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DEPT: II EEE
SUB/ CODE : MEASUREMENTS AND INSTRUMENTATION/EE33
2MARKS:
UNIT-I
INTRODUCTION
1. Define instrument.
An instrument is a device for determining the value or magnitude of a quantity.
2. What are the types of instruments?
a. Mechanical instrument
b. Electrical instrument
c. Electronic instrument
3. Write the dynamic characteristics of any measurement system.
a. Step change
b. Linear change
c. Sinusoidal change
d. Lag
e. Fidelity
f. Dynamic error
4. What is standard? What are the different types of standards?
A standard is a physical representation of a unit of measurement. A known accurate
measure of physical quantity is termed as standard.
Types:
a. Primary standard
b. Secondary standard
c. International standard
d. Working standard.
5. What is calibration?
Calibration is the process of checking the accuracy of instrument by comparing the
instrument reading with a standard meter of known accuracy.
6. Define arithmetic mean.
Arithmetic mean is calculated by taking the sum of all readings divided by the
number of readings.
7. Define the terms precision and sensitivity.
Precision:
It is a measure of the repeatability of a series of measurements.
Sensitivity:
It is the measure of change in reading of an instrument for a given change in
the measured quantity.
8. Define static error.
The static error of a measuring instrument is the numerical difference between the
true value of a quantity and its value as obtained by measurement.
9. Define accuracy.
The degree of closeness of a measurement compared to the true value.
10. Write the static characteristics of measuring instruments.
a. Accuracy
b. Precision
c. Sensitivity
d. Resolution
e. Error
11. What are the different calibration methodologies?
(i) Direct calibration
a. Meter calibration
b. Generator calibration
c. Transducer calibration
(ii) Indirect calibration
d. Meter calibration
e. Generator calibration
a. Transducer calibration
12. Define instrumental errors.
These errors arise due to inherent short coming in the instrument, misuse of the
instruments and loading effects.
13. List the different types of possible errors in measurements.
a. Gross error
b. Systematic error
c. Environmental error
d. Observational error
e. Random error
14. What is the need for measurement?
The need for the measurement is to know about the unknown magnitude.
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15. Write the need for calibration.
The need for calibration means is to check the accuracy and reliability.
16. What are the basic elements of a measurement system?
a. Primary sensing element.
b. Variable conversion element.
c. Variable manipulation element.
d. Data transmission element.
e. Data presentation element.
17. What is meant by measurement?
The process of determining the present value is called as measurement.
18. What are the methods of measurements?
a. Direct method.
b. Indirect method.
19. Define environmental error.
This error occurs due to external conditions to the measuring device, including
conditions in the area surrounding the instrument, such as the effects of change in
temperature, humidity, magnetic or electrostatic fields.
20. Define sensitivity
The ratio of the change in output of the instrument to a change of input or measured
value is called sensitivity.
UNIT-II
ELECTRICAL AND ELECTRONIC INSTRUMENTS
1. Write the classification of measuring instruments.
Electrical instruments are mainly classified as
a. Indicating instruments
b. Recording instruments
c. Integrating instruments
2. Define indicating instruments.
Indicating instruments are used to indicating the magnitude of unknown quantity.
The examples are ammeters, voltmeters etc.
3. Define recording instruments.
These instruments give a continuous record of the given input quantity. The
examples are various types of recorders.
4. Define integrating instruments.
These instruments measure the total quantity of electricity delivered over period
of time. Example: energy meter.
5. What are the requirements of an instrument?
The following systems must be present in an instrument
a. Deflecting system producing deflecting torque.
b. Controlling system producing controlling torque.
c. Damping system producing damping torque.
6. What are the types of instruments?
It consist of two types
(i) Permanent magnet moving coil instrument.
(ii) Moving iron instruments
a. Moving iron attraction type.
b. Moving iron repulsion type.
7. What are the advantages of digital instruments over analog instruments?
a. High accuracy.
b. High input impedance.
c. Reading speed is very high.
d. Digital output can be directly recorded.
