Projected Capacitive Touch Screen

Projected Capacitive Touch Screen

A projected capacitive touch screen is typically manufactured with a front layer of glass, with a matrix of conductive elements behind. These elements are made from electrically conductive materials such as Indium Tin Oxide (ITO), Silver, Copper or Carbon – and they are arrayed in an X-layer and a Y-layer (with insulation between).

 

The conductive matrix is connected to a suitably designed touch controller which injects an electrical charge into the matrix and then monitors the various elements of the matrix for changes. When a finger (or a stylus) approaches the front of the touchscreen, there is a minute change in the capacitive field generated within the matrix behind the front glass. The touch controller firmware should then be sophisticated and sensitive enough to detect these changes, identifying the areas or elements of the matrix with the greatest change, and ‘triangulating’ the touch position(s) within the X and Y layers. The controller then transmits this data in the form of X-Y coordinates to the host computer, much in the same way as a mouse or mouse pad (also projected capacitive touch sensing) moves a cursor around a display.

 

There are two types of projected capacitive touch sensing – self capacitive and mutual capacitive. Both have advantages and limitations described in detail elsewhere on our website and in various articles and whitepapers but suffice to say that the benefits of mutual capacitive touch sensing have led it to become the most widely used touch technology in the world.

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