External force detecting device and external force detecting sensor

摘要

An external force detecting device capable of accurately and easily detecting external force applied to a piezoelectric piece is provided. A crystal piece 2 is cantilever-supported in a container 1. Excitation electrodes 31, 41 are formed on an upper face and lower face, respectively, for example in a center portion of the crystal piece 2. On a front end portion of a lower face side of the crystal piece 2, a movable electrode 5 connected via a lead-out electrode 42 to the excitation electrode 41 is formed on the lower face side, and a fixed electrode 6 is provided on a bottom portion of the container 1 to face this movable electrode 5. The excitation electrode 31 on the upper face side and the fixed electrode 6 are connected to an oscillation circuit 14. When the crystal piece 2 bends by external force applied, capacitance between the movable electrode 5 and fixed electrode 6 changes, and this capacitance change is regarded as a change in oscillation frequency of the crystal piece.