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

Abstract

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. Index Terms-Binary inductive current divider (BICD), current shunt, four-terminal mutual inductor, residual inductance, substitution method, time constant.

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

“…In the measurement setup for the calibration of the relationships between two currents of BICD in Fig.1 To reduce the influence from input terminal of the 792A loading the output of shunt R S2 , a shunt with 0.1 Ω has been built. The frequency response of the shunt can be calibrated against time constant standard with known relationship at frequencies to 200 kHz [7], and the result shows in Table II. Since the resistance of the shunt is 0.1 Ω, the output voltage of the shunt is set in the range from 100 mV down to 1 mV by changing the current in two branches from 1 A down to 10mA.…”

A Circular Loop Time Constant Standard

“…The time constant τ can be expressed approximately for most values of R and C as [3][4][5] (1) with the phase angle of the standard (2) The circular loop is wound using a manganin wire with the diameter 0.07 mm on a circular plastic former (Fig. 2).…”

“…In [3] a simple resistance standard with calculable time constant is described. In [4] a coaxial time constant standard for the determination of phase angle errors of current shunt is presented.…”

“…Therefore, the phase an important for the determination of the phase angle errors of precision Additionally, it is also needed in other applications like capacitor loss fac Classical designs of calculable resistors include Haddad, bifilar and folded loop simple resistance standard with calculable time constant is described. In [4] constant standard for the determination of phase angle errors of current shunt…”

Four-terminal mutual inductor for calibration of the lock-in amplifier at mV ranges

“…A coaxial four-terminal time constant standard is developed to measure the phase angle errors of the ac current shunts at high frequencies [1]. In the measurement of the residual inductance of the time constant, a lock-in amplifier is used.…”