The objects shake, which lets people listen, whose frequency is between 20HZ and 20KHZ. Ultrasonic wave is more than 20KHZ, infrasonic wave is less than 20HZ. The normal ultrasonic wave frequency is between tens of KHZ and tens of MHZ.
Ultrasonic is a mechanical oscillation in an elastic medium. There are two ways: Lateral oscillation
(share wave) and longitudinal oscillation(Longitudinal wave ). Ultrasonic can transfer in gaseous, liquid and solid, and their speed is different. In addition, it also has refractive and reflection phenomena, and there is attenuation in the propagation process.When the ultrasound is transmitted through the air, its frequency is low, normally tens of KHZ, while when it is transmitted through the solid and the liquid, its frequency is high. It decays fast in the air, while in the liquid and the solid, it decays slowly and transfers far. Using the feature of ultrasonic, people produce many kinds of ultrasonic sensor and make various ultrasonic measuring instruments and devices with different circuits. It is also normally used in many aspects, such as communication and medical.
The main materials of ultrasonic sensor level measurement
is piezoelectric crystal (electrostriction) and nickel-iron alloys (magnetostrictive). The materials of the electrostriction mainly is PZT and so on. The ultrasonic sensor level measurement of the piezoelectric crystal is an invertible sensor, it can transfer the electricity into mechanical oscillation to produce ultrasonic. At the same time, it also turns into electricity when it receives an ultrasound, so it can be divided into transmitters or receivers. Some of the ultrasonic sensor level measurement can either send or receive. Just take small ultrasonic sensor level measurement to introduce. There are slight differences between send transmission and reception. It is suitable to transmit in the air, whose frequency for work is normally 23-25 KHZ or 40-45 KHZ. This kind of sensor is suitable for ranging, remote control and anti-theft. This kind has T/R-40-60, T/R-40-12 and so on(T: transmit, R: receive, 40: frequency, 60,12: outer diameter,;In millimeters). There is also a sealed ultrasonic sensor level measurement
(MA40EI). It is characterized by waterproofing(but it can not put in water), Its performance is good, which can be used as material position and proximity switch. There are three basic types of ultrasonic application: transmission type is used for remote control, burglar alarm, automatic door, proximity switch, etc; the separated reflection type is used for ranging, liquid level or material position; the reflection type is used for material flaw detection and thickness measurement and so on.
It consists of a sensor-transmitter (or a wave transmitter), a receiving sensor (or a wave receiver), a control part, and a power supply.The transmitter sensor consists of a transmitter and a ceramic oscillator transducer, and the using diameter of the ceramic oscillator transducer is 15mm. The function of the transducer is to convert the vibrational energy of the ceramic vibrator into superenergy producing airborne radiation. Besides, the receiving sensor consists of a ceramic oscillator transducer and a amplifier circuit. Transducer receiving wave generates mechanical vibration, which produces electronic power. The power is the output of the sensor receiver, so it will check the ultrasonic in dispatching. In practice, a ceramic vibrator used as a transmitter sensor can also be used as a receiver sensor. The control part mainly controls the pulse chain frequency, the space ratio, the sparse modulation, counting and detection distance of the transmitter.