| 摘要 |
PURPOSE:To achieve a stable detection of a liquid level for a long time, by arranging a light emitting element, a light shielding plate and a light receiving element on both external sides of a double-structured container to detect intensity of light between both the elements. CONSTITUTION:Water 8 is poured between an outer container 1 and an inner container 2 while the container 2 is filled with a liquid source 7 and a light emitting element 3 and a projection lens 4 are provided outside a window 17 while a light shielding plate 11, a condensing lens 10 and a light receiving element 5 are provided outside a window 18. Then, the position of the lens 4 is adjusted beforehand so that with a liquid surface of the source 7 above a detection level, outgoing light of the element 3 is condensed on the light shielding plate 11, which makes the quantity of light received of the element 5 very weak. Under such a condition, when the liquid surface of the source 7 falls below the detection level, an outgoing luminous flux to the element 5 is diffused and incident on the element 5 without being intercepted with the light shielding plate 11. Thus, a liquid level can be detected from a change in the quantity of light received of the element 5 depending upon whether the liquid source is above or below the detection level. Moreover, as a change in the intensity of a transmission light of the container 2 is detected, the quantity of light received of the element 5 will not be affected regardless of a slight deviation of the position of the container 2 to the right or left; thereby, a detection accuracy stable for a long time can be obtained. |
