fg05w2 - introduction to temperature measurement .pdf

7/29/2019 FG05W2 - Introduction to Temperature Measurement .pdf

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Introduction to TemperatureMeasurement

FG05W2 Version 1.3 2010


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Seminar Logistics

Seminar materials Downloadable presentation

Question and Answer session (audio and email)

Survey

Earn 1.5 Professional Development Hours (PDH)

Seminar length

90 minute total presentation

Three approximately 20 minute instructional presentations

Three approximately 10 minute question and answer sessions

4

Audio Instructions

Please note the following during the seminar:

As a participant, you are in a listen-only mode.

You may ask questions via the internet, using yourkeyboard, at any time during the presentation.

However, the presenter may decide to wait to answeryour question until the next Q&A Session.

If you have audio difficulties, press *0.


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Audio Instructions for Q & A Sessions

Questions may be asked via your telephone line. Press the *1 key on your telephone key-pad.

If there are no other callers on the line, the operator willannounce your name and affiliation to the audience andthen ask for your question.

If other participants are asking questions, you will beplaced into a queue until you are first in line.

While in the queue, you will be in a listen-only mode untilthe operator indicates that your phone has beenactivated. The operator will announce your name and

affiliation and then ask for your question.

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Introduction of the Presenter

ISA Presenter

Larry Thompson, CAP

ISA Adjunct instructor since 1984. B.A.A.S Tarleton StateUniversity. Instructor for Texas State Technical College inInstrumentation (1977-1979), Computer Networking and

System Administration (1996-1999), E-Commerce Technology(1999-2003). CCST Certificate, FCC Radiotelephone License

(General, formerly First Class). Served 20 years USAFprimarily in Electronic Encryption Systems. Owned and

managed own services business since 1979.

Designed, developed, taught and maintained industrialcontrols in many varied applications.

Author of ISA books: Industrial Data Communications and

Basic Electrics/Electronics for Control


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Goals of this Session

Discuss the measurement principles, instrumenttechnologies, and applications to process conditions fortemperature measurement

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Section 1: Intro-Temperature Measurement

Principles Classification of Thermometers Temperature Scales Liquid Filled Systems Vapor Filled Systems Bimetallic elements


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Room Heating Example

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Room Temperature Measurement

Where do you mount thermostat?

What kind of measuring device?

What temperature are you measuring?

At what temperature does it turn the furnace on?

At what temperature does it turn the furnace off?

What causes the room temperature to vary?

What accuracy is required of this measurement?

Is reliability a concern?


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Temperature Measurement

Measurement of heat energy of a substance May be measured by contact

May be measured by radiation

Is a key process measurement

Characteristics of material change through temperature

Density changes through temperature change

Three states of matter are dependent upon (among other things)

temperature (solid, liquid, gas)

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Classification of Temperature Devices Classified as to absolute or temperature sensors

Classified as to mechanical or electrical

Classified by construction


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Temperature Scales

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Basic Liquid in Glass Thermometer


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Types of Liquid in Glass Thermometers

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Liquid Filled System Thermometer

Completely filled with Mercury


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Volatile Liquid Filled System Thermometer

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Comparison of Filled Systems

RANGE

ADVANTAGES

LIMITATIONS

LIQUID-FILLED VAPOR GAS-FILLED

Lowon-offdifferential,fast response,small bulb size

Insensitiveto ambienttemperaturechanges

Insensitiveto ambienttemperaturechanges

Requiresambientcompensation

Largebulbrequired,slowresponse

Large bulbrequired,slowresponse

-150 TO 1200 Fo

-100 TO 550 Fo

-100 TO 1500 Fo

(-101.1 to 648.9C) (-73.3 to 287 C) (-73.3 to 815.6 C)


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Bimetallic Thermometers

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Other Bimetallic Applications

On-Off Switch (coffee maker)

Thermostat (continuous)

Circuit Breakers (Low voltage)

Motor Overloads

Directional Signals

Others?


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Considerations

Bimetallics are basically on-off No way to easily transmit a continuous signal

Filled systems; while analog and have ability to transmit,are slow

Liquid in Glass Thermometers are only as accurate astheir insertion level

All filled systems, liquid in glass thermometers, and to anextent; bimetallic devices do not have an exceptionallyhigh range or large span, nor do they function well belowa determined temperature.

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Review of Key Points

Principles

Classification of Thermometers

Temperature Scales

Liquid Filled Systems

Vapor Filled Systems

Bimetallic elements


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Live Question and Answer Session

During Q&A, questions may be asked via your telephone line.

Press the *1 key on your telephone key-pad.

If there are no other callers on the line, the operator willannounce your name and affiliation to the audience and thenask for your question.

If other participants are asking questions, you will be placedinto a queue until you are first in line.

While in the queue, you will be in a listen-only mode until theoperator indicates that your phone has been activated. The

operator will announce your name and affiliation and then askfor your question.

