Thermocouple Temperature Measurement System with Amplifier-Based Cold Junction Compensation

Application Circuit is a complete thermocouple signal conditioning circuit with cold junction compensation followed by a 16-bit sigma-delta analog-to-digital converter (ADC). The AD8495 thermocouple amplifier provides a simple, low cost solution for measuring K type thermocouple temperatures, including cold junction compensation. A fixed gain instrumentation amplifier in the AD8495 amplifies the small thermocouple voltage to provide a 5 mV/oC output. The high common-mode rejection of the amplifier blocks common mode noise that the long thermocouple leads can pick up. For additional protection, the high impedance inputs of the amplifier make it easy to add extra filtering. The AD8476 differential amplifier provides the correct signal levels and common-mode voltage to drive the AD7790, 16-bit ADC