Decagon Devices EC-5, Руководство пользователя

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EC-5 User’s Manual
4. Collecting Data
14
The EC-5 is much less sensitive to variation in texture
and electrical conductivity because it runs at a much
higher measurement frequency. Therefore, its general
calibration equation should apply for all mineral soils up
to 8 dS/m saturation extract. Its calibration equations are
shown below for mineral soil, potting soil, and rock-
wool growing media:
Dielectric Permittivity
Dielectric permittivity can be used to determine volu-
metric water content using external published equations
such as the Topp equation. Dielectric permittivity is
given by


= 1/(-1.1

x 10
-9

RAW
3

x 10
-6


RAW
2

x 10
-3

RAW

where RAW is the output from the Decagon data logger
using 3V excitation. If you are using a non-Decagon
data logger, dielectric permittivity is given by


= 1/(

x 10
-9

mV
3

x 10
-6

mV
2

x 10
-3

mV

Mineral Soils
According to our tests, a single calibration equation will
generally suffice for all mineral soil types with electrical
conductivities from 0.1 dS/m to 10 dS/m saturation
extract. Volumetric water content (ø) is given by
ø = 8.5 * 10
-4
* RAW - 0.48 (1)