Power amplifier application--piezoelectric ceramic impedance test, Antai Electronics Manufacturer

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Power amplifier application--piezoelectric ceramic impedance test, Antai Electronics Manufacturer [Copy link]

Common impedance devices are mostly nonlinear, such as the impedance-temperature curve of resistance devices such as metal oxides and metal platinum, which is a typical nonlinear curve. The impedance characteristics of the piezoelectric ceramic stator of the ultrasonic motor, its operating voltage is generally above 100V peak-to-peak, and the impedance modulus has a resonance point and an anti-resonance point. The impedance is the smallest at the resonance point and the largest at the anti-resonance point. This paper uses the basic principle of large resistance parallel and small resistance series voltage and current meter, based on LabVIEW program and supporting NIPXI modular instrument design test system, to measure the swept frequency impedance of the piezoelectric ceramic stator under different excitation voltage amplitudes, analyze its resonance point and anti-resonance point frequency, and image offset under different excitation voltage amplitudes.

The piezoelectric ceramic impedance test under working voltage based on LabVIEW, the test system is as follows:

Experimental process:

The test system is mainly composed of LabVIEW program, modular instrument signal generator, power amplifier , conditioning voltage divider circuit and modular instrument data acquisition card. First, the computer program controls the start and end frequency, voltage amplitude, etc. of the signal generator frequency sweep, and then the power amplifier amplifies the voltage to the required voltage amplitude according to the specified ratio and adds it to the impedance to be measured. Then the conditioning voltage divider circuit linearly amplifies or reduces the voltage and current to within the range of the acquisition card, and the data acquisition card collects voltage, current and other data, and processes the data inside LabVIEW.

Test results:

(1) The system is used to test the piezoelectric ceramic stator with a single-phase excitation source of different voltage amplitudes. The impedance modulus and impedance angle obtained at 20V vary with frequency:

(2) The system is used to measure the impedance of piezoelectric ceramics at a higher working voltage of 120V peak-to-peak:

From the measured images, it can be seen that under the working voltage of 20V and 120V, the impedance modulus images reflect the resonance point and anti-resonance point. The impedance modulus is the smallest at the resonance point and the largest at the anti-resonance point. The impedance angle jumps between the resonance frequency and the anti-resonance frequency, and the rest of the frequency bands are always around -90°.

By comparing the measurement images of different voltages, it can be found that the impedance characteristic curve is slightly offset under high voltage, and the frequency of the resonance point is slightly shifted to the left, from 77.7KHz at 20V to about 77.2KHz at 120V. This shows that under different voltage excitation conditions, the frequency of the resonance point of piezoelectric ceramics will shift, and as the voltage gradually increases, the resonance frequency point will gradually decrease, which means that the results of the normal working voltage impedance characteristic test will be more accurate; regardless of the voltage amplitude, the impedance angle peak is around 50°~60°. According to the basic circuit theorem, between the resonant frequency and the anti-resonant frequency, the piezoelectric ceramic has a resistance-capacitance or resistance-inductance characteristic, and performs mechanical work to the outside world. In other frequency bands, it is always a pure capacitive characteristic of -90°, and does not perform work to the outside world.