A simple methodology to develop bifilar, quadrifilar, and octofilar calculable resistors

Abstract

This paper describes the development of bifilar, quadrifilar, and octofilar Calculable Resistors (CRs). The research involves Evanohm-S and Isaohm wire heat treatment processes to achieve temperature coefficients less than 0.5 μΩ/Ω/°C in the CR's wire resistance element, tests of different terminal-wire joining techniques, and construction aspects achieving a stability of less than 0.05 μΩ/Ω/day. This kind of construction methodology has not been presented in detail in previous CR papers, and it is essential to accomplish the correct parameters of a CR. Without it, the development of a CR can take several months or even years. A comparison between CRs developed in this research and a CR from the Federal Institute of Metrology (METAS) in Switzerland was carried out. Measurement results between the 10 kΩ octofilar CR and the METAS 1 kΩ coaxial CR show an agreement better than 0.35 μΩ/Ω through the audio-frequency range. Therefore, the octofilar CR can be used as an AC resistance reference with traceability to the quantum Hall resistance in DC.