Department of Electrical and Department of Electr Engineering

EE2201-Measurement & Instrumentation For Third semester EEE Two marks questions with answers, Possible 16 mark questions with key, Previous year Anna university question papers solved. Mr.P.Elamurugan M.E.(PhD)., Asst Professor/EEE

Department of Electrical &

Electronics Engineering

SYLLABUS(R-2008) EE2201 MEASUREMENTS AND INSTRUMENTATION 3 0 0 3 1. INTRODUCTION 9

Functional elements of an instrument – Static and dynamic characteristics – Errors

in measurement – Statistical evaluation of measurement data – Standards and

calibration.

2. ELECTRICAL AND ELECTRONICS INSTRUMENTS 9

Principle and types of analog and digital voltmeters, ammeters, multimeters –

Single and three phase wattmeters and energy meters – Magnetic measurements –

Determination of B-H curve and measurements of iron loss – Instrument

transformers – Instruments for measurement of frequency and phase.

3. COMPARISON METHODS OF MEASUREMENTS 9

D.C & A.C potentiometers, D.C & A.C bridges, transformer ratio bridges, self-

balancing bridges. Interference & screening – Multiple earth and earth loops -

Electrostatic and electromagnetic interference – Grounding techniques.

4. STORAGE AND DISPLAY DEVICES 9

Magnetic disk and tape – Recorders, digital plotters and printers, CRT display,

digital CRO, LED, LCD & dot matrix display – Data Loggers

5. TRANSDUCERS AND DATA ACQUISITION SYSTEMS 9

Classification of transducers – Selection of transducers – Resistive, capacitive &

inductive transducers – Piezoelectric, optical and digital transducers – Elements of

data acquisition system – A/D, D/A converters – Smart sensors.

L = 45 Total = 45 Periods

TWO MARKS QUESTION WITH ANSWERS

UNIT – I

INTRODUCTION

1. What is meant by measurement?

Measurement is an act or the result of comparison between the quantity and a predefined standard.

2. Mention the basic requirements of measurement.

· The standard used for comparison purpose must be accurately defined and

should be commonly accepted. · The apparatus used and the method adopted must be provable.

3. What are the 2 methods for measurement?

· Direct method and · Indirect method.

4. Explain the function of measurement system.

The measurement system consists of a transducing element which converts

the quantity to be measured in an analogous form. the analogous signal is then processed by some intermediate means and is then fed to the end device which presents the results of the measurement.

5. Define Instrument.

Instrument is defined as a device for determining the value or magnitude of a quantity or variable.

6. List the types of instruments. The 3 types of instruments are · Mechanical Instruments

· Electrical Instruments and · Electronic Instruments.

7. Classify instruments. • Absolute Instruments • Secondary Instruments

8. What are the 2 modes of operation of secondary Instruments?

· Analog mode and · Digital mode

9. What are analog devices?

Signals that vary in a continuous fashion and take on an infinity of values in

any range are called analog signals. The devices that produces these signals are called analog devices

10. What are digital devices?

Signals that vary in discrete steps and thus take on only finite different values in a given range are called digital signals. The devices that produces these signals are called digital devices.

11. Mention the functions performed by the measurement system.

· Indicating function · Recording function · Controlling function.

12. Give the applications of measurement systems.

· The instruments and measurement systems are sued for · Monitoring of processes and operations. · Control of processes and operations. · Experimental engineering analysis.

13. List the functional elements of the measurement systems.

· Primary sensing element. · Variable conversion element and

· Data processing element.

14. What is signal conditioning?

The performing of non-linear processes like modulation, detection, sampling, filtering, chopping and clipping etc. on the signal to bring it to desired form is called signal conditioning.

16. Give the function of the variable manipulation element.

The function of the variable manipulation element is to manipulate the

signal presented to it preserving the original nature of the signal.

17. What are the characteristics of the measurement system?

· Static characteristics · Dynamic characteristics

18. Why calibration of instrument is important?

The calibration of all instruments is important since it affords the

opportunity to check the instrument against a known standard and subsequently to errors in accuracy.

19. Explain the calibration procedure.

Calibration procedure involves a comparison of the particular instrument with either.

· A primary standard · A secondary standard with a higher accuracy than the instrument to be calibrated or

· An instrument of known accuracy.

20. What are the static characteristics?

· Accuracy · Sensitivity · Reproducibility · Drift · Static error and

· Dead zone.

21. Define true value

True value of a quantity to be measured is defined as the average of an infinite number of measured values when the average deviation to the various contributing factors tends to zero.

22. Define scale range.

The scale range of an instrument is defined as the difference between the

largest and smallest reading of the instrument.

23. What is meant by reproducibility?

Reproducibility is the degree of closeness with which a given value may be repeatedly measured. It may be specified in turns of units for a given period of time.

24. Define repeatability.

Repeatability is defined as the variation of scale reading and is random in nature.

25. Define noise.

Noise is defined as any signal that does not convey any useful information.

26. What is accuracy?

Accuracy is the closeness with which an instrument reading approaches the

true value of the quantity being measured.

27. What is precision?

Precision is measure of the reproducibility of the measurements, i.e. given a fixed value of a quantity; it is a measure of the degree of agreement within a group of measurements.

28. Mention the characteristics of precision.

· Conformity and · Number of significant figures.

UNIT – II ELECTRICAL & ELECTRONICS INSTRUMENTS

1. Mention the two main differences between a flux meter and a Ballistic

Galvanometer.

Flux meter Ballistic

Galvanometer

� Controlling torque is very small controlling torque is high

� Heavy electromagnetic damping

electromagnetic damping is not

heavy

� Less sensitive more sensitive

� Less accurate more accurate

2. What are the adjustments in energy meter?

· Main speed adjustment · Power factor adjustment · Friction adjustment · Creep adjustment

3. Write about DC tests in magnetic measurements.

These are used to determine B-H curve and hysteresis loop of Ferro-

magnetic materials. The direct current is used to have variable m.m.f. and flux

meter is used to measure the flux density. A ballistic galvanometer can be used to

measure flux density. Such tests are also called ballistic tests.

4. Give two differences between analog and digital type phase meters.

Analog type Digital Type This is called balanced modulator method this is called flip-flop method Accuracy is very less high as 0.1

o can be achived

Less stable, sensitive & reliable high stable, sensitive and reliable DC meter is used at the output display unit is used at the output

5. What is creeping?

Without any current through current coil, disc rotates due to the

supply voltage exciting its pressure coil. This is called creeping.

6. Write some advantages of instrument transformer.

· The normal range ammeters and voltmeters can be used along with

these transformers to measure high currents and voltage.

· The rating of low range meter can be fixed irrespective of the value of high

voltage or current to be measured · These transformers isolate the measurement from high voltage and

current circuits. This ensures safety of the operator and makes the

handling of the equipments very easy and safe.

· These can be used for operating many types of protecting devices such as

relays or pilot lights.

7.List out the advantages of Digital Voltmeter The advantage is that the readout is more accurate and it can be read at different

angles.and cost is low.They are Sensitive and Relaible. 8.List out the disadvantages of Digital Voltmeter

The disadvantage is if the signal is not steady then the readout will roll numbers

causing to take a guess of measurement. 9.Define the terms digitizing and digitizing period.

In the digital voltmeters, it is necessary to convert the analog signal to digital

signal. Various techniques used to achieve this conversion. The circuits which are

used to achieve such conversion are called digitizing circuits and the process is

called digitizing. The time required for this conversion is called digitizing period. 10. What are the requirements of a shunt? · The temperature coefficient of shunt and the meter should be low and

should be as equal as possible. · The shunt resistance should be stable and constant with time. · The shunt resistance should not carry currents which will cause excessive

temperature rise. · The soldering joints should not cause a voltage drop. · The values of resistance should not change due to soldering. · The resistance should have low thermal electromotive force with copper. 11. Mention any two precautions to be taken while using a voltmeter. · It should be always connected across the circuit or component whose

voltage is to be measured. · The polarities must be observed correctly. · First use the highest range and then decrease the voltage range until the

sufficient deflection is obtained. · Take care of loading effect.

