AsiaPro Technology
Touch and Sense ASIAPRO
Capacitive Touch
Capacitive touch

How Capacitive Touch Works

The principle of capacitive touches works using body capacitance, a finger touch causes a change in capacitance of the sensor, so that the finger position can be detected and calculated by sensing controller IC, and consequent display or response can be made. Capacitive sensors can either be touched with a bare finger or with a conductive device held by a bare hand. There are two types of capacitive touches, including projected capacitive touch (PCT), which AsiaPro mainly develops, and surface capacitive touch.


Projected capacitive:

There are 2 kinds of patterned sensors structure: single layer and 2 separated layers, both structures support multi-touch and no calibration is needed. They are suitable for small sizes display, can work with protective or decorative cover lens.

Projected capacitance or Projected Capacitive Touch (PCT) technology is a capacitive technology that permits more accurate and flexible operation. It requires 1 single conductive layer to form a grid pattern of electrodes, or 2 layers of separated and perpendicular X-Y array of lines to form the grid of electrode nodes. By applying voltage to the arrays, a grid of capacitors is created. Bringing a finger or conductive stylus close to the surface of the sensor changes the local electrostatic field. The change of capacitance at every individual point on the grid can be measured, it provides precise identification of the position. The use of grid permits a higher resolution and no need to calibrate, it also allows multi-touch operation and suitable for small sizes touchscreen.


Surface capacitive:

It consists of one layer of conductive ITO layer, a small voltage is applied to the layer resulting in a uniform electrostatic field, when a finger touch the screen, a capacitor is dynamically formed and the sensing controller can determine the location of the touch indirectly from the change in the capacitance measured from the four corners of the panel. As surface capacitive is prone to false signals from parasitic capacitive coupling and EMI, it needs calibration regularly. Also, it does not support multi-touch function and not suitable for small sizes touch screen.



Multi-touch sensing technologies

 All Point Addressable(APA) technology:

Independent-matrix sensing method
  • self capacitance(absolute capacitance)
  • 1 layer ITO sensor, independent sensing circuit for every single sensor
  • more sensing lines
  • mutli-touch

    • Intersection-matrix of row and column sensing method
  • mutual capacitance(transcapacitance)
  • 2 layers X-Y matrix ITO sensing patterns
  • driving and sensing lines, scan one by one in sequent order
  • require high speed sensor IC
  • multi-touch


    • Axis Intersect(Profile Based) technology:
  • self capacitance(absolute capacitance)
  • usually diamond shape sensing patterns
  • 2 layers X-Y matrix ITO sensing patterns
  • detect X axis sensor and Y axis sensor to obtain the cordinates
  • multi-touch but appear ghost points, solving by gesture interaction or touching time different methods











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