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Name of Experiment：the application of power amplifier based on the fabrication of a two-dimensional elliptical ultrasonic oscillator and the measurement of vibration characteristics

Research Direction：test and verify the actual resonant frequency of the fabricated piezoelectric ceramic oscillator is the same as the design

Experiment Contents：by dividing the electrode on a large piece of piezoceramics, the effect of four piezoceramics are actually realized. The electrode material is Ag, the power amplifier drives the piezoceramics to be plated on the surface of the piezoceramics by coating method, and the piezoceramics and 304 stainless steel matrix are bonded by epoxy resin to realize the vibration transfer.

Experiment Process：

The circuit diagram used for the analysis of resonance characteristics is shown in the figure. The frequency characteristic analyzer provides the output signal of frequency sweep, and can measure the voltage at both ends of the piezoelectric ceramic oscillator and the current through the piezoelectric ceramic oscillator. The power amplifier (ATA-4052) amplifies the input signal and adds it to the oscillator circuit. The piezoelectric ceramic oscillator is connected in series with 1 ohm standard resistance. The frequency sweep range is 20K-30khz. When only two separated electrodes are energized, the B4 mode of the oscillator is excited, and when four electrodes are energized at the same time, the L1 mode of the oscillator is excited.

Experiment Result：

1.It can be seen from the figure that the resonant frequency of the oscillator mode B4 is 24.10kHz and the inverse resonant frequency is 24.22kHz, while the resonant frequency of the oscillator mode L1 is 24.01kHz and the inverse resonant frequency is 24.24kHz. The difference between the resonant frequencies of the two vibration modes is about 0.09kHz, and this degree of error is within the permissible range when using this ultrasonic oscillator. In addition, due to the small resonance frequency difference between the two oscillation modes, the maximum amplitude can be obtained at the same frequency for both longitudinal and bending vibration, and the amplitude of the synthesized elliptic vibration will be the largest.

On the other hand, the difference between the anti-resonance points in the two vibration modes is about 0.02kHz, which is very small. Because when the ultrasonic oscillator is excited at the resonance point, although the impedance is small and the amplitude is maximum,however, if a frequency close to the resonance point is used, a relatively large load will be applied to the piezoceramics, which may lead to rupture or rupture of the piezoceramics. When excited at the anti-resonance point, the impedance increases and the power consumption is minimized. Therefore, the frequency of the excitation signal is usually located at the anti-resonance point, and the difference of 0.02kHz meets the requirement. Therefore, it can be seen that the oscillator shown in the figure will produce the optimal ultrasonic elliptical trajectory when excited at the frequency of 24.22kHz.

Impedance characteristic curve of L1 mode        Impedance characteristic curve of B4 mode

2.The optimal ultrasonic elliptical trajectory is produced when the oscillator is excited at 24.22kHz.

Comparison of impedance characteristics between L1 mode and B4 mode

The performance of the amplifier in the experiment：

Drive the piezoelectric ceramics, ensure the ultrasonic wave can output a complete sinusoidal waveform, and can freely schedule the gain amplitude, so as to achieve the experimental purpose of freely switching the strength of the ultrasonic signal under different light intensities.