Projected capacitive touch (PCT; also PCAP) technology is a variant of capacitive touch technology but where sensitivity to touch, accuracy, resolution and speed of touch have been greatly improved.
This intelligent processing enables finger sensing to be projected, accurately and reliably, through very thick glass and even double glazing. PCT touch screens are composed of thousands of discrete keys, but most PCT touch screens are made of an x/y matrix of rows and columns of conductive material, layered on sheets of glass.
This can be done either by etching a single conductive layer to form a grid pattern of electrodes, by etching two separate, perpendicular layers of conductive material with parallel lines or tracks to form a grid, or by forming an x/y grid of fine, insulation coated wires in a single layer. The number of fingers that can be detected simultaneously is determined by the number of cross-over points.
The conductive layer is often transparent, being made of Indium tin oxide (ITO), a transparent electrical conductor. In some designs, voltage applied to this grid creates a uniform electrostatic field, which can be measured. When a conductive object, such as a finger, comes into contact with a PCT panel, it distorts the local electrostatic field at that point. This is measurable as a change in capacitance.
If a finger bridges the gap between two of the “tracks”, the charge field is further interrupted and detected by the controller. The capacitance can be changed and measured at every individual point on the grid. This system is able to accurately track touches.