If you would like to look at both the AC and DC components of a waveform or are only interested in the DC component use DC coupling. It is also necessary to set the timebase speed on the oscilloscope. The light is sensed by a Light Dependent Resistor LDR which changes its resistance accordingly.
Make the proper adjustments on the probe so that the corners of the square wave are square.
In this case we have. The oscilloscope is set up so that it triggers when the first microphone detects a sound and the time base is adjusted so that the sound arriving at both microphones can be seen on the screen. The difference between these two values is 008 µs which is the time taken for the. The TOF is read with a digital oscilloscope connected to two fast sensors detecting the signals at the switch-on of a laser diode and at the arrival of the light pulse reflected from a plane.