ifm electronic sensors, networking and control … networking and control technology for automation...
TRANSCRIPT
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ifm electronic
Sensors, networking and control technologyfor automation
Training manualR
temperature sensors
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temperature sensors
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Training manual
You will find further information, data sheets, prices etc. at: www.ifm-electronic.com
Training manual temperature sensors (as in March 2003)
Note on guarantee
Utmost care was taken when writing this manual. Nevertheless, we cannot guarantee that the contents are correct.
Since it is impossible to avoid mistakes despite intensive efforts, we always appreciate indications.
We reserve the right to make technical alterations to the products so that deviations from the contents of theTraining manual may result.
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Contents
1 INTRODUCTION 5
1.1 Temperature sensors used in industry 5
1.2 Notation 10
1.3 On the contents 10
2 TEMPERATURE 12
2.1 Definition 12
2.2 Units 14
2.3 Values 16
2.4 Material characteristics 18
3 TEMPERATURE MEASUREMENT TECHNOLOGY 27
3.1 Overview 27
3.2 Principles of temperature measurement 28
3.3 Terms 29
3.4 Comparison of the measuring systems 323.4.1 PTC 333.4.2 Thermistor 353.4.3 IC sensor 353.4.4 Thermoelement 363.4.5 Other types 36
4 THE IFM TEMPERATURE SENSOR FAMILY 37
4.1 History 37
4.2 Technical details 384.2.1 Sensor element 384.2.2 Signal processing 40
4.3 Basic unit 414.3.1 Display 414.3.2 Switch point 434.3.3 Hysteresis 444.3.4 Window 46
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4.3.5 Analog output 474.3.6 Other settings 494.3.7 Enhanced functions 524.3.8 Overview 53
4.4 Overview of the units 554.4.1 Summary 554.4.2 Mechanical characteristics 624.4.3 Electrical characteristics 70
4.5 Summary 714.5.1 Conventional temperature sensors 714.5.2 Control monitor 724.5.3 Sensor in the modular system 72
5 APPLICATIONS 73
5.1 Application example 73
5.2 Further examples 745.2.1 CIP Cleaning-In Place 745.2.2 Yeast pre-enrichment system for breweries 765.2.3 Washing systems 775.2.4 Pasteurisation systems (short-time heating systems) 785.2.5 Tank and vessel monitoring 795.2.6 Temperature sensors for machine tools (automotive industry) 80
TECHNICAL GLOSSARY 82
EXPLANATION PRODUCTION CODE 92
TYPE KEY 93
INDEX 95
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1 Introduction
1.1 Temperature sensors used in industry
Where? In many different market segments of different importance a wide rangeof applications for temperature sensors exists.
Some typical examples will give an idea of the variety of applications.
With what? These examples also show the modular design of a sensor family. Theexact description of the family is given in chapter 4. The designations TTand TS are also explained in this chapter.
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Temperature monitoring of:
Tanks and containers A thermowell is welded into the tank or for the MO or DIN version it isscrewed into it depending on requirements and place of temperaturemonitoring. Via the progressive ring fitting the sensor can be pushed intothis thermowell until the end stop has been reached and can then befixed by the progressive ring fitting. An optimum heat transfer of thethermowell with the pushed-in TT temperature sensor with protectivetube must be guaranteed by a thermolubricant. Typical applications arefor example:• the fermentation process in breweries where the exact adherence to
limit process values are decisive for the quality of the product• in storage tanks where cooling systems are controlled via the switch
points to ensure a constant temperature of liquids of all kinds, e.g.beverages, chemicals etc. (figure 1)
figure 1: Temperature monitoring in tanks and containers
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Machine tools
The tank for the coolant or lubricant must not exceed a certaintemperature. If this is however the case, the liquid is exchanged with thatof a central tank for all machines to reduce the temperature. The TTtemperature sensor with protective tube can be clamped into the tankwithout additional thermowell via a progressive ring fitting. Its signal istransferred to the control monitor which indicates the temperature onsite and at the same time passes the current temperature data on to thecentral plc via its analog output.The TS cable sensor is screwed into the return pipe of the spindle drive. Inthis application example (figure 2) it ensures the safe detection ofoverheating of this drive. Moreover the temperature of the coolant orlubricant is monitored to avoid overheating of the tool or the workpiece.
figure 2: Temperature monitoring in machine tools
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Heat exchanger One of the most frequent applications is the monitoring and controlling of"temperature transfer processes". These processes can be found in heatexchangers, such as refrigerating sets and heaters, as well as in all processsteps, e.g. in the chemical industry, where certain processes are controlled byheat supply or discharge.
In this example (figure 3) the wort coming out of the mash pan is cooledbefore it enters the fermentation and storage tanks where yeast is addedand the beer ripens. It enters the heat exchanger with the temperatureT1 and leaves it with T2. The coolant is heated from T3 to T4. Ifnecessary, the temperature of the coolant must be monitored separately(not shown here).
figure 3: Temperature monitoring of a heat exchanger
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Many more examples could be given. For the different applications avariety of sensors or measuring instruments with different functions areavailable. Below (see 3) an overview of all common sensors types andtypical applications will be given.
The variety of applications shows the huge market potential fortemperature sensors. Studies show that temperature sensors are one ofthe most important sensor groups. It is not possible to describe allapplications here. Further examples are given in chapter 5. The mostimportant aspects are described here.
Requirements The market study before the development of the temperature sensors hasshown that the requirements in the individual industries differconsiderably. This concerns for example:
− temperature range− length of the temperature probe− connection of the sensor to the control monitor and its features with
regard to switching functions and the universal use of controlmonitors
Tasks There are two main tasks for temperature sensors
• monitoring tasks and• process control
There are various monitoring tasks. The second task concerns theimportant area of process engineering.
Solution: modular As a consequence different precision and response times are required. Itis not easy to meet all requirements. The Pt 1000 element and the otherperipheral equipment is an optimum solution.
The objective of the development was to cover as many applications aspossible with the smallest possible number of components. It hasbecome clear that a modular design is the ideal system. It is described indetails in chapter 4.
Advantages Another aspect should also be mentioned.
An electronic temperature sensor is in competition with well-known,simple and inexpensive units. It is however not necessary to find newarguments for its use because they are similar to the arguments for theother electronic sensors. Two specific examples:
Thermometer A mercury or alcohol thermometer ensures a reliable indication of thetemperature on a scale. Sometimes it is however difficult to read thetemperature. The main problem of these units is that it is verycomplicated to get a reliable analog or binary output signal.
Bimetal A bimetal contact is a simple and inexpensive "temperature sensor". Itprovides a binary signal. In many cases a temperature sensor not only hasto enable the setting of a switch point but also the indication of thecurrent temperature. In these cases a measuring instrument and nobinary sensor is required. In addition to the other problems of the
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bimetal, it is hardly possible to change the switch point and to indicate ameasured value or to provide it as an output signal. Temperatureindication is the best possible task.
1.2 Notation
For a better understanding some notations should be explained whichmake it easier for you to read the text and find information.
Headwords Headwords are written in the left margin. They refer to the topic in thefollowing paragraph.
What does FAQ mean? This means Frequently Asked Questions. This is a term which is forexample also used for modern electronic media. Almost anybody goinginto a new field faces the same questions. Sometimes they are given atthe beginning of a paragraph instead of a headword. They are printed initalics to distinguish between FAQ and simple headwords.
( 4) A number in round brackets in the left margin indicates an equationwhich is mentioned later, e.g. see (4). You do not have to learn theseequations by heart. They shall help you to understand the contentsbecause, like a figure, an equation gives a shorter and more precisedescription of a correlation than many words.
1.3 On the contents
This document is to explain the basic principles of temperaturemeasurement technology. Important terms and correlations will beexplained, state of the art technology and technical data of atemperature sensor will be presented. The text will be structured asfollows:
1. Temperature Some basic terms, units and their correlation which are needed tounderstand the applications of temperature measurement technology willbe described.
2. Temperature measurement technology A short overview of the variety of systems which are used in practice willbe given. Among others it is intended to facilitate the correct placementof the ifm sensor and to decide where it can be used and where not. Theknowledge of these systems, their advantages and disadvantages and theterms is a prerequisite for a good discussion with the user.
3. A family of temperature sensors The data of the sensors will be listed and explained in this chapter.Mechanical design, electrical features, application and switch pointsetting will be described here.
4. Applications A short overview of possible applications will be given.
5. Short glossary This documentation is also made for private studies. Terms which are notencountered so often will be explained briefly in the glossary. The termswhich are important for the example of a sensor are described in more
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details in the chapters preceding this glossary. The index will help you tofind the terms.
Much success! With this basis everyone should be able to work with temperaturesensors successfully.
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2 Temperature
We are familiar with temperature or temperature measurement in oureveryday life. It is good to be familiar with the basic principles becausethis helps to understand technology and applications.
2.1 Definition
What is this? As is often the case with familiar things, it is difficult to say what it is. Theanswer to this question seems to be a little bit abstract: temperature is ameasure of molecular movement. Without knowing the structure ofmatter it is difficult to understand temperature.
Structure of matter This is a short reminder that matter consists of atoms or molecules. Forinert gases (e.g. helium or neon) it consists of individual atoms. For othergases, e.g. oxygen or water vapour, the atoms have formed molecules.Since individual atoms are an exception, we will only speak of moleculesbelow. Usually these molecules keep moving.In gases they can move freely. Individual molecules can reachconsiderable speed in the range of km/s.Liquids are similar to gases. But liquids have an interface through whichthe fastest molecules can escape (evaporate, vaporise).The molecules in crystalline solids have a lattice structure. Normally theydo not leave their place in the lattice, but they can swing to and fro (seechapter 2.4, figure 12).
Energy They all have a certain kinetic energy. If more energy is supplied, which iscalled heating, the movements become faster. The temperature increases.This can be defined as follows:
__W = CT
( 1)
W [J]: energy, workC [J/K]: material-dependent coefficientT [K]: temperature
J is the abbreviation for Joule. The correlation with the basic values m, kg,s, A is not important in this context. The unit K for the temperature isexplained in 2.2.
Since they do not all move the same way, some are faster, some slower,the average of the energy W is calculated. This is indicated by thehorizontal line. In this context the energy is called heat (W stands forwork). C is a constant which is not explained further and T is thetemperature.
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Intensive and extensive Like e.g. pressure, temperature is called a state quantity. The differencebetween heat and temperature can be explained with an example. Toheat 1 l of water by a defined amount ∆ T, a defined energy is needed.For 2 l of water you need twice as much. If you pour together 2 l ofwater of the same temperature, the energy is twice as high as for 1 l. Butthe temperature is not twice as high, it remains the same (figure 4). It iscalled an intensive value, the heat is an extensive value.
figure 4: Heat and temperature
Short summary Heat is a form of energy. The molecules keep moving. The average oftheir kinetic energy is called heat. The temperature is the intensity of theheat.
Different material characteristics depend on the temperature, e.g.• volume (density) or• electrical conductivityThis can be used for temperature measurement.
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2.2 Units
° C In former times the definition of the unit referred to the changes in thestate of aggregation caused by temperature. If you heat ice, it melts, thismeans that water passes from the solid to the liquid state. If you mix icewith water, there will be a temperature equilibrium after some time. Thevalue of this temperature was defined as 0°C (in words "zero degreeCelsius"). Celsius was a Swedish physicist and astronomer who suggestedthis definition. The value for the transition from liquids to gases, theboiling point, was defined as 100°C. It must however be considered thatthe boiling point depends on the pressure. It is known that the water onhigh mountains (and lower pressure) boils at lower temperatures. This iswhy it is difficult to boil eggs or tea there. For higher pressures, e.g in apressurised cooking pot, the boiling point is higher. 100°C is thus definedfor normal pressure, approx. 1 bar.
K If you test the volume of gas at different temperatures and enter thevalues in a graph, you will find out that all the values are on a straightline. If you prolong this straight line until the point of intersection withthe axis is reached, the theoretical temperature value at which thevolume becomes 0 is determined. This value is the same for all gases andis -273°C, see figure 5. It is called absolute zero. Lower temperatures arenot possible.
figure 5: Absolute zero of the temperature
This value was defined as 0 K (in words "zero Kelvin", not "zero degreeKelvin") and is independent of a material characteristic (melting point ofwater). Kelvin was an English physicist who concentrated on heatresearch. For this unit no sign must be considered, only positive valuesexist. The Kelvin scale has the same gradation as the Celsius scale. As aconsequence it is very easy to convert the units. The Kelvin scale is adisplaced Celsius scale. The following applies:
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0 K = -273°C and
0°C = 273 K
Precision The value -273°C is indicated without decimal places. A precisetemperature measurement is complicated and difficult, this precision isnormally sufficient. In this case we do not have to consider the differencein the definition of °C and K, which is approx. 1/100° and has noimportance in practice.
Difference For temperature differences it is not important which unit is used. If forexample water is heated from 20°C to 30°C, you can also say that it isheated from 293 K to 303 K. In both cases the difference is 10. TheInternational System of Units (SI, abbreviation for French systèmeinternational) stipulates that temperature differences always have to beindicated in K.
° F It is no new idea to start the temperature scale at the lowest value toavoid negative values. The physicist Fahrenheit from Königsbergintroduced such a scale. During the coldest winter in living memory inKönigsberg, he tried to reproduce the lowest temperature with a water-salt mixture. He defined this temperature as the zero of his scale. Hedivided his scale into 180 steps between the melting and the boilingpoints of water. On the Fahrenheit scale the melting point is thus at 32°F.The conversion is more complicated:
( 2) T[° F] = 9/5 T[° C] + 32
As a consequence 0° C = 32° F and100° C = 212° F
This a little bit antiquated unit of measurement is still used in the UK andthe United States.
The following diagram shows the correlation and helps to convert thevalues.
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!
figure 6:Conversion °C - °F
° R Nowadays the Réaumur scale is seldom used, this is why it is only brieflymentioned. It is similar to the Celsius scale. The only difference is thatthere are 80 steps instead of 100 steps between the melting and boilingpoints of the water. The melting point is thus 0° R and the boiling point80° R.
2.3 Values
Is 1°C much? First of all this question - a similar one to that in the pressure manual - isto be discussed briefly. Here it is easier to answer because we are familiarwith this value: 1°C is a relatively low value. It is near the limit value ournatural temperature sensors in the skin can distinguish. Our feelingenables a more reliable reaction on temperature differences. It is thusvery easy to find out whether a medium has a higher temperature thananother. The body temperature, usually approx. 37°C, is a yardstick.Between 0°C and 60°C our body sensors function in a relatively reliableway.
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The following table gives an overview of the typical temperature values. Itcan only give an idea of the magnitude. These values are no exact valuesbut typical values. All values are indicated in °C.
T [°C] Phenomenon6000 electrical arc under pressure
surface of the sun4000 electrical melting furnace3000 filaments in bulbs2000 ignition in the car engine1800 Bunsen burner1600 gas oven1400 coal fire (anthracite)1370 liquid glass1200 iron melts1000 iron glows
800 diamonds burnwood fire
600 illuminating gas ignites400 vapour in locomotives200 engine block in the car
0 melting point of water-2.5 melting point of sea water-65 lower stratosphere
-200 air becomes liquid-253 hydrogen boils
The absolute zero cannot be reached in practice. It was however possibleto approach it down to some fractions of Kelvin. This is however only oftheoretical interest because this is only possible for a short time and fornot much matter.
