Module 5

Data acquisition, data manipulation, data presentation, Design of experimental set-ups, selection of instruments, design of experiments

Quadrant 2: List of animations/Videos:

1. See how to measure rotation speed revolutions per minute (RPM) and learn about some of the common rotational sensors. Sensors include variable reluctance sensor, hall effect sensors, magnetic and optical sensors http://www.youtube.com/watch?v=PS3K-whRVY0&list=PL1C8E4DA2B8D1F309&index=1

2. This video tutorial shows how to take basic data acquisition measurements using LabView and a National InstrumentsDAQ-6009. http://www.youtube.com/watch?v=GBhJk5Tnshc

3. View a walk-through of LabVIEW system design tools, including the graphical development environment, to see how it can increase your productivity.

http://zone.ni.com/wv/app/doc/p/id/wv-1344

4. NPTEL Video lecture on filters, lecture 37:filters

http://freevideolectures.com/Course/2261/Basic-Electronics-and-Lab/37

5. Today's Electronics 101 video discusses the active filter, its basic design, and how it differs from the passive filter

http://www.youtube.com/watch?v=Wa_1O6RWRho

6. Lecture Series on Digital Signal Processing by Prof.S. C Dutta Roy, Department of Electrical Engineering, IIT Delhi, digital filter design, lecture 39

http://www.youtube.com/watch?v=nsK7mmRSTDY

7. NPTEL video on data acquisition system by IIT Kharagpur

freevideolectures.com/Course/2345/Industrial-Automation-and-Control/10

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8. Typical basic SCADA animation is shown

http://en.wikipedia.org/wiki/SCADA

Illustrations:

1. Image of a DAQ system is provided http://sine.ni.com/cs/app/doc/p/id/cs-11398

2. DAQ system components are illustrated http://www.testbench.co.in/daq-systems.html

3. DAQ system development with MATLAB http://www.mathworks.in/discovery/data-acquisition-system.html

List of questions (FAQ):

1. What is data transmission? 2. Mention the different types of data acquisition systems 3. What is signal conditioning? 4. What do you understand by the following terms as applied to instrumentation or

measurement system? 1. Detector-transducer stage, 2. Signal conditioning stage 5. What are the limitations of mechanical amplification? 6. State the advantages of electrical signal conditioning. 7. Discuss the following functions of signal conditioning tools:

a. Amplification b. Impedance matching c. Data transmission d. Modification or modulation e. Data processing

8. Discuss briefly the following: a. Mechanical amplifiers b. Fluid amplifiers c. Electrical and electronic amplifiers

9. Explain briefly the mechanical signal conditioning with examples. 10. List some of the manipulations involved in electronic or electrical signal conditioning. 11. What is signal conditioning and why is it required?

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12. With a schematic diagram discuss the functioning of an instrumentation amplifier 13. Illustrate the following :

a. Basic operational amplifier circuit b. Summing amplifier using an operational amplifier c. Differential amplifier d. Integrating amplifier e. Differentiating amplifier f. Logarithmic amplifier g. A circuit for taking the ratio of two signals h. RC notch filter i. Low pass filter j. High pass filter

14. What do you mean by data acquisition system? What are its major parts? What are the available?

15. What is analog data acquisition? 16. What is digital data acquisition? 17. What are uses of data acquisition systems? 18. List the main components of a data acquisition system 19. What are filters? How they are classified?

