Temperature fluctuations, RTD is normal
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Recently, there have been three consecutive failures related to temperature fluctuations. The field transmitters in question are Roemont 644 models, mounted on rails inside junction boxes, with the RTDs connected to the transmitters via terminals. Upon on-site wire removal and inspection, the RTD resistance was found to be normal; once it was connected back to the transmitter, the temperature returned to normal. What could be the cause of this? Could it be static electricity?
Electrostatic interference shouldn’t occur normally; after rewiring, did the fluctuations appear 2 times, or 3 times before it was unplugged and rewired again? If it doesn’t appear now, check whether there are issues with the connection or the wiring.
This could be caused by poor terminal contact or electromagnetic interference.
You can try connecting another set of RTDs to see; if the fluctuations persist, it is recommended to shut down the equipment for a thorough inspection, as this could be a sign of mechanical problems!
Is the temperature-sensitive type a shielded cable? Is there no single-point grounding for the shielding layer, and no grounding for the on-site junction box?