×

Accelerometer using pulse-on-demand control

  • US 5,473,946 A
  • Filed: 09/09/1994
  • Issued: 12/12/1995
  • Est. Priority Date: 09/09/1994
  • Status: Expired due to Term
First Claim
Patent Images

1. An accelerometer system, comprising:

  • first and second conductive plates in a fixed spatial relationship;

    a first switch for selectively connecting the first plate to a fixed positive potential and to ground;

    a second switch for selectively connecting the second plate to a fixed negative potential and to ground;

    a conductive pendulum resiliently suspended between the first and second plates and responsive to sensed inertial acceleration inputs by moving toward one or the other of the first and second plates from a predetermined null position;

    a third switch for selectively connecting the pendulum to a high impedance and to at least one predetermined fixed potential, including ground, to which each of the first and second plates can be connected;

    a microprocessor, responsive to a force-indicative signal, and having a clock that establishes a cycle period, and producing (a) a first control signal indicative of first, second, and third time intervals within the cycle period; and

    (b) a second control signal;

    switch control means, responsive to the first and second control signals, for (a) actuating the first switch to connect the first plate to the fixed positive potential and actuating the second switch to connect the second plate to the fixed negative potential at the beginning of the first time interval, and actuating the third switch to connect the pendulum to the high impedance at or shortly before the beginning of the first time interval;

    (b) actuating the third switch and a selected one of the first and second switches to connect the pendulum and a selected one of the plates, selected in response to the second control signal, to one predetermined fixed potential, no later than the beginning of the second time interval;

    (c) actuating the previously unselected one of the first and second switches to connect the previously unselected plate to ground at the beginning of the third time interval; and

    (d) if the one predetermined fixed potential is other than ground, actuating the third switch to connect the pendulum to ground at the beginning of the third time interval; and

    signal generating means, electrically coupled to the pendulum and responsive to the voltage on the pendulum during the first time interval, when the first plate is connected to the fixed positive potential, the second plate is connected to the fixed negative potential, and the pendulum is connected to the high impedance, wherein the pendulum voltage is indicative of the acceleration-responsive displacement of the pendulum from the null position, the signal generating means producing the force-indicative signal indicative of the force required to restore the pendulum to the null position;

    wherein the microprocessor is responsive to the force-indicative signal by (a) generating the second control signal in response to the sign of the force-indicative signal, and (b) varying the length of the second time interval in proportion to the magnitude of the force-indicative signal, whereby the length of the second time interval is indicative of the sensed acceleration input.

View all claims
  • 2 Assignments
Timeline View
Assignment View
    ×
    ×