Abstract
As it contains elements of complete digital impedance meter, the AD5933
integrated circuit is an interesting solution for impedance measurements.
However, its use for measurements in a wide range of impedances and
frequencies requires an additional digital and analogue circuitry. This
paper presents the design and performance of a simple impedance meter
based on the AD5933 IC. Apart from the AD5933 IC it consists of a clock
generator with a programmable prescaler, a novel DC offset canceller for
the excitation signal based on peak detectors and a current to voltage
converter with switchable conversion ratios. The authors proposed a simple
method for choosing the measurement frequency to minimalize errors
resulting from the spectral leakage and distortion caused by a lack of an
anti-aliasing filter in the DDS generator. Additionally, a novel method
for the AD5933 IC calibration was proposed. It consists in a mathematical
compensation of the systematic error occurring in the argument of the
value returned from the AD5933 IC as a result. The performance of the
whole system is demonstrated in an exemplary measurement.
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