Grounded Thermocouple

Using a multi-meter set to ohms (Ω), you can perform a continuity test between a lead end/plug pin and the outer sheath tip of the thermocouple probe:

A grounded thermocouple is a closed circuit and has a fluctuating reading of continuity when the multi-meter probes are placed on a pin/lead wire and the outer sheath tip of the thermocouple probe.  Certain multi-meters will also have an audible “beep” when continuity is present.  You may have to firmly touch the probe in a couple of different spots on or around the end of the probe sheath to get a reading on a grounded thermocouple.

Ungrounded Thermocouple

An ungrounded thermocouple is an open circuit and indicates no continuity.  The multi-meter will show a “0” or “1” reading when the multi-meter probes are placed on a pin/lead wire and the outer sheath tip of the thermocouple probe.  You may have to firmly touch the probe in a couple of different spots on or around the end of the probe sheath to verify there is no continuity.