Sensors 2015, 15, 1252-1273; doi:10.3390/s150101252
sensors
ISSN 1424-8220
www.mdpi.com/journal/sensors
Article
A Customized Metal Oxide Semiconductor-Based Gas Sensor
Array for Onion Quality Evaluation: System Development
and Characterization
Tharun Konduru
1
, Glen C. Rains
2
and Changying Li
1,
*
1
College of Engineering, University of Georgia, 200 D.W. Brooks Dr., Athens, GA 30602, USA;
E-Mail: kondurutharun@gmail.com
2
Department of Entomology, University of Georgia, 2360 Rainwater Road, Tifton, GA 31793, USA;
E-Mail: grains@uga.edu
* Author to whom correspondence should be addressed; E-Mail: cyli@uga.edu;
Tel.: +1-706-542-4696; Fax: +1-706-542-2475.
Academic Editor: Gonzalo Pajares Martinsanz
Received: 3 November 2014 / Accepted: 4 January 2015 / Published: 12 January 2015
Abstract: A gas sensor array, consisting of seven Metal Oxide Semiconductor (MOS)
sensors that are sensitive to a wide range of organic volatile compounds was developed to
detect rotten onions during storage. These MOS sensors were enclosed in a specially
designed Teflon chamber equipped with a gas delivery system to pump volatiles from the
onion samples into the chamber. The electronic circuit mainly comprised a microcontroller,
non-volatile memory chip, and trickle-charge real time clock chip, serial communication
chip, and parallel LCD panel. User preferences are communicated with the on-board
microcontroller through a graphical user interface developed using LabVIEW. The
developed gas sensor array was characterized and the discrimination potential was tested
by exposing it to three different concentrations of acetone (ketone), acetonitrile (nitrile),
ethyl acetate (ester), and ethanol (alcohol). The gas sensor array could differentiate the four
chemicals of same concentrations and different concentrations within the chemical with
significant difference. Experiment results also showed that the system was able to
discriminate two concentrations (196 and 1964 ppm) of methlypropyl sulfide and two
concentrations (145 and 1452 ppm) of 2-nonanone, two key volatile compounds emitted by
rotten onions. As a proof of concept, the gas sensor array was able to achieve 89% correct
classification of sour skin infected onions. The customized low-cost gas sensor array could
be a useful tool to detect onion postharvest diseases in storage.
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