SM150T User Manual 1.0
Introduction
9
How the SM150T works
When power is applied to the
SM150T
...
...it creates a 100MHz waveform (similar to FM radio).
The waveform is applied to a pair of stainless steel rods
which transmit an electromagnetic field into the soil.
The water content of the soil surrounding the rods...
...dominates its
permittivity
.
(A measure of a material’s response to polarisation in
an electromagnetic field. Water has a permittivity
81,
compared to soil
4 and air
1)
The permittivity of the soil has a strong influence on the
applied field…
V
out
…which is detected by the SM150T, resulting in a
stable voltage output that…
Soil Moisture
22 %
...acts as a simple, sensitive measure of
soil moisture
content
.
