Process Indicators & Control Units

Process Indicators & Control Units

Process indicators and control units provide local visualization and evaluation of measurement signals, bridging the gap between a transmitter output and on-site action. They indicate analog values, apply scaling and calculations, and present results on high-contrast displays that remain readable in demanding environments. Depending on the device, they also add limit monitoring and simple control functions that complement higher-level control strategies.

A key benefit is clarity at the point of measurement. Universal inputs allow connection of common signal types - current, voltage, RTDs, and thermocouples - so one indicator family can standardize local displays across diverse loops. Loop-powered indicators require no separate supply and can be inserted directly into 4–20 mA circuits, supporting retrofits and intrinsically safe applications where wiring simplicity matters.

The category spans panel-mount and field-mount indicators, loop-powered Ex-capable devices, HART indicators that can display multiple variables from a smart transmitter, and units with control functions such as limit value monitoring, math blocks, and linearization. Fieldbus indicators extend the concept to PROFIBUS PA and FOUNDATION Fieldbus networks, acting as listeners that display values communicated on the bus. Some control units combine functions such as an active barrier, transmitter behavior, and relay outputs in one device.

Typical applications include adding a readable local value where transmitter housings are hard to see, providing a verification point during commissioning, and improving situational awareness in field locations with limited access to control graphics. Control-capable units are used for straightforward interlocks, alarm annunciation, and local limit handling on utilities and auxiliary systems. In bus-based installations, fieldbus indicators display key variables near equipment without additional analog conversion.

Selection should consider mounting and ingress requirements, whether loop-powered operation is desired, and the need for HART or fieldbus compatibility. Approval needs - Ex, SIL, marine, or water protection requirements - often determine the shortlist. Define the desired behavior (pure indication vs. relay actions and math), confirm the input signal mix, and ensure the local display supports, rather than conflicts with, the operating philosophy.

Instrumentation and Controls., an exclusive authorized representative of sales and service for Endress+Hauser.