Quadrature Bridge for R-C Comparisons based on Polyphase Digital Synthesis

IEEE Trans. Instrum. Meas.

Ortolano

et al. 2015

We present here the concept of three-arm current comparator impedance bridge, which allows one to perform comparisons among three unlike impedances. Its purpose is the calibration of impedances having arbitrary phase angles against calibrated nearly pure impedances. An analysis of the bridge optimal setting and proper operation is presented. To test the concept, a two-terminal-pair digitally assisted bridge has been realized; preliminary measurements of an air-core inductor and of an RC network versus decadic resistance and capacitance standards, at kilohertz frequency, have been performed. The bridge measurements are compatible with previous knowledge of the standard values with relative deviations of parts in 10^{-5}

Section: B Bridgementioning

confidence: 99%

A Three-Arm Current Comparator Bridge for Impedance Comparisons Over the Complex Plane

Callegaro

IEEE Trans. Instrum. Meas.

Ortolano

et al. 2015

“…4. The bridge measure the product C 1 C 2 in terms of R 1 R 2 ; it is an evolution of a similar bridge presented in [36].…”

Section: Quadrature Bridgementioning

confidence: 99%

Realization of the farad from the dc quantum Hall effect with digitally assisted impedance bridges

Callegaro¹,

Trinchera

2010

Metrologia

A new traceability chain for the derivation of the farad from dc quantum Hall effect has been implemented at INRIM. Main components of the chain are two new coaxial transformer bridges: a resistance ratio bridge, and a quadrature bridge, both operating at 1541 Hz. The bridges are energized and controlled with a polyphase direct-digital-synthesizer, which permits to achieve both main and auxiliary equilibria in an automated way; the bridges and do not include any variable inductive divider or variable impedance box. The relative uncertainty in the realization of the farad, at the level of 1000 pF, is estimated to be 64 × 10 −9 . A first verification of the realization is given by a comparison with the maintained national capacitance standard, where an agreement between measurements within their relative combined uncertainty of 420 × 10 −9 is obtained. § Corresponding author (l.callegaro@inrim.it)

“…Recently, we have shown that the concept of digitallyassisted bridges permit to achieve measurement uncertainties at the 10 −8 level, with the potential for further improvements [2], [3].…”

Section: Introductionmentioning

confidence: 99%

A digitally-assisted current comparator for audio frequency impedance scaling

Trinchera

2012 Conference on Precision Electromagnetic Measurements

Capra

et al. 2012

A current comparator bridge, suitable for the comparison of four terminal-pair impedance standards in the audio frequency range at 1:1 and 10:1 nominal ratios is here presented. The bridge is digitally-assisted: its accuracy is granted by electromagnetic devices, but voltages and current required to reach principal and auxiliary equilibria are given by a polyphase directdigital-synthesis generator. The measurement is semi-automated and equilibrium can be achieved in a few minutes. Measurements performed on calculable resistors give a base accuracy of a few parts in 10 7 , with the potential for further improvements.