Principle of ultrasonic transducer

1 Introduction

With the development of new technologies such as automation, the number of ultrasonic transducers is increasing, and all modern instruments and equipment are inseparable from sensors in the industrial production, especially in the production processes, various transducers are used to monitor and control various parameters of the production process, such as temperature, pressure, flow, etc., in order to make the equipment work at its best and the product is at its best quality. In the middle of the 20th century, it was found that transducer crystals of certain media (such as quartz crystal, sodium potassium tartrate crystal, PZT crystal, etc.) can generate the higher power ultrasonic waves under the action of high voltage and narrow pulse. It is different from audible sound waves, it can be used for welding of integrated circuits and cleaning inside the picture tube. In terms of detection, transducer for depth has the characteristics of refraction and reflection that is similar to light waves, and ultrasonic nano detectors can be used. it is detecting seabed shipwrecks and enemy submarines. Ultrasound has penetrated into many areas of our lives now, such as B-ultrasound, remote control, anti-theft non-destructive testing, and so on.

2. The concept of ultrasound

People can hear that the sound is generated by the vibration of the object. Its frequency is in the range of 20Hz-20kHz, which is called audible sound wave. Mechanical vibrations are below 20 Hz are inaudible to the human ear, called infrasound waves; mechanical vibrations above 20 kHz are called ultrasonic waves, and commonly used for ultrasonic, frequencies of ultrasonic echo-sounder transducer are from tens of kHz to tens of MHz. Ultrasonic waves are mechanical oscillations in the elastic media. There are two forms: lateral oscillation (transverse wave) and longitudinal oscillation (longitudinal wave). Applications used in the industry often use longitudinal oscillations. Ultrasonic waves can travel in the gases, liquids, and solids, but at different propagation rates. In addition, it also has refraction and reflection phenomena decays during propagation. The frequency of ultrasonic waves is propagating in the air is relatively low, generally it is tens of kHz, but the attenuation is faster; the frequency of propagation in the solids and liquids is higher, but the attenuation is smaller and the propagation is farther.

3. Features of ultrasound

The directivity of the mounting ultrasonic transducer is good, it is not easy to diverge, and the energy is concentrated. Therefore, the penetration power is large, and the energy loss is small after penetrating the steel plate of several meters thick. Ultrasonic waves can produce significant reflection and refraction when they encounter the interface between the two media. This phenomenon is similar to light waves. The higher of frequency is the ultrasonic transducer for flowmeter, the better is the sound field directivity, and the closer is the reflection and refraction characteristics of the light wave are. By using the characteristics of ultrasonic waves, various ultrasonic sensors can be used, and different circuits can be used to make various ultrasonic measuring instruments and devices, and are widely used in the underwater communications, medical, and home appliances.

4. Principle of ultrasonic sensor

The ultrasonic sensor is a sensor developed by utilizing the characteristics of ultrasonic waves, and is composed of a transmitting sensor, a receiving sensor, a control portion, and a power supply portion. The transmitter sensor consists of a transmitter and piezo ceramic vibrator transducer with a diameter of about 15 mm. The functions of ultrasonic flowmeter transducer is to convert the electrical vibration energy of the ceramic vibrator into super energy and radiate into the air; the receiving sensor is a piezo ceramic vibrator transducer. It is composed of an amplifying circuit, the receiving 2MHz ultrasonic sensor is to generate mechanical vibrations, converts them into electrical energy, and acts as an output of the sensor receiver to detect the transmitted ultrasonic waves. In the actual use, the piezo ceramic vibrator is used for the transmitting sensor.which can also be used as a ceramic vibrator on the receiving sensor. The part mainly controls the pulse frequency, duty cycle, sparse modulation and counting, and detection distance sent by the transmitter. power supply of ultrasonic oil level sensor can be DC12V ± 10% or 24V ± 10%.