Isolated 4-Channel, Thermocouple/RTD Temperature Measurement System with 0.5 degree-C Accuracy based on ADT7310

Application Circuit is a completely isolated 4-channel temperature measurement circuit optimized for performance, input flexibility, robustness and low cost. It supports all types of thermocouples with cold junction compensation and any type of RTD (resistance temperature detector) with resistances up to 4k-Ohm for 2, 3, or 4-wire connection configurations. The RTD excitation current are is programmable for optimum noise and linearity performance. RTD measurements achieve 0.1 degree-C accuracy (typical) and Type-K thermocouple measurements achieve 0.05 degree-C typical accuracy because of the 16-bit ADT7310 digital temperature sensor used for cold-junction compensation. The circuit uses a four-channel AD7193, 24-bit sigma-delta ADC with on-chip PGA for high accuracy and low noise