| 摘要 |
PURPOSE:To detect the presence or absence and the amount of fluid in a closed container automatically by inputting ultrasonic waves orthogonally with respect to the wall of the container, and detecting the attenuating rates of the multiple reflected echoes of the ultrasonic waves which are reflected from the inner surface of the all of the container. CONSTITUTION:Ultrasonic waves are sequentially projected orthogonally on the surface of the outer wall of a casing 1 from ultrasonic wave probes 2a - 2c which are in contact with the surface of the outer wall of the casing 1. Then parts of the waves are reflected from the surface of the inner wall of the casing 1 and returned to the probes 2a - 2c are primary reflected echoes. Parts of the ultrasonic waves are sequentially reflected from the outer wall surface and to the inner wall surface and returned as the secondary echoes. Similarly, the reflected echoes up to the nth order are returned. When said multiple reflected echoes are transduced into electric signals, the signals are divided into two patterns. That is, when the liquid level is higher than the incident position of the ultrasonic waves parts of the ultrasonic waves reaching the inner wall surface are absorbed into liquid. Therefore, the attenuating rate of the multiple reflected echoes is large. When the liquid level is lower than the incident position, the attenuating rate becomes small. Therefore, when the two kinds of said patterns are judged, whether the liquid is filled to the incident position of the ultrasonic waves or not can be found. |
