Development of high-precision temperature measurement system based on ARM

Abstract

The high-precision temperature measurement system which adopts ARM processor LM3S1138 as controlling core was introduced in this paper. In the temperature measuring circuits, the current driving circuit of sensor Pt100A and A/D converting circuit adopt the same reference voltage, which makes A/D conversion results are only dependent on the changing value of platinum resistance with the temperature change DeltaR <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> , and will not be affected by the stability of sensor constant current drive current and the reference voltage accuracy of A/D converter, the design method has improved the sampling accuracy of the system hardware effectively. In the software calibration of measurement error, least squares method was used to fit the ldquosampling value - temperaturerdquo curve in connection with the measured data of various temperature sections, it offsets the deviation which occurred in various intermediate links of the signal from platinum resistance to the A/D conversion in the temperature measurement of Pt100A. In the temperature measurement process, ARM processor do real-time computing to get final temperature measurement results according to the A/D sample value and combined with the polynomial of sub-fitting actual measurement results show that, the system temperature deviation is less than 0.05degC.