高精度三线制热电阻检测方法研究

Research on high precision measurement of 3-wire thermal resistance

介绍了一种恒压分压法精密测量三线制热电阻阻值的方法，使用精密放大器OPA334与24位分辨率∑-△型A／D转换器AD7714Y设计了简洁的输入检测电路。检测过程补偿了导线电阻影响、接触热电势影响及放大器输入漏电流等误差因素。介绍了测量电路自身基准参数的数字校准方法。对于Pt100热电阻，检测分辨率达到0．001Ω，在0～400℃范围内，热电阻测量的绝对误差小于0．01Ω。该测量方法具有精度高、量程宽、成本低及低功耗等特点，能够广泛应用于各类高精度测温仪表。

An accurate method with constant voltage detection for precision measurement of three-wire thermal resistance is presented. In addition, a compact input detection circuit is designed using OPA334 and 24 bit ∑-△ style A/D 7714 converter. Lead resistance, contact thermo-electric voltage and leakage current in amplifier input are all com-pensated very well in the whole detection process. Digital calibration method for reference variables in detection circuit is presented. For Pt100 thermal resistance, the detection resolution is up to 0.001Ω; the absolute error for the thermal resistance measurement is less than 0.01Ω in the temperature range of 0-400℃. The proposed method features high precision, wide measurement range, low cost and low-power, which can be widely used in all high precision temperature measurement and control instruments.