Instrumentation Amplifier MCQ [Free PDF] - Objective Question Answer for Instrumentation Amplifier Quiz

1. Strain gauge is an example of which device?

A. Transducer
B. Voltage follower
C. Integrator
D. Differentiator

Answer: A

A strain gauge is a device when subjected to pressure or force undergoes a change in its resistance.

2. An instrumentation system does not include

A. Transducer
B. Instrumentation amplifier
C. Automatic process controller
D. Tester

Answer: D

Except for the tester, the remaining blocks form the input, intermediate, and output stages of the instrumentation system.

3. Transmission lines are used for

A. Output signal
B. Input signal
C. Signal transfer
D. All of the mentioned

Answer: C

Transmission lines are the connecting line between the blocks and permit signal transfer from unit to unit.

4. The length of the transmission lines are

A. Longer than 10 meters
B. Shorter than 10 meters
C. Equals to 10 meters
D. None of the mentioned

Answer: D

The length of the transmission lines depends primarily on the physical quantities being monitored and on system requirements.

5. Why output of the transducer is not directly connected to the indicator or display?

A. Low-level output is produced
B. High-level output is produced
C. No output is produced
D. Input is fed directly

Answer: A

Many transducers do not produce output with sufficient strength to permit their users directly. Therefore, the low-level output signal of the transducer needs to be amplified.

6. What are the features of an instrumentation amplifier?

A. Low noise
B. High gain accuracy
C. Low thermal and time drift
D. All of the mentioned

Answer: D

Instrumentation amplifiers are intended for precise low-level signal amplification because of the features mentioned.

7. What is the disadvantage of using LH0036 instrumentation op-amp?

A. Extremely stable
B. Relatively expensive
C. Accurate
D. All of the mentioned

Answer:b

LH0036 is a very precise special-purpose circuit in which most electrical parameters are minimized and performance is optimized. So, it is relatively expensive.

8. What instrument is used to amplify the output signal of the transducer

A. Peaking amplifier
B. Instrumentation amplifier
C. Differential amplifier
D. Bridge amplifier

Answer: B

The major function of the instrumentation amplifier is to amplify the low-level output signal of the transducer so that it can drive the output stages.

9. General purpose op-amps are used in applications as

A. Instrumentation amplifier
B. Differential instrumentation amplifier
C. Inverting instrumentation amplifier
D. Non-inverting instrumentation amplifier

Answer: B

When the requirement for the application is not too strict. The general purpose op-amp can be employed in the differential mode. Such amplifiers are called Differential instrumentation amplifiers.

10. In an instrumentation amplifier using a transducer bridge, which device measures the change in physical energy

A. Resistive transducer
B. Indicating meter
C. Capacitive transducer
D. Inductor circuit

Answer: A

A resistive transducer is used to measure the change in the same physical energy, which is connected to one arm of the bridge.

11. The temperature of a thermistor increases, when the value of its resistance

A. Remain constant
B. Increase
C. Decrease
D. Depends on the heating material

Answer: C

The thermistor is a semiconductor that behaves like a resistor, with a negative temperature coefficient of resistance. As the temperature of the thermistor increases, its resistance decreases.

12. Consider the entire resistors in the bridge circuit are equal. The resistance and change in resistance are given as 3kΩ and 30kΩ. Calculate the output voltage of the differential instrumentation amplifier?

A. 4.95v
B. 1.65v
C. 8.25v
D. 14.85v

Answer: B

The output voltage of the circuit is

V_o =-(R_F/R₁)×(△R/R)×V_dc

= (5.5kΩ/100Ω)×(30kΩ/3kΩ)×3 = 1.65v.

13. Consider a thermistor having the following specifications: R_F=150kΩ at a reference temperature of 35^oC and temperature coefficient of resistance = 25^oC. Determine the change in resistance at 100^oC.

A. -1.625MΩ
B. 9.75MΩ
C. 4.78MΩ
D. None of the mentioned

Answer: A

Thermistor has a negative temperature coefficient of resistance.

Therefore, △R=-(25kΩ/^oC )×(100^oC-35^oC. = -1625kΩ .

△R=-1.625MΩ.

14. Consider the given bridge circuit, and find the voltage across the output terminal, V_ab.

A. V_ab = 4.9v
B. V_ab = -5.6v
C. V_ab =1.2v
D. V_ab =-8.2v

Answer: A

According to the voltage divider rule,

V_a =( R_a×V_dc)/[R_a+(R_T+△R)]

= (1kΩ×5v)/(1kΩ+75kΩ) = 0.065v

V_b = ( R_b×V_dc)/(R_b+R_c)

= (50kΩ×5v)/(50kΩ+250Ω) = 4.975v

The voltage across the output terminal of the bridge, V_ab = V_a– V_b = 4.9v.

15. Express the equation for the transducer bridge, if all the resistor values are equal

A. v=-(△R×V_dc)/(2×R+△R)
B. v=-(△R×V_dc)/2×(R+△R)
C. v=-V_dc/[2×(2×R+△R)].
D. v=-(△R×V_dc)/ [2×(2×R+△R)].

Answer: D

If the R_a=R_b=R_c=R_T=R(Equal), then the output voltage across the bridge terminals of the transducer bridge is

v=-(△R×V_dc)/ [2×(2×R+△R)].

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