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DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

EE2201-Measurements and Instrumentation
Two mark Question & Answer
UNIT I - INTRODUCTION
1. What is meant by measurement?
Measurement means an act or the result of comparison between the quantity and a
predefined standard.
2. Mention the basic requirements of measurement.
The basic requirements of measurement are
i. The standard used for comparison purpose must be accurately defined and
should be commonly accepted.
ii. The apparatus used and the method adopted must be provable.
3. State the two methods for measurement.
The two methods of measurement are
i. Direct method and
ii. Indirect method.
4. State 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. List the three types of instruments.
The three types of instruments are:
i. Mechanical Instruments
ii. Electrical Instruments and
iii. Electronic Instruments.
6. Classify the instrument based on their functions.
Instruments are classified into three types based on their functions. They are
i. Indicating instruments
ii. Integrating instruments
iii. Recording instruments
7. Give any three applications of measurement systems.
The applications of measurement systems are
i. Monitoring of processes and operations.
ii. Control of processes and operations.
iii. Experimental engineering analysis.
SARASWATHI VELU COLLEGE OF ENGINEERING - SHOLINGHUR


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8. 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.

9. List 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.

10. Define: Calibration
Calibration is defined as the process by which comparing the instrument with a standard
to correct the accuracy.

11. Mention the functions performed by the measurement system.
The functions performed by the measurement system are
i. Indicating function
ii. Recording function
iii. Controlling function

12. List the functional elements of the measurement systems.
The three main functional elements of the measurement systems are:
i. Primary sensing element
ii. Variable conversion element
iii. Data presentation element

13. Write the characteristics of the measurement system.
Characteristics of measurement system is divided into two categories:
i. Static characteristics
ii. Dynamic characteristics

14. Write the main static characteristics?
The main static characteristics are:
i. Accuracy
ii. Sensitivity
iii. Reproducibility
iv. Drift
v. Static error
vi. Dead zone
vii. Resolution
viii. Precision
ix. Repeatability
x. Stability



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15. Define static error
Static error is defined as the difference between the true value and the
measured value of the quantity.
Static error = A
t
A
m
where A
m
=measured value of quantity
A
t
=true value of quantity.

16. Define resolution
Resolution is defined as the smallest increment of quantity being measured which can be
detected with certainty being measured which can be detected with certainty by an
instrument.

17. Define threshold
Threshold is defined as the minimum value of the input at which the output starts
changing/increasing from zero.

18. Define linearity
The linearity is defined as the ability to reproduce the input characteristics symmetrically
and linearly.

19. Define reproducibility
Reproducibility is defined as the degree of closeness with which a given
value may be repeatedly measured. It is specified in terms of scale readings
over a given period of time.

20. Define drift
Drift is defined as slow variation of reading from a fixed value.

2 21 1. . D De ef fi in ne e s sp pe ee ed d r re es sp po on ns se e
Speed response is defined as the rapidity with which a measurement system responds to
changes in measured quantity. It is one of the dynamic characteristics of a measurement
system.

22. D De ef fi in ne e f fi id de el li it ty y
Fidelity is defined as the degree to which a measurement system indicates changes in the
measured quantity without any dynamic error.

23. Define dynamic error
Dynamic error is defined as the difference between the true value of the quantity
changing with time and the value indicated by the measurement system if no static error is
assumed. It is also called measurement error. It is one the dynamic characteristics.

24.Define retardation delay
Retardation delay is defined as the retardation delay in the response of a measurement
system to changes in the measured quantity.



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25. Define time delay
Time delay is defined as the response of the measurement system begins after a dead
zone after the application of the input.

UNIT II - ELECTRICAL AND ELECTRONIC INSTRUMENT

1. Name the types of instruments used for making voltmeter and ammeter.
The types of instruments used for making voltmeter and ammeter are
i. PMMC type
ii. Moving iron type
iii. Dynamometer type
iv. Hot wire type
v. Electrostatic type
vi. Induction type.

2. State the advantages of PMMC instruments.
The advantages of PMMC instruments are:
i. Uniform scale
ii. No hysterisis loss
iii. Very accurate
iv. High efficiency

3. State the disadvantages of PMMC instruments.
The disadvantages of PMMC instruments are
i. Cannot be used for ac measurements
ii. Some errors are caused by temperature variations

4. State the applications of PMMC instruments.
The applications of PMMC instruments are
i. Measurement of D.C voltage and current
ii. Used in D.C galvanometer.

