CCT Troubleshooting & Maintenance of Instruments 2

Question 1

A pressure transmitter consistently reads 2% higher than the reference standard across its full range. This is most likely caused by:

Accepted Answer

Zero offset error

Answer

A consistent offset across the full range indicates a zero shift, not a span or linearity problem.

Question 2

During maintenance of a thermocouple installation, you notice the extension wire has been routed near a high-voltage cable. What is the primary concern?

Accepted Answer

Electromagnetic interference will corrupt the millivolt signal

Answer

Thermocouple signals are low-level millivolt signals highly susceptible to EMI from nearby high-voltage conductors.

Question 3

A differential pressure flow meter shows erratic readings only when the process flow is high. The most probable cause is:

Accepted Answer

Air entrainment at high flow velocities

Answer

At high flow velocities, dissolved gases can come out of solution and cause bubble-induced signal noise in the impulse lines.

Question 4

When troubleshooting a 4-20 mA loop, a technician measures 0 mA with the loop powered. The most likely fault is:

Accepted Answer

Open circuit in the loop wiring

Answer

Zero milliamps in a 4-20 mA loop indicates a broken circuit, since a functioning loop always carries at least 4 mA.

Question 5

A pH electrode exhibits sluggish response during calibration, taking several minutes to stabilize. The most likely cause is:

Accepted Answer

Dehydrated or fouled glass membrane

Answer

A glass pH electrode that has dried out or is coated with process deposits will respond very slowly to changes in hydrogen ion activity.

(CCT) Certified Calibration Technician Practice Test

(CCT) Certified Calibration Technician Practice Test

CCT Troubleshooting & Maintenance of Instruments 2