Methods for testing the ZET 7021 and ZET 7121 measuring units:

With the thermistor disconnected, use an amperemeter or a multimeter in the current measuring mode to check the current between terminals 1 and 3, it should be close to 1 mA.

Check the resistance of the disconnected thermocouple: at ambient temperature it should be close to the NSC (nominal static characteristics) of the thermistor marking.

With the thermistor connected, check the current between terminals 1 and 3, it should be < 1 mA and have a value other than zero. [/av_textblock]