Except for the extreme temperatures in glass or steel melting processes orin applications with liquid hydrogen many industrial processes take placein a range from 0 to 100°C. It is of course not by hazard that these valuesare the reference points of the Celsius scale. If the range is extendedupwards and downwards, e.g. from -50 to +150°C, an even largervariety of processes is covered.
Food industry One example is the food industry with processes such as cryotransfer,refrigerating, simple cooling, fermenting, short-term heating, cooking,cooking under pressure, vapour cleaning etc. These processes must bemonitored to avoid inadmissible temperature variation or to sort outinedible results. Since many sensors are required for this, the potential oftemperature sensors in this industry is enormous. This also shows inwhich temperature ranges the sensors are used.
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2.4 Material characteristics
As already mentioned in chapter 2.1, characteristics such as volume,electrical resistance etc. change when the temperature changes. In thischapter we will explain the background and some important terms. Thetechnical application is described in chapter 3.
To increase for example the temperature of a medium, energy must besupplied (see equation ( 1)).
Thermal capacity Different materials have a different increase in temperature when thesame energy is supplied. The value describing this characteristic is calledthermal capacity or specific heat. This material characteristic is sometimesmixed up with the next term.
Thermal conductivity If the energy is for example supplied because a colder object is in contactwith a warmer object, another material characteristic can be observed.Different materials have a different temperature adjustment speed. Thischaracteristic is called thermal conductivity. As regards the heat insulationof buildings for example a low thermal conductivity is advantageous. Asdescribed below a good thermal conductivity is however important forthe sensor.
Warm and cold The thermal conductivity plays an important role for our subjectivefeeling whether a material feels warm or cold. Wood for example feelswarm even at low temperatures because the surface quickly adapts to thetemperature of the hand. We no longer feel the lower temperature insidethe piece of wood. Cold metal feels cold because of the good thermalconductivity. Heat is withdrawn from the hand. We always feel thetemperature of the whole metal object. Like our natural temperaturesensors measuring instruments can also be mislead.
What does that mean? These material characteristics are important for the characteristics andthe operation of temperature sensors. The sensor can only detect thetemperature of the medium if its own temperature has adapted to thetemperature of the medium.
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figure 7: sensor in the medium
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The place of measurement is also important. The temperature of themedium is not the same everywhere. There can for example be differenttemperatures at the edge or inside the tank.
Since the measurement must be taken in the middle of the medium, thesensor is surrounded by a housing so that it is not mechanically damagedor attacked by chemicals. This has effect on the measurement.
Temperature equilibrium When the sensor is immersed in the medium or when the temperature ofthe medium changes, the sensor element has another temperature thanthe medium (figure 7 and the following figures).
The following figures show different situations. They are based on figure7. The grey area is the medium, the hatched area is the housing and thewhite area is the sensor itself.
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figure 8: temperature difference
This temperature difference (figure 8) will be balanced after some time(the ideal case is shown in figure 9). How long this will take is describedin figure 19.
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figure 9: Temperature equilibrium
Characteristics of sensor 1 It is disadvantageous if the sensor or the material of the housing has apoor thermal conductivity. If it takes a long time until the temperature ofthe sensor has adapted to the medium the sensor has a slow response.This characteristic is known for the flow sensor (with the calorimetricprinciple). If the material PTFE is used because of the high chemicalresistance, the sensor has a considerably slower response than a metalsensor.
Medium air Air is a poor conductor of heat. For this reason double or triple glazedwindows improve the thermal insulation of buildings, even if the spacebetween the window panes simply contains air. An air layer between thesensor element and the housing or between the sensor and theprotective tube (see 4.4.2) is however disadvantageous because thesensor then only has a slow response.
Thermolubricant Such air layers are avoided by applying a thermolubricant, a plasticmaterial with good thermal conductivity e.g. between the protective tubeand the sensor. A temperature equilibrium between the medium and thesensor is thus reached fast enough.
Characteristics of sensor 2 A high thermal capacity is also disadvantageous.
Cooling In this case the sensor must withdraw a lot of energy from a warmermedium until its temperature has adapted to the medium temperature.This means that the temperature of the medium decreases, the sensoritself falsifies the measurement (figure 10).
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figure 10: Deviation by cooling
Heating The reverse is also possible. If the temperature of the medium decreases,the sensor still has the higher temperature. If the medium cannot absorbmuch heat, the temperature of the sensor remains the same for a muchlonger time. The self-heating of the sensor element must also beconsidered. A Pt-T for example (see chapter 3.3) is a current-carryingresistor.
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figure 11: Deviation by heating
Non-flowing media The two causes for measuring errors described above have particularlystrong effect when the medium is not flowing. In this case the heattransfer is poor. The situation can possibly be improved by calibration(see chapter 4.3.6). In particular non-flowing media with low density,such as air, may lead to problems.
Characteristics of sensor 3 The above-described characteristics concern the temperature equilibriumbetween sensor element and medium. The sensor must not have toostrong influence on the medium or the process. If for example thetemperature of a hot medium is to be detected, the sensor housing mustnot transfer excess heat to the environment. On the other hand excessenvironmental heat must not be transferred to a cold medium via thesensor housing. The modular design is best suited for these requirements.
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Electrical conductivity The thermal conductivity correlates with the electrical conductivity. Atfirst sight this may be surprising but it is easy to understand if you have alook at the structure of matter. In chapter 2.1 it has already beenmentioned that temperature can be described as the average kineticenergy of the molecules. In a solid the molecules cannot move freely,they can only swing. If energy is supplied, it is obvious that it takes arelatively long time until the energy is spread evenly because a moleculeat its fixed place can only influence its nearest neighbours.
figure 12: Lattice structure
figure 12 shows a cubic lattice as an example (a small cube is marked inthe figure). It only shows the structure and not the movement. Let ustake an individual atom to get a better impression of the movement.
figure 13: Atom in the lattice
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figure 13 shows that the atom can swing in different directions.
figure 14:Swinging
figure 14 shows that you can imagine that an atom is fixed with elasticsprings between which the atom can swing. For simplification only onedirection was represented. It should be clearer now what temperaturereally is (see chapter 2.1), a measure for the average energy with whichall atoms swing. Unless too much energy is supplied so that the lattice isdestroyed (melting), each atom remains at its place and energy is spreadonly slowly. Only for good electrical conductors this can be faster. Whatis the reason for this?
A material is electrically conductive because the charge carrier can movefreely. In the case of metals the electrons are the charge carriers. They arefaster in absorbing and spreading the supplied energy. This is why metalsare good thermal conductors.
PTC This explains why in many cases the electrical resistance increases whenthe temperature increases (PTC, see chapter 3.3). At low temperaturesthe molecules swing (for metals: the atoms) only a little bit. The electronshave a lot of free space to move without restrictions - the resistance islow. At higher temperatures the swinging is more intensive. The electronsoften collide, it is more "difficult" for them to move - the resistanceincreases.
NTC It is clear that this simple model has its limits because there are materialswith the opposite characteristics (NTC, see chapter 3.3). It should also beconsidered that the number of freely moving charge carriers alsodepends on the temperature. This also has influence on the conductivity.The more charge carriers are "released", the higher the conductivity is.These complex correlations will however not be considered here.
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A PTC is used for the example of a temperature sensor in 4. This PTC is aPt-T. These terms are explained in chapter 3.3.
Thermoelements These fundamental principles also make it easy to understand thefunctioning of thermoelements. Different metals have a differentelectrical conductivity κ. The reason for this is that the electrons in onemetal can move better, "more freely", than in other metals and that thenumber of electrons which can move freely is different.
Seebeck effect What happens if two objects of different metals get in contact with eachother? Electrical contact means that charges can flow from one metal tothe other, i.e. electrons can pass the boundary between the twomaterials. If both metals had the same characteristics, the same numberof electrons would be exchanged between them. If the mobility and thenumber of electrons are however different, there will be an unbalance.
& & &
figure 15: Metals in contact
This effect is named Seebeck effect after its researcher. But even thencurrent cannot flow continuously because the charge difference wouldincrease constantly and result in increasing voltage. Indeed anotherequilibrium is established when the voltage becomes so high thatelectrons can no longer move to the other side.
Temperature difference This is the reason why two points of contact are required for athermoelement. Only if these two points have different temperatures,have they a different "permeability" which also depends on thetemperature.
Now the thermovoltage or the thermocurrent can be measured from theoutside.
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figure 16: thermoelement
figure 16 shows that two materials with different electrical conductivityκ1 and κ2 are required. Their points of contact must have differenttemperatures (T1 and T2). figure 15 shows a high magnification of asensor tip (left for T1).
It is obvious that only a temperature difference can be measured with athermoelement. To measure an absolute temperature, a medium with afixed reference temperature is needed. This is similar to a differentialpressure measurement. But it is even more difficult to keep a temperatureconstant than the pressure.
Error of measurement For this measurement principle it should be considered that there areother points of contact in the complete system, e.g. between the cablesto the measuring instrument and the thermoelement. If these points havedifferent temperatures, an additional thermovoltage results which canfalsify the result. This error of measurement does not only occur forthermoelements but also for those temperature measurements which arebased on the measurement of electrical values, such as PTC's for example(see chapter 3.3).
Energy In the case of a thermoelement the current could for example be used todrive an engine. Even if the power is very low, energy would be requirednevertheless. Where can it come from? The only possibility is thetemperature difference. With this effect a temperature equilibrium isestablished between the different temperatures (even without thermalconduction). If there is no temperature difference any longer, no currentcan flow, no work can be done.
Heat engine Each heat engine, e.g steam machine or Stirling engine, is based on thisprinciple. It is obvious that a medium with a higher temperature isrequired as an energy supplier. But it took a long time before it becameclear that another medium with a different temperature is alsoimportant. Only then became the construction of a functioning steamengine by James Watt possible. This was not even 250 years ago.
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Peltier effect This effect can also be reversed. If energy is supplied from outside theprocess, if for example a voltage source is connected, the temperaturedifference increases. One point of contact is heated, the other coolsdown. This is called the Peltier effect. Such a thermoelement is a Peltierelement. This effect is for example used for refrigerators which areoperated by battery. The low efficiency is disadvantageous for thispractical application.
Summary The most important basics are summarised here:
• temperature transferThe sensor must be able to adapt to the temperature of themedium quickly. A thermolubricant can support this.
• electrical resistanceThis value is often used for temperature measurement. Thesensor described in 4 also evaluates the change in the electricalresistance in the case of temperature changes.
• thermoelementsThey are used for temperature measurements but it is difficult touse them in practice.
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3 Temperature measurement technology
3.1 Overview
The variety of units for temperature measurement is as large or evenlarger than the variety of units for pressure measurement (see chapter3.2). Some units or measuring principles will be briefly presented in thischapter to get to know the important terms and to enable a betterassessment of sensors. The following table shows some examples andtheir temperature ranges.
Measuring range of temperature measurement procedures
Liquid-in-glass thermometer with mercury -30° C to 280°Liquid-in-glass thermometer with mercury and gas -30° C to 750° CLiquid-in-glass thermometer with alcohol -110° C to 50° CThermocolours 150° C to 600° CSeger cone 220° C to 2000° CMetal expansion thermometer -20° C to 500° CElectrical resistance thermometer -250° C to 1000° CHeat colours 500° C to 3000° CGas thermometer -272° C to 2800° C
figure 17: temperature measurement procedures
Below please find a brief explanation of some terms which are notcovered in this chapter.
Thermocolours Thermocolours are substances which change their colour when a limittemperature is exceeded. They can only be used once. They are used forindicating high temperatures. LCD thermometers are based on a similarprinciple. The colour change should however be reversible. They are onlyseldom used because of their considerable aging.
Seger cone They are also used for monitoring high temperatures during the burningof ceramics. At a certain limit temperature they start to melt, i.e. they fallor get bent. This shows if the burning process is correct and if the settemperature ranges are adhered to. They are available for different limittemperatures.
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3.2 Principles of temperature measurement
Depending on the principle used, the temperature measurementmethods can be divided into several categories. For pressuremeasurement most measuring instruments are based on a mechanicaldeformation. There are more methods of measuring temperatures but inmost cases the medium must be in direct contact with the measuringinstrument.
Expansion All materials change their volume when the temperature changes, somemore, some less (thermal expansion). This becomes clearer when adistinction between the different states of aggregation is made.
• Gases
Gas thermometers are a little bit complicated because the pressurealways has to be considered. They are used for high temperatures.
• Liquids
At present the liquid-in-glass thermometer is the type most frequentlyused. They exist in almost every household, more often than barometers.For most bath thermometers alcohol is used, for many medicalthermometers mercury is used. It should be handled with care becausemercury is toxic.
• Solids
For this type the different heat expansion of different metals is used. Iffor example two strips of different metals are soldered to become onestrip, this strip is bent when the temperature changes because one sideexpands more than the other. This is a bimetal thermometer.
Electrical conductivity It changes when the temperature changes. You can also say that theresistance changes when the temperature changes. So it is very easy togenerate an electrical signal. This effect is used for most electronicthermometers and also for the example of temperature sensors.Important basic terms are explained in chapter 3.3. In chapter 3.4possible technical solutions are discussed.
Thermoelectric voltage The voltage arising for thermoelements is also used to measure thetemperature (see chapters 2.4 and 3.4).
Radiation Hot objects emit infrared rays or in the case of high temperatures evenvisible light (glowing). For binary sensors such as the ifm OW family, thecorrelation between switch point and temperature is not clear becausethe received radiation depends on the material constant degree ofemission. That is why ifm has included these sensors with the positionsensors, see Training manual Photoelectric sensors. There are morecomplicated and more expensive measuring instruments which determinethe temperature on the basis of the radiation (see heat colours in thetable above).
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3.3 Terms
Most pressure measuring instruments evaluate a mechanicaldeformation. The documentation shows how many different solutionsexist. As described above, temperature measurements can be based onmore phenomena. Not all possibilities will be discussed in details here.Only some important terms for temperature sensors will be described.This concerns especially units which evaluate a change in resistance. Onlythe term transient function is also used for most of the other units.Further terms can be found in the short glossary.
In this chapter the terms are not arranged in alphabetical order butaccording to correlations.
Characteristic curve If you measure the electrical resistance at different temperatures andenter these values in a graph, the resulting characteristic curve (see figure18) enables to determine the temperature on the basis of the resistancemeasurement.
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'
(
figure 18: Characteristic curve (Pt100)
figure 18 shows the characteristic curve of a Pt-T (see below). It can beseen that in this case the characteristic curve is almost linear so that it isnot so difficult to linearise the characteristic curve. For many othermaterials the curve is not so linear.
Temperature coefficient, PTC NTC If this characteristic curve (see figure 18) or part of it is replaced by anapproximative straight line, the gradient of the straight line is thetemperature coefficient. There are materials where the resistancedecreases when the temperature rises. For these materials the coefficientis negative (NTC: negative temperature coefficient). The materials with apositive coefficient are however more important for this application. Theabbreviation for this is PTC (positive temperature coefficient).
Pt-T, Pt 1000, Pt 500, Pt 100 These designations must not be confused with PTC. For different reasons,e.g. the high chemical resistance, platinum is used for such temperature-dependent resistors. Pt is the chemical abbreviation for platinum. The so-called nominal value, this is the resistance of a standard conductor at0°C, is exactly 1000.00 Ω for PT1000. Pt500 and Pt100 with therespective nominal values are also available. The characteristic curve of aPt100 is given in figure 18. The characteristic curves of a Pt500 and aPt1000 are similar. They are only 5 times or 10 times steeper and meetthe resistance axis at 500 Ω or 1000 Ω. Many temperature sensors have aPt XY as a sensor element (XY stands for 100, 500 or 1000). A Pt XY isalso a PTC. PTC's made of less expensive material are also offered but
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their characteristics are not so good. Below the abbreviation Pt-T will beused for platinum temperature sensor element.