8. Define gravity control.
It consists of a small weight attached to the moving system. Whose position is
adjustable. This weight produces a controlling torque due to gravity.
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9. Define spring control.
In this system two hair springs are attached to the moving system which produce
the controlling torque.
10. Explain the purpose of Schmitt trigger in digital frequency meter.
In a digital frequency meter, Schmitt trigger is connected between amplifier and
a gate, it is used to convert the analog voltage from the amplifier to train of pulses
which is fed to the gate.
11. Which torque is absent in energy meter? Why?
In energy meter, there is no controlling torque, as the driving torque alone is
enough to cause continuous revolution of the disc.
12. What are the various principles of analog type electrical instruments?
a. Magnetic effect
b. Heating effect
c. Electrostatic effect
d. Electromagnetic effect
e. Hall effect
13. What is the principle of ramp type digital voltmeter?
Ramp type digital volt meter works on the principle of comparison of unknown
voltage with the ramp signal and by counting the number of pulses passing
through till both the voltages become equal. This number of pulse will give the
direct indication of the voltage.
14. What is the purpose of instrument transformers?
The transformers used for measuring very large values of current or voltage
which can not be directly measured are called instrument transformer. Two types
of instrument transformers are
a. Current transformer
b. Voltage transformer.
15. How a PMMC meter can be used as voltmeter and ammeter?
When a resistance is connected across the basic PMMC meter then it will act as a
D.C ammeter and when a resistance is connected in series with the basic PMMC
meter then the meter will act as a D.C voltmeter.
16. What is volt ampere hour and watt hour?
Volt ampere hour is the reactive power consumed by the load where as watt
hour is the real power consumed by the load.
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17. What are the different methods of measurement of frequency in the power
frequency range?
a. Mechanical resonance type or vibrating reed type frequency meter.
b. Electrical resonance type frequency meter.
c. Weston frequency meter.
18. How are the analog instruments classified on the basis of method used for
comparing the unknown quantity?
a. Electrostatic type instruments.
b. Electromagnetic type instruments.
c. Instruments using magnetic effect.
d. Instruments using heating effect.
e. Instruments using hall effect.
19. Give the advantage of moving iron meters?
a. The same instrument can be used for both A.C and D.C measurement.
b. Torque /weight ratio is very high hence errors due to friction is very high.
c. These instruments are highly accurate.
d. These instruments are simple in construction.
20. What is creeping in energy meters?
A slow but continuous rotation of energy meter disc even when there is no
current flowing through the current coil but only the pressure coil is energised, is
called creeping. Some other factors that cause creeping are excessive voltage
across the pressure coil, vibrations and external magnetic fields.
UNIT-III
COMPARISION 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.
a. Measurement of small emfs (up to 2V).
b. Comparison of emf of two cells.
c. Measurement of high emfs (up to 250V).
d. Measurement of resistance.
e. Measurement of current.
3. What are the types of potentiometer?
a. D.C potentiometer
b. A.C potentiometer.
4. What are the types of DC potentiometer?
a. Simple potentiometer.
b. Direct reading potentiometer.
c. Crompton potentiometer.
d. 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?
a. Polar potentiometer.
b. Co ordinate potentiometer
7. Mention some applications of AC potentiometers.
a. Measurement of self inductance
b. Calibration of ammeter
c. Calibration of voltmeter
d. Calibration of wattmeter
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8. What are the uses of bridge circuits?
The bridge circuits are mainly used for measuring unknown quantities such as
resistance, inductance and capacitance.
9. What are the two main types of bridges?
a. DC bridges
b. AC bridges
10. What are the types of DC bridges?
a. Wheatstone bridge
b. Kelvin’s bridge
c. Kelvin’s double bridge.
11. What is a Wheatstone bridge?
Wheatstone bridge is used for measurement of medium resistances in the range
of 1Ω to 100 k Ω.
12. What is Kelvin’s bridge?
Wheatstone bridge is not suitable for measurement of very low resistance.
Kelvin’s bridge is a modification of Wheatstone bridge and is used to measure
values of resistance below 1 Ω.
