In life, we can hear that the sound is generated by the vibration of the object. Its frequency is in the range of 20HZ-20KHZ. The ultrasonic wave is more than 20KHZ, and the subsonic wave is lower than 20HZ. Commonly used ultrasonic frequencies are between tens of KHZ and tens of MHZ.
Ultrasonic is a mechanical oscillation in an elastic medium. There are two forms: lateral oscillation (transverse wave) and longitudinal and oscillation (longitudinal wave). In industrial applications, longitudinal oscillations are mainly used. Ultrasonic waves can travel in gases, liquids, and solids at different propagation speeds. In addition, it also has refraction and reflection phenomena and decays during propagation. Ultrasonic waves are transmitted in the air at a low frequency, generally tens of KHZ, while frequencies are higher in solids and liquids. It decays faster in the air and propagates in liquids and solids with less attenuation and longer propagation. Utilizing the characteristics of ultrasonic waves, it can be made into various ultrasonic sensors, equipped with different circuits, and made into various ultrasonic measuring instruments and devices, and is widely used in communication, medical appliances and the like.
The main materials of the ultrasonic sensor are piezoelectric crystal (electrostrictive) and nickel-iron aluminum alloy (magnetostrictive). The electrostrictive material is lead zirconate titanate (PZT) or the like. An ultrasonic sensor composed of a piezoelectric crystal is a reversible sensor that converts electrical energy into mechanical oscillation to generate ultrasonic waves, and when it receives ultrasonic waves, it can also be converted into electrical energy, so it can be divided into a transmitter or a receiver. Some ultrasonic sensors are used for both transmission and reception. Only small ultrasonic sensors are introduced here. The transmission and reception are slightly different. It is suitable for propagation in air. The working frequency is generally 23-25KHZ and 40-45KHZ. These sensors are suitable for ranging, remote control, anti-theft and other purposes. This species has T/R-40-60, T/R-40-12 and the like. There is also a sealed ultrasonic sensor (MA40EI type), which is characterized by its waterproof function (but not in water), which can be used as a material level and proximity switch, and its performance is better. There are three basic types of ultrasonic applications, such as remote control, anti-theft alarm, automatic door, proximity switch, etc.; separate reflection type for distance measurement, liquid level or material level; reflective type for material flaw detection, thickness measurement, etc. .
a. Liquid level indication and controller Because the ultrasonic wave has a certain attenuation in the air, the signal sent to the liquid surface and reflected back from the liquid surface is related to the liquid level. The higher the liquid level position, the larger the signal; the more the liquid level When low, the signal is small. The received signal is amplified by BG1 and BG2, and rectified into DC voltage by D1 and D2. When the voltage on 4.7KΩ exceeds the turn-on voltage of BG3, a current flows through BG3, and the ammeter indicates that the current is related to the liquid level. Point A is connected to point A in the above figure. When the liquid level is lower than the set value, the comparator output is low. BG does not conduct. If the liquid level rises to the specified position, the comparator flips and outputs a high level. BG is turned on, J is sucked, and the infusion switch can be turned off by a solenoid valve to achieve the purpose of control (high position control).
b. Remote control switch The ultrasonic remote control switch can control household appliances and lighting. Small ultrasonic sensor (Φ12-Φ16), working frequency is 40KHZ, remote control distance is about 10 meters. Remote control transmission, this is an oscillator composed of 555 time base circuit, adjust 10KΩ potentiometer, make the oscillation frequency 40KHZ, sensor Connected to the 3rd foot, when the button is pressed, the ultrasonic wave is sent out and the circuit is received. The power supply is stepped down by 220V, rectified, filtered, and regulated to obtain a 12V operating voltage. Since it is a non-isolated power supply, the entire circuit should be packaged in a plastic case to prevent electric shock (also pay attention when debugging). The signal is received by the ultrasonic receiver and amplified by Q1 and Q2 (the L and C resonant tanks are tuned at 40 kHz). The amplified signal triggers a bistable circuit composed of Q3 and Q4, and Q5 and LED are used as trigger isolation, and can be illuminated. Since the bistable state is random at startup, a clear button is added. The trigger signal of the Q5 output turns on the triac and the load is turned on. To load an open circuit, press the send button once.
Digital Infrared Thermometer,Non Contact Infrared Thermometer,Non Contact Medical Thermometer,No Contact Infrared Thermometer
Ningbo Autrends Prevention Products Co., Ltd , https://www.autrendsafety.com