Accelerometer including an overall arrangement for reducing temperature related errors

Claim 1

In a pendulous type of accelerometer apparatus, a closed housing, a magnetic circuit arrangement located within said housing for the purpose of providing a magnetic field having a given constant flux density in a given area within said housing, means including a pendulous member mounted for pivotal movement within said housing and having a current carrying torque coil located within and responsive to said magnetic field for producing an electrical output signal corresponding to the acceleration to which said apparatus is subjected, said magnetic circuit arrangement containing temperature sensitive magnetic material which is sufficient to cause the flux density within said magnetic field to vary inversely with changes in temperature within said closed housing and thereby introduce a temperature related error into said electrical output signal such that the latter does not correspond to said acceleration, and temperature compensating means for reducing said temperature related error, said compensating means including means for reducing the amount of change in flux density of said magnetic field as a result of said temperature changes so as to provide said temperature related error reduction said change in flux density reducing means including flux leakage means located within said housing and acting on said magnetic circuit arrangement for causing a constant amount of flux to leak from said magnetic field when the latter displays said given flux density at a corresponding temperature within said chamber, said flux leakage means varying the amount of flux which leaks from said field in response to and inversely with said temperature changes for providing said reduction in the amount of change in flux density of said magnetic field caused by said temperature changes, said flux leakage means including a flux conductive plate-like member located in spaced relationship with said magnetic circuit arrangement, and means supporting said member such that the spacing between the latter and said magnetic circuit arrangement varies directly with said temperature changes so as to provide said varying amount of flux leakage, said plate-like member and supporting means together forming a bellows which expands with decreases in said temperature changes and contracts with increases in said temperature changes, said housing being a sealed housing containing oil which surrounds said pendulous member, magnetic circuit arrangement and said bellows, said oil being of a type which changes in volume directly with said temperature changes, said bellows expanding with and as a result of decreases in said oil volume and contracting with and as a result of increases in said oil volume whereby to provide said spacing variation and to compensate for said changes in volume.