Measurements and Instrumentation

1. MEASUREMENTS AND INSTRUMENTATION
UNIT – I
INTRODUCTION
1. Describe the functional elements of an instrument with its block diagram. And illustrate them
with pressure gauge, pressure thermometer and D’Arsonval galvanometer. (16)
2. What are the three categories of systematic errors in the instrument and explain in detail. (16)
3. (i) What are the basic blocks of a generalized instrumentation system? Draw the various
blocks and explain their functions. (10)
(ii) Explain in detail calibration technique and draw the calibration curve in general. (6)
4. (i) Discuss in detail various types of errors associated in measurement and how these
errors can be minimized? (10)
(ii) Define the following terms in the context of normal frequency distribution of data (6) a)
Mean value, b) Deviation, c) Average deviation, d) Variance e) Standard deviation.
5. (i) Define and explain the following static characteristics of an instrument. (8)
a) Accuracy, b) Resolution, c) Sensitivity and d) Linearity
(ii) Define and explain the types of static errors possible in an instrument. (8)
6. Discuss in detail the various static and dynamic characteristics of a measuring system. (16)
7. (i) For the given data, calculate
a) Arithmetic mean, b) Deviation of each value, c) Algebraic sum of the deviations (6) X1
= 49.7, X2 = 50.1, X3 = 50.2, X4 = 49.6, X5 = 49.7 (ii) Explain in detail the types of static
error. (7)
(iii) Give a note on dynamic characteristics. (3)
8. (i) What is standard? Explain the different types of standards? (8)
(ii) What are the different standard inputs for studying the dynamic response of a system?
Define and sketch them. (8)
9. a) Define resolution. (4) b) What is threshold? (4)
c) Define zero drift. (4) d) What are random errors? (4)
10. Explain the Normal or Gaussian curve of errors in the study of random effects. (16)

2. UNIT – II
ELECTRICAL AND ELECTRONICS INSTRUMENTS
1. (i) Describe the construction and working of a permanent magnetic
moving coil instruments. (10)
(ii) Explain the design of three phase wattmeters and give the
reactive power measurement in 3 phase circuits. (6)
2. (i) How B-H curve is determined for a ring specimen. (8)
(ii) Explain the frequency measurement in Wien’s bridge (8)
3. Discuss why it is necessary to carry out frequency domain analysis of
measurement Systems? What are the two plots obtained when the frequency
response of a system is carried out? (16)
4. Explain the function of three phase wattmeter and energy meter. (16)
5. (i) Sketch the circuit and waveforms for ac voltmeter using a PMMC
Instrument and half wave rectifier. Explain the circuit operation. (10)
(ii) Develop the torque equation for a PMMC instrument and show its scale
is linear (6)
6. (i) Discuss in detail the working of the successive approximation
DVM.(8)
(ii) With a neat diagram, explain the various methods of magnetic measurements.
(8)
7. (i) Explain with a neat sketch the construction and working principle of
single-phase induction type energy meter. (10)
(ii) How the range of d.c ammeter and d.c voltmeter can be extended?
Derive the expressions to calculate shunt resistance and multiplier resistance. (6)
8. (i) With a neat diagram explain the construction and working of
electrodynamometer type instruments. Also derive its torque equation. (10)
(ii) Explain with neat diagram the working of linear ramp type DVM. (6)
9. (i) Explain the different methods of determination of B –H curve (8)
(ii) With block diagram explain the working principle of digital
frequency meter. (8)
10. (i) Explain the working principle of moving iron instrument. (8)
(ii) Give detailed notes on Instrument transformers. (8)

3. UNIT-III
COMPARISON METHODS OF MEASUREMENTS
1. Explain in detail about the laboratory type DC potentiometer. (16)
2. Describe about the multiple earth and earth loops. (16)
3. Explain voltage sensitive self balancing bridge, and derive the bridge
sensitivity of voltage sensitive bridge with fundamentals. (16)
4. With fundamentals distinguish between DC and AC potentiometers, and
give any two specific applications for each. (16)
5. Discuss the advantages and limitations of electromagnetic interference in
measurements. (16)
6. Explain Kelvin’s double bridge method for the measurement of low resistance.
(16)
7. Explain how inductance in measured by using Maxwell’s bridge. (16)
8. Explain the working principle of Anderson’s bridge and also derive its balance
equations. (16)
9. Explain the working principle of Schering Bridge and also derive its balance
equations. (16)
10. (i) Give the applications of AC potentiometers. (8)
(ii)Explain the different techniques of grounding. (8)
UNIT- IV
STORAGE AND DISPLAY DEVICES
1. Describe the construction and working of LCDs, mention the difference
between light scattering and field effect types of LCDs, and also explain the
advantages of LCDs (16)
2. Give the basic block diagram of a digital data recording system (16)
3. (i) Explain the basic elements of a magnetic tape recorder. (8)
(ii) Explain the block diagram of oscilloscope with a neat sketch (8)
4. (i) Describe the basic components of a CRT. (10) (ii) Write short notes on
liquid crystal displays. (6)
5. (i) With a neat block diagram, explain the working of digital storage

