小麦播种机电容式排种量传感器设计

为提高小麦播种机排种量检测的可靠性，根据电容器的电容随极板间介质质量变化而发生变化的原理，研制了一种电容式排种量传感器。利用AD7745数字转换器和单片机搭建微电容信号调理电路，电容传感器与调理电路采用短线连接，减小了寄生电容对测量精度的影响。通过标定，获得了传感器电容值与排种量的关系模型。在播种机试验台架上对电容式排种量传感器性能进行了测试。试验结果表明，在排种速度不同的情况下，该传感器的最大测量误差为2.2%。该传感器能够较好地实现小麦播种机排种量的在线检测，为变量播种提供了有力支持。

Design of capacitance seed rate sensor of wheat planter

To improve the measurement reliability of the seed rate on wheet planter, a capacitance seed rate sensor was developed according to the principle of capacitance variation of medium mass. The signal condition circuit as designed with AD7745 convert and a single chip microcomputer, and short line connection betweent the sensor and conditon circuit was used to decrease the stray capacitance of the sensor. The founction relationship between the sensor capacitance and seed rate was obtained according to the calibration. The results showed that the maximum error of the sensor was 2.2% in different seeding rate. The sensor can test the seed rate well on line and provide strong support for variable seeding.