Precise high resistance comparison between the NMIJ traveling dual source bridge and the NIST adapted Wheatstone bridge

Abstract

A precise high resistance comparison was performed between the traveling dual-source bridge developed by the national metrology institute of Japan (NMIJ) and the adapted Wheatstone bridge of the national institute of standards and technology (NIST) from 10 MΩ to 100~TΩ at NIST. The NMIJ traveling bridge was shipped to NIST Gaithersburg and was installed right next to the NIST bridge and these bridges alternately measured the resistance ratio of the high resistance standards, without moving the location of the resistors inside the temperature-controlled air bath. Having the bridges and resistance standards in the same location for the comparison decreased the transportation and temperature coefficient effects on the resistance standards, contributing to the excellent agreement of the measured values. The NMIJ traveling bridge used an 8.5-digit digital multimeter and a relay switch box to determine a resistance ratio by measuring the ratio of the voltages applied to the resistors. The comparison was started from 10 MΩ based on the same 1 MΩ standard resistor calibrated using a NIST 2-terminal cryogenic current comparator bridge, and standard resistors from 10 MΩ to 100 TΩ were calibrated by repeating 10:1 scaling measurements with both systems. Excellent agreement was obtained within the uncertainty of all resistance ranges and the difference between both systems was less than 1 μΩ/Ω up to 1 TΩ and the degrees of equivalence for 10 TΩ and 100 TΩ were less than 6 μΩ/Ω.