Hardware
Device Description Embedded HMI XVH-3x0
Notes on the Touch Screen
01/05 AWB2776-1559GB
© by Moeller GmbH
25
11 N
OTES ON THE
T
OUCH
S
CREEN
11.1 I
NFRA
-R
ED
T
OUCH
Basic touch screen function
The touch screen operates using an active light matrix in the infra-red 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. A touch on the screen is detected by the
simultaneous interruption of one or several channels on the X or Y axis.
Repeated touch actuations and those that cover an area greater than 20 mm x 20 mm are not
evaluated by the touch 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.
Function test
A function test of the touch screen is permanently active. 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
TOUCH ERROR
LED (flashing). 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. The touch screen, however, remains fully functional.
Only a further 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 touch activated.
Cleaning the Touch Screen
For proper operation ensure that the signal levels of the channels are not so severely reduced or
interrupted due to excessive contamination through dirt.
Clean the inside of the plastic frame on the device front 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 destroy the plastic frame and
foil (frame material: polycarbonate (PC); Foil material: polyester (PET); Display pane: non-reflective
glass; Carrier plate: aluminum).
