Touch panel
From Wikipedia, the free encyclopedia
A touch panel is a display device that accepts user input by means of a touch sensitive screen. Because of their compact nature and ease-of-use, touch panels are typically deployed for user interfaces in automation systems, such as high-end residential and industrial control. Touch panels are also becoming common on portable computers such as Tablet PCs, Ultra-Mobile PCs and consumer devices such as VOIP phones.
The most common types of touch panels are resistive, capacitive and surface wave.
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[edit] Resistive
A resistive touch panel is composed of several layers. The most important are two resistive layers separated by thin space. When some object touches this kind of touch panel, the layers are connected at certain point; the panel then electrically acts similar to two voltage dividers with connected outputs. When measuring press force, it is useful to add resistor dependent on force in this model -- between the dividers.
A resistive touch panel can be made with either four or five wires. The positions of the conductive contacts in resistive layers differ depending on how many wires are used. When four wires are used, the contacts are placed on the left, right, top, and bottom sides. When five wires are used, the contacts are placed in the corners and on one plate.
[edit] Capacitive
A capacitive touch panel must be touched by hand or other conductive objects. Contact with a conductive object results in changed capacitance based on capacity measurement.
[edit] Surface wave
In a surface wave touch panel, ultrasound wave travels through a glass surface and is absorbed by touching object.
