Touch Screens

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Touch Screens

Post  admin on Fri 23 Jul 2010, 2:50 am

Touch screens enter data by detecting the touch of the user’s finger, and usually responds as if this was a mouse click. Clear touch screens may be attached to the front of a notebook or desktop computer screen, or even to a large plasma screen. There are also electronic whiteboards that can interact with the user's touch as do computer touch screens.

There are three basic systems that are commonly used in touch screens
• Resistive – Consists of a glass layer covered by a conductive and a resistive metallic layer. An electric current runs through the two layers. When a user touches the screen the screen the metal touches the glass, and the change in electric current at that spot is registered. The coordinates of that point are calculated, and the touch is converted; usually into a mouse click.
• Capacitive – Uses a layer that stores electrical charge on top of the glass panel. When a user touches the monitor some of the charge is transferred to the user, so the charge on the layer decreases. This decrease is measured in circuits located at each corner of the monitor. The computer calculates, from the differences in charge at each corner, exactly where the touch event took place. The system then transfers the touch in a similar method to the resistive system.
• Surface acoustic wave- This technology uses ultrasonic waves that pass over the touch screen panel. Two transducers (one receiving and one sending) are placed along the monitor’s glass plate. Reflectors are also placed on the glass to reflect an electrical signal sent from one transducer to the other. The receiving transducer can tell if the wave has been disturbed by a touch event and can locate it. The surface acoustic wave system allows for 100% of the light through, resulting in the best image clarity.


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