As part of a Foundation fieldbus infrastructure, device couplers or isolated device couplers (where applicable) are installed where the fieldbus trunk (i.e., home run cable) is connected to the various device spurs. Isolated device couplers are specifically designed to allow automation end users to connect more devices per coupler while permitting live segment work in hazardous plant areas. These couplers provide isolated, conditioned power to multiple fieldbus devices and protect against short circuits caused by excess current in a spur. By enabling more devices per segment, they also help reduce controller input/output (I/O) points and associated installation costs.
The Foundation fieldbus device coupler test specification includes criteria from the international IEC 61158 standard and additional functional tests such as input impedance, short-circuit reaction time, and bus voltage consumption.
The specification is designed for coupler manufacturers to perform a standard set of tests against their implementation.