Abstract
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 resist-ance,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℃/10day,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.
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