12.Mention the two main differences between an ammeter and a

voltmeter.

Ammeter Voltmeter It is a current measuring device it is a voltage measuring deveice Always connected in series with circuit Always connected in parallel with

circuit The resistance is very small The resistance is very high

13.Explain the Priniciple of Digital Phasemeter.

The simplest technique to measure the phase difference between two signals employs

two flip-flops.The signals to be fed must be of the same frequency.First, the signals must

be shaped to square waveform without any change in their phase positions,by the use of a

zero crossing detector.

14.What are the adjustments in energy meter?

· Main speed adjustment · Power factor adjustment · Friction adjustment · Creep adjustment

15.Write about AC tests in magnetic measurements.

When a ferro- magnetic material is subjected to cycle of magnetization and

demagnetization then the eddy current and hystereis losses occur. Hence

alternating current is used to determine iron losses, having provision of a variable

frequency and form factor. Such tests are carried out at power, audio or radio

frequencies. 16.Mention the errors in Moving iron instruments.

· Hysteresis error · Temperature error · Stray magnetic field error · Frequency error · Eddy current error

17.What is the essential torques required for operating an instrument? The torques essential for operating instrument are,

(i)Controlling Torque

(ii)Deflecting Torque

·

18.How can we prevent creeping in energy meter?

Two holes are drilled in the aluminum disc 180o opposite to each other.

When this holes comes under the shunt magnet pole, it gets acted upon by a torque

opposite to the rotation.

19. Mention the purpose of Schmitt trigger in frequency meter.

To convert the amplified signal from sine wave to square wave with fast rise

and fall times.

20. Define torque to weight ratio in electrodynamometer instrument.

To have reasonable deflecting torque, mmf of the MC must be enough. Thus

mmf=NI, hence current through MC should be high or no. Of turns should be large.

The current cannot be made high because it may cause excessive heating of spring.

Large no. of N hence is the only option but it increases weight of the coil.

21.Why are the ordinary watt-meters not suitable for low power factor circuits?

Ordinary electro-dynamometer wattmeter is not suitable for measurement of power in

low power factor circuits owing to (i) small deflecting torque on the moving system even

when the current and pressure coils are fully excited and (ii) introduction of large error

due to inductance of pressure coil at low power factor

22. What are the requirements of a Multiplier?

· Their resistance should not change with time · The change in their resistance with temperature should be small. · They should be non-inductively wound for a.c. meters.

23.Mention any two precautions to be taken while using an Ammeter.

· It should never be connected across any source. · The polarity must be observed correctly. · First use the highest range and then decrease the voltage range until the

sufficient deflection is obtained. 24.List the Instruments for measurement of frequency .

o Vibrating Reed type

o Electrical resonance type

o Weston frequency meter

o Digital type o Wien’s bridge

25.What is phase meter? Mention the types of phase meter. Phase Meter is a device which measure the phase difference between two signals.

It classified two types:

1.Analog Phase Meter.

2. Digital Phase Meter.

26.What is a phase sequence indicator?

An electromagnetic or induction instrument used to indicate the phase sequence in

three-phase electric circuits. The phase sequence determines the direction of rotation of

three-phase electric motors; the correct operation of some measuring instruments and

automatic control devices also depends on the phase sequence.

27.What is meant by creeping in energy meter? In respect of energy meters, it is seen that, even without any current through current coil,

the disc rotates due to the supply voltage exciding pressure coil. This is called creeping.

This creeping may be because of over friction compensation To eliminate this, two holes

are drilled in the disc 180o opposite to each other. When these holes come under shunt

magnet pole, they get acted up on by a torque opposite to its rotation. This restricts its

rotation, on no load condition

.

UNIT – III SIGNAL CONDITIONING CIRCUITS

1. What are the characteristics of a DC amplifier?

* It may need balanced differential inputs giving a high common mode

rejection ratio (CMRR) * It should have an extremely good thermal and long term stability.

2. Enumerate the merits and demerits of a dc amplifier.

* It is easy to calibrate at low frequencies. * It is able to recover from an overload condition unlike it’s AC

counterpart. 3. Give the purpose of bridge circuits. What are the different type?

The bridge circuits are used in instrumentation systems for the

measurement of resistance , inductance and capacitance. Types:

DC type and

AC type.

4. What are the 2 types of wheatstone bridge?

* Null type bridge * Deflection type bridge.

5. What are the different types of AC bridges?

AC bridge using push-pull transducers AC bridge with push-pull inductive transducers

Inductive transducer Blumlein bridge

Capacitive transducer Blumlein bridge

6. Define slew rate

Slew rate is defined as the maximum output voltage change per unit time. 7.List the requirements of an instrumentation amplifier

* Low drift * High i/p impedance * High linearity * High CMRR * High noise rejection capability

8. Give few applications of instrumentation amplifier.

The instrumentation amplifier finds increasing application in the amplification of the output signals obtained from thermocouples, strain gauge bridge and biological electrode.

9. What is a filter?

A filter is often a frequency selective circuit that passes a specified band of frequencies and blocks or attenuated signal of frequencies outside this band.

10. List the different types of filters.

* Analog or digital filters * Passive or active filters * Audio (AF) or radio (RF) filters.

11. Specify the advantages of an active filter

* Gain and frequency adjustment flexibility * No loading problem * Low cost

12. What is frequency scaling?

The procedure of converting a cutoff frequency to a new cutoff

frequency is called frequency scaling.

13.What is quality factor ?

The ratio of resonant frequency to bandwidth is known as the quality factor

Q.

14. What is acquisition time of S/H circuit?

Acquisition time is the time required for the capacitor to charge up to

the value of the input voltage after the switch is first started. 15. What is aperture time of S/H circuit?

The aperture time is the time required for the switch to change from ON

state to OFF state. 16.What are detectors normally used for AC bridges?

(i) Head phones (250 Hz to 4kHz) (ii) Vibration galvanometers- most commonly used below 200Hz.

since below 200Hz, there are more sensitive then head

phones.

(iii) Tunable amplifier detectors ( 10 Hz to 100 Hz) 17.What do you understand by the term “ratio transformer”?

(i)The ratio transformer is used in transformer ratio bridges, which are replacing the conventional ac bridges at rapid rate.

(ii) The performance of ratio transformer approaches that of an ideal transformer. An ideal transformer is one that has no resistance, no core loss and leakage flux.

(iii) the ratio transformer is provided with a number of tapings in order

to obtain voltage divisions. 18.What are the constructional requirements for ratio transformer?

(iv) The material used for construction of core should give the smallest core loss at the operating frequency.

(v) Magnetizing current is reduced by using toroidal core (vi) The winding takes the form of a multi conductor rope. The multi

conductor rope has ten wires with successive sets of turns connected in series and tapping is taken each joints.

(vii) Copper wire of heavy cross section is used for the winding to reduce the resistance.

19.What is electromagnetic interference? The energy associated with the current or charge variation in a

conductor gets radiated away from it, at high frequencies such radiations

are the form of waves called electromagnetic waves

e.g. Signal from radio or radar transmitters or by some other sources. These waves have influence in the performance of measuring instruments,

which is termed as electromagnetic interference. 20.What is electrostatic interference?

Two conductors which are near each other form a capacitive effect and get electrically coupled to each other. Voltage change in one conductor causes corresponding interference in the other. This is called electrically coupled interference. This is also known as electrostatic interference or capacitive interference.

21.What is inductive interference?

Magnetic fields due to current carrying conductors produce

inductive interference (electrostatic field produce capacitive

interference) This is also called as magnetically coupled interference.

