Interface Electronic Circuitry for an Electronic Tongue

NASA’s Jet Propulsion Laboratory, Pasadena, California

Monday, October 01 2007 In the present version, the electronic tongue contains 12 analog cells: nine oxidation/ reduction (redox) electrochemical cells, an electrical- conductivity cell, and the aforementioned heater and temperature sensor. The interface circuitry (see figure) consists mainly of 12 digitalto- analog converters (DACs) for excitation of the cells, and four analog-to-digital converters (ADCs) for readout from the cells connected to 12 analog cells. Each analog cell is made of two instrument amplifiers, two operational amplifiers and analog filters for reducing signal-to-noise ratios, and control and switching circuits.

The interface circuitry resides on a board mounted immediately below the ceramic substrate and, as in the prior version, is connected to the analog cells via miniature edge connectors on the ceramic substrate. By thus placing the ADCs and DACs near the analog cells, the design helps to minimize pickup of noise and reduce cross-talk on the analog signal lines.

As in the prior version, the control circuitry can be programmed to make the DACs generate the specified excitation waveforms and to make the ADCs acquire the specified response waveform data, and each electrochemical cell can be addressed individually. Depending on the specific application, a given electrochemical cell can be operated in a potentiostatic mode (voltage forced, current measured) or a galvanostatic mode (current forced, voltage measured), or can be made to alternate between the two modes. In one typical application, the main sequence of excitations and responses in a potentiostatic mode is chosen to implement anodic stripping voltammetry or cyclic voltammetry. In another typical application, a working electrode of a cell is operated in a galvanostatic mode at a positive bias for generating oxygen or a negative bias for generating hydrogen.

This work was done by Didier Keymeulen and Martin Buehler of Caltech for NASA’s Jet Propulsion Laboratory.

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
JPL
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109-8099
(818) 354-2240
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Refer to NPO-41365, volume and number of this NASA Tech Briefs issue, and the page number.