Level Gauges

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.