What is a common symptom of an open RTD circuit?
A. Low reading
B. Stable reading
C. Sensor fault
D. Fast response
View Answer
Answer: C
Explanation:
An open RTD circuit occurs when the RTD element or its wiring becomes disconnected, causing the resistance measured by the instrument to become extremely high or infinite.
Since the control system can no longer receive a valid resistance value, it typically generates a:
Sensor fault
Open circuit alarm
Bad PV indication
Over-range error message
Common Causes of Open RTD Circuits
- Broken RTD element
- Loose terminal connections
- Damaged extension cables
- Corroded connections
- Broken lead wires
Typical System Indications
Depending on the transmitter, PLC, or DCS:
- Fault message displayed
- Temperature driven upscale or downscale
- Diagnostic alarm generated
- Sensor status marked as bad
Why the Other Options Are Incorrect
Low reading
- More commonly associated with short-circuit conditions.
Stable reading
- An open circuit usually causes a fault indication rather than a valid stable measurement.
Fast response
- Not related to an open RTD circuit.
Because an open RTD circuit is usually detected as a measurement failure, the most common symptom is a sensor fault indication.
Therefore, Option C (Sensor fault) is the correct answer.