Touch Technology: Surface Capacitive

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.

Illustration 1: Surface Capacitive

Pros and Cons

ProsCons
Withstands contaminants and moving liquids on the screen and keeps working across the entire touchscreen surfaceSupports only finger or tethered pen
Very light finger touch required for activationSevere scratch can affect operation within the damaged area
Technology with fastest touch response timeLimited to 1 resolvable point with gesture capability
Transmission typically 88 % to 9 2%

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