This set of Linear Integrated Circuit Multiple Choice Questions & Answers (MCQs) focuses on “Instrumentation Amplifier – 3”.
1. Strain gage are used to monitor change in
d) All of the mentioned
Explanation: A strain gage may be used to monitor change in applied pressure, torque and displacement by measuring the corresponding change in the gage resistance.
2. Which type of resistive transducer is most commonly used?
b) Photoconductive cell
c) Strain gage
d) All of the mentioned
Explanation: Thermistors are most commonly used because they are relatively easy to mount.
3. What is the unit of strain gage?
c) Newton / meter^2
Explanation: Strain gage changes resistance when an external stress is applied. Therefore, the stress is defined as force/unit area i.e. Newton / meter^2.
4. Which type of strain gage has better resolution?
a) Semiconductor strain gage
b) Wire strain gage
c) Wire and Semiconductor strain gage
d) None of the mentioned
Explanation: Semiconductor strain gage are much more sensitive than wire type and so, it provide better accuracy and resolution.
5. How a differential instrumentation amplifier using 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 thermistor by light intensity meter
Explanation: 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 output of the differential instrumentation amplifier drives a relay that controls the current on the heat generating circuit.
6. 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
Explanation: The strain gage elements are mounted in the base of the weight platform. So, that whenever external force or weight is applied to the platform, one pair of element in the opposite arm of bridge elongates, whereas the other pair in opposite arm compresses.
7. What will be the resultant circuit, when the thermistor in the bridge transducer is replaced by a strain gage?
a) None of the mentioned
b) Light intensity
c) Analog weight scale
d) Differential input and differential output amplifier
Explanation: By connecting a strain gage in the transducer bridge, the differential instrumentation amplifier circuit can be converted in a simple and inexpensive analog weight scale.
RT1, RT2, RT3, RT4 are unstrained gage resistance. If the resistance change in each gage is 0.3Ω. Choose the correct option?
1. RT1 and RT3 increases by 0.3Ω
2. RT2 and RT4 decreases by 0.3Ω
3. RT1 and RT3 increases by 0.3Ω
4. RT2 and RT4 decreases by 0.3Ω
a) 3 and 4
b) 1 and 2
c) 1 and 4
d) 2 and 3
Explanation: When external weight is applied to the platform. One pair of element elongate and the other pair compresses. Therefore, RT1 and RT3 is △R and the increase in RT2 and RT4 is also by △R.
9. The gain of the differential amplifier is -125. Assume the voltage applied to bridge circuit Vdc=+10v and the unstrained resistance of four element of strain gage is 200Ω. When a certain weight is placed on the platform, the output voltage Vo=5v. Determine the change in resistance of each strain gage for analog weight scale. (Assuming the output is initially nulled).
Explanation: The output voltage of analog weight scale, Vo = Vdc×(△R/R)×(RF/R1)
=> △R=( Vo/ Vdc)×(R1/RF)×R =( 5v×200Ω)/(125×10v) =0.8Ω.
10. Assume that the increase and decrease in the resistance of the strain gage element is by the same number of △R. Determine the unbalanced voltage equation.
a) V= – Vdc×(△R/R)
b) V= – Vdc×(△R/R+△R)
c) V= Vdc×(△R/R)
d) V= – Vdc×[(△R+ R)/R] View Answer
Explanation: When the unstrained gage resistance are same, then the output voltage of the strain gage bridge circuit (unbalanced voltage) is given as V= -Vdc×(△R/R).
Sanfoundry Global Education & Learning Series – Linear Integrated Circuit.