I have an application where several of the critical PID loops need to have some sort of manual backup in place in case of system or component failure. The idea would be that if the 4-20 signal from the PID controller (could be a DCS, PLC or single loop) would normally be passed through the backup station. If the controller failed, was removed, etc the manual backup station would either hold the last valid output (preferred) or would default to a previously defined value. In either case, it would need have a switch and pot of some sort that an operator could take control and manipulate the output. I realize that most PLC/DCS systems have the ability to freeze the output on failure .. this is not sufficient for this application.

I could buy the components and build one but my preference would be to find something commercially available. Does anyone know of a company selling something like this?

Thanks.

 

Hello

Try Control Technology Inc. www.cti.knox.tn.us

They have offered a manual backup station for about 20 years, works with PLCs. Not specific to any PLC brand.

Regards,
Al

 

I suggest the CTI Model 7312 Manual Backup Station. www.cti.knox.tn.us.

Product has been available >15 years.

Regards
Al Boake P.E.
[email protected]