ACCELERATION SENSOR AND MANUFACTURE OF SAID SENSOR

PURPOSE: To detect an acceleration both upward and downward in directions, while avoiding the bending of the resonator of a press load by disposing a flexible spring having symmetric structure, provided with upper and lower resonators in the center of a silicon platelet. CONSTITUTION: Structural parts for resonators 10, 11 are fabricated on the upper and lower sides 5, 6 of a silicon platelet 4. The range of a frame 2 and an oscillatory mass 3 is then masked, and a flexible spring 1 is manufactured by etching the platelet 4 and undercutting the structural part. When acceleration is generated in the vertical direction, the mass 3 is displaced. Consequently, a tensile load is generated in one of the resonators 10, 11, while a pressing load is generated in the other resonator, and the resonance frequencies of the resonators 10, 11 are varied. In the case of a tensile load, the frequency is a measure of the displacement of the mass 3, and thereby a measure of acceleration, and the acceleration can be detected. However in the case of a pressing load, the frequency is not a measure of acceleration. Since a symmetric structure is employed, one resonator can detect the acceleration without fail, while preventing the other pressing resonator from bending.