An automatic bridge for the comparison of the impedance standards

The paper describes an automatic autotransformer bridge for comparison of the impedances (capacitance, resistance, inductance, etc.) over a wide range of values. The proposed bridge structure, algorithm and processing of two unbalance signals eliminates the influence of the cable impedance on the measurement results. The autotransformer bridge uses only one inductive divider for a wide range of measurement. Automation of the measurement is based on a variational method of the precise bridge unbalance determination. This simplifies the bridge inductive divider and twice reduces the number of its digits without decreasing of the automatic bridge accuracy. The bridge measurement uncertainty on main ranges is better than 1 ppm; the sensitivity is better than 0.01 ppm.