It is quite likely that your interest in touch was first awakened after seeing an implementation of capacitive touch.
For changing displays and interacting with electronics and machines, touch has many great solutions, but if very precise measurements of multiple finger movements are necessary, capacitive is the technology of choice.
This article should answer some basic questions about how capacitive touch works—future articles will focus on finer details of implementation. If you have questions about implementing capacitive touch, we at Cirque would definitely enjoy discussing ideas with you.
An ASIC then charges and monitors the grid. As charge is pulled by a finger(s) from an area in the grid, the ASIC is made aware of the location of the finger, which then gets interpreted into a mouse cursor position or point of touch on a touchscreen.
Sensors using projected capacitive technology can be tuned to sense a finger or another capacitor that is not touching the surface. This also allows more layers on top of the sensing surface or thicker materials that can better handle vandalism and extreme conditions.
Because a grid is involved it is possible to sense the presence of more than one finger. The grid's sensing of both and X and Y coordinates also increases the accuracy of projected capacitive.
Where you've seen
You are seeing projected capacitive sensors everywhere. It is in the trackpad on your laptop and in most of the high-end touchscreen cell phones. It is in the screens of tablet computers, and as TouchAdvance readers likely know, it may be in the restaurant you're eating at this evening.
What's still missing from this report
As with most feats of electronic engineering, capacitive touch goes much deeper than can be covered in one article.
Projected capacitive can be broken down into two different methods: mutual capacitance and self-capacitance. These subjects should be explored on TouchAdvance soon.
The differences of projected and surface capacitive are highlighted fairly well, but the detailed intricacies of the underlying components will be left for another article.
* Depending on tuning, the finger does not have to actually contact the surface for projected capacitive to sense the finger's location.