Patent ID: 9016128
Filing Date: 2015-04-28
Classification: G01L,G01P

Abstract:
1. An external force detecting method using a sensor comprising: a cantilever piezoelectric plate supported at one end on a base; one excitation electrode and another excitation electrode provided on a portion less than an entirety of one face side and a portion less than an entirety of another face side, respectively, of the piezoelectric plate so as to vibrate this piezoelectric plate; an oscillation circuit connected electrically to the one excitation electrode; a movable electrode for forming variable capacitor provided in a portion separated from the one end side on the piezoelectric plate and connected electrically to the other excitation electrode; and a fixed electrode provided separately from the piezoelectric plate to face the movable electrode and connected to the oscillation circuit, where capacitance between the fixed electrode and the movable electrode is changed by bending of the piezoelectric plate to thereby form a variable capacitor; and wherein the movable electrode is provided at the other end of the piezoelectric piece at a greater distance than the one excitation electrode and the other excitation electrode; the method comprising the steps of: setting the sensor so that an angle formed between a face orthogonal to a direction of external force as an intended subject of measurement and a length direction of the piezoelectric plate in the movable electrode is 30° to 60°; detecting a signal as frequency information corresponding to an oscillation frequency of the oscillation circuit by a frequency information detecting unit; and finding the magnitude of the external force acting on the piezoelectric plate on the basis of the difference between the frequency detected with the frequency information detecting unit when an external force that is the subject of measurement is not applied to the piezoelectric plate, and the frequency detected with the frequency information detecting unit when an external force that is the subject of measurement is applied to the piezoelectric plate.