[Doppler Effect Comprehensive Experimental Device] Functions and Functions:
The Doppler effect comprehensive experimental device is a comprehensive experimental device and experimental method involving the quantitative measurement of the speed of sound and the movement speed of objects and the verification of the Doppler effect.
Doppler effect is an important content of university physics. At present, there are many teaching demonstration instruments for Doppler effect, but there are few instruments used for experiments, and there are also many deficiencies that cannot be accurately measured.
The Doppler effect comprehensive experiment device provides an experimental device that is applied to teaching, is reliable for students, and has strong operability, physical quantity display is simple, and different experimental parameters can be changed according to experimental principles. The experiments that can be done on this device are rich in content, such as in the case of different signal source frequencies, different car motion speeds, different car motion directions, and the exchange of sound sources and receiver positions. Both the source and receiver can be measured under non-relative motion conditions, not only to verify the Doppler effect theoretical formula but also to calculate the speed of sound and the moving object and to establish the equation of motion of the object.
The Doppler effect integrated experimental device is divided into three parts: host, signal generation controller, signal acquisition and processing.
The host is composed of speed controller, track, stepper motor, belt pulley, belt, trolley, photoelectric door, sound source, signal receiver and frame. The car is fixed on the belt, the stepper motor on the frame drives the belt pulley, the two cars The wheel is on the track, the speed controller of the motor speed is on one side of the frame, the light block is installed on the side of the car, and the sound source or audio signal receiver is fixedly installed on the end of the machine frame or on the small car. The machine frame is equipped with a speed measurement and control car. Stopped photoelectric door.
The signal generation controller is a frequency signal generator with adjustable signal frequency and amplitude, and a speed display, frequency display, trolley motion control, and reset function. The instrument panel has frequency and amplitude adjustment knobs, digital display frequency. Values ​​and the duration of the light barrier through the photogate, the back of the instrument has a frequency output interface, a photoelectric gate interface and an oscilloscope interface, and a control interface.
Signal acquisition processing consists of audio signal receiver, computer audio input and spectrum analysis software.
Signal acquisition can also be recorded via a mini MP3 recorder. Place the recorder in the box on the car or on the end of the stand. The recording port is opposite to the sound source and acts as an audio signal receiver.
There are three photoelectric doors on the machine base, and the middle one is the speed-measuring photoelectric door. On both sides, the photoelectric door is controlled to stop the car.
The position of the speedometer photoelectric door can be moved and changed. The car automatically stops through the photoelectric doors at both ends of the track. The sound source and receiver mounting positions are interchangeable according to the experimental content.
The signal frequency of the audio signal generator ranges from 10 KHz to 20 KHz.
The Doppler effect integrated experimental device measurement method is:
Press the control button After the stepper motor is turned on, the trolley starts. The motor rotates to drive the pulley to make the trolley move on the track of the seat. The speed of the motor is adjusted by the speed control knob of the speed controller to change the speed of the trolley to achieve the continuous speed of the trolley. Tuning and optional trolleys for uniform or variable speed movements; speed photoelectric door through the light barrier through the photogate time, measuring the time elapsed by the car to calculate the car speed, the position of the photoelectric door can be moved and changed, the time value in the signal control The display window of the device is displayed; the frequency of the audio signal generator is adjusted by the frequency adjustment button of the signal generation controller, and the amplitude is adjusted by the amplitude adjustment knob; the frequency value is displayed on the digital display window of the panel; the audio signal receiver of the signal acquisition will The sound signal received by the sound source is connected to the computer's audio input through a wire, the computer saves it as a file, and the frequency spectrum analysis software performs spectrum analysis and numerical processing on the signal of the stationary part and the moving part of the sound file respectively.
The Doppler effect integrated experimental device can achieve the following functions:
1, the car speed adjustable.
2, the direction of movement of the car can be changed.
3, the car can be used for uniform or variable speed sports.
4. The position of sound source and receiving head can be interchanged.
5, the relative movement of the sound source and receiver, the sound source and the receiver for non-relative motion.
6. The output frequency range of the audio signal generator is from 10KHz to 20KHz, no noise is generated and the size is adjustable.
7, adjustable speed photoelectric door position.
8. The received audio signal is directly input by the microphone into the computer or recorded and saved by the mini MP3 recorder.
9, through the spectrum software, analysis and determination of the car at rest and exercise frequency, verify the Doppler effect and calculate the corresponding physical quantity.
The Doppler effect comprehensive experiment instrument has the following advantages:
Stepping motor belt pulley structure ensures the experimental verification conditions of the uniform motion of the object. At the same time, it can also realize the variable speed motion of the object. The Doppler effect is used to measure the speed of the car at any moment and the motion equation of the car is obtained.
The experimental device does not need a special computer interface. It only needs to record and save the sound file through the audio input port of the computer, which reduces the cost. Through the spectrum analysis software, the recorded audio signal can be analyzed to obtain the frequency of the signal received in the stationary and moving state of the object.
The experimental device can do a lot of experiments, in the case of different signal source frequencies, different car movement speeds, different car movement directions, the exchange of sound sources and receiver positions, and sound sources. The receiver can be measured under the condition of non-relative motion, verify the theoretical formula or calculate the speed of sound and moving objects and establish the equation of motion of the object.
The experimental data can be analyzed and processed online or saved after being processed. It is very flexible and convenient. The instrument also has an oscilloscope interface, and the signal can also be displayed on the oscilloscope.
The Doppler effect comprehensive experimental device can not only study the Doppler effect phenomenon of acoustic waves and verify the Doppler effect formula in university physics experiment teaching, but also use spectrum analysis in the data processing of signals to expand students’ knowledge. , And improve the quality of physics experiment teaching.
Title: Doppler Effect Comprehensive Experimental Device
Completed Unit: Zhejiang University Physics Experiment Teaching Center