Servo accelerometer with tunnel current sensor and complementary electrostatic drive
First Claim
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1. An accelerometer comprising:
- position sensing means including a tunnel current sensor forsensing a displaced position of a proof mass from a servo null position and for generating a position sensing signal indicative of said displaced position;
means responsive to said position sensing signal for providing an output signal indicative of sensed acceleration;
electrostatic drive means for generating first and second electrostatic forces on said proof mass for returning said proof mass from said displaced position to said servo null position, said first electrostatic force being opposite in direction to said second electrostatic force;
a frame having first and second surfaces;
elastic connecting means for elastically connecting said proof mass to said frame;
a first cover plate sealingly engaging said first surface;
a second cover plate sealingly engaging said second surface opposite said first surface;
said first and second cover plates and said frame defining a chamber in which said proof mass is disposed; and
a damping fluid disposed in said chamber.
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Abstract
A servo accelerometer uses a tunnel current sensor having a first sensing electrode coupled in fixed alignment with a frame and a second sensing electrode coupled to a proof mass. A position sensing circuit develops a sensing signal indicative of displacement of the proof mass. A feedback circuit provides an output signal and provides a feedback signal to electrostatic drive electrodes for applying an electrostatic repositioning force to the proof mass. The proof mass and frame are connected by a highly compliant suspension structure.
52 Citations
45 Claims
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1. An accelerometer comprising:
- position sensing means including a tunnel current sensor for
sensing a displaced position of a proof mass from a servo null position and for generating a position sensing signal indicative of said displaced position; means responsive to said position sensing signal for providing an output signal indicative of sensed acceleration; electrostatic drive means for generating first and second electrostatic forces on said proof mass for returning said proof mass from said displaced position to said servo null position, said first electrostatic force being opposite in direction to said second electrostatic force; a frame having first and second surfaces; elastic connecting means for elastically connecting said proof mass to said frame; a first cover plate sealingly engaging said first surface; a second cover plate sealingly engaging said second surface opposite said first surface; said first and second cover plates and said frame defining a chamber in which said proof mass is disposed; and a damping fluid disposed in said chamber. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
- position sensing means including a tunnel current sensor for
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18. An accelerometer comprising:
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proof mass; a frame having first and second surfaces; elastic connecting means for elastically connecting said proof mass to said frame; a tunnel current sensor disposed to generate a tunnel current, the magnitude of said tunnel current being indicative of the relative position of said frame and said proof mass; a position sensing circuit connected to supply a voltage potential to said tunnel current sensor and for generating a position sensing signal from said tunnel current, said position sensing signal corresponding to a displaced position of said proof mass from a servo null position with respect to said frame; a drive circuit for generating drive voltages in response to said position sensing signal and for generating an output signal indicative of sensed acceleration; a plurality of drive electrodes disposed to provide oppositely directed electrostatic forces on said proof mass to urge said proof mass from said displaced position to said servo null position in response to said drive voltages; a first cover plate sealingly engaging said first surface of said frame; a second cover plate sealingly engaging said second surface opposite said first surface of said frame; said first and second cover plates and said frame defining a chamber in which said proof mass is disposed; and a damping fluid disposed in said chamber. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
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Specification