Device Description MV4-570-TA1/2, MV4-590-TA1/2 2-16
Moeller 07/01 AWB-C2700-1347GB
9 The Touch Screen
9.1 Basic function of the Touch Screen
The function of Touch Screen is based on the active light matrix principle in the infrared range. The optical
elements of the light matrix are located behind the IR transparent plastic frame in the front of the device.
They are located in such a way that their radiation extends slightly out of the front plate. Each emitter is
assigned a receiver that is located on the other side. In this way a total of 70 IR channels are arranged
closely together. A touch on the screen is detected by the simultaneous interruption of one or several
channels in the X or Y axis.
Repeated touches and touches that cover an area greater than 20 mm ⫻ 20 mm are not evaluated by the
touch controller. Continuously interrupted channels caused by severe contamination and dirt, or by the failure
an optical element, are detected by the touch controller and are no longer included in the evaluation.
9.2 Power up function test
The device runs through a function test of the Touch Screen with every start-up. All the IR channels are
evaluated and their signal levels compared with those of the initial values. The initial values are determined
before the device is delivered and stored in a retentive memory.
If one or several channel signals is below a minimum relative to the initial level, this will be indicated on the
screen with an error message and the
DEF/DIRTY
LED will be lit (see Section 10). A reduced signal level of
this kind is normally due to severe contamination of the IR transparent plastic frame which consequently has
to be cleaned (see Section 9.3). The Touch Screen, however, remains fully functional.
Only an increase in the contamination of the screen will lead to the continuous interruptions of one or several
IR channels. IR channels that are continuously interrupted will be detected by the touch controller and no
longer included in the evaluation. In extreme cases, this may mean that individual zones cannot be activated
by touch.
CAUTION ! Do not touch the screen whilst the system is being started up,
and wait till your application has started.
The Touch Screen carries out a function test during the start up in which
the signal levels of the IR channels are measured.
9.3 Cleaning and care of the Touch Screen
For operation ensure that the signal levels of the channels are not so severely reduced or interrupted due to
excessive contamination through dirt (see Section 9.1).
Clean the inside of the plastic frame of the device regularly with a damp soft cloth. Ensure that the surface is
not scratched or scoured, especially when removing hard deposits and abrasive dusts.
Do not expose the front of the device to solvents which may corrode and loosen the plastic frame (frame
material: polymethylmethacrylate, PMMA).
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