Power Supplies & Barriers

Power Supplies & Barriers

Power supplies and barriers form the electrical “conditioning layer” between sensors/transmitters and the control system. They provide stable loop power where required and, critically, ensure galvanic isolation so 4–20 mA signals are transferred cleanly between circuits and zones. In hazardous-area designs they support safe separation while still allowing the measurement signal - and often digital overlays - to pass reliably.

The portfolio typically includes transmitter power supplies for 2‑wire and 4‑wire instruments, plus active and passive barriers selected by the loop topology. An active barrier supplies the transmitter (including in Ex areas when required) and transmits the galvanically isolated signal; a passive barrier is used when a controller supplies the loop, passing supply into the Ex area and returning the 4–20 mA signal without requiring its own power supply.

Diagnostics capability is increasingly important. Optional HART® transparency and monitoring allow bidirectional communication and status access while the analog loop is isolated, and brief or intermittent errors can be identified through monitored status rather than guesswork. Many solutions integrate the HART resistor and provide communication sockets to simplify configuration access from the cabinet, reducing wiring variability and improving maintainability.

Benefits include improved signal integrity, reduced risk of ground loops, and better fault containment between plant areas. Galvanic isolation and early-warning style sensor monitoring can prevent nuisance trips and reveal degradation before it becomes a failure. Selection and design usually focus on loop loading and compliance voltage, required approvals, separation requirements, and whether alarming relays or monitoring outputs are needed for the maintenance strategy.

Typical applications include powering head transmitters in temperature assemblies, isolating analog inputs in large distributed systems, interfacing Ex-area sensors to non-Ex control rooms, and maintaining HART access for configuration and diagnostics without compromising intrinsic safety. They are also common in marine and other approval-driven environments where standardized separation and robust power conditioning are mandatory.

Field Instruments & Controls, Inc. an exclusive authorized representative of sales and service for Endress+Hauser.