Novomatics Operation Manual
AlphaTackPlus
28
8.2.
Definition of variables
The AlphaTackPlus measurement system operates with a set of independent and dependent
variable. Independent variable can be defined in a measurement program and will apply to
the sample during the measurement. The dependent variables will be quantified during
measurement and depend on sample itself and applied independent variables. For example:
The measured peak tack is up from the ink itself on one hand but also from the applied roller
speed on the other.
WinAlphaTack distinguishes also between
process
and
tackscan
variables.
Process variables characterize the current state of sample and measurement independent of
a certain position on roller surface.
In opposite to this tackscan variables describe the current of sample in dependence on a
certain roller position and under the applied process conditions.
A fourth variable characterization is process value and set point for independent variables. A
set point is the physical value that must be achieved (for example. set point temperature has
been set to 30.0 °C). The process value is the real value measured by the instrument (for
example, measured temperature on roller surface 29.9 °C).
8.2.1.
Independent Variables
Time [s, min]
Indicates the time since start of measurement.
Temperature [°C, °F, K]
Indicates the temperature of measurement roller surface. The measurement roller contains a
PT 1000 temperature probe that is placed very close to roller surface. This arrangement
grants a smallest temperature difference between surface and probe. For details please refer
to
temperature control system
.
The postfix SP defines the set point of temperature (the value that has to be achieved). The
postfix PV defines the process value of temperature (the real temperature value).
Roller Speed [rpm, m/min, m/s, km/h]
The gearless electronic driving system allows the step less adjustment of speeds. It is
defined in rotations per minute. The equivalent surface speed is calculated by the roller
diameter.
The postfix SP defines the set point of roller speed (the value that has to be achieved). The
postfix PV defines the process value of roller speed (the real speed value).
Line Force , Integral Pressure[N/m]
The line force variable indicates the applied force between upper elastomer roller and
measurement roller. It is expressed relatively to the roller length. This makes this variable
independent of real roller length and simplifies the comparability to the situation on press.
The postfix SP defines the set point of line force (the value that has to be applied). The
postfix PV defines the process value of line force (the real line force value).
