Directivity of Ultrasonic Transducers

In order to meet the various requirements of different industries, ultrasonic transducers often need to be considered from the material, shape and structural composition of the transducer. In addition, under the needs of detection conditions, objects and environments, there are corresponding special requirements for small ultrasonic transducers, such as being used in high temperature and low temperature environments, underwater detection and so on. In general, the ultrasonic transducers used are required to have sharp directivity, just like using a concentrating flashlight for illumination, which is conducive to concentrating the transmitted energy, obtaining a higher signal-to-noise ratio when receiving, and is also conducive to the detection of Target positioning assessment.


1. Directivity characteristics of ultrasonic transducers


The directivity of an medical ultrasonic transducer is related to the size, structure, operating frequency and sound transmission medium characteristics of its radiating surface. Usually, the directivity factor can be used to reflect the directivity of an ultrasonic transducer. For transmitting ultrasonic transducers, the so-called directivity factor refers to the mean square sound pressure of a certain frequency at a certain point away from the transmitting ultrasonic transducer on the sound pressure of the main axis of the transmitting sound beam and the difference between the sound pressure passing through this point and the transducer The ratio of the mean square sound pressure at a point on a concentric sphere at the same frequency. For the receiving ultrasonic transducer, it refers to the ratio of the square value of the electromotive force generated by the sound wave of a certain frequency along the main axis of the transducer to the square value of the electromotive force generated by the diffuse sound field with the same frequency and the same root mean square sound pressure. The directivity factor of an ultrasonic transducer can also be expressed in decibels (dB), which is called the directivity index, which is equal to the common logarithm of the directivity factor multiplied by 10. For transmit transducers, the directivity index may also be referred to as the directivity gain.


2. Correct selection of ultrasonic transducers


Ultrasonic transducer is the core component of ultrasonic equipment, and the selection of its characteristic parameters determines the performance of the entire equipment. Correct selection of ultrasonic transducer can make your measurement more accurate.


(1) Understand the use of ultrasonic equipment


Know your own needs, understand the purpose of the small ultrasonic transducer equipment, and understand the characteristics of the required ultrasonic transducer: such as the size of the range, whether it is anti-corrosion, and explosion-proof.


(2) Select the frequency of the ultrasonic transducer


The frequency of ultrasonic waves affects the propagation of ultrasonic waves, and different ultrasonic devices have different frequency requirements. The higher the ultrasonic frequency, the more concentrated the energy and the better the directionality, but the higher the frequency, the greater the ultrasonic attenuation.


(3) Select the incident angle of the ultrasonic transducer


The incident angle determines the installation position of the ultrasonic transducer. In order to ensure the selectivity of the signal received by the probe, the incident angle should be selected to be greater than the first frontage angle and less than the second critical surface angle, generally between 28.7° and 60°.

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