This paper describes the process and implementation of a commercially available Quantum Hall Resistance System into a Primary Standards Calibration Laboratory. Topics include system design, component descriptions and verification of the sample operating characteristics, including the measurement of the QHR device in the MI 6800A system when compared to a cryogenic current comparator. (CCC) The system verification referenced is located at the Institute for National Measurement Standards (INMS) at the National Research Council (NRC), Canada. Also included is a brief description of the most recent on-site installation, the measurement results using the QHR 6800A system to establish the value of a 1 kΩ resistor and the automated measurement process from the 1 kΩ resistor up to the 10 kΩ and down to the 1 Ω value.
We have compared a 100 Ω wire resistor with a QHR (step i = 2) using a cryogenic current comparator bridge and using a commercial dc room temperature current comparator bridge. In the latter case the measurement was made via an intermediary (1 kΩ) wire resistor. The difference between the values obtained for the 100 Ω resistor using the two bridges is – 0.3 ± 1.4 μΩ, or – 0.003 ± 0.014 ppm.
The principle of the Direct Current Comparator has been around for some 30 years, however, very little work has been done towards automation. This paper describes a bridge for measuring resistance ratios in the range of 0.001 ohms to 10,000 ohms using a microprocessor controlled automated DC Current Comparator with IEEE-488 to an uncertainty of better than 0.1 ppm from 1 ohm to 1000 ohms and 0.2 ppm at the 0.1 ohm and 10,000 ohm level.
Outlines the recent development of the “QuantW”, an affordable, portable quantised Hall resistance (QHR) standard that uses as its measuring component a room temperature DC current comparator bridge. We describe the characteristics of the QHR devices developed for this system, and give details of the refrigerator and integrated 8 T magnet which can be top-loaded as a single unit into a transport dewar. We discuss the measurements required to ensure an accurate transfer from a QHR device to a wire resistor, and show that the QuantW can be used to meet these requirements.
It has been observed that several standard platinum resistance thermometers show resistance leakage due to humidity inside their sheath. This insulation leakage depends on the frequency of the Resistance Bridge that is used for the measurement of the platinum resistance thermometers, because of the polarization of the water molecules in the thermometer.
Therefore, a set of standard platinum resistance thermometers has been calibrated between the triple point of mercury and the melting point of gallium with D.C. and a.c. bridges at different frequencies, in order to investigate the polarisation effect due to humidity. At the triple point of water, a larger polarization effect was observed than at the melting point of gallium, while no such effect was observed at the triple point of mercury. This is due to the different values of the water vapor pressure at the temperatures of the calibration fixed points.
The calibration results so obtained are compared and analyzed, and information on the reproducibility and accuracy of the ITS-90 realization in this range is presented.
Two techniques are described for measuring resistance ratios from 1μOhm to 1G Ohm using the direct current Comparator Bridge and the binary voltage divider principles with uncertainties in the sub PPM level.
The paper outlines the advantages and disadvantages of the two techniques for use in primary standards for the measurement of resistance. Both techniques are based on the latest research performed by the National Research Council of Canada (NRCC).
Measuring Resistance Ratios:
Passing a current through two or more resistors in series and measuring the ratio of voltages developed across the resistors.
Passing known ratios of current through each resistor is equal.
Binary Voltage Divider and Direct Current Comparator: Their History, Limitations, Advantages, Applications and Block Diagrams.
The DC Current Comparator Principle was developed in the late 1960’s. The technology was later commercialized as a manual device for both resistance and temperature measurements. In 1987, Measurements International enhanced the DC Technology in the 6010B bridge.
In comparison to AC Bridges, DC bridges depend on a smaller number of components to achieve their performance, the inherent stability coming from the DC Comparator, which is not subject to temperature variations or warm up.
A current comparator technique, applied to several auxiliary instruments, enables accurate power measurements to be made for measuring losses in medium and large transformers. The instruments include high voltage active dividers with nominal outputs of 120 volts, a current transformer with nominal output of 1 A and precision wattmeters. Two stage compensated current transformer technology is used in each instrument to achieve uncertainties of < 10 ppm in magnitude and phase respectively. In the high voltage divider, the current comparator is used in a feedback loop to correct the magnitude and phase errors of the associated outputs. This paper discusses the technology used and the associated uncertainties of the instruments to achieve a full-scale system uncertainty of < 50 ppm at all power factors.
An automatic ratio bridge based on BVD is used to take measurement up to 1 GΩ at NIM. Adopting a “Virtual Null” mode efficiently reduces effects of insulation of bridge and offset current of detector. The measurement of a 100 MΩ Hamon resistor shows an agreement of 1 parts in 106 at ratio 1 GΩ:100 MΩ.
A practical procedure for ratio measurement uncertainty estimation of auto DCC Bridge is described. By comparison with CCC, the result is confirmed.
Abstract: A 1 Gohm and 10 Gohm Inter comparison was performed by various Primary Level Laboratories in Japan in an effort to help understand there measurement capabilities. Reported are the results and findings of this inter comparison as presented at NCSLI Japan in Tokyo, Japan December 9th, 2012 by Azbil Corporation Personal Toru Yamaguchi, Yosuke Shinzawa
This paper presents overview of new extension of use of the Binary Voltage Divider (BVD) based on Cutkosky principle for fully automated maintenance of voltage scale at positive and also negative voltages at range from 1 mV to 1200 V.