Instruction manual

CS650 and CS655 Water Content Reflectometers
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 ≥ 1
inch and length about 2 inch 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.
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
permittivity are one datum pair to be used for the calibration curve fit.
8.4.4 Collecting Field Data for Calibration
Required equipment:
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