In order to precisely measure the volume fraction of methane to avoid explosion accident' s occurrence, a signal conditioning circuit for a thermal conductivity sensor is designed based on the thermal conductivity sensor TCS208F,instrumentation amplifier INA122,U/I transmitter AD694. The weak voltage signal obtained by sensor is amplified, converts into 4～20 mA industrial standard electric current signal which suites for long-distance transmission after the U/I transformation. Electric current signal is converted back to voltage signal,and sends it into the monolithic integrated circuit. Aimed at question appeared in the circuit design process, the analysis is carried on to circuit design' s disturbance factor,a series of anti-jamming measure is obtaind,and the good effect is obtained.%为了准确测量下水道内甲烷气体的体积分数,以避免爆炸事故的发生,基于热导传感器TCS208F,仪表放大器INAl22,U/I变换芯片AD694等设计了热导传感器信号调理电路,将传感器得到的微弱电压信号放大,经过U/I变换将电压信号转换成适合于远距离传输的4～20 mA的工业标准电流信号,再将电流信号还原成电压信号送入单片机进行采集.针对调理电路设计过程中出现的问题,对电路设计中的干扰因素进行分析,得出一系列抗干扰措施的方法,在实际应用中得到了较好的效果.
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