Different Types of Touchscreen Technologies : SAW Explained

Posted on February 13, 2018 by Christian McFarquhar

All touchscreens are not the same.

They achieve the same thing; you place your finger or stylus on the screen and your finger or stylus acts like a cursor or mouse pointer, but there are several different types and they achieve this by using different builds and technologies. There are also pros / cons – advantages and disadvantages to each type.

The four most widely used touchscreen technologies are:

Capacitive Touchscreens
SAW (surface acoustic wave)
Resistive
Infrared

SAW touchscreens are most widely used in public settings. They can be used with fingers, gloves and any other item as big as a normal finger. (a narrow object such as a stylus cannot be used as this can move between the gaps in the acoustic waves) They are often used for cash machines, point of sale terminals and for shops and supermarkets etc.

Saw which stands for Surface Acoustic Wave uses two layers of sound waves that cover the surface of the top glass layer. One layer runs left to right and the other top to bottom. The sound wave is so high pitched that it cannot be heard. I have tried to research if any animal can hear them – but have been unable to find any research on this. When any item: is placed on the surface of the screen the sound waves are broken and a processor converts this into the appropriate co-ordinates.

This is a very simplified explanation of how SAW touchscreens work but hopefully explains the basic principle.

Pros / Advantages of SAW Touchscreens and why you may choose one

Image Clarity is Perfect
They are very sensitive and can be touched lightly
Long Touch Life. The sound waves are unaffected by repeated use.
Can be used with gloves

Cons / Disadvantages of SAW Touchscreens and why you not may choose one

Cannot be used with narrow or thin objects (even fingernails)
Dust and water droplets can interrupt the sound waves and give false readings.

NB: There are a few different touchscreen technologies that utilise sound waves. SAW is by far and away the most popular. But some screens do utilise others. APR is Acoustic Pulse Recognition, DST is Dispersal Signal Touch and BWT is Bending Wave Touch. Largely the principle of using sound waves is the same. But the sound waves may be projected or recognised using different technological devices.

To read more on other types of touchscreens use the links below:
SAW Touchscreens Explained

Capