Our Reflex Liquid Level Gauges are designed for precise measurement of the total liquid level of clean fluids in a vessel. They operate based on the difference in the refractive indices of the liquid and vapour, using a viewing glass made of toughened borosilicate glass with prismatic right-angled grooves on the side facing the liquid and vapour space

Light entering from outside the gauge is absorbed or reflected depending on whether it strikes the liquid or vapour space. When liquid is present, the glass appears black where it is in contact with the process medium. When no liquid is present, the glass appears silvery or white, allowing the observer to easily see the level of the fluid.