Thermocouple. Th? thermocouple is a security machine t?at detects w?ether ?our furnace's pilot light-weight is lit. The thermocouple incorporates ? steel rod that is definitely put quite shut t? the pilot gentle'? flame. Thermocouple. ?he thermocouple or flame sensor i? a little metallic product positioned in the flame path ?file t?e pilot light-w