Table 6. Equations used for calibration runs.
both of these runs was also generated. Box 1 and
3.1831 1011 Vref sin(Vph)/Vdiv
C
=
Actual data points for each of these calibration
1.04 1012
Ccable
=
curves are shown in Tables 7 and 8. Since the
3.5 1012
Cair
=
calibration curves were quite nonlinear, calibra-
Cmeas
=
CCcable
63.2 1012 Cmeas/[(63.2 1012) Cmeas]
Cprobe
=
ε
the combination of both runs were generated for
=
Cprobe/Cair
three ranges of dielectric constant: low end,
Notes:
midrange, and high range. These calibration equa-
Vref, Vdif, and Vph are the actual values read as the
tions are shown in Table 9 (for percent dry weight)
raw field data.
and Table 10 (for percent volume). Other perti-
Ccable is the small offset capacitance that corrects for a
nent soil data, such as each sample's dry weight
minor unnulled portion of the cable.
and volume, are also shown. Note that this proce-
insulation on the probe.
dure is primarily a volume-calibration method,
The 3.1831 1011 in the first equation is from 1/Rω
and the percent dry weights were calculated by
= 1/500 2 π 10 106. The minus sign corrects
using the density of the test soil, not by using the
the minus value for Vph to yield a positive capaci-
actual density of soils at the test site.
tance value.
Table 7. Calibration run 2, GSB test site.
Table 8. Calibration run 3, GSB test site.
Dry weight = 65.9 g
Dry weight = 68.3 g
Volume = 48 cm3
Volume = 46 cm3
Insulated probe: Box 1, probe circuit 1 (nulled)
Insulated probe: Box 1, probe circuit 1 (nulled)
Cair = 3.2
Cair = 3.29
Dielectric
Weight of
Percent of
Dielectric
Weight of
Percent of
constant
water added
dry weight
constant
water added
dry weight
Low end
Low end
2.10 (dry)
0.00
0.0
2.07 (dry)
0.00
0.0
2.22
0.63
1.0
2.47
0.63
1.0
2.92
1.26
1.9
2.89
1.26
1.8
5.22
1.89
2.9
3.98
1.89
2.8
6.63
2.52
3.8
5.36
2.52
3.7
7.90
3.10
4.7
6.64
3.15
4.6
9.28
3.73
5.7
7.77
3.78
5.5
10.76
4.36
6.6
9.19
4.41
6.4
11.68
4.99
7.6
10.52
5.05
7.4
12.17
5.62
8.5
11.34
5.68
8.3
Midrange
Midrange
12.88
6.25
9.5
11.95
6.31
9.2
13.42
6.88
10.4
12.23
6.94
10.2
13.61
7.51
11.4
12.73
7.57
11.1
13.91
8.14
12.4
13.44
8.20
12.0
14.29
8.77
13.3
13.90
8.83
12.9
14.20
9.40
14.3
14.27
9.46
13.8
14.61
10.03
15.2
14.58
10.09
14.8
15.13
10.66
16.2
15.10
10.72
15.7
15.60
11.29
17.1
15.63
11.35
16.6
High range
High range
16.36
11.92
18.1
15.97
11.98
17.5
17.05
12.55
19.0
16.44
12.61
18.5
17.55
13.18
20.0
17.01
13.24
19.40
18.12
13.81
21.0
17.58
13.81
20.20
12