Auto Calibration Sensor
Feb 2010Optek Technology, Industrial Sensing & ControlRequest Info
CARROLLTON, Texas, Feb. 11, 2010 – Providing medical design engineers with a cost-effective alternative to ultrasonic sensors, TT electronics Optek Technology’s OCB350 fluid sensor features automatic calibration circuitry and is available with multiple output states, including “fluid present,” “no fluid present” and “no tube present.” It is suitable for use in medical applications, such as monitoring the presence of fluid or air in tubing for infusion and transfusion pumps where fluids of different optical densities are used.
The sensor is designed to maintain the calibrated setting even if power is lost. Once calibrated, the setting will remain constant, allowing for faster start-up. The self-calibration feature enables the sensor to adapt to changes in fluid type.
Designers can initiate the calibration procedure at any time by grounding the J1-pin-4, which allows the device to be remotely calibrated and then mounted in the equipment. When the system calibrates the sensor, it raises the current through the LED from 0 to 14 mA, until the phototransistor reaches the pre-set point.
The sensor comprises an infrared LED and a phototransistor packaged in an opaque plastic housing that enhances ambient light rejection and that features an opening designed to accommodate 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 present” states. If no tube is present, the phototransistor sinks the current between the dark and clear fluid states.
The infrared LED produces a forward DC current of 50 mA with a peak current of 1 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.