External force detection sensor and external force detection equipment

An external force detection sensor, detecting an external force that acts on a piezoelectric piece, the external force detection sensor comprising:

• a piezoelectric piece that has one end side supported by a pedestal being formed in a crystal plane;
• one excitation electrode and another excitation electrode, the one excitation electrode being disposed at one surface side of the piezoelectric piece, the another excitation electrode being disposed at another surface side of the piezoelectric piece;
• an oscillation circuit electrically connected to the one excitation electrode;
• a movable electrode for forming variable capacitance disposed in a portion distant from the one end side of the piezoelectric piece, the movable electrode electrically connecting to the another excitation electrode;
• and
• a fixed electrode separated from the piezoelectric piece, the fixed electrode facing the movable electrode, the fixed electrode connecting to the oscillation circuit, the fixed electrode forming variable capacitance with variation in capacitance between the fixed electrode and the movable electrode, the variation in capacitance being caused by deflection of the piezoelectric piece, wherein
• an oscillation loop formed starting from the oscillation circuit and back to the oscillation circuit via the one excitation electrode, the another excitation electrode, the movable electrode, and the fixed electrode,
• the piezoelectric piece, the excitation electrode, the movable electrode, and the fixed electrode constitute combinations of a first combination and a second combination,
• the first combination constitutes a first sensor unit by disposing a first piezoelectric piece on a first crystal plane of the crystalline body, and
• the second combination constitutes a second sensor unit by disposing a second piezoelectric piece on a second crystal plane, the second crystal plane not opposite to the first crystal plane of the crystalline body, a relative position of the second crystal plane with respect to the first crystal plane being obtained.