Complex Impedance meter

By Yi Zhang

The Complex Impedance Meter presented in this report is a high precision, low power consumption impedance conversion system which provides programmable frequency sweep and tuning capability for impedance measurement from 5kΩ to 1.1MΩ with system accuracy of 2%. The system is built with an AVR microcontroller ATmega32, an Analog Device network analyzer AD5933, two analog multiplexers ADG706, a CTS low jitter clock oscillator MXO45HS, two accurate resistor networks with designed resistance values and a liquid crystal display RCM2034R. It allows an unknown external impedance to be excited with a known frequency. The response signal from the impedance is sampled by the on board ADC, and the DFT is processed by a DSP engine which returns a real and imaginary data word at each excitation frequency. The magnitude of these data words is further scaled by calibrated Gain Factor in order to return the actual impedance value. The prototype of the system is implemented and system calibration is done to improve the overall accuracy.

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