Active magnetic field compensation system using a single filter

摘要

The present invention provides a magnetic compensation system and a method of utilizing a magnetic compensation system to neutralize magnetic fields in an environment of a magnetically sensitive instrument. A magnetometer is used to sense magnetic field components in the environment and convert them into a signal. The signal is filtered to remove frequency components associated with the resonant frequency of the compensation system. The filtered signal is amplified by a signal amplifier and amplified by a power amplifier to generate current to drive a semi-Helmholtz coil disposed in the environment of the instrument. Magnetic fields are produced by the semi-Helmholtz coil which neutralize the sensed magnetic fields. The filter may be implemented using either a low-pass filter or a notch filter with notch frequencies set to the resonant frequency and harmonics thereof. The cut-off frequency of the low pass filter or the notch frequencies of the notch filter are selected so that the open loop gain of the compensation system is less than about 1 at the resonant frequency. The compensation system components are selected to maximize the resonant frequency and reduce circuit delay.