4. oscilloscope. (8) (ii) Discuss briefly about the applications of LED. (8)
6. (i) What are the various types of oscilloscopes? (4)
(ii) Discuss in detail the construction of a storage type oscilloscope.
What are the accessories for a CRO? (12)
7. (i) Explain in detail, how the data is stored in a magnetic disk and tape? (10)
(ii) Describe the performance of digital plotter. (6)
8. (i) Explain the block diagram of a general purpose oscilloscope and also
describe about
the observation of waveform on CRO. (10)
(ii) Write short notes on Printers. (6)
9. a) List out the advantages of X-Y records over strip chart recorder. (4)
b) List the advantages of laser printer. (4)
c) List the two advantages of digital X-Y recorder. (4)
d) What is power requirement of LCD? (4)
e) Explain with a neat sketch
f) a) Dot matrix displays (8) b) Bar graph displays(8)
UNIT – V
TRANSDUCERS AND DATA ACQUISITION SYSTEMS
1. (i) Explain the principle of inductive and capacitive
transducer. (8)
(ii) Explain the construction and working of LVDT with a neat sketch (8)
2. (i) Explain different strain gauges with their principle of operation. (8)
(ii) Discuss in
detail about resistive transducers. (8)
3. (i) Explain the various types of temperature transducers. (8) (ii) Explain the
function of piezoelectric transducer. (8)
4. (i) Explain the binary weighted resistor technique of D/A conversion.(8)
(ii) Define the following terms for D/A converters:
a) Resolution b) Accuracy c) Monotonicity and d) conversion time (8)
5. (i) Explain the resistive transducer with respective to potentiometer. (4) (ii)
Explain the capacitive transducer. (6)
(iii)Describe the piezoelectric transducer and give the formula for coupling
coefficient. (6)
6. (i) Explain schematic block diagram of a general data acquisition system
(DAS) and give its objectives (6)
(ii)Discuss R-2R ladder type D/A converter. (6)
(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)

5. 7. Explain the various types of ADC with suitable sketches. (16)
8. Explain the working principle of various types of DAC with neat sketches. (16)
9. (i) Explain the principle of operation a thermocouple with neat sketch. (10)
(ii)Give a short note on single and multi channel DAS. (6)
10. (i) Explain the different types of optical encoders. (8)
(ii) Explain the successive approximation type ADC. (8)
Measurements & Instrumentation
UNIT III - Comparison Methods of Measurements
1. What is potentiometer?
A potentiometer is an instrument designed to measure an unknown voltage by comparing it with a known
voltage.
2. Mention the applications of potentiometers.
i) Measurement of small emfs (up to 2V) ii) Comparison of emf of two cells iii) Measurement of high emfs (up to
250V) iv) Measurement of resistance v) Measurement of current.
3. What are the types of potentiometer?
D.C potentiometer & A.C potentiometer.
4. What are the types of DC potentiometer?
Simple potentiometer. , Direct reading potentiometer. , Crompton potentiometer. , Modern form of slide wire
potentiometer.
5. What is the main difference between in operation between DC potentiometer and AC potentiometer?
In the DC potentiometer only the magnitude of the unknown emf and slide wire voltage drop must be made
equal to obtain balance, where as in the AC potentiometer the phases of the two voltages, as well as their
magnitudes, must be equal for balance to be obtained.
6. What are the types of AC potentiometers?
Polar potentiometer. & Co ordinate potentiometer
7. Mention some applications of AC potentiometers.
Measurement of self inductance, Calibration of ammeter, Calibration of voltmeter, & Calibration of wattmeter.
8. Draw Maxwell’s AC Bridge and give the balance equation in terms of resistance.
Rx = (R2/R1) (R3 + r)
Advantages of Maxwell's Bridge:
1. The frequency does not appear in the final expression of both equations; hence it is independent of
frequency.
2. Maxwell's inductor capacitance bridge is very useful for the wide range of measurement of
inductor at audio frequencies.