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Section 2: RTDs and Thermistors


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Basic RTD

RESISTANCEELEMENT

PLATINUMLEADS

RTD IN A CUTAWAY VIEW SHOWING MEASURING ELEMENT

Basic RTD Circuit (2 Wire)


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3 Wire Circuit

4 - Wire RTD


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RTD Construction

PARTIALLY SUPPORTED RTD

PLATINUM WINDING

PLATINUM LEADS

CERAMIC BODY

BIRD CAGE RTD

PLATINUM ELEMENT

INSULATOR DISC

PLATINUM LEADS

GLASS BODY

PLATINUM COIL WOUND ON GLASS FORMER

FULLY SUPPORTED RTD

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RTD with ceramic body


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Sheathed RTD

METAL SHEATH

LEAD WIRES

MANDREL

(WITH PLATINUM ELEMENT)

FILLER(POWDER

OR CEMENT)

Smart RTDs


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RTD Considerations

Very stable, can have less than 1C drift over 5 years *

Most linear of temperature sensors

Does not require a cold junction reference

Does require lead resistance compensation

Temperatures from -200to 650C commonly available

Industry typical is 385 or 392 Platinum, 100 @ 0C

385 refers to 0.00385 Ohms/Ohm/Deg C

392 refers to 0.00392 Ohms/Ohm/Deg C

There is also a 0.003902 Ohms/Ohm/Deg C

* Dependent upon type

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Thermistors

Designer resistor

Electrical resistance of material varies greatly withtemperature

Limited spans, low cost

High accuracy & stability

Limited to low-medium temps

Typically resistance decreases as temperature increases

3% to 5% per F (5% to 9% per C) Can be had with either positive or negative temperature

coefficient.

May be had in a variety of shapes and forms


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Thermistor illustrated

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Basic RTD

2-Wire RTD

3- Wire RTD

4-Wire RTD

Sheathed RTD

RTD Considerations

Thermistors


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Section 3: Thermocouples

Basic Thermocouple Principles

Thermocouple Materials

Thermocouple Extension Wire

Thermocouple Construction and Assemblies

Thermocouple Considerations

Thermocouple Loop Calibration


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Basic Thermocouple

MEASURING

JUNCTION

T2T1

REFERENCE

JUNCTION

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Reference Junction


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Modern Ice Point

THERMOCOUPLE

MEASURING

JUNCTION

INSTRUMENT

REFERENCE

JUNCTION

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Standard Thermocouple Materials

ISA

DESIGNATION

E

J

K

B Platinum

30% Rhodium/

Platinum

6% Rhodium

0 TO1820 C Inert or Oxidizing Easily contaminated,

use in non-metallic,

silica-freeprotecting

tube.

WIRE

MATERIALS

RECOMMENDED

ATMOSPHEREFEATURES

Nickel

10% Chromium/

Copper-Nickel

Iron/Copper-Nickel -210 to760 C Vacuum, I nert,

Oxidizing,

or Reducing

May rust or become

brittle in sub-zero

temperatures

Nickel

10% Chromium/

Nickel

5% Aluminum

and/ or Silicon

-270 to 1372 C Inert or Oxidizing Most linear of all

thermocouples. Short

life in marginally oxid-

zing atmospheres.

-270 to 1000 C Vacuum, Inert,

or Oxidizing

Highest EMF output,

larger drift than other

base-metal thermo-

couples

NOMINAL

TEMP. RANGE C

(32 to 3308 F)

(-454 to 1832 F)

(-346 to 1400 F)

(-454 to 2501.6 F)


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Standard Thermocouple Materials (contd)

ISADESIGNATION WIREMATERIALS RECOMMENDEDATMOSPHERE FEATURESNOMINALTEMP. RANGE C

R

S

Platinum13% Rhodium/Platinum

Platinum10% Rhodium/Platinum

Copper/Copper Nickel

Tungsten/Tungsten-26% Rhenium

Tungsten6% Rhenium/Tungsten26% Rhenium

-50 to 1768 C

-50 to 1768 C

-270to 400 C

-18 to 2315 C

-18 to 2315 C

Inert or Oxidizing

Inert or Oxidizing

Vacuum, InertOxidizing orReducing

Inert or Vacuum

Inert or Vacuum

Good linearity at hightemperatures, smallsize, fast response,easily contaminated,use in protecting tube.

Same as Type R

Good for sub-zero usebecause of superiorresistance to corrosionfrom moisture, limitedtemp. range.

Good linearity at hightemperatures, brittle,hard to handle.

Good linearity at hightemperatures,slightly less brittle,than above.

(-58 to 3214 F)

(-58 to 3214.8 F)

(-454 to 752 F)

(-.4 to 4199 F)

(-.4 to 4199 F)

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Standard Thermocouple Extension Leads


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Bare Wire Thermocouple Insulation Types

Typical Thermocouple Assembly


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Thermocouples drift (depending on type) from 2to 5C in thesame direction annually.

Can measure the highest temperatures of any contact sensor

Can measure the lowest temperatures of any contact sensor

Have more errors in selection, installation, maintenance, andcalibration then other sensors

Are relatively linear over a portion of their range

They will burn open


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Basic Thermocouple Principles Thermocouple Materials

Thermocouple Extension Wire

Thermocouple Construction and Assemblies



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Related ISA Courses

FG07 Introduction to Industrial Automation and Control

TC05 Tuning Control Loops

TS00 CCST Review Course

All ISA courses are available any time as on-site training

For more information: www.isa.org/training

or (919) 549-8411


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ISA Certifications

Certified Automation Professionals (CAP ) www.isa.org/CAP

Certified Control Systems Technician (CCST)

www.isa.org/CCST

Please visit us online for more information on any ofthese programs, or call (919) 549-8411.

Please take our Web Seminar Survey

via ZoomerangThe seminar survey was sent to you via email

during the seminar. Please do not forget tocomplete the Zoomerang survey.


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Conclusion

This is the end of:

Introduction to Temperature Measurement

fg05w2 - introduction to temperature measurement .pdf

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