Power Engineering 4A - Unit 9 - Plant Instrumentation Most Recent exam
COMPLETE (2026) EXAM Questions and Answers (Verified Answers) (Latest
Page | 1
Update 2026)
1. What is the purpose of the primary element in an instrumentation system?
A. To transmit the output signal
B. To detect the process variable
C. To amplify the signal
D. To perform the final control action
Rationale:
The primary element senses the variable (pressure, temperature, etc.) and is the first part of the
measurement chain.
2. A standard pneumatic signal uses what pressure range?
A. 0–5 psi
B. 20–100 kPa (3–15 psi)
C. 40–80 kPa
D. 10–20 psi
Rationale:
Industrial pneumatic controllers and valves use 3–15 psi as a universal control signal.
3. A 4–20 mA signal represents:
A. Mechanical signal
B. Pneumatic pressure
C. Standard electrical analog signal
D. Hydraulic pressure
Rationale:
4–20 mA is the global standard for electrical instrumentation signaling.
4. Which type of control provides the fastest response to error?
A. Proportional
B. Integral
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, C. Derivative (D) control
D. On/Off
Rationale:
Derivative control reacts to the rate of change, providing rapid correction.
Page | 2
5. A bourdon tube is used to measure:
A. Temperature
B. Flow
C. Pressure
D. Level
Rationale:
Bourdon tubes convert pressure into motion and are common in pressure gauges.
6. Thermocouples operate based on:
A. Change in resistance
B. Change in density
C. Seebeck effect (voltage from temperature difference)
D. Viscosity change
Rationale:
Thermocouples generate a voltage proportional to temperature differences.
7. An orifice plate measures flow by creating:
A. Turbulence
B. Heat
C. A pressure drop across a restriction (ΔP)
D. Electrical current
Rationale:
Flow is calculated using differential pressure across the orifice.
8. The final control element in most processes is the:
A. Sensor
B. Controller
C. Control valve
D. Transmitter
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, Rationale:
Valves implement the controller’s output by adjusting flow.
9. What does proportional band represent?
Page | 3
A. Temperature range of an RTD
B. Pressure range of the process
C. Range of error over which controller output changes proportionally
D. Flow range of the orifice plate
Rationale:
Proportional band is the span in which the controller regulates via proportional action.
10. A DP cell used for level measurement works by:
A. Measuring sound waves
B. Comparing pressures at bottom and top of vessel
C. Measuring light reflection
D. Weighing the tank
Rationale:
Level causes hydrostatic pressure differences, measured by DP cells.
11. Which device is most accurate for high-temperature measurement?
A. Thermistor
B. RTD
C. Thermocouple (Type K)
D. Dial thermometer
Rationale:
Thermocouples withstand extremely high temperatures.
12. A controller that cycles fully open and closed only is:
A. P controller
B. On/Off controller
C. PID controller
D. I controller
Rationale:
On/Off provides no proportional action—only two states.
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, 13. A valve with equal percentage characteristic:
A. Opens fully with small signal
B. Provides constant change per signal
Page | 4 C. Gives small flow change at low opening, larger at high opening
D. Used for emergency shutdown
Rationale:
Equal percentage valves are used where flow increases exponentially with lift.
14. A pneumatic actuator uses what medium?
A. Steam
B. Compressed air
C. Oil
D. Water
Rationale:
Compressed air is the standard medium for control valves.
15. A pitot tube measures:
A. Static pressure
B. Dynamic pressure
C. Velocity head for flow measurement
D. Valve position
Rationale:
Pitot tubes measure velocity via dynamic pressure.
16. Purpose of a positioner on a control valve:
A. Measure flow
B. Amplify a pneumatic signal
C. Ensure valve moves to exact position commanded by controller
D. Record valve operation
Rationale:
Positioners improve valve accuracy and overcome friction.
EXAMPREPMASTER
COMPLETE (2026) EXAM Questions and Answers (Verified Answers) (Latest
Page | 1
Update 2026)
1. What is the purpose of the primary element in an instrumentation system?
A. To transmit the output signal
B. To detect the process variable
C. To amplify the signal
D. To perform the final control action
Rationale:
The primary element senses the variable (pressure, temperature, etc.) and is the first part of the
measurement chain.
2. A standard pneumatic signal uses what pressure range?
A. 0–5 psi
B. 20–100 kPa (3–15 psi)
C. 40–80 kPa
D. 10–20 psi
Rationale:
Industrial pneumatic controllers and valves use 3–15 psi as a universal control signal.
3. A 4–20 mA signal represents:
A. Mechanical signal
B. Pneumatic pressure
C. Standard electrical analog signal
D. Hydraulic pressure
Rationale:
4–20 mA is the global standard for electrical instrumentation signaling.
4. Which type of control provides the fastest response to error?
A. Proportional
B. Integral
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, C. Derivative (D) control
D. On/Off
Rationale:
Derivative control reacts to the rate of change, providing rapid correction.
Page | 2
5. A bourdon tube is used to measure:
A. Temperature
B. Flow
C. Pressure
D. Level
Rationale:
Bourdon tubes convert pressure into motion and are common in pressure gauges.
6. Thermocouples operate based on:
A. Change in resistance
B. Change in density
C. Seebeck effect (voltage from temperature difference)
D. Viscosity change
Rationale:
Thermocouples generate a voltage proportional to temperature differences.
7. An orifice plate measures flow by creating:
A. Turbulence
B. Heat
C. A pressure drop across a restriction (ΔP)
D. Electrical current
Rationale:
Flow is calculated using differential pressure across the orifice.
8. The final control element in most processes is the:
A. Sensor
B. Controller
C. Control valve
D. Transmitter
EXAMPREPMASTER
, Rationale:
Valves implement the controller’s output by adjusting flow.
9. What does proportional band represent?
Page | 3
A. Temperature range of an RTD
B. Pressure range of the process
C. Range of error over which controller output changes proportionally
D. Flow range of the orifice plate
Rationale:
Proportional band is the span in which the controller regulates via proportional action.
10. A DP cell used for level measurement works by:
A. Measuring sound waves
B. Comparing pressures at bottom and top of vessel
C. Measuring light reflection
D. Weighing the tank
Rationale:
Level causes hydrostatic pressure differences, measured by DP cells.
11. Which device is most accurate for high-temperature measurement?
A. Thermistor
B. RTD
C. Thermocouple (Type K)
D. Dial thermometer
Rationale:
Thermocouples withstand extremely high temperatures.
12. A controller that cycles fully open and closed only is:
A. P controller
B. On/Off controller
C. PID controller
D. I controller
Rationale:
On/Off provides no proportional action—only two states.
EXAMPREPMASTER
, 13. A valve with equal percentage characteristic:
A. Opens fully with small signal
B. Provides constant change per signal
Page | 4 C. Gives small flow change at low opening, larger at high opening
D. Used for emergency shutdown
Rationale:
Equal percentage valves are used where flow increases exponentially with lift.
14. A pneumatic actuator uses what medium?
A. Steam
B. Compressed air
C. Oil
D. Water
Rationale:
Compressed air is the standard medium for control valves.
15. A pitot tube measures:
A. Static pressure
B. Dynamic pressure
C. Velocity head for flow measurement
D. Valve position
Rationale:
Pitot tubes measure velocity via dynamic pressure.
16. Purpose of a positioner on a control valve:
A. Measure flow
B. Amplify a pneumatic signal
C. Ensure valve moves to exact position commanded by controller
D. Record valve operation
Rationale:
Positioners improve valve accuracy and overcome friction.
EXAMPREPMASTER
