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Instrumentation & Equipment Maintenance Flashcards

7 cards from real CPT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Instrumentation & Equipment Maintenance flashcards as text

  1. What is the primary purpose of a thermocouple in process instrumentation?

    Answer: Measure temperature by generating a voltage

    A thermocouple generates a small voltage proportional to the temperature difference between its hot and cold junctions, which is used to infer temperature.

  2. A control valve fails to respond to the positioner signal. Which component should be checked first?

    Answer: The instrument air supply pressure

    Insufficient instrument air supply pressure is the most common reason a pneumatic control valve fails to respond to its positioner signal.

  3. What does the term 'dead band' refer to in a control instrument?

    Answer: The range of input change that produces no output change

    Dead band is the range over which an input signal can change without causing a corresponding change in output, and it causes hysteresis in the control loop.

  4. Which maintenance strategy involves replacing components based on their predicted service life before failure occurs?

    Answer: Preventive maintenance

    Preventive maintenance involves scheduled replacement or servicing of equipment at predetermined intervals to prevent unexpected failures.

  5. A pressure transmitter reads higher than expected. After zeroing, the reading is still off-scale. What is the most likely cause?

    Answer: Plugged impulse line

    A plugged impulse line traps pressure and prevents the transmitter from sensing actual process pressure, causing an erroneously high or stuck reading.

  6. What is the function of a seal pot in an impulse line system?

    Answer: Maintain equal liquid head on both impulse lines for accurate DP measurement

    Seal pots maintain equal and constant liquid levels in both high- and low-side impulse lines, ensuring the hydrostatic head cancels out for accurate differential pressure measurement.

  7. When calibrating a 4–20 mA transmitter, what output signal corresponds to 0% of the measurement range?

    Answer: 4 mA

    In a 4–20 mA loop, 4 mA represents 0% of the measurement span, and 20 mA represents 100%, with the 4 mA offset used to detect open-circuit faults.