significantly by soils with compositions significantly different then
the references with which the gauge is calibrated. This error
indicates the amount of error you will have in your
measurements when going from one soil composition extreme
to another. Composition error is determined by measuring
limestone and granite standards with known densities.
Standards of limestone and granite that are homogenous are
available which have compositions that bracket the
composition of most soils. Composition error for nuclear gauges
is calculated by the following equation.
Lime (Gauge) and Granite (Gauge) are density of limestone
and granite standards measured by the gauge after
calibration. Lime (Actual) and Granite (Actual) are actual
density values of limestone and granite. This error indicates the
amount of error you will have in your measurement when going
from one soil composition extreme to the other.
Composition error in most gauges can be minimized by
appropriate filtering of the detection system and /or adjustment
of the source to detector distance. Even though this error can
be minimized, any adjustment to reduce this error can cause
an increase in surface error and reduction in gauge
repeatability. During design, it is extremely critical that the
gauge geometry is optimized to reduce all the above errors to
an acceptable limit.
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