Kapazitiv
Touchscreen Kapazitive Technologie

Surface capacitive - Projected capacitive

More information Surface Capacitive
Projected Capacitive

Capacitive touchscreens can basically be divided into two broad categories:

  • Surface capacitive

  • Projected Capacitive

Projected capacitive technology is not based on pressure detection, but detects touch by measuring the electrical capacitance at each addressable electrode.

The mere touch of the surface is enough to operate the touch screen. When a finger approaches an electrode, its electromagnetic field is disturbed, as a result of which the electrical capacitance changes and is measured by the electronics.

The projected capacitive technology can support one, two or more touch points (single, dual and multi-touch touchscreens) in its various versions.

Surfaces Capacitive touch systems

In the case of surface capacitive touch screens, several techniques are available.

In the sandwich film layer construction, a conductive ITO layer is applied to the front of the touch sensor. The ITO layer is a transparent metal oxide coated film that is laminated onto glass, e.g. as in the patented GFG version.

An alternating voltage applied to the ITO layer generates a constant, uniform electric field. When touched, there is a low charge transport, which means that the position of the contact point can be measured exactly and passed on to the controller for processing.

Projected Capacitive Touch Systems

In projected capacitive touch panels, the conductive ITO layer is lamented to the back of the glass and uses two layers with a conductive pattern. The two levels are isolated from each other, with one plane serving as a sensor and the other level as a driver.

In the case of projected capacitive touchscreens, a countercapacitance is deliberately built up between the elements of rows and columns located in the vicinity of the individual intersections. If a finger is at the intersection of two strips, the capacitance changes and a stronger signal arrives at the receiver strip.

The sensor is mounted on the back of the cover glass and the ITO layer projects the capacitive field through the glass pane.

The PCAP technology supports the detection of multiple contact points simultaneously, making multi-touch possible.

Advantages of capacitive technology

Due to the technology, you don't need any force to trigger a touch event. As a result, the touch is very fast and easy to use and enables multi-touch functionality.

Another advantage of operation without pressure is that the surface is not exposed to mechanical effects and therefore practically does not wear out.

Also, surface contamination has no influence on usability and functionality, which is why PCAP touchscreens are an ideal solution for touchscreen applications that are publicly accessible or used under extreme environmental conditions.

However, touchscreens with capacitive technology can only be operated with gloves to a limited extent. Operation with thick or non-conductive gloves is not possible with mutual-capacitance systems.

On the other hand, unrestricted operability is possible with conductive or thin latex gloves, which are used, for example, in medical or food processing areas.