SM150T User Manual 1.0
Appendix 1
44
Insert SM150T into the sample and record its output in Volts.
V
w
= 0.350V
Dry the sample thoroughly.
With mineral soils this is usually achieved by keeping it in the
oven at 105°C for several hours or days (the time required
depends on the sample size and porosity).
For organic
soils and composts it’s usual to air-dry the
sample to avoid burning off any volatile factions.
Weigh the dry sample in the beaker.
W
0
= 627.2g
Re-insert the SM150T into the dry sample and record this
reading.
V
0
= 0.051V
Calculate
a
0
For the SM150T,
In the dry soil
V
=
V
0
= 0.051 Volts
Substitute this into the equation
√𝜖 = 1.0 + 14.4396𝑉 − 31.2587𝑉
2
+ 49.0575𝑉
3
− 36.5575𝑉
4
+ 10.7117𝑉
5
gives
√𝜖 = 1.66
Since
0
= 0, this is the value needed for
a
0
a
0
= 1.66
Calculate
w
The water content of the wet soil,
w
, can be calculated from
the weight of water lost during drying, (
W
w
–
W
0
) and its
volume,
L
s
:
25
.
0
5
.
463
2
.
627
3
.
743
0
s
w
w
L
W
W
w
= 0.25
