PSI - Issue 43

Dagmar Faktorová et al. / Procedia Structural Integrity 43 (2023) 288–293 Author name / Structural Integrity Procedia 00 (2022) 000 – 000

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4 Discussion To demonstrate the presented implementation of the proposed impedance converter concept, as an example of use, the measurement of the magnitude-frequency response and the phase-frequency response of an ultrasonic transducer in the application of high frequency fatigue tests and measurement the thickness of aluminum foil using changes in the impedance due to the influence of eddy currents are shown in Fig. 5 and Fig. 6 respectively. The presented concept of impedance converter implemented on a microcontroller chip can be further modified. Because the used MCU has two independent DAC converters, their combination makes it possible to control and adjust the DC component of the excitation voltage without reducing the bit resolution of the output voltage. Two independent DDS generators with a common LUT table for multifrequency analysis can be implemented and their outputs can be summed using an instrument amplifier.

Fig. 5. Impedance characteristics of the loaded and unloaded ultrasonic transducer.

Fig. 6. Normaliz ed impedance diagrams of aluminum foil (thickness n*16.5[μm]) for frequencies 2 kHz, 10 kHz and 20 kHz, probe R = 30 Ω, L = 1.6 mH, 260 windings on the ferrite core  4.8 mm. 5 Conclusion The paper presents the concept of impedance analyzer/converter implementation on a microcontroller chip as a technological basis for the construction of sensors for IoT or in-situ measurements. The implementation itself is relatively small, the compiled code (without tables) takes up less than 3 kB. When the suitable external components will be used, a miniature design is possible, which allows the analyzer to be built directly into the sensor with the