| 摘要 |
PURPOSE:To make it possible to detect fine particles contained in a liquid by enhancing electricity-sound converting efficiency, in a sensor for counting the number of fine particles such as dust or bacteria present in the liquid such as water, by allowing an ultrasonic vibrator to expose to a liquid flowing part. CONSTITUTION:An 1/4 wavelength plate 5 is applied to an ultrasonic vibrator 1 having a concave surface and a packing material 4 for absorbing an ultrasonic wave is further provided to the rear surface of said ultrasonic vibrator 1. In this case, the surface of the 1/4 wavelength plate 5 is pierced through the wall surface of an arranged pipe material 3 so as to be exposed to a liquid flowing part. When a sonic wave is emitted from the ultrasonic vibrator 1, it is directly emitted to the liquid flowing part without being attenuated in the material of said arranged pipe material 3 and reflected sounds from fine particles increase. Because the ultrasonic vibrator 1 coated with the 1/4 wavelength plate 5 is exposed to the liquid flowing part, the attenuation element of the reflected sonic wave is eliminated and sound-electricity converting efficiency becomes high and the detection of fine particles in a liquid is enabled. |
