How the
Profile Probe
works
Before you rush out and hammer
your access tubes into the soil,
it will help to understand a little about how the
Profile Probe
works:
When power is applied to the
Profile Probe
...
...it creates a 100MHz signal (similar to FM
radio).
The signal is applied to pairs of stainless steel
rings....
... which transmit an electromagnetic field
extending about 100mm into the soil.
The field passes easily through the access tube
walls, but less easily through any air gaps.
The water content of the soil surrounding the
rings...
...dominates its
permittivity
.
ε
(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
…resulting in a stable voltage output that…
...acts as a simple, sensitive measure of
soil
Soil Moisture
moisture content
.
22 %
Profile Probe User Manual
3.0a
Introduction
z
9
