Impedance Measuring Device Based on an AC Potentiometer

This paper describes a novel ac potentiometer composed of digital sinewave generators and inductive voltage dividers (IVD's) for the comparison of unlike impedances with different nominal values from a few 10 Q up to 1 kΩ in the frequency range between 50 Hz and 1 kHz. As an example, the resistance of a 100-Ω standard resistor may be compared with the capacitance of a 1-μF standard capacitor at a frequency of 400 Hz with a relative uncertainty of about 1 X 10-6 which is mainly due to the short-term stability of the digital sources.