Spectrum WaterScout SMEC 300, Руководство по эксплуатации продукта, Страница: 22 / 24

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Electrical
Conductivity
Electrical conductivity (EC) is a measure of how well a
solution conducts electrons. Pure water does not conduct
electricity at all. However, as the concentration of
dissolved ions increases, the electrical charged carried by
those ions of the solution will increase as well. This is
reflected in a higher EC measurement for that solution.
In soil solutions, the sources of these ions are minerals in
the soil (such as sodium or calcium) and applied fertiliz-
ers. The EC of a liquid at a given temperature is governed
mainly by the amount of dissolved salt ions. However,
when a direct measurement is being made in a wet soil,
the degree of saturation also impacts the measured EC.
This is because as water content decreases, the conductive
path becomes increasingly tortuous, thus decreasing the
EC even though the concentration of salt in the remaining
liquid is increasing. Such an EC measurement is some-
times referred to as bulk EC because it reflects how well
electrons in the bulk soil are conducted. The SMEC 300
measures bulk EC. An alternative measure of EC is pore
EC. This is the value that would be measured if the soil
solution alone were extracted from the soil and measured.
Pore EC will almost always increase as soil moisture con-
tent decreases.
The EC sensor for the SMEC 300 consists of a pair of car-
bon ink electrodes that are integrated onto the sensor sur-
face. The EC electrodes measure the conductivity of wet
soil in contact with the sensor. The carbon ink electrodes
provide a large surface area which minimizes the effect of
localized dry spots or loss of contact in the soil.