Explain the potential free contact
Potential free contact means, Dry contact that has a voltage-free contact .relay, limit switch contact is a potential-free contact.
There will be no Power supply to energize the Output devices (digital output signal) from the DCS panel. Relay control supply on instrument signal card and common supply to NC or NO will be from Electrical panel.
That’s why it can be called a potential free contact
Eg: Motor start/stop signal