Development a kind of auto raindrop detecting set base on AT89C52

The ultrasonic detector (5P14) gives off an ultrasonic wave when it is given an electronic pulse. This ultrasonic wave is rejected at the interface of two kinds of media. The ultrasonic detector receives this wave and converts it into electronic pulse. The time between the send pulse and the back pulse can be captured using the capture function of the MCU AT89C52. The temperature can be got by the digital temperature sensor DS1820. Use the temperature, the speed of ultrasonic can be calculated accurately and the height of liquid can be measured accurately. The absolute error of measure is limited within 0.1mm when the precipitation rain fall is less than 10mm and the relative error is limited within 0.5% when the precipitation rain fall is more than 10mm.