What Is Ultrasonic Sensor?
An ultrasonic sensor is a device that measures the distance from the sensor to an object through the air without physical contact. It calculates the distance by emitting high-frequency sound waves (also called ultrasonic sound waves) at the measured object - receiving the reflected sound waves and calculating the distance from the sensor. The time between the transmission from the transmitting source and the return from the receiving source, then the distance is measured.
Ultrasonic sensor is an important branch of sensor products and occupies a large proportion in the sensor industry. Ultrasonic sensor has many advantages such as high precision, high sensitivity, strong adaptability and low cost, making it the best choice for short-distance sensing conditions. select. With the continuous upgrading of products and the continuous growth of downstream industries, the future development prospects of the ultrasonic sensor industry are very broad.
There are many types of ultrasonic sensors. According to the detection mode, they can be divided into two types: integrated transceiver type and split transceiver type. According to the structure, they can be divided into three types: high-frequency type, open type and waterproof type. According to the material, they can be divided into piezoelectric type ( Electrostrictive type) and magnetostrictive type, according to the use environment can also be divided into ultrasonic sensors in gas and ultrasonic sensors in liquid.
Piezoelectric (Electrostrictive) Ultrasonic Sensors:
Piezoelectric ultrasonic sensor is an ultrasonic sensor that uses the piezoelectric effect principle of piezoelectric materials to work. The commonly used sensitive components are mainly piezoelectric crystals and piezoelectric ceramics. According to the difference of positive and inverse piezoelectric effects, piezoelectric ultrasonic sensors are divided into two types: generator (transmitting probe) and receiver (receiving probe). , Lamb wave probes, variable angle probes, dual crystal probes, focusing probes, water immersion probes, water spray probes and special probes, etc.
Piezoelectric ultrasonic generators use the principle of inverse piezoelectric effect to convert high-frequency electrical vibrations into high-frequency mechanical vibrations to generate ultrasonic waves. When the frequency of the applied alternating voltage is equal to the natural frequency of the piezoelectric material, resonance will occur, and the ultrasonic wave generated at this time is the strongest. Piezoelectric ultrasonic sensors can generate high-frequency ultrasonic waves ranging from tens of kilohertz to tens of megahertz, and their sound intensity can reach tens of watts per square centimeter. Piezoelectric ultrasonic receivers work on the principle of positive piezoelectric effect. When the ultrasonic wave acts on the piezoelectric wafer to cause the wafer to expand and contract, charges of opposite polarities are generated on the two surfaces of the wafer. These charges are converted into voltages, amplified and sent to the measuring circuit, and finally recorded or displayed. The structure of the piezoelectric ultrasonic receiver is basically the same as that of the ultrasonic generator, and sometimes the same sensor is used as both the generator and the receiver.
Magnetostrictive Ultrasonic Sensor:
The phenomenon that ferromagnetic materials stretch and contract along the direction of the magnetic field in an alternating magnetic field is called the magnetostrictive effect. The strength of the magnetostrictive effect, that is, the degree of material elongation and shortening, varies with different ferromagnetic materials. The magnetostrictive effect of nickel is the largest. If a certain DC magnetic field is applied first, and then an alternating current is applied, it can work in the region with the best characteristics. In addition to nickel, the materials of magnetostrictive sensor include iron diamond vanadium alloy and ferrite containing zinc and nickel. They operate in a narrow range of efficiency, within a few tens of kilohertz, but with powers up to 100,000 watts, sound levels up to several kilowatts per square millimeter, and high temperature tolerance.
The magnetostrictive ultrasonic generator is to place the ferromagnetic material in an alternating magnetic field, so that it produces an alternating change in mechanical size, that is, mechanical vibration, thereby generating ultrasonic waves. It is made by stacking several nickel sheets with a thickness of 0.1-0.4mm, and the sheets are insulated to reduce eddy current loss. The principle of the magnetostrictive ultrasonic receiver is that when the ultrasonic wave acts on the magnetostrictive material, it causes the material to expand and contract, thereby causing its internal magnetic field (that is, the magnetic permeability) to change. According to electromagnetic induction, the induced electromotive force is obtained in the coil wound on the magnetostrictive material. This potential is sent to the measuring circuit and finally recorded or displayed.
Ultrasonic sensors have the advantage of being widely used and versatile. In terms of application fields, it can be used for water level detection, drone applications, automatic obstacle avoidance applications, distance detection applications, etc.; in terms of test types, there are non-contact detection, level detection, position detection, distance detection, etc. It can meet most of the detection requirements. At the same time, ultrasonic sensors have a wide range of applications in condition monitoring and predictive maintenance, including boilers, compressors, heat exchangers, steam traps, valves and other components. They can minimize production downtime, improve troubleshooting capabilities, enhance quality control and safety, and provide significant economic benefits.
The main advantage of ultrasonic sensors is their strong resistance to environmental interference, that is, they can be used in any lighting environment, and are reliable under various light conditions such as indoor or outdoor, complex ambient light, etc. Non-contact detection can be carried out. So for some applications ultrasonic sensors are better than infrared sensors because they are not affected by soot or black matter. At the same time, ultrasonic sensors can detect transparent objects, including echoes reflected from glass and liquid surfaces, and are resistant to fog, dust and dirt particles, and can stably detect objects with complex shapes, such as grid trays, springs, etc.
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