Table 4. Insulated probes 1 and 2. Kw = 79.78.
Distilled water
Methanol
Probe
Vref
Vdiv
Vph
C
CCD
Vref
Vdiv
Vph
C
CCD
Box 2
M
0.954
0.205
71.3
140.3
141.3
0.971
0.371
58.0
70.6
71.5
U
0.958
0.212
71.4
136.3
137.3
0.971
0.372
58.0
70.4
71.3
M
0.956
0.210
71.3
137.2
138.2
0.971
0.377
57.8
69.3
70.3
U
0.959
0.217
71.3
133.2
134.2
0.971
0.378
57.8
69.2
70.1
Box 3
M
0.984
0.169
72.6
176.8
165.1
0.992
0.287
64.7
99.5
87.7
U
0.981
0.173
72.1
171.7
160.0
0.992
0.287
64.8
99.5
87.8
M
0.985
0.172
72.6
173.9
162.2
0.992
0.289
64.9
98.9
87.2
U
0.982
0.177
72.2
168.1
156.4
0.992
0.290
64.9
98.6
86.8
Box 4
M
0.992
0.233
71.7
128.7
129.7
0.992
0.425
59.3
63.9
64.9
U
0.993
0.242
71.5
123.8
124.9
0.990
0.426
58.6
63.1
64.2
M
0.993
0.257
71.1
116.3
117.4
0.992
0.426
59.7
64.0
65.0
U
0.993
0.244
71.0
122.5
123.5
0.991
0.426
58.5
63.1
64.2
Box 2
CD = 1.59 pF/1.78 = 0.89 pF offset
Box 3
CD = 26.9 pF/2.28 = 11.76 pF offset
Box 4
CD = 2.0 pF/1.85 = 1.06 pF offset
Ratio of distilled-water dummy readings and insulated and uninsulated C readings in distilled water:
Box 2
average distilled water capacitance = 137.7 pF
Cair = 137.7/79.78 = 1.72 pF
average methanol capacitance = 70.8 pF
dielectric constant K = 70.8/1.72 = 41.2
Box 3
average distilled water capacitance = 160.9 pF
Cair = 160.9/79.78 = 2.01 pF
average methanol capacitance = 87.4 pF
dielectric constant K = 87.4/2.01 = 43.5
Box 4
average distilled water capacitance = 123.9 pF
Cair = 123.9/79.78 = 1.55 pF
average methanol capacitance = 64.6 pF
dielectric constant K = 64.6/1.55 = 41.7
next to the FERF building at USACRREL in
Based purely on the results of these two meth-
Hanover, New Hampshire. Three insulated probes
ods for calculating the dielectric constant of a
were inserted into the wall of the test pit at depths
material, procedure 2 would seem to offer much
of 6, 12, and 18 in. (15.25, 30.5, and 45.75 cm).
more accurate data.
Thermocouples were mounted on the probes so
that temperature at each depth could also be re-
corded as part of the measurement program.
RESULTS OF A
Thirty-inch cables were attached to the probes
FIELD TEST PROGRAM
using a two-part epoxy resin to ensure the water-
tight integrity of the connection. Data were read
During the winter of 19901991, a field test
manually throughout the winter's freezethaw
program was conducted to demonstrate and gain
experience in the use of this method for making
cycle at all three depths. Box 3 (nulled) was the
actual soil moisture measurements.
readout instrument. Soil temperatures were read
with a handheld thermocouple reader.
Data taking started on 19 November 1990 and
Test description
For this field demonstration, a test pit (called
continued until 3 June 1991. A complete copy of
the GSB test site) was dug in a test area located
the raw data, the dielectric constants calculated
10
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