Process Indicators & Control Units

Process Indicators & Control Units

Process indicators and control units are local interface devices that display, evaluate, and—when required—control process signals. They provide immediate visibility of measured values and can also execute basic logic such as limit alarming, simple calculations, linearization, or relay-based control actions.

These instruments commonly accept universal inputs to accommodate current, voltage, RTD, and thermocouple signals, enabling standardization across diverse loops. Large, high-contrast displays improve readability in challenging environments, and local presentation can be critical when the primary transmitter display is obstructed or the measuring point is not easily observed.

Loop-powered indicator variants can operate directly from a 4–20 mA circuit without requiring an additional power supply, which simplifies installation and supports use in intrinsically safe concepts. Fieldbus indicator variants can display values communicated on the bus, extending local visibility into digital architectures without adding analog conversions.

Control-capable versions combine multiple functions—such as barrier behavior, transmitter supply, and relay outputs—into a single device, consolidating panel hardware. This can improve cabinet density and reduce wiring complexity while maintaining clear on-site status and basic safety interlocks.

Typical applications include local display at remote skids, pump/limit control, alarm annunciation, and fieldbus value indication where local confirmation is needed. Selection is usually driven by input type, mounting style (field vs. panel), needed control functions (relay count, math, linearization), bus protocol support, and approval requirements such as Ex or SIL where applicable.

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