Temperature compensated permanent magnet/moving coil accelerometer
First Claim
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1. A temperature compensated accelerometer comprising:
- a housing;
permanent magnet means mounted in said housing for producing a magnetic field in a defined region;
a mass having a coil thereon lying in a plane perpendicular to a central axis of the coil;
a suspension system for mounting said mass so that said coil is positioned in the defined region with the axis of the coil transverse to the direction of magnetic field, said suspension system permitting movement of said mass relative to said housing;
position sensing means for producing a position signal indicative of displacement of said mass from a predetermined position relative to said housing;
servo amplifier means for producing a rebalance current in response to the position signal;
electrical conductor means for supplying the rebalance current to said coil, whereby said mass is maintained in the predetermined position;
a temperature sensing winding for producing a temperature signal indicative of the temperature of said permanent magnet means;
an auxillary winding associated with said permanent magnet means for augmenting the magnetic field produced in the defined region;
a differential amplifier having inverting and noninverting input terminals and an output terminal;
means for connecting said auxillary and temperature sensing windings in series in a negative feedback circuit between the output and inverting input terminals of said differential amplifier; and
biasing means for supplying biasing voltages to the inverting and noninverting input terminals of said differential amplifier.
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Abstract
A temperature compensated accelerometer of the type having a permanent magnet, moving coil rebalance system is disclosed. A cylindrical permanent magnet and surrounding sleeve produce radial magnetic fields in annular regions in which are located rebalance coils on a suspended bobbin. A noninductive temperature sensing winding on the magnet is connected in a bridge input circuit to an amplifier which produces a current in an auxillary winding for augmenting the fields produced by the permanent magnet so as to maintain constant magnetic field strength in the annular regions.
13 Citations
10 Claims
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1. A temperature compensated accelerometer comprising:
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a housing; permanent magnet means mounted in said housing for producing a magnetic field in a defined region; a mass having a coil thereon lying in a plane perpendicular to a central axis of the coil; a suspension system for mounting said mass so that said coil is positioned in the defined region with the axis of the coil transverse to the direction of magnetic field, said suspension system permitting movement of said mass relative to said housing; position sensing means for producing a position signal indicative of displacement of said mass from a predetermined position relative to said housing; servo amplifier means for producing a rebalance current in response to the position signal; electrical conductor means for supplying the rebalance current to said coil, whereby said mass is maintained in the predetermined position; a temperature sensing winding for producing a temperature signal indicative of the temperature of said permanent magnet means; an auxillary winding associated with said permanent magnet means for augmenting the magnetic field produced in the defined region; a differential amplifier having inverting and noninverting input terminals and an output terminal; means for connecting said auxillary and temperature sensing windings in series in a negative feedback circuit between the output and inverting input terminals of said differential amplifier; and biasing means for supplying biasing voltages to the inverting and noninverting input terminals of said differential amplifier. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In acceleration responsive apparatus of the type including permanent magnet means for producing a magnetic field in which is located a coil forming at least a portion of a mass suspended for movement relative to the magnet means, a servo system for supplying current to the coil to maintain the mass in a predetermined position relative to the magnet means and pickoff means for supplying a signal indicative of displacement of the mass from the predetermined position, temperature compensation means for minimizing nonlinearities in response resulting from changes in permeability of the magnet means with changes in temperature, comprising:
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a temperature sensing winding for producing a temperature signal indicative of the temperature of said permanent magnet means; an auxillary winding associated with said permanent magnet means for augmenting the magnetic field produced by said permanent magnet means; a differential amplifier having inverting and noninverting input terminals and an output terminal; means for connecting said auxillary and temperature sensing windings in series in a negative feedback circuit between the output and inverting input terminals of said differential amplifier; and biasing means for supplying biasing voltages to the inverting and noninverting input terminals of said differential amplifier. - View Dependent Claims (8, 9, 10)
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Specification