Luca Callegaro, Vincenzo D'Elia
LIKE AND UNLIKE IMPEDANCE COMPARISONS WITH THE SAME INSTRUMENT
IEN system for unlike impedance comparison (resistance vs. inductance, or resistance vs. capacitance) is based on an implementation of the three-voltmeter method, which configures both standards in comparison as four terminal-pair, by using automatic electronic compensations to achieve the purpose. Basic relative accuracy of the instrument is between a few parts in 10-6 for comparison of impedances in the range 10 Ω to 10 kΩ, and at frequencies in the range 100 Hz - 10 kHz.
The same system, without any changes in the instrumentation employed or its wiring, can be effectively used also as a four terminal-pair ratio bridge for comparison of like impedances (resistance vs. resistance, or capacitance vs. capacitance), in the same impedance and frequency range. This capability has been checked by conducting measurements of resistance ratios of four terminal-pair ac resistors, having nominal ratios of 1:1 and 10:1. Results show that, for like impedances, relative accuracies at the level of a few 10-7 can be within reach.