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Thank you for purchasing a WaterScout SMEC 300 Soil Mois-
ture Sensor. The moisture and nutrient status of your soil or
container substrate are key pieces of information. They allow
you to tailor your irrigation and fertilization program to suit
your crop's needs. They also help identify if it is necessary to
leach salts from the profile. The SMEC 300 combines afforda-
bility and accuracy into a sensor that is easy to install.
The soil moisture sensor consists of two electrodes that func-
tion as a capacitor, with the surrounding soil serving as the di-
electric. An 80 MHz oscillator drives the capacitor and a signal
proportional to the soil’s dielectric permittivity is converted to
the output signal. The dielectric permittivity of water is much
greater than air, soil minerals and organic matter. So, changes
in water content can be detected by the sensor circuitry and cor-
related to the soil’s moisture content.
The salinity of the soil solution, irrigation water or fertilizer
solution is an important parameter affecting the root zone envi-
ronment. Any of these factors can have a significant effect on
plant growth and physiology. The easiest way to monitor salin-
ity is by measuring the electrical conductivity (EC). EC is
strongly correlated to the salinity of the soil solution. EC meas-
urement is also affected by temperature and, to a lesser degree,
by soil moisture content. The SMEC 300 measures EC with a
pair of carbon ink electrodes which provide a large contact sur-
face with the soil solution. Temperature is measured with a
thermistor potted in the sensor molding.
The SMEC 300 is designed to be compatible with the Watch-
Dog®data loggers and weather stations as well as the Field
Scout®soil sensor reader. SpecWareTM software enables you to
view your data in graphical and tabular form as well as run re-
ports customized to your application.
General Overview
