How Do Touch Screens Work?

by Andy Brock on January 24, 2012

How Touch Screens WorkTouch screens are everywhere today. Like many technologies, they began as a science fiction pipe dream but have become common and ordinary.

Smart phones use touch screens, as do the many new tablet computers being released onto the market today. However, although using these screens is typically quite simple and intuitive, many people wonder how they actually work.
 
The question of how do touch screens work is not all that easy to answer, since the technology is quite sophisticated. However, in this article we will present some information that should help you to understand the basics.
 
Different Types Of Touch Screen
 
There are many different ways to achieve the same results. Different manufacturers often have their own preferences for which technology to use, especially if they have invested large sums of money into research and development.
 
One sort is called a resistive touch display. These involve having two transparent and conductive layers separated by a gap. When you press the layers together, the device can measure the resistance both vertically and horizontally to figure out the location of your finger. Another kind uses ultrasonic waves that your finger interrupts. However, the majority of good touch displays as used in phones and tablets are known as capacitive screens.
 
Capacitive Touch Screens
 
Capacitive screens work through capacitance rather than resistance, but they share many similarities besides that. Your finger creates a capacitance on the surface of the device which can be measured from all four corners. By comparing these four values, the location is discerned. Different types of capacitive screens work better for different situations. Some are more robust and thus ideal for point-of-sale applications, while others are more responsive and therefore better for use in personal devices like phones and tablets. However, the screen does little by itself. The software plays a far more important part.
 
Software Advances
 
A touch screen is an input device, essentially no different to a mouse or a keyboard. Just as neither of those devices will work without suitable software, the touch screen’s data must be interpreted in order to be of any use. More accurate mutual-capacitance touch screens have now been combined with sophisticated software so that multiple touch points can be interpreted simultaneously. This allows complex multi-touch gestures to be used. It is vital that each touch point can be interpreted precisely, or else the signal may become too confusing for the software to understand.
 
Summary
 
The essential purpose of a touch display is to provide a transparent layer that sits on top of a screen and records the position of a controlling finger. The position is typically determined by measuring an electrical signal on the X and Y axes. This data is then interpreted by the software to perform a useful task. There are many different ways of accomplishing this, but capacitive screens are common in modern personal devices. High-tech touch displays can even measure multiple inputs simultaneously and facilitate complex gestures and commands that in turn enable elaborate functions to be performed with ease.

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