Campbell CS650, User Manual

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User Manual
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Probe rods can be buried in a tray or inserted into a column. When using a
column, insert the rods carefully through surface until rods are completely
surrounded by soil. Movement of rods from side-to-side during insertion can form
air voids around rod surface and lead to measurement error.
Collect the probe permittivity output. Repeat previous step and this step three or
four times.
Determine volumetric water content by subsampling soil column after removing
probe or using mass of column. If subsampling is used, remove soil from column
and remix with samples used for water content measurement. Repack column.
Water can then be added to the top of the container. It must be allowed to
equilibrate. Cover the container during equilibration to prevent evaporation. The
time required for equilibration depends on the amount of water added and the
hydraulic properties of the soil. Equilibration can be verified by frequently
observing the CS650 permittivity output. When permittivity is constant,
equilibration is achieved. Collect a set of calibration data values and repeat the
water addition procedure again if needed.
With soil at equilibrium, record the CS650 permittivity.
Take subsamples of the soil using containers of known volume. This is necessary
for measurement of bulk density. Copper tubing of diameter

2.5 cm (1 in) and
length about 5 cm (2 ins) works well. The tubes can be pressed into the soil
surface.
It is good to take replicate samples. Three carefully handled samples will provide
good results.
The sample tubes should be pushed evenly into the soil. 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.
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 measured mass is constant.
Gravimetric water content is calculated after the container mass is accounted for.

g
wet dry
dry
m m
m


For the bulk density

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