超声波发射器向某一方向发射超声波，在发射时刻的同时开始计时，超声波在空气中传播，途中碰到障碍物就立即返回来，超声波接收器收到反射波就立即停止计时。超声波在空气中的传播速度为340m/s，根据计时器记录的时间t，就可以计算出发射点距障碍物的距离(s)，即：s=340t/2 。这就是所谓的时间差测距法。 -Ultrasonic transmitter to the ultrasonic transmitter in one direction, while the launch time of start time, ultrasonic propagation in the air, on the way to return immediately encountered obstacles, the ultrasonic reflected wave received by the receiver to immediately stop the clock. Ultrasonic propagation velocity in air is 340m/s, according to the timer records the time t, we can calculate the emission from the pitch obstacle (s), ie: s = 340t/2. This is called time difference ranging method.