Some Features of the Calibration Equipment for Measuring the Parameters of Impedance

Abstract

Peculiarities of the accurate impedance meters calibration are considered. Author show that most important and complicate part of calibration procedure consists in determination of two uncertainty components: additive error and error, caused by nonlinearity of the meter transfer function. Problems of the determination of the additive error are caused by the fact, that there no exist accurate standard of the zero impedance. Author considers the creation of proper zero impedance standard, whose impedance can be arbitrarily close to zero and its impedance remnant can be estimated on the base of its geometrical dimensions. Implementation of such standard is very simple, cheap, and easily carried out. This standard works well on DC. Standard of zero impedance for AC measurement consists of two coaxial T-branches, which are connected through insertion piece. Such standard eliminates influence of the possible mutual inductive connection between current and voltage loops of the proper cables, which connect the “zero impedance standard” and measuring devise. To determine nonlinearity of the transfer function author analyze using of the non accurate resistive or alternative impedance dividers. To use such dividers in whole range of measurements special structures of these dividers where developed. In these structures measurement of the divider standards are provided together with impedance of their terminals. It eliminates influence of the impedance of these terminals on the accuracy of meter calibration or unit transfer. Special complex of two-standards dividers were developed to simplify the accurate calibration of the impedance meters.

Keywords

• calibration, divider, four pair, uncertainty, calculable zero impedance standard.