Quadrant 3 Wiki links/reference links/courses from other university websites

1. Pressure calibration is explained http://www.acin.nl/EN/PDF/Calibration/instruments/Betz.pdf (Betz micromanometer)

2. Introduction to data acquisition, various terms related to data acquisition and different types of data acquisition systems are explained http://www.omega.com/prodinfo/dataacquisition.html

3. Various data loggers are shown http://www.omega.com/guides/loggers.html

4. Flow and level data loggers are shown http://www.omega.com/subsection/ph-flow-level-data-loggers.html

5. Data acquisition and analysis software are listed http://www.omega.com/toc_asp/subsectionSC.asp?subsection=B&book=das&all=1

6. Basics of signal conditioning are presented http://en.wikipedia.org/wiki/Signal_conditioning

7. Data logging thermometers – product details are available

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http://www.google.co.in/images?hl=en-IN&q=data+logging+thermometer&gbv=2&sa=X&oi=image_result_group&ei=O1jvUarRDs39rAf4m4CgDA&ved=0CCsQsAQ

8. DAQ hard ware and software are explained http://en.wikipedia.org/wiki/Data_acquisition

9. Basics of electronic filters are discussed http://en.wikipedia.org/wiki/Electronic_filter

10. Basic introduction to filters _ texas instruments http://www.ti.com/lit/an/snoa224a/snoa224a.pdf

11. Data visualization basics are discussed http://en.wikipedia.org/wiki/Data_visualization

12. Images of data presentation are presented http://www.google.co.in/images?hl=en-IN&q=data+presentation&gbv=2&sa=X&oi=image_result_group&ei=Enf7Uau7J8ymrQeVlIHADg&ved=0CCMQsAQ

13. Effective presentation of data, usually in the form of Figures or Tables, are shown http://www.stars.rdg.ac.uk/data.html

14. Quantitative data presentation are highlighted http://www.perceptualedge.com/blog/?p=1668

15. Data acquisition techniques are presented http://www.mstarlabs.com/daq.html

16. Fundamentals of data acquisition are presented- how does a data acquisition system work? http://www.vtiinstruments.com/Why-Use-Data-Acquisition.aspx

17. SCADA details are presented http://en.wikipedia.org/wiki/SCADA

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Quadrant 4

Case study: Data acquisition in a creep measurement set up:

Fig. 1 A creep measurement set up – lever arm type. A heating furnace is attached for conducting accelerated creep tests.

Fig. 2 A three zone heating furnace is integrated to the creep setup. Appropriate thermocouples are used to measure the temperature inside the furnace.

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Fig. 3 Proximity switch to sense the level of the lever. If the level of lever changes due to elongation of the specimen, the proximity sensor senses this and a signal is sent to the controller. Then, the controller sends a signal to draw- head to adjust the level of lever.

Fig. 4 Draw- head which adjusts the level of lever.

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Fig. 5 Controller (PID) of the creep setup which controls temperature of the furnace.

Fig. 6 An LVDT is used to measure the elongation of the creep test specimen. Range is ± 20 mm and LC is 0.001 mm

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Fig. 7 Eurotherm data logger is used to acquire the thermocouple output and LVDT out put. Digital display of the temperature of 3 zones can be seen in the above picture. Bridge software is used for data acquisition.

Fig. 8 In the computer screen a window appears to select the creep measurement option.

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Fig. 9 A power cut off switch (limit switch ) is used to cut off power to the furnace when the test specimen breaks.

Fig. 10 Creep test aluminum specimen after fracture inside the furnace.

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Multiple choice questions (Choose the correct answer)

1. Which is the most desirable feature in an electronic amplifier? a. High output impedance b. Low input impedance c. Good frequency response d. All of the above

2. Charge amplifiers are normally used in order to amplify the output signals of a. Inductive transducers b. Capacitive transducers c. Resistive transducers d. Piezo-electric and capacitive transducers

3. Filters that transmit all frequencies below a defined cut-off frequency are known as a. Low-pass filters b. High-pass filters c. Band-pass filters d. Any of the above

4. Excitation and amplification systems are required for a. Active transducers only b. Passive transducers only c. Both active and passive transducers d. Both passive and output transducers

