Instruction manual

CS650 and CS655 Water Content Reflectometers
The sample tubes should be pushed evenly into the soil surface. Remove the
tube and sample and gently trim the ends of excess soil. Remove excess soil
from outside of tube.
Remove all the soil from tube to a tray or container of known mass that can be
put in oven or microwave. Weigh and record the wet soil mass. If samples
must be stored prior to weighing, seal the container with tape or inside a plastic
bag to prevent water loss and store away from direct sunlight.
Water is removed from the sample by heating with oven or microwave. Oven
drying requires 24 hours at 105 °C. Microwave drying typically takes 20
minutes depending on microwave power and sample water content. ASTM
Method D4643-93 requires heating in microwave for 3 minutes, cooling in
desiccator then weighing and repeating this process until mass is constant.
Gravimetric water content is calculated after the container mass is accounted
for.
θ
g
wet dry
dry
m m
m
=
−
For the bulk density,
ρ
bulk
dry
cylinder
m
volume
=
the dry mass 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 CS650 period are
one datum pair to be used for the calibration curve fit.
8.4.5 Calculations
The empty cylinders used for core sampling should be clean and both empty
mass 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 mass. This tray will hold the core sample during drying
in an oven.
28