Patent ID: 8919201

Claim:
An acceleration measuring apparatus comprising: a pendulum member, extending in a vertical direction, wherein an upper end of the pendulum member is supported; a piezoelectric resonator comprising a piezoelectric plate and a first drive electrode and a second drive electrode provided respectively on a first surface side and a second surface side of the piezoelectric plate in order to vibrate the piezoelectric plate; an oscillating circuit, configured to oscillate the piezoelectric resonator; a first movable electrode and a second movable electrode each respectively disposed on opposite surfaces of the pendulum member in a horizontal direction, configured to form variable capacitances; a first fixed electrode separated from the pendulum member, provided so as to oppose the first movable electrode, configured to form a first variable capacitance upon a change in capacitance between the first fixed electrode and the first movable electrode due to swinging of the pendulum member; a second fixed electrode separated from the pendulum member, provided so as to oppose the second movable electrode, configured to form a second variable capacitance upon a change in capacitance between the second fixed electrode and the second movable electrode due to swinging of the pendulum member; a switching unit, configured to alternately switch the connection of the first variable capacitance and the second variable capacitance with an oscillation loop comprising the oscillating circuit and the piezoelectric resonator; a frequency information detecting unit, configured to calculates frequency information corresponding to a difference between an oscillating frequency corresponding to the first variable capacitance and another oscillating frequency corresponding to the second variable capacitance that are time-divided by the switching unit; and an operating unit, configured to apply an external force to the pendulum member to immobilize the pendulum member in a reference position based on the frequency information detected by the frequency information detecting unit, the reference position is a stationary state in a vertical posture, and wherein an acceleration acting on a pendulum member is evaluated based on a size of the external force.