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Ten years ago the international community started the expansion of the measurement range for ac-dc current transfer from 20 A to a present level of 100 A at frequencies up to 100 kHz with uncertainties of around 100 µA/A. At BEV coaxial current shunts based on resistive foils as well as low inductance tee connectors suitable to compare the shunts were fabricated [1]. This paper describes progress...
The dc performance of a widely-used high-accuracy commercial thermal transfer standard is found to be significantly affected by a variable contact resistance on its lower impedance ranges. This has a direct impact on the AC voltages measured by the instrument on these ranges. Cleaning the contacts and ensuring clearance around an input common mode choke effectively resolves the problem.
This paper gives a survey of the performance of existing current shunts designed by National Metrology Institutes (NMI's) around Europe. Key characteristics for power measurement; phase displacement, ac-dc transfer difference and power coefficient of the shunt resistance is reported for 5A, 50 A and 100 A shunts.
A comparison of the phase of existing shunts for currents between 10 A and 100 A and frequencies from 500 Hz to 100 kHz has been organized. The measurements were performed at INRIM using a first prototype of a new type of phase comparator and a step-up method for the data processing. The results of the relative measurements have shown a good repeatability, but the method for the evaluation of the...
Special tee connectors are necessary to calibrate ac-dc current shunts up to 100 A in a step-up procedure. Influences of these tees on the measured ac-dc difference have been observed. The reason for this influence is shown and a solution suggested, which reduces uncertainties in the 20 A to 100 A range and provides customers with calibration values free from tee influences.
The paper presents an international comparison of ac-dc current transfer measurements at 10 mA and frequencies up to 1 MHz. The standards of NMIA, PTB and BEV have already been compared. The comparison is currently being extended to involve SP. The results will be presented at the conference.
This paper describes the method used at BEV to determine the frequency dependence of thermal current converters at 10 mA in the frequency range 10 Hz to 1 MHz.
The paper describes a set of four cylindrical coaxial ac current shunts used as the new National Research Council of Canada (NRC) working standards in the frequency range up to 100 kHz. They were designed for currents from 20 to 100 A. At the lower current range, the shunts were compared to NRC coaxial shunts built from discrete resistors. At the higher current range, they were compared to the old...
The paper describes a set of four cylindrical, coaxial, ac current shunts used as the new National Research Council (NRC) working standards in the frequency range up to 100 kHz. They were designed for currents from 20 A to 100 A. At the lower current range the shunts were compared to NRC coaxial shunts built from discrete resistors. At the higher current range they were compared to the old working...
To expand the measurement capability up to 100 A at 100 kHz a construction for current shunts and Tee-connectors has been made, calculated and manufactured up to 40 A until now
The purpose of this work was (a) to develop an experimental set-up which is capable to record the time dependent temperature fluctuations of single junction thermal converters due to low-frequency ac currents by using an IR photo detector and (b) a characterisation of the local and temporal temperature behaviour of shunts for the ac current measurements with a thermocamera
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