Research and Design of Human Impedance Measuring Instrument Based on the Method of Multi-Frequency and Multi-Segment

Traditional human impedance measuring instruments adopt excitation signal with single frequency, which makes the measurement result cannot reflect the true character of human impedance. Meanwhile, they measure the whole body impedance, which makes the measurement result cannot reflect the body segments´ impedance character that is very significant on many conditions, such as the measure of the body composition and the analysis of the blood flow. To solve these problems, multifrequency and multi-segment measuring method is introduced. In the design of this human impedance measuring instrument, ARM microprocessor is adopted as the microcontroller. The multifrequency signals are generated by direct digital synthesis (DDS) technology. At the process of analyzing the human impedance, fast Fourier transform (FFT) algorithm is used. The test for the instrument after the finished design verifies that the instrument measures impedance accurately and has a high precision. So the instrument can be applied in the area of both clinic and research.