Thank you for the reply on this. Horner Electric suggested grounding the shield at the PLC input module but neglected to mention grounding all unused inputs to ground which I haven't tried yet. Groundng in the field would be risky. The field location has high energy globars connected to SCR...
I have interference on analog inputs to a PLC via a thermocouple input module. There are 8 inputs, we are using 4 on this particular module. They are foil shielded type K T/C's. When the furnace zone approaches the set point temperature (~900°C) ONLY the 1st channel input starts fluctuating...
