Field device with latching relay

Abstract

A field device for an industrial process includes a digital isolator which electrically divides the field device into a primary side for low voltage electronics from a secondary side. A device power supply located in the secondary side is configured to provide power to a process control device which monitors or controls a process variable of the industrial process. A latching relay located in the secondary side couples to the process control device and the device power supply and has a set input to responsively couple the device power supply to the process control device and a reset input which causes the latching relay to enter an electrically open state to thereby disconnect the device power supply from the process control device. A controller located in the primary side is configured to generate a switch signal. The digital isolator extends between the primary side and the secondary side and couples to the switch signal from the controller and provides a digital output on the secondary side in response to the switch signal. Edge triggered circuitry couples to the digital output of the digital isolator and provides a pulse output to the reset input of the latching relay in response the digital output of the digital isolator.