New Digital Linearization Technique for Thermocouples

Abstract

A digital technique has been developed and tried successfully to linearize highly non-linear low level output of different thermocouples- J, K, T, E, R and S. In this technique, different gains required for different segments of a thermocouple curve have been realized digitally by modifying the conventional “Dual Slope” analog to digital converter. The different gains required for different segments decided through control logic, have been achieved by varying the charging period in terms of counts. This technique has eliminated the various shortcomings of the earlier technique of linearization in which variable gains arc realized through the precision amplifier and demultiplexer. This technique ensures better linearization by varying digitally the different gains needed for increased number of segments. Besides this, the cost has been reduced and long term stability has improved considerably. The technique described can successfully be translated into a custom built “Thermocouple Processor” micro-chip.