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1.5.2. SONO-VARIO for measuring Moisture of Expanded Clay and Lightly Sand
Concerning the material density, expanded clay and lightly sand differ significantly in comparison to
sand and gravel. Therefore a separate calibration for each material is necessary. It is to consider that
expanded clay below a moisture level of 12% still can absorb more water, ie here it must be calculated
with more addition of water into a mixture. At moisture levels above 12% (the maximum core moisture
of expanded clay), the surface water of the expanded clay would act as a free addition of water and
the addition of water into a mixture should be reduced.
For measuring these two materials the probe calibration Cal10 or Cal11 can be selected.
If you want to use a single SONO probe with the calibration Cal1 for both normal sand/gravel as well
as these two materials, then there is the possibility with a simple mathematical conversion inside a
PLC. Requirement would be that the PLC knows when and what material is to be measured. You may
convert the following:
MoistureLightlySand = MeasurementValueCal1 * Factor of 4
MoistureExpandedClay = MeasurementValueCal1 * Factor of 4.8 + 3.2 Offset
It is to consider that this correction calculation for expanded clay can only be measured above 3.2%,
which in practice would be acceptable as it is unlikely that in plant operation the moisture in expanded
clay is below 3.2%.