Campbell Scientific CS616 CS616 and CS625 Water Content Reflectometers - Page 44

Calculations

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CS616 and CS625 Water Content Reflectometers Gravimetric water content is calculated after the container weight is accounted for. θg = mwet − mdry mdry For the bulk density, ρbulk = mdry volumecylinder the dry weight of the sample is divided by the sample tube volume. The volumetric water content is the product of the gravimetric water content and the bulk density θv = θg *ρbulk The average water content for the replicates and the recorded CS616 period are one datum pair to be used for the calibration curve fit. 8.5 Calculations The empty cylinders used for core sampling should be clean and both empty weight and volume are measured and recorded. For a cylinder, the volume is volume = π *   d 2   2 * h where d is the inside diameter of the cylinder and h is the height of the cylinder. During soil sampling it is important that the cores be completely filled with soil but not extend beyond the ends of the cylinder. Once soil core samples are obtained, place the soil-filled cylinder in a small tray of known empty weight. This tray will hold the core sample during drying in an oven. To obtain mwet, subtract the cylinder empty weight and the container empty weight from the weight of the soil filled cylinder in the tray. Remove all the soil from the cylinder and place this soil in the tray. Dry the samples using oven or microwave methods as described above. To obtain mdry, weigh the tray containing the soil after drying. Subtract tray weight for mdry. Calculate gravimetric water content, θg, using θg = mwet − mdry mdry . 38

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CS616 and CS625 Water Content Reflectometers
Gravimetric water content is calculated after the container weight is accounted
for.
θ
g
wet
dry
dry
m
m
m
=
−
For the bulk density,
ρ
bulk
dry
cylinder
m
volume
=
the dry weight of the sample is divided by the sample tube volume.
The volumetric water content is the product of the gravimetric water content
and the bulk density
θ
θ
ρ
v
g
bulk
=
*
The average water content for the replicates and the recorded CS616 period are
one datum pair to be used for the calibration curve fit.
8.5
Calculations
The empty cylinders used for core sampling should be clean and both empty
weight and volume are measured and recorded.
For a cylinder, the volume is
volume
d
h
=
π
*
*
2
2
where d is the inside diameter of the cylinder and h is the height of the
cylinder.
During soil sampling it is important that the cores be completely filled with soil
but not extend beyond the ends of the cylinder.
Once soil core samples are obtained, place the soil-filled cylinder in a small
tray of known empty weight. This tray will hold the core sample during drying
in an oven.
To obtain m
wet
, subtract the cylinder empty weight and the container empty
weight from the weight of the soil filled cylinder in the tray.
Remove all the
soil from the cylinder and place this soil in the tray.
Dry the samples using
oven or microwave methods as described above.
To obtain m
dry
, weigh the tray containing the soil after drying.
Subtract tray
weight for m
dry
.
Calculate gravimetric water content,
θ
g
, using
θ
g
wet
dry
dry
m
m
m
=
−
.
38