Low-Cost Noise-Immune Isolated Thermocouple Signal Processor

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This application report describes a low-cost, thermocouple-based, temperature measurement system featuring high-noise immunity and electrical isolation between the analog and digital circuits. Unlike conventional designs employing analog cold junction compensation, in this design the thermocouple is connected directly to the differential inputs of an INA326 instrumentation amplifier. This configuration takes advantage of the high (>90 dB) CMRR (commnon mode rejection ratio) of the instrumentation amplifier.