Requirements for Obtaining High Accuracy with Proton Magnetometers Part 2
Gyromagnetic Constant The gyromagnetic constant relates the precession frequency and the magnetic induction or flux density. It is а real constant, i.e. the precession frequency of protons and the applied magnetic inductions are linearly related. Several institutions have been engaged in determination of the gyromagnetic constant: NIST (USA) National Institute of Standards and Technology formerly NBS NPL (UK) National Physical Laboratory VNIIM (Russia) Mendeleyew Institute of Metrology, St.Pеtеrsburg NIМ (China) National Institute of Metrology ASMW (former East Germany) Amt fur Standardisierung Messwesen and Wonenpufung, Berlin They came with their own results and accuracies, unfortunately often far apart from each other.…
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Requirements for Obtaining High Accuracy with Proton Magnetometers Part 1
Definition of Absolute Accuracy Absolute accuracy of a measurement is the difference between measured and true values. Obviously, nobody knows the true value, so we end up defining the limits we know the true value must be within. Presently the limits of accuracy of measurement of the magnetic field of the Earth can be pushed to better than 1ppm. In a field of, say, 50,000nT, this is better than 0.05nT. However, there are numerous difficulties and conditions that must be fulfilled to obtain that kind of absolute accuracy. Parameters that are involved include: • Gyromagnetic constant’s accuracy • Time reference…
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