MEASUREMENTS and INSTRUMENTATION Questions and Answers :-
1. A 10MHz CRO has
A. 5MHz sweep
B. 10MHz vertical oscillator
C. 10MHz horizontal oscillator
D. 10MHz supply frequency
ANSWER: C
2. Which of the following instruments can be used to measure AC current only?
A. Permanent Magnet Type ammeter
B. Induction type ammeter
C. Moving iron voltmeter
D. Moving iron ammeter
1. D only
2. B only
3. A, B, D
4. B and D only
ANSWER: 2
3. An oscilloscope indicates
A. Peak to peak value of voltage
B. DC value of voltage
C. RMS value
D. Average value
ANSWER: A
4. In a ballistic galvanometer, the deflecting torque is proportional to
A. the current through coil
B. square of current through coil
C. square-root of current through coil
D. sine of measured
ANSWER: A
5. The error of an instrument is normally given as a percentage of
A. measured value
B. full-scale value
C. mean value
D. rms value
ANSWER: B
6. If the instrument is to have a wide range, the instrument should have
A. Linear scale
B. Square-law scale
C. Exponential scale
D. Logarithmic scale
ANSWER: D
7. The resistance can be measured most accurately by
A. Voltmeter-ammeter method
B. bridge method
C. multimeter
D. Megger
ANSWER: B
8. The repeat accuracy of an instrument can be judged from its
A. static error
B. linearity error
C. dynamic error
D. standard deviation of error
ANSWER: D
9. Which of the following meters has a linear scale?
A. Thermocouple meter
B. Moving iron meter
C. Hot wore meter
D. Moving coil meter
ANSWER: D
10. No eddy current and hysteresis losses occur in
A. Electrostatic instruments
B. PMMC instruments
C. Moving iron instruments
D. Electrodynamo meter instruments
ANSWER: A
11. Two voltmeters have the same range 0-400V. The internal impedance are 30,000 Ohms and 20,000 Ohms. If they are connected in series and 600V be applied across them, the readings are
A. 360V and 240V
B. 300V each
C. 400V and 200V
D. one of the meters out of the range and other 100V
ANSWER: A
12. The full-scale deflection current of an ammeter is 1 mA and its internal resistance is 100Ohm. If this meter is to have full deflection at 5A, what is the value of the shunt resistance to be used?
A. 49.99 Ohms
B. 1/49.99 ohms
C. 1 Ohm
D. 2 Ohms
ANSWER: B
13. The full-scale deflection current of an ammeter is 1 mA and its internal resistance is 100Ohm. This is to have full deflection when 100V is measureD. What is the value of series resistor to be used?
A. 99.99 K ohms
B. 100 K ohms
C. 99.99 ohms
D. 100 ohms
ANSWER: A
14. Why is a MISC meter not recommended for DC measurement?
A. The meter is calibrated for AC and it’s error for DC would be high
B. The meter does not respond to DC signals
C. The error is high due to hysteresis effect
D. The error is high due to eddy current effect
ANSWER: C
15. The EMF of Weston standard cell is measured using
A. Moving- iron meter
B. Moving-coil meter
C. Digital Volt meter
D. Potentiometer
ANSWER: D
16. A mulliammeter can be used as
A. Voltmeter and ammeter
B. Wattmeter
C. Ohmmeter
D. Frequency meter
ANSWER: A
17. Which instrument has identical calibration for ac as well as dc values?
A. Hot wire type
B. Moving coil type
C. Induction type
D. Moving iron type
ANSWER: A
18. An instrument to be used for measurement and control should preferably have
A. Dead zone and dead time
B. Linear output and fast response
C. Non-linear output
D. A highly damped response
ANSWER: B
19. The current coil of a wattmeter is connected to the CT of R-phase. The potential coil is connected across Y and B phases. The wattmeter measures
