Delta-T Devices WET150, Руководство пользователя

Страница: 65 / 72

Appendix
⚫
65
Insert WET150 into the sample, press [Read] on
the meter and record the permittivity reading (
ε’
).
ε
w
= 9.06, I.e.
√
ε
w
= 3.01
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 / composts it
’s advisable to dry
the sample at a lower temperature to avoid
driving off volatile factions.
Weigh the dry sample in the beaker.
W
0
= 1400g
Re-insert the WET150 into the dry sample and
again record the permittivity reading.
ε
0
= 2.56, I.e.
√
ε
0
= 1.60
Calculate
a
0
Since the water content of the dry soil,
θ
0
= 0, this
gives
a
0
directly:
√
ε
0
=
a
0
= 1.60
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
:
𝜃
𝑤
= (𝑊
𝑤
− 𝑊
0
) 𝐿
𝑠
⁄ = (1573 − 1400) 960 ⁄ = 0.180

w
= 0.180
Calculate
a
1
𝑎
1
= (√𝜀
𝑤
− √𝜀
0
) (𝜃
𝑤
− 𝜃
0
) ⁄
= (3.01 − 1.60) (0.173 − 0)
⁄
= 7.82
1400.0