声速测量实验英文版.pptVIP

Measurement of Speed of Sound Yabin Zhu (Director) Email: ybzhu@bjtu.edu.cn Room: 7415 Basic of Experiments Theory 1 Ultrasonic transmitting and receiving Ultrasonic pressure Voltage Piezoelectric transducer electromechanical interaction Piezoelectric effect receiving Reverse piezoelectric effect transmitting applied mechanical stress charge accumulates applied electrical field mechanical strain Physical description Standing wave resonance method Phase comparison method 2 Measurement of speed of sound Apparatus resonance frequency: about 35kHz oscilloscope Signal generator Piezoelectric transducer Auto reading metric scale Experiment Procedure Tune signal generator to give about 35 kHz sine signal; Adjust the distance between S1 and S2 reaches to 5 cm, slowly move S2 to increase the distance. Find larger amplitude of sine wave fix S2; 3) Carefully tune signal generator again, find the largest graphics amplitude on the screen write down the resonance frequency f. Stage I Find the resonance frequency f Note: the resonance frequency f is not the same for every ultrasonic velocity meter. 1?) To record the first position l1 by the metric scale. Slowly moving S2 again, when the largest amplitude of sine wave appears on the screen for the second time, write down the position l2. 3) Continuously move S2 from near to the distance, successively record all the maximum amplitude position l3, l4, …l12, which are observed on the oscilloscope screen. Stage II Standing wave resonance method to measure Note: the resonance frequency f remains unchanged during the procedure. ?1) Select X-Y mode of oscilloscope, observe Lissajous patterns. 2) Shift S2 position, start to record the position coordinate when the first slanting line is observed. ③ Continuously move S2 from near to the distance, successively record all the same slanting line position l1, l2, …l12, which are observed on the oscillos