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TT Electronics' Self-Calibrating Fluid Sensors Enable Engineers to Easily Correct for System Variations

Mon, 06/27/2011 - 12:41pm


Fluid SensorsTT electronics Optoelectronics Business Unit has developed a self-calibration system for its OPB350 Series optoelectronic fluid sensors that is designed to save engineers set-up time as well as maintain the sensors’ optimum accuracy over years of operation. Designated the OCB350 Series, the non-contact fluid sensor features an automatic calibration function that can be used to compensate for manufacturing, environmental and system variances inherent with optical devices. This self-calibration feature makes the sensors ideal for medical equipment used to deliver IV fluids, transfusion/infusion systems, blood plasma and urine analysis; as well as precision industrial applications where tubing is used to deliver toner, lubricating oil, or other clear or colored fluids.

The sensor operates with an infrared LED/phototransistor pair to determine the presence or absence of fluids in a tube that passes through the sensor housing, using the difference in refractive properties to vary the output current to signal different states, including “fluid present,” “no fluid present,” and “no tube present.” It can also be used to identify the presence of air bubbles in the fluid passing through the tube.

The auto-calibration function enables the design engineer to narrow the device’s initial output state, which helps maintain consistent switching performance by compensating for several factors, including ambient light variation; LED/phototransistor performance degradation over time, overall system power variations; and fluctuations in ambient temperature. The calibration settings are maintained, even if power is lost to the device, which enables faster start-up mode without the need for calibration each time the sensor is initiated. In addition, the sensor can be calibrated remotely before installation.

The OCB350 Series devices include the sensor mounted on a PC board with an interface cable, and a series of colored LEDs to indicate the various states of calibration. Custom PC boards can also be developed to meet customer requirements.

The OCB350 Series auto-calibrating fluid sensors are available to fit applications using clear tubing with outer diameters of 0.0625” (1.6mm), 0.125” (3.2mm), 0.1875” (4.8mm), or 0.25” (6.3mm). Wide operating temperature range is from -40ºC to +85ºC.

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