22.What is an isolation amplifier? Where is it used? An amplifier guard shield with an isolation device is called an isolation amplifier.It is used in the measuring setup of Input guarding.

23.State the condition for balance in Wheatstone bridge.

When the bridge is balanced,the galvanometer carries zero current and it does not shows any deflection.This bridge works on the principle of null deflection or null indication

R1R3=R2R4 This is the required condition for balanced bridge. 24. What are the applications of AC Potentiometers? 1.Voltmeter Calibration,2. Ammeter Calibration,3. Wattmeter & Energymeter Testing and 4.Measurement of self reactance of coil. 25.List the techniques to reduce groudloop interference

1.Murrey loop test 2.Varley loop test

26.List the application of D.C. potentiometers.

The application of D.C. potentiometers are, � Calibration of Ammeter � Calibration of Voltmeter � Calibration of Wattmeter � Measurement of Resistance � Measurement of Power

27.What are parasitic voltages and how are they eliminated?

In electrical circuits, parasitic capacitance, stray capacitance or, when relevant, self-capacitance (of an inductor), is an unavoidable and usually unwanted capacitance that exists between the parts of an electronic component or circuit simply because of their proximity to each other By isolation techniques and grounding methods. While the use of ground planes does lower impedance and helps greatly in lowering ground noise, there may still be situations where a prohibitive level of noise exists. In such cases, the use of ground error minimization and isolation techniques can be helpful.

UNIT- IV

STORAGE AND DISPLAY DEVICES

1.List the components of a magnetic tape recorder.

· Recording head · Magnetic tape · Reproducing head · Tape transport mechanism · Conditioning devices.

2.Mention the different methods of magnetic tape recording.

· Direct recording · Frequency modulation (FM) recording and · Pulse duration modulation (PM) recording.

3. What is the purpose of erase head?

In the erase head, a signal of high frequency and level sweeps the

magnetic tape thereby completely wiping out the information contained there

in. this renders the magnetic tape to be used fresh for smother signal. 4.What is drop out?

In direct recording, some portions of the tape may not be perfectly

recorded owing to dirt or poor manufacturer and this is called drop out. 5.Mention the 2 factors in FM recording

· Percentage deviation and · Deviation ratio

6. What is the operation of a serial printer?

The serial printer produces a single character at a time, usually moving

from left to right across a page. It prints 200 characters per second.

7. Mention the purpose of line printers.

The line printers are used to print and entire line simultaneously. It

points 4000 lines per minute.

8. Give the operation of page printers.

The page printer prints in a line at a time mode, but can be stopped and

restarted only on the page basis. The top speed is 45,000 lines per minute. 9. List the classification of printers.

· Impact and non-impact printers. · Fully formed character and dot matrix character printer. · Character at a time and a line at a time.

10. What is daisy wheel printer?

Daisy wheel printer is a fully formed character printer, designed for

computer usage and has characters mounted on the periphery of a spinning

print head similar to a daisy flow. They are capable of bi-directional printing. 11. Give short notes on dot-matrix printers.

In dot-matrix printers, the characters are formed by printing a group of dots to form a letter, no. or other symbols. It can print any combination of dots with all available print position in the matrix. 12. List the important features of CRTs.

· Size · Phosphor · Operating voltages · Deflection voltages · Viewing screen .

13. What is meant by deflection sensitivity in CRT?

The deflection sensitivity of the CRT is usually stated as the DC voltage

required for each cm of deflection of the spot on the screen.

14. What is meant by recurrent sweep in CRT?

When the saw tooth, being an AC voltage alternates rapidly, the display occurs respectively, so that a lasting image is seen by the eye. This repeated operation is known as recurrent sweep. 15.Mention the methods that are used for generating the 2 electron beams

within the CRT.

The methods that are used for generating the 2 electron beams within

the CRT are the double gun tube and split beam method. 16. Explain CRO and its function.

Cathode Ray Oscilloscope (CRO) is a very careful and versatile

laboratory instrument used for display measurement and analysis of waveforms

and other phenomena in electrical and electronic circuits. CRO is in fact a very

fast X-Y plotter displaying an input signal versus another signal or time. 17. Name the components of a CRO.

CRO consists of a cathode ray tube (CRT) along with electron gun

assembly, deflection plate assembly, fluorescent screen, glass envelope and

base.

18.What is an electron gun?

The source of focused and accelerated electron beam is the electron gun. The electron gun which emits electrons and forms them into a beam consists of a heater, a cathode, a grid a pre-accelerating anode, a focusing anode and an accelerating anode. 19. Name the basic circuitry of CRO.

· Vertical (Y) deflection system · Horizontal (X) deflection system · Synchronization · Blanking circuit · Intensity (z-axis) modulation · Positioning controls

· Focus control · Intensity control · Calibration control · Astigmatism.

20. What is LED?

The LED is basically a semiconductor PN junction diode capable of

emitting electromagnetic radiation under forward conductions.

21. Compare common anode and common cathode displays.

Common anode type display require an active low (or current linking)

configuration for code converter circuitry, whereas an active high output circuit is necessary for common cathode LED type display.

22. List the characteristics of LCD.

· Light scattering · Can operate in reflective or Transmissive configuration. · Do not actively generate light and depend for their operation on

ambient or back light. 23.On what does the operation of LCD depend?

The utilization of a class of organic materials which remain a regular

crystal like structure even when they have melted. 24.Name the 2 commonly available types of LCDs. Dynamic scattering and Field effect type.

25.What is the purpose of dot matrix displays?

Excellent alphanumeric characters can be displayed by using dot matrix

LEDs with an LED at each dot location.

26. What are the commonly used dot matrices for the display

of characters?

The commonly used dot matrices for the display of prominent characters

are 5 x 7, 5 x 8 and 7 x 9

27.What are the 2 writing patterns of dot matrix displays?

* Common anode or common cathode connection (uneconomical) * X-Y array connection (economical and can be extended vertically

or horizontally using a minimum number of wires)

UNIT – V TRANSDUCERS

1. Define transducers.

Transducers are defined as a device which when actuated, transforms energy from one form to another. Generally, any physical parameters is converted into electrical form.

2. What are the 2 types of transducers?

* Electrical and * Mechanical

3. Name the parameters that dictate the transducer capability

* Linearity * Repeatability * Resolution and * Reliability

4. Define sensitivity

Sensitivity is defines as the electrical output per unit change in the

physical parameter. High sensitivity is generally desirable for a transducer. 5. Classify electrical transducers.

* Active * Passive

6. Name the 2 parts of a transducer

* Sensing element * Transduction element

7. Mention the factors considered while selecting a transducer.

• Frequency response & resonant frequency

• Environmental compatibility

• Minimum sensitivity

• Accuracy

• Usage and ruggedness Electrical parameters

8. What is meant by POT?

POT is a resistive potentiometer used for the purpose of voltage division. It consists for a resistive element provided with a sliding contact called as wiper.

9. Explain the working principle of a strain gauge.

Strain gauge works on the principal that the resistance of a conductor or a semiconductor changes when strained. This property can be used for measurement of displacement, force and pressure.

10. Name the different types of strain gauges.

* Un-bonded metal strain gauge * Bonded metal wire strain gauge * Bonded metal foil strain gauge * Vacuum deposited thin metal film strain gauge * Sputter deposited thin metal strain gauge * Bonded semiconductor strain gauge * Diffused metal strain gauge

11. What is meant by rosette?

It is a combination of strain gauges to a single element strain gauge. 12. Give the 3 working principles of variable inductance transducers

* Change of self inductance * Change of mutual inductance * Production of eddy currents.

13. Write notes on LVDT

It is the linear variable differential transformer which is used to translate the linear motion into electrical signals. It consists of a single primary winding and 2 secondary winding.

14. List the advantages of LVDT

• High range of displacement measurement Friction &

electrical isolation Immunity from external effects High I/p and

high sensitivity Ruggedness

• Low hysterisis & low power consumption.

