Compensating for Effects of Humidity on Electronic Noses

NASA Tech Briefs, Jun 2004

Corrections are derived from outputs of separate humidity and temperature sensors.

NASA's Jet Propulsion Laboratory, Pasadena, California

A method of compensating for the effects of humidity on the readouts of electronic noses has been devised and tested. The method is especially appropriate for use in environments in which humidity is not or cannot be controlled - for example, in the vicinity of a chemical spill, which can be accompanied by large local changes in humidity.

Heretofore, it has been common practice to treat water vapor as merely another analyte, the concentration of which is determined, along with that of the other analytes, in a computational process based on deconvolution. This practice works well, but leaves room for improvement: changes in humidity can give rise to large changes in electronic-nose responses. If corrections for humidity are not made, the large humidity-induced responses may swamp smaller responses associated with low concentrations of analytes.

The present method offers an improvement. The underlying concept is simple: One augments an electronic nose with a separate humidity and a separate temperature sensor. The outputs of the humidity and temperature sensors are used to generate values that are subtracted from the readings of the other sensors in an electronic nose to correct for the temperature-dependent contributions of humidity to those readings. Hence, in principle, what remains after corrections are the contributions of the analytes only. Laboratory experiments on a first-generation electronic nose have shown that this method is effective and improves the success rate of identification of analyte/water mixtures. Work on a second-generation device was in progress at the time of reporting the information for this article.

This work was done by Margie Homer, Margaret A. Ryan, Kenneth Manatt, Hanying Zhou, and Allison Manfreda of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at uiww.techbriefs.com/tsp under the Physical Sciences category.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:

Innovative Technology Assets Management

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Refer to NPO-30615, volume and number of this NASA Tech Briefs issue, and the page number.