Device Description MV4-670-TA1/2, MV4-690-TA1/2 3-25
Moeller 07/01 AWB-C2700-1347GB
17 Touch Screen
17.1 Basic Touch Screen function
The Touch Screen operates 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 panel of the device. They are
located in such a way that their radiation extends slightly out of the front pane. Each emitter is assigned a
receiver that is located on the other side. In this way 70 closely positioned IR channels are provided on the
10.4” unit and 96 IR channels on the 15” unit (→ Section 21). 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 x 20 mm are not evaluated by the
controller. Continuously interrupted channels caused by severe contamination and dirt, or by the failure of an
optical element are detected by the touch controller and are no longer included in the evaluation.
17.2 Power up function test
The MV4-600 carries out a function test of the touch screen with each power up of the device. This test
measures the signal levels of all IR channels and compares them with initial signal values. The initial values
are determined before the device is delivered and stored in a retentive memory.
If the signal of one or several channels is below a minimum level relative to the initial values, this will be
indicated by an error message on the screen and the flashing of the
DEF/DIRTY
LED (→ Section 16). 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 (→ Section 17.3). The Touch Screen, however, remains fully
functional.
Only an increase in the contamination of the screen will lead to the continuous interruption 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.
Do not touch the screen whilst the system is being started up, and wait till your
application has started.
During the startup the touch screen carries out a function test in which the signal
levels of the IR channels are measured.
17.3 Cleaning and maintenance 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 (→ Section 17.1).
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 dust.
Do not expose the front of the device to solvents which may corrode and dissolve the plastic frame
(frame material: polymethylmethacrylate, PMMA).
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