According to the different feedback signals, the frequency tracking method of the veterinary ultrasound generator can be divided into current feedback and phase feedback. What is current feedback? What is phase feedback? Let's take a detailed look at it according to different principles

Current feedback of veterinary ultrasound generator

The current feedback method uses the principle of the impedance amplitude-frequency characteristic of the transducer. The impedance amplitude of the veterinary ultrasound transducer is the smallest at the resonant frequency. When it deviates from the resonant frequency, the impedance amplitude will decrease sharply as the offset increases. The impedance amplitude-frequency characteristic of the veterinary ultrasound transducer can be measured by an impedance analyzer. When the driving voltage is constant, the current is inversely proportional to the impedance of the transducer. The current is the largest at the resonant frequency. When it deviates from the resonant frequency, the current will decrease sharply as the offset increases. The ultrasonic generator determines how to adjust the driving frequency by detecting the magnitude of the current. For example, when the veterinary B-ultrasound generator increases the driving frequency, if the current increases accordingly, it means that the current driving frequency is less than the resonant frequency of the transducer, and the veterinary B-ultrasound generator should increase the driving frequency; if the current decreases, it means that the current driving frequency is greater than the resonant frequency of the transducer, and the ultrasonic generator should reduce the driving frequency. After repeated adjustments, the final driving frequency will be consistent with the resonant frequency of the transducer.

Phase feedback type of veterinary B-ultrasound generator

The phase feedback type uses the principle of the impedance phase-frequency characteristics of the transducer. The impedance phase angle of the veterinary B-ultrasound transducer is zero at the resonant frequency; when the frequency is greater than the resonant frequency, the impedance phase angle is greater than zero; when the frequency is less than the resonant frequency, the impedance phase angle is less than zero. The impedance phase angle corresponds to the phase difference between current and voltage. The veterinary B-ultrasound generator determines how to adjust the frequency by detecting the phase difference between current and voltage. If the phase difference is less than zero, it means that the current driving frequency is less than the resonant frequency, and the veterinary B-ultrasound generator should increase the driving frequency; if the phase difference is greater than zero, it means that the current driving frequency is greater than the resonant frequency, and the ultrasonic generator should reduce the driving frequency.

link: https://www.bxlimage.com/nw/769.html