Reflex level gauges allow the medium to be viewed through a reflex glass: the side of the glass which is exposed to the medium has a prismatic surface, while the other side is smooth. The medium level inside the level gauge is indicated as the result of the light refraction principle, since the liquid filled area completely absorbs the rays of light and appears dark, whereas the rays of light are totally reflected in the gas/air filled area which appears bright.
Reflex level gauges offer great advantages in terms of low purchase and maintenance costs, as well as easy level reading. Anyway, they cannot be used in certain cases, for example when the separation level between two liquids has to be read, when the observation of the liquid colour is required or when the fluid to be measured is high-pressure water steam.
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