Save operation using two hands via multitouch. Photo: tci GmbH
Not even ten years ago it was just normal to react slightly upset: colleagues who have left several fingerprints on the screen (no touch screen at that time) when explaining the structure of their new excel table. When releasing LCDs it has even been discussed if touching the display could be harmful – as you can see in an article of 2009.
Touch as a Part of Every-Day Life
Due to the increasing number of smartphones, operating via touch became part of our every-day life. Particularly in the private sector we take it for granted to operate directly on the display. This has two key benefits, no matter if we look at the usage in a car, in a smart home or on a production system:
- The user doesn’t need to switch focus between input device and display, there is just one single device.
- There are no mechanical buttons that need space in the housing and can fail because of dirt or abrasion.
However, I don’t want to conceal a disadvantage: to find out if the operation procedure has been successful, in many cases the user has to take a look at the display. An acoustical or vibrational response isn’t always possible.
In the following you’ll find a brief overview and a comparison of the most common touch technologies.
Capacitive Glass Touch
The glass surface is coated with a transparent metal oxide. An alternating voltage at the ends of the coating generates a uniform electrical field. The touch of a finger creates a minimal current flow which is measured on the corners of the touch screen. On this basis the touch controller determines the exact position of the finger. Disadvantage: it doesn’t work with gloves.
Resistive Touch Screens
Resistive touch sensors consist of two conductive coatings – one of them is flexible and the other one is solid – which keep distance to each other and create a voltage divider. When operating the flexible coating is pushed against the solid one. The controller measures the electrical resistance and is able to calculate the position of the pressure point exactly.
Compared to capacitive touch, which just needs to be touched softly, the resistive version requires a certain pressure. The operation can also be carried out with a glove or pen. Disadvantage: The flexible coating gets worn out. Using the new gfg technology (glass-foil-glass), the flexible coating is protected through a thin scratch-resistant glass coating, which ensures the advantages of a glass surface.
For example tci’s Industrial Computers H16ST and H19ST are available with resistive glass touch (gfg). Industrial Computers are often equipped with resistive touch screens. This has proven over the years and is more cost-effective than the capacitive ones. Those are utilized in areas, where it is important to operate with several fingers (multitouch) – resistive technologies only identify one pressure point.
There are some other touch technologies which are used in special applications, so I refer to Wikipedia. What is your experience regarding touch screens? Share your opinion as a comment on our blog or write an e-mail directly to the author.