Nominal value A high nominal value (see Pt1000) increases the possible resolutionbecause the change in resistance is also big. Up to 100°C the coefficientfor PtXY types is as follows:
Pt100 0.4 Ω/KPt500 2.0 Ω/KPt1000 4.0 Ω/K
It is of course easier to measure 4 Ω than 0.4 Ω.
How precise is the nominal value? As explained for Pt1000 the nominal value is an approximative value.Strictly speaking the resistance change, e.g. for Pt1000 and atemperature range from 0 to 100°C, is between 3.8 and 3.9 Ω/K. Thesame applies to Pt500 and Pt100. In IEC 751 these values are called basicvalues. Since the characteristic curve is almost linear, the above-mentioned nominal values are a good approximation.
Tolerance classes PT-T's are divided into tolerance classes. Of course it is almost impossibleto manufacture two or several Pt-T's with completely identicalcharacteristics. They are subject to individual variations. The maximumpermissible values are stipulated in the definition of the tolerance classesin IEC 751.
Tolerance class Temperature range ToleranceA -200° C to 600° C ± (0.15 K + 0.0020 * t)B -200° C to 850° C ± (0.30 K + 0.0050 * t)
1/3 B -70° C to 250°C ± (0.10 K + 0.0017 * t)
In IEC 751 only the classes A and B are stipulated. The class 1/3 B is aspecification following IEC 751. Since the classes A and B cannotguarantee a satisfactory coverage of the large variety of applications, 1/3B (and others) are also used. Even in the temperature sensors of 4 Pt-T'sof class B are used. The types specially designed for applications inhygienic areas, e.g. TT0061, TT1061 use Pt-Ts class A.
t in the table is the temperature value in °C (without sign). The tableshows for example:
at 0°C the tolerance is ± 0.30 Kat 100°C the tolerance is ± 0.80 K
These values apply to class B.
Thermistor For special semi-conductors the nominal value is very high so that a goodresolution of the measurement is possible. The characteristic curvehowever is not at all linear which makes the evaluation more difficult.Such resistors are called thermistor.
Transient function This function describes the time behaviour of a temperature sensor. Firstof all the sensor (and the surrounding medium) have the temperature T1.Then the medium temperature immediately changes to T2 (the exact testset-up is described in IEC 56B). The sensor's own temperature increasesslowly (see chapter 2.4). The curve of the measuring signal is the
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transient function. Two values are selected to characterise the function:t0.5 and t0.9. This is the time after which the measuring signal hasreached 50 %, the so-called half-time, or 90% of its final value. Thisfunction is given in figure 19. It should be considered that this is not themedium temperature but the temperature of the sensor or the valuedisplayed by the control monitor (please also see figure 7 and thefollowing figures).
)
)
) ) *
figure 19: transient function
3.4 Comparison of the measuring systems
After the explanation of some terms and the description of themeasuring principles current systems or types are to be compared now.The order of the mentioned points is no evaluation. The importance of acharacteristic may differ for every individual case.
Advantages and disadvantages are presented in the tables. These tablescan be explained as follows:
If a term, e.g. output voltage, is mentioned in the column +, this meansthat it is relatively high and thus easy to measure. If it is mentioned in thecolumn -, it is relatively low. The measurement is thus more difficult andmore susceptible to errors.
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3.4.1 PTC
This term has already been explained in chapter 3.3 (see "temperaturecoefficient"). This chapter concerns practical applications.
To determine the resistance, a voltage is for example applied. If voltageand current are measured, the resistance can be calculated by Ohm's law.
( 3) U = R * I
U [V]: voltageR [Ω]: resistanceI [A]: current
The current I also leads to a self-heating of the PTC, which causes ameasuring error. To keep it small, the current must be as low as possible.If the current is for example 1 mA, the voltage drop caused by a Pt100 isexactly 0.1 V.
This voltage must be measured at the PTC. There are three types ofcircuitry.
2-wire circuitry The PTC is connected to the power supply by means of a 2-wire cable. Inthis case the measurement can only be carried out there. In that way thetotal resistance determined is the sum of the resistance of the PTC andthat of the cables. It is extremely difficult to compensate for the cableresistance because it also depends on the temperature. The temperatureof the cables is neither constant in time nor in space. The longer thecables, the higher the resulting measuring error. For this circuitry a high-ohmic PTC is favourable.
A 2-wire circuitry is used for the temperature sensor described in 4. Tocompensate for possible measuring errors, they can be calibrated (seechapter 4.3.6). Should it become obvious that this is not sufficient formany applications, it would be technically feasible to manufacture unitswith 4-wire circuitry (see below).
3-wire circuitry This circuitry has an additional wire to a contact of the PTC, thus a totalof 3 wires. Two measuring circuits can be evaluated, which enables abetter compensation of the influence of the cables.
4-wire circuitry Two measuring wires to the PTC contacts in addition to the two supplywires guarantee a very reliable measurement. If the ohmic value of theinput of the evaluation circuitry is high enough, the influence of themeasuring wires can be ignored. This circuitry is of course the mostcomplex one.
In practical applications there can be mixtures. The head of the sensorwhich is the process connection can for example be connected to themeasuring system outside the medium. The two measuring cables thengo to this connection point whereas two wires are connected to the PTC.The measuring error thus depends on the distance between themeasuring wires and the PTC.
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Summary The characteristics of the metallic PTC are summarised here:
+ -• stability • price• precision • response time• linearity • power supply necessary
thus self-heating
Pt As already mentioned Pt XY (XY = 100, 500 or 1000) are often used forPTC's. If the requirements are not so high, other metals such as nickel orcopper alloys are also used.
Applications We can only give some examples of the variety of applications.
• heating, air conditioning• overload protection for engines• semi-conductor protection• process temperature regulation
Non-metallic Non-metallic materials (PTC thermistors), such as polycrystalline bariumtitanate, are also used according to the same principle. This material isnot so precise and has a high degree of individual variations. Anothercharacteristic makes it interesting for practical use. It only behavesaccording to Ohm's law ( 3) up to a certain limit. If the voltage is higherthan this limit, the resistance increases rapidly. The current is thus limited.
+
,
+
+'
figure 20: NTC thermistor
The maximum current intensity is called breakover current IK and thealmost constant current at higher voltage is called residual current IR(figure 20).
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Applications For consumer goods where high quantities are needed and precision isnot so important these types are often used.
• temperature limit switch (motor windings, hot-water apparatus)• overload protection (loudspeaker, low-frequency technology, small
engines)• delay circuits• self-regulating thermostats (hairdryer)
3.4.2 Thermistor
The term is described in chapter 3.3. The low heat capacity on the onehand as described above is advantageous. On the other hand this makesthis type susceptible to measuring errors because of self-heating.
+ -• output voltage• temperature coefficient• response time
• no linearity• temperature range• mechanical stability• power supply necessary
thus self-heating
3.4.3 IC sensor
There are types where the sensor element and the evaluation circuit forman IC. The first temperature sensor of 4 was one of these types. It hashowever been replaced by Pt1000 sensors.
+ -• output voltage• price• linearity
• only temperatures < 250°C• response time• selection• power supply necessary
thus self-heating
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3.4.4 Thermoelement
This term is also explained in chapter 3.3.
+ -• no power supply necessary• robustness• price• many types• temperature range
• no linearity• output voltage• reference required• stability• temperature coefficient• contact points
Contact points means the following: In the complete set-up there are notonly the contacts in the sensor element but also contacts with the cables.If these points have different temperatures, a measuring error will result.
3.4.5 Other types
We would like to mention some other types which are also often used.The basic principles will however not be explained.
NTC In chapter 3.4.1 the term PTC resistors has been mentioned. NTC's arecalled thermal resistors. They consist of ceramic oxides. They can be usedin many applications, are inexpensive and have a high temperaturecoefficient. On the other hand the response time is relatively long.
Applications It can be used for many applications. Some examples:
• food and plastic industry• car electronics• medical technology• temperature compensation of coils, transistors• overload protection
Semi-conductor sensors The electrical characteristics of semi-conductors also depend on thetemperature. These types have a temperature range between -50°C and+150°C.
Silicon N-type silicon is used here.
Diode, transistor It is based on the effect that the resistance of the pn junction stronglydepends on the temperature. These junctions are generated by thedoping of suitable materials. Since this process is difficult to reproduce,there is a high degree of individual variations.
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4 The ifm temperature sensor family
4.1 History
In the beginning this family of the temperature sensors consisted of onlyone type which will be described briefly. This sensor is an IC sensor (seechapter 3.4.3). In the continuous process of optimisation this type has inthe meantime been replaced and complemented by other types (see4.2.1).
Measuring method The analog resistance value must be digitised for electronic evaluation.This is reached by a frequency measurement, this means by measuringthe number of oscillations in a defined period. The temperature-dependent resistor is part of an oscillating circuit. If the temperaturechanges, the resistance and thus the frequency changes, i.e. the numberof oscillations per time changes. For different reasons a relativemeasurement is often better than an absolute measurement, e.g. for abetter compensation of measuring errors. This method has also beenapplied to this sensor. Strictly speaking it contains two oscillating circuits.One circuit has a resistor with a high temperature coefficient, the otherone has a resistor with a low temperature coefficient (see figure 21, (1)and (2)). They are compared by measuring the number of oscillations.The known characteristics enable the determination of the temperature.No calibration is necessary which makes other measuring methodscomplicated and expensive.
'
figure 21: temperature coefficient of the IC sensor
1 Chip There is only one chip for all the functions.
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Evaluation and display The signal provided by this chip must then be evaluated, displayed,compared etc. in a separate element. This principle is similar to that ofthe pressure sensor so that development could be minimised. Even forthe next generation there have been hardly any changes concerningdisplay and setting.
Housing The housing is also almost the same. The new TN looks like the old one(see chapter 4.4.2).
A new development of the housing and the sensor tip has not beennecessary. The housing of the PN and the sensor tip of the SF or ST flowsensors have been used. Especially as regards chemical resistance, thesame statements as for SF or ST apply (see Training manual flow sensors).
This description of the first type is sufficient. The following chapters willconcern the current generation.
Synergy The big advantage for the user is that the setting of the sensors is alwaysdone in the same way (see 4.3) independent of the different processparameters, in this case pressure and temperature. It is not necessary tofamiliarize oneself with different operating concepts all the time. Thereare, of course, some differences in the details: the temperature detection,for instance, works more slowly than the pressure measurement. That iswhy the temperature sensor hardly requires any function to smoothtransient peaks, although this function is not available.Because of equal designs one single adapter (see 4.4.2) is sufficient toconnect either a flow, pressure or temperature sensor to the process.
4.2 Technical details
4.2.1 Sensor element
PT 1000 The sensor element, the real pick-up, is a Pt 1000 (see chapter 3.3). Itwould also be possible to use a Pt 100. The control monitor (see chapter4.3) can automatically adapt to it.
! The user can continue to use all Pt 100 sensors which have already beenintegrated! They can be connected to the display and control monitordirectly via the M12 plug without additional adapter.
Thin film technology This technology is used for the Pt XY sensor elements. A platinum layer isapplied to an aluminium-oxide carrier by photolithographic methods.This is a ceramic material with good thermal conductivity (see chapter2.4). The platinum layer is approx. 1 µm thick. The track has the shape ofa strip with a width of approx. 5 – 100 µm. The strip is protected withglass which is sealed with glass-ceramics. It is connected via connectionpads. This structure limits the mechanical rating of the Pt-T.
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figure 22: Structure of a Pt-T
Components The following components have been used:
1. ceramic carrier Al2O3 substrate2. Pt resistor photographically generated thin-film structure3. cover glass4. electrical connection connection pads5. cables wires6. insulation sealing by glass-ceramics
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4.2.2 Signal processing
The signals are processed in the display and control monitor, brieflycalled basic unit (Strictly speaking only the display and control monitor ofthe modular system is called basic unit. Since the signal processing of theintegrated unit is the same, it need not be handled separately.) Displayand setting is described in chapters 4.3.1 to 4.3.8. This chapter explainshow the signal is processed.
To determine the temperature, the electrical resistance of the sensorelement must be determined as described above. Depending on thehousing (see chapter 4.4.2) there can however be a great distancebetween the sensor element and the basic unit. The distance betweenthe units itself is not the problem. But this makes it necessary to usecables which also have an electrical resistance.
Compensation of the cable resistance A longer cable to the sensor element has a higher resistance. The totalresistance (sensor element + cable) as a systematic error would result inexcess temperature. This has to be considered when the temperature isdetermined. This is called compensation of the cable resistance which isreached by calibration (see chapter 4.3.6).
Microprocessor This calibration function and all the other functions described in chapters4.3.1 to 4.3.8 can only be achieved by a microprocessor. Themicroprocessor has the following functions:
• It controls the conversion of the analog current and voltage values todetermine the resistance and calculates the temperature on this basis.
• It shifts the value in accordance with the set calibration.• It converts the temperature value into the set unit.• It controls the temperature display (upright or rotated).• It enables the setting of the setpoint on a scale by means of a push-
button.• It also enables the setting of the reset point and of the switching
functions on a scale: normally closed, normally open, hysteresis andwindow.
• It controls the timer function of the binary output.• It controls the options for the analog signal output• It stores the entries in the EEPROM.• It averages.• It does plausibility checks.
Block diagram This can be shown by means of a (schematic) block diagram.
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4.3 Basic unit
The basic unit is the same for all types. This is why it is only explainedonce. The functions which are different will be explained separately.Strictly speaking the basic unit is only the display and control monitor ofthe modular system. Since the only difference of the integrated unit isthat the sensor element is located directly in the housing, it need not behandled separately.
1...4 The following descriptions apply to units with 2 outputs. In themeantime types with 4 outputs are also available. If all existingpossibilities were to be listed the text would be rather confusing. So thisis just pointing out that this type does not only have SP1 and SP2 (SP issetpoint), but also SP3 and SP4. The same applies also to the otherfunctions.
4.3.1 Display
This chapter describes the displayed values when the operator does notintervene.
Normal operation Normally the unit is in the RUN mode.
Display At first sight the display looks like the display of the PN. For thetemperature sensor the medium temperature is displayed.
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MODE/ENTER
SET
figure 24: Display
A difference can be seen at the upper left end. It is the unit selected forthe display. If the LED does not light, the value is displayed in °C. If itdoes light, °F is indicated. For units with only one binary output, there isonly one LED to the right indicating the output state.
Resolution The resolution is 0.5°C or 0.5 K. For values higher than 100°C no fourthdigit is available. 0.5 is displayed by the decimal point to the right. E.g.125 means 125.0°C and125. means 125.5°C.To be more precise, this is the resolution of the display. The measurementaccuracy is ± 0.2 °C. For analog outputs the resolution is higher (8 stepsper K, see chapter 4.4.3).
Error display In addition to the display of the medium temperature errors are alsoindicated for temperature sensors.
OL 0L (overload) means too high a temperature.
UL UL (underload) means too low a temperature.
SC 1, SC 2 S( 1 (short circuit) means short circuit of the switching output 1. Theoutput is blocked. S( 2 refers to switching output 2. The display isflashing.