13. What is Kelvin’s double bridge?
This circuit consists of double bridge. This circuit is mainly used for measuring
very low resistances from 0.00001 Ω to 1 Ω.
14. What is Schering bridge?
The Schering bridge, one of the most important AC bridges, is used for
measurement of capacitors, it is also measures the insulating properties of the
electrical cables and equipments.
15. What is Maxwell’s bridge?
The Maxwell bridge is used to measure both a given inductance and its series
resistance by comparison to a standard capacitance.
16. What is Anderson bridge?
It is a modified version of the Maxwell’s inductance capacitance bridge. In this
method the self inductance is measured in terms of a standard capacitor.
17. What is earth loop?
Earth loops form a distinct part of the guarding system of electrical equipments.
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18. 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.
19. Write the classification of interference signal.
a. Capacitive interference
b. Inductive interference
c. Electromagnetic interference
d. Electrostatic interference
e. Ground loop interference
20. What are the sources of electromagnetic interference?
a. Welding equipment.
b. Inductive or capacitive coupling
c. AC power circuits, radio frequency transmitters.
UNIT-IV
STORAGE AND DISPLAY DEVICES
1. Define recorder.
It is used to record all electrical and nonelectrical quantities as a function of time.
2. Define X-Y recorder.
It is used to study the behaviour of one variable with respect to another variable
instead of recording recording them separately as function of time. There are two
types of X-Y recorders namely.
a. Analog X-Y recorders.
b. Digital X-Y recorders.
3. List out the controllers normally found in XY recorder.
a. Servo controller.
b. Chopper controller.
4. 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.
5. What is the basic operating principle of digital tape recording?
Digital data can be recorded and stored in magnetic tapes using a variety of
techniques. The basic principle used to modulate the digital data in some form and
then record this modulated data in the tape.
6. What are the various methods of recording data?
a. Direct recording.
b. Frequency modulated (FM) recording.
c. Pulse duration modulation (PDM) recording.
7. Write the basic components of magnetic tape recorder.
Following are the basic components of magnetic tape recorder:
a. Recording head
b. Magnetic tape
c. Reproducing head
d. Tape transport mechanism
e. Conditioning devices.
8. List the main parts of cathode ray tube.
a. Electron gun assembly
b. Deflection plate assembly
c. Fluorescent screen
d. Glass envelope.
9. List out the advantages and disadvantages of LCD.
Advantages:
a. Low cost
b. Low power consumption
Disadvantages:
a. Life time is very less compared with LED.
b. Reliability is low
c. It occupies large area.
10. What are the types of printers according to printing methodology?
(i) Impact printer
a. Line printer
b. Dot matrix printer
(ii) Non impact printer
a. Ink jet printer
b. Laser printer
11. In what ways line printers are advantage over dot matrix printer?
a. Prints one line at a time.
b. Printing speed is better
c. Printing quality is better
12. What are the different materials used in LED? Also name the colours emitted.
Materials:
a. Gallium arsenide phosphate
b. Gallium arsenide
c. Gallium Phosphide
Colours emitted:
Red, yellow, green, infrared
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13. Differentiate between LED and LCD.
No LED LCD
1.
2.
3.
4.
Consumes more power.
High cost.
More life time.
Capable of generating its own
light.
Consumes less power.
Low cost.
Less life time.
Requires an external or internal light
source.
14. State the features of ink jet printers.
a. They can print from two or four pages per minute.
b. The operating cost is quite low.
c. Resolution is about 360 dots per inch, therefore better printing quality is
achieved.
15. Define the deflection sensitivity of CRT.
The deflection sensitivity of a CRT is defined as the deflection of the screen per
unit deflection voltage.
16. What are the different types of amplifiers used for CRO?
a. Vertical amplifier
b. Horizontal amplifier
17. What are the advantages and disadvantages of FM method of magnetic tape
recording?
Advantages:
a. Accurately reproduces the wave form of the input signal.
b. Wide frequency range.
Disadvantages:
a. Requires a high tape speed
b. Limited frequency response
c. Requires a high quality of tape transport and speed control.
