The principle of ultrasonic transducer

                                                         The principle of ultrasonic transducer

 Ultrasonic positioning technology is the bat and some invisible creatures as a defensive predators and capture prey , these organisms can launch ultrasonic people can not hear (20kHz above the mechanical wave), with the air medium, according to prey or obstacles, The time interval and intensity of the reflected echo, and determine the nature of the prey or the position of the obstacle. People according to the principle of bionics, developed a range of ultrasonic transducer for distance and nondestructive testing and a series of practical ultrasonic sensors. Ultrasonic sensor is a reversible transducer, the use of crystal piezoelectric effect and electrostrictive effect, the mechanical energy and electrical energy convert together, to achieve a variety of measurement parameters. Ultrasonic generator can be divided into two categories: one is using electrical means to produce ultrasound; one is using mechanical way to produce ultrasound. Electrical categories include piezoelectric type, magnetostriction type and electric type, etc ; mechanical categories, including  Gala flute, whistle and air whistle and so on. They produce the ultrasonic frequency, power and sound characteristics are different, so the application is also different. Commonly used is the  piezoelectric ultrasonic generator, which is the use of piezoelectric crystal resonant to work, the sensor has two piezoelectric ceramic and a resonant plate, when its poles plus pulse signal, and the frequency is equal to the natural oscillation frequency of piezoelectric . The piezoelectric chip will resonate,and  and drive the resonance plate vibrate to produce ultrasound.On the other hand, if there is no extra voltage between the two electrodes, when the resonant plate receives an ultrasonic wave, it will force the piezoelectric wafer to vibrate and convert the mechanical energy into an electrical signal, which becomes an ultrasonic receiver. Depending on the time difference between the echo and the transmitted wave or the strength of the echo, the ultrasonic sensor can obtain the distance or attribute of object .