6. Disadvantages of Maxwell's Bridge
1. The variable standard capacitor is very expensive.
2. The bridge is limited to measurement of low quality coils (1 < Q < 10) and it is also unsuitable for
low value of Q (i.e. Q < 1) from this we conclude that a Maxwell bridge is used suitable only for
medium Q coils.
9. Give some applications of Wheatstone’s bridge.
Wheatstone bridge is used for measurement of medium resistances in the range of 1Ω to 100 k Ω.
Unknown Resistance RX = R3 × (R2 / R1).
a) Wheatstone bridge is used for measuring the very low resistance values precisely.
b) Wheatstone bridge along with operational amplifier is used to measure the physical parameters like
temperature, strain, light, etc.
c) We can also measure the quantities capacitance, inductance and impedance using the variations on the
Wheatstone bridge.
10. What are the sources of errors in bridge measurement?
Errors due to stray magnetic fields, Leakage errors, Eddy current errors, Residual errors, Frequency and
waveform errors.
11. What is meant by transformer Ratio Bridge.
Transformer Ratio Bridge uses ratio transformer which is highly accurate and versatile. Its basic form
consists of voltage transformer which is an auto transformer. The numbers of tappings are provided to obtain
to voltage division. It behaves as an ideal transformer.
12. What are the features of ratio transformer? List its applications.
They have very small ratio errors. Almost behave as ideal transformers, can be operated over wide frequency
range from 50 Hz to 50 kHz., have e high input impedance, low output impedance to avoid loading effects.
Applications: Measurement of Amplifier gain, Phase shift, transformer ratios, Measurement of R, Land C in
comparison with standard R, L and C respectively.
13. What is meant by electromagnetic interference?
Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio
frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit
by electromagnetic induction, electrostatic coupling, or conduction.
14. List the sources of electromagnetic interference.
Welding equipment, Inductive or capacitive coupling & AC power circuits, radio frequency transmitters,
Gas discharges in fluorescent tubes, Arcing in electric generators, Sparking in electric switches, Signals
from TV radars and radio transmitters
15. What are the ways of minimizing the electromagnetic interference?
Use twisted-pair, shielded signal lines, and connecting shields on both ends. Internal filtering to reduce effects of
electrical noise. Ensure good connections between the cabinet components
16. What are the main causes of group loop currents?
Potential difference between the points of ground where the ground terminals are connected. ii) Due
to stray magnetic field and radio frequency waves there can be inductive pick up
17. What are the limitations of single point grounding method?
The systems in which various units such as supply, amplifiers are located to far away, and then the single
point grounding is impractical. The ground loops can exist due to capacitive coupling in single point
grounding.
18. What is the necessity of grounding and state is advantages.
The connection between electrical appliances and devices with the earth plate or electrode through a thick
wire of low resistance to provide safety is known as Earthing or Grounding, is the reference point in an
electrical circuit from which voltages are measured, a common return path for electric current, or a direct
physical connection to the Earth. Earthing System or Grounding System in Electrical network is for safety
purpose. i) Stabilizes voltage levels ii) Prevents damage and injury iii) Protection against electrical
overload
19. What is meant by ground loop? How it is created?
An unwanted current that flows in a conductor connecting two points that is nominally at the same potential,
i.e., ground, but are actually at different potentials.
The electrical potential at different points on the surface of the Earth can vary by hundreds of
volts, primarily from the influence of the solar wind. Such an occurrence can be hazardous, e.g., to
personnel working on long grounded conductors such as metallic telecommunications cable pairs.

