普通四线制铂电阻测温系统受恒流源长短期漂移、导线热电动势影响, 其测量准确度难以超过0.1℃量级。本文分析了一种改进型4线制高精度铂电阻测温方法的原理误差, 并设计了相应的高精度铂电阻测温系统。采用温度系数小、阻值稳定性好的参考电阻作为铂电阻阻值测量基准, 消除了恒流源长期漂移引起的铂电阻测温误差; 分别在正、反向恒流激励条件下测量了铂电阻上的电压, 利用导线热电势大小与方向的短期不变性, 对得到的两电压量求差以消除导线热电势的影响; 通过半导体致冷器(TEC)控制恒流源温度来减小恒流源的短期电流漂移, 进而减小其对铂电阻测温精度的影响; 设计了精度高、阶跃响应速度快的分时复用式电压信号采集单元用来高精度地测量铂电阻和参考电阻上电压量的比值。等效实验和校准实验结果表明, 高精度铂电阻测温系统的测量稳定性优于0.005 ℃/10 day, 测量分辨力优于0.005 ℃, 测量准确度为0.02 ℃(k=2), 满足超精密激光干涉测量系统提出的高精度温度测量需求。

Interfered by factors such as short and long term drifts of a constant current source and the thermal electromotive force of a wire, the measurement accuracy of conventional 4-wire Pt-resistance temperature measurement system is hard to achieve the order of 0.1℃. After analyzing the principle error of an enhanced 4-wire Pt-resistance temperature measurement method, a high precision Pt-resistance temperature measurement system was designed. By using a reference resistance with small temperature coefficient and high stability as the Pt-resistance measurement datum, the temperature measurement error caused by the long term drift of a constant current source was eliminated. At the same time, the short-term drift of the constant current source was suppressed by temperature control using a Thermoelectric Cooler(TEC). For wire thermal electromotive force, it was a great advantage to be short-term invariable. Measured under the positive and negative current conditions, the two voltages on Pt-resistance were subtracted. In this way, the effect of wire thermal electromotive force was eliminated. To realize high precision voltage measurement for Pt-resistance and reference resistance, a time-sharing voltage acquisition unit with high precision and quick step response was also designed. Experimental results show that the high precision Pt-resistance temperature measurement system can achieve the stability of 0.005 ℃/10 day, the resolution of 0.005 ℃ and the accuracy of 0.02 ℃(k=2). It meets the requirements of high accuracy temperature measurement in ultra-precision laser interferometers.