Abstract: A kind of experimental instrument for the Doppler effect based on a multiplier is introduced. The output signal of ultrasonic receiver is processed to keep the amplitude constant before connecting to the multiplier, and the inspiriting signal of the emitter is used as a conference signal of the multiplier. The output of the multiplier passed through a low-pass filter then the Doppler frequency shift can be obtained and the speed of the receiver is calculated. The structure of this instrument is simple and the physical phenomenon of Doppler effect is easy to be observed. So it is suitable to be used in the physical experiments.

Key words: Doppler effect, multiplier, speed measurement