This CR Magnetics current sensing relay has an internal transformer, requires a supply voltage of 120VAC, and is used for monitoring electrical current in power supply applications. This current sensing relay has a window for routing the current-carrying wire and a calibrated dial for setting the trip point. An adjustable delay-on timer provides stability. When current levels rise above the adjusted set point, the relay is tripped and starts the timer. Once the timer cycles, the relay is energized and turns the output to full on. It has an internal transformer for scaling the current up or down and a voltage reference circuit that provides a repeatable trip point. This current sensing relay has an LED indicator that alerts the user when the relay is tripped and is suitable for monitoring electric heater elements, sensing motor over/under loads, detecting lamp burn-out and indicating phase-loss.SpecificationsContact form1 Form C (SPDT)Contact materialSilver-cadmium oxideSupply voltage120VACPower-on delay100 ms. maximumInput supply power80 mA normal; 100 mA maximumRated output20 amps maximumMaximum sensed currentContinuous 200% full scaleHysteresis5% maximumMechanical life10 million operations at normal rated loadElectrical life100,000 operations at normal rated loadInitial contact resistance50 milliohms maximum at 500 mA, 12VDCFrequency (at 60 Hz)50 to 400 HzOperating temperature-30 to +60 degrees CStorage temperature-55 to +85 degrees CTerminals3 1/4" male QCWeight0.05 lb.Standards metUL (Underwriter's Laboratories)RoHS (Restriction on Hazardous Substances)Relay switches (also called an electrical relay or an electrical relay switch) use a small amount of power to control a larger source of power connected to electrical devices such as car motors, computers, and lighting installations. A basic relay switch has a control circuit with an electromagnetic coil and a load circuit with contacts and a lever. When current flows into the relay switch, it moves through the coil and a magnetic field is created, which causes the lever in the load circuit to move between contacts, either turning the device on or off. In a normally open (NO) relay switch, when power is supplied to the relay, the load circuit is closed and the power source connected to the relay is turned on. In a normally closed (NC) relay switch, when power is supplied to the relay, the load circuit is open and the power source connected to the relay is turned off. In other types of relay switches, non-moving parts such as transistors or semiconductors can be used as the control circuit to operate the switching mechanism. Relay switches can be controlled with an external switch, such as a light switch, or they can be connected to an automatically switched power source, such as a car ignition. One relay can operate multiple switches, and multiple relays can be operated with a single switch, with each relay operating independently from the other relays in the system.CR Magnetics manufactures electrical sensors, indicators, and displays. The company, founded in 2004, is headquartered in Saint Louis, MO.