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For the 7-term SOLR calibration method to calibrate a four-sampler vector network analyser (VNA), the deviations of the seven error terms, as well as of the the measured S-parameters are determined due to the deviations of the reflections of the calibration elements (Short, Open and Load) from their true values. For the SOLR calibration, a reciprocal unknown network is used instead of a known Through...
A digital optical fiber current transformer (OCT) based on Rogowski coil and optical fiber transmission for use in high voltage systems is described in this paper. The technologies of signal sampling, processing and communication for the optical current transformer are introduced. The paper analyzes the present supply power techniques on high voltage side, and puts forward a new closed-loop regulating...
In the present study, we introduce a wideband calibration method of electric field strength sensors by using a gigahertz transverse electromagnetic (GTEM) cell and a reference electric field sensor. A preliminary comparison shows good agreement between the proposed method and other ones. Another measurement result will be presented at the conference.
A number of direct comparisons of Josephson Array Voltage Standards (JAVS) using Superconductor-Insulator-Superconductor (SIS) junction arrays have been performed at the National Metrology Centre (NMC), Singapore. The comparisons were performed over a range of voltage from 1 V to 10 V and with different combinations of array chips, both USA and German made. The comparisons used a parallel biasing...
This paper describes AC-DC current transfer difference measurement system in CMI which is able to measure AC-DC current differences from 3 mA up to 10 A in the frequency range 10 Hz - 10 kHz.
To solve the problem of channel-closing of multichannel comparator for heavy direct current, a new method is proposed that an air gap is set between every two channels in the DC comparator. This method fairly prevents the channels of multi-channel comparator from closing, and guarantees high precision measurement. By calculation, the comparator of four channels, with the total length of air gaps to...
This paper describes a compact, portable, high-precision voltage standard based on 1 V programmable Josephson array. The accuracy of the system is estimated to be better than 4 nV. The system can realize the fully automatic measurement of voltage reference, as well as its weight and volume are reduced. "In August, 2007 this system was carried to PTB, Germany to make a comparison. The difference...
A commercially available complete microprocessor controlled, fully automated 10 Volt Josephson voltage standard system was developed in cooperation between IPHT and Supracon. The system operates with an array of altogether 19,700 SIS Josephson tunnel junctions. A direct comparison between two such systems showed an uncertainty of 2 times 10-10. Furthermore, a novel cryocooler based system is described.
In high voltage testing there is a need to measure both the peak value and rms value of power frequency voltage. This paper describes method to calculate accurately both quantities; even when the frequency is not stable. The method can handle waveforms with harmonic content, and an uncertainty of few ppm can be achieved. Method is not sensitive to frequency fluctuation and phase lock loop is not needed.
Developed and approved in 2007 Secondary Standard of AC voltage scale transformation coefficient (VSTC) unit at primary rated voltages of 400 / radic3 kV and 500 / radic3 kV is described below.
A low DC current source based on the method of charging a capacitor using a linear voltage ramp was built for the calibration of picoammeters and the metrological features of the setup were tested. The measurement uncertainty was improved by offset current compensation and a galvanic isolation between the personal computer and the ramp generator via opto-coupling. Using this setup, a low-current meter...
A system for the precise measurement of electrical quantities by means of the rms value of ac voltages or currents is described. The system is implemented by a multijunction thermal converter and low cost electronic circuits. As a first application the system can both carry out ac voltage comparisons and ac and dc voltage measurements.
The configuration of a calibration system of digital recorder (digitizer) for HV impulse measurement is described. The system is developed based on Labview. Its calibration methods are according to IEC61083-1-2001, excepted for a fitting algorithm introduced in the determination of static non-linearity for digital recorder. The calibration system has been applied to the calibration of 8-bit and 300...
This paper describes some improvements to the accuracy of the on-site measuring system of the National Research Council of Canada (NRC) Travelling Standard Program. This NRC service provides traceable calibrations of the multifunction electrical standards that electrical utilities and other organizations use to test and verify electricity revenue meters. The calibration program can be used to show...
We have performed an experiment to drive an over-damped Josephson junction array (JJA) with modulated current pulse trains, which are generated by a modulated optical comb (an ultra-short pulse laser). The intensities of optical pulse trains are modulated using a pulse pattern generator. We quantitatively verified that the output voltages of the JJA were consistent with the modulation signals.
An overview of the development of a current-comparator-based high-voltage inductance bridge at the National Research Council of Canada (NRC) for the accurate measurements of load losses of large high voltage inductive loads at low power factor operating conditions, such as, large high voltage power transformers and shunt reactors, will be presented. The bridge has ratio uncertainties of less than...
We investigate the causes of the observed normal mode offsets in precision DMM's. With a circuit simulation tool to model the front-end amplifier we have been able to qualitatively reproduce the observed offset in a commonly used 8.5 digit precision DMM. In general the cause of the offset is related to the symmetry of the front-end architecture. However it seems there are several mechanisms which...
This paper describes a measurement set up based on a synchronous sampling system which allows the realization of the henry directly from the ohm and the second. This new set up improved the realization of the henry at METAS by a factor of 5. For the calibration of a 100 mH inductance standard at a frequency of 1 kHz, the expanded uncertainty amounts now to 15 muH/H.
A cryogenic noise source (CNS) cooled by liquid nitrogen (LN2) is constructed and evaluated in the frequency range of 8 GHz to 12 GHz (WR-90 waveguide band). A noise temperature of the CNS is changed from the boiling temperature of LN2 by a correction factor (CF) related to loss and temperature distribution of a transmission line (TL). We have investigated the CF by a sliding short method using a...
In this paper, theoretical calculation to related parameter of the counter-Helmholtz's coils is first processed, and experimentalized it later. It was found that time constant T is always fell short of destined target. Think over winding parameter and the correlative theoretical calculation is processed. Additionally, we improved experimental testing set. Here, the measured time constant is accorded...
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