Technical Reference
⚫
53
where
is a geometry factor which is determined by the
distance between the electrodes and their areas in contact with
the soil. Note that contact problems of the electrodes with the
soil will be reflected in
.
The equivalent circuit for such a lossy capacitor is a loss-free
capacitor,
C
, with a conductor,
G
, in parallel.
C
represents the
energy storage capability of the soil and is related to
b
.
G
represents the energy loss and is related to
b
.
Y
may be
written in terms of
C
and
G
as:
C
j
G
Y
+
=
[10.]
From Eq. [9] and Eq. [10] and with Eq. [4] to Eq. [8] in mind, the
real and imaginary parts of
Y
can be found:
)
(
p
g
G
=
[11.]
and
(
)
)
(
'
'
p
0
0
b
g
C
+
=
=
[12.]
In terms of the measurable bulk quantities
b
and
b
:
)
(
p
b
g
=
[13.]
and
)
(
'
'
'
p
0
b
b
g
+
=
=
[14.]
From Eq. [13] and [14] the ionic conductivity of the pore water
can be written as:
)
'
-
'
(
'
0
b
b
p
p
b
=
=
[15.]
The model of Eq. [15] describes the relationship between
p
of
the pore water (the water that can be extracted from the soil)
and the values
b
and
b
as measured in the bulk soil using a
dielectric sensor. The offset
0
b
'
=
can be calculated from the
b
and
b
values measured at two arbitrary free water content
values.