7. A ground loop can also exist in a floating ground system, i.e., one not connected to an Earth
ground, if the conductors that constitute the ground system have a relatively high resistance, or have,
flowing through them, high currents that produce a significant voltage ("I•R") drop. Ground loops can be
detrimental to the operation of the electrical system. Contrast with ground current.
20. What are parasitic voltages and how are they eliminated?
The voltages induced due to dissimilar metal to metal connections affecting the signal are called parasitic
voltage. The parasitic voltages are of very small value and typically observed in case of potentiometer switch or
sliding wire. Using switches or sliding contacts, high resistance is shunted across a reference resistor in circuit.
Due to this parasitic parasitic voltage, contact resistances are in high resistance circuit and thus the error
gets reduced. The parasitic voltages are generally eliminated using differential input amplifiers such as op-amp.
21. Define interference.
The instruments used for electrical measurements are in an environment which contains many sources of
electrical magnetic energy. These sources can produce undesirable signals called interference.
UNIT IV – Storage and Display Devices
1.What is a recorder and what are the types of it?
It is used to record all electrical and nonelectrical quantities as a function of time.
2.What are the different types of magnetic recording?
Direct recording, Frequency modulated (FM) recording & Pulse duration modulation (PDM) recording
3.What is magnetic tape recorder?
Magnetic tape recorder is a recorder which records analog data in such a manner that they can be reproduced in
electrical form again.
4.What are the basic components of a tape recorder?
Recording head, Magnetic tape, Reproducing head, Tape transport mechanism & Conditioning devices.
5.List the advantages and disadvantages of direct recording?
1. It requires simple and cheap electronic circuits only.
2. It can be used to record voice signals.
3. It has a good dynamic ratio without increase in distortion.
4. It has wide frequency response from 50 Hz to 2 MHz for tape speed of 3.05 m/s. It has a very high
bandwidth.
Disadvantages
1. Amplitude instability in recorded signal.
2. Due to poor manufacturing and dirt on the tape, some portion may not be perfectly recorded.
3. It can be used only when maximum band width is needed.
4. It cannot record d.c signals.
6.What are the advantages and disadvantages of digital data recording?
1. Process of recording digitally coded numbers is simple.
2. High accuracy.
3. Insensitive to speed of magnetic tape
4. Information can directly fed to computers for processing.
5. Non linearity and distortion problems do not exist in these recorders.
Disadvantages
1. High quality of magnetic tape is needed for proper recording.
2. Requires ADC.
3. Extra circuitry is needed for parallel recording.
4. Loss of pulses when rate of pulses increases.
7.What is CRO? What are the sections of a CRO?
The device which allows, the amplitude of periodic or non periodic signals, to be displayed primarily as a function of
time, is called cathode ray oscilloscope. It gives visual representation of time varying signals. The main parts are i)
Electron gun assembly ii) Deflection plate assembly iii) Fluorescent screen iv) Glass envelope.

8. 8.What is meant by deflection sensitivity of a CRT?
The deflection sensitivity of a CRT is defined as the deflection of the screen per unit deflection voltage
9.List the advantages of digital storage oscilloscope.
i) Easier to operate. ii) Infinite storage time iii) Flexible display iv) cursor measurement possible v) X-
Y Plots, B-H Curve, iv) P-V diagrams can be displayed.
10.Differentiate between dual trace and dual beam CRO
ii) In a dual beam oscilloscope we are using two separate electron beam for producing different wave
forms. But in a dual trace oscilloscope the same beam is used for producing two different wave forms.
iii) The dual trace oscilloscope cannot capture two fast transient events, as it cannot switch quickly
enough between traces. The dual beam oscilloscope has two separate electron beams, therefore two completely
separate vertical channels.
11.List two requirements of sweep generator.
1. The sweep must be linear in nature, for all screen horizontal deflection.
2. To move spot in one direction only, the sweep voltage must drop to zero suddenly, after reaching the
maximum value.
12.Compare line printer and dot matrix printer.
No Line Printer Dot Matrix Printer
1 Prints only one line at a time Prints a character at a time.
2 Characters are embossed in a drum or chain Formed by combination of dots.
3 No different fonts Various fonts
4 Better printing quality Poor printing quality
5 Better printing speed Poor printing speed
6 Heavy duty printers Light duty printers
13.State the features of ink-jet printers.
o They can print from two or four pages per minute.
o The operating cost is quite low.
o Resolution is about 360 dots per inch; therefore better printing quality is achieved.
14.List the advantages of laser printer.
1. Speed 2.Precision 3. Economy 4. Greater Speed 5. No spillage of excess ink 6. Low Running cost 7. Tonner
is cheap and lasts for longer time.
15.Write two advantages of LED in electronic displays
i) Long life ii) High reliability iii) fast switching characteristics.
Applications: i) construction of alpha numeric displays and seven segment displays. Ii) Indicators iii) Front panel
indicators
16.Differentiate between LED and LCD.
No LED LCD
1. Consumes more power. Consumes less power.
2. High cost. Low cost.
3. More life time. Less life time.
4. Capable of generating its own light. Requires an external or internal light source.
17.What are the different materials used in LED? Also name the colours emitted.
Gallium arsenide phosphate, Gallium arsenide, Gallium Phosphide. Colours emitted: Red, yellow, green, infrared
18.What is CRO? What are the sections of a CRO?
The device which allows the amplitude of periodic and non periodic signal, to be displayed primarily as a function of
time is called cathode ray oscilloscope. It gives visual representation of time varying signals. The main parts are i)
Electron gun ii) Deflection System iii) Fluorescent Screen iv) v) Base

9. 19.List the two advantages of digital X-Y recorder.
1. Simultaneous storage of number of input signals is possible.
2. The data can be plotted using multi – pen plotting system
3. The recorder can record or draw grids, axis.
4. The hardware and software interface provides better capabilities.
20.List out the advantages and disadvantages of LCD.
Advantages: Low cost & Low power consumption
Disadvantages: Life time is very less compared with LED ii) Reliability is low iii) It occupies large area.
21.List the uses of DSO.
i)Testing signal voltage in circuit debugging. ii) Testing in manufacturing. iii) Designing. iv)Testing of signals
voltage in radio broadcasting equipment. V)In the field of research. Vi) Audio and video recording equipment

