Hung mass accelerometer with differential Eddy current sensing

摘要

A new class of accelerometer uses a differential Eddy current sensor to sense the displacement of the proof mass. This accelerometer can provide improved performance in an open-loop configuration based on the thermal stability and improved linearity of the differential Eddy current sensor. The accelerometer may provide lower cost alternatives to commercial grade accelerometers and lower cost and higher reliability alternatives to strategic grade accelerometers.

主权项

1. A hung mass accelerometer, comprising:
a body having an internal cavity; a first flexure attached to the body inside the internal cavity, said first flexure compliant along a linear axis; a proof mass attached to the first flexure to hang inside the internal cavity, said proof mass allowed to move in-line with the first flexure along the linear axis in an open-loop configuration; an oscillator that generates an alternating drive signal; first and second sensor heads positioned on the body inside the internal cavity on opposite sides of the proof mass at distances d1 and d2 that increase and decrease in opposition as said proof mass moves along the linear axis, each said sensor head having a reference coil responsive to the alternating drive signal to produce a primary oscillating magnetic field that induces Eddy currents in the proof mass that create an opposing secondary magnetic field that resists the primary magnetic field generated by the reference coil, any change in the distance between the reference coil and the proof mass causing a change in the magnetic field interaction that alters an output signal; and a first electrical circuit configured to compare the output signals from the first and second sensor heads to provide an output proportional to the displacement of the proof mass along the linear axis; and a second electrical circuit configured to convert the output to a measured acceleration of the body knowing the mass of the proof mass and the stiffness of the flexure.