Err Err (error) means a general error, e.g. no sensor is connected. Thedisplay is flashing.
Setting When the Mode button is pressed, the active functions are displayed first.By pressing the Set button the set values are displayed. But only bykeeping the Set button pressed (for at least 5 s), does the unit leave theRun mode and values can be changed. Then the unit is in the SET mode.The functions of the Set mode will be described in the next chapters. Themode is also called the operating mode.
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4.3.2 Switch point
1. Mode
MODE/ENTER
SET
figure 25: switch point setting 1
Mode button The Mode button is pressed. By pressing this button of the unit you canmove through a type of menu. The user is informed by the display whichmenu item is active at present. The button must be pressed several timesuntil SP 1 for the switch point 1 is displayed. "1" is important for unitswith two outputs. When SP 2 is displayed the switch point 2 can be set.
2. Set
MODE/ENTER
SET
figure 26: switch point setting 2
Then the Set button is pressed. When it is pressed only for a short time,the set switch point is indicated with a resolution of 0.5 K. If it is to bechanged, the button must be pressed for approx. 5 s. Then the valueincreases continuously.
3. Enter
MODE/ENTER
SET
figure 27: switch point setting 3
When the requested value of the switch point is indicated, it must beconfirmed by pressing the Enter button. figure 24 shows that the leftbutton has two functions. In the Mode function different menu itemscan be selected, in the Enter function the set value is confirmed. Whenthis button has been pressed, the set value becomes effective. Forapprox. 5 s the display indicates the selected function, which is SP1 inthis case. Then it returns to the RUN mode. If the value is not confirmed,the value set before remains effective. After approx. 30 s the unit returnsto the RUN mode so that there is enough time to reconsider the setting.
Gone too far? What can you do if you have waited for too long and the requested valuehas been exceeded? There is no button which decreases the value. Morebuttons would have made the unit more complicated and expensive. Theonly thing you can do is to wait until the maximum value is reached andit starts with the minimum value again. The next paragraph describeshow the requested value can be reached easily.
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Using the Set button Once in the Set mode, which can be seen by the continuously increasingvalues, you only have to release the Set button once. Every time thebutton is now pressed, the value is increased by one as long as the Setmode is active. If you want to set the switch point to 10°C as in theexample above, you stop pressing the button at about 5°C and press thebutton several times until the correct value is set. Do not forget toconfirm the value afterwards (see chapter 4.3.8).
4.3.3 Hysteresis
The hysteresis can be shown by means of a thermometer, figure 28. Itshould be considered that for mechanical units a precise and free settingis not possible.
figure 28: Hysteresis
The hysteresis is the difference between the setpoint SP and the resetpoint rP. It is a special feature of our sensor and the advantage comparedto the mechanical temperature switch is that the hysteresis can be setwithin a wide range. The minimum hysteresis is 0.5 °C. Since this value isof almost the same magnitude as the switch point accuracy, a lowervalue would not make sense. Of course, the range of the hysteresisdepends on the setpoint. If the setpoint of a unit is for example set to10.0°C, the maximum hysteresis can be 50 K since the minimum value ofthe reset point is -40°C. The hysteresis range is presented in figure 29.
Fixed hysteresis To simplify the correction of the set values and to avoid the entry ofincorrect values, the value of the hysteresis remains the same when thesetpoint is changed. If for example (SP = 10.0°C, rP = 0.0°C, hysteresis =10.0 K) the setpoint is changed to 15.0°C, the reset point automaticallychanges to 5.0°C. The value of the hysteresis thus remains 10.0 K.This is different in the opposite direction. If for the same values (SP =10.0°C, rP = 0.0°C, hysteresis = 10.0 K) the setpoint is changed to -35°C, the reset point is changed to -39.5°C because this is the minimumvalue. In this case the hysteresis is 4.5 K.
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figure 29: Hysteresis range
Reset point The hysteresis is set by the setting of the reset point. The procedure is thesame as for the setpoint (see chapter 4.3.2). An incorrect setting of thereset point, e.g. above the setpoint, is not possible.
rP 1 The setting of the reset point is identical with the setting of the setpointin chapter 4.3.2. Press the Mode button until rP 1 is displayed. "1" isimportant for units with two switching outputs. The second reset point isset via rP 2.
Hno, Hnc When the hysteresis is set, the output function is programmed at thesame time: normally open or normally closed.
1. Mode Mode 0U 1
The Mode button is pressed until OU 1 (for output) is displayed.
2. Set Set Xno
When the Set button is pressed, Hno is displayed. When the button isonly pressed for a short time, the set function, here Hno, is onlydisplayed. After 5 s OU 1 is displayed. After another 5 s the unit returnsto the Run mode. When the function is to be changed, the Set buttonmust be pressed for approx. 5s until the display changes from Hno toHnc. By this setting the output is inverted compared to Hnc. The otherfunctions are explained in chapter 4.3.4.
3. Enter Enter 0U 1
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Setting is confirmed by pressing the Enter button. The menu item OU1 isdisplayed. After approx. 5 s the unit returns to the Run mode.
If the setting is to remain unchanged, you can either wait 5 s until OU1 isagain displayed or, as described in chapter 3, confirm the value bypressing the Mode button once again. When the Set button has beenpressed (more than 5 s), e.g. to have a look at the different alternatives,you have to wait approx. 30 s.
The units with two switching outputs can be set accordingly (OU 2).
The alternative to the hysteresis function is given in chapter 4.3.4.
4.3.4 Window
figure 30: Window
Fno, Fnc The window function enables the monitoring of a range of acceptablevalues. When Fno is set, the output is open (0 signal) when thetemperature is below the reset point or above the setpoint. The output isclosed (1 signal) when the temperature is between the setpoint and thereset point. When Fnc is set, the output is inverted. When the windowfunction is set, the hysteresis is set to the minimum value 0.5°C (pleasealso see chapter 5.1).
The setting of the window function is identical with the hysteresis setting(see chapter 4.3.3).
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1. Mode Mode 0U 1
The Mode button is pressed until OU1 is displayed.
2. Set Set Fno
When the Set button has been pressed, Fno is displayed first. When thebutton is pressed for a short time, the set function, here Fno, is onlydisplayed. After 5 s OU1 is displayed. After another 5 s the unit returns tothe Run mode. When the function is to be changed, the Set button mustbe pressed for approx. 5 s until the display changes from Hno to Hnc,then to Fno and finally to Fnc. When the button is kept pressed or justpressed once, the same values are displayed again and again. When therequested function, in this example Fno, is displayed, this selection mustbe confirmed.
3. Enter Enter 0U 1
Setting is confirmed by pressing the Enter button. The menu item OU1 isdisplayed. After approx. 5 s the unit returns to the Run mode.
Fixed window As for the hysteresis the value of the window remains unchanged whenthe setpoint is changed. The example for the hysteresis at the end ofchapter 4.3.3 can also be taken as an example for the window function.
The units with two switching outputs can be set accordingly (OU 2).
4.3.5 Analog output
The resolution of the conversion is 8 steps per degree. This means thatthe complete measuring range (-40°C to 150°C) is divided into 1520steps (190 * 8). A higher resolution would not make sense in view of thedifferent measuring errors. The total measuring range is however onlyused in some applications. It is useful to adapt the analog output signalto the real measuring range, e.g. for display or evaluation. If for examplewater temperatures between 0°C and 100°C are to be monitored, it canmake sense to set 0°C as the lower end of the analog output (0 V or 4mA) and 100°C as the upper end of the analog output (10 V or 20 mA).The measurement accuracy is ± 2 °C, see above.
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! This should not be misunderstood. The resolution, the precision is notincreased by this. In the above-mentioned example the measuring rangehas almost been divided in half. This does not mean that the smallertemperature interval is divided into 1520 steps. The interval is nowdivided into 800 steps (8 steps per degree).
ASP The lower end of the analog output is set by the function ASP (analogstarting point). The setting range is between -40 and 140 in steps of0.5°C. The value can be set as follows:
1. Mode Mode ASP
The Mode button is pressed until ASP is displayed.
2. Set Set 10.0
When the Set button has been pressed, the set value is displayed. Whenthe button is pressed for a short time, the value, here 10.0, is onlydisplayed. After 5 s ASP is again displayed. After another 5 s the unitreturns to the Run mode. If the value is to be changed, the Set buttonmust be pressed for approx. 5 s. The value is then increasingcontinuously. When the value 0.0 has been reached, it can be confirmed.
3. Enter Enter ASP
Setting is confirmed by pressing the Enter button. The menu item ASP isdisplayed. After approx. 5 s the unit returns to the Run mode.
If the setting is to remain unchanged, you can either wait 5 s until ASP isagain displayed or, as described in chapter 4.3, confirm the value bypressing the Mode button once again. When the Set button has beenpressed (more than 5 s), e.g. to have a look at the different alternatives,you have to wait approx. 30 s.
AEP This function enables the setting of the upper end of the analog output(analog end point). The setting range is between -30 and 150°C. Settingis identical with the setting of ASP. When the value 100 is set here, theabove-mentioned example applies.
Minimum interval In view of the resolution (see above) and the measuring precision theinterval is limited to at least 10 K. This means that AEP = ASP + 10. Thisequation defines the maximum value for ASP and the minimum value forAEP.
ASPmax = 140° CAEPmin = -30° C
In contrast to the hysteresis and window function the interval does notremain the same when the lower end, ASP, is changed. This means thatASP cannot be set over the complete range. Only if AEP is set to 150, canASP be set to 140. Otherwise ASP is limited to AEP - 10. The sameapplies to AEP accordingly.
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AOU With this function a current or voltage output can be selected.
1. Mode Mode A0U
The Mode button is pressed until AOU is displayed.
2. Set Set I
When the Set button has been pressed, the set function is displayed.When the button is pressed for a short time, the function is displayed, inthis example I for current output (4-20 mA). After 5 s AOU is displayed.After another 5 s the unit returns to the Run mode. If the value is to bechanged, the Set button must be pressed for approx. 5 s. The displaythen changes between I and U for current or voltage output (0-10 V).When the requested function is displayed, it must be confirmed.
3. Enter Enter A0U
Setting is confirmed by pressing the Enter button. The menu item AOU isdisplayed. After approx. 5 s the unit returns to the Run mode.
If the setting is to remain unchanged, you can either wait 5 s until AOU isagain displayed or, as described in chapter 4.3, confirm the value bypressing the Mode button once again. When the Set button has beenpressed (more than 5 s), e.g to have a look at the different alternatives,you have to wait approx. 30 s.
4.3.6 Other settings
The temperature sensor offers special setting functions the pressuresensor does not have. A short description will follow, first of all a tablesummarising all functions.
diS With this function the type of display is set (diS for display). On the onehand this concerns ° C or ° F. On the other hand a rotated display can beselected. The user does not always have a choice as regards the placewhere the sensor is mounted or the sensor mounting is incorrect. If thedisplay is then difficult to read because the display is standing on itshead, no mechanical changes are necessary, the display can simply berotated by 180°.
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1. Mode Mode diS
The Mode button is pressed several times until diS is displayed.
2. Set Set °o(
When the Set button is pressed several times, the set unit/type of display,here ° C as a standard, is displayed. When the button has been pressedfor 5 s, ° C, ° F, r° C and r° F are displayed alternately. r means rotated by180°. Any change must be confirmed.
3. Enter Enter diS
When the setting has been confirmed by pressing the Enter button, theactive menu item is displayed. When the button is pressed once again (inthe Mode function), other menu items are displayed or you wait 5 s untilthe unit returns to the Run mode.
Min/Max Another special feature of the temperature sensor is that the highest andthe lowest temperature can be displayed, as for a Min/Max thermometer.
Hi The maximum temperature is displayed.
1. Mode Mode Xi
The Mode button is pressed several times until Hi is displayed (for high).
2. Set Set 40.5
When the Set button is pressed once, the maximum value, 40.5°C in thisexample, is displayed. When the button is pressed for 5 s, the value isdeleted. - - - is displayed.
Set (> 5 s) - - -
3. Enter Enter Xi
When the deletion has been confirmed by pressing the Enter button, theactive menu item is displayed. When the button is pressed once again (inthe Mode function), other menu items are displayed or you wait 5 s untilthe unit returns to the Run mode.
Lo The minimum temperature is displayed.
The procedure is the same as for Hi.
Compensation of the cable resistance For longer cables to the sensor element the cable resistance, see 4.2.2,can no longer be ignored. It must be compensated for by the menu itemCAL.
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Cable resistance The following table gives an overview of the measuring error caused bythe cable resistance. It refers to copper cables with an electricalconductivity γ of:
γ = 58 m/Ωmm2
The given values refer to a Pt1000.
Cable cross-section[mm2]
0.5 0.75 1.5
Resulting error (K)for a cable length of
10m15 m
100 m150 m200 m
0.180.271.792.693.58
0.120.181.191.792.39
0.060.090.600.901.19
Correction factor The resistance of the cables also depends on their temperature. This isdescribed by the temperature correction value α of the electricalresistance. For copper (at 20°C) the following applies:
α = 3.9 10-3 1/K
The resistance difference can be calculated as follows:
( 3) ∆R = α R ∆T
R[Ω]: resistance∆R[Ω]: resistance difference∆T[K]: temperature differenceα[1/K]: temperature correction value
CAL With this menu item the displayed temperature value can be shifted by -9.9 to +9.9°C in steps of 0.1°C for calibration.
1. Mode Mode (AL
The Mode button is pressed until CAL is displayed.
2. Set Set 0.0
When the Set button is pressed, the set value is displayed. When thebutton is pressed for a short time, the value, here 0.0 (default value), isdisplayed. After 5 s CAL is displayed. After another 5 s the unit returns tothe Run mode. If the value is to be changed, the Set button must bepressed for approx. 5 s. The values increase continuously within thesetting range. When the requested value is displayed, it must beconfirmed.
3 . Enter Enter (AL
Setting is confirmed by pressing the Enter button. The menu item CAL isdisplayed. After approx. 5 s the unit returns to the Run mode.
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If the setting is to remain unchanged, you can either wait 5 s until AOU isagain displayed or, as described in chapter 3, confirm the value bypressing the Mode button once again. When the Set button has beenpressed (more than 5 s), e.g to have a look at the different alternatives,you have to wait approx. 30 s.
Locking / unlocking To make unwanted or inexpert settings more difficult, the unit can beelectronically locked or unlocked. For this purpose keep bothpushbuttons pressed for > 10 s in the RUN mode. If an attempt is madeto change a parameter in the locked state, Loc is displayed.
4.3.7 Enhanced functions
For more demanding tasks a unit has been developed (TR8430, seeCatalogue) which apart from 4 outputs and a 4-digit display alsoprovides enhanced functions. This made it necessary to to partly usedifferent abbreviations which will be described below.
EF When scrolling through the menu you come to the display
EF (enhanced functions)
When selecting this menu point you will find the following functions:
COF This point has the same meaning as CAL above (calibration offset, see4.3.6).
Car This allows a simple reset of the value set through COF back to thedefault setting (calibration reset). After the reset the following displayappears:
Set (> 5 s) - - -
as for pressure The following parameters are set in the same way as for the pressuresensor (see Training manual Pressure Sensors). The pressure sensormanual describes the process more detailed. Here we will only brieflyexplain the meanings.
dr1, dS1 Here the switch-on or switch-off delay for output 1 is set (delay reset,delay set). A value 3 for dS1, for instance, means that the limit value ofthe temperature has to be exceeded by 3 s before the unit switches.Outputs 2, 3 and 4 can be set accordingly (independent from eachother).
dIS Not to be confused with dr or dS. Here, a damping of the display can beset which is done by means of internal averaging. This is useful to e.g.read the values more easily in the case of fast changing temperatures.The damping does not refer to the output.
