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| Advanced Touch Screen
Technology |
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| Touch screen technology has the
potential to replace most functions of the mouse and keyboard. As
the technology advances, people may be able to operate computers
without mice and keyboards. Because of its convenience , touch
screen technology solutions has been applied more and more to
industries, applications, products and services, such as Kiosks, POS
(Point-of-Sale), consumer electronics, tablet PC, moderate to harsh
Machine Control, Process Control, System Control/Office Automation
and Car PC, etc. |
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| Nowadays there are four types of
touch screen technologies applied in our life and industries. |
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Capacitive |
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Resistive |
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Infrared |
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Surface acoustic wave
(SAW) | |
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| The capacitive technology is
applied on glass sensor that is added conductive coatings. The
electrical charge is set at the four corners of the glass along an
X-Y axis, and spreads the stable voltage on the glass as a uniform
field. When a user touches the screen, some of the charge is
transferred to the user, and makes the potential difference on the
screen. After the panel controller recognizes that, the controller
will send the X-Y axis information to the PC port. The advantage is
that capacitive technology transmits almost 90% percent of the light
from the screen. The superior efficiency gives capacitive better
than resistive technology. |
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| The resistive technology is applied
on two layers with overlaying a hard-coated ITO on a conductive
clear glass. These two layers are held apart by spacers (dot). When
the flexible layer is touched and contacts the other layer that is
set on the stable glass, the voltage is detected and measured from
same voltage applied as an electrical field. The controller uses
voltage measured from along the X-Y axis to calculate the position
of the touch. The advantage of resistive technology is referred to
the cheap price, but the surface of resistive panel is not solid as
capacitive panel, it cannot sustain strong punches and work in harsh
environment. |
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| The infrared technology is applied
on touch panels that place infrared receivers and CRT utilizing
infrared Light Emitting Diodes (LED) along the horizontal and
vertical X-Y axis. When a user touch the surface of screen, the
infrared emitted from LED beam is broken and receiver transmits X-Y
axis information to the PC port via touch controller. |
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| The surface acoustic wave
(SAW) technology is based on two transducers
(transmitting and receiving) placed for the both of X and Y axis on
the touch panel. The other important element of SAW is placed on the
glass, called reflector. The controller sends electrical signal to
the transmitting transducer, and transducer converts the signal into
ultrasonic waves and emits to reflectors that are lined up along the
edge of the panel. After reflectors refract waves to the receiving
transducers, the receiving transducer converts the waves into an
electrical signal and sends back to the controller. When the user
touches the panel, the user absorbs a portion of the wave travelling
across it. The controller compares and calculates the change of
signal that transducers emits and receives. The calculation
processes for both X and Y axis independently. |
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