The OPB350 series liquid sensor is designed to work with 3.2mm (1/8 inch) and 6.3mm (1/4 inch) outside diameter clear tubes. Used in conjunction with suitably designed output reference circuitry, output states such as "fluid present", "no fluid present" and "no tube present" can be recognised. Clear liquid present causes the phototransistor to sink the maximum current, while dark liquid present causes it to sink the minimum current. As bubbles pass through the tube, the signal will vary between the liquid present and no liquid states. If no liquid is present, the phototransistor sinks only a small amount of current. If no tube is present, the phototransistor sinks a larger current than in the no liquid state.

Opaque plastic housing enhances ambient light rejection
Lead length 610mm, 26 AWG wire
Applications: non-contact sensing of oils and other petroleum products, coloured fluids, toner fluids and water