Project for Getting the Global Network of Magnetic Observatories to Take Part in the BIPM Unified System of Magnetic Induction Measurements
Earth and related Environmental sciences
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As is well known, the international community has founded BIPM in 1875 to ensure worldwide uniformity in units of measurements. In the beginning its activities were limited to measurements of length and mass. Later on, the Consultative Committees (CC) were set up, which were responsiblized with coordinating the international work in a number of the measurement fields, including the electrical measurements (CCE). In 1997, the CCE was transformed into the Consultative Committee for Electricity and Magnetism (CCEM) to embrace the magnetic measurements as well. Considering this, the D.I. Mendeleyev Institute for Metrology (VNIIM, Russia) suggested that CCEM should launch Key Comparisons (KC) of magnetic induction standards (MIS) in the geomagnetic range between 20 μT to 100 μT. The final objective is to set up a worldwide-recognized magnetic induction unit in the field where the most precise magnetic measurements are possible. The offer presumes the opportunity of participation in the KC not onldy of the National Metrology Institutes (NMI), but also the Geomagnetic Observatories (GO). The latter should then be nominated by the NMI as responsible for the KC from the given country, if a NMI in that country does not have the capabilities in this field of measurements. This offer was approved at the 22nd CCEM meeting (2000). However it has not been realized, because until now the Geophysical Community has not supported it. VNIIM has been working successfully on the absolute γp’ determination , establishing MIS , developing techniques for comparison of standards and ensuring the traceability from the base SI units. Comparisons provide conditions for highly stable and uniform field with the capability to reproduce the magnetic induction parameters at any point of the Earth surface. The systematic and random standard deviation of the total magnetic field reproduction is (0.01 – 0.03) nT and 0.002 nT, accordingly. Magnetic Observatories, as a result of their routine tasks, maintain MIS for the most part in the form of Reference Magnetometers. Some of them are also involved in testing and comparing magnetometers within the geomagnetic community. We suggest running a comparison campaign with 10-15 participating countries sending their standards to VNIIM, where all available magnetometers will be thoroughly compared against the VNIIM Standard. The result of this comparison will allow to assess and to implement the true MIS standards in order to carry out calibration of the scalar magnetometers belonging to Magnetic Observatories with the use of the definition standards, and in order to obtain the corrections and to determine the measurement uncertainties for each magnetometer. This corrective action could increase the accuracy, if the stability of the instruments were higher than the correction. Also, the magnetic observatories that carry out the tests of magnetometric instruments will obtain ISO9001 certification for their test sites.
CitationShifrin,V.Ya; Rasson, J.J. (2005). Project for Getting the Global Network of Magnetic Observatories to Take Part in the BIPM Unified System of Magnetic Induction Measurements. , Issue Proceedings of the XIth IAGA Workshop on Geomagnetic Observatory Instruments, Data Acquisition and Processing, Kakioka, Japan, November 9 - 17, 2004, 56, IRM,