A new electronic sniffer called the zNose is able to identify hundreds of scents in a mix, and is also able to measure the quantities of each scent. The new sensor, manufactured by Electronic Sensor Technology of Newbury Park, California, is the first of its kind accurate enough to be given US Environmental Protection Agency approval. The makers of zNose say it can be used to detect pollutants in nearly everything - from plastics and perfumes to food items. The zNose works by using fast chromatography, which separates scents by their chemical and physical properties.
Different chemicals show up on the chromatography unit at different times.
The sensitivity of the zNose is determined by its surface acoustic wave detector, which measures the concentration of each chemical. This devise uses a piezoelectric crystal with an electrode on one end that generates 500-megahertz ultrasound waves on the surface of the crystal. An electrode on the other end picks up these waves. Chemicals from the chromatography unit are absorbed on the surface of the detector crystal, which causes a small change in the tone arriving at the detector electrode. This change indicates how much of the chemical is present.