一个基于AT89C51单片机设计的温湿度计，应用了SHT11温湿度传感器，除了最简单的温湿度测量，电路还可以通过按键设置温湿度阈值，并添加了超声波雾化器，当湿度超过阈值时，超声波雾化器工作，自动加湿环境。-One based on AT89C51 microcontroller design hygrometer, temperature and humidity sensors SHT11 applied, but the simplest humidity measurement circu

选用MQ2气体传感器对现场可燃性气体浓度进行检测，采用功能和性价比较高的STC89C52单片机作为中央处理单元，对浓度信号进行采集、数据处理、显示、报警及打开排气装置等工作。-Using mq2 gas sensor for the concentration of flammable gas field were detected by function and high ratio of performance to price STC89C52 microcontroller as the

51单片机接入差分信号重量传感器，设定额重，输出控制，同时DA转换（AD421芯片）输出4-20mA。-51 single access differential signal of the weight sensor, set the amount of weight, output control, while the DA converter (AD421 chip) output 4-20mA.