Power Supplies & Barriers

Power Supplies & Barriers

Power supplies and barriers are DIN‑rail system components that condition and protect the electrical interface between field instruments and control systems. They provide reliable transmitter power, galvanic isolation, and - where required - intrinsic safety separation for signals entering or leaving hazardous areas. In modern marshalling architectures, they also act as “signal hygiene” devices that improve loop robustness and diagnostic clarity.

Typical functions include supplies for 2‑wire and 4‑wire transmitters, isolating amplifiers, and barrier modules that safely separate 4–20 mA circuits. Active barriers incorporate their own power supply to feed the loop and pass a galvanically isolated signal onward. Passive barriers transfer loop power from the safe area into the hazardous area and return the measurement signal without needing a separate power source. Options with bidirectional, HART‑transparent paths allow digital communication to pass for configuration, troubleshooting, and device status monitoring without breaking the loop.

The key benefits are protection, availability, and maintainability. Galvanic isolation reduces the impact of ground potential differences and electrical noise, protecting sensitive I/O and improving signal quality. Line fault detection, relay alarming, and optional HART monitoring make intermittent issues easier to locate and reduce time‑to‑repair. Wide‑range power inputs and international approvals support consistent designs across diverse installations.

Integration is straightforward in control cabinets and remote I/O marshalling. Modules are commonly organized by loop, making it easier to standardize wiring, isolate problems, and apply consistent grounding and shield practices. Redundant 24 VDC feed modules and fault-message monitoring can improve availability in critical areas. Because the barrier layer becomes part of the measurement loop, selection should account for required loop voltage, HART impedance needs, and any functional safety constraints.

Typical applications include supplying head transmitters in temperature assemblies, isolating analog outputs to PLC/DCS inputs, extending HART diagnostics through barrier layers, and enabling safe signal transfer from intrinsically safe field devices. They are widely used wherever hazardous-area segregation, signal isolation, and robust loop power are required.

Forberg Smith, an exclusive authorized representative of sales and service for Endress+Hauser.