5. How the range of instrument can be extended in PMMC instruments?
The range of PMMC instrument can be extended by
i. connecting a shunt resistor
ii. connecting a series resistor.

6. State the advantages of dynamometer type instruments.
The advantages of dynamometer type instruments are
i. They Can be used for both D.C and A.C measurements
ii. Free from hysterisis and eddy current errors.
7. State the advantages of moving iron type instruments.
The advantages of moving iron type instruments are:
i. Less expensive
ii. Can be used for both DC and AC
iii. Reasonably accurate.


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8. State the advantages of Hot wire type instruments.
The advantages of Hot wire type instruments are:
i. They can be used for both dc and ac
ii. They are unaffected by stray magnetic fields
iii. Readings are independent of frequency and waveform.

9. What are the constructional parts of dynamometer type wattmeter?
The constructional parts of dynamometer type wattmeter are:
i. Fixed coil
ii. Moving Coil
iii. Current limiting resister
iv. Helical spring
v. Spindle attached with pointer
vi. Graduated scale

10. State the disadvantages of dynamometer type wattmeter.
The disadvantages of dynamometer type wattmeter are:
i. Readings may be affected by stray magnetic fields.
ii. At low power factor it causes error.

11. Name the errors caused in dynamometer type wattmeter.
The errors caused in dynamometer type wattmeter are:
i. Error due to pressure coil inductance
ii. Error due to pressure coil capacitance
iii. Error due to methods of connection
iv. Error due to stray magnetic fields
v. Error due to eddy current.

12. Name the methods used for power measurement in three phase circuits.
The methods used for power measurement in three phase circuits are:
i. Single wattmeter method
ii. Two wattmeter method
iii. Three wattmeter method.

13. What are the special features to be incorporated for LPF wattmeter?
The special features to be incorporate for LPF wattemeter are:
i. Pressure coil circuit
ii. Compensation for Pressure coil current
iii. Compensation for Pressure coil inductance.

14. Name the methods used in wattmeter calibration.
The methods used in wattmeter calibration are:
i. Comparing with standard wattmeter.
ii. Using voltmeter ammeter method.
iii. Using Potentiometer.


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15. Name the constructional parts of induction type energy meter.
The constructional parts of induction type energymeter are:
i. Current coil with series magnet
ii. Voltage coil with shunt magnet
iii. Al disc
iv. Braking magnet
v. Registering mechanism.

16. How voltage coil is connected in induction type energy meter?
Voltage coil is connected in parallel to supply and load in induction type energy meter.

17. How current coil is connected in induction type energy meter?
Current coil is connected in series to the load in induction type energy
meter.

18. Why aluminium disc is used in induction type energy meter?
Aluminium disc is used in induction type energy meter because it is a
nonmagnetic metal.

19. What is the purpose of registering mechanism?
The purpose of registering mechanism is to record the energy proportional to the
rotations.

20. Define creeping.
Creeping is defined as slow but continuous rotation of disc when pressure
coil is energized and current coil is not energized.

21. State the reason why holes are provided in aluminium disc.
Holes are provided on both sides of aluminium disc to avoid creeping.


















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UNIT III - COMPARSION METHODS OF MEASUREMENT

1. What is the basic principle used in potentiometer?
Basic principle used in potentiometer is that the unknown emf is measured
by comparing it with a standard known emf.

2. Name the materials used in potentiometer.
The materials used in potentiometer are
i. German silver
ii. Manganin wire

3. State the applications of potentiometer.
The applications of potentiometers are
i. measurement of unknown emf
ii. ammeter calibration
iii. Voltmeter calibration
iv. wattmeter calibration

4. State the advantages of crompton potentiometer.
The advantages of crompton potentiometer are:
i. More accuracy
ii. Easy to adjust

5. What are the practical difficulties in A.C potentiometers?
The practical difficulties in A.C potentiometers are:
i. More complicated
ii. Accuracy is seriously affected
iii. Difficulty is experienced in standardization.

6. Classify AC potentiometers.
AC potentiometers are classified as
i. Polar potentiometer
ii. Coordinate potentiometer.

7. How the phase angle is measured in polar type potentiometers?
The phase angle is measured in polar type potentiometers from the position of phase
shifter.

8. List any two AC potentiometers.
The two AC potentiometers are
i. Drysdale Tinsley potentiometer
ii. Gall Tinsley potentiometer.

9. State the advantages of AC potentiometers.
The advantages of ac potentiometers are
i. They can be used for measurement of both magnitude and phase angle


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ii. They can be used for measurement of inductance of the coil.
iii. They are used in measurement of errors in current transformers.

