Point of sale

I often get requests for touch screens and touch applications and wonder if the client is well enough informed on the various technologies for correct and flawless implementation and integration suitable to their expectations on performance. Most users don't know that SAW, IR and Accutouch are currently the major technologies available for them to choose from each with their own benefits and drawbacks and each intended for different applications and environments. Accutouch (which is a 5 wire resistive panel) and SAW (surface acoustic wave) are the ones most commonly fitted in retail and hospitality point of sale devices. Newer point of sale equipment can also be equipped with infra red touch screens.
The working operation of the various touch screens is simple. Accutouch consist of 2 layers of conductive transparent material insulated with grid spacing. This technology is easily identifiable just by looking at the screen one would see grid array of dots both horizontally and vertically and one would also "feel" the touch membrane. This technology is extremely popular in the club and bar environment where users can use anything from finger, pen or card to control their application. Accutouch screens are resistant to liquid spills and I will recommend this type of screen for restaurants where the packing screen is fitted in a kitchen close to the deep fryer or in a bar environment especially where shooters are poured and sticky residue stays on the screen.
For fast food outlets, cooking oil and droplets does not cause de-calibration nor does it result in cursor drift unlike the SAW and IR technologies when used in these environments. One drawback of this technology is that it is prone to scratches, burn marks and the discoloration where users touch constantly on the same place over and over i.e. a login screen where keypad is displayed. When cleaning Accutouch panels use soap and water, stay away from chemicals.
Surface acoustic wave and IR technologies do not have the same problems as Accutouch panels. To understand the problems associated with SAW and IR one would need to understand the working principle behind it. SAW panels has deflector strips along the 4 sides of the panel, with transmit and receiver transducers in the corners.
The deflector strips and transducers are not visible; they are covered by the LCD's front bezel. Similarly the infra red panel consist of a PCB frame populated with a row of infra red transmitters and receivers. Both the Infra Red and SAW panels transmit an invisible grid of acoustic waves or infra red beams. When the panel is touched the X:Y co-ordinates are calculated by the touch controller and a HID or human interface device is emulated. IR technology is easily identifiable by an infra red filter (normally dark red or black) between the glass and LCD bezel. Keep this filter dust and scratch free as it may give rise to sporadic cursor jumps and invalid touch conditions. Infra red technologies are normally water proof and sealed making them popular in environments where liquid spills occur. SAW or intelli-panels are normally fitted with a dust strip inside the front bezel.
These strips provide the small space required for the bezel not to press directly on the reflector strips (causing invalid touch conditions) and also stops dust from entering the system. It is extremely common for these dust strips to accumulate dirt and grime giving rise to various touch problems and these displays.
If you are experiencing erratic touch problems on your system inspect the areas where the front bezel meets the glass, nine out of ten times you will find your problem. Sometimes one can remove the buildup with alcohol and lint free cloth, if that does not work you would need to remove the front bezel and the panel to clean the transducers and reflectors. Remember these technologies do not work with foreign matter on the glass panel. Touch problems can be avoided by simply keeping the panel clean. It is recommended to use SAW technology in cleaner environments.
Written by: Melt Brink
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