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  • Fluid Sensors
Mar 2009
TT Electronics
CARROLLTON, Texas, March 24, 2009 – Providing design engineers with a simplified means of detecting the presence of fluid in transparent tubing, TT electronics Optek Technology has expanded its family of fluid sensors to include automatic calibration circuitry and a preset trip level feature.

Designated the OCB350 series, the sensors require only an optical device and a power supply for operation. They 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.”

The sensors minimize the effects of changes in their optics caused by manufacturing variances, ambient light, temperature fluctuation and degradation of the LED and phototransistor over time. The calibration circuit allows design engineers to narrow the expected output state, allowing the fluid sensors to operate with the same startup setting for years.

OPTEK_Circuitry.jpgThe liquid sensor comprises an LED and a phototransistor packaged in an opaque plastic housing that enhances ambient light rejection. The housing features an opening that accommodates clear tubing with outer diameters of 1.6, 3.2 or 4.8 mm. 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.

The sensors maintain the calibrated setting even if power is lost. Designers can initiate the calibration procedure at any time by grounding the J1-pin-4, which allows the device to be calibrated remotely and then mounted in the equipment. The calibration system features four LEDs that indicate whether the device is being calibrated (blinking green); whether the device cannot be calibrated (red); and whether the analog output has reached the logical trip higher (blue) or lower than the calibration point (green).

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

The LED features a forward DC current of 50 mA with a peak current of 1.0 A. Reverse DC voltage is 2 V, and power dissipation is 100 mW. The output phototransistor features a maximum collector-emitter voltage of 24 or 30 V, with collector DC current of 50 mA and power dissipation to 100 mW. Operating temperature range is from –40 to 85 ºC.

The sensors are suitable for noncontact fluid-sensing applications, including IV fluids, oils and other petroleum products, colored fluids, toner and water.

For more information, visit:

TT electronics Optek Technology
1645 Wallace Drive
Carrollton, Texas 75006
Phone: (972) 323-2200
Fax: (972) 323-2396

The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The science includes light emission, transmission, deflection, amplification and detection by optical components and instruments, lasers and other light sources, fiber optics, electro-optical instrumentation, related hardware and electronics, and sophisticated systems. The range of applications of photonics extends from energy generation to detection to communications and...
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