by R. Colin Johnson
EE Times

PORTLAND, Ore. — Researchers at the National Institute of Standards and Technology (NIST) claim its electronic nose can identify hundreds of different chemical compounds using pattern-recognition algorithms that mimic the way animals recognize odors.

NIST’s electronic nose depends on 16 microheater elements supplying samples to eight different types of sensors, enabling them to detect everything from nerve gas to environmental contaminants. NIST researchers suggested the microheater technology could be used in handheld devices used by first responders and hazardous material teams as well as for industrial processes monitoring and space exploration.

The electronic nose mimics the way an animal’s nose identifies aromas using arrays of hierarchically-organized detectors, each specifically tuned to a smell category. When different sensor combinations are stimulated, a signature for the smell is catalogued. Humans, for instance, have about 350 types of smell neurons for odor recognition; dogs have several hundred more, making their sense of smell much better.

Hence, a human may smell a “fruit,” but a dog could determine if it was an apple or a pear.

NIST’s algorithms mimic this hierarchical method, using an array of semiconductor sensors arrayed just above the microheaters that vaporize odor molecules. The electronic nose uses eight oxide-film sensors deposited atop 16 microheaters. The microheaters were controlled in 350 precise temperature increments, enabling over 5,600 different combinations–enough to rival the signature recognition of the most sensitive animal noses.

NIST researchers Barani Raman and Steve Semancik claim their electronic nose is better at identifying a wide array of aromas than other conventional sensor technologies while compensating for sensor aging.

Pattern recognition algorithms learn to adapt both to changes in the samples being detected and changes in the sensor itself, such as drifting. In tests, the electronic nose was able to correctly recognize the general categories of aromas that it had never before encountered.