Touch Panel

Characteristics

Infrared:

  1. Very resistant
  2. Used for bigger displays in the outskirt area (e.g. cash machine)
  3. No abrasion due to use
  4. Can be operated with finger (gloved), as well as with stylus

Resistive:

  1. Very precise
  2. Used for smaller displays
  3. Flat construction (few millimeters)
  4. Cheap production
  5. Can be operated with finger (gloved), stylus etc.

Capacitive:

  1. Less abrasion than resistive touch panels have
  2. Very percise
  3. Flat construction (few millimeters)
  4. Can be operated with bare finger or conductive stylus

Working principle of the different technologies

Infrared:

A frame around the glass sends out infrared rays, which form a grid over the glass surface. When using the panel, the grid is being interrupted and the touch points coordinates are calculated from this interruption. Based on the robust construction, this sort of touch panels are usually used for systems in public places (ticket- or cash machines).

Resistive:

Analog Resistive Touch Panels consist of two transparent layers, the bottom layer is made of glass and the top layer is a flexible synthetic film. When touched, the two layers get in electric contact. The controller calculates the coordinates of the touch point based on voltage change. As resistive touch panels are very precise and can be operated with gloved finger, they are suitable for various devices, such as PDAs, route guidance systems and medical equipment.

Capacitive:

A transparent, conductive coating is added to the glass surface. Voltage is added to the corners, which builds an electric field. When the finger touches the glass, it absorbs some of the voltage. The controller uses the voltage change to calculate the coordinates. This working principle allows operating with bare finger or conductive stylus only. The advantage of capacitive touch panel is that they are more resistant against rough handling than resistive panels are. At the moment they are mainly used for recent mobile phones.