RTD drifting in AB 1746-NR4 module

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Thread Starter

John Marvin

I have an Allen Bradley 1746-NR4 module installed in our system per manual's specs but I am seeing RTD drifting at temperatures above 150F. It will drift as much as 15F. Is there anything special that I can do to fix this? The RTD wire appears to be ok because when we wire it to a 4-20mA transmitter, we don't see the drifting problem.

I've replaced this module already with no success. There's a couple VFDs and starters in the same panel in the panel but it's about 2.5' away so I don't know if there's any EMF or something similiar. The RTD cables are routed away from any motor leads.
 
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Bill Clemons

You might consider adding another wire to the RTD for better resolution of the sensor resistance.
 
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