Piezoelectric wafer eigenfrequency measurement method

Abstract

The invention relates to a piezoelectric wafer eigenfrequency measurement method. The method comprises the following steps: (1) arranging a measurement device including a function generator, a piezoelectric wafer and a digital oscilloscope; (2) starting the function generator to generate Tone-Burst sine wave signals with a certain period number, conducting electric pulse excitation to the piezoelectric wafer by the function generator at a frequency f, stopping the electric pulse excitation to the piezoelectric wafer when the function generator completes the period number, enabling the piezoelectric wafer to start vibrating freely, and collecting the free vibration signal between two electrodes of the piezoelectric wafer by the digital oscilloscope; (3) adjusting the digital oscilloscope to amplify the free vibration signal between the two electrodes of the piezoelectric wafer in the step (2), and processing the amplified signal by fast Fourier transform; (4) extracting the frequency of the peak on the spectrogram obtained by Fourier transform in the step (3) to obtain the eigenfrequency of the piezoelectric wafer to be tested; and (5) changing the frequency f of the function generator in the step (2), repeating the step (3) and step (4), and measuring each eigenfrequency of the piezoelectric wafer.

Description

technical field [0001] The invention relates to a measuring method, in particular to a measuring method for the eigenfrequency of a piezoelectric wafer. Background technique [0002] Piezoelectric wafers (piezoelectric ceramics) are the core components of sensors such as non-destructive testing ultrasonic probes and seabed sonars in the prior art due to their high electromechanical conversion coefficient and stable performance. Measuring the technical performance parameters such as the eigenfrequency of the piezoelectric wafer is of great significance for selecting a suitable piezoelectric wafer as a sensor. At present, the measurement method of the eigenfrequency of the piezoelectric wafer is mainly the transmission line method. The specific steps are as follows: firstly, a signal generator (also known as a function generator) is used to generate a continuous sine wave electrical signal with adjustable frequency, which is applied to the piezoelectric wafer. In the measurem...

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Problems solved by technology

[0003] Although the transmission line method can measure the series resonant frequency and parallel resonant frequency of the piezoelectric wafer at the same time, it needs to be carefully adjusted near the characteristic frequency and repeatedly observed the indication value of the high-frequency voltmeter. The measurement is time-consuming and not accurate enough.

And in this measurement method, there are also many limiting conditions, such as requiring the output impedance of the signal generator to be lower than the impedance of the piezoelectric wafer, requiring the impedance of the piezoelectric wafer whose matching resistance is greater than 10 times, etc., and before the measurement, this The impedance value is unknown and difficult to determine in advance. In addition, there are strict requirements on the distributed capacitance of the measurement circuit

Moreover, the transmission line method also has requirements for the size of the sample. For example, for a piezoelectric wafer with a disc-shaped thickness vibration mode, the diameter is required to be much larger than the thickness; for a longitudinally vibrating round rod-shaped piezoelectric wafer, the diameter is required to be much smaller than the length. For piezoelectric wafers with little difference in size, there are often errors in the measurement results by using the transmission line method

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