UnI Here the unit (°C or °F) is selected, as under dIS above (4.3.6).
FOU1 This abbreviation (function output 1) hides an interesting function toincrease the operational reliability. In the case of an error (short circuit or
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cable break at the sensor) the outputs of the other types are switchedoff. Here, selecting
0n or 0ff
defines the state of the output in the error case. This selection can bemade accordingly (and indepenent) for outputs 2, 3 and 4.
4.3.8 Overview
Handling TS, TN
1 2 3 4 5 6 7 8 9 10
12.5MODE/ENTER
SP1
SET
10.0
SET
> 5 s -39. 150
MODE/ENTER
MODE/ENTER
rP1
SET
8.0
SET
> 5 s -40 9.5
MODE/ENTER
MODE/ENTER
0U1
SET
knoSET
> 5 s kno knc Fno Fnc
MODE/ENTER
MODE/ENTER
ASP
SET
0.0
SET
> 5 s -40 90
MODE/ENTER
MODE/ENTER
AEP
SET
100
SET
> 5 s 10 150
MODE/ENTER
MODE/ENTER
A0U
SET
I
SET
> 5 s I U
MODE/ENTER
MODE/ENTER
diS
SET
o[
SET
> 5 s o[ of ro[ rof
MODE/ENTER
MODE/ENTER
[AL
SET
0.0SET
> 5 s -9.9 9.9
MODE/ENTER
MODE/ENTER
ki
SET
40.5
SET
> 5 s ---
MODE/ENTER
MODE/ENTER
Lo
SET
8.0
SET
> 5 s ---
MODE/ENTER
Explanations The value 12.5 in line 2 is an example (all values in °C). The other entriesin column 2 are the fixed displays which inform the operator which menuitem is active at the moment. You get from one item to the next bypressing the Mode button. To simplify the table, the menu items SP2, rP2etc. which are only important for units with two switching outputs are
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not indicated. The damping function of the pressure sensor has not beenused because the response of the temperature sensor is much slowerthan that of the pressure sensor, see transient function in chapter 3.3.
The values in column 4 are also examples. When SP 1 is for exampledisplayed when the Mode button has been pressed, the setpoint 1, inthis example 10.0, is displayed when the Set button has been pressed.The current value (12.5) in this example is above the setpoint, output 1should switch. The reset point 1 in this example is 8.0. The delay for thereset point 1 (dr1) was set to 4 s. The output function has been set tohysteresis and normally open. An explanation of the terms hysteresis andwindow is given in chapters 4.3.3 and 4.3.4. The values are displayed in°C, the maximum temperature value is 40.5°C, the minimum value 8.0°C.
Columns 7 - 9 indicate the complete range of values which can be setwhen the Set button is pressed for more than 5 s when column 4 isdisplayed. In line 3 the value for SP1 would of course not start with -54.5but with the set value of 10.0. If you waited however until the completerange of values has been displayed, that is until 124.5, the displayedvalues would start again at -54.5. The values in line 4 for the reset point1 (rP 1) cannot cover the complete range. The smallest value is given bythe maximum hysteresis, the highest value by the minimum hysteresis. Inthis example SP1 has been set to 10.0. The same applies to the functionsASP and AEP. The value for ASP would not start with -40 in this examplebut with the displayed value 0.0. In columns 7-9 however the completerange of values is to be displayed. The values for AEP can however notcover the complete range of values (see chapter 4.3.5) because AEP mustbe at least ASP + 10. As regards the functions OU1, AOU and diS nofigures are set but the switching or output function and the unit or typeof display are programmed. The values indicated for Hi and Lo cannot bechanged but only be deleted.
Temperature range The maximum temperature value for TN is 124.5°C. For TR it is 149.5°C.
To make the table esier to read only the standard functions have beendescribed. For the enhanced fuchtions see 4.3.6.
Do not forget! If a value has been changed by keeping the Set button pressed, it mustbe confirmed by pressing the Enter button. Otherwise the value setbefore remains effective.
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4.4 Overview of the units
4.4.1 Summary
TN The sensor element, the Pt-T, and the control monitor of the TN arecontained in one housing. The TN is thus called temperature sensor withintegrated control monitor. The main feature of this unit is its compactdesign. Figure 31 shows the TN measuring the temperature in a tube.
first version This type has been replaced by an improved ty (see figure 32).
figure 31: Mounting TN
This "short" design has been replaced by a longer tip.
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figure 32: Improved type TN
The various adaption possibilities as can be seen for the SI100 (seeTraining manual Flow Sensors) allow the adaption to all common processfittings (e.g. M12, G1/4, G1/2 etc., see also 4.4.2). A list of the currentlyavailable available adapters can be found in the ifm website.
TR The difference between temperature and pressure measurements is thatthe temperature is not always evenly spread in the medium or only aftera long time. There can for example be a great difference between thetemperature inside a tube or a tank and the temperature near the wall(please also see chapter 2.4). For many applications the correct positionof the sensor element is important. In other words, the processconnection plays a very important role. This is shown by the variety ofunits on the market, e.g. DIN thermowells for temperature sensors. Thesensor meets these requirements thanks to a modular design which willbe explained and shown with some examples below (please also seechapter 4.4.2). Important aspects are:• separation between control monitor and sensor element• versions
• rigid connection with TT• connection via cable, direct for TS, via connecting cable for TT
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Modular design The modular design is characteristic of the new sensor family. Asdescribed in 1.1 it is not easy to meet the various requirements of thevariety of applications by offering only some units.
The objective of the modular design is a free combination of theindividual components consisting of a control monitor of type TR and thesensor part of type TT or TS to guarantee the highest flexibility for theuser.
figure 33: Control monitor TR
In contrast to the pressure sensors the control monitor and the sensorelements are designed in a way that a rigid connection between displayunit and sensor as well as their separation by cable connections arepossible without any changes in the sensor element. The respectiveaccessories are available as an option.
Rigid connection For the rigid connection the TT temperature sensor with protective tubeand the control monitor TR are fit into each other and screwed by a nut.Two cylinder pins guide the plug and socket connection during thisprocedure and avoid mechanical strain.
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New types figure 34, 35 and 36 have to be complemented by the new types TT0061and TT1601 which have been designed specially for application inhygienic areas (food industrie). The TR8430 has been added as anothercontrol monitor.
*0 '
' '
0$1$ 6$4 $/$ $0$$*$*
/ 75
/ 75
figure 34: rigid connection
Figure 34 shows the mounted unit on the left and the individual parts ofthe mounting kit on the right in a type of exploded view.
The process connection is made via a progressive ring fitting (figure 35).
0/$**1$/ /5
figure 35: rigid progressive ring fitting
Flexible connection For the flexible connection the connecting cable can be fitted to the TRcontrol monitor and the TT temperature sensor with protective tube asusual.
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*0'
' '
figure 36: Flexible connection
Figure 36 shows examples of the mounted unit on the left. On the rightyou can see how the connection is made.
In the real application the TT temperature sensor can be mounted intanks, tubes or thermowells via a progressive ring fitting or other clampsand ensures pressure resistance and optimum alignment. ifm offers aprogressive ring fitting adapter with 1/2" thread which enables this typeof fixing.
$4$*$2/2 -+;
5 5 5
0/$**1$ / / *$4 $
Configurator
It can be seen that temperature sensorsmay consist not only of one single piecebut of a system of various components. Inifm's websites a configurator helps tochoose the correct components which areneeded and matching for such a system.
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$4$*$2/2 -+;
5 5 5 5
*$4 $ *$4 $
#< 0$ 0$*16$$2/2 0 )
5
figure 37: flexible screwing
The process connection can be made via common thermowells or via aM0 adapter. The following figure 38 shows some M0 adapter.
pipe fitting clamp Varivent
figure 38: M0 adapter real
As an alternative the compact TS sensor can be used.
These adapters can be used for for either flow, pressure or temperaturesensors. As explained in more detail in the Training manual PressureSensors this type of metal-to-metal sealing (if mounted correctly, seeMounting Instructions) results in a practical flush process fitting whichmakes the unit suitable for for use in hygienic areas. For information ofEHEDG testing or 3A certificate please refer to the catalogue or contactyour ifm specialist. A short overview on the different approvals and thesignification of the abbreviations can be found in the Training manualProtection Ratings an Classes.
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.
.
figure 39: compact cable sensor
figure 39 shows a mounted unit on the left and the connection on theright.
For the measurement e.g. of the oil temperature in an oil pipe the TScable sensor with very compact design can directly be screwed into thepipe system by means of a progressive ring fitting of size 10.
figure 40: Process connection by means of a T-piece
figure 40 shows the process connection of the compact cable sensor bymeans of a T-piece.
Like the TT sensor, the TS sensor can also be connected to the process bymeans of thermowells and adapters, see figure 36.
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4.4.2 Mechanical characteristics
This product group comprises a variety of components because of themodular design. At first sight this may be confusing. This chapter showshowever that this system is not very complicated. It is a positiveargument that a variety of process connections can be covered by onlyfew components and adapters. Stocking is easier for the user if he doesnot need a complete unit for each process connection. It is of coursemore economical to purchase just an adapter instead of a complete unit.
Overview of the types
TN
TR
TN For the TN unit Pt-T and control monitor are integrated in one housing.The dimensions can be seen in figure 40. A mounting example is given infigure 31.
The first generation TN has ashorter sensor tube. It also had a threadinstead of a lock nut for connection with the adapter.
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#"
)
)
#"
)
1 7 segment display2 programming button3 lock nut for adapter
figure 41: TN temperature sensor
TR The TR only contains the control monitor. An additional Pt-T is required.The scale drawing is given in figure 42.
=>
)
#"
1 7 segment display2 programming button
figure 42: TR control monitor
Pt-T Types TS and TT are offered as Pt-T. They are described below.
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! The control monitor is not only suitable for these types. Any Pt1000 canbe connected. A Pt 100 can also be connected. The control monitoradapts to it automatically. It should however be considered that theinfluence of the cable resistance on the measuring result is 10 timeshigher (see chapter 4.3.6). The following example would be possible. Theuser has already used a Pt-T in the plant. He is however not satisfied withthe evaluation of the measuring signals and would like to have anadditional display on site. In this case the TR can be used.
TS The TS is used when a compact sensor is needed. It has a Pt1000 sensinghead. The dimensions are given in figure 42.
#"
)
)?
figure 43: TS
The TS is available in lengths of L = 2 m and L = 5 m.
Process connection There are three possibilities:
• direct, e.g. by means of progressive ring fitting• in common thermowells (with accessories)• in M0 thermowells (with accessories)
A short description of these possibilities will be given below.
Progressive ring fitting figure 40 shows an example. figure 44 shows the dimensions.
= >
figure 44: progressive ring fittingFigure 43:
Common thermowells As an accessory the E350XX thermowell into which the sensor is insertedis required. XX stands for the different thermowell lengths.
?
= >
= >
figure 45: thermowells
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The nominal lengths are 100, 200, 300 and 500 mmwith L2 being 82, 182, 282 and 482.
Screw connection The cable entry is sealed by means of a screw connection (see figure 37).
= >
figure 46: screw connection
M0 thermowells They enable frequent process connections with special features. In thefood industry a typical requirement for hygienic reasons is for examplethe use of flush mounting measuring systems. Typical connections areTri-Clamp, Varivent etc. M0 adapters are available for these connections.
For this, the TS is inserted into a M0 thermowell (see figure 38).
= >
?
$ $ #< 0$
figure 47: M0 thermowells
M0 thermowells are available with the nominal lengths of50 and 100 mm with L2 being: 45 and 95 mm.See catalogue underE34110 E30005E34410 E30050
Again, the cable entry is sealed by means of a screw connection.
The M0 thermowell is screwed into the required M0 adapter.
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))
)
$
*$/ $/$
$*$/ $/$
)
*$/ $/$
$
figure 48: M0 adapter
TT For the TT the Pt1000 is integrated into a rigid protective tube.
?
#"
)
)
)
figure 49: TT
The TT is available with the nominal lengths 100, 200, 300, 500 mm,with L being: 137, 237, 337, 537 mm.
There are two possibilities to connect the TT to the TR control monitor:
• rigid connection• connection via cable
Rigid connection The sensor and the control monitor almost form one unit, comparable tothe TN. The advantage of the modular design is that not for everythermowell length an individual unit is needed but that thermowells withdifferent lengths can be connected to one and the same control monitor.
Mounting set The mounting set is used for this connection. It provides a mechanicallystable connection of the components and avoids at the same time thatthere is too high a mechanical strain during mounting (see figure 33).
$$$ /
figure 50: mounting set
As already mentioned and can be seen in this chapter, it was not so easyto meet the two requirements on the sensor:
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• only a small number of components, one basic unit• adaptation to as many common process connections as possible.
The following detailed figure 51 shows that some thoughts and somemechanical efforts are required for this.
figure 51: cut-away view rigid connection
Connection by means of a cable It is used if, as for TS, a flexible connection is required between sensorand control monitor or if the requested place of display is far away fromthe place of measurement. Even for places of measurement difficult toaccess the display can be read easily and the unit is easy to set. Aconnecting cable with plug and socket is used. The other connections(except for the mounting set for rigid connection) are the same as for theTS.
• progressive ring fitting, figure 44• conventional thermowells, thermowells figure 45 with screw
connection figure 46• M0 thermowells, M0 thermowell figure 47 and adapters figure 48
Overview The following figure shows the different versions once again. To get acomplete set of components you only have to follow the arrows.
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connecting cable
figure 52: Overview modular system
Sequence The arrows in figure 52 shall help to find the corresponding components.They do not show the mounting sequence. This is not possible because
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the components are partly fitted into or on top of each other. Thepreceding figures show this clearly.
Configurator Of course, such a static figure has some restrictions compared to adynamic representation. As mentioned at figure 37 this can be found inifm's websites. The configurator helps to choose the correct componentswhich are needed and matching for such a system. figure 52 should giveonly an idea of the system. It can not be shown there which of all thecombinations are possible. By the same reason not every component isshown in figure 52 there are examples.
Material The materials of which the sensors consist must meet harshrequirements. The housings must for example be resistant to cleaningagents and the wetted material must be resistant to chemicals. This iswhy stainless steel is used. The next paragraph gives a short overview.
All contacts are gold-plated.The housing materials for TN and TR are: stainless steel 304S15, PBTP,PC, EPDM/X, FPM and PA. Further information on the materials is given inthe catalogue.Wetted materials:for TN stainless steel 303S21for all the other sensors, thermowells and adapters stainless steel316S12.screw connection (here also FPM) and mounting set stainless steel303S21progressive ring fitting stainless steel 320S17The cable is available in two versions:connector housing PVC, nut stainless steel 320S17connector housing TPU, nut nickel-plated diecast zinc
Vibration resistance Pt-T's are rated for up to 40 g in a range from 10 Hz to 2 kHz. For thecomplete unit, TS or TR, 20 g is given (to DIN/IEC 68-2-6, 10-2000 Hz).
Shock resistance The limit of the shock resistance is a half-sine 100 g pulse of 8 msduration. For the complete unit, TS or TR, 50 g is given (to DIN/IEC 68-2-27, 11 ms).
