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Detection Features
Apart from double sheets DoubleSense can detect
a number of situations described in the table
below. The effect may be that other sensors can
be replaced by DoubleSense, such as for example
photocells for paper edge recognition and many
others.
| Double Sheet |
The paper is twice as thick
or twice as dark as the calibrated paper.
Example 1: Calibrated on 2 paper layers a
double sheet is 4 paper layers. Example 2:
Calibrated on a blank sheet a double sheet
is a coloured sheet, i.e. wrong paper. |
| Paper Jam |
The presence of a paper in the
sensor when it is not expected to be there
(damaged paper, overlapped paper). |
| Missed Sheet |
The absence of a sheet in the
paper feeding process. |
| Layer Error |
One (1) missing layer out of
two (2), equal to twice as high opacity as
the calibrated value. Example: The sensor
calibrated on two (2) paper layers and one
of the following sheets had only one (1) layer. |
| Paper Present |
The presence of a paper in the
sensor, from lead edge to trail edge (photocell
function). |
| Calibration Errors |
Paper stand-still, paper pass
time too fast (< 40 ms) or too long (>5 sec),
paper too dark or too thick or extended calibration. |
| Pass Time Variations |
Paper speed 67% of previous
paper speed.
Paper speed 150% of previous paper speed.
Paper speed 10% of calibration paper speed.
Paper speed 10 times the calibration paper
speed.
Paper present for more than 5 seconds (paper
stand-still). |
Opacity recognition
The infrared throughbeam sensor is advantageous
in paper layer detection because of the strong
effect it delivers, as opposed to the fibre optic
type. Thicker and darker materials can thereby
be detected without any drawbacks.
The opacity – light reduction - varies on a printed
paper, from moderate reduction on white areas
to stronger reduction on black areas. DoubleSense
treats these variations with an intelligent processing
and is therefore able to deliver a 100% reliable
detection result on a coloured paper.
DoubleSense is able to detect double sheets on
a wide range of printed papers. From thin paper
thickness’ such as a 20 g/m2 coloured plastic
film or bible paper, up to a 1000 g/m2 white cardboard.
Bundles of papers, e.g. leaflets and folded papers,
can also be double detected. Depending on how
dark the printed colours are, DoubleSense can
double detect leaflets from 2 up to 10 sheets.
Thinner paper material as well as folded sheets
are often subject to feeding malfunctions such
as double or damaged sheets. Should the material
however be too thick or too dark to beam through
the sensor will continue to detect all other errors
than doubles described in the table to the left.
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