General Hints For Process Security - Roland udk20 Manual

System description
3.2

General hints for process security

The process security of the system is influenced by the following factors:
• the stability of the measuring values
• the setting of under-gauge threshold and over-gauge threshold
• the evaluation of the status signals
Stable measuring conditions will result in stable measuring results. For measuring procedures with
single-sided contacting sensors the air gap between sensor and material surface is a decisive
criterion.
Air gaps varying from measurement to measurement will cause varying measuring results.
Basically, such situations are bad, since in such cases the user is inclined to decrease the under-
gauge threshold and to increase the over-gauge threshold. On doing so, the user puts up with the
drastically increasing risk of not detecting a double sheet.
The following external factors decisively influence the stability of measuring results and need to be
considered for operation of a double sheet detector:
• the air gap between sensor and material surface
• the magnetical characteristics of the material
• the tolerance in material thickness
From this some simple rules derive, which enable a large degree of process security when abided
by:
• Always care for good contact of the sensor with the material!
• Use separate programs to measure different sheet thickness (and alloy)!
• Adjust the switching thresholds as tight as possible!
Furthermore it is necessary that the control checks all status signals of the UDK20, also the
0-sheet signal. While measuring, only the 1-sheet signal may occur. If 0-sheet or 2-sheet occurs,
the measured sheet may not be transported on. In such cases, the sheet will usually be deposited,
re-picked and measured again.
• The control needs to evaluate all status signals !
Checking-up through the 0-sheet signal is to assure that a sheet really is in front of the sensor
during measuring. If 0-sheet occurs while measuring, the measurement is not correct. For example,
a defective sensor holder might prevent the sensor from contacting the sheet. Monitoring the sheet
thickness would then only be performed apparently.
In case of double sheet fatal consequences could then result.
Pos: 21 /Doppelblech/Geräte/UDK20/3 Systembeschreibung/Auswertegerät @ 1\mod_1306753440142_501.doc @ 9300 @ 2 @ 1
22
ROLAND ELECTRONIC GmbH · Otto-Maurer-Str. 17 · DE 75210 Keltern · Phone +49 (0)7236-9392-0 · Fax +49 (0)7236-9392-33
Double Sheet Detector R1000 series UDK20
Manual
B0048991 / Rev. 1.3