Active magnetic field compensation system using a single filter
First Claim
1. A magnetic compensation system having a predetermined resonant frequency and being adapted for use with a magnetically sensitive instrument comprising:
- a sensor for sensing magnetic fields in an environment of said magnetically sensitive instrument;
a transducer means coupled to said sensor for generating a signal having frequency components associated with said magnetic fields sensed by said sensor;
a filter coupled to an output of said transducer means for filtering said signal to substantially eliminate frequency components associated with said resonant frequency to define a compensating signal; and
a compensation coil disposed in the environment of said magnetically sensitive instrument and being operatively coupled to an output of said filter, said compensation coil producing neutralizing magnetic fields based on said compensating signal to effectively neutralize said sensed magnetic fields.
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Abstract
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.
24 Citations
25 Claims
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1. A magnetic compensation system having a predetermined resonant frequency and being adapted for use with a magnetically sensitive instrument comprising:
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a sensor for sensing magnetic fields in an environment of said magnetically sensitive instrument; a transducer means coupled to said sensor for generating a signal having frequency components associated with said magnetic fields sensed by said sensor; a filter coupled to an output of said transducer means for filtering said signal to substantially eliminate frequency components associated with said resonant frequency to define a compensating signal; and a compensation coil disposed in the environment of said magnetically sensitive instrument and being operatively coupled to an output of said filter, said compensation coil producing neutralizing magnetic fields based on said compensating signal to effectively neutralize said sensed magnetic fields. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of utilizing a magnetic compensation system having a predetermined resonant frequency to neutralize magnetic fields in an environment of a magnetically sensitive instrument, comprising the steps of:
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sensing magnetic fields in the environment of said magnetically sensitive instrument; generating a signal based on said sensed magnetic fields; filtering said signal to substantially eliminate frequency components associated with said resonant frequency to define a compensating signal; and producing neutralizing magnetic fields in said environment based on said compensating signal to effectively neutralize said sensed magnetic fields. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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22. A magnetic compensation system having a predetermined resonant frequency and being adapted for use with a magnetically sensitive instrument comprising:
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a sensor for sensing magnetic fields in an environment of said magnetically sensitive instrument; a transducer means coupled to said sensor for generating a signal having frequency components associated with said magnetic fields so sensed; a filter coupled to an output of said transducer means for filtering said signal to substantially eliminate frequency components associated with said resonant frequency to define a compensating signal; a compensation coil disposed in the environment of said magnetically sensitive instrument and being operatively coupled to said filter, said compensation coil producing neutralizing magnetic fields based on said compensating signal to effectively neutralize said magnetic fields so sensed; and said sensor, transducer means, filter, and compensation coil being designed to substantially maximize said resonant frequency and minimize circuit delay of said compensation system. - View Dependent Claims (23, 24, 25)
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Specification