Mysterious middle of the night noise in RTD causing damage? Induced AC current?

[TTM2]

See attached log of RTD data.

9 RTDs in close proximity. 3 start acting very strange in the middle of the night for ~10 minutes, and it appears to cause damage to one which reads ~60C low the next day (of course screwing up all operation). 100 Ohm Pt element, 3 wire.

We're trying to diagnose this reading. The RTD lines are on a 120ft+ run up a steel galvanized tower. I can't say for certain how the wires are shielded right now.

I post in this forum to get some perspective on electrical noise caused by nearby AC power lines. There are 410 AC inputs nearby in cabinets powering ground equipment, although no powered lines are following the RTD runs up. Had anyone ever seen induced currents damaging RTDs?

 

[itsmoked]

Was there lightning?

Was there rain the night of the "change".

Has the power usage up the tower tower changed dramatically?

How are these RTDs being read?
Each read separately, or thru one device that could be malfunctioning?

What are the RTDs being used to measure exactly?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

The weirdest RTD signals I've ever seen.

Going positive AND negative and one very linear ramp. Over minutes. Those are no external or internal transients - unless the recorder has some kind of glitch-catching function.

Gunnar Englund

http://www.gke.org

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