Reflex level gauges
Reading the liquid level in the gauge glass is performed by the naked eye, which is why it is important that the material is transparent, making the liquid level is visible. Reflex systems are based on reflecting light from a specially designed surface on the glass. In a gas or vapor phase, the light is 100% reflected off the prismatic grooves, whereas in the liquid phase, the light is absorbed, which to the eye will appear as a dark indication of the level.
