Projected Capacitance (Also known as P-cap or Pro-cap) is a solid-state technology. Instead of being based on electric resistance, it relies on electrical capacitance.
If the charge is applied to the conductor, it will hold the charge. And then second conductor is brought near it, second conductor will “steal” some of the charge from first one. Stealing a charge is same as when walk on carpet and try to touch any metallic thing you feel some spark at the tip of your finger. Here, metallic thing that you are trying to touch steals charge, which was built during walking on carpet. Pro-cap technology works on this basic principle.
Like resistive design, Pro- cap sensors uses two layers of transparent ITO conductors, separated by an insulator. The conductors on one layer run right angle to the conductors on other layer. The separated conductors are scanned in rapid sequence, so that all the possible intersections are measured many times per second.
When you touch the screen with your finger, it steals a little bit of the charge from each layer of the conductors at that point. The electrical charge involved is very tiny, which is why you don’t feel any shock or spark. This little change in the charge is enough to be detected by electronic devices. Because each conductor is checked separately, it is possible to identify multiple simultaneous touch points.
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| Pro-cap Touch Technology |
Today’s projective capacitance technology relies on the fact that an electromagnetic field project above the plane of the conductive sensor layer. It allows to cover the touch module with sheet of thin glass or specially toughened Gorilla Glass, without losing the sensitivity of screen. It also increase the reliability of mobile.
No technology is without its challenges, so as the Pro-cap. The system of conductors used is susceptible to electrical noise from electromagnetic interference (EMI). Also touch screen won’t respond to non-conducting materials like finger nails.
In spite of all these shortcomings, Pro-cap technology has become dominant choice for the mobile devices.
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