Measurement of four terminal-pair impedances by means of a sine-fit based technique

This paper deals with an impedance measuring system that can be arranged by means of general purpose instruments usually available in most calibration laboratories, without requiring dedicated and costly devices. Impedance measurements are performed by employing a comparison technique and taking advantage of a sine-fit processing to make negligible the effect of noise and signal distortion on the obtained results. The system have been specialized for the measurement of impedances defined as four terminal-pair networks, therefore a suitable technique has been implemented in order to compensate for the voltages at the impedance low-potential ports. Both measuring and compensation processes are automatically managed by means of a personal computer, thus giving the possibility to remotely exercise the calibration of impedance standards through the Internet. Preliminary results are described in the paper, which have shown the functionality of the whole system. The expected measurement uncertainty is respectively of 0.05% and of 0.04° for amplitude and phase of the measured impedance in the frequency range of 40 Hz to 10 kHz.