基于4~20 mA输出的温湿度传感器设计

Design of temperature and humidity sensor based on 4-20 mA output

基于工业现场温湿度信号的测量,为解决温湿度传感器测量信号远距离传输时受噪声干扰、线路阻抗等的影响,利用4~20 mA电流环的抗干扰特性,采用电流进行信号传输,使电路的传输性能大大提高。设计采用SHT15作为测温、测湿的敏感元件,利用C8051F410单片机的IDAC功能,将测得的温湿度数字量转化成模拟量。再经过适当调理转换电路,并通过软件程序设计改善测量信号的线性度,实现4~20 mA的电流输出。最后利用标准温湿度测量设备进行测试试验分析,验证温湿度传感器的4~20 mA电路可以实现高精度的温湿度测量。

Based on measurement of temperature and hunimity signal in industrial fields,the anti⁃inter⁃ference charateristics of 4-20 mA current loop are utilized to solve the influence of noise interference and line impedance on the long⁃distance transmission of temperature and humidity sensor’s measurement signal.Using current for signal transmission greatly improves the transmission performance of circuits.SHT15 is used as the sensitive element for temperature and humidity measurement,the digital quantity of temperature and humidity measured is converted into analog quantity by the IDAC of C8051F410.Through an appropriate conditioning and swithching circuit,the linearity of measurement signal is improved through software programming to achieve 4-20 mA current output.The standard temperature and humidity measurement equipments are used for testing and analysising to verify that 4-20 mA circuit of the te mperature and humidity measurement.