| 摘要 |
PURPOSE:To easily adjust the resonance frequency of a sensor by applying a coating agent over the surface of piezoelectric ceramic. CONSTITUTION:The piezoelectric ceramic 29 which has an electrode formed on both surfaces is adhered to a diaphragm 26. The insulating coating agent 34 is applied over the surface of the ceramic 29 to adjust the resonance frequency. Then, a substrate 22 fitted to a connector unit 30 is inserted into a housing 20 and fixed to a step part 20A in the housing by entire-periphery ring projection welding. Then, an O ring 35 and a control plate 36 are inserted and the opening end of the housing 20 is curled inwardly to complete a knocking sensor. Thus, the resonance frequency of the sensor is easily adjusted.
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