15. What is a digitizer?

It is a digital encoding transducer that enables a linear or rotary displacement to be directly converted into digital form without intermediate forms of analog to digital (A/D) conversion.

16.List the various electrical transducers.

1. Resistive 2. Inductive 3. Capacitive 4. Electromagnetic 5. Piezo-electric 6. Photo-emissive 7. Photo-resistive 8. Potentiometric 9. Thermo-electric

10. Frequency generating

17.What is resistance transducer? Resistive transducers are those in which the resistance changes due to a change in some physical phenomenon.

Eg. The change in value of resistance with a change in length

of the conductor can be used to measure displacement.

18.What is the principle of working of strain gauge? What are the types? Strain gauge is a passive transducer that uses the variation in

resistance in wires to sense the stress produced by the force on the

wire.

Types of Strain Gauges: 1. Wire Strain Gauges 2. Foil Strain Gauges 3. Semiconductor Strain Gauges

19.Define Gauge Factor of Strain Gauge? Gauge Factor is the ratio of “Change in resistance of the resistive

transducer” to “ the Change in Strain” applied on it.

20.What is the commonly used material as sensor in resistance

thermometer? Platinum, Nickel and copper among which platinum. 21.Differentiate between Sensor & Transducer S.NO Sensor Transducer

1 A device produce

measurable response to a

change in physical

condition.

A device which converts physical

quantity into the proportional

electrical signal

2 All sensors are not

transducers.

All transducers can be called as

sensor.

3. Example:Fiber obtic

sensor,Pressure sensor

Example:Generator,LVDT

22. What are the classifications of encoder? The three types are,

(i) Tachometer Encoder (ii) Incremental Encoder and (iii) Absolute Encoder.

23. What is the need of sample and hold circuit in A/D converter?

An individual S/H is assigned to each channel and they are updated synchronously by timing circuit. The S/H outputs are connected to an A/D converter through a multiplexer resulting in a sequential readout of the outputs.

24.Draw the Block Diagram for 4-bit Analog to Digital Converter Analog I/P Bo B1 B2 B3

25 .State Performance parameters of ADC.

ADC performance specifications are generally categorized in two ways: DC accuracy and dynamic performance. Most applications use ADCs to measure a relatively static, DC-like signal)or a dynamic signal.

Absolute error The absolute error is the total DC measurement error and is characterized by the offset, full-scale, INL, and DNL errors.

Signal-to-noise ratio The signal-to-noise ratio (SNR) is the ratio of the root mean square (RMS) power of the input signal to the RMS noise power (excluding harmonic distortion), expressed in decibels (dB)

26.Define Primary & Secondary Transducers. For example,the pressure is converted into a displacement by Bourdontube then the displacement is converted into an analogous voltage by LVDT.The bourdon tube is called a “Primary Transducer” while the LVDT is called an “Secondary Transducer”.

ADC

PART-B UNIT -I

1.Describe the functional elements of an instrument with its block

diagram. (16) Block Diagram(4) Explanation of

• Primary sensing Element(2) • Variable conversion and Variable Manipulation element with

relating two blocks(6) • Data Transmission & Data Presentation Element(4)

2.Explain the different types of Error.(8)

• Classification of Errors(1) • Gross Error(2) • Systematic Error(3) • Random Error(2)

.

3.Define the following terms (10)

a) Mean value (2) b) Deviation (2) c) Average deviation (2) d) Variance (2) e) Standard deviation (2).

� Note: Definition and Formula carry one mark each

4.. Discuss in detail the various static characteristics of a measuring system(16)

List out the static characteristics (2) Explanation with necessary Graph(10)

5.Discuss in detail the various dynamic characteristics of a measuring system(8) List out the characteristics(1) Explanation(5)

6.If X1 = 49.7, X2 = 50.1, X3 = 50.2, X4 = 49.6, X5 = 49.7.Find a) Arithmetic mean b) Deviation of each value

c) Algebraic sum of the deviations (6)

a) Arithmetic mean (2) b) Deviation of each value (2) c) Algebraic sum of the deviations(2)

Note: Formula and calculation carry one mark each

8.

87. What is standard? Explain the different types of standards? (8) Definition(2) Classification(1) Explanation(5)

8.What are the different standard inputs for studying the dynamic response of a System? Define and sketch them. (8)

Types(1) Definition and Figure(7)

89. What is Calibration? Explain the different types of calibration (8) Definition(2) Classification(1) Explanation(5)

UNIT – II

1.(i) Describe the construction and working of a permanent magnetic moving coil

instruments. (10) Diagram(3) Construction Explanation(3) Working Explanation(4) (ii)Explain the design of three phase wattmeter and give the reactive power measurement in three phase circuits (6) Construction Diagram(1) Connections b/w resistance and wattmeter diagram(2) Explanation(3)

2.2. (i)How B-H curve is determined for a ring specimen.(8)

Diagram of Ring specimen(1) B-H curve Graph(3) Explanation of two methods(2+2)

(ii) With a neat diagram, explain the various methods of magnetic measurements.(8) Diagram(2) Explanation of each method with necessary equations(3+3)

� Equation carries one mark each in both methods.

(8)

3. Explain the function of three phase wattmeter and energy meter (16) Diagram of 3 phase wattmeter(3) Explanation of 3 phase wattmeter(5) Diagram of 3 phase energymeter(3) Explanation of 3 phase energymeter(5)

4.(i)Sketch the circuit and waveforms for ac voltmeter using a PMMC instrument and half wave rectifier. Explain the circuit operation.(10) Circuit Diagram(2) Wave forms(4) Explanation(4)

(ii) Develop the torque equation for a PMMC instrument and show its scale is

Working principle(1) Derivation (4) Explanation for linear variation(1)

5.(i) Discuss in detail the working of the successive approximation DVM.(8) Diagram(3) Explanation(5) (ii) Explain with neat diagram the working of Linear ramp type DVM. (8)

Diagram(3) Explanation(5)

6 .

6.(i)Explain the construction and working of a Single phase induction type energy meter.(10) Diagram(3) Construction Explanation(3) Working Explanation(4) (ii)How the range of D.C ammeter and D.C.Voltmeter can be etended?Derive the expression to calculate shunt resistance and multiplier resistance.(6) Explanation(1) Diagram(1) Derivation upto Rs(2) Derivation upto Rm(2)

7

6. (i)With a neat diagram, explain the construction and working of electrodynamometer type instruments. Also derive its torque equation.(16)

Diagram(3) Construction Explanation(3) Working Explanation(4) Torque Equation derivation(6) 777.(i) With a neat block diagram explain the working principle of digital

frequency meter.(6) Block Diagram(2) Explanation(4) (ii) Explain the working principle of moving iron instrument.(10) Diagram of two types(2+2)

linear(6)

Working Explanation(3+3) 888.Give a detailed notes on Instrument transformers.(16)

Diagram of Current Transformer & Potential Transformer(3+3) Explanation of Current Transformer & Potential Transformer(3+2) Use of Instrument Transformer(1) Advantages & Disadvantages(2) Ratios of Instrument Transformer(1) Burden of an Instrument Transformer(1)

UNIT – III

1. (i) Explain in detail about the laboratory type DC potentiometer. (10)

Diagram(4) Explanation(6)

(ii) Give the applications of AC potentiometers.

