Datasheet

 2009-2012 Microchip Technology Inc. Preliminary DS41393B-page 9
AR1000 SERIES RESISTIVE TOUCH SCREEN CONTROLLER
2.4 8-Wire Sensor
An 8-wire resistive touch sensor consists of a stable
and flex layer, electrically separated by spacer dots.
The layers are assembled perpendicular to each other.
The touch position is determined by first applying a
voltage gradient across the flex layer and using the
stable layer to measure the flex layer’s touch position
voltage. The second step is applying a voltage gradient
across the stable layer and using the flex layer to
measure the stable layer’s touch position voltage.
The measured voltage at any position across a driven
axis is predictable. A touch moving in the direction of
the driven axis will yield a linearly changing voltage. A
touch moving perpendicular to the driven axis will yield
a relatively unchanging voltage.
The basic decoding of an 8-wire sensor is similar to a
4-wire. The difference is that an 8-wire sensor has four
additional interconnects used to reference sensor
voltage back to the controller.
A touch system may experience voltage losses due to
resistance changes in the bus bars and connection
between the controller and sensor. The losses can vary
with product use, temperature, and humidity. In a
4-wire sensor, variations in the losses manifest them-
selves as error or drift in the reported touch location.
The four additional sense lines found on 8-wire sensors
are added to dynamically reference the voltage to cor-
rect for this fluctuation during use (See Figure 2-2).
FIGURE 2-2: 8-WIRE DECODING