Abstract
An impedance measuring method (IML) based on the least squares method is consists of a pair of current-to-voltage converter (CVC) composed with an operational amplifier, a personal computer equipped with a pair of analog-to-digital converter, an ac voltage source. Two impedances ZP and ZQ are connected with the ac voltage source in parallel. Each current flowing through ZP and ZQ is converted to a voltage with the CVC. An amplitude and a phase of the voltage are estimated by the least squares method. Then, a ratio of Zr to ZQ is calculated.
Resistance ratios of 1:1 and 3:1 composed with some combinations of metal film resistors of which nominal values are 1, 3, 100 and 300 [kΩ] are measured by this method in frequency range of 100[Hz]to 20[kHz]. It is estimated that the uncertainties of the average values of 10 measurements are less than 0.005[%] in magnitude and 0.05 [mrad] in phase angle.
