Dr. Samuel C. Hurst invented touch screen monitors in 1971 and since then they have become increasingly popular, particularly in commercial computing such as ATMs and ticket machines and also in mobile phone and PDA technologies.
Touch screen monitors combine both an input and output device, minimizing the need for separate peripherals like keyboard, mouse and monitor. Instead a user merely has to touch the monitor with either a finger or sometimes a stylus at manipulate the graphical user interface.
Touch screen monitors use one of a number of technological systems to recognize a person's touch the most common being resistive, capacitive, infrared and acoustic wave.
Resistive touch screens are the most versatile, they consist of a normal glass plate that is covered with both a conductive and a resistive metallic layers. The two layers are spaced apart and an electrical current runs through them while the monitor is running. When a user touches the screen, the layers make contact in that exact spot causing interference in the electrical field, the computer then calculates the coordinates.
The only downsides to this system are that the multiple layers restrict about a quarter of the light transmitted by the monitor and they can also be easily scratched which reduces their efficiency.
The capacitive system differs by having a layer that stores an electrical charge placed on the glass panel of the monitor. When someone touches the panel, some of the charge is transferred to the user, so the overall charge on the layer decreases, this can be measured by circuits and calculated by the computer as to where the touch took place. The capacitive system also allows a lot more light to be transmitted from the monitor than the resistive system.
Capacitive touch screens are a lot more durable and resistant to contaminant than the resistive system. They are a more popular for industrial and outdoor applications because of their durability and their imperviousness to moisture, dirt and grease.
Surface acoustic wave technology uses ultrasonic waves that pass over the touch screen panel. When the panel is touched, a portion of the wave is absorbed, like the current in a capacitive system and this can be measured identifying the location of the touch.
Surface wave panels can be easily damaged and contaminants on the surface will hinder its functionality but it offers higher clarity and optical accuracy than the other systems.
Infrared touch screens employ two different methods. One measures warmth of a person's touch to the surface layer. This method requires warm hands and users cannot wear gloves or use a stylus. Another method is to use a light beam near the surface of the screen the infrared is used to measure when that light beam is broken by touching the monitor. IR touch screens are the most durable but can be slow to respond.
Other systems include strain gauge, where the screen is spring mounted on the four corners and the movement is measured when the screen is touched. This technology is heavily durable and resistant to vandalism.
Richard N Williams is a technical author and a specialist in the industrial computer industry helping to develop industrial computer enclosures and protection for all environments. Please visit us for more information about industrial touch screen monitors or other industrial monitors