Indicators & Alarm

Indicator and alarm units are used in industrial automation panels for local display of process variables, limit supervision, and actuation of alarm or interlock outputs. Typical applications include temperature, pressure, level, force, voltage, current, and differential measurement loops where an independent field or panel indication is required upstream of a PLC, DCS, or data logging system.

This category includes Gefran 4A, 4T, 40A, 40B, 40T, 40TB, 650L, 1250L, and 2400 units. The 4A 48-96 series consists of microprocessor-based indicators in 48×48 and 96×48 DIN formats, with IP65 front protection, 3 or 3/4 digit display, and direct AC input capability for voltage ranges 0–2, 0–20, 0–200, and 0–500 Vac, and current ranges 0–20, 0–50, and 0–200 mAac, plus 0–1 and 0–5 Aac, without the need for an external shunt or adapter.

Gefran 650L and 1250L are used as safety limit indicators in processes where a limit exceedance must remain latched until manual acknowledgement, digital input reset, or serial communication reset is performed. They support universal input for thermocouples, RTDs, and linear current or voltage signals, with relay or logic outputs, RS485 Modbus RTU communication, 60 ms sampling time, sensor diagnostics, and alarm event counters for maintenance planning and fault tracking.

The Gefran 2400 is a 96×48 indicator/alarm unit intended for signals with rapid variation. It provides two main analog inputs, two auxiliary analog inputs, two digital inputs, and up to four relay or logic outputs. Additional functions include differential measurement, peak memory, failsafe alarm logic, and optional serial communication via RS485 Modbus RTU or Profibus DP.

Selection should be based on sensor type, input range, latch reset requirement, number of setpoints, output type, supply voltage, front protection rating, communication protocol, response time, and calibration procedure. In critical process duties, the alarm unit should be assessed as part of the protection chain rather than treated as a simple digital indicator.