Thermocouple Condition Monitoring Using Thermocouple Resistance. Experimental Study

Industries apply thermocouples for measurements in a wide range of temperatures with relative error 1-2%. However, thermocouple deterioration results in a dramatic increase in the thermocouple error while in operation. This study suggests a novel algorithm of thermocouple condition monitoring based on variations of thermocouple resistance. The experimental verification of the algorithm has carried out for the chromel-alumel thermocouple. The experimental set-up involves equipment for accurate measurements of thermocouple resistance using the proposed measurement circuit. Also, the set-up allows inducing thermocouple deterioration via applying thermal shocks onto the thermocouple. The experimental results have confirmed the relation between thermocouple resistance and the thermocouple in-service state variations. Also, the experiment has shown the influence of thermal shocks onto the thermocouple in-service state. The proposed algorithm for thermocouple condition monitoring has provided for up to 80% accuracy for determining the deteriorated thermocouple as well as the thermocouple in the healthy state. The study results enhance methods using the information redundancy for thermocouple in-service state monitoring.