| 摘要 |
<p>A water level gauge comprises a column (10) for containing water, a plurality of light sources (14) on one side of the column and a plurality of detector assemblies (28) on an opposite side of the column. Filters (16) are utilised to project red and green light through the column (10). Each detector assembly (28) includes a red detector (30) and a green detector (32) with red and green filters (26, 24), respectively. Due to the difference in offset of light beams transversing the column at an oblique angle through water and through air, the green detector (32) is activated by green light when the green and red light passes through the water in the column and the red detector (30) is activated when the light passes through air in the column, that is, above the water level (20) in the column. By means of a circuit connected to each detector assembly (28), it is possible to discover the level (20) of water in the column (101.</p> |