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4.4.3 Electrical characteristics
Connections
analog normally open normally closed
TN 2
L
L+
4
1
3
Xno
Fno
2
L
L+
4
1
3
Xnc
Fnc
TR 2
L
L+
4
1
3
Xno
Fno
2
L
L+
4
1
3
Xnc
Fnc
TR 4
1
3
2
L+
L
4-20 mA0-10 V
4
1
3
2
L+
L
Xno
Fno
4
1
3
2
L+
L
Xnc
Fnc
The TR family has been complemented by a type with four swichingoutputs.
?&
?
<
<<<2222
@;A9@,@B=C%B<=
D22E
D22E
'
figure 53: TR with four switching outputs
2-wire figure 53 shows that the unit is designed for the connection of 2-wiresensors (see 3.4.1). An input circuit for the connection of 4-wire sensors(see also 4.3.7) is in preparation.
output function The unit can be programmed with the help of the display by pressing theprogramming buttons.
Analog output The analog output can be selected (4-20 mA <-> 0-10 V) and isscaleable. This means that any temperature value of the measuring rangecan be allocated to the lower end (4 mA or 0 V) and the upper end (20mA or 10 V). The description of the procedure and other information aregiven in 4.3.5.
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Analog output 4-20 mA maximum load 500 ΩAnalog output 0-10 V minimum load 2 kΩ
Power-on delay This is the time between the moment when the operating voltage isapplied and the moment when the correct switching signal is given. It is1 s.
Operating voltage The operating voltage is 20-30 V DC (incl. residual ripple).
Current rating The maximum current rating is 250 mA. The outputs are protectedagainst reverse polarity and overload. They have a pulsed short-circuitprotection. This information concerns the binary outputs.
Current consumption The sensor needs less than 66 mA for its own supply.
4.5 Summary
The following summary shows the advantages of electronic temperaturesensors. First of all we would like to go into the "classic" processconnection.
4.5.1 Conventional temperature sensors
It has already been mentioned that especially the process connection oftemperature sensors must meet harsh requirements (e.g. in chapters 2.4and 4.4.2). In the course of time special types have become widespread.
! -! ! @! 3
figure 54: Conventional temperature sensors
A variety of tubes, thermowells and screw connections exists. It is thusadvantageous to have a clever system with a relatively small number ofcomponents (see chapter 4.4.2).
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Conventional sensors often have a cap in form of a hat which only hasthe function to seal the terminal chamber. A lot of material and space isneeded. Indication or setting on site is not provided.
4.5.2 Control monitor
The TR control monitor has a 7-segment display which has already beenused for the pressure sensors. This enables a display on site.
The control monitors of type TR2430 and TR7430 offer the followingfeatures:
• 7-segment display with 3-digit LED display• two programming buttons, the left button indicates the program
steps, with the right button the respective value can be set.• change from °C to °F in the menu• free programming of the setpoints and the reset points (for TR7430
two setpoints and reset points, but without analog or voltageoutput),
• a min/max memory stores the highest and the lowest value duringoperation and can be reset
• change between analog output (4-20 mA) and voltage output (0-10 V) for TR2430
• combination of all ifm sensor types possible, direct or via intermediatecable
• evaluation of Pt100 (conventional temperature resistance) and Pt1000possible by means of the same control monitor. The control monitorcan identify the type of sensor (Pt 100 or Pt 1000) automatically
• standard US100 plug and socket connection to the sensor as well asto the control cabinet
• forms a unit with the TT sensor with protective tube by the use of themounting set
• threaded sensor element for nut or separate mounting• the temperature range can be limited to 10 K and then be assigned to
4-20 mA or 0-10 V. The complete voltage or analog output can forexample be shifted to an area of 80-90°C.
4.5.3 Sensor in the modular system
• Sensor element TS with cables of different length can directly beconnected to the control monitor and be clamped e.g. directly in ahydraulic T-piece via progressive ring fittings.
• TT temperature sensor with protective tube can pass the signal on tothe control monitor via any intermediate cable (US100).
• The sensor element TS can be "clamped" into all thermowell versionsamong others also DIN thermowells and ifm MO thermowells via ascrew connection.
The TT temperature sensor with protective tube can be screwed into anysurface, any thermowell with sufficient internal diameter in any heightand rotational direction via a progressive ring fitting or screw connection.
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5 Applications
5.1 Application example
The different functions of the temperature sensor will be described belowby means of a realistic application example. This example is simple andclear, and so it can be used to explain again the hysteresis and windowfunctions.
What can the temperature sensor do? In this example the different functions of a sensor, e.g. TS with twooutputs will be explained to show that one single sensor is sufficient tocope with a relatively complex control task.
Description In a tank a temperature of about 50°C is to be maintained. For the sakeof simplicity the cables, pipes, valves, etc. have not been considered inthe drawing. If the temperature goes down, the heating is to be turnedon to increase the temperature again. A lamp is to indicate whether thetemperature is within the correct range. The values of the set and resetpoints as well as the switching functions can be seen in the figure. Thetime diagram below shows the process by way of example.
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.% F '% F <,F9;
.% F '% F <,F!;<
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figure 55:Application example
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figure 56: Time diagram
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5.2 Further examples
Some real applications will be presented below. The customer's benefitfrom ifm temperature sensors will be described in detail.
5.2.1 CIP Cleaning-In Place
Automatic inside cleaning of all production systems used in the foodindustry such as apparatus, tanks, heaters, pipes and cables must bepossible (cleaning in place - system remains closed). The productionsystems are cleaned without being taken apart or substantialmodifications being made.Cleaning solutions are moved past the wetted parts via pumps or aresprayed onto the surfaces with suitable devices. With the correct pressurecontrol there are the following advantages:− repeatable cleaning results− safe operation− high economic efficiency
Temperature sensors and CIP cleaning To obtain an optimum cleaning effect, it is important that certaintemperatures depending on pressure, flow velocity, concentration ofcleaning agents and cleaning duration are achieved. When the requestedtemperature has been reached cleaning or minimum exposure timesmust be complied with to eliminate the layers of dirt.
Since the cleaning times cannot be assessed until the instant the cleaningagent has achieved the requested temperature over the whole section tobe cleaned, the complete system requires consistent monitoring, speciallythe return flow.
Task− Monitoring the vapour temperature− Checking the flow and return flow temperatures of the cleaning
agents and washing liquids− Monitoring the temperatures of tanks for the repeated utilisation of
the cleaning fluids
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$4
4
4$
*$
$*$
4$ 6*$
6*$
7 $*6$$/$
figure 57: compact CIP system
Advantages of these sensors
− Stable temperature control by means of a tight two-step control− The sterilisation temperature (141°C) can be accurately monitored
(process reliability)− With a tight hysteresis too high temperatures can be avoided, thus
allowing energy savings (energy as a cost factor)− Precise setting on site (high flexibility) with local evaluation of the PT-
1000 sensor (reduction of personnel cost because of a better andmore efficient handling and simple decentralised CIP systems -advantage over a unit with analog output)
− No calibration required because the sensor and control monitor canbe replaced separately (time saving)
− Simple fault location by means of display on site (time savingcompared to analog output)
− Because of the modular design the control monitor is independent ofthe actual sensor type (storage cost kept to a minimum)
− High uptime of the installation because of mechanical stability andlong-term stability of the sensors in conjunction with high shock andvibration resistance as well as locking to protect against unauthorisedtampering with the program (advantage over the contactthermometer)
− For the unit TR7 self-monitoring possible by means of a second switchpoint (safety)
− Excellent visibility of the LED display even under poor illuminationconditions in the plant
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− Compatibility with competitive units because PT100 detection isautomatic and its evaluation is identical to PT1000 (changeover costunimportant)
− Interchangeability of the parts, and so only few parts need to be instock (storage cost)
− Mounting the individual control monitors at one location to ensure asimple plant set-up
5.2.2 Yeast pre-enrichment system for breweries
In this pre-enrichment system for yeast the yeast is put in an optimumcondition before it is added to the wort to shorten the beer fermentationtime, thus enhancing the beer quality in general. The operatingtemperature or storage temperature can be set via an outside heatexchanger.Behind this heat exchanger the yeast is pumped through an aeratorwhere it is supplied with oxygen. A precise temperature controldetermines the successful use of this installation.
The wort with the treated yeast requires no further aeration and does notfoam when it is filled into the tank.
$* $$$
$* 7
$0$$
"/$$$
00
$ $$
figure 58: yeast pre-enrichment system with temperature control
Advantages of the temperature sensors with modularly designed control monitors:
− Hygienic mounting of the sensor (PT1000 element) in a M0thermowell by means of M0 adapters
− Increased flexibility compared to clamp fittings− No dead space
− Small hysteresis leads to a stable and precise temperature monitoringby eans of a two-step control
− Via the analog output or voltage output the higher-level controllercan precisely define the yeast control (transparent processes with highproduct quality because of high-quality yeast yield which is availablein the correct quality at the right time).
− Long-term stability leads to a good repeatability of the temperaturecontrol
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− High uptime because no mechanical components are used (advantageover the contact thermometer and thermostat)
− Clear set-up of the installation because of the modular design of thetemperature sensors. The control monitor can be mounted at anaccessible location independent of the temperature sensor via a cableconnection.
5.2.3 Washing systems
Different requirements are made for washing systems (continuous orintermittent) depending on the wide range of application areas.
Whereas for the conventional belt-type washing systems certain cleaningtemperatures must be reached for the prewashing and main washingoperations as well as for drying to achieve an optimum cleaning effectand an optimum utilisation of energy via a heat exchanger, the crucialpoint for cleaning apparatus used for hospitals, pharmaceutical researchand production, etc. is to safely attain certain temperatures fordisinfection and sterilisation.
The temperatures of the washing operation and the function of theheaters and heat exchangers must be monitored.
$$
4$ $ 7 4 4$$ 0$4*/ $ *$*
4*/0$ 0$4*/
$ $"/$
$* 4$
figure 59: belt-type washing system
Advantage of electronic temperature sensors:
− Temperature limitation by means of a two-step control (energysavings and monitoring the cleaning temperature)
− Mounting the control monitors at one location of easy access outsidethe washing system
− Time saving because of on-site setting outside the control cabinet,multiple functions for precise and simple tting
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− Saving memory space in the central controller− Locking to avoid unauthorised tampering− Protection rating IP67 for spray mist applications− Robust field housing for severe conditions at higher operating
temperatures
5.2.4 Pasteurisation systems (short-time heating systems)
Preserving for example juices for a longer period can be done by thermaltreatment with pasteurisation systems, also called short-time heatingsystems. Without a sustained change to the product (e.g. taste, colour) along-term preservation is achieved by means of a short-time heating to74° C.
Description of the installation This type of installation is a 3-stage heat exchanger:− Preheater− Heater− Cooler
The beverage is fed to the preheater from the buffer tank or directly fromthe upstream installation via a dosing pump where it recovers energyfrom the medium in the downstream heater. In the actual heater thepasteurisation temperature is exceeded for a short time, with themedium being conveyed to the cooler via the preheater where it isbrought to the filling temperature.
*$$ > ;
:$) 7 $2
$
00
$$
0$$$
4$
$
$ 4$
6$ 7
figure 60: short-time heating system for pasteurisation of juice etc.
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Advantages of the described sensors:
− Tight switch point setting for the control monitor on site− Temperature monitoring in the pasteurisation system with a tight
hysteresis and short temperature response times for an exact process(process safety) with optimised energy utilisation (cost)
− Achieving the pasteurisation temperatures directly behind theheater
− Upward temperature limitation− Quality assurance− Energy saving
− Hygienic mounting without dead space by means of M0 adapters incommon fittings such as Varivent, Triclamp, etc.
− Modular design with separate control monitor (cost saving forstorage, mounting and integration in the overall control system)
− Programming on site− Mounting the control monitors for the different measuring
points at one location− Analog or voltage output for the central controller
− Long-term stability with operational reliability (cost savings byconstant product quality and short downtime of the installation) bymeans of
− IP67− Robust field housing (mechanical and chemical)− Long-term stability of the sensor element and the control
monitor
5.2.5 Tank and vessel monitoring
Example fermentation control This application will be explained by means of fermentation control in thefermentation cellar of a brewery.
In the fermentation cellar the yeast is added to the wort, which startsfermentation. Within about eight days the fermentable sugar isconverted into alcohol and carbonic acid.
Depending on the requested kind of beer and the corresponding kind ofyeast, this fermentation operation takes place in cylindrical cone-shapedtanks with a cooling jacket at temperatures between 0 and 20°C until theyeast can either be removed from the bottom or siphoned off from thetop. The temperature control results in the velocity and the quality offermentation. If faults are made here, undesired fermentation by-products such as fatty acids form (see figure 1).
Requirements and advantages of the described temperature sensors
− Exact repeatability of the temperature values around 0.5°C (plantsafety)
− Mounting of the control monitor at eye height via a cable connectionto the sensor, which ensures good visibility (simple set-up for costsavings for commissioning, maintenance and operation)
− The temperature sensor with protective tube can be inserted into awelded thermowell via progressing ring fitting or seal fitting with soft
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gasket or can be directly mounted into the tank with no dead spacevia a common M0 adapter (exchangeability)
− Small range of parts in stock because the control monitors can becombined with the different temperature sensors (flexibility by meansof modular design saves cost).
− Sensors without mechanically moved parts such as magnetic Reedcontacts for low downtime because they are wear-free.
− For the control monitor analog output programmable to current orvoltage for integration with plc (guarantees reduced storage andsimple installation in existing systems)
− No recalibration because of high long-term stability (time saving formaintenance)
− No calibration equipment or other equipment for commissioningrequired (cost savings)
− Noise immunity by IP67 and robust field housing for minimum cost
5.2.6 Temperature sensors for machine tools (automotiveindustry)
For machine tools there are mainly two liquid circuits to be monitored:the hydraulic and cooling lubricant circuits.
Depending on how much the machine is stressed during the individualmachining operations different amounts of heat energy are generated inthe hydraulic system or the cooling lubricant. Since this allows forexample to determine overload of a machine part and to start cooling ofthe storage tank, a precise temperature monitoring is required.
Application example
For a hydraulic machine the temperature of the medium is controlled viathree switch points (TN 7430). With the switching output 1 themaximum and minimum temperatures are monitored and corrected, i.e.when the maximum setpoint is reached, the medium is cooled, when theminimum setpoint is reached cooling is turned off. The second switchingoutput is used to turn off the installation when a critical temperature isexceeded, i.e. in case of insufficient cooling capacity (see figure 2).
Advantages of ifm sensors for the customer
− Control monitor with two set and reset points each- for TN7430 andTR7430 for an accurate monitoring of different temperature stages(low-cost unit)
− Installation of the temperature sensors into thermowells viaprogressive ring fitting without problem at any requested installationdepth. DIN thermowells with inch thread can also be used. The sensorwith cable is adapted to the progressive ring fitting of a T-piece sothat within each hydraulic line the temperature can be measured(clear information about the whole system)
− Since the actual temperature sensor can be mounted separately fromthe control monitor via a cable connection as opposed to a contactthermometer or thermostat, the individual control monitors can bemounted side by side at a location which can be easily accessed by
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the operator. This provides good information on the current conditionof the machine. The LED display provides excellent visibility.
− In contrast to contact manometers there is no mechanical wear.− The temperature control is decentralised from the hydraulic and
cooling lubricant circuits: fewer inputs on the central plc needed (costsaving), which enables a simple setting and evaluation on site.
