| 摘要 |
PROBLEM TO BE SOLVED: To attain chemical resistance and sound wave conversion over a wide temperature range by providing a sensor element for ultrasonic transmission/receiving, a matching layer surrounding the sensor element, and a clamp ring surrounding the matching layer and a stress equalization layer, all encased in a casing, and an attenuation layer arranged in the remaining hollow space in the casing. SOLUTION: A hollow cylindrical body 11 is sealed with a diaphragm 12 and a casing 1 is made of a chemical resistant thermosetting plastic. A pulse oscillation is excited in the sensor element 2 arranged in the casing 1 by an electronic circuit. In order to match the acoustic impedance of element 2 with the acoustic AC resistance of a medium being irradiated with an ultrasonic pulse, a matching layer 3 is interposed between the element 2 and diaphragm 12. Since the diaphragm 12 has a coefficient of thermal expansion higher than that of the layer 3, a stress is generated and transmitted through the layer 3 to the element 2. Consequently, the element 2 is subjected to a pressure load under high temperature and tensile stress under low temperature. A stress equalization layer 5 protects the element 2 against stress. |
