User Manual
SONO-MIX MINI Version 2_7
2017-05-12
Page 14
2.3. Calibration of SONO-MIX MINI in a mixing plant
SONO-MIX MINI is delivered with a raw calibration function which is far higher than the real moisture
values (kiln dried values) of a sand/gravel or fresh concrete mixture. The reason is that SONO-MIX use
a powerful modified filter algorithm, which would work incorrect at Zero-values (division by zero results
in infinite). Therefore it is necessary with SONO-MIX, (as well as with all other moisture probes), to
make a recipe specific calibration with the PLC in the mixing plant. Another reason for this calibration is
that every mixer type has another behaviour concerning the raw density of the mixed material.
In practice, a mixer moisture probe has to be calibrated with two points in the mixing plant. The first
calibration point should be relatively dry, e.g. at 2 to 3% gravimetric moisture. The second point should
be in a range which matches the maximum moisture value in practice, e.g. 5%. The closely together
these both moisture-values1 and 2 are, the higher could be the measurement error due to the
reference measurement, especially at moisture values which are beyond of these two points or not
between these two points!
Following process can be recommended:
1. Record measurement values in the PLC for a dry mixture of one cubic meter, i.e. the mixture
has a relative low water content. It is recommended to average the values of the PLC over the
last 5 seconds of the dry mixing time. In this example a measurement value of 8126 has been
recorded with the PLC:
SONO-MIX
Measurement
values
(current signal
from 4…20mA)
Measurement
value in a PC
(in % moisture)
Digit Value of
A/D-Converter
PLC
without unit from
0 to max. 32768
digits
Water
content
Measurement
values with dry
mixture
5.968 mA
3.2
8126
This is the
Dry-value-A/D
2.
Add water manually into the dryer mixture, e.g.
20.0 liter water.
The added and measured
water content is later used for the calculation of the c1-Sensitivity of the SONO-MIX for this
recipe. When
the mixture has a stable consistency, than
record the
measurement values with
