Multi-touch with Projective Capacitive Touch
Projective Capacitive Touch (PCT)
PCT (projective capacitive touch) sensors are located behind a glass screen with a thickness of up to eight millimetres to protect them and to avoid wear. The touch sensor is a grid of fine wires or etched ITO semiconductor films, laminated separately, that are working as driving and sensing lines.
An alternating current is induced in the driving lines, providing a capacitive coupling between driver and sensor. Touching the screen with a conductive object, such as a finger, will change the capacity. This in turn allows the touch controller to calculate the touch point coordinates.
A key advantage of capacitive technology is the fact that the touch screen, by design, can recognize multiple touch points simultaneously. The smooth glass surface allows for low-resistance moving and twisting motions and is ergonomically friendly, in particular for distances on larger displays. Another plus is the long service life as the sensors virtually won't wear out. Even scratches in the glass will not impact on the operation.
Method of operation of projective capacitive touch screens
Touch panel and panel PC surfaces without corners and edges can easily be achieved. They are easy to clean which makes them good candidates for hygiene sensitive environments, such as pharmaceutical and food industries or medical engineering. In medicine in particular, many applications need to be operated without applying force. For example, when dimming a surgery light it is vital that the lamp alignment is not accidentally changed.
In addition, working with glass opens up new design options, such as rear side printing or designing customer-specific geometries.Any limitations for use with industrial systems apply mainly to operation. Touch pens need to be conductive, and even gloves must not insulate too much. However, electro-conductive contaminants, such as metal chips or liquids, can impact on the touch functionality.