Analog Signal Spikes

Hello everyone,
Im in need of some help and ideas.
Here is my issue
I have an analog signal input go into PLC, and whenever my pump was shutting down, this analog signal always spikes for exact 8mA. stays there for various amount of time. the set up is very simple, analog signal coming out from one of the analog output on a controller, and go into one side of terminal, and other side terminal is go into PLC analog card. I also have only shield ground for one side.

Has anybody run into this issue before?
Really appreciate your helps.

https://www.torexsemi.com/technical-support/tips/reduction-spike-noise/

The above post may help you out.
Regards,

A first step would be to eliminate the terminals in the line and wire directly from the analog source to the analog input. Many times this fixes the issue.

Is the pump on a VSD? Where does your analog signal cable run in relation to the motor cables? I assume this analog is not from a flow meter or pressure sensor which would be directly affected by the pump process.

I would check:

Instrument cable screen grounded only at one end.

Cable routing as far away as possible from motor cables

Inside the panel from the terminals you mention, wire routing path is as short as possible and away from power conductors etc. If that's not possible you may need to take the screened cable directly up to the analog input terminals