Loop calibrators are a type of electrical calibrator specifically designed to troubleshoot 4-20 mA current loops. Current loops are extremely common in industrial measurement and control applications due to their ease in setting up, wide power supply requirements, low noise output, and ability to be transmitted over great distance without loss. Loop calibrators are capable of measuring current, sourcing current to unpowered devices in a loop, as well as simulating the operation of loop-powered 4-20 mA transmitters.