Wenfang Liu

A Coaxial Time Constant Standard for the Determination of Phase Angle Errors of Current Shunts

This paper describes a new method to determine the phase angle errors of ac shunts by measuring the inductance and distributed capacitance. A 1-Ω shunt of coaxial design has been developed as the time constant standard. A coaxial inductor with identical structure as the time constant standard has been developed. A four-terminal mutual inductor has also been built for the measurement of the inductance of the time constant standard. The method is based on the use of a binary inductive current divider to compare the inductor with the mutual inductor. The standard uncertainty of the inductance measurement of the time constant standard is within 28 pH at frequencies up to 200 kHz. The expanded uncertainty of the phase angle errors is from 0.4 μrad at 1 kHz to 80.0 μrad at 200 kHz at 1 A.

Using inductive voltage divider to measure the millivolt ac voltage at frequencies up to 100 kHz

A method to measure the millivolt ac voltage has been described. The method is based on use of the binary inductive voltage divider and 2n:1IVDs. The measurement setup for the calibration of the 2n:1IVD has been proposed and the results have also been given at frequencies up to 100 kHz.

Determination of Equivalent Inductance of Current Shunts at Frequency Up to 200 kHz

We report on the measurement techniques and results of the equivalent inductance of current shunts at frequencies from 50 to 200 kHz. With a three-branch binary inductive current divider and difference detection transformer, the equivalent inductance of the cagelike shunts was measured against a set of four-terminal resistors whose time constants were accurately determined. The verification experiments for the systematic errors of the measurement setup and the phase comparator with the current ratio of 2 : 1 are also presented.

Measurement of the Phase Angle Errors of High Current Shunts at Frequencies up to 100 kHz

This paper describes a new method for determining phase angle errors of shunts with rated currents at 50 and 100 A at frequencies from 25 to 100 kHz. The method is based on the use of a three-branch binary inductive current divider to measure the phase angle errors of high current shunts against a phase angle reference standard with only one step. An inductive high current shunt has been designed using a 100:1 current transformer connected in parallel with a 1-

Design and self-calibration of cascaded inductive voltage divider with ratio of 2 n :1

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Design and self-calibration of the RVD with serial-parallel connection

shunt. The phase angle errors of resistive high current shunts and the inductive high current shunt have been measured. The level dependence in phase angle errors of three different types of high current shunts has been evaluated at currents from 1 to 100 A. The measurement results and standard uncertainties of the phase angle errors of high current shunts are reported.

Design of the current comparator for measuring the current shunts at common ground

A set of cascaded IVDs with ratio of 2n:1 has been designed and self-calibrated. The IVD is built based on the use of the cascaded structure between the IVD with ratio of 2n-1:1 and BIVD. The amplitude errors and phase angle errors of the IVDs with ratios from 2:1 to 256:1 have been measured by means of sampling method at frequencies ranging from 10 kHz to 100 kHz, and the measurement results are presented.

Self-calibration of the current comparator with common ground

A new design of resistive voltage divider with serial-parallel connection has been built. A self-calibration method has also been proposed to determine the phase angle errors of the resistive voltage divider. The measurement has been done at frequencies from 10 kHz to 100 kHz to calibrate two RVDs with ratio of 100:1 and results are presented.

A new method to compare two thermal current converters at common ground at frequency up to 200 kHz

A new design of current comparator to compare two current shunts at common ground has been proposed in this paper. The comparator is designed by several current transformers with ratio of 1:1 in series connection. Based on this design structure, current comparator with ratio of 2:1, 5:1 and 10:1 have been developed and presented.

A new method to measure millivolt ac voltage at frequencies up to 200 kHz

A method to measure the phase angle errors and amplitude errors of the current comparators with ratio of 2:1, 5:1 and 10:1 has been described. The method is based on the use of the differential current transformer to determine the current relationship of the current comparator. The measurements have been done at frequencies from 10 kHz to 100 kHz, and the results are presented.