Sensitivity and the Problem of False Positives

One of the primary characteristics of any sensor is its sensitivity. In principle, increased sensitivity should lead to increased performance, that is, a greater likelihood of finding the object being sought. However, increasing the sensitivity in a cluttered environment often leads instead to an increase in false positive. A false positive occurs when the sensor system correctly detects an item of the 

Clearly, if there is unbumed explosive material present in an area of interest, then the trace chemical sensor will register a false positive. Similarly, some bulk chemical sensors may provide false positives when they encounter a mass of nitrogen-rich material, such as fertilizer or feces. In either case the rate of false positives is still likely to be less that the false-positive rate of a metal detector. 

Adjusting the sensor sensitivity is usually only partially successful. There is another way to overcome the problem of false positives. A suite of sensors that are orthogonal in principle can be used together. 

Visual Sensor (Senses the shape, size, texture, and appearance of an object) 

Trace Chemical Sensor (Senses presence of specific molecules) 

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