10. State the applications of AC potentiometers.
The applications of AC potentiometers are
i. Measurements of self inductance.
ii. Ammeter calibration
iii. Voltmeter calibration
iv. Wattmeter calibration.

11. State the advantages of instrument transformers.
The advantages of instrument transformers are
i. Used for extension of range
ii. Power loss is minimum
iii. High voltage and currents can be measured.

12. State the disadvantage of instrument transformers.
The disadvantage of instrument transformers is that they cannot be used for
DC measurements.

13. What are the constructional parts of current transformer?
The constructional parts of current transformer are
i. Primary winding
ii. Secondary winding
iii. Magnetic core.

14. Name the errors caused in current transformer.
The errors caused in current transformer are
i. Ratio error
ii. Phase angle error

15. Define ratio error
Ratio error is defined as the ratio of energy component current and secondary current.

16. How the phase angle error is created?
The phase angle is created mainly due to magnetizing component of excitation current.

17. State the use of potential transformer.
The use of potential transformer are
i. They are used for measurement of high voltage
ii. They are used for energizing relays and protective circuits.

18. How the current transformer and potential transformer are connected in a circuits?
In a current transfrmer is connected in series and potential transformer is connected in parallel




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19. What is the range of medium resistance?
The range of resistance is about 1 ohm to 100 kilo ohms.

20. Name the methods used for low resistance measurement.
The methods used for low resistance measurement are
1. Ammeter voltmeter method
2. Potentiometer method
3. Kelvin double bridge method
4. Ohm meter method.

21. What are the types of DC potentiometers?
The types of DC potentiometers are
i. Cromptons Potentiometer
ii. Duo-Range Potentiometer
iii. Vernier Potentiometer
iv. Brooks Deflectional Potentiometer

22. What is a bridge circuit?
A bridge circuit consists of a network of four impedance
arms forming a closed circuit. A source of current is applied to two opposite
junctions. The current detector is connected to other two junctions.


23. What are the types of bridges?
The types of bridges are:
i. DC bridge
ii. AC bridge

24. What are the types of DC bridges?
The types of DC bridges are
i. Wheatstone bridge
ii. Kelvin Double bridge

25. What are the types of AC bridges?
The types of AC bridges are
i. Capacitance comparison bridge
ii. Inductance comparison bridge
iii. Schering bridge
iv. Maxwells Inductance and capacitance bridge
v. Hays bridge
vi. Anderson bridge
vii. Wien bridge
26. Classify the cables according to their sheathing.
According to their sheathing cables are classified as
i. Armoured cables
ii. Unarmoured cables.


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27. State the advantages of prices guard wire method.
The advantage of prices guard method is leakage current does not flow through the
meter and therefore it gives accurate reading.

28. How the earth resistance is measured?
Earth resistance can be measured by using earth megger.

29. Which type of detector is used in ACbridges?
The detectors used in AC bridges are
i. Vibration galvanometers
ii. Tunable amplifier
iii. Head phones

30. Name the sources of errors in AC bridge measurements.
The sources of errors in AC bridges are
i. Errors due to stray magnetic fields
ii. Leakage errors
iii. Eddy current errors
iv. Residual errors
v. Frequency and waveform errors.

31. State the advantages of wein bridge.
The advantage of wien bridge is the balance equation is independent of frequency and
therefore is more accurate.

32. State the disadvantage of wein bridge.
The disadvantage of wien bridge is a standard variable capacitor. Variable capacitor is
more costly.

33. State the disadvantages of Hays bridge.
The disadvantages of Hays bridge is the balance equation is dependent of frequency and
therefore any changes in frequency will affect the measurement.

34. State the use of Wein bridge.
Wien bridge is used for the measurement of unknown capacitance and
frequency.

35. Define: Q-factor of the coil
Q-factor of the coil is defined as the ratio of power stored in the coil to the
power dissipated in the coil.
36. Name the faults that occurs in cables.
Faults that occur in cables are
i. Break down of cable insulation
ii. Short circuit fault
iii. Open conductor fault.


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37. Name the loop test methods used in location of fault.
Loop test methods used in location of fault is
i. Murray loop test
ii. Varley loop test.

UNIT-IV
STORAGE AND DISPLAY DEVICES

1. List the components of a magnetic tape recorder.
The components of a magnetic tape recorder are :
i. Recording head
ii. Magnetic head
iii. Reproducing head
iv. Tape transport mechanism
v. Conditioning devices.

