| 摘要 |
For liquid storage tanks, a level indicator is provided for making the level of the tank contents easily visible once the liquid level in the tank has fallen below a certain amount. The object is achieved according to the invention in that tank wall includes a prism placed in the area of an inspection aperture. The prism on which incident light coming through openings in the inspection aperture reflects the light back toward an observer or absorbs the light in the liquid in the tank. Therefore, when the liquid level is as high as the prism the prism appears bright, or illuminated, and when the liquid level is below the level of the prism the prism appears darker.
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