Multi-wire self-diagnostic thermocouple

摘要

A multi-wire self-diagnostic thermocouple having three thermocouple elements enclosed in a sheath and insulated therefrom. The three thermocouple elements are electrically connected to each other to form three thermocouple junctions. An electronic circuit response to the three EMF signals generated by the three thermocouple junctions generates an error signal when the ratio between the three EMF signals differs from predetermined ratios signifying that the calibration of at least one of the three thermocouple elements has changed. In the preferred embodiment, the sheath is a metal sheath and the three thermocouple elements are fused to each other and to the metal sheath.