This article describes the types of touch screen technologies which are available.
Most common touchscreens are based on a sheet of glass covering the display where various technologies are applied to the glass to arrive at the ability to select items on a display for further action. There are of course different attributes to the different technologies used for each of the touchscreen types. The common types of touchscreen technology are:- 4-wire resistive, 5-wire resistive, capacitive, pen touch capacitive, Surface wave acoustic, near field imaging and Infra Red. Taking each one in turn their method of functioning and attributes are below:
4-Wire Resistive Touchscreens
4-Wire Resistive touch technology consists of a glass or acrylic panel that is coated with electrically conductive and resistive layers. The thin layers are separated by invisible separator dots. When operating, an electrical current moves through the screen. When pressure is applied to the screen as in a touch the layers are pressed together, causing the resistance to change and therefore a change in the electrical current. This then registers as a touch and gives its location. 4-Wire Resistive type touch screens are generally the least costly but are generally less precise than other types. This type of touchscreen is generally used in more consumer type products where the performance is less demanding.
5-wire Resistive Touchscreens
5-Wire Resistive touch technology is constructed in a similar way to 4-wire but is more accurate and more durable. 5-Wire Resistive type touch screens are generally more durable than the similar 4-Wire Resistive type. This type of screen is generally found in demanding point-of-sale systems, restaurant systems, industrial controls, and other workplace applications.
Surface Capacitive Touchscreens
Surface Capacitive touch screens are made where the base glass is coated with a capacitive (charge storing) material on its surface. Circuits located at corners of the screen measure the capacitance of a person touching the screen. As a result of the overall capacitance of these circuits changing when the screen is touched the oscillation frequency of the circuits change and can then determine the X and Y coordinates of the touch event. Capacitive type touch screens are very durable, and have a high clarity. They are used in a wide range of applications, from restaurant and POS use to industrial controls and information kiosks. Their advantages are: image clarity, not affected by dirt, grease and moisture, only works by be touched by a human finger and high touch resolution.
Projected Capacitance Touchscreens
Projected Capacitance touchscreens operate on a slightly different basis where two sets of conductive layers are etched on the glass screen such that a series of capacitors are produced. A human finger as it touches or gets near these capacitors change their capacitance thereby creating a touch event with X and Y coordinates. The fact that the screen capacitors change capacitance with a finger near the screen means that the screen can be placed behind and armoured glass and still work as a touchscreen – hence the name Projected Capacitance Touch. This type of screen is inherently more accurate as well as being the main type used for vandal proof systems.
Infra Red Touchscreens
Infra Red touchscreens are not so common and use an array of IR light emitting diodes on two adjacent bezel edges of a display with photo sensors on the opposite sides of the display to analyse the system and determine a touch event. The LED and photosensor pairs create a grid of light beams across the display. An object (such as a finger or pen) that touches the screen interrupts the light beams, causing a measured decrease in light at the corresponding photosensors. The measured photosensor outputs can be used to locate a touch-point coordinate.
Widespread adoption of infrared touchscreens has been hampered by two factors: the relatively high cost of the technology compared to competing touch technologies and the issue of performance in bright ambient light. However, one feature of infrared touch remains desirable and represents attributes of the ideal touchscreen which is to eliminate the glass or plastic overlay that most other touch technologies require in front of the display. In many cases, this overlay is coated with an electrically conducting transparent material which reduces the optical quality of the display.
The above systems form the bulk of the touch screen technologies in use at the present time and are generally widely available. The various technologies have different attributes and are used in different applications. Some much more costly than others but are needed in certain environments. Nearly all are easy to incorporate into systems and set up after manufacture. At Kiosks4business most of the requirements we see are for 5-wireresistive and projected capacitance type screens.
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