2. What are the advantages of magnetic tape recorders?
The advantages of magnetic tape recorders are :
i. They have a wide frequency range from D.C. to several MHz.
ii. They have low distortion,
iii. They have a wide dynamic range which exceeds 50dB. This permits the linear recording
from full scale signal level to approximately 0.3% of full scale.
iv. The magnitude of the electrical input signal is stored in magnetic memory and this signal
can be reproduced whenever desired. The reproduced signal can be analyzed by
automatic data reduction methods.

3. Mention the different methods of magnetic tape recording.
The different methods of magnetic tape recording are :
i. Direct recording
ii. Frequency modulation (FM) recording and
iii. Pulse duration modulation (PM) recording

4. Mention is the purpose of erase head.
The purpose of erase head is to erase the content of magnetic tae. It consists of a signal
of high frequency and level sweeps the magnetic tape thereby completely wiping out the
information contained there. This renders the magnetic tape to be used fresh for another signal.

5. List the advantages of direct recording.
The advantages of direct recording are:
i. This recording process has a wide frequency response ranging from 50
Hz to about 2 MHz for a tape speed of 3.05 m/s. It provides the
greatest bahdwidtn obtainable from a given recorder.
ii. It requires only simple, modulately priced electronic circuitry.


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iii. It is used to record signals where information is contained in the
relation between frequency and amplitude, such as spectrum analysis
of noise.
iv. It can be used for recording voice and in multiplexing a number of
channels of information into one channel of tape recording.

6. Mention the disadvantages of direct recording.
The disadvantages of direct recording are:
i. Direct recording is used only when maximum bandwidth is required
and when variations in amplitude are acceptable.
ii. Direct recording can be used for instrumentation purposes but it is
mainly used for recording of speech and music.

7. What is drop out ?
In direct recording, some portions of the tape may not be perfectly recorded owing to dirt
or poor manufacture and this is called drop out.

8. Mention the two factors in frequency modulation recording.
The two factors in frequency modulation recording are:
i. Percentage deviation and
ii. Deviation ratio.

9. Define: percentage deviation
Percentage deviation is defined as the carrier deviation to centre frequency.
i.e. Percentage deviation or modulation index, m =(f/f
c
) x 100,
where f = carrier deviation from centre frequency
f
c
= centre or carrier frequency

10. Define: Deviation ratio
Deviation ratio is defined as the ratio of carrier deviation from centre
frequency to signal or modulating frequency.
Deviation ratio, = (f/f
m
)
where, f
m
= data signal

11. Give few advantages of frequency modulation recording.
The advantages of frequency modulation recording are :
i. It is useful when the D.C. component of the input signal is to be preserved or
when the amplitude variations of the direct recording process cannot be
tolerated.
ii. This system has wide frequency range can record from D.C. voltages to
several kHz.
iii. It is free from dropout effect.
iv. It is independent of amplitude variations and accurately reproduces the
waveform of the input signal.
v. It is used extensively for recording the voltages from the force, pressure and
acceleration transducers.


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vi. It is extremely used for multiplexing in instrumentation systems.

12. List few disadvantages of frequency modulation recording.
The disadvantages of frequency modulation recording are :
i. The circuitry of an FM recording system is more complicated than that of a
direct recording system. This complexity of circuitry is an account of separate
modulation systems.
ii. It has a limited high frequency of about 80 kHz.
iii. It requires a high tape speed.
iv. It requires a high quality of tape transport and speed control and therefore
expensive than the direct recording system.

13. Enumerate the merits and demerits of pulse width modulation recording.
The merits of pulse width modulation recording are :
It has the ability to simultaneously record information from a large number of channels.
It has a high accuracy due to the fact that it can be self-calibrated.
It has a high 3/N ratio.
The demerits of pulse width modulation recording are :
It has the limited frequency response
It has a highly complex electronic circuitry and therefore, the reliability of such systems
are low.
It is used only for special applications such as flight recorders, where a large number of
slowly changing variables are involved.

14. What is the operation of a serial printer ?
The operating of serial printer is to produces a single character at a time, usually moving
from left to right across a page. It prints 200 characters per second.


15. Mention the purpose of line printers.
The line printers are used to print line by line instead of characters. It prints
4000 lines per minute.


16. Give the operation of page printer.
The purpose page printer prints a line at time mode, but can be stopped and restarted
only on the page basis. The top Speed is 45,000 lines per minute.

17. List the classification of printer.
Printers are classified into three brad categories. They are
i. Impact and non-impact printers.
ii. Fully formed character and dot matrix character
printer
iii. Character at a time and a line at time.