5. A dc amplifier a. Needs to have a balanced differential inputs with a high common mode rejection

ratio to give very good thermal and long term stability b. Easy to calibrate at low frequencies and has ability to recover from overload

conditions c. Is immune to drift and low frequency spurious signals come out as data

information d. All of the above

6. The output from frequency-modulation systems is a. ac voltage b. dc voltage c. ac and dc voltage d. any of the above

7. The data transmission systems with synchro employs ----- telemetering to convey the requisite information

a. Frequency b. Position

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c. Impulses d. Voltage

8. When using ac signal conditioning system for capacitive transducers , the carrier frequencies a. Range between 50 Hz and 20 kHz b. Should be of the order of 0.5 MHz c. Should be of the order to 20 MHz d. None of these

9. The properties of an ideal Op-amp are a. It should have zero input impedance b. It should have high input impedance c. It should have a zero open loop gain d. None of these

Answer table

1. c 2. d 3. a 4. d 5. d 6. b 7. b 8. b 9. b

Fill in the blanks with appropriate word/s

10. The first stage of the instrumentation (or measurement system) which detects the measurand is termed as ---- stage

11. Transmission of signal from one location to another location without changing the contents of the information is called -----

12. Amplifier is a device which is used to ------- the weak signal 13. An -----------is a linear IC that has a very high voltage gain, a high input impedance and a

low voltage output impedance 14. Op-amps are linear ICs that work on relatively------ supply voltage 15. Buffer amplifier converts a voltage at high impedance to the same voltage at -----

impedance 16. ---- is an electronic circuit which can pass or stop a particular band of frequencies

through it 17. A charge amplifier is used with-------- transducers .

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18. Filtering is a process of --------- unwanted components of a measured signal while permitting the required components to pass .

19. A band-pass filter is obtained by ----- a low-pass and a high-pass filter .

Answer table 10. Detector-transducer stage 11. Data transmission 12. Increase or augment 13. Op-amp 14. Low 15. Low 16. Filter 17. Piezoelectric 18. Removing 19. cascading

True/false/yes/no

20. The first stage of the instrumentation or measurement system which detects the measurand is termed as detector-transducer stage (yes)

21. Amplification means enhancement of the signal level which is given in the low level range (yes)

22. Modulation means to change the form of signal (yes) 23. DC amplifier is easy to calibrate at low frequencies (Yes) 24. The major disadvantage of a DC amplifier is that it suffers from the problem of drift (yes) 25. The ratio of output signal to input signal for an amplifier is termed as gain or

amplification (yes) 26. The DC amplifiers are capable of amplifying static, slowly changing or rapid-repetitive

input signals (yes) Answer table For all questions (20 to 26), answer is yes

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Assignment questions and solutions

1. List some of the manipulations involved in electronic or electrical signal

conditioning. Ans: Following are some of the manipulations that are involved in signal conditioning: 1. Amplification- increase voltage level 2. Amplification after manipulation – increase voltage level after some algebraic

manipulation 3. Analog to digital conversion – convert analog signal to digital signal readable by a

computer 4. Communication with a computer – data storage 5. Manipulation using software and presentation of data in a user friendly form –uses

softwares such as LABVIEW, MATLAB, EXCEL and others 6.

2. Explain briefly a data acquisition system. Ans: A data acquisition system is explained below: Collecting data is a tedious and time-consuming component in most of the research projects or experiments. Although necessary, it is a task that we would rather not spend much time on. Data acquisition and control system allows us to automate the long hours of routine data collection, freeing us for tasks that can make a difference Data acquisition (DAQ) is a process of measuring an electrical or physical phenomenon such as voltage, current, temperature, pressure, flow rate, speed, sound, etc. using a computer. It consists of sensors, DAQ measurement hardware and a computer with programmable software. Each of these are explained below:

a. Sensor: It measures a physical phenomenon, such as the pressure in a chamber, force applied on a machine member, heat intensity, etc. a sensor also called a transducer converts a physical phenomenon into a measurable electrical signal. Depending on the sensor used, its electrical output cam be a voltage, current, resistance, or another electrical attribute that varies with time. Some sensors may need additional circuitry and components to properly produce a signal that can accurately and safely be read by the DAQ device.

b. DAQ device: It acts as an interface between a computer and signals from the outside world. It primarily works as a device that digitizes incoming analog signals so that a computer can interpret them. The three important

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components of a DAQ device used for measuring a signal are the signal conditioning circuitry, ADC, and computer bus.

c. Computer: A computer with programmable software control the operation of the DAQ device and is used for processing, visualizing and storing the measurand. Driver and application software are needed to control the operation.

d. Bus: It is the communication interface between the DAQ device and computer for passing instructions and data. Common computer buses used are USB, PCI, PCI express, Ethernet and 802.11 Wi-Fi.

