Instrumentation Multiple Choice Questions Answers

21. Hall effect transducers are used for measuring

(a) magnetic field.
(b) current.
(c) electric field.
(d) pressure.

22. Hall effect device can be used to

(a) multiply two signals.
(b) divide one signal by another on an instantaneous basis.
(c) add two signals.
(d) subtract one signal from another.

23. The measurement of Hall coefficient of a semiconductor with one type of charge carrier gives the information about

(a) sign of charge carrier.
(b) density of charge carrier.
(c) both sign and density of charge carrier.
(d) mass of the charge carrier.

24. Which one of the following transducers can be used for magnetic flux density measurement ?

(a) LVDT.
(b) Synchro.
(c) Hall effect transducer.
(d) Thermocouple.

25. Magnetoelastic transducers operate on the principle of

(a) change in permeability with change in stress.
(b) change in dimensions with change in applied stress.
(c) change in coercive force with change in stress.
(d) none of the above.

26. Photoelectric transducers are used for the measurement of any phenomenon associated with variation in

(a) light intensity.
(b) magnetic flux.
(c) current.
(d) voltage.

27. Which of the following does not require auxiliary circuitry if used as transducer ?

(a) Capacitance.
(b) Photocell.
(c) Resistance.
(d) Inductance.

28. A tachometer encoder has

(a) single output.
(b) two outputs.
(c) three outputs.
(d) four outputs.

29. A tachometer encoder can be used for measurement of

(a) displacement in one direction only.
(b) displacement in both directions.
(c) speed in situations where the rotation never reverse.
(d) both (a) and (c).

30. Incremental encoders use

(a) one channel only.
(b) two channels.
(c) two channels and sometimes three.
(d) four channels.

31. The drawbacks of incremental encoders are that

(a) any false pulse resulting from electric noise will cause error, which will persist even on disappearance of noise.
(b) the failure of power supply causes total loss of position data which cannot be retrieved even after restoration of power supply.
(c) these encoders are usually limited to a measurement of single revolution.
(d) both (a) and (b).

32. Absolute encoders are employed for

(a) normally one revolution.
(b) continuous speed.
(c) continuous speed in both directions.
(d) none of the above.

33. A bolometer is an element that

(a) senses thermal output.
(b) senses optical input and gives thermal output.
(c) senses optical input and gives electrical output.
(d) senses electrical input and gives optical output.

34. Bolometers are used for measuring

(a) electrical signals.
(b) optical inputs.
(c) thermal radiations.
(d) none of these.

35. Ring-balance meter cannot be used for measuring

(a) pressure.
(b) differential pressure.
(c) mass flow rate.
(d) total flow.

36. A force balance transducer

(a) amplifies the output from the sensing element.
(b) feeds back the output to an element which makes a force-summing member to return to its zero position.
(c) both (a) and (b).
(d) neither (a) nor (b).

37. Which displacement transducer is used for accurate and linear measurement ?

(a) LVDT.
(b) Strain gauge.
(c) Potentiometer.
(d) Capacitive displacement transducer.

38. Which of the following primary detector type transducers are employed for displacement measurement?

1. Thermistor. 2. Diaphragm. 3. Thermocouple. 4. Pivot Torque.

Select the correct answer using the code given below :
(a) 1 and 2
(b) 2 and 4
(c) 3 and 4
(d) 1 and 4

39. The ballast circuit employs a capacitor to act as high pass filter for measurement of

(a) static strains.
(b) dynamic strains.
(c) both static and dynamic strains.
(d) none of the above.

40. Why are dummy strain gauges employed ?

(a) For calibration of strain gauges.
(b) For increasing the sensitivity of the bridge.
(c) For compensation of temperature variations.
(d) For neutralizing the influence of bridge voltage supply variations.

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