A. Active power in R phase
B. Active power of Y phase
C. Reactive power of R phase
D. Power proportional to 3 phase power if the load is balanced
ANSWER: C
20. The problem of Electro-static coupling in a transformer is acute at
A. Low frequencies
B. Power frequencies
C. High frequencies
D. High load on the transformer
ANSWER: C
21. Which meter is suitable for the measurement of 10mV at 50MHz?
A. Moving iron voltmeter
B. VTVM
C. Moving coil voltmeter
D. CRO
ANSWER: D
22. It can be stated that
A. CT operates at almost the same flux density as a PT
B. CT operates with a higher flux density than PT
C. CT operates with considerably lower flux density than a PT
D. no generalisation can be made with regard to the flux densities in CT and PT
ANSWER: C
23. The thermocouple instruments do not have
A. High sensitivity
B. Absence of frequency error
C. Independence of ambient temperature
D. High degree of measuring accuracy
ANSWER: D
24. Some wire- wound resistors have bifilar winding. This type of winding is used to
A. Increase the thermal stability
B. Reduce the tolerance
C. Reduce the inductance of winding
D. Double the power rating of the resistor
ANSWER: C
25. Wien bridge is useful for measuring
A. Very high frequency
B. Low frequency
C. Medium frequency
D. High frequency
ANSWER: D
MEASUREMENTS and INSTRUMENTATION Questions and Answers ::
26. A megger is usually
A. Moving iron type instrument
B. Electro-static type instrument
C. Hot-wire type instrument
D. Moving coil type instrument
ANSWER: D
27. A moving iron ammeter may be compensated for frequency errors by
A. a shunt resistance
B. a series inductance
C. shunt capacitance
D. series resistance
ANSWER: C
28. Ryall crest voltmeter is used for measurement of
A. AC voltage of any form
B. Low frequency voltage
C. High DC voltage
D. High AC voltage
ANSWER: D
29. Jewels are used in instruments for the purpose of
A. Damping
B. Torque control
C. Suppressing noise
D. Bearing
ANSWER: D
30. The thermocouple instrument will measure
A. Current
B. Voltage
C. Flux
D. None of the above
ANSWER: D
31. A CRO can display
A. AC signals
B. DC signals
C. Both AC and DC signals
D. Time invariant signals
ANSWER: C
32. The internal resistance of an ammeter should be
A. Very small
B. medium
C. High
D. Infinity
ANSWER: A
33. A galvanometer has
A. air friction damping
B. fluid friction damping
C. Spring coil damping
D. Eddy current damping
ANSWER: D
34. Electrostatic instruments are normally used for
A. Low current measurements
B. High current measurements
C. Low voltage measurements
D. High voltage measurements
ANSWER: D
35. In a moving coil instrument, the deflecting torque is proportional to
A. Current
B. Square of the current
C. Squareroot of the current
D. sine of the measurand
ANSWER: A
36. The absolute measurement of resistance is done by
A. Ohm’s law method
B. Bridge Method
C. Rayleigh method
D. Lorenz method
ANSWER: D
37. To measure the flux, devices used are based on
A. Voltaic effect
B. Piezo-electric effect
C. Hall effect
D. Photo-voltaic effect
ANSWER: C
38. The form factor in AC is the ratio of
A. peak value to average value
B. peak value to rms value
C. rms value to average value
D. rms value to peak value
ANSWER: C
39. PMMC type instruments normally use
A. Air friction damping
B. Fluid friction damping
C. Eddy current damping
D. None of the above
ANSWER: C
40. In a moving iron meter, the deflecting torque is proportional to
A. Current through the coil
B. Square of the current through the coil
C. Sine of the measurand
D. Squareroot of the measurand
ANSWER: B
41. In a gravity controlled instrument, the deflection angle is proportional
A. Measurand
B. Square of the measurand
C. sine inverse of measurand
D. sine of the measurand
ANSWER: C
42. Ampere is one of the
A. Supplementary units
B. Derived units
C. Base units
D. Units used to measure charge
ANSWER: C
43. Direct method is used to measure
A. Length
B. Temperature
C. Pressure
D. Voltage
ANSWER: A
44. A rectifier type instrument is connected to 100VDC and is operated in the DC measuring module reads
A. 111V
B. 90V
C. 50V
D. 100V
ANSWER: A
45. A permanent magnet moving coil ammeter has a coil resistance of 99ohm and Full Scale DeflectionFSD. current of 0.1mA. Shunt resistance is 1 ohm. Current through the meter at 0.5 F.S.D is
A. 0.007mA
B. 0.05mA
C. 0.023mA
D. 0.1mA
ANSWER: B
46. One single phase wattmeter operating on 230V and 5A for 5 hours makes 1940 revolutions. Meter constant in revolutions is 400. What is the power factor of the land?
A. 1
B. 0.84
C. 0.73
D. 0.65
ANSWER: B
47. For power measurement of three phase circuit by two wattmeter method, when the value of power factor is less than 0.5 lagging
A. one of the wattmeters will read zero
B. both give the same readings
C. one of the wattmeter connections will have to be reversed
D. pressure coil of the wattmeter will become ineffective.
ANSWER: C
48. When using ohmmeter, applied voltage is to be disconnected from the circuit because
A. Voltage source will increase resistance
B. Current will decrease resistance
C. the ohmmeter has its own internal battery
D. non of the above
ANSWER: C
49. Which wave has the least form factor?
A. Square wave
B. Rectangular wave
C. Sine wave
D. Triangular wave
ANSWER: A
50. With a sweep time 10ms across the screen the approx. horizontal sawtooth frequency will be
A. 50Hz
B. 100Hz
C. 1kHz
D. 500Hz
ANSWER: B
51. A spring controlled indicating instrument has a deflection of 90deg for maximum current I. The corresponding deflection for a gravity controlled instrument is
A. 90°
B. 120°
C. 30°
D. 0°
ANSWER: C
52. It is found that 10A current passes through a resistor of 10ohms. The resistor has 5% tolerance . The error in measurement of current can be as high as 5%. What is max error in measurement of power, calculated from measured value of I and the nominal value of resistor?
A. 100 W
B. 150W
C.50W
D. 200W
ANSWER: B
53. A resistor of 10Kohms with 5% tolerance is connected in parallel with a 5Kohms resistor of 10% tolerance. What is the tolerance limit for the parallel network?
A. 5%
B. 6.67%
C. 10%
D. 8.33%
ANSWER: D
54. The resistance offered to the passage of an in-varying current by a column of mercury at the temperature of melting ice of mass 14.4521 gms of uniform cross-sectional area and length 106.3cm is
A. Standard ohm
B. One international ohm
C. One ohm according to SI units
D. One ohm according to working standards
ANSWER: B