− For sensitive machining operations such as grinding spindle withhydrostatic circulated lubrication the temperature can be kept stablewithin a narrow range, which has a positive effect on themanufacturing accuracy (enhanced quality and cost savings).
− Individual units can be replaced for each other without the need ofcalibration (low downtime)
− Status indication for fault location on site (simple diagnosis of themachine, e.g. for faulty bearings and the resulting higher heatgeneration)
− Locking avoids tampering with the system (noise immunity)− High shock and vibration resistance in conjunction with a robust field
housing, chemical resistance to oil and cooling lubricants to ensure along life
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Technical glossaryThis glossary is not intended to be a comprehensive reference book. It isto help you to quickly find some information about basic terms. In thefuture additions will be made, so this is not the final version. Suggestionsas to which terms should be listed are welcome.
On the one hand, the glossary provides additional information byexplaining terms which were only briefly or not at all mentioned in themanual. On the other hand, terms which were discussed in detail in themanual are briefly explained again. The index helps to find these terms inthe manual. Terms which are specially important for ifm sensors areexplained in chapter 3.3, page 29.
Terms
Absolute accuracy This term describes how the measured value differs from a definedreference.
figure 61: Absolute accuracy
There is no deviation in the example in figure 61.
Accuracy Every measurement is error-prone. The accuracy is described by themaximum values of these errors or the error limits.
Basic values Pt temperature sensors have a change in resistance of 0.38 - 0.39 and3.8 - 3.9 Ω/°C for PT 1000 according to DIN EN 60751 (IST 90).
Characteristics (See temperature characteristics)
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Characteristics deviation It is defined for temperature sensors as the highest deviation of thecharacteristics from a straight line from the low to the high limit of theset point. For characteristics deviation see also DIN 16086, see alsoDeviation of the characteristics.
Current consumption Current for the internal supply of the temperature sensor. The valuespecified in the data sheet applies to the switched unit without load.
Current rating/continuous This is the current at which the ifm temperature sensor can becontinuously operated. The units are protected against short circuits,overload and reverse polarity. If there is a short circuit, the end transistoris blocked immediately. After the short circuit has been rectified the unitis ready again for operation.
Deviation of the characteristics The deviation of the characteristics is the deviation from a defined curvebased on measurements at increasing and decreasing values, includinghysteresis. In temperature measurement technology the defined curve isusually a straight line, which means a linear signal. There are differentdefinitions for the deviation of the characteristics which will not beexplained here in more detail. The following figure 62 shows what ismeant.
figure 62: Deviation of the characteristics
Drift, long-term drift In general, this is the change of the output value of a measuring systemwith time with a constant input value. A temperature drift or long-termdrift is a slow change of the output value which is not directly caused bya change of the input values of a component or in the circuit. Theshifting of the mechanical zero point of electromechanical and electronicmeasuring instruments can also be put down to this. This value is alsoimportant for temperature measuring instruments. It is specified as themaximum change of the value within a defined time interval. Pt-T havespecially good characteristics. <0.04 % in 5 years at an operatingtemperature of 200°C is stated as a typical value. The standards fordifferent measuring systems state exactly under which conditions the
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repeatability is defined thus trying to describe effects such as drift (seerepeatability)
EMC See standards and approvals at the end of the glossary.
Errors To be able to correctly assess the accuracy of a measurement it isimportant to distinguish the error types.
• Absolute error
It is 0.2 K for the ifm sensors and can be caused by a shifting of the zeropoint.The accuracy also depends on the resolution. The display of the ifmsensors can only indicate changes in value up to one digit. So it does notmake much sense to request a resolution greater than 0.5 K for thesignal processing. Conversely, the analog output has a better resolution.It is 0.125 K.
• Relative error
If for example a temperature drift of 4 K is measured and the absoluteerror is ± 0.2 K (as in the above example), the relative error is 10%. Butfor a temperature difference of 40 K it is only 1%.
The error which is indicated in % of the measuring range is different. It isfor example produced when the signal is converted into the indicatedoutput value. For the ifm sensors it is 0.5% of the measuring range.
This results in the above-mentioned errors of
± (0.2 K + 0.5% of the measuring range + 1 digit)
Heat conducting paste See thermowell.
Housing materials See materials
Hysteresis of the switching output The difference between the setpoint and reset point is called hysteresis ofthe switching output. The hysteresis of the temperature sensor can be setbetween 2% and 97% of the final value of the measuring range (cf.figure 29).
Long-term drift See drift.
Long-term stability Due to the chemical inertia and homogeneity of the used platinum thePt-T are the temperature sensors with the highest stability. Depending onthe operating conditions the typical Rt changes after 5 years of operationat 200°C are less than 0.04%.
Materials Housing materials, wetted parts. The materials of the temperaturesensors are adapted to the requirements of a wide range of industrialapplications. For critical applications the resistance of the materials mustbe checked.
Measuring error This describes the deviation of the unit from the actual value. See error.
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Measuring range The measuring range is the range of the measured quantity oftemperature for which the measurement deviations of a measuringinstrument are to be within the defined error limits. The limits of themeasuring range are the initial and final value. If only positive valuesgreater than zero are measured, e.g. pressure or length, this term meansthe same as value of measuring range VMR (see below). For temperaturesbetween -40 and +150°C the measuring range is 190.
Measuring stability This is the ability of a unit to retain its properties unchanged. They canchange within time (drift) or by other influences (e.g. temperature).
figure 63: Measuring stability
figure 63 shows an example of how the length of a measuring rodchanges as a result of heating.
Noise immunity To avoid malfunction as a result of too high a voltage spike which mayoccur in critical applications we recommend laying the cables of thetemperature sensors separately from the cables of interfering sources(e.g. motors, solenoid valves, etc.). In especially difficult cases screenedcables may be necessary. If in doubt, please contact our engineers.
Normally closed Normally closed means closed circuit. When the switching condition isnot met, the output is switched.
Normally open Normally open means open circuit. When the switching condition is met,the output is switched.
Operating temperature Temperature range where the temperature sensor functions safely.
Operating voltage The nominal operating voltage is a voltage value for which an electricalapparatus is rated. The operating voltage range is the range in which theunit functions safely. For DC units the minimum and maximum values,including residual ripple, must not be exceeded.
Output function, programmable The switching output can be programmed to be normally open ornormally closed via a button.
Plastics The resistance of plastics depends on the environmental conditions. Thisis why certain properties or the suitability for a certain application cannotbe guaranteed. Concerning the specific resistances we refer you to "PVC"and "PPU cable" as well as "Materials". The general notes given do notexempt you from running your own tests.
Platinum temperature sensors This is the designation of measuring resistor type sensor elements whichare used for temperature measurement. They are commonly known as Pt100, Pt 500 or Pt 1000 (in the manual abbreviated as Pt XY or Pt-T).
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They are temperature sensors whose function is based on thetemperature dependence of the electrical resistance, here it is the metalplatinum (Pt). For metal resistor temperature sensors the dependence ofthe charge carrier mobility on temperature is utilised. In this case itdecreases as the interaction between electrons and latticed componentsincreases with rising temperature so that the temperature coefficient ofthe resistor is positive (PTC).For the Pt 100 element the resistance value at 0°C is 100.000 Ω (IEC751), the value 100 is based on this. If at 0°C this resistance value is 500Ω or 1000 Ω, we speak of Pt 500 or Pt 1000. The higher the resistancevalue, the greater is the resistance change per temperature unit, and thusthe response sensitivity so that the resistance values of cables are lessimportant. However, intrinsic heating is higher.Since platinum guarantees a good repeatability of the measured values, itis preferred to the metals nickel or copper which could also be used. Thewide theoretical range of applications between -200°C and 1000°C is atpresent covered by ifm sensors from -40°C to 120°C, max. 150°Cdepending on the sensor version.Advantages of the platinum temperature sensors are:− Precise and long-term stable measured data over a wide temperature
range− Simple processing of the standardised and linear output signal− Simple replacement of elementary sensors
Power-on delay time The power-on delay time is the period which the sensor needs to producea correct switching signal after application of the operating voltage.During this time the output is inactive.
PPU cable Oil-resistant cable. Not resistant to hydrolysis, so not suitable forpermanent contact with water. In order to avoid breakage the cablesshould not be moved if the temperature falls below -10°C -> Plastics.
Protection rating IP65Complete protection against contact with live parts. Protection againstthe penetration of dust. Protection against water jets.IP67Complete protection against contact with live parts. Protection againstthe penetration of dust. Protection when immersed under definedconditions: 1 m depth of water for 30 minutes.
Protective insulation Protection is not only achieved through basic insulation but by means ofa double or enhanced insulation which meets the requirements of theprotective insulation.
Protection classification and rated impulse withstand voltageProtection class 1: units with protective wire connectionProtection class 2: units with protective insulationProtection class 3: Units for connection to protective low voltageVoltage supply to EN50178, PELV, SELV
Pt See platinum.
PVC cable Tried and tested standard cable. In order to avoid breakage the cablesshould not be moved if the temperature falls below -5°C. PVC cables are
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not suitable for continuous operation in oily environments. They are notresistant to ozone or ultra-violet light -> Plastics.
Range of destruction The range of destruction is the range in which changes to themeasurement characteristics of the sensor are permanent and mechanicaldestruction of the sensor is possible. It starts at the end of the measuringrange.
Reaction time See thermal response time.
Repeatability The possible deviation of the switch point for two successivemeasurements under identical conditions. This describes which deviationscan occur from a displayed value if after fluctuations the temperaturereturns to its normal value, in this example 30°C.
figure 64: Repeatability
The example shown in figure 64 is not realistic. For mechanical unitsgreater deviations must be expected.
Resolution This is the smallest step or the smallest change of the measured valuewhich can be sensed by the unit.
figure 65: Resolution
figure 65 shows two measuring rules with a different resolution.
Reverse polarity protection An internal protection prevents the temperature sensor from destructionin the case of reversed wire connections.
Rise time The time which the analog signal takes after an abrupt temperaturechange to rise from 10% to 90% of its final value which results from thetemperature change (see transient function in chapter 3.3, figure 19).
Selection According to DIN EN 60751 the Pt-T can be divided into the accuracytolerance classes A, B, 1/3 B. ifm uses sensors of the most common classB (in parts also A).
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Short-circuit protection The temperature sensors are protected against excessive current by apulsed short-circuit protection.
Signal processing The internal signal processing in the measuring device is increasinglydone digitally. Conversely, most outputs are still analog. But the share ofthe overall market is still low compared to mechanical temperatureswitches. There is no uniform bus system for temperature sensors ortemperature measuring instruments. The HART protocol is commonlyused for configuration, parameter setting, etc. It is also used for pressuresensors. In addition, manufacturer-specific protocols or for example aprotocol for RS232 are also used. The interest of users in processtechnology for example in remote parameter setting is great. Coupling toa field bus is of course possible but this can be expensive. Besides, thecommon bus systems are not rated for use in Ex areas.
Stability of the zero signal This can be a problem, specially for mechanical units.
F
figure 66: Stability of the zero signal
Switch point accuracy The possible deviation of the set value from the real value of the switchpoint.
System temperature The temperature of the measured medium to which the temperaturesensor is exposed.
Temperature characteristics If depending on the temperature the electrical resistance is indicated in acurve, this is the temperature characteristics. For the Pt-T this curveapproximates a straight line, specially in the range from 0 to 100° C.Also see: Deviation of the characteristics and 3.3.
Temperature coefficient Coefficient which describes the temperature dependence of a physical orchemical quantity. For measurement technology the temperaturecoefficient of the electrical resistance (TCR) is important. For platinumtemperature sensors the electrical resistance increases with risingtemperature. We therefore speak of a positive temperature coefficient ofthe platinum metal resistor (PTC). In mathematical terms this is theupward slope of the characteristics.The average temperature coefficient α defined in the standard (IEC 751)for the temperature range between 0 and 100°C is obtained if thedifference between the resistance values at 100°C and 0°C is formed and
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then divided by 100 and the resistance value at 0°C. The formula is asfollows:
α = (R100 - R0)/(100°C * R0)
For the Pt-T the average temperature coefficient α approximates the realtemperature coefficient. This coefficient indicates the upward slope of thecharacteristics, which for the Pt-T is more or less a straight line in thistemperature range.Also see: Deviation of the characteristics and 3.3.
Thermal response time The thermal response time is the time which a Pt-T needs to react to anabrupt temperature change with a change in resistance whichcorresponds to a certain percentage share of the temperature change.DIN EN 60751 recommends the times for a 50% and 90% change. T05
and T09 are specified in the data sheets for water and air flows of 0.4 and1.0 m/s. You get the same response times for different velocities of themedia because the thermal conductivity and the heat capacity aredifferent. For other media these times can be determined with the heattransfer coefficients to VDI/VDE 3522. The precise time characteristics aredescribed by the transient function (see figure 19 in 3.3).
Thermowell Whereas for pressure sensors the sensor element must be in directcontact with the medium, the temperature sensor can be inserted into awelded or screwed thermowell which ensures that no medium leaks intothe environment while the sensors are replaced. These thermowells canbe optimised to the requirements of the corresponding industry such ascorrosion resistance, hygienic design of the surface and materialcomposition, etc.To make sure that the medium temperature can pass from thethermowell to the sensor element they must be in good thermal contact.An air gap would impede the heat transfer. For heat air has an insulatingeffect (cf. flow sensors). To guarantee short reaction times under alloperating conditions as a result of optimised thermal conductivity a heatconducting paste must be used.
Tolerance classes The Pt-T have defined operating temperature ranges with a certaindeviation from the ideal characteristics. This is why accuracy toleranceclasses are defined. According to DIN EN 60751 the Pt-T used by ifmbelong to the common class B: ∆t = ±(0.3 + 0.005/t).
Value of measuring range The abbreviation VMR is frequently used. An example of linearmeasurement is to illustrate this.
figure 67: Value of measuring range VMR
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Two measuring instruments (measuring rods) are shown here with thesame accuracy and the same resolution but different VMR.
Vibration resistance The temperature sensors are tested according to DIN/IEC 68-2-6 in thefrequency range of 10 - 2000 Hz and are resistant to vibration up to20 g.
Voltage drop Voltage loss which occurs at the switching output of the temperaturesensor in the case of maximum load current.
Window adjustable The output function is activated if the system temperature is between theselected setpoint and reset point. These temperature sensors monitor arange where the values are ok.
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Standards and approvals Switches made by ifm electronic are developed, produced and tested inaccordance with the appropriate standards and regulations. Theycorrespond to the presently valid and applicable IEC publications, ENstandards or DIN VDE regulations, special country-specific regulations aswell as various customers' own specifications. For new developments,modifications and improvements of existing products, the latest draftstandards on a European and international basis are taken into account.Quality assurance and quality management of ifm electronic meet thepresent and future high international requirements. This qualityassurance system guarantees the development and production of units toa high quality level.
Electromagnetic compatibilityAccording to the EC guideline (89/336 EEC) on electromagneticcompatibility (short EMC guideline) electrical and electronic apparatus,plants, systems or components are required to work satisfactorily in theexisting electromagnetic environment. These requirements are specifiedin the standards and regulations referring to the units.
Radiation of interference EN 55011The units specified in the catalogue comply with class B.
