VM Series Maintenance and Safety Manual 704-0212-209 Machine Components 1- 29
A Max console is pictured below:
Figure 1–9. Max Control Console
Touchscreen and Touchscreen Controller
The touchscreen is a passive device consisting of a glass substrate and two layers of
silver-ink screened polyester film separated by microscopic plastic spacers. The silver is
thinly and precisely applied so that the silver ink has a consistent sheet resistance.
When the operator applies pressure to the outer polyester film, the silver ink planes
contact each other, momentarily completing a pair of voltage dividers. During that brief
period the touchscreen controller applies a DC voltage between the top and bottom bus
bars on the front silver ink plane. The touchscreen controller then reads the voltage level
from the rear plane to determine vertical position.
During the second half of the scan cycle, the controller applies a differential voltage
horizontally across the rear plane, then reads its voltage or horizontal positions from the
front layer. This scan cycle occurs several hundred times per second and screen
coordinates are digitally filtered before they are transmitted via RS232 to the host CPU
and driver software.
The driver software has a built-in utility that the Service engineer uses to calibrate the
touchscreen at machine installation. This procedure can be repeated by the operator as
necessary.
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