Fluid Sensor - Tube Style (OPB350 series)

TT Electronics
Part Number Information
Part #: Price/Availability:
OPB350 Buy Now

The OPB350 series liquid sensor is designed to work with 1/16” [1.6mm] 1/8” [3.2mm], 3/16” [4.8 mm] and 1/4” [6.3 mm] outside diameter clear tubes. When output reference circuitry is added, multiple output states such as “fluid present,” “no fluid present” and “no tube present” can be recognized.

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 tube is present, the phototransistor sinks current between the dark fluid and clear Fluid states. The customer will have to identify the typical current values for each situation. The ratio between the different stated allows acknowledgment of different conditions.


  • Can identify if liquid is present in clear tubes that have an outside diameter of 1/16” [1.6mm], 1/8" [3.2mm], 3/16" [4.8 mm] or 1/4" [6.3 mm]
  • Opaque plastic housing enhances ambient light rejection
  • Printed circuit board mounting or 24” (610 mm) 26 AWG wires


  • Non-contact fluid sensing including
    • IV fluid
    • Oils and other petroleum products
    • Colored fluids
    • Toner fluids
    • Water