| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic wave sensor having high sensitivity and a high output at a low cost that solves problems such as effects of reverberation, effects of an external electromagnetic noise, impedance matching with air, and a noise caused by vibration laterally propagated. SOLUTION: The ultrasonic wave sensor is characterized in that a piezoelectric element on the major side of which an electrode is provided is fitted to an inner bottom face of a case made of a metallic thin plate material, the electrode of the piezoelectric element is connected to a connection terminal fitted to a base member that is air-tightly fixed to a circumferential part of an opening of the metallic case, an impedance matching layer made of a plastic material with glass balloons or glass beads intruded thereto is provided on an outer side face of the case opposed to the inner bottom face of the case to which the piezoelectric element is fitted, and a contraction tube suppressing vibration in a lateral direction from the piezoelectric element is provided on the side faces of the case and the matching layer.
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