1762-IR4 Temperature Jumping

[Heater]

I was wondering if someone could give me a hand with an issue I have been having.

I am using a 1762-IR4 input card for a PT100 3-wire RTD. The temperature input has been fine the past few years since it was installed originally. The RTD is in a cooler, where the temperature is consistently 2 Celsius (this has been verified with thermometer in the room). The reading I get will be fine for a few hours, then all of a sudden jumps to -70 or a large number that is not close to correct. The RTD its self has been replaced, the wiring has been replaced. I measure the correct resistance where the connection to the card is. but the input keeps jumping around. The card channel configuration is fine.

Any suggestions would be great.

 

[alan_505]

Are you able to try a different input to see if it is a faulty input channel.

 

[Heater]

Yes, I tried another input on the card. Same things was happening

 

[MaxK]

If the 1762-IR4 inputs are galvanically isolated, I would try to leave the RTD and wiring on one input, and connect any (50-250 Ohm) resistor directly to the other input. If there is a jumps at both the sensor input and the resistor input, then the problem is on the 1762-IR4 side, otherwise on the wiring and sensor side.
In case you described, it's usually a wiring issue. Are you absolutly sure in all connections, that the cable does not touch current-carrying parts, is not in the zone of electromagnetic fields?