Noise immunity IEC 1000-4-1/EN 61000-4-1Electromagnetic compatibility for industrial process measurement andcontrol equipment
IEC 1000-4-2/EN 61000-4-2Electrostatic discharge requirements
IEC 1000-4-3/EN 61000-4-3Radiated electromagnetic field requirements
IEC 1000-4-4/EN 61000-4-4Electrical fast transient requirements (burst)
IEC 1000-4-6/EN 61000-4-6Immunity to conducted disturbances induced by radio-frequency fields
Severity levels to EN 50082-2Generic standard Noise immunity
Quality to standards Quality assurance and quality management of ifm electronic meet thepresent and future high international requirements. This qualitymanagement system guarantees the development and production ofunits on a high quality level. At the same time we hereby declare theconformity of the units with the safety regulations of the EC low voltageguideline 73/23 EEC dated 19/02/1973. Because of the world-widedistribution of products and for the internationally active customer,country-specific approvals are available, if needed, and will be pursuedand achieved (e.g. for Canada, USA, Japan, Switzerland).
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Explanation production code
d:\dokumente und einstellungen\dezeyegu\eigene dateien\lokalab05-04\materiallevele\originale\prodcode-e.docThis copy was printed on 03.06.04 enclosure to EA SIT-015
The coding is indicated on the type and box labels of our products or on an alternative type oflabelling, e.g. 'direct laser labelling' as it is used with the units in modular technology.
The coding covers information about Legend 'production site'
production site production month special designation
(meaning registered in the production site)
production status
E ifm ecomatic, KressbronnK ifm prover, Kressbronn (from 1/3/2000)P (bought-in products)S ifm syntronT ifm Tettnang (parent plant)U ifm USA (efector inc.)W ifm SwedenF ifm France
Current production code:
Standard coding Direct laser labelling(conventional units) (modular units)
Example: SA8 made byifm Syntron inOctober (A) 1998
- no special designation -
Example: 9903 made in 1999,in March (03)
AA first production status (AA)
T AB in the parent plantifm Tettnang ;second prod. status (AB)
- no special designation -
Old coding (until September 1995)
spec.des.
prod. site(see
legend)
prod.month(hex.)1...9,A,B,C
Prod. year(last pos.)
prod. statusAA...ZZ spec.
des.prod. site
(see legend)
prod. month(dec.) 01...12
prod. year(last two pos.)
prod. statusAA...ZZ
spec.des.
prod year(last pos.)
prod. month(dec.) 01...12
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Type key
Pos. Designation Contents1 Sensing principle T = temperature sensor2 Display A = no display
B = LED bar displayM = sensor with process connectionN = numerical displayO = customer specific unitsP = EPS unitR = remote sensor with numerical displayS = sensor with cableT = sensor with socketY = special keyZ = special key
3 - = standardD = with diagnostic output
4-6 Length of sensing unit Length in mm (type TA, TN, TT)Cable length Cable length in mm (type TS)
7 Measuring unit C = °CF = °FK = combined °C and °F
8 Temperature range / B = -40°C up to 125°C / PT1000Measuring principle C = -40°C up to 150°C / 1000
D = control unit for PT100 / PT1000E = -40°C bis +300°CI = -40°C...+250°CL = special range (different ranges possible)
9 Type / B = cylindrical metal housing V2A; process connection V2Ahousing D = cylindrical metal housing V2A; process connection V4A
E = cylindrical metal housing V4A; process connection V4AK = cylindrical metal housing V4A; process connection V4A; cable
10 Type of thread D = cylindricalof the process connection M = metric thread
N = NPT threadP = PT thread (according to DIN 2999)R = pipe thread, internalS = saw toothed threadU = UNF thread
11-12 Thread size and diameter (M)xx = diameter in mm(N)14 = NPT thread 1/4"(P)38 = PT 3/8(R)01 = pipe thread 1"(R)14 = pipe thread 1/4"(R)12 = pipe thread 1/2"(R)34 = pipe thread 3/4"(S)30 = saw toothed thread S30x2(U) = UNF thread 7/16"(D)10 = 10mm diameter(D) 08 = 8mm diameter(D) 06 = 6mm diameter(D) 05 = 5mm diameter
13 Free
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20T N - 0 1 3 K B B R 1 2 - K F P K G / US
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14 Type of output A = analog output 4-20mAB = analog output 0-10VC = analog output 0-20mAD = analog output 1-10VF = windowH = hysteresis adjustableK = combined (analog 4-20 mA / binary)L = combined (analog 0-10 V / binary)M = combinedt (analog 4-20 mA or 0-10V / binary)Q = 2 x binaryR = 3 x binaryS = 4 x binary
15 Switching functionnktion - = without output functionF = programmable output functionS = normally openO = normally closed
16 Output B = semiconductor AC and AC/DCD = 3-wire (analog output)N = semiconductor output negative switchingP = semiconductor output positive switchingZ = 2-wire (analog output)
17 Short-circuit protection K = with short-circuit protectionO = without short-circuit protectionV = reverse polarity protection
18 Supply voltage A= AC/DC voltageG = DC voltageW = AC voltage
14-16 For units with ASI = AS-i protocolbus system CAN = CAN protocol
EPS = EPS protocolPRO = Profibus protocol
19 Slash20 Options US = with M12 connector
SS = with SS connectorLS = with LS connectorCSA = CSA approval3D = ATEX approval category 3DE = cell seal EPDMN = cell seal NBRP = cell seal PTFE; process connection seal FPM (VITON)V = cell seal FPM (Viton)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20T N - 0 1 3 K B B R 1 2 - K F P K G / US
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Index!
! .............................................................38, 48, 64
°
° C...................................................................14, 50° F ...................................................................15, 50° R.........................................................................16
2
2-wire circuitry ......................................................33
3
3A ........................................................................603-wire circuitry ......................................................33
4
4-wire circuitry ......................................................33
A
absolute accuracy..................................................82absolute error........................................................84absolute zero ..................................................14, 17accuracy................................................................82adapter .................................................................60adaption of the analog output ..............................47AEP.......................................................................48air becomes liquid .................................................17alcohol thermometer...............................................9analog output ...........................................47, 49, 70AOU .....................................................................49applications.........................................34, 35, 36, 73approvals ..............................................................91ASP.......................................................................48atoms ...................................................................12
B
basic unit ..............................................................40basic values.....................................................31, 82bimetal .............................................................9, 28block diagram .......................................................40boiling point .........................................................14Bunsen burner.......................................................17bus system ............................................................88
C
cable resistance .....................................................51cable sensor ..........................................................61CAL.......................................................................51calibration.......................................................37, 51calibration offset ...................................................52calibration reset.....................................................52Car........................................................................52Celsius...................................................................14characteristic curve................................................29characteristics..................................................82, 83characteristics of sensor...................................20, 21
chip ...................................................................... 37CIP........................................................................ 74coal fire ................................................................ 17coefficient............................................................. 31COF ...................................................................... 52cold ...................................................................... 18common thermowells ..................................... 60, 64compensation of the cable resistance .................... 40configuration ........................................................ 88configurator.......................................................... 59confirmation ................................................... 43, 54connecting cable................................................... 58connection by means of a cable ............................ 67contacts................................................................ 69containers............................................................... 6control monitor............................................... 57, 72conventional temperature sensors ......................... 71conventional thermowells ..................................... 67cooling ................................................................. 20correction value .................................................... 51current consumption....................................... 71, 83current output ...................................................... 49current rating.................................................. 71, 83
D
damping function ................................................. 54delay reset ............................................................ 52deviation of the characteristics .............................. 83diamonds burn ..................................................... 17digitally................................................................. 88DIN EN 60751....................................................... 89diode.................................................................... 36diS........................................................................ 49dIS........................................................................ 52display .................................................................. 41dr1 ....................................................................... 52drift ...................................................................... 83dS1....................................................................... 52
E
EF ......................................................................... 52EHEDG.................................................................. 60electrical arc.......................................................... 17electrical conductivity ................................ 22, 28, 51electrical contact................................................... 24electrical melting furnace ...................................... 17EMC ............................................................... 84, 91EN 60751 ............................................................. 89energy ............................................................ 12, 25engine block in the car.......................................... 17enhanced functions .............................................. 52Enter function....................................................... 43Err ........................................................................ 42error display.......................................................... 42errors.................................................................... 84expansion ............................... see thermal expansionextensive............................................................... 13
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F
Fahrenheit.............................................................15FAQ ......................................................................10fermentation control .............................................79fermentation process...............................................6filaments in bulbs..................................................17fixed hysteresis ......................................................44fixed window ........................................................47flexible connection ................................................58flush mounting .....................................................65Fnc........................................................................46Fno .......................................................................46food industry ........................................................17FOU1 ....................................................................52frequency measurement ........................................37function output.....................................................52
G
gasignition ......................................................................... 17
gas thermometers .................................................28
H
half-time ...............................................................32heat ......................................................................12heat conducting paste...........................................84heat engine...........................................................25heat exchanger .......................................................8heating ...........................................................12, 21Hi .........................................................................50Hnc.......................................................................45Hno ......................................................................45housing materials ..................................................69hydrogen boils ......................................................17hysteresis ..................................................44, 46, 84
I
I .........................................................................49IC sensor ...............................................................35IEC 56B .................................................................31IEC 751 ...........................................................31, 88ignition in the car engine.......................................17integrated control monitor ....................................55integrated unit ......................................................41intensive................................................................13iron
glowing ........................................................................ 17melting ......................................................................... 17
K
K .........................................................................14Kelvin....................................................................14kinetic energy........................................................12
L
length of the temperature probe .............................9lengths......................................................64, 65, 66liquid glass ............................................................17liquid-in-glass thermometer...................................28
Lo ......................................................................... 50loc ........................................................................ 52locking.................................................................. 52long-term drift ...................................................... 83long-term stability................................................. 84
M
M0 adapter..................................................... 60, 65M0 thermowells........................................ 64, 65, 67machine tools ................................................... 7, 80material ................................................................ 69materials............................................................... 84maximum hysteresis .............................................. 44maximum load...................................................... 71maximum temperature.......................................... 50measuring error .................................................... 84measuring principles ............................................. 32measuring range............................................. 85, 89measuring stability ................................................ 85mercury thermometer ............................................. 9microprocessor ..................................................... 40Min/Max ............................................................... 50minimum hysteresis............................................... 44minimum interval.................................................. 48minimum load ...................................................... 71minimum temperature .......................................... 50mode.................................................................... 41Mode function...................................................... 43modular.................................................................. 9modular design..................................................... 57modular system .................................................... 72molecular movement ............................................ 12molecules ............................................................. 12monitoring ............................................................. 9mounting kit......................................................... 58mounting set .................................................. 66, 72
N
noise immunity ..................................................... 85nominal value ................................................. 30, 31normal operation .................................................. 41normally closed............................................... 45, 85normally open................................................. 45, 85NTC .......................................................... 23, 30, 36
O
OL ........................................................................ 42operating temperature .......................................... 85operating voltage............................................ 71, 85oscillating circuit ................................................... 37OU 1 .................................................................... 45OU 2 .................................................................... 46output function .............................................. 70, 85overload ............................................................... 71overview ............................................................... 67
P
parameter setting.................................................. 88Peltier effect.......................................................... 26plastics.................................................................. 85
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platinum .........................................................30, 85power-on delay .....................................................71power-on delay time .............................................86PPU.......................................................................86precision .........................................................15, 48process connection................................................56process control........................................................9process engineering ................................................9progressive ring fitting...........................6, 58, 59, 64protection class .....................................................86Protection classification .........................................86protection rating ...................................................86protective insulation ..............................................86protective tube........................................................6Pt ...................................................................30, 86Pt 100.................................................30, 38, 72, 85Pt 1000...........................................9, 30, 38, 72, 85Pt 500.............................................................30, 85Pt XY.....................................................................30PTC .........................................23, 30, 33, 34, 36, 88Pt-T.................................................................30, 85PT-T ......................................................................31PVC.......................................................................86
Q
quality management .............................................91
R
r° C .......................................................................50r° F........................................................................50radiation ...............................................................28range of acceptable values ....................................46range of destruction..............................................87range of values......................................................54rated impulse withstand voltage............................86reaction time.........................................................87Réaumur ...............................................................16reference temperature ...........................................25repeatability ..........................................................87reset point ......................................................44, 45resistance ..............................................................28resistance of the cables..........................................33resolution............................................42, 47, 48, 87reverse polarity ......................................................71reverse polarity protection .....................................87rigid connection ..............................................57, 66rise time................................................................87rotated display ......................................................49rP 1 .....................................................................45rP 2.......................................................................45RUN......................................................................41RUN mode ............................................................41
S
SC 1......................................................................42SC 2......................................................................42sea water
melting ......................................................................... 17Seebeck effect .......................................................24Seger cone ............................................................27
selection ............................................................... 87semi-conductor sensors......................................... 36sensor in the medium ........................................... 18sequence ........................................................ 68, 69SET ....................................................................... 42SET mode ............................................................. 42setpoint .......................................................... 44, 45setting .................................................................. 42setting of the reset point....................................... 45setting range ........................................................ 48shock resistance .................................................... 69short-circuit protection.......................................... 88short-time heating systems.................................... 78SI ......................................................................... 15signal processing............................................. 40, 88Silicon................................................................... 36SP ......................................................................... 43SP 2 ...................................................................... 43specific heat.......................................................... 18speed.................................................................... 12stability of the zero signal...................................... 88standards.............................................................. 91state quantity........................................................ 13stratosphere.......................................................... 17surface of the sun ................................................. 17switch point.......................................................... 43switch point accuracy............................................ 88system temperature .............................................. 88
T
t0.5 ...................................................................... 32t0.9 ...................................................................... 32T05 ........................................................................ 89T09 ........................................................................ 89tanks ...................................................................... 6tasks ....................................................................... 9temperature.............................................. 12, 22, 23temperature coefficient ................................... 37, 88temperature correction value................................. 51temperature difference.......................................... 24temperature differences ........................................ 15temperature equilibrium ....................................... 19temperature measurement ........................ 12, 26, 28temperature measurement procedures .................. 27temperature measurement technology .................. 27temperature of the sensor ..................................... 20temperature range ............................................ 9, 54temperature sensor with protective tube ............... 58temperature sensors.................................... 5, 18, 31thermal capacity ............................................. 18, 20thermal conductivity ................................. 18, 20, 22thermal expansion................................................. 28thermal response time........................................... 89thermistor............................................................. 31thermistors ........................................................... 34thermocolours ...................................................... 27thermoelement ............................................... 25, 36thermoelements.............................................. 24, 28thermolubricant .......................................... 6, 20, 26thermovoltage ...................................................... 24thermowell ....................................................... 6, 89
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thermowells ..........................................................56thin film technology ..............................................38time behaviour ......................................................31TN...................................................................55, 62tolerance classes..............................................31, 89TR .............................................................56, 63, 72transient function..................................................31transistor...............................................................36Tri-Clamp ..............................................................65TS ...................................................................64, 72TT .........................................................................72
U
U 49UL.........................................................................42UnI .......................................................................52unit.......................................................................52units .....................................................................14unlocking..............................................................52using the Set button..............................................44
V
value of measuring range...................................... 89vapour in locomotives ........................................... 17Varivent ................................................................ 65VDI/VDE 3522....................................................... 89vibration resistance ......................................... 69, 90VMR ............................................................... 85, 89voltage drop ......................................................... 90voltage output ...................................................... 49volume ................................................................. 28
W
warm.................................................................... 18washing systems ................................................... 77water
melting .........................................................................17window .......................................................... 46, 90wood fire.............................................................. 17
Y
yeast pre-enrichment ............................................ 76