Select ultrasonic sensor, first of all, read the instructions or use of the sensor, different ultrasonic sensor output frequency or signal type is different! Industrial output is now a bunch of beam pulse signal, which contains the modulated signal information, hire, cut in addition to the role of the cut has encryption or other signal isolation or interference with the use of modulation Signal contains data bits and other work information. All that does not mean that there is no waveform or waveform discontinuity to judge whether the sensor is good or bad. You can use the headset after the signal output will be divided by the frequency of the signal will be heard, if there is no problem that ultrasonic emission.
The above said is working in the switch or pulse state ultrasound, generally used for positioning purposes, there is a similar radar used to measure the speed of the work to take the line, the output of analog signals, the general frequency directly determine the value, because of Not anti-interference with less.