Fluid Sensors (OCB350 series)

TT Electronics
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The OCB350 Series is a fluid sensor with self-calibration circuitry that requires only an optical device and power supply for operation. Like the original OPB350 Series sensors, these devices use an LED/phototransistor to sense the change in refractive properties between full and empty tubing as it passes through the sensor housing, creating multiple output states such as "fluid present," "no fluid present," and "no tube present."

Click hereThe OCB350 Series liquid sensor consists of an LED and phototransistor packaged in an opaque plastic housing that enhances ambient light rejection. The housing features an opening designed to accommodate clear tubing with outer diameters of 0.0625" (1.6mm), 0.125" (3.2mm) or 0.1875" (4.8mm).

The presence of clear liquid causes the phototransistor to sink the maximum current, while the presence of dark liquid 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.

When the system calibrates the sensor, it raises the current through the LED from 0mA to 14mA, until the phototransistor reaches the preset point. Once calibrated, the setting will remain constant, allowing for faster startup.


  • LED
    • Forward DC current of 50mA with a peak current of 1.0A
    • Reverse DC voltage is 2.0V and power dissipation is 100mW
  • Output Phototransistor
    • Maximum collector-emitter voltage of 24V or 30V
    • DC current of 50mA and power dissipation to 100mW
    • Operating temperature range is from -40ºC to +85ºC


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