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Resistive
Touchscreen
(for 90% of all touchscreen applications)
The resistive touchscreen uses a glass panel overlay with a uniform resistive
coating. A polyester coversheet is tightly suspended over the top of
the glass, separated by small, transparent insulating dots. The coversheet
has a hard durable coating on the outer side and a conductive coating
on the inner side. When the screen is touched, the conductive coating
makes electrical contact with the coating on the glass. The voltages
produced are the analog representation of the position touched. The controller
digitizes these voltages and transmits them to the computer for processing.
Surface
Acoustic Wave Touchscreen (available for 19.1" and 21.3"
displays)
(safest touchscreen for hazardous area applications)
The Surface Acoustic Wave Touchscreen has a glass overlay with a grid
of transmitting and receiving piezoelectric transducers. The touchscreen
controller sends a 5 mHz electrical signal to the transmitting transducer,which
converts the signal into ultrasonic waves within the glass. When the
screen is touched, a portion of the wave traveling across it is absorbed,
thus changing the received signal. The signal is then compared to a stored
reference signal, the change recognized, and a coordinate calculated.
The process happens independently for both the X and Y axes. By measuring
the amount of the signal that is absorbed, a Z-axis is determined.
Infrared
Touchscreen
(for applications where touchscreen is exposed to extreme
abuse)
The Infrared Touchscreen
relies on the interruption of an IR light
grid in front of the display screen.
Integrated into the display bezel is
an opto-matrix frame that contains a
row of IR-light emitting diodes (LEDs)
and photo transistors, each mounted on
two opposite sides to create a grid of
invisible infrared light.The opto-matrix
frame is isolated from the outside environment
by an IR transparent barrier. The IR
controller sequentially pulses the LEDs
to create a grid of IR light beams. When
a stylus, such as a finger, enters the
grid, it obstructs the beams. One or
more of the phototransistors detects
the absence of light and transmits a
signal that is the X and Y coordinates.
Because the infrared scanning is done
in front of the display, a bulletproof,
3/8" thick polycarbonate window is installed
between the IR grid and the display itself.
This window provides a level of environmental
protection for the electronics that is
unique to the infrared touchscreen technology.
Click here to view the Touchscreen Comparison
Chart
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