Four terminal-pair coaxial capacitance standards with nominal values of 1 pF and 10 pF have been realized and, using a uniform transmission line model, their frequency dependences have been evaluated. 1:1 comparisons against reference capacitors with known frequency dependence (Agilent 16381A and Agilent 16382A) have shown that the values of the 1 pF and the 10 pF standard change by 0,04 % and -0,05 % respectively when frequency increases from 1 kHz to 1 MHz.

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Four terminal-pair coaxial standards of capacitance

The air capacitor has a very good frequency response and is suitable to act as an impedance standard for the frequency range of several MHz. In this paper, the determination of capacitance at high frequency is discussed. It should be noted that the result depends on the form of equivalent circuit used. An ordinary simple circuit of lumped parameters gives an inaccurate result and a distributed parameter circuit gives a better result for capacitance at high frequency. This work is important when an air capacitor is intended for use as an a reference standard.

The equivalent circuit of air capacitor in high frequency range

Distributed shunt impedances and leakage impedances in the windings of inductive voltage dividers (IVDs) cause the major components of ac voltage ratio errors, and these two kinds of errors had been well investigated from both theory and experiments. The winding -to-screen capacitances of IVDs can also introduce small but significant ratio error. A theoretical analysis result for this kind of error has been obtained, and a method to correct this kind of error has been presented.

Zhao Jianting

Papers

The equivalent circuit of air capacitor in high frequency range

A method to correct inductive voltage dividers error caused by capacitances between winding and screen