Touch screens are by far the best way to operate a Point of Sale system, and have been for a long time.
Touching a point on the screen with your finger emulates clicking with a mouse. This makes operation much faster than trying to use a mouse and keyboard and much simpler.
The main problem with touch screens in the past has been the cost. While there have been some cheaper ones available, they tended to wear out quickly and many cheap ones in heavy use would lose sensitivity to parts of the screen in as little as 6 months with heavy supermarket usage.
However there have always been 2 premium manufacturers of touch screen which would last up to 1000 times more touches than the cheap alternatives. Those manufacturers have been ELO and Microtouch (owned by 3M). For a long time, we advised customers to only buy ELO or Microtouch touch screens. Unfortunately those quality touch screens were significantly more expensive than the low quality alternatives.
Now however, with more and more devices using touch screens, the price is falling dramatically. And more manufacturers have entered the market. In some cases you can buy complete "all in one" computers for around the same cost as a premium touch monitor.
How they work
Touch screens have a touch panel placed on top of the display monitor. Almost all
touch panels are post fitted to the monitor after manufacture. The monitor
case is opened, and the touch panel placed directly on top of the display and then closed
so that it looks as if it had been manufactured that way.
The touch panel detects the coordinates where it has been touched, and the controller sends that information back to the driver which translates the position touched to the position on screen .
Important!
You need to know which company manufactures the touch panel and controller. The brand name
shown in the monitor is not the manufacturer of the touch panel and touch controller.
The sales rep trying to sell you the touch screen may not know, but it should be
shown in the specification. If you can't find out which company makes the touch
panel and touch controller, then it is probably because it is a cheap low quality
touch panel.
Resistive Touch Panels When you put pressure on a resistive touch panel, it lowers the electronic resistance at the point and that is what is used to detect the position touched.
There are "4 wire" resistive touch screens and "5 wire" resistive touch screens. If a 4 wire resitive touch screen is scratched, it will stop working. 5 wire resistive touch panels will continue to work even thought they have been scratched. always choose 5 wire resistive over 4 wire.
Resistive touch screens feel positive to use. You can tap them with a finger nail, and they are fast to respond. They can provide good accuracy when touched at a small point with a stylus or finger nail.
Capacitive Touch Panels Capacitive touch panels detect a variance in capacitance where touched by your finger. They need to be touched with the ball of the finger, not the finger nail or stylus.
Because the surface area on the ball of your finger is larger than a small part of a finger nail, the position detected is less precise than with a resistive touch screen. They are also a little slower to operate since you are pressing the ball of your finger instead of tapping your finger nail.
Capacitive touch screens do not wear like resistive touch screens. They used to be more expensive than resistive touch screens, but now they are fairly similar in price.
Surface Acoustic Wave Surface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touch panel. When the panel is touch, a portion of the sound is absorbed and this is detrected by the touch sensor and controller.
We have never used SAW touch screens and see no particular benefit for POS applications, however good SAW touch screens will work effectively for POS systems.
Monitor Case/Stand When choosing a touch monitor, it is very important to look at the monitor stand and the way it is mounted. Most display monitors are not designed to be touched, they just need to stay in one position.
But touch monitors are used by pushing them with a finger, and if they move about or flop around it makes them difficult to use, and can cause the mounting to break.
VESA monitor mounts are a very good idea for touch screens.
Monitor Size You don't need a large touch monitor for point of sale. Very large screens might look good on a desk, but at the point of sale, they just get in the way and use counter space.
Touch screens provide input to the computer by either a Serial RS-232 connection, or a USB connection.
Serial cables normally come with the touch screen, so you rarely have problems making up a cable. Serial interfaces however are no longer supplied standard with many computers, so in general USB is a better choice.
Touch Screen Drivers Touch screen controllers all work differently, and you will need drivers supplied by the manufacturer. The quality of these drivers vary widely. Drivers from Microtouch and ELO are excellent and support both Windows and Linux. If you are buying from another touch panel manufaturer, you need to test the drivers, and how the screen is calibrated.
Make sure the drivers are also available for Linux, even if you plan to run Windows, just to keep your options open later.