土壌水分センサーに関する公開セミナー
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日時： 6月20日（月） 14:40-16:20
場所： 東京大学農学部７号館A棟113番教室
参加申し込み： 6月15日（水）までに、mizo@soil.en.a.u-tokyo.ac.jp に参加希望のメールをください。
講師： コリン・キャンベル氏 （デカゴン社センサー開発担当）
内容： 主として、新型の土壌水分計（ECHOプローブ、マトリッックサクションセンサー等）の特性
概要：
Decreasing Electrical Conductivity and Temperature Sensitivity of a Low-Cost Dielectric Soil Moisture Sensor
Dielectric soil moisture measurements are now widely used, both in research and in commercial agriculture. Although measurements are often made in locations where electrical conductivity (EC) and temperature fluctuations are low, high levels of either can cause difficulty in analyzing dielectric moisture data. Several researchers have proposed using higher probe frequencies to mitigate these effects, but there are limits to that approach, both in cost and effectiveness. The objective of this research was to determine what could be done to decrease salt and temperature sensitivity of the soil moisture probe in different soils. Sensitivity to EC was found to be large in coarse-textured soils but slight in fine- textured soils at low probe frequencies. Increasing the probe frequency removed most of the EC sensitivity in coarse soil but did not appear to improve the response in the fine soils. Higher frequencies also diminished temperature sensitivity considerably in all soils. While increasing frequency improved probe performance to a point, frequencies above about 70 MHz appeared to cause probe performance to worsen.
Measuring Simultaneous Temperature and Electrical Conductivity with Volumetric Water Content in a Single Sensor
Many researchers and growers need to measure volumetric water content (VWC), temperature (T), and electrical conductivity (EC) simultaneously, whether to study water and nutrient availability to a crop or to correct for problems in measurement. In the last 10 years, a few commercial probes have become available that measure all three parameters but their expense makes widespread use cost prohibitive. Decagon has been developing a low cost VWC, T, and EC probe (ECH2O TE) that improves upon the original ECH¬2O technology. To this point, the ECH2O TE has been extensively tested in rockwool and sand with tests planned for finer textured soils. Result show that VWC output has a low sensitivity to EC over a range of 0 to 8.3 dS m-1 while EC measurements correlate well with actual solution EC values. In addition, although material characteristics are very different between sand and rock wool, VWC calibrations were similar. Work is ongoing to determine how the probe functions in fine-textured soil and organic potting media.
ホームページへ戻る（
溝口勝,
環境地水学研究室,
生物・環境工学専攻,
農学生命科学研究科,
東京大学
）
mizo@soil.en.a.u-tokyo.ac.jp
Update by mizo (2005.6.10)