18. Write the advantages of LED on electronic display.
a. Low power consumption
b. Small size and weight.
c. Long life
d. Very fast action
19. Define data logger?
It is used to automatically record of the readings of instruments located at different
parts of the plant.
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20. What are the functions of a data logger?
The main function of the data logger is to measure electrical output from any type
of transducer.
The data logger is used to automatically record of the readings of instruments
located at different parts of the plant.
21. What are the functions of aluminium layer?
a. The aluminium layer acts as a heat sink for the phosphor and thus reduces
the chances of the phosphor burning.
b. It serves as a light scatter. When the beam strikes the phosphor with
aluminized layer, the light emitted back in to the tube is reflected back
towards the viewer which increases the brightness.
UNIT-V
TRANSDUCER AND DATA ACQUISITION SYSTEM
1. Define transducer.
It is a device which converts one form of energy into another form.
2. What are the classification of transducer?
The transducers are classified as
a. According to the transduction principle
b. Primary and secondary transducer
c. Active and passive transducer
d. Analog and digital transducer
e. Transducer and inverse transducer
3. Define active transducer.
Active transducers are self generating type of transducers. These transducers
develop an electrical parameter which is proportional to the input quantity.
4. Define passive transducer.
Passive transducer do not generate any electrical signal themselves. To obtain an
electrical signal from such transducers, an external source of power is essential.
5. What is analog transducer?
Analog transducer converts input signal in to output signal, which is a continuous
function of time such as strain gauge, LVDT, thermocouple.
6. What is digital transducer?
Digital transducer converts input signal in to the output signal, which is in the form
of pulses.
7. What is an inverse transducer?
An inverse transducer is defined as a device which converts an electrical quantity in
to a non electrical quantity.
8. Write the transducer selection factor.
a. Nature of measurement
b. Loading effect
c. Environmental conditions
d. Measuring system compatibility
e. Cost and availability.
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9. Define strain gauges.
The strain gauge 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 wire.
10. Define gauge factor.
The gauge factor is defined as the ratio of per unit change in resistance to per unit
change in length.
Gauge factor : ΔR/R
ΔL/L
11. What are the main types of potentiometers?
a. Wire wound potentiometer
b. Non wire potentiometers
12. Mention the types of strain gauges
The strain gauges are mainly of four types namely
a. Wire strain gauges
b. Foil strain gauges
c. Thin film strain gauge
d. Semiconductor strain gauge.
13. What is an inductive transducer?
An inductive transducer is a device that converts physical motion in to a change in
inductance. Transducers on the variable inductance type work upon one of the
following principles.
a. Number of turns
b. Geometric configuration
c. Permeability of the magnetic material
14. Mention the advantages of LVDT
a. LVDT has high sensitivity.
b. The LVDT gives a high output.
15. Mention the applications of LVDT.
LVDT are used to measure
a. Displacement
b. Force
c. Weight
d. Pressure
e. Position
16. What are the types of DAS?
The DAS is mainly classified as
a. Analog data acquisition system (DAS).
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b. Digital data acquisition system (DAS).
17. What is piezoelectric effect?
A piezoelectric material is one in which an electric potential appears across certain
surfaces of a crystal if the dimensions of the crystal are changed by the application of
a mechanical force. This potential is produced by the displacement of charges. The
effect is reversible also if varying potential is applied to the proper axis of the crystal,
it will change the dimensions of the crystal there by deforming it. This phenomenon is
known as piezoelectric effect.
18. What are the materials used for piezoelectric transducers?
Common piezoelectric materials include ammonium dihydrogen phosphate , quartz
and ceramics made with barium titanate, potassium dihydrogen phosphate and lithium
sulphate are used in real applications.
19. Define smart sensor?
Smart sensors are sensors with integrated electronics that can perform one or more
of the following functions.
a. Logic functions
b. Two way communication
c. Make decision
20. Mention some applications of smart sensor.
Smart sensor enhances the following applications:
a. Self calibration
b. Computation
c. Communication
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