The automatic feed line sensor for pigs is mainly used for quantitative feeding, feed sensing and quantitative start-stop In particular, although the sensor is small, it can affect the normal operation of the whole material line. Once the sensor is insensitive and fails to start and stop at the quantitative position, the feed line will continue to run and feed, which will overload the whole feed line and cause the main engine to burn out. According to many years' experience in pig farm feed line construction, two kinds of sensors suitable for feed line are recommended: Israel imported five-wire sensor and Derfl two-wire sensor. It is recommended not to buy tens of dollars cheap because of small losses. Once something goes wrong, the loss outweighs the gain.