Projeto e desenvolvimento de um analisador de impedância

Abstract

This undergraduate thesis presents the design and development of an impedance analyzer intended for academic, educational, and bench applications, capable of measuring resistance, inductance, and capacitance over a frequency range from 100 Hz to 200 kHz. The motivation for this work is related to the limited availability of affordable instruments that allow frequency response analysis of passive components, a feature typically found only in high-cost equipment. The adopted methodology involved a study of the main impedance measurement methods described in the literature, with the selection of the auto-balancing bridge technique due to its accuracy and suitability for embedded systems. The hardware was developed based on the AD5941 integrated circuit, integrating signal excitation, acquisition, and processing circuits, along with a microcontroller responsible for system control and the human–machine interface. The electrical schematic, printed circuit board layout, and a 3D-printed enclosure were designed. The firmware was implemented using a real-time operating system, enabling measurement automation, frequency sweep operation, and graphical visualization of results on a touch-sensitive display. Experimental validation was performed through comparative tests with commercial reference instruments, evaluating the measurement accuracy of resistors, inductors, and capacitors, as well as the analysis of RLC circuits and the non-ideal behavior of real components. The results indicated a relative error below 2% for resistance measurements in the range from 1 Ω to 100 kΩ, a typical error below 5% for inductance measurements at frequencies above 1 kHz, and an error lower than 2% for capacitance measurements with values equal to or greater than 470 pF over most of the operating frequency range. The prototype also demonstrated the ability to identify phenomena such as resonance, parasitic effects, and impedance variation with frequency. It is concluded that the developed analyzer meets the proposed objectives, presenting satisfactory performance and a favorable cost–benefit ratio, thus constituting an accessible alternative for applications that do not require high-end metrological instrumentation.