Calibration procedure for triaxial magnetometers without a compensating system or moving parts

Precise Calibration Method for Triaxial Magnetometers Not Requiring Earth’s Field Compensation

“…The basic idea of the calibration has been described in [12]. A predefined sequence of currents is performed together with measuring the response of the calibrated triaxial magnetometer.…”

“…A predefined current sequence was applied during the calibration [12] (see Fig.5). The sequence contains current steps designed to have an significant influence on the calibrated magnetometer axes in each orthogonal direction and also to keep the magnetic field well in the magnetometer range The aim was to obtain a response at least 25 µT in each axis of the calibrated triaxial magnetometer.…”

“…The Earth's magnetic field is not cancelled by the coil system but its scalar value is remotely monitored. All input quantities (coil current, triaxial magnetometer output and the monitored Earth's field scalar value), forming N equations from N calibration steps where the magnetic field in the calibrating coils is changed in its amplitude and direction, are passed to a solver which solves the problem by the Levenberg-Marquardt non-linear optimization according to [12].…”

“…Based on an experience of [12], it was more suitable to approximately align the axes of the calibrated magnetometer with the respective calibrating coil axes because the non-linear solver converged faster. From the optimization described above, the sensitivity and two angles with respect to the orthogonal coil system have been obtained for each axis of the calibrated magnetometer.…”

“…a) The Overhauser magnetometer sensor placed in the triaxial coil system during calibration -a central position assures low field gradient, b) the coil pair oriented N-S, c) the coil pair oriented E-W d) the coil pair oriented verticallyfrom[12].…”