Patent ID: 6983223

Claim:
A method of detecting thermocouple failure in a temperature monitoring circuit, the method comprising: inputting and storing manufacturers values for an initial resistance R mo and a temperature coefficient of resistance α for a thermocouple based on the thermocouple part number; measuring a loop resistance LR at an indicated initial temperature T mo ; computing and storing an initial circuit resistance R c of the unsheathed portion of the temperature monitoring circuit, based on the LR measurement and initial temperature T mo ; measuring a current loop resistance LR at a current indicated temperature T m ; computing a thermocouple confidence level % CL based on comparing a predicted LR, to the current measured LR at the current indicated temperature T m according to a thermocouple failure detection algorithm; determining whether the thermocouple confidence level % CL has exceeded a predetermined limit; measuring another current loop resistance LR at the current indicated temperature T m , if the % CL has not exceeded the predetermined limit; generating an alarm for maintenance of the thermocouple, if the % CL has exceeded the predetermined limit; and wherein the limit of the thermocouple confidence level corresponds to an impending thermocouple failure and the prediction thereof.