then the sum of the two sensors would be the web width. If the two sensors overlap each other if they have
a gap between them, then the offset is either negative or positive. Hence the measurement width would be
the sum of web covered by each sensor plus the offset.
NOTE:
If both the sensors are in the same orientation the width measurement would still work but the
display on the front screen would show both edges moving in the same direction with a black gap in the
middle.
NOTE:
If sensing mode is contrast, the two sensors have to be positioned a certain way to get the correct
contrast width measurement. Please consult the factory for more detailed documentation for such an
installation.
Teaching
When the user presses the teaching wand, the controller will automatically calculate the offset based on the
raw sensor(s) measurement at that instant. The offset is computed by subtracting the raw sensor(s)
measurement from the nominal width.
In order to record the correct offset the user should present a web of known width (preferably the known
width is equal to the nominal width) at the desired working distance from the sensor(s), ensuring that both
edges of the web are seen by the sensor(s). If that known width is different from the nominal width, then that
value can be entered as the nominal width before pressing the teaching wand. As soon as the wand is
pressed, the controller will calculate the offset. If the nominal width is different from the known width used
for teaching, then the appropriate nominal width can be reset.
NOTE:
When the teaching wand is pressed the controller will compute the offset using this equation:
offset = nominal width - raw measurement from the sensor(s). The offset is not shown on the display
however the measurement width will be shown. Since the measured width is offset plus the raw
measurement from the sensor(s), the measured width will be the same as the nominal width (if the web is
stationary).
WARNING:
Pressing the teaching wand will reset the offset based on the current measurement.
NOTE:
The offset can be reset to zero by pressing the teaching wand when no web is in front of the
sensor(s).
Output Type
When an analog output is used for width measurement, the analog output type can either by the absolute
width measurement or the error in width measurement. Pressing the button will toggle the state between the
absolute and error output.
Absolute
When the output is set to absolute, the digital width measurement displayed on the home screen will
provide the measured width value in mm. The analog output on the other hand would be scaled to range
from null scale to full scale based on the range of the sensor and the range of the analog output. For
example, with a 48 mm sensor a web width of 24 mm would have an analog output value of 5 V if the analog
Content subject to change without notice
SCU5: Sensor and Web Guide Controller User Manual v 3.6| Page 34
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