Current Sensing Relay (IR) - NORD Drivesystems PDF fileCurrent Sensing Relay (IR) The current sensing relay, is used to achieve a fast brake engagement (stopping) without the use of external control equipment or additional wiring. The relay is mounted directly on the conduit box, and is powered from the motor’s terminal block. Current sensor switch circuit - Gadgetronicx Current sensors are used when there is a need to measure the amount of current consumed by a certain appliance or device. There are several methods to measure the current flow and we are about to use Hall effect in our Current sensor switch circuit. IC ACS712 a simple linear current sensor form the most significant part of this circuit.