Pedosphere 19(5): 588--596, 2009
ISSN 1002-0160/CN 32-1315/P
©2009 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Adjusting temperature and salinity effects on single capacitance sensors |
A. FARES1 , M. SAFEEQ1 and D. M. JENKINS2 |
1 Department of Natural Resources and Environmental Management, University of Hawaii at Manoa, 1910 East West Road, Honolulu, HI 96822 (USA)
2 Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, 1955 East West Road, Honolulu, HI 96822 (USA) |
| ABSTRACT |
| Several newly developed capacitance sensors have simplified real-time determination of soil water content.Previous work has shown that salinity and temperature can affect these sensors,but relatively little has been done to correct these effects.The objectives of this study were to evaluate the effect of media temperature and salinity on the apparent water content measured with a single capacitance sensor (SCS),and to mitigate this effect using a temperature dependent scaled voltage technique under laboratory conditions.A column study was conducted containing two media:pure deionized water and quartz sand under varying water contents (0.05 to 0.30 cm3 cm-3) and salinity (0 to 80 mmol L-1).Media temperature was varied between 5 and 45℃ using an incubator.The SCS probes and thermocouples were placed in the middle of the columns and were logged at an interval of 1 minute.There was strong negative correlation between sensor reading and temperature of deionized water with a rate of -0.779 mV ℃-1.Rates of SCS apparent output were 0.454 and 0.535 mV ℃-1 for air in heating and cooling cycles,respectively.A similar positive correlation with temperature was observed in sand at different water contents.The SCS probe was less sensitive to temperature as salinity and water content increased.Using a temperature-corrected voltage calibration model,the effect of temperature was reduced by 98%.An analytical model for salinity correction was able to minimize the error as low as ± 2% over the salinity level tested. |
| Key Words: calibration, ECH2O probes, quartz sand, water content |
| Citation: Fares, A., Safeeq, M. and Jenkins, D. M. 2009. Adjusting temperature and salinity effects on single capacitance sensors. Pedosphere. 19(5): 588-596. |
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