The working principle of this level glass type is based on the different light refractive index as passes from glass to a liquid or from glass to a gas.


The glasses used have, on the side in touch with fluid, many right angle grooves.
In this way when the inner side is filled with a liquid, the incident light beam is refracted inward and entirely absorbed.
On the contrary the light beam is totally reflected when meets a gas.
In this manner the observer can see:
- Blake zone corresponding to the liquid level.
- Silvery zone where level glass is not filled by liquid.
So the liquid level is clearly shown, independently of the liquid nature and color.
In view of this plain operation this type of level glasses are recommended by their low purchase and operating cost and by their easy reading in every environmental condition.
Reflex level glasses are not suited when is necessary to visualize:
a). the liquid colored
b). the interface between liquids
c). the fluid level when the gaseous substance is high pressure steam

* Zoekterm: tubular, transparant, reflex level indicator