Explanation(6)

2. (i) Describe about the multiple earth and earth loops. (10)

Diagram(2+2) Explanation(3+3) (ii) Explain the different techniques of grounding. (6)

Murrey loop test & Varley loop test Diagram(3) Explanation of Murrey loop test & Varley loop test (3) 3.(i) Explain how inductance in measured by using Maxwell’s bridge. (8)

Circuit Diagarm(3) Condition of Balanced Bridge(1) Derivation for finding Unknown inductance(4)

(ii) Explain the frequency measurement in Wien’s bridge.(8)

Circuit Diagarm(2) Condition of Balanced Bridge(1) Derivation for Unknown inductance/capacitance(3) Formula & solution for finding frequency(2)

4.Explain voltage sensitive self balancing bridge, and derive the bridge sensitivity of voltage sensitive bridge with fundamentals. (16)

Circuit Diagram of voltage sensitive self balancing/Wheatstone bridge(4)

Explanation & Derivation for unknown resistance at null condition(6) Derivation for finding Bridge sensitivity(6)

5.(i)Explain the Kelvin bridge for the measurement of low resistance.(8)

Circuit Diagarm(3) Condition of Balanced Bridge+ Assumptions(1) Derivation for finding Unknown resistance(4)

(ii) Discuss the advantages and limitations of electromagnetic interference in measurements. (8)

Explanation of Advantages(4) Explanation of Limitations(4)

6.(i) Explain the working principle of Anderson’s bridge and also derive its balance equations. (8) Circuit Diagarm(2) Phasor Diagram + Condition of Balanced Bridge(2) Derivation for finding Unknown inductance(4)

(ii) Explain the working principle of Schering bridge and also derive its balance equations. (8) Circuit Diagarm(3) Condition of Balanced Bridge(1) Derivation for finding Unknown Capcitance(4)

7.(i)Explain the construction details about the types of AC potentiometer.(10) Diagram of Drysadle & Gall Tinsely Potentiometer(2+2) Explanation of each(2+2) Advantages,Disadvantages,Limitations of each(1+1) (ii) With fundamentals distinguish between DC and AC potentiometers, and give any two specific applications for each. (6)

Explanation(4) Applications of each(1+1)

UNIT-IV 1. Describe the construction and working of LCDs, mention the difference

between light scattering and field effect types of LCDs, also explain the advantages of LCDs (16)

Diagram of Light scattering and Field effect type (2+2) Explanation of Construction for Light scattering and Field effect type (2+2) Explanation of Working for Light scattering and Field effect type (2+2) Difference between Light scattering and Field effect type (2) Advantages of each(2)

2. (i) Give the basic block diagram of a digital data recording system (8)

Diagram(4) Explanation for function of each blocks(4) (ii) Explain with a neat sketch

a) Dot matrix displays b) Bar graph displays (8)

Diagram+Explanation of Dot matrix displays(2+2) Diagram+Explanation of Bar graph displays(2+2)

3. (i) Explain the basic elements of a magnetic tape recorder. (8)

Diagram(4) Explanation for function of each blocks(4)

(ii) Explain the block diagram of oscilloscope with a neat sketch. (8)

4.

Diagram(4) Explanation for function of each blocks(4)

(i) Describe the basic components of a CRT.(10)

Diagram(2) Explanation of components(8)

(ii) Write short notes on liquid crystal displays. (6)

Diagram of Light scattering and Field effect type (1+1) Explanation for Light scattering and Field effect type (2+2)

5. (i) With a neat block diagram, explain the working of digital storage

oscilloscope. (8)

Diagram(4) Explanation for function of each blocks(4) (ii) Discuss briefly about the applications of LED.

(8)

6

LED cross section Diagram(1) LED controlled by a transistor switch(2) Explanation(5)

.(i) What are the various types of oscilloscopes?

(4)

Types of oscilloscopes (4) (ii) Discuss in detail the construction of a storage type oscilloscope. What

are the accessories for a CRO? (12) Diagram(4) Principle of Operation(2) Explanation of Construction & working(4) Accessories for a CRO(2) 7.(i)Explain in detail, how the data is stored in a magnetic disk and tape? (10)

Diagram(3) Explanation of Construction & working(3+4) (ii) Describe the performance of digital plotter. (6)

Diagram(2) Explanation of working(4) 8.(i) Explain the block diagram of a general purpose oscilloscope and also

describe about the observation of waveform on CRO. (10)

Block Diagram(2) Explanation for function of each blocks(5) Waveform(1) Explanation for waveform(2) (ii) Write short notes on Printers. (6)

Diagram (2) Explanation for working of Different types(4)

UNIT-V

1. (i) Explain the principle of inductive and capacitive transducer. (8)Diagram of inductive and capacitive transducer(1+1) Principle of inductive and capacitive transducer(1+1) Working of inductive and capacitive transducer(2+2)

(ii) Explain the construction and working of LVDT with a neat sketch (8) Diagram of LVDT (2) Principle of LVDT (1) Construction & Working of LVDT (2+3)

2.(i) Explain different strain gauges with their principle of operation. (8) Types(1)

Diagram+Principle of operation(7) (ii) Discuss in detail about resistive transducers. (8)

Types(1) Diagram+Principle of operation(3+4)

3. (i) Explain the various types of temperature transducers. (8) Types(1)

Diagram+Principle of operation(3+4) (ii) Explain the function of piezoelectric transducer. (8) Diagram (3) Principle of Working(5)

4. (i) Explain the binary weighted resistor technique of D/A

conversion.(8) Diagram (3) Explanation(5) (ii) Define the following terms for D/A converters:

a) Resolution b) Accuracy c)Monotonicity and d) conversion time(8)

Defination of each carries two mark(4*2=8)

5. (i) Explain the resistive transducer with respective to potentiometer. (4)

Diagram (1) Explanation(3)

(6)

(ii) Explain the capacitive transducer.

Diagram (2) Explanation(2) Derivation for Capacitance(2)

(iii) Describe the piezoelectric transducer and give the formula for coupling

coefficient. (6) 6.

Diagram (2) Explanation(2) Derivation for Coupling Co-efficient(2)

(i) Explain schematic block diagram of a general data acquisition system

(DAS) and give its objectives (6)

Diagram(2) Explanation for function of each blocks(4) (ii) Discuss R-2R ladder type D/A converter. (6)

Diagram(2) Explanation(4) (iii) For a 5 bit ladder, if the input levels are 0 = 0V and 1 = 10V, what are

the output voltages for each bit? (4)

7.

Formula(1) Substituting of given values(2) Solution(1) Explain the various types of ADC with suitable sketches. (16)

Diagram of various(4) types(2+2+2+2=8) Explanation of various types(4*2=8) 8. Explain the working principle of various types of DAC with neat sketches. (16)

Diagram of various types(4) Derivation for Calculation of Imax(6) Explanation of various types(6) 9.(i) Explain the principle of operation a thermocouple with neat sketch. (10)

Diagram of Thermocouple (2) Characteristic Graph(2) Explanation of Thermocouple(4) Advantages & Disadvantages(1) (6)

Limitations(1) (ii) Give a short note on single and multi channel DAS.

10.

Diagram of single and multi channel DAS (1+1=2) Explanation of single and multi channel DAS (2*2=4) (i) Explain the different types of optical encoders. (8)

Diagram of various(2) types(2+2=4) Explanation of various types(2*2=4) (ii) Explain the successive approximation type ADC. (8)

Diagram(3)

Explanation(5)

Previous Year Question Papers

B.E/B.Tech Degree Examination, NOVEMBER/ DECEMBER 2009 Third semester

Electrical and Electronics Engineering EE 2201 — MEASUREMENTS AND INSTRUMENTATION

(Regulation 2008) Time : Three hours

Maximum : 100 Marks

Answer ALL questions PART A — (10 × 2 = 20 Marks)

1. Differentiate Resolution from Threshold. 2. How are the absolute error and relative errors expressed mathematically? 3. What is the essential torques required for operating an instrument? 4. What is phase meter? Mention the types of phase meter. 5. What is an isolation amplifier? Where is it used? 6. State the condition for balance in Wheatstone bridge. 7. What are the types of printers according to printing Technology? 8. What are the main parts of cathode ray tube? 9. Differentiate Sensor from Transducer 10. Draw the block diagram for 4-bit analog to digital converter.

