基于HX710A的温度测量电路设计及误差分析

Design and Error Analysis of Temperature Measurement Circuit Based on HX710A

电桥法或者恒流源法PT100温度测量时只能输出毫伏级信号,为解决因信号幅度过小需经放大后才能AD采样的问题,采用24位A/D电子称重专用芯片HX710A直接测量毫伏级信号,针对HX710A的±20 mV采样范围设计了两线制PT100的惠斯通电桥电路,测量电阻结果采用查表法转换为温度,经过零点标校后,在-20℃~100℃温度范围内利用恒温槽对PT100进行测量,温度测量分辨率0.0003℃,实测误差不超过±0.1℃;用标准电阻模拟测量,输出信号不超过±18 mV范围,不经过放大,HX710A直接采样并计算出电阻值,查表后转化为温度,温度范围扩展到-200℃~600℃,测量误差不超过±0.1℃。

Measuring temperature with bridge or constant-current-source method,the output signal of PT100 is millivolt signal.In order to solve the problem that the signal amplitude is too small and it needs to be amplified before AD sampling.A special HX710A for 24 bit A/D electronic weighing is used to directly measure the millivolt level signal.The Wheatstone bridge circuit of two-wire PT100 is designed for the±20 mV sampling range of HX710A.The measurement result of resistance are converted into temperature by look-up table after zero point calibration,PT100 is measured by thermostat bath in the temperature range of-20℃~100℃,the resolution of temperature measurement is 0.00003℃,and the measured error is not more than±0.1℃;the output signal is not more than±18 mV without amplification.The resistance value is directly measured by HX710A without amplification,and is converted into temperature after look-up table.The temperature range is extended to-200℃~600℃,and the measurement error is not more than±0.1℃.