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19. What is impact and non-impact printers ?
Impact printers form characters on a paper by striking the paper with a print
head and squeezing an inked ribbeia between the print head and paper.
Non-impact printers form characters without engaging the print mechanism
with the print surface i.e. by heating sensitised paper or by spraying ink from a
jet.

20. Write short notes on printer character set.
Mini and micro computers use ASCII codes for the printers. They are specified using the
48 character set, the 64 character set, the 96 character set or the 128 character set. The entire 128
character ASCII set contains 32 characters normally used for communication and control.




21. 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 bidirectional printing.

22. 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, number or other symbol. It can print any combination of dots with all availble print
position in the matrix.

23. List the important features of CRTs.
The important features of CRTs are :
i. Size
ii. Phosphor
iii. Operating voltages
iv. Deflection voltages
v. Viewing screen

24. What is meant by deflection sensitivity in cathode ray tube ?
The deflection sensitivity of the cathode ray tube is usually stated as the D.C. voltage
required for each cm of deflection of the spot on the screen,

25. List the requirements of a sweep generator.
The requirements of a sweep generator are :
i. The sweep must be linear.
ii. The spot must move in one direction only, i.e. from left to right only, else the
signal will be traced backwards during the return sweep. This means that the
sweep voltage must drop suddenly after reaching its maximum value. These
requirements call for a sweep voltage having a linear sawtooth waveform.




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26. What is meant by recurrent sweep in cathode ray tube ?
When the sawtooth, being an A.C. 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.

27. What is intensity modulation in CRT?
In some applications, an A.C. signal is applied to the control electrode of the CRT. This
causes the intensity of the beam to vary in step with signal alterations. As a result, the trace is
brightened during the positive half cycle and diminished or darkened during negative half cycle.
This process is called intensity modulation or z-axis modulation. It produces bright segments or
dots on the trace in response to positive peak or dim segments or holes in response to negative
peaks.

28. Mention the methods that are used for generating the two electron beams within the
CRT.
The methods that are used for generating the two electron beams within the CRT are the
double gun tube and split beam method.

29. Mention the two storage techniques used in oscilloscope CRTs.
The two storage techniques used in oscilloscope CRTs are mesh storage and phosphor
storage.

30. CRO has become an universal tool in all kinds of electrical and electronic investigation.
Why ?
CRO has become an universal tool in all kinds of electrical and electronic investigations
because in CRO, the vertical input voltage is the voltage under investigation and it moves the
luminous spot up and down in accordance with the instantaneous value of the voltage. When the
input voltage repeats itself at a fast rate, the trace (display) on the screen, appears stationary on
the screen.

31. Name the components of a CRO.
The Components of CRO are:
i. cathode ray tube (CRT) along with electron gun assembly
ii. deflection plate assembly
iii. fluorescent screen
iv. glass envelope and
v. base.

32. What is an electon gun ?
An electon gun is the source of focussed 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 focussing anode and an accelerating anode.

33. Name the basic circuitry of CRO.
The basic circuitry of CRO are named as :
i. Vertical (Y) deflection system


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ii. Horizontal (X) deflection system
iii. Synchronization iv. Blanking circuit
iv. Intensity (z-axis) modulation
v. Positioning controls
vi. Focus control
vii. Intensity control
viii. Calibration control
ix. Astigmatism.

34. Write notes on dual trace cathode ray oscilloscopes.
In a dual trace CRQ, there are two separate vertical input channels A and B and these use
separate attenuator and preamplifier stages. Hence the amplitude of each input as viewed on the
oscilloscope can be individually controlled, after preamplification, the two channels meet at an
electronic switch and this has the ability to pass one channel at a time into the vertical amplifier
via the delay line.

35. State the purpose of a lissajous pattern in CRO.
The lissajous pattern is used for determining the frequency. The particular pattern results
when sine waves are applied simultaneously to both pairs of the deflection plates.

36. What is a LED ?
The LED is basically a semiconductor PN junction diode capable of emitting
electromagnetic radiation under forward conductions.

37. List the different materials used in manufacturing LEDs
The different materials used in manufacturing LEDs are
i. Gallium Arsenide (GaAs) - red
ii. Gallium Arsenide Phosphide (GaAsP) - red or yellow
iii. Gallium Phosphide (GaP) - red or green.