PART B — (5 × 16 = 80 Marks)

11. (a)Define and explain the static characteristics of an instrument. Or

(b) (i) Draw and explain the general block diagram of measurement system.(10)

(ii) Write note on the different types of errors. (6)

12.(a)Describe the construction and working of single phase induction type energy meter.

Write a short note on any two adjustments required in energy meter.

Or (b)Explain with neat sketch the classification of instrument transformers. Write a note on the

errors affecting the characteristics of an instrument transformer

13.(a)with a neat sketch describe a bridge to determine the unknown inductance and a bridge

to determine the unknown capacitance

Or (b)Explain the grounding techniques in detail to reduce the ground loop interfence signal.

14.a)Describe LED & LCD display devices.

Or

b)Describe the direct and frequency modulation magnetic tape recording types.Give its merits

and demerits.

15.a)What are the selection criteria for the transducers?Explain the working principle of LVDT

with neat sketch & Characteristics.Give the advantages,disadvantages and applications of

LVDT.

Or

b)What are the performance parameters of analog to digital converter?Explain any two basic

A/D conversion techniques in detail.

Answers :

PART-A

1.Difference between Resolution and Threshold

S.No Resolution Threshold

1 If non zero quantity is slowly

increased, output reading will not

increase until some minimum

change in input is called resolution

If input quantity is slowly increased from zero,

output does not change until some minimum

value of input is exceeded. This minimum

value is called threshold

2 Smallest measurable input change Smallest measurable input

2. Absolute error and Relative error mathematical expression:

Absolute Error (E)= At –Am

Whereas,At-True value of the quantity,

Am-Measured value of the quantity

Relative Error(Er)=E/At=(At-Am)/At

3.Essential Torques for Operating Instrument: The torques essential for operating instrument are, (i)Controlling Torque (ii)Deflecting Torque 4.Phase meter & its types; Phase Meter is a device which measure the phase difference between two signals. It classified two types: 1.Analog Phase Meter. 2. Digital Phase Meter. 5. Isolation amplifier & its Uses: An amplifier guard shield with an isolation device is called an isolation amplifier. It is used in the measuring setup of Input guarding.

6. Condition for balanced Wheatstone bridge: When the bridge is balanced,the galvanometer carries zero current and it does not shows any deflection.This bridge works on the principle of null deflection or null indication

R1R3=R2R4 This is the required condition for balanced bridge. 7.Types of Printers: Types of Printers are 1)Line Printers, 2)Drum Printers,3)Chain Printers,4)Dot Matrix Printers,5)Inkjet Printers,6)Laser Printer & 7)Thermal Transfer Printer 8.Main Parts of Cathode Raytube: The main parts of cathode raytube are1)Electron gun,2)Deflection System,3)Fluroscent Screen, 4)Glass tube or envelope and 5)Base. 9..Difference between Sensor & Transducer: S.NO Sensor Transducer

1 A device produce measurable

response to a change in physical

condition.

A device which converts physical quantity

into the proportional electrical signal

2 All sensors are not transducers. All transducers can be called as sensor.

3. Example:Fiber obtic sensor,Pressure

sensor

Example:Generator,LVDT

10.Block Diagram for 4-bit Analog to Digital Converter Analog I/P Bo B1 B2 B3

ADC

PART-B

11.a)Static characteristics of an instrument(16)

Definition(2),List out the characteristics any10(2)

Explanation of 10 chararcteristics(10*1=*10)

Diagram of Hystersis,Threshold,Resolution(2)

For Expalanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 Page no-25 to 41(in chapter 2) b) (i)General block diagram of measurement system(10) Diagram(2) Explanation of

• Primary sensing Element(1) • Variable conversion and Variable Manipulation element with relating two blocks(3) • Data Transmission & Data Presentation Element(1+1)

For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 Page no- 9 to 11,[Chapter 1,Heading 1.13-Elements of generalized measurement system] (ii) Different types of errors(6)

• Classification of Errors(1) • Gross Error(1) • Systematic Error(3) • Random Error(1)

For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 67 to 70,[Chapter 3,Heading 3.5 to 3.8) 12.(a) Construction and working of single phase induction type energy meter

• Construction Diagram(2) • Explaining the 4 main parts(4) • .Working & derivation of Deflecting torque with phasor diagram(1+4+1=6)

• Two adjustment methods(4) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 467 to 473,[Chapter 12,Heading 12.7) (b) Classification of instrument transformers &its Errors(16)

• Diagram of Potential & Current Transformer(2+2) • Explanation of construction details of each(2+2) • Explanation for errors of instrument transformers(2+2) • Errors & its reduction methods(2+2)

For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 387 to 393,405 to 409[Chapter 10,Heading 10.5 , 10.5.2, 10.5.3, 10.5.4, 10.6, 10.6.3,10.6.4)

13. (a)Bridge to determine the unknown inductance and the unknown capacitance(16) Bridge to determine the unknown inductance (Maxwell Bridge)

• Circuit Diagarm(3) • Condition of Balanced Bridge+ Assumptions(1) • Derivation for finding Unknown Inductance(4)

Bridge to determine the unknown capacitance(Schering Bridge) • Circuit Diagarm(3) • Condition of Balanced Bridge+ Assumptions(1) • Derivation for finding Unknown Capacitance(4) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 589 & 598,[Chapter 16,Heading 16.5.1 &16.6.2)

(b) Grounding techniques to reduce the ground loop interfence signal (16)

• Diagram of two methods (2+2) • Derivation for finding length of fault cable with(4+4) • Disscussion of two methods(2+2) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics d Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 549 to 551,[Chapter 14,Heading 14.6.1)

14.(a) LED & LCD display devices(16)

• Diagram of LED & LCD(2+2)

• Explanation for LED & LCD(4+4) • Advantages & Disadvantages of LED & LCD(2+2) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics d Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 549 to 551,[Chapter 14,Heading 14.6.1)

(b).Direct and Frequency modulation magnetic tape recording types

• Diagram of each(2+2) • Explanation of each(4+4) • Advantages of each(1+1) • Disadvantages of each(1+1) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics d Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 1319 to 1323,[Chapter 28,Heading 28.5.1,28.5.2.)

15. (a)Selection criteria for the transducers & LVDT

• Selection criteria for the transducers(6) • LVDT diagram(2) • Working principle of LVDT(2) • Characteristics of LVDT(3) • Advantages & Disadvantages of LVDT(2) • Applications of LVDT(1) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics d Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 949 & 1001 to 1006,[Chapter 25,Heading 25.10 &25.24) (b) Analog to digital converter • Performance parameters(2) • Diagram of each method of ADC(3+3) • Explanation of each method of ADC(4+4) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics d Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 1188 to 1191,[Chapter 26,Heading 26.28, 26.28.1 &26.28.2)

Answers :

PART-A

1.Difference between Range and Span

S.No Range Span

1 The scale range of an instrument is defined as the difference between the largest and smallest reading of the

instrument.

The scale range of an instrument is defined as the difference between the Highest point of calibration and lowest

point of calibration of the instrument.

2 Example: Range of Thermometer

is 200 0C to 500 0C

Example: For the range of Thermometer

200 0C to 500 0C, Span is 300 0C

2.Stanadard Deviation:

For an infinite number,it is defined as the square root of the sum of individual deviations squared divided by number of readings.

For an finite number,the standard deviation is given by,(for readings less than 20)

Where, -Standard Deviation n-no.of.readings -Deviation from mean 3.Advantages of Digital Voltmeter The advantage is that the readout is more accurate and it can be read at different

angles.and cost is low.They are Sensitive and Relaible.The disadvantage is if the signal is not steady then the readout will roll numbers causing to take a guess of measurement.

4.Priniciple of Digital Phasemeter The simplest technique to measure the phase difference between two signals

employs two flip-flops.The signals to be fed must be of the same frequency.First, the signals must be shaped to square waveform without any change in their phase positions,by the use of a zero crossing detector.

