Intrinsically safe limit indicators are used to monitor the value of analog signals. A drop in the signal level below the set minimum value (lower threshold) or an increase above the set maximum value (upper threshold) is signaled by a change in the alarm relay state. The devices also have a display showing the current input signal value.
Limit indicators are used in process and technological systems. They can signal when a measured value has been exceeded or regulate the ON/OFF switching of a process based on a measured parameter, e.g., temperature, pressure, level, humidity, etc.