Hydronix Hydro-Control VI, Operator'S Manual

Page: 43 / 88

Chapter 8 Using Moisture Control
Hydro-Control VI Operators Guide HD0456 Rev 1.7.1 43
For a good calibration it is important for the sensor signal to be as stable as possible during the
averaging periods at the end of both the dry and wet mix times. The stability of the signal can
be improved by extending the mix time to allow time for the mix to become homogenous. For
the best calibration, the deviations should be as close to zero as possible, always less than 3
unscaled units and preferably less than 0.5 unscaled units.
When planning to use a mix for calibration it may be necessary to temporarily extend mixing
times to investigate how the signal changes over time. After the calibration has been
completed, the wet mix time can be reduced for actual plant operation. It is important to note
that this can affect the quality of the mix produced.
CALC mode can be done in either the pre-wet phase, the main phase or during both phases.
2.3
CALC Mode – Main Water
This is the most common place to use Calc mode. This is for mixes where after addition of pre-
wet water and cement, a stable dry mix and wet mix reading can be obtained. The calibration
made based on the dry and wet readings is used for the pre-wet phase also. If initial or pre-
wet mix phases are used before cement is added the moisture reading during this period may
be invalid. This is commonly not a problem as in most circumstances only the moisture of the
finished mix is of concern.
2.4
CALC Mode – Pre-wet Water
In some cases it is possible that after addition of certain admixtures (usually SCC admixtures)
that the wet mix reading is out of the measurement range of the sensor. In situations where
materials, such as metal fibres, are added during the dry mix the sensor may no longer be able
to give reliable readings. In such cases it is possible to calibrate the mix based on the initial
mix reading, the pre-wet water and the pre-wet mix reading. The pre-wet water added is usually
the amount of water required before addition of the admixture.
2.5
CALC Mode – Pre-wet + Main Water
This mode can be used if an accurate moisture is required at all points throughout the cycle. It
is the longest method of addition and so would only be used where quality tracking throughout
the mix is necessary and time constraints are low.
2.6
CALC Mode – Main using pre-wet value
In some cases, once cement is added it can take a long time for the mix to homogenise to the
point where a stable dry mix reading can be taken for calculating the required water. In such
cases it is common that prior to adding cement a stable reading can be obtained quite quickly.
In this method of calibration a stable pre-wet mix is required but a stable dry mix is not
2.7
CALC Mode – Pre-wet and Main using pre-wet value
This mode allows the user to calculate both the pre-wet water. It also allows the main water to
be calculated from the pre-wet mix value in the situation where the dry mix does not stabilise
quickly.