5.Applications of AC Potentiometers

1.Voltmeter Calibration,2. Ammeter Calibration,3. Wattmeter & Energymeter Testing and 4.Measurement of self reactance of coil.

6.Techniques to reduce groudloop interference 1.Murrey loop test 2.Varley loop test 7.Advantages of LCD over LED

They have low power consumption.A seven segmental display requires 140 microwatt(i.e 20 microwatt/segment).This is the great advantage over LED which requires 40 microwatt per numeral.

8.X-Y Recorders It is an instrument which gives a graphic record of relationship between two

variables. In X-Y recorders, an emf is plotted as a function of another emf.

9.Primary & Secondary Transducers For example,the pressure is converted into a displacement by Bourdontube then the displacement is converted into an analogous voltage by LVDT.The bourdon tube is called a “Primary Transducer” while the LVDT is called an “Secondary Transducer”.

10.Performance parameters of ADC ADC performance specifications are generally categorized in two ways: DC

accuracy and dynamic performance. Most applications use ADCs to measure a relatively static, DC-like signal)or a dynamic signal.

Absolute error The absolute error is the total DC measurement error and is characterized by the offset, full-scale, INL, and DNL errors.

Signal-to-noise ratio The signal-to-noise ratio (SNR) is the ratio of the root mean square (RMS) power of the input signal to the RMS noise power (excluding harmonic distortion), expressed in decibels (dB

PART-B

11.(a) i) Funcional Elements of Instrument system(6) • Block Diagram(2) • Explanation of each blocks(4) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 9 to 11,[Chapter 1,Heading 1.13-Elements of generalized measurement system]

(ii)Static Characteristics of instrument(10) • List out the characteristics any 8(1) • Explanation of 8 chararcteristics(8*1=*8) • Diagram of Hystersis,Threshold,Resolution(1)

For Expalanation to these characteristics refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no-25 to 41(in chapter 2)

(b) (i) Different types of errors(10) • Classification of Errors(1) • Gross Error(2) • Systematic Error(5) • Random Error(2) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 67 to 70,[Chapter 3,Heading 3.5 to 3.8)

(ii)Calibration of Instrument(6) • Explanation of two methods(2+2) • Example for two methods(1+1) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 1&2,[Chapter 1,Heading 1.3) 12.(a)(i) Working of Attraction & Repulsion type of Moving Iron

Instruments(8) • Diagram of two types(1+1) • Working Explanation(3+3) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 316&317,[Chapter 9,Heading 9.9.2) (ii)Block Diagram of DMM(8) • Block diagram(4) • Explanation(4) Refer text book by Kalsi, H.S., “Electronic Instrumentation”, Tata McGraw Hill,

2004. • Page no- 148 &149,[Chapter 6,Heading 6.2] (b)(i) Detrmination of B-H curve(8) • Diagram of Ring specimen(1) • B-H curve Graph(3) • Explanation of two methods(2+2) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 660 to 665,[Chapter 18,Heading 18.3.5]

(ii)Digital Frequency meter(8)

• Block Diagram(3) • Explanation(5) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 1297 to 1298,[Chapter 28,Heading 28.24,28.25]

13(a).(i)DC potentiometer for Calibration of ammeter,voltmeter & wattmeter • Diagram(4) • Explanation(6) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 568,569,570[Chapter 15,Heading 15.1.11]

(ii)Schering’s Bridge

• Circuit Diagarm(3) • Condition of Balanced Bridge(1) • Derivation for finding Unknown Capcitance(4) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 598,599[Chapter 16,Heading 16.6.2] 13.b.(i)Methods of Deflecting Electron beam in CRT • Diagram(1+1) • Explanation(3+3)

For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 787 to 790[Chapter 21,Heading 21.5 &21.6] (ii)Multiple Earth & Earth Loops • Diagram(1+1) • Explanation(3+3) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 547 to 549[Chapter 14,Heading 14.5.1 &14.5.2] 14.a.(i).Basic components of Magnetic recorders • Diagram(3) • Explanation(5) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 1317 to 1318,[Chapter 28,Heading 28.49,28.50,28.50.1,28.50.2] (ii).Types of Printers • Explanation(2+3+3) Refer text book by Kalsi, H.S., “Electronic Instrumentation”, Tata McGraw Hill,

2004. • Page no- 54 & 55,[Chapter 2,Heading 2.13 &2.14)

b (i) Digital storage oscilloscope:

• Diagram(3) • Explanation(5) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 825 to 827,[Chapter 21,Heading 21.24.1] (ii)Operation and types of LCD

• Diagram of LCD(2) • Explanation LCD(4) • Advantages & Disadvantages of LCD(2) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics d Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 549 to 550,[Chapter 14,Heading 14.6.1)

15.a.(i) Selection Criteria for Transducers(6) • Explanation(6)

For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics d Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 949 [Chapter 25,Heading 25.10] (ii).Resistance Potentiometric Transducer(6)

• Diagram(2) • Explanation(3) • Advantages & its disadvantages(1)

For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics d Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 951 [Chapter 25,Heading 25.12] (iii)Pressure capacitive transducer

• Diagram(2) Explanation(2) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics d Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 1017,1018 [Chapter 25,Heading 25.8.2]

131301 MEASUREMENTS AND INSTRUMENTATION Third semester

NOVEMBER/ DECEMBER 2010 question paper

Electrical and Electronics Engineering EE 2201 — MEASUREMENTS AND INSTRUMENTATION

(Regulation 2008) Time : Three hours

Maximum : 100 Marks

Answer ALL questions PART A — (10 × 2 = 20 Marks)

1. Define static characteristics of an instrument. 2. What is meant by absolute error of measurement? 3. Why are the ordinary watt-meters not suitable for low power factor circuits? 4. What is a phase sequence indicator? 5. List the application of D.C. potentiometers. 6. What are parasitic voltages and how are they eliminated? 7. What is the purpose of a Post Deflection Acceleration (PDA) in a CRT? 8. Differentiate between LED and LCD. 9. What are the classifications of encoder? 10. What is the need of sample and hold circuit in A/D converter?

PART B — (5 × 16 = 80 Marks)

11.(i) Draw the block diagram of functional elements of measuring system and explain the function of each block. (8) (ii) Explain the different types of errors in measurements. (8)

Or (b) (i) The probable values of two resistors and their S.D are specified as R1 – 18.62 , S.D = 0.025 , R2 = 74.48 , S.D. = 0.05 . Find the probable value and S.D for the two resistors when they are connected in (1) Series and (2) Parallel. ( 8) (ii) Discuss the different types of standards of measurements. (8) 12.(a) (i) What are the various types of digital voltmeters? With a neat sketch explain the working principle of any one type of a digital voltmeter. (8) (ii) With a neat diagram explain the construction and its working principle of elector dynamo-meter type watt-meter. Also derive its torque equation. (8)

Or (b) (i) Explain the method of measurements of B.H curve of a ring specimen with a neat diagram( 8)

(ii) Describe the construction and working principle of digital frequency meter. (8) 13.(a) (i) Draw a neat sketch of a modern slide-wire D.C potentiometer and discuss how the potentiometer is standardized. (8) (ii) Describe how co-ordinate type potentiometer can be used for calibration of a voltmeter and A.C energy meters. (8)

Or (b) (i) Explain the theory and working principle of Kelvin's double bridge method for measurement of low resistance. Derive the relation for finding unknown resistance. (8) (ii) Discuss briefly how Hay's Bridge can be used for the measurement of inductance. ( 8) 14.(a) (i) Explain the construction and its working principle of X-Y Recorder. (6) (ii) Briefly discuss the features of digital plotters and printers. (10)

Or (b) (i) Explain the working principle of electrostatic deflection system in a CRT. (10) (ii) Explain the working principle of digital storage oscilloscope. (6) 15.(a) (i) Explain the construction and working of unbounded and bonded type strain gauges.(8) (ii) Explain the construction and working of optical encoders with aneat diagram. (8)

Or (b) (i) Draw the generalized block diagram of a digital data acquisition system and explain. (8) (ii) Explain the successive approximation method of A/D converter. (8)

2

Answers :

PART-A

1. Static characteristics of an instrument · The Static characteristics are considered for an instruments which are used to

measure an unvarying process condition.The static characteristics are, · Accuracy · Sensitivity · Reproducibility · Drift · Static error and · Dead zone.

