Design Of Impedance Measurement System Based On ARM

Impedance is described network and an important parameter in the system, is a complexquantity, with its signal frequency and voltage changing. In the lumped parameter system,show that energy loss is resistance element parameter R, and indicate that stored energy andthe change of the system parameters is inductance element L, and capacitance element C.Strictly electromagnetic phenomena in the analysis of these components is very complex, soin general, tend to view them as the same constants for measurement. Is proposed in order torealize measurement of impedance in different frequency range of the measurement, theimpedance of the object to be tested.This paper expounds the STM32control the impedance measurement system design andimplementation of the method. STM32is introduced based on the architecture of ST companycore M332-bit microcontroller series, adopt efficient harvard structure, level3lines, withindependent instruction bus and data bus, can satisfy the high real-time requirements in thefield of control; STM32processor in this system mainly complete control of the synchronousorthogonal signal source, AD sampling, calculation of impedance, liquid crystal display (LCD)test results. In the aspect of software design, the use of STM32library provides a completeand efficient official firmware, without using assembler operation peripherals characteristics,reduces the code development cycle, reduce the difficulty of development, improve thereadability and maintainability of the program.Need two road impedance measuring system with strict orthogonal frequency signalsource, signal frequency is adjustable within the required range. The direct digital frequencysynthesis technology as the core chip AD9854, designed the orthogonal signal source is usedfor impedance measurement system for synchronization. In order to effectively suppress noiseinterference and the double phase lock-in amplifier. Synchronous signal0°reference signalprovides the drive for impedance converting circuit, the converted voltage signal through themultiplier MLT04, and synchronous signal of0°and90°, with two way AD are collected atthe same time, get the impedance values of measured object.Finally, to the design of the impedance measurement system based on ARM was testedand validated. Analog circuit under test chose first-order RC low-pass filter, the experimentalresults show that the method has high degree of automation, test results error is small, stronganti-interference ability.