Method for increasing reliability in gas detection based on indicator gradient in a sensor array

We present a method for analyte detection using an optical sensor array. The method is implemented in an ammonia gas detector, using a pH sensitive dye. The array is composed of four sensors, each coated with a different concentration of the dye. The resulting signal vector is collected by measuring the absorption at a single wavelength, at each sensor. Simple correlation of the signal vector with an expected gradient-like response enables detection of ammonia. Moreover, it improves immunity to false signals created by changes in illumination intensity and the humidity of the environment. The method of detection is generic and applicable to sensor arrays where the probe concentration can be controlled.