PCAP Touch Screens – How they Work, How they are Constructed and Customization

CDS has a new and expanded range of PCAP touchscreens and explains here how they work and highlights the possible customisation.



HOW PCAP Touchscreens Work?

A Projected Capacitive Touch (PCT; also PCAP) technology consists of an insulator such as glass, which is coated with a transparent conductor, like ITO (indium tin oxide). The user’s finger conducts electricity, so touching the surface of the screen results in a distortion of the screen’s electrostatic field; that distortion is measurable as a change in capacitance.

In other words, a capacitance-based sensor is a circuit designed to sense touch by coupling with the electrical fields; touch causes the capacitance of the circuit to change.

Different technologies may be used to determine the location of the touch; the location is then sent to the controller for processing. The way Apple describes it, the process is fairly straightforward:

  • Read output from sensing points, producing and analysing the touch data
  • Then compare the current data to past data and perform actions based on the comparison
  • Additionally, receive and filter the raw data, generate gradient data, calculate boundaries and coordinates for each touch region, performing multipoint tracking.


Projected Capacitive Touch (PCT) Screen Construction

PCAP screen construction

A capacitive touchscreen sensor consists of a large array of indium tin oxide (ITO) conductors on one or more layers of glass or polyethylene terephthalate (PET) plastic.

The good optical clarity and low resistivity of ITO make it the overwhelming choice for this very sensitive circuit.


Projected Capacitive Touch (PCT) Screen Layers

PCAP screen layers

On top of the display screen, but before the touch sensor is added, is placed an insulating material to avoid interference from capacitive noise to optimise the touchscreen performance. Particularly if a metal bezel is used, an additional insulator is needed for the same reason.


Customized Multiple Colour Cover Glass as well as Corporate Logos

custom pcap image

You are no longer limited to black-and-white printing on glass and CDS we can take your custom orders for Projected Capacitive Multi Touch Displays, with colour and logos printed directly onto the glass.


For more information please go to: https://crystal-display.com/products/pcap-touch-screen-overlays/ or contact us on info@crystal-display.com or call our main office on +44 (0)1634 327 420.