Field device switch monitor

An industrial process control system comprising:

• a field device comprising:
• an active component selected from the group consisting of a sensor configured to sense a process parameter, and a control device configured to control a process;
• a switch electrically coupled to first and second terminals and configured to electrically connect the first and second terminals when in a closed state, and electrically disconnect the first and second terminals when in an open state;
• a switch monitor configured to detect a current state of the switch corresponding to one of the closed and open states, and generate a state output indicating the current state;
• and
• a controller configured to set the switch between the open and closed states, and generate a notification based on the state output that indicates at least one of the current state of the switch and a condition of the switch;
• an external device electrically coupled to the switch through the first terminal;
• and
• a power supply electrically coupled to the switch through the second terminal and configured to power the external device through the switch;
• wherein:
• power is supplied to the external device when the switch is in the closed state, and power is disconnected from the external device when the switch is in the open state;
• the switch monitor is configured to detect an electrical parameter indicating the current state of the switch selected from the group consisting of a voltage across the switch and a current through the switch, and generate the state output based on the detected electrical parameter;
• the controller is configured to set the switch in the open or closed state using a switch drive signal;
• the field device includes a comparator circuit;
• and
• the controller generates the notification based on a comparison of the state output to the switch drive signal performed by the comparator circuit.

A method of controlling an external device using an industrial process field device comprising:

• sensing a process parameter of an industrial process or controlling the industrial process using an active component of the field device;
• setting a switch of the field device to a current state corresponding to one of an open state, in which electrical power from an external power supply is disconnected from the external device, and a closed state, in which electrical power from the external power supply is connected to the external device, using a switch drive signal generated by a controller of the field device;
• detecting an electrical parameter indicating the current state of the switch selected from the group consisting of a voltage across the switch and a current through the switch using a switch monitor of the field device;
• generating a state output indicating the current state based on the detected electrical parameter using the switch monitor;
• comparing the state output to the switch drive signal using a comparator circuit of the field device;
• and
• generating a notification based on the comparison using the controller that indicates at least one of the current state of the switch and a condition of the switch.