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1.6. Creating a linear Calibration Curve for a specific Material
The calibration curves Cal1 to Cal15 can be easily created or adapted for specific materials with the
help of SONO-CONFIG. Therefore, two measurement points need to be identified with the probe.
Point P1 at dried material and point P2 at moist material where the points P1 and P2 should be far
enough apart to get a best possible calibration curve. The moisture content of the material at point P1
and P2 can be determined with laboratory measurement methods (oven drying). It is to consider that
sufficient material is measured to get a representative value.
Under the menu
"Calibration
" and the window "
Material Property Calibration
" the calibration curves
CAL1 to Cal15 which are stored in the SONO probe are loaded and displayed on the screen (takes
max. 1 minute). With the mouse pointer individual calibration curves can be tested with the SONO-
probe by activating the button "
Set Active Calib
". The measurement of the moisture value
(
MoistAve)
with the associated radar time
tpAve
at point P1 and P2 is started using the program
SONO-CONFIG in the sub menu "
Test
" and "
Test in Mode CF
" (see "Quick Guide for the Software
SONO- CONFIG").
Step 1:
The radar pulse time
tpAve
of the probe is measured with dried material. Ideally, this takes
place during operation of a mixer/dryer in order to take into account possible density fluctuations of the
material. It is recommended to detect multiple measurement values for finding a best average value
for
tpAve
. The result is the first calibration point P1 (e.g. 70/0). I.e. 70ps (picoseconds) of the radar
pulse time
tpAve
corresponds to 0% moisture content of the material. But it would be also possible to
use a higher point P1´ (e.g. 190/7) where a
tpAve
of 190ps corresponds to a moisture content of 7%.
The gravimetric moisture content of the material, e.g. 7% has to be determined with laboratory
measurement methods (oven drying).
Step 2:
The radar pulse time
tpAve
of the probe is measured with moist material. Ideally, this also
takes place during operation of a mixer/dryer. Again, it is recommended to detect multiple
measurement values of
tpAve
for finding a best average value. The result is the second calibration
point P2 with X2/Y2 (e.g. 500/25). I.e.
tpAve
of 500ps corresponds to 25% moisture content. The
gravimetric moisture content of the material, e.g. 25% has to be determined with laboratory
measurement methods (oven drying).
Step 3:
With the two calibration points P1 and P2, the calibration coefficients m0 and m1 can be
determined for the specific material (see next page).
Step 4:
The coefficients m1 = 0.0581 and m0 = -4.05 (see next page) for the calibration curve Cal14
can be entered directly by hand and are stored in the probe by pressing the bu
tton “
Set
”. The name of
the calibration curve can also be entered by hand. The selected calibration curve (e.g. Cal14) which is
activated after switching on the probes power supply will be adjusted with the button "
Set Default
Calib
”.
Attention:
Use “dot” as separator (0.0581), not comma !
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