基于STM32的温湿度变送器设计

Design of Temperature and Humidity Transmitter Based on STM32

摘要:

针对目前常见的电流型温湿度变送器恒流输出特性较差、精度较低、校准繁琐的不足,给出了一种基于STM32单片机的温湿度变送器设计方案;该电路以STM32单片机为控制核心,以SHT11数字式温湿度传感器采集环境温湿度;通过STM32的内部12位D/A输出模块将温湿度转换为模拟电压信号;随后,该电压信号通过V/I转换电路变为4～20 mA的模拟电流信号;研究了常见V/I转换电路的原理并提出改进电路方案;最后,基于STM32的内部FLASH存储功能给出了一种上位机软件校准方案;通过对比仿真和实验表明,该变送器具有成本较低、恒流特性较好、精度较高、校准快捷方便的优点,能够满足工农业生产中常规温湿度测量的要求。

Abstract:

Today’s common current-output temperature and humidity transmitters have some deficiencies such as poor characteristic of constant current output,low accuracy and cumbersome calibration. This paper presents a design of the transmitter based on STM32 microcontroller in order to make up for the deficiencies. With the STM32 as the core controller,the circuit gains the temperature and humidity signals by SHT11 digital sensor. The signals are converted to analog voltage signals via the internal 12-bit D/A module of STM32 microcontroller. After which,the voltage signals become 4 ~ 20 mA analog current signals through the V/I converter circuit. This paper studies the principle of the V/I converter circuit and then optimizes the circuit. At last,this paper presents a calibration scheme based on PC software. The simulation and experimental results show that the transmitter has advantages such as good constant current characteristic,high precision,easy and fast calibration. These superiorities of the transmitter meet the requests of conventional temperature and humidity measurement in industrial and agricultural production.