Campbell Scientific TDR100 Time Domain Reflectometry Systems User Manual
Page 40
TDR100
To view the current parameter values type GECP at the > prompt. The values
of the 4 parameters are returned.
The default values for the threshold equation are:
a = 0
b = 1
c = 2
Therefore the default threshold is the mean plus twice the standard deviation of
the values in the 10-point window before the probe. All values in the window
must be below the threshold value.
The threshold equation was chosen to provide flexibility when conditions of
noise or large amount of signal attenuation are present.
threshold = a*(maximum derivative) + b*(mean from step 3) + c*(standard
deviation from step 3)
840
860
880
900
920
940
960
980
1000
0
0.1
0.2
0.3
0.4
0.5
waveform
waveform derivative
waveform and derivative near probe
data point
re
fle
ct
io
n c
oe
ffi
ci
en
t
max_deriv
indexmax_derivative
values used for applied signal
FIGURE 9-3. Waveform and derivative values near TDR probe and locations of index for point of
maximum derivative and maximum derivative value. The green band represents the results of the
search using the threshold value.
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