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AC-DC current transfer step-up and step-down calibration and uncertainty calculation
Ist Teil von
IEEE transactions on instrumentation and measurement, 2002-10, Vol.51 (5), p.1027-1034
Ort / Verlag
New York: IEEE
Erscheinungsjahr
2002
Quelle
IEEE Electronic Library (IEL)
Beschreibungen/Notizen
New AC-DC current transfer standards are built for the current range from 0.3 mA to 20 A and the frequency range from 10 Hz to 100 kHz. A three-dimensional PTB-multijunction thermal converter (MJTC) with a heater resistance of 27 /spl Omega/ is the basic standard for the AC-DC current transfer at currents from 20 to 50 mA. At lower currents, planar MJTCs (PMJTCs) with heater resistances from 90 to 960 /spl Omega/ are used in a step-down procedure. Coaxial current shunts in parallel with PMJTCs extend the current range up to 20 A. The standard measurement uncertainties are in the range from 0.2 /spl mu/A/A at 25 mA and 1 kHz to 50 /spl mu/A/A at 20 A and 100 kHz. The high sensitivity of the PMJTC allows bigger steps in the step-up calibration and some smaller steps between these steps. Calibration of all these steps leads to an overdetermined system to check for the validity of the assumptions made in the step-up procedure. This results in reduced uncertainties at the different current levels compared to the old method.