10. UNIT V- Transducer and Data Acquisition System
1. Mention 2 disadvantages of capacitive transducer? (May-11)
 Output impedance of capacitive transducer is very high. So its measuring circuit becomes
very complicated.
 The capacitance of capacitive transducer change with change in temperature or account
of presence of small external matter. Example: dust particles, moisture.
2. Give the 2 types of principles for the operation of optical transducers (may-11)
Intrinsic Sensor: In this the fiber optic cables itself is the sensor.
Extrinsic Sensor: In this fiber optic cable is only used to guide light to or from a
conventional sensor.
3. Write the function of transducer. (May-11)
It converts one type of energy into another.
4. Give any 2 applications of smart sensors. (May-11)
Self calibration. Computation. Communication. Multi sensing.
5. Define inverse
transducer with example (May-10)
An inverse transducer is defined as device which converts an electrical quantity into a
non electrical quantity. It is a precision actuator which has an electrical input and a low
power non electrical output.
6. Mention any 4 types of analog to digital convertor? (May-10)
Flash type of convertor, Staircase convertor, Tracking convertor, Successive
approximation type
7. What are the classifications of encoder? (Dec-10)
Tachometer transducers, Incremented transducers, Absolute transducers.
8. What is the need of sample and hold circuit in A/D convertor? (Dec-10)
Sample and hold circuits are the devices that store analog information and reduce the
aperture time of an A/D convertor. A sample hold is a simply a voltage memory device
in which an input voltage is acquired and then stored on a high quality capacitor.
9. Define the primary and secondary transducers? (May 2010)
Primary Transducer: When the input signal is directly sensed by the transducer and
physical phenomenon is converted into electrical form directly then such a transducer is
called the primary transducer.
Secondary Transducer: When the input signal is sensed first by some detector or sensor
and then its output being of some from other than input signals is given as input to a
transducer for conversion into electrical form, then such a transducer falls in the category
of secondary transducers.
10. State the performance parameters of ADC (May 2010)
Resolution. Quantization error, Conversion time.
11. How do you classify transducers? (Dec 2010)
On the basis of transduction form used ii) as primary and secondary transducers. iii) As
active and passive transducers. iv) As analog and digital transducers. v) As transducers
and inverse transducers.
12. What is telemetry? (Dec 2010)
Telemetry is a highly automated communications technique with the help of which
measurements and data collection are done at remote.
13. What is piezo-electric effect? (Dec 2010)
A piezoelectric material is one in which an electric potential appears across certain
surfaces of the crystal if the dimensions of the crystals are changed by the application of a
mechanical force this potential is produced by the displacement of charges. This effect is
reversible. This phenomenon is known as piezoelectric effect.
14. Explain the working principle of capacitive transducers? (Dec 2010)
The principle of capacitive transducer is based on the familiar equation of capacitance of
parallel plate capacitor.

11. C= ε A /d
15. What are the selection criteria for the transducer? (Jun 2009)
Operating range. Sensitivity. Environmental conditions, Errors and Accuracy.
16. What is meant by strain gauge? What for it is used? (Jun 2009)
It is an example of a passive transducer that uses the variation in electrical resistance in wires
to sense the strain produced by a force on the wires.
17. What is POT? It is active or passive transducer? (Dec 2006)
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.
The POT is a passive transducer since it requires an external power source for its operation.
18. Which are the materials used in piezo-electric transducer? Jun 2006)
Rochelle salt, Ammonium dihydrogen phosphate (ADP), Quartz, Ceramic made with barium
titanate, dipottasium tartrate, potassium dihydrogen phosphate and lithium sulphate.
19. Name the transducer that uses sensing acceleration? (Jun 2006,
May 2005) Piezo-electric transducer.
20. Mention the use of capacitive transducer? (May 2005)
Capacitive transducers can be used for measurement of both linear and angular
displacements. It can be used for measurement of force and pressure. Can be used for
measuring humidity. It is used in conjunction with mechanical modifiers for measurement of
volume, density etc.
20. Write any four basic requirements of transducer? (Dec 2004)
Ruggedness: It should be capable for withstanding overload. Linearity: The input-output
characteristics should be linear.
No Hysteresis: It should not give any hysteresis during measurement while input signal is
varied from low to high value and vice versa.
Residual Deformation: There should be no deformations on removal of load after long
period of time