Which fault typically causes intermittent RTD readings?
A. Excess immersion depth
B. High process pressure
C. Loose connection
D. Thermowell failure
View Answer
Answer: C
Explanation:
A loose electrical connection is one of the most common causes of intermittent RTD readings.
When a terminal, junction box connection, transmitter terminal, or cable connection becomes loose, the RTD circuit resistance can change unpredictably, causing the temperature reading to fluctuate or drop in and out.
Common Symptoms of a Loose Connection
Fluctuating temperature readings
Sudden spikes or drops in temperature
Intermittent sensor fault alarms
Unstable transmitter output
Readings changing when cables are moved
Common Locations for Loose Connections
- RTD terminal head
- Junction box terminals
- Marshalling panels
- Transmitter terminals
- Cable glands and connectors
Why the Other Options Are Incorrect
Excess immersion depth
- Usually improves measurement accuracy.
- Does not cause intermittent readings.
High process pressure
- May affect sensor life but does not typically cause intermittent signals.
Thermowell failure
- Can damage the sensor or create process issues, but intermittent readings are more commonly caused by wiring or connection problems.
Because poor electrical continuity causes the measurement signal to appear and disappear intermittently, Option C (Loose connection) is the correct answer.