Maker - RS Pro, Carlo Gavazzi, Phoenix Contact

Monitoring relays are a type of relay that trips a circuit breaker when a fault is detected. A relay is an electrically controlled switch that is used to turn the power on or off in a circuit. 

Monitoring relays are more sophisticated than regular relays, as they have adjustable operating conditions, whereas normal relays switch according to a fixed threshold. They measure a given parameter, such as voltage or temperature, and will trip a circuit breaker when the parameter gets too high or low.

For monitoring parameters - Frequency, Liquid Level, Speed, Voltage and Thermistor protection relay for motor control circuits.