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    • Reference Design for Isolated 4-Channel, Thermocouple/RTD Temperature Measurement System with 0.5°C Accuracy
    • Reference Design for Isolated 4-Channel, Thermocouple/RTD Temperature Measurement System with 0.5°C Accuracy


    The EVAL-CN0287-SDPZ is an Evaluation Board for the circuit CN0287, Isolated 4-Channel, Thermocouple/RTD Temperature Measurement System with 0.5°C Accuracy.

    The 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 4 kΩ 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°C accuracy (typical), and Type-K thermocouple measurements achieve 0.05°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.

    Input transient and overvoltage protection are provided by low leakage transient voltage supressors (TVS) and Schottky diodes. The SPI-compatible digital inputs and outputs are isolated (2500 V rms), and the circuit is operated on a fully isolated power supply.

    The circuit is designed for precision temperature measurement applications in the industrial field environment and is optimized for flexibility, performance, robustness, and cost. This circuit uses the AD7193, low noise, 24-bit sigma-delta ADC to ensure high resolution and linearity for the entire circuit.

    The AD5201, 33-position digital potentiometer, AD8603 op amp, and ADG702 single channel switch constitute a simple programmable current source and bias voltage buffer for the RTD and thermocouple measurements. The ADG738 routes the current source to the active RTD channel and allows wire resistance compensation for the 3-W RTD configuration.

    The ADT7310 digital SPI temperature sensor has ±0.8°C maximum accuracy (+5 V supply) from −40°C to +105°C and is used for cold-junction compensation for the thermocouple measurement. The ADR3440 is a low noise and high accuracy 4.096 V reference connected to REFIN1(+)/REFIN1(−) of the AD7193 for the thermocouple measurements.

    The EVAL-CN0287-SDPZ circuit board and the SDP-B (EVAL-SDP-CB1Z) system demonstration platform controller boards have 120-pin mating connectors, allowing for the quick setup and evaluation of the performance of the circuit. The EVAL-CN0287-SDPZ board contains the circuit to be evaluated, as described in this note, and the SDP-B controller board is used with the CN0287 Evaluation Software to capture the data from the EVAL-CN0287-SDPZ circuit board.

    Key Applications: Programmable Logic Controllers/ Distributed Control Systems, Temperature Controllers, Electronic Test & Measurement, High Temperature, Avionics


    • 4-Channel Thermocouple/RTD Measurements
    • Fully Isolated
    • Input Protection

    Ships With

    • Evaluation Board

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