Capacitive Touchscreens

...response to touch

If elegant design, quality and high surface demands are valued, then the capacitive technology is the right choice.

Among capacitive touch screens, various types are available. Nowadays, most are so-called Projected Capacitive Touches – also known as PCT or PCAP – which increased in popularity with the iPhone.

As durable surfaces are used, capacitive keypads are resistant to wear and scratches. These robust input systems easily withstand ball drop tests.

How does it work?

Control units with capacitive touch screens consist of two isolated, conductive electrodes, generating an electric field. The touch of the surface with a conductive object, usually a finger, causes a voltage change of the electric field. The changed capacity if measured and evaluated by a controller, evaluating the point of contact.

Thus, multiple touches can be detected simultaneously, making capacitive touch screens multi-touch capable and allowing touch gestures such as rotating and zoom.

The advantage of PCT over surface capacitive touches is that the touch sensor may be mounted on the back of the cover glass with the capacitive areas projected through the glass. This principle provides a more durable construction preventing vandalism.

Pros and cons

Pros

  • Multi-touch with up to ten fingers is not a problem on newer models.
  • The capacitive touches exhibit barely any wear and tear.
  • Using better controllers or device-specific programming, the application range and reliability increases tremendously.
  • With the appropriate components, the equipment can be operated in the harshest conditions (vandalism, temperature, humidity).

Cons

  • The equipment can only be operated with bare fingers or with thin latex gloves, but not with heavy work gloves.
  • The conventional stylus is not detected, specific conductive pins have to be used.
  • Electromagnetic fields, moisture or extreme temperature fluctuations can cause malfunctions.

Applications

Due to the innovations in input devices in the consumer sector – smartphones, tablets, etc. – the acceptance of the capacitive technology also increases in other areas. Furthermore, the technology-related deficits – e.g. electromagnetic interference, humidity and temperature fluctuations – can usually be corrected or alleviated through a combination of software and hardware adjustments. Among others, capacitive input devices are now used in the following areas:

  • Smartphones
  • Tablet PCs
  • Industrial-PCs
  • Household appliances (e.g. washing machine / dryer)
  • Control panels (e.g. in public transportation)
  • Input devices in the public sector