The Extech 412440-S current loop checker is a low cost, pocket-sized checker for simulating current loops. Featuring the ability to instantly determine if your device needs calibration, the Extech 412440-S current loop checker is ideal for checking calibration and as a current source for setting up engineering units on a process indicator or controller. The Extech 412440-S current loop checker simulates output ranges of 4mA, 12mA, and 20mA from the transmitter.