Sensors 2012, 12(6), 8338-8354; doi:10.3390/s120608338
Article

A Miniature Integrated Multimodal Sensor for Measuring pH, EC and Temperature for Precision Agriculture

1 Head Office for “Tailor-Made and Baton-Zone” Graduate Course, Toyohashi University of Technology, 1-1, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580, Japan 2 Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, Aichi 441-8580, Japan 3 Electronics-Inspired Interdisciplinary Research Institute (EIIRIS), Toyohashi University of Technology, Aichi 441-8580, Japan 4 Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, 7, Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan
* Author to whom correspondence should be addressed.
Received: 30 April 2012; in revised form: 30 May 2012 / Accepted: 1 June 2012 / Published: 15 June 2012
(This article belongs to the Special Issue Ultra-Small Sensor Systems and Components)
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Abstract: Making several simultaneous measurements with different kinds of sensors at the same location in a solution is difficult because of crosstalk between the sensors. In addition, because the conditions at different locations in plant beds differ, in situ measurements in agriculture need to be done in small localized areas. We have fabricated a multimodal sensor on a small Si chip in which a pH sensor was integrated with electrical conductivity (EC) and temperature sensors. An ISFET with a Si3N4 membrane was used for the pH sensor. For the EC sensor, the electrical conductivity between platinum electrodes was measured, and the temperature sensor was a p-n junction diode. These are some of the most important measurements required for controlling the conditions in plant beds. The multimodal sensor can be inserted into a plant bed for in situ monitoring. To confirm the absence of crosstalk between the sensors, we made simultaneous measurements of pH, EC, and temperature of a pH buffer solution in a plant bed. When the solution was diluted with hot or cold water, the real time measurements showed changes to the EC and temperature, but no change in pH. We also demonstrated that our sensor was capable of simultaneous in situ measurements in rock wool without being affected by crosstalk.
Keywords: multimodal sensor; electrical conductivity sensor; pH sensor; temperature sensor; crosstalk; simultaneous measurement; real time measurement; rock wool; agriculture

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MDPI and ACS Style

Futagawa, M.; Iwasaki, T.; Murata, H.; Ishida, M.; Sawada, K. A Miniature Integrated Multimodal Sensor for Measuring pH, EC and Temperature for Precision Agriculture. Sensors 2012, 12, 8338-8354.

AMA Style

Futagawa M, Iwasaki T, Murata H, Ishida M, Sawada K. A Miniature Integrated Multimodal Sensor for Measuring pH, EC and Temperature for Precision Agriculture. Sensors. 2012; 12(6):8338-8354.

Chicago/Turabian Style

Futagawa, Masato; Iwasaki, Taichi; Murata, Hiroaki; Ishida, Makoto; Sawada, Kazuaki. 2012. "A Miniature Integrated Multimodal Sensor for Measuring pH, EC and Temperature for Precision Agriculture." Sensors 12, no. 6: 8338-8354.

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