An assembly of sensors, denoted an electronic tongue, is undergoing development as a prototype of compact devices for use in measuring concentrations of contaminants in water. Thus far, the electronic tongue has been tested on ions of Cu, Zn, Pb, and Fe and shown to respond to concentrations as low as about 10 parts per million. This electronic tongue is expected to be capable of measuring concentrations of other metal ions and organic compounds. Potential uses for electronic tongues include monitoring the chemical quality of water in a variety of natural, industrial, and laboratory settings; detecting micro-organisms indirectly by measuring microbially influenced corrosion; and characterizing compounds of interest to the pharmaceutical and food industries.
This version of the electronic tongue includes a heater, a temperature sensor, an array of ion-specific electrodes, an oxidation/reduction sensor pair, an electrical-conductivity sensor, and an array of galvanic cells, all on one compact ceramic substrate (see figure). Special-purpose electronic excitation and readout circuitry for the sensors has also been constructed.
The main advantage of the electronic tongue, relative to electrodes of this type used traditionally to assess water quality, is extreme ruggedness.
The types of measurements that can be performed by use of the sensors on the electronic tongue are quite varied. The best combination of types of measurements for a given application depends on the specific contaminants that one seeks to detect. Experimental studies to identify such combinations were in progress at the time of reporting the information for this article.
This work was done by Marlin Buehler and Gregory Kuhlman of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Electronics/Computers category.
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Refer to NPO-30601, volume and number of this NASA Tech Briefs issue, and the page number.