摘要：超聲波是一種機械波，其振動頻率在20kHz~106 kHz,超出人耳所能覺察的范圍，因此也稱為不可聞聲波。因為其具有較好的方向性，沿著介質傳播時所攜帶的能量大，傳播時衰減較弱，穿透能力強，所以被廣泛應用于工業，農業，醫學，化工，能源等許多領域。

　　　液位檢測的需求遍布生產生活的各個方面，特別是在工業生產的過程中的液位檢測需要滿足精度高，靈敏度高，能適應復雜的生產環境，操作簡單且易于維護等要求。

　　　本次設計的液位檢測控制系統是超聲波技術在單片機平臺的上的應用實現。液位的檢測方法有很多種，采用超聲波方法來檢測是因為其測量的方式是非接觸式測量，適應大部分液體的測量。且其測量時間短，精度高，可以滿足實時檢測的要求。本次設計是利用超聲波傳感器，采用回波法，即利用超聲波發生裝置產脈沖信號，當超聲波遇到液體時產生回波，通過檢測接收到回波的時間間隔計算出超聲波所傳播的距離，從而達到液位檢測的目的。而單片機作為控制芯片，通過超聲波傳感器實現液位數據的實時采集，控制直流電機水泵的PWM達到調節液體流量的大小目的，并通過串口通訊的方式實現和上位機通訊。

關鍵字：超聲波  液位檢測  單片機  PWM

ABSTRACT：Ultrasound is a mechanical wave which vibration frequency in the 20 kHz to 106 kHz. It is also called non-audible sound wave because it beyond the range of the human ear can perceive. Ultrasound has good directivity, propagation attenuation is weak, strong penetrating power. It carried more energy than other waves, Ultrasound is widely used in industry, agriculture, medicine, chemical industry, energy and many other fields.

　　　Demand for liquid level detection throughout all aspects of production and living. Especially in the industrial production process, Liquid level detection need to meet the high precision, high sensitivity, able to adapt to the complexity production environment, simple operation and easy maintenance requirements.

　　　The design of the liquid level detection and control system is the ultrasonic technology application implementation in single-chip platform. There are a variety of liquid level detection methods, employment ultrasonic methods, because the measurement is non-contact measurement. It adapt to the measurement of most of the liquid. The measurement time is short, high precision to meet the requirements of real-time detection. This design is the use of ultrasonic sensors, using the echo method, use the ultrasonic wave generating means producing a pulse signal, generating an echo when the ultrasonic encountered liquid, through the detection of the received echo time, we can calculated ultrasonic transmission distance so as to achieve the purpose of the liquid level detection. System used the Micro-controller as a control chip, through the ultrasonic sensors to achieve real-time data acquisition, control PWM of the DC motor to adjust the liquid flow, and PC communication.

Keywords: ultrasonic wave; Liquid level detection; MCU; PWM