| 摘要 |
PURPOSE:To install a space as a dead zone effectively by providing such a reflection wave wherein an ultrasonic beam refracts at a right angle to a radiation direction within its aerial propagation route. CONSTITUTION:A radiation ultrasonic beam 12 refracts roughly at a right angle to form an ultrasonic beam 7' which is made incident perpendicularly to a surf5. The ultrasonic beam 8' reflected from the surface 5 is refracted again roughly at a right angle by a reflection plate 11 to form a reflected ultrasonic beam 13 which propagates roughly in parallel to the surface 5 and is made incident to a photodetector 4' of a detecting probe 1'. In this case, the max. level of an object to be measured, that is, the distance up to the top edge of a pipe culvert 6 is installed at a distance equal to a dead zone via the plate 11 from a transmitter 3'. Then, the space 15 occupied by the culvert 6, the probe 1' and the plate 11 is sufficient if it is made slightly higher than a space 9 by a distance h3. |
