Four factors affecting the working effect of ultrasonic transducers

Views: 3 Author: Site Editor Publish Time: 2020-06-03 Origin: Site

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Ultrasonic sensors use the vibration of the pressure vibrating ceramics on the sensor head to generate high-frequency (inaudible to human ears) sound waves for induction. If the sound waves hit a certain object and are reflected back, the sensor can receive the echo. The ultrasonic sensor can determine the distance between the 200KHz ultrasonic transducer probe and the object based on the sound wave wavelength and the time difference between transmitting and receiving echoes. In a typical application, ultrasonic sensor can have both short-distance and long-distance settings through the setting of buttons. No matter what kind of limit the object is , the ultrasonic sensor can detect it. For example: the ultrasonic sensor can be installed on a tank filled with liquid, or a box is containing small balls, and emit sound waves to the container. The length of time to receive the return wave can determine whether the container is full, empty or Is partially full.

Ultrasonic transducer distance can also be through-beam, ie independent transmitters and receivers. When it is detecting slow-moving objects, or requiring rapid response or application in a humid environment, this type of ultrasonic sensor called split or split is very suitable. Ultrasonic sensors are preferred when is detecting transparent or colored objects, liquids, smooth, rough, shiny, translucent, and other material surfaces, and irregular objects. Therefore, ultrasonic sensors are widely used in industry, national defense, biomedicine, etc.

Regarding the use rules of ultrasonic sensors, many customers often ignore the influence of some environmental factors and cause troubles for the normal use of ultrasonic sensors. They have summarized the following major factors for customer research:

Scope and size
The size of the detected object will affect the maximum effective range of the ultrasonic sensor. The ultrasonic sensor must detect a certain level of sound waves before it can be excited to output a signal. A large object can reflect most of the sound waves to the sensor, so the sensor can Sensing this object to the maximum extent, and a small object can only reflect very few sound waves, which significantly reduces the range of induction.
Test object
The most ideal object that can be detected with an ultrasonic sensor should be a large, flat, high-density object, they are placed vertically facing the sensor sensing surface. The most difficult to detect are those with very small areas, or made of materials that can absorb sound waves, such as foam plastic, or those that face the sensor at an angle. For objects that are more difficult to detect, you can teach the background surface of the object first, and then react to the object placed between the sensor and the background.

For liquid measurement, the liquid surface needs to face the ultrasonic sensor vertically. If the surface of the liquid is very uneven and fluctuates greatly, the response time (St) of the ultrasonic sensor should be adjusted longer. It will average these changes. , You can minimize the impact of very uneven and large fluctuations on the measurement results.

3. Vibration
Whether it is the ultrasonic sensor itself or the vibration of the surrounding machinery, it will affect the accuracy of the distance measurement. At this time, some damping measures can be considered. For example: using a rubber anti-vibration device to make a base for the ultrasonic sensor can reduce the vibration, and can also use a fixed rod eliminate or minimize vibration. When the ambient temperature changes slowly, the ultrasonic sensor with temperature compensation can make adjustments, but if the temperature changes too fast, the sensor will not be able to make adjustments.

4. Misjudgment
Sound waves may be reflected by nearby objects, such as guide rails or fixed fixtures. To ensure the reliability of detection, the influence of surrounding objects on sound wave reflection must be reduced or eliminated. In order to avoid false detection of surrounding objects, many ultrasonic sensors have a The LED indicator is used to guide the operator to install, to ensure that the sensor is installed correctly, reducing the risk of errors.

The ultrasonic sensor emits high-frequency sound pulses that cannot be heard by the human ear, and measures the time difference between when the signal is transmitted back to the object. The rugged ultrasonic sensor has successfully demonstrated its superior performance in various occasions, especially the measurement or detection of non-contact objects. This can also be used in very harsh working environments. The most impressive performance is that it can accurately detect substances of various materials and colors (not affected by materials and colors).

The detection range of the custom ultrasonic transducer depends on the wavelength and frequency used. The longer the wavelength, the lower the frequency, the greater the detection distance. For example, the detection range of a ultrasonic sensor with a millimeter-level wavelength is 300~500mm. The detection range of ultrasonic sensor with a wavelength greater than 5mm can reach 8m. Some ultrasonic sensors have a narrow 6ordm; acoustic emission angle, which is more suitable for accurately detecting relatively small objects. Other ultrasonic sensors with an acoustic wave emission angle of 12 to 15 mm,which can detect objects with large inclination angles. In addition, we also have an external probe-type ultrasonic sensor, and they are corresponding with electronic circuit is located in the conventional sensor housing. This structure is more suitable for detecting occasions with limited installation space.