Touch Screen Systems

Have you ever wondered how touch screens work? Of course we don’t need to know the engineering details which can vary to some degree between specific products, but what is the basic mechanics that allows something like a touch screen laptop to recognize your finger or stylus? In my research there are three basic systems used, although some really cool stuff are being developed using futuristic recognition technology that we won’t go into today.

The first of technique is called the resistive system. It has two metallic sheets of that carries a charge and are separated ever so slightly. When some foreign object touches the screen and forces these two sheets to touch, the change in the electrical field where the contact is made can be calculated by the systems computer.

The second is the capacitive system in which a single sheet carrying a charge is used. When something conductive like your finger or an oppositely charged stylus touches the screen, some of the charge escapes through the contact. Where the charge is decreased is how the system determines the point of contact.

The surface acoustic wave system uses devices along the sides of the screen to reflect electrical current. When your finger interrupts the current, the computer calculates the exact point of contact using x-y coordinates from the sides of the screen.

And there you have it. Who cares right? As users we just want stuff that works well and looks good. Not really, some people have a need to at least have an idea about what is going on. If you are not one of those people, and have a touch screen laptop, then I’m sorry I wasted your time.