| 摘要 |
PURPOSE:To enhance general purpose property, by inputting a light signal from one light transmitting part, which is provided at the wall of a container enclosing liquid, and providing a light emitting element so that the signal can be received at the other light transmitting part, which is provided at the corresponding position when the liquid surface is lower than a reference level. CONSTITUTION:Light transmitting parts 2 and 3 are provided in the wall surfaces of a container. A light emitting element 4 and a light receiving element 5 having directivity are arranged so that light is received when liquid is not present on a light path. When the liquid is present on the light path, the light is not received because of the difference in refractive indexes of the liquid and air. By using this fact, the liquid level is detected. Namely, in the case of the liquid level 9, the light advances along the light path 7 due to the difference in the refractive indexes of the air and the liquid, and the light is not inputted to the light receiving element 5. When the liquid level is decreased to the position of the liquid level 8, the light directly advances along the light path 6, and the light input is given to the light receiving element 5. Based on the light input to the light receiving element 5, the liquid level, which is lower than the control level, is detected, and control valves 12 and 13 are operated. |