2. Absolute error of measurement It is defined as the difference between true value of the quantity to the measured value of the quantity.

Absolute Error (E)= At –Am

Whereas,At-True value of the quantity,

Am-Measured value of the quantity

3. Ordinary watt-meters not suitable for low power factor circuits

Ordinary electro-dynamometer wattmeter is not suitable for measurement of power in low power factor circuits owing to (i) small deflecting torque on the moving system even when the current and pressure coils are fully excited and (ii) introduction of large error due to inductance of pressure coil at low power factor

4.Phase sequence indicator

An electromagnetic or induction instrument used to indicate the phase sequence in three-phase electric circuits. The phase sequence determines the direction of rotation of three-phase electric motors; the correct operation of some measuring instruments and automatic control devices also depends on the phase sequence. 5. Application of D.C. potentiometers The application of D.C. potentiometers are,

� Calibration of Ammeter � Calibration of Voltmeter � Calibration of Wattmeter � Measurement of Resistance � Measurement of Power

6.Parasitic voltages and its elimination In electrical circuits, parasitic capacitance, stray capacitance or, when relevant,

self-capacitance (of an inductor), is an unavoidable and usually unwanted capacitance that exists between the parts of an electronic component or circuit simply because of their proximity to each other By isolation techniques and grounding methods. While the use of ground planes does lower impedance and helps greatly in lowering ground noise, there may still be situations where a prohibitive level of noise exists. In such cases, the use of ground error minimization and isolation techniques can be helpful. 7. Purpose of a Post Deflection Acceleration When the measurements are made above the frequency of 10MHz,post accelerators are used. They have a large beam accelerating bias after the deflection plates so as to increase the beam energy and give a bright display on screen. 8.Differentiate between LED and LCD S.NO LED LCD

1 LED is basically a semiconductor

PN junction diode capable of

emitting electromagnetic radiation

under forward conductions.

The utilization of a class of organic

materials which remain a regular crystal

like structure even when they have

melted.

2 They have high power

consumption while compare to

LCD

They have low power consumption.

3. LED which requires 40 microwatt

per numeral.

LCD requires 140 microwatt(i.e20

microwatt/segment).

9. Classifications of encoder The three types are,

(iv) Tachometer Encoder (v) Incremental Encoder and (vi) Absolute Encoder.

10. Sample and hold circuit in A/D converter

An individual S/H is assigned to each channel and they are updated synchronously by timing circuit. The S/H outputs are connected to an A/D converter through a multiplexer resulting in a sequential readout of the outputs.

Part-B 11.(a) i) Funcional Elements of Instrument system(8) • Block Diagram(3) • Explanation of each blocks(5) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 9 to 11,[Chapter 1,Heading 1.13-Elements of generalized measurement system]

(ii) Different types of errors(8) • Gross Error(2) • Systematic Error(4) • Random Error(2) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 67 to 70,[Chapter 3,Heading 3.5 to 3.8]

(b)(i) Finding of probable value and S.D

• Formula for Probable value and SD while resistors are connected in series(2) • Solution of Probable value and SD while resistors are connected in series(2) • Formula for Probable value and SD while resistors are connected in Parallel(2) • Solution of Probable value and SD while resistors are connected in Parallel(2)

(ii) Different types of standards

• Definition(2) • Classification(1) • Explanation(5)

For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 181 to 182,[Chapter 5,Heading 5.20] 12(a).(i)Digital voltmeters

• Different types(1) • Diagram of any one type(3) • Explanation of any one type(4)

For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 1303 to1308,[Chapter 28,Heading 28.31) (ii)Electrodynamometer type wattmeter

• Diagram(1) • Construction Explanation(1) • Working Explanation(2) • Torque Equation derivation(4)

For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 431,432[Chapter 11,Heading 11.3.1,11.3.2]

( b)(i) Detrmination of B-H curve(8) • Diagram of Ring specimen(1) • B-H curve Graph(3) • Explanation of two methods(2+2) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 660 to 665,[Chapter 18,Heading 18.3.5]

(ii)Digital Frequency meter(8)

• Diagram(3) • Explanation(5) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 1297 to 1298,[Chapter 28,Heading 28.24,28.25]

13.a.(i). Modern slide-wire D.C Potentiometer and Potentiometer standardisation

• Diagram(2) • Construction & working(3) • Standardisation(3) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 558 to 559,[Chapter 15,Heading 15.1.1]

(ii)Co-ordinate type potentiometer for calibration of a voltmeter & A.C energy meters

• Diagram(2) • working(2) • calibration of a voltmeter(2)

• calibration of A.C energy meters(2) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 576,578 to 579,[Chapter 15,Heading 15.3.4 & 15.3.6]

(b)(i)Kelvin bridge for the measurement of low resistance.(8)

• Circuit Diagarm(3) • Condition of Balanced Bridge+ Assumptions(1) • Derivation for finding Unknown resistance(4) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 534,535,[Chapter 14,Heading 14..3.2]

(ii)Hays bridge (8) • Circuit Diagarm(3) • Condition of Balanced Bridge+ Assumptions(1) • Derivation for finding Unknown inducatance(4) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004 • Page no- 591,[Chapter 16,Heading 16.5.3] 14. (a) (i) Construction and working principle of X-Y Recorder(6)

• Diagram(2) • Construction & Woking(4)

Refer text book by Kalsi, H.S., “Electronic Instrumentation”, Tata McGraw Hill, 2004.

• Page no- 382 to 384,[Chapter 12,Heading 12.6)

(ii) Features of digital plotters and printers. (10)

• Explanation of Digital plotters(5) Refer text book by Kalsi, H.S., “Electronic Instrumentation”, Tata McGraw Hill,

2004. • Page no- 384,[Chapter 12,Heading 12.6.1 ) • Explanation of printers(5) Refer text book by Kalsi, H.S., “Electronic Instrumentation”, Tata McGraw Hill,

2004. • Page no- 55 ,[Chapter 2,Heading 2.13,2.16,2.17,2.18,2.19 ) b. (i)Electrostatic deflection system • Diagram(4) • Explanation(6) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 787 to 790[Chapter 21,Heading 21.5 &21.6]

ii) Digital storage oscilloscope: • Diagram(2) • Explanation(4) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 825 to 827,[Chapter 21,Heading 21.24.1]

15.a.(i) Construction and working of unbounded and bonded type strain gauges • Diagram(2+2) • Explanation(2+2) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

• Page no- 966 & 967,[Chapter 25,Heading 25.17.1 &25.17.12 ] (ii)construction and working of optical encoders

• Diagram(4) • Explanation(4) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

Page no- 1059 to1064,[Chapter 25,Heading 25.36] b.(i) Block diagram of a digital data acquisition system

• Block Diagram(3) • Explanation(5) Refer text book by Kalsi, H.S., “Electronic Instrumentation”, Tata McGraw Hill,

2004. • Page no- 626 to 628 ,[Chapter 17,Heading 17.1]

(ii) Successive approximation method of A/D converter • Diagram(4) • Explanation(4) For explanation refer the text book- Sawhney A.K., “A course in Electrical & Electronics Measurement and Instrumentation”,Dhanpat Rai & Co., 2004

Page no- 1188 to 1190,[Chapter 26,Heading 26.28.1]