Hardware Failure of Temperature Transmitter


Thread Starter


Hardware failure found on Honeywell STT25H. During troubleshoot got messages like open circuit, temp sensor broken, etc. While checking element (RTD) it gives good resistance values corresponding to the temperature, taken out checked in the lab also, working good. The service of that temp element is the sea water out line which has a fair amount of vibration & may be some swirling flow. Was not able to find any open or short circuit in the temp element.

Any one facing the same?

Please need some suggestions.
Assuming the RTD is a Pt100, test the transmitter by wiring a 120 ohm resistor, along with whatever jumper(s) needed to simulate whatever the transmitter is configured as, 3 or 4 wire. If the configured LRV is not zero, pick a resistor that will give a reading within the transmitte's configured range.

If the transmitter reads somewhere around 52 deg C (depends on resistor tolerance) then the transmitter is functional.

Look carefully for heavy corrosion or an open circuit (broken wire, bad crimp, loose screw connection) between the RTD and the transmitter. Wiggle the wiring to force an intermittent fault to appear.
I must not have had my coffee yet that morning I replied.

A common RTD failure mode is when the RTD element breaks due to vibration. I've encountered situations where break was not evident in a cold state or when vibration was not present. But the element would open when heated up when vibration was present.