| 摘要 |
PURPOSE:To facilitate remote measurement, by making an optical beam incident to a cylindrical gauge tube so that the optical beam is orthogonal to the axis of the tube and is oblique to the wall of the tube and discriminating whether the beam after passage of the tube is detected by a photodetector or not to detect the presence or the absence of a liquid. CONSTITUTION:A gauge tube 1 is made of a transparent solid such as a transparent quartz, various kinds of glass, or the like which is not affected chemically by an object liquid 4. When the wall of the tube is thick, the influence upon the optical path is almost eliminated. If the liquid does not exist in the tube and is filled up with air, the optical path is a straight line approximately, and the light can be detected by a light receiving part 3. If the liquid 4, for example, water exists in the tube, the optical path is bent, and the light is not detected by the light receiving part 3. The device is so formed that a considerably large angle of incidence is formed between the incidence direction of the beam and the normal to the wall of the tube at the point where the optical beam is made incident to the gauge tube. |