3. What is a data logger? Ans: A data logger is a device used to store data. It includes many data acquisition devices such as plug-in boards or serial communication systems which use a computer as a real time data recording system. Data logging is the measuring and recording of physical or electrical parameters over a period of time. A wide range of devices can measure and log data from basic, single measurement devices to complex systems with built-in analysis functions and displays. Data loggers can measure different types of signals and sensors. Data loggers are used in an array of applications such as in vehicle data logging, environmental monitoring, structural health monitoring, and machine condition monitoring. Common measurements include temperature, strain, current, pressure, voltage, force and acceleration.

4. What are the main applications of data acquisition system? Ans: The main applications of data acquisition system are given below:

1. Temperature monitoring system 2. Multi point weighing scales 3. Pressure monitoring 4. Flow monitoring 5. Versatile automobile seat tester 6. Automobile crash testing 7. Intelligent data selection

5. Present an overview of data acquisition and control system

A data acquisition and control system turns physical phenomena (temperature, pressure, flow, position, speed) into data that can be stored, analyzed, displayed, or acted on. DAC system has the following components for its functioning. Transducers:

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Transducers are devices that transform physical phenomena (temperature, pressure, flow, strain, position, speed, pH, acceleration, etc.) into electrical parameters (voltage, current, resistance, pulses, etc.) that can be measured by instrumentation Signal Conditioning: Signal conditioning is used in data acquisition systems to put the analog or digital signal into a form that can be accurately measured by the equipment. The signal may be too weak, too strong, too noisy, or in the wrong shape to be measured accurately. The conditioning may be accomplished on the transducer end of the wiring or in the measurement hardware. Switching: A switch is a mechanical or electronic device that is used to make or break the connections in an electrical circuit. Switches can be used to route the output signals from multiple transducers to one measurement instrument (scanning). Switches are also used as control devices to switch power to external fans, heaters, pumps, lights, and motors. Switches come in a variety of forms. A relay is an electrically-controlled device where a mechanical part moves to make or break the circuit. Reed relays and armature relays are two examples. A solid state switch is an electronic device that makes or breaks the circuit. Field Effect Transistor (FET) switches are examples of solid state switches. In general, solid state switches will outlast relays but can only switch low voltages. The following table summarizes some common switch types. Scanning: Multiplexers are electronic devices that are used to switch multiple channels to a single measurement instrument, one at a time. They operate much the same way as a television set, although several channels are available, only one channel is viewed at a time. Multiplexers are available in one-wire, two-wire, three-wire and even four-wire varieties, each with its own special usage. One-wire (sometimes called single-ended) multiplexers are used in applications where the measurement instrument is close to the transducers and a common ground is practical. Two-wire (differential) multiplexers are the most common type and are used with instruments that have a differential (high and low) input.

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Three-wire (guarded) multiplexers are used with high-end, guarded voltmeters for the best accuracy in analog measurements (see the measurement hardware section on A/D converters). Four-wire multiplexers are used in making four-wire measurements on transducers such as RTDs (see Appendix C) that require a current source. Some A/D converter cards come with a multiplexer on the card. In cardcage products, the multiplexers are generally on a separate card from the A/D converter. In this way, several multiplexers can be tied to one A/D converter. Some multiplexers require the user to solder wires to the card while others supply screw-down terminals. For convenience, some cardcage multiplexers supply a separate terminal block. Wires from the transducers are attached to the terminal block without removing the multiplexer from the cardcage. The terminal block simply attaches to the end of the multiplexer card. Control switching: Switching can also be used to supply power to external fans, pumps, motors, or lights by completing a circuit. Power is normally supplied outside the DAC system. The switch card acts much like a light switch, turning power on or off to the device. In some cases, the DAC switch card supplies a small voltage signal to a larger external relay which in turn supplies the power to the device.

