Ultrasonic Double Sheet Monitor UDC-18GMA-400-3E2
Description of sensor functions
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Subject to reasonable modifications due to technical advances.
Copyright Fuchs, Printed in Germany
Fuchs Group • Tel.: Germany (06 21) 7 76-0 • USA (330) 4 25 35 55 • Singapore 7 79 90 91 • Internet http://www.pepperl-fuchs.com
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Description of sensor functions
The ultrasonic double sheet monitor is used in all situations in which the au-
tomatic distinction between single and double sheets is required in order to
protect machines or avoid waste production. The double sheet monitor is
based on the ultrasonic through-beam principle. The following can be detec-
ted:
• No sheet, i. e. air
• Individual sheet
• Double sheet or multiple sheets (no distinction can be made for the num-
ber of sheets)
A microprocessor system evaluates the signals. The appropriate switch out-
puts are set as a result of the evaluation. Changes in ambient conditions such
as temperature and humidity are compensated for automatically.
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Working principle
The measuring principle of the double sheet control is based on measuring
and evaluating the transmitted sound amplitude through a sheet of paper. If
there is no paper, no sound is absorbed and the received signal reaches its
maximum level. If there are two sheets of paper, one on top of the other, al-
most all of the signal is absorbed due to multiple reflection between the layers.
The amplitude of the signal passing through thus reaches a minimum level.
The thicker or denser a given type of paper is, the lower the portion of sound
that will pass through it according to the working principle. Because of this,
the functionality of the double sheet control is limited to types of paper that fall
within a specific range. Paper that is too thin allows too much sound to pass
through so that it is not sufficiently different from air. On the other hand, paper
that is too thick absorbs so much of the sound that the amplitude for single
sheets is already in the range of a double sheet.
Therefore, the double sheet control offers the user 4 different programs for
different ranges of material, making it possible to adjust to the ideal setting for
different applications. There is no need to perform TEACH-IN for single sheet.
This makes the product more user-friendly. Fluttering movements of the pa-
per do not affect reliable operation of the DSM.