38. How are LCDs created ?
LCDs are created by sandwitching a thin (10 to 12um) layer of a liquid-crystal fluid
between two glass plates. A transparent, electrically conductive film or backplane is put on the
rear glass sheet. Transparent sections of conductive film in the shape of the deviced character are
coated on the front glass plate. When a voltage is applied between a segment and the backplane,
an electric field is created in the region under the segment. This electric field change the
transmission of light through the region under the segment film.

39. List the characteristics of LCD.
The characteristics of LCD are :
i. They are light scattering.
ii. They can operate in a reflective or transmissive configuration.
iii. They do not actively generate light and depend for their operation on ambient or back
lighting.

40. Name the two commonly available types of LCDs.


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The two commonly available types of LCDs are :
i. Dynamic scattering and
ii. Field effect type

41.State the purpose of dot matrix displays.
Excellent alphanumeric characters can be displayed by using dot matrix
LEDs with an LED at each dot location.

42. Write the two writing patterns of dot matrix displays.
The two wirting patterns of dot matrix displays are :
i. Common anode or common cathode connection (uneconomical).
ii. X-Y array connection (economical and can be extended vertically or
horizontally using a minimum number of wires).
































UNIT-V


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TRANSDUCERS

1. Define: Transducer
A transducer is defined as a device that receives energy from one system and
transmits it to another, often is a different form.

2. Write the parameters of electrical transducer.
The parameters of electrical transducer are:
i. Linearity
ii. Sensitivity
iii. Dynamic range
iv. Repeatability
v. Physical size

3. List the advantages of electrical transducers.
The advantages of electrical transducers are:
i. Electrical amplification and attenuation can be easily done.
ii. Mass-interia effects are minimized.
iii. Effects of friction are minimized.
iv. Using very small power level.
v. Electrical output can be easily used, transmitted and processed for the purpose of
measurement.
vi. The output can be indicated and recorded remotely at a distance from the sensing
medium.

4. Define: Viscosity
Viscosity is defined as the property which determine the magnitudes of the
resistance of the fluid to a shearing force.

5. Give the types of potentiometer.
The types of potentiometer are:
i. Translatory
ii. Rotational
iii. Helipot

6. Give the limitations of thermistor.
Limitations of thermistor are:
i. Non-linearity in resistance Vs temperature characteristics.
ii. Unsuitable for wide temperature range.
iii. Very low excitation current to avoid self-heating.
iv. Need of shielded power lines, filters etc., due to high resistance.

7. In what principles,inductive transducer works?
i. Variation of self-inductance.
ii. Variation of mutual-inductance.



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8. Write a short notes on LVDT.
LVDT(Linear Variable Differential Transformer) converts the mechanical
energy into differential electrical energy. It has single primary winding, and two
secondary windings wound on a hollow cylindrical former. An movable soft
iron core slides within the hollow former and therefore affects the magnetic
coupling between the primary and the two secondaries.

9. List the advantages of LVDT.
The advantages of LVDT are:
i. High range of displacement measurement.
ii. Friction and electrical isolation.
iii. Immunity from external effects.
iv. High input and high sensitivity.
v. Ruggedness
vi. Low hysteresis and low power consumption.

10. List the limitations of LVDT.
The limitations of LVDT are:
i. Large displacements are required for appreciable differential output.
ii. They are sensitive to stray magnetic fields.
iii. Dynamic response is limited.
iv. Temperature also affects the transducer.

11. List the two physical parameters in strain gauge.
The two physical parameters in strain gauge are:
i. The change in gauge resistance.
ii. The change is length.

12. List out the features of piezo-electric accelerometer.
The features of piezo-electric accelerometer are:
i. Instrument is quite small in size and has a low weight.
ii. The natural frequency is very high.
iii. Useful for high input frequencies and the response is poor at low frequencies.
iv. The crystal is a source with a high output impedance and in order to avoid loading
effect, a voltage monitoring source of a high input impedance should be used.

13. Define: Inductive Transducer
Inductive transducer is defined as a device that converts physical motion into
a change in inductance. It may be either of active or passive type.

14. Give the principle of capacitive transducers.
Capacitive transducer principle is a linear change in capacitance with changes in the
physical position of the moving element may be used to provide an electrical indication of the
elements position.
C=KA/d
Where K= dielectric constant.


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A= total area of capacitor surfaces.
d = distance between two capacitive surfaces.

15. What is meant by digital transducers?
Digital transducers are also called as encoders. They are normally in the form of linear or
rotary displacement transducers. Hence they require analog to digital converter to realize the
digital data.

16. Classify digital transducers.
Digital transducers are classified into,
i. Tachometer transducers
ii. Incremental transducers
iii. Absolute transducers