6. What are filters? How they are classified?

Ans: Time varying signals commonly consist of a combination of many components or harmonics. In addition to this, noise is often picked up, there by resulting in distortion and masking of the true signal. It is usually possible to selectively filter out some or all the unwanted signals using appropriate circuitry. Filtering is the process of attenuating unwanted components of a measurand while permitting the desired components to pass. Filters are classified into

1. Low-pass filters 2. High-pass filters 3. Band-pass filters 4. Band-rejection filters

7. What are the limitations of mechanical systems as signal conditioning devices?

Ans: Input signals are often converted to mechanical displacement by detector transducers. The displacement is then fed to a secondary transducer, which converts the input into a form, often electrical, which is easily processed by the intermediate

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stage. Occasionally, mechanical displacement is fed to intermediate mechanical elements in the form of links, gearing, cams, etc. Such mechanical elements present design problems when dynamic inputs are handled. The limitations of mechanical systems, as signal conditioners are presented below: 1. Poor amplification 2. Lack of kinematic linearity 3. A small frictional force in the mechanism may return back to the input as a

magnified load 4. Inertial forces in the system may also return back to the input as a magnified load 5. Backlash and elastic deformation normally cause a lost-motion at the output equal

to the product of backlash or deformation and the amplification between the source and the output.

6. Variation of tolerances on dimensions may result in error at the output 7. Thermal distortion cause changes in dimensions and physical properties (both

elastic and electrical), resulting in zero shift and scaling error. Electrical and electronic signal conditioning systems are not affected to a great extent by the above factors.

Self answered questions and answers:

1. What are data loggers and data acquisition boards ?

Ans: Please visit web resource nptel.iitm.ac.in/courses/IIT-MADRAS/Mechanical _Measurements (module 5)(Fig. 20)

2. Illustrate the following :

a. Basic operational amplifier circuit b. Summing amplifier using an operational amplifier c. Differential amplifier d. Integrating amplifier e. Differentiating amplifier f. Logarithmic amplifier g. A circuit for taking the ratio of two signals h. RC notch filter i. Low pass filter j. High pass filter

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Ans: Please visit web resource nptel.iitm.ac.in/courses/IIT-MADRAS/Mechanical _Measurements (module 5)

3. Explain how thermocouples are calibrated? Ans: Please visit web resource nptel.iitm.ac.in/courses/IIT-MADRAS/Mechanical _Measurements (module 5)(figures 21 to 26)

4. Present a few examples of measuring instruments using purely mechanical signal conditioning. Ans: Please visit web resource nptel.iitm.ac.in/courses/IIT-MADRAS/Mechanical _Measurements (module 5)(figures 2 and 3)

5. Present a schematic of a general instrument Ans: Please visit web resource nptel.iitm.ac.in/courses/IIT-MADRAS/Mechanical _Measurements (module 5)(figures 19)

Test your skills/knowledge:

1. Visit the experimental setups available in the various laboratories of your institute and identify the various signals measured and also identify the sensors integrated.

2. Collect the details of data acquisition system used in the above experimental setups. 3. Learn how to select the sensors for different applications. 4. Learn the data presentation methods used in the above measurement systems. 5. Visit the IC engine laboratory of your institute, and study the type of dynamometers

used to measure the performance of engines. 6. The temperature range of the heating furnace (in the above case study) is 50 to 1100o C.

Suggest suitable thermocouples for this temperature range. 7. Learn the methods of eliminating noise from the signals. 8. Explain the methods of reducing noise pickup in the data acquisition systems.

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