Azbil Model HPF-D27/HPF-D033 Contact-Type Liquid Level Fiber Unit Photoelectric Sensors all-resin structure ensures no metal contamination. 4mm diameter allows easy running of cables. Proprietary tip structure prevents liquid from clinging to the top, eliminating a cause of faulty operation. The lens built into the tip of the fiber ensures a significant difference in light quantity between the conditions when liquid is present, and liquid is absent. When used with an HPX-EG amplifier (sold separately), you can set sensitivity – easy setup done without the process liquid.