Acceleration sensor

An acceleration sensor including a vibrating body, comprising:

• a base fixed to a pedestal;
• a plurality of oscillating arms extended in parallel to each other from the base in a beam-like shape, oscillating transversally in a planar direction at a predetermined resonant frequency;
• and
• an added mass formed immediately adjacent the plurality of oscillating arms and having a mass equal to or larger than that of the base which couples the plurality of oscillating arms at distal ends thereof,
• the plurality of oscillating arms each including:
• at least one through hole opened through a thickness direction at a widthwise center of the oscillating arm, the through hole extending in a lengthwise direction thereof, and
• an excitation means for exciting the oscillating arms, the excitation means being provided in a range within an internal surface of the through hole and within both lateral surfaces of at least one of the plurality of oscillating arms, the range including at least a position where a deformation caused by an oscillation is large,
• the base and the oscillating arms including the added mass being monolithic, and
• the acceleration sensor detecting a resonant frequency variability of the vibrating body caused by an inertial effect of the added mass under acceleration,
• wherein the excitation means is formed at least adjacent a junction of the plurality of oscillating arms and the base, adjacent a junction of the plurality of oscillating arms and the added mass, and on an inside surface and both side surfaces of the oscillating arms at lengthwise centers of the plurality of oscillating arms.