摘要：超声波是一种机械波，其振动频率在20kHz~106 kHz,超出人耳所能觉察的范围，因此也称为不可闻声波。因为其具有较好的方向性，沿着介质传播时所携带的能量大，传播时衰减较弱，穿透能力强，所以被广泛应用于工业，农业，医学，化工，能源等许多领域。

　　　液位检测的需求遍布生产生活的各个方面，特别是在工业生产的过程中的液位检测需要满足精度高，灵敏度高，能适应复杂的生产环境，操作简单且易于维护等要求。

　　　本次设计的液位检测控制系统是超声波技术在单片机平台的上的应用实现。液位的检测方法有很多种，采用超声波方法来检测是因为其测量的方式是非接触式测量，适应大部分液体的测量。且其测量时间短，精度高，可以满足实时检测的要求。本次设计是利用超声波传感器，采用回波法，即利用超声波发生装置产脉冲信号，当超声波遇到液体时产生回波，通过检测接收到回波的时间间隔计算出超声波所传播的距离，从而达到液位检测的目的。而单片机作为控制芯片，通过超声波传感器实现液位数据的实时采集，控制直流电机水泵的PWM达到调节液体流量的大小目的，并通过串口通讯的方式实现和上位机通讯。

关键字：超声波  液位检测  单片机  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