16. Which type of thermistor is chosen for temperature measurement and control?
A. High-temperature coefficient of resistance
B. Low-temperature coefficient of resistance
C. Positive temperature coefficient of resistance
D. None of the mentioned
Answer: A
Thermistors with a high-temperature coefficient resistance are more sensitive to temperature change and are therefore well suited to temperature measurement and control.
17. Photoconductive cell changes its resistance with
A. Change in temperature
B. Material composition
C. Incident radiant energy
D. Change in elasticity
Answer: C
The photoconductive cell is a type of transducer that changes its resistance or varies its resistance with an incident radiant energy with light.
18. What will be the resistance of a photoconductive cell in darkness?
A. 1000-3000Ω
B. 100MΩ
C. 250-500Ω
D. None of the mentioned
Answer: D
The resistance of the photoconductive cell in darkness is typically in the order of 100kΩ.
19. Which material is used for photoconductive cells?
A. Germanium
B. Cadmium sulfide
C. Lithium
D. Phosphorous
Answer: B
The conductivity in cadmium sulfide is a function of incident radiant energy. So, it is used for the photoconductive cell.
20. Name the resistive transducer that varies its resistance on the application of external stress?
A. Photocells
B. Light-dependent
C. Stain gage
D. None of the mentioned
Answer: C
The strain gage is a type of resistive transducer whose resistance changes due to elongation or compression when the external stress is applied.
21. Strain gage are used to monitor changes in
A. Pressure
B. Torque
C. Displacement
D. All of the mentioned
Answer: D
A strain gage may be used to monitor changes in applied pressure, torque, and displacement by measuring the corresponding change in the gage resistance.
22. Which type of resistive transducer is most commonly used?
A. Thermistor
B. Photoconductive cell
C. Strain gage
D. All of the mentioned
Answer: A
Thermistors are most commonly used because they are relatively easy to mount.
23. What is the unit of strain gauge?
A. Ω/oC
B. Lux
C. Newton / meter2
D. Volts
Answer: C
The strain gauge changes resistance when the external stress is applied. Therefore, the stress is defined as force/unit area i.e. Newton/meter2.
24. Which type of strain gauge has a better resolution?
A. Semiconductor strain gage
B. Wire strain gage
C. Wire and Semiconductor strain gage
D. None of the mentioned
Answer: A
A semiconductor strain gauge is much more sensitive than a wire type and so, it provides better accuracy and resolution.
25. How a differential instrumentation amplifier using a transducer bridge can be used as a temperature controller?
A. Increase room temperature
B. Replaces calibrated meter with relay
C. Change the bridge resistance
D. Replace the thermistor with a light intensity meter
Answer: B
A simple and inexpensive temperature controller can be constructed by replacing a meter with a relay in the circuit. So, the output of the differential instrumentation amplifier drives a relay that controls the current on the heat-generating circuit.
26. The strain gage elements in the analog weight scale are mounted on a
A. Base of weight platform
B. Hanging weight platform
C. Loading weight platform
D. Varying weight platform
Answer: A
The strain gauge elements are mounted on the base of the weight platform. So, whenever the external force or weight is applied to the platform, one pair of elements in the opposite arm of the bridge elongates, whereas the other pair in the opposite arm compresses.
27. What will be the resultant circuit, when the thermistor in the bridge transducer is replaced by a strain gage?
A. Differential input and differential output amplifier
B. Light intensity
C. Analog weight scale
D. None of the mentioned
Answer: C
By connecting a strain gauge in the transducer bridge, the differential instrumentation amplifier circuit can be converted into a simple and inexpensive analog weight scale.
28. RT1, RT2, RT3, and RT4 are unstrained gage resistance. If the resistance change in each gage is 0.3Ω. Choose the correct option?
1. RT1 and RT3 increase by 0.3Ω
2. RT1 and RT3 increase by 0.3Ω
3. RT2 and RT4 decrease by 0.3Ω
4. All of the above
Answer: A
When external weight is applied to the platform. One pair of elements elongates and the other pair compresses. Therefore, RT1 and RT3 are △R and the increase in RT2 and RT4 is also by △R.
