Technologies of Touch Screen

Surface Capacitive

Structure

Transparent conductive coating is on the base glass sheet, and glass protective coating is placed over it. Electrodes are placed on the four corners.

Structure looks very simple. How does it sense the touched points?

I am getting to it.

Sensing Method

The same phase voltage is imposed to the electrodes on the four corners, then a uniform electric field will be forming over the panel. When a finger touches on the panel, electrical current will flow from the four corners through the finger. Ratio of the electrical current flowing from the four corners will be measured to detect the touched point. The measured current value will be inversely proportional to the distance between the touched point and the four corners.

Features

  • Surface capacitive technology is suitable for large size monitors.
  • Surface capacitive sensor can respond to light touch, and no pressure force is needed for detection
  • Visibility is high because structure is only one glass layer.
  • Surface capacitive is structurally tough as it is made of one sheet of glass.
  • Surface capacitive does not get affected by moist, dust, or grease.
  • Parallax is minimized in surface capacitive.
  • Surface capacitive has high resolution and high response speed.
  • Basically, surface capacitive can detect touches by fingers only. It does not detect input by gloved hand. Some surface capacitive touch screens may detect touches by thin-gloved hand, but they do not support the combination use of bare finger and gloved finger. Some surface capacitive touch screens support pen writing, but they usually does not support combination use of finger touch and pen writing.
  • Surface capacitive technology does not support multi-touch.
  • Surface capacitive touch screen is likely to be affected by noise. Recently, tolerance for noise has been improved with various methods such as noise shielding.
  • Surface capacitive touch screens tend to be employed for applications that are large size (over 12inch), used by general public, and requiring high-quality looking, high resolution and high durability. They are used on ATM, ticketing machine, kiosk, POS, office automation, factory automation, arcade games, and medical and food industry. Surface capacitive touch screens are especially popular in amusement fields such as casino gaming due to its high durability and visibility.
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