Abstract：To compensate the end effect error in a vertical calculable cross-capacitor (VCCC) with a fixed and a movable guard electrode, an electrical compensation approach is adopted by the National Institute of Metrology, China (NIM). After continuous improvements and modifications, the latest optimal hollow active auxiliary electrode (OHAAE) was developed, which was different from a nosepiece used by other national institutes of metrology in the world, and its electrical performances including the compensation effectiveness, eccentricity effect and so on were investigated on the NIMs model capacitor device.Instead of the nosepiece, the latest OHAAE was successfully applied and the relative standard uncertainty of the reproduction of 1 pF capacitance unit from the new NIMs VCCC was 1.0×10-8.
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