An optical oxygen sensor system based on the process of fluorescence quenching is reported. The device detects the fluorescence quenching of a ruthenium complex (Ru(clip-phen)3(ClO)4) also known as RUDPP { 1] by sensing minute variations of a fluorescent membrane emission intensity. A dual channel design consisting of a reference branch and a sensing branch is used. Both branches include modulated light from a bright blue LED acting as the excitation source coupled through an enclosed channel to a photo-diode. The sensing branch has the RUDPP fluorescence quenching membrane sandwiched between the blue LED and the photo-diode, while the reference branch is void of such membrane. To avoid membrane saturation in the sensing branch, the excitation source is modulated with a 350 Hz square wave. The output signals of the two channels are amplified separately and subtracted from each other using a difference amplifier. Adjusting the difference amplifier output to zero effectively ensures excitation source interference cancelation. The photo-diode in the sensing branch detects the intensity variations as a function of fluorescent quenching by oxygen. It was possible to isolate the fluorescent signal completely, based solely on electronic components, without the use of optical ifiters. The output signal from the difference amplifier is further amplified (with an adjustable gain for calibration) and displayed. Sensor performance was tested and it exhibited both excellent sensitivity and response time, compared to the recent oxygen sensors reported by others {2]-{3J. A decrease of less than 4 percent oxygen concentration was readily detectable. We concluded that this design establishes the feasibility of developing an optical oxygen sensor, relying solely on optoelectronic components for detection.

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