Stress-relieved amorphous metal ribbon magnetometer having viscous fluid interface
First Claim
1. A magnetometer for detecting an applied magnetic field comprising:
- a magnetostrictive element having a longitudinal axis extending between opposing ends of the element;
means for supporting the element so that the element is free to vibrate longitudinally, said supporting means including a piezoelectric driver;
means for applying an oscillating electrical driving signal to the driver such that the driver applies an oscillating dither stress to the element which induces magnetization fluctuations along the longitudinal axis of the element of a magnitude proportional to the strength of an applied magnetic field;
means operated on by the magnetization fluctuations for producing an oscillating electrical measuring signal corresponding thereto;
means for detecting the measuring signal; and
a viscous fluid disposed between the magnetostrictive element and the supporting means for reducing the transmission of stresses at a frequency substantially below that of the driving signal which stresses introduce low-frequency noise and change the calibration by changing the piezomagnetic modulus of the element.
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Accused Products
Abstract
A highly-sensitive, physically small and rugged magnetometer employs a magnetostrictive amorphous metal ribbon core. A piezoelectric driver induces stress variations in the ribbon of a magnitude determined by an external magnetic field. The amplitude of the variations in magnetization is sensed by a pick-up winding disposed around the ribbon core. The dynamic range of the device is improved by employing a nulling field winding around the core to continuously null out the magnetization of the core. In contrast to the non-linear characteristic of the conventional fluxgate magnetometer, the invention provides a linear response to magnetic field strength which simplifies the processing circuitry. In addition, the ribbon may be field-annealed to improve the sensitivity of the device. Still further, low-frequency stresses in the ribbon (due to thermal expansion and the like) are relieved with a viscous fluid interface between the ribbon and support to thereby reduce low-frequency noise in the output signal and drifts in the calibration.
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Citations
23 Claims
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1. A magnetometer for detecting an applied magnetic field comprising:
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a magnetostrictive element having a longitudinal axis extending between opposing ends of the element; means for supporting the element so that the element is free to vibrate longitudinally, said supporting means including a piezoelectric driver; means for applying an oscillating electrical driving signal to the driver such that the driver applies an oscillating dither stress to the element which induces magnetization fluctuations along the longitudinal axis of the element of a magnitude proportional to the strength of an applied magnetic field; means operated on by the magnetization fluctuations for producing an oscillating electrical measuring signal corresponding thereto; means for detecting the measuring signal; and a viscous fluid disposed between the magnetostrictive element and the supporting means for reducing the transmission of stresses at a frequency substantially below that of the driving signal which stresses introduce low-frequency noise and change the calibration by changing the piezomagnetic modulus of the element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A magnetometer for detecting an applied tic field comprising:
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a magnetostrictive element comprising a ribbon of an amorphous metal, said ribbon having a longitudinal axis extending between opposing ends; a piezoelectric driver; a rigid supporting means; means for attaching the ribbon at opposing ends to the driver and supporting means; means for applying an oscillating electrical driving signal to the driver such that the driver applies an oscillating dither stress to the ribbon which induces magnetization fluctuations in the ribbon of a magnitude proportional to the strength of the applied magnetic field; a pick-up coil surrounding the ribbon along the longitudinal axis thereof wherein tho magnetization fluctuations in the ribbon induce an electroactive force (emf) in the pick-up coil; and means for detecting the emf in the pick-up coil for producing an output signal proportional to the applied magnetic field; and a viscous fluid disposed between at least one of the interfaces of the supporting means and ribbon and the driver and ribbon for reducing the transmission of stresses at a noise frequency substantially below that of the driving signal which stresses introduce low-frequency noise and change the calibration by changing the piezomagnetic modulus of the ribbon. - View Dependent Claims (20)
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21. A magnetometer for detecting an applied magnetic field comprising:
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a piezoelectric substrate; a magnetostrictive element comprising a ribbon of an amorphous metal disposed adjacent one surface of the substrate, said ribbon having a longitudinal axis; means for applying an oscillating electrical driving signal to the substrate such that the substrate applies an oscillating dither stress to the ribbon which induces magnetization fluctuations in the ribbon of a magnitude proportional to the strength of the applied magnetic field; a pick-up coil surrounding the substrate and ribbon along the longitudinal axis thereof wherein the magnetization fluctuations in the ribbon induce an electromotive force (emf) in the pick-up coil; means for detecting the emf in the pick-up coil for producing an output signal proportional to the applied magnetic field; and a viscous fluid disposed between the substrate and ribbon for reducing the transmission of stresses at a noise frequency substantially below that of the driving signal which stresses introduce low-frequency noise and change the calibration by changing the piezomagnetic modulus of the ribbon. - View Dependent Claims (22, 23)
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Specification