Volkswagen RNS 510, Руководство пользователя

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The horizontal and vertical monitor coordinates are
determined based on the principle of the voltage
divider. Another example of this functioning principle
is the potentiometer.
To clarify the procedures taking place in the touch-
sensitive layer of the touch screen, we will break down
the process into two steps:
- measurement in horizontal direction and
- measurement in vertical direction
Measurement in horizontal direction
The touch screen controller first applies a voltage
of 5 volt (U
x total
) to the rear indium tin oxide layer so
that a current flows through this coating in horizontal
direction (X-direction).
The total path between the two voltage poles has a
fixed resistance R
x
.
When the touch screen is touched, an electrical
contact is created from the front to the back layer.
The contact point divides the total resistance between
the two voltage poles of the rear coating into the two
part resistances R
x1
and R
x2
. The controller now
measures the voltage U
x2
at part resistance R
x2
with
the help of the top coating. The controller uses
the measured voltage to calculate the value for the
distance from the touch point to the edge of the
monitor and thus determines the X-coordinate of the
touch point on the screen.
Voltage division
U
x total
Touch point
R
x2
R
x1
U
x2
Part resistances
Measured
voltage U
x2
at
resistance R
x2
Coordinates
calculation
Output
Controller
Monitor
Screen
coordinate in
X direction
Front
indium tin oxide
layer
Back
indium tin oxide
layer
U
x total
R
x
Front
indium
tin oxide
layer
Back
indium tin oxide
layer
Touch
point
X
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