Environmental Engineering Reference
In-Depth Information
The advantage of the ICM method is that, thanks to the simplicity of the used
equations, it leads very rapidly and without much effort to the estimation of
K
p
.
5.5.3
Validation of the Methods
The experimental setup for the reflectometry measurements includes the HL1500
TDR unit [4], the 15 cm-long three-rod probe (Campbell Scientific CS630) [3], and
a 3.5 m-long 50
-matched coaxial cable.
The first step was the evaluation of the probe constant
K
p
,
C
−
S
to be used for sub-
sequent measurements based on the C-S method. After preparing nine electrolyte
solutions, the corresponding values of
Ω
σ
0
,
ref
were measured through a conductiv-
ity meter and considered as reference values. The value of
K
p
,
C
−
S
was evaluated
from the linear fitting of the measurement points in the
G
s
−
σ
0
plane, as shown
in Fig. 5.13. The obtained value for
K
p
,
C
−
S
is 2.9 m
−
1
, whereas the correspond-
ing standard uncertainty evaluated according to the formulation described in [13] is
u
K
p
=
2m
−
1
.
0
.
100
80
60
40
20
measurement points
linear fit
0
0
5
10
15
20
25
30
35
G
s
(mS)
Fig. 5.13
G
s
−
σ
0
,
ref
regression curve obtained from the measurements on nine electrolyte
solutions differing in reference electrical conductivities. The curve slope gives the
K
p
to be
used for the estimation of σ
0
through the C-S method [13]
At the same time, TDR waveforms at longer distances were acquired on the same
electrolyte solutions and were used to calculate
G
s
for each electrolyte solution,
as the average value of TDR measurements in the considered long-distance range.
Fig. 5.14 shows the typical TDR waveforms measured for the nine electrolyte so-
lutions, which differed in reference values of electrical conductivity. It can be seen
that the waveforms are quite stable in the distance range 750-1250 m; therefore,
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