The Fieldbus Foundation today announced registration of the first isolated device couplers based on its FOUNDATION H1 (31.25 kbit/s) device coupler test specification. Devices from MTL and R. Stahl successfully completed the foundation's rigorous registration process.

 As part of a FOUNDATION fieldbus infrastructure, isolated device couplers 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.

MTL's 9370-FB Series Fieldbus Barrier provides a range of complete integrated enclosure systems, instead of stand-alone barrier modules. All internal components are live pluggable, meaning that field maintenance can be carried out quickly and safely. Surge protection devices for the trunk and spurs can be easily fitted without requiring product re-design. The product series includes 6- and 12-spur versions in stainless steel or GRP enclosures, as well as a redundant option enabling improved system availability in critical fieldbus networks.

R. Stahl's Series 9411/21 and 9411/24 isolated device couplers are suitable for use in Zone 1, Zone 2 and U.S. Division 2, and are available with plastic or stainless steel housings that can be tailored to fit customer requirements. The series also includes a unique power management feature: during the start-up of a fieldbus segment, the spurs energize one after the other. This reduces the inrush current on a segment by up to 50 percent, requiring less spare energy and making longer segment lengths possible.

The Fieldbus Foundation's Stephen Mitschke, director-fieldbus products, commented, "The device coupler test specification provides a high level of robustness in fieldbus systems. And recent enhancements to the FOUNDATION fieldbus physical layer specifications provide end users with greater confidence that registered fieldbus equipment can be employed in a tightly integrated, interoperable control system architecture that is well suited to the most demanding industrial environments," Mitschke said.