Diagram: Surface Capacitive Technology

Surface Capacitive

Sensor Materials

Glass substrate, transparent metal oxide coating

Principle of Operation

  • Voltage is applied to the corners of the touch screen.
  • A pattern of electrodes around the periphery of the touch screen distribute the voltage to form a uniform electric field across the conductive surface.
  • A finger touch draws a minute amount of current from the surface and is measured by the controller.
  • The relative magnitude of current is inversely proportionate to the distance from the contact point to the touch screen corners.
  • Ratios of the four corner currents are calculated to determine the X,Y coordinate.

Advantages

  • Withstands contaminants and moving liquids on the screen, and continues to function over entire touch screen area
  • Very light finger touch required for activation
  • Technology with fastest touch response time
  • Transmission typically 88% to 92%

Disadvantages

  • Supports only finger or tethered pen
  • Severe scratch can affect operation within the damaged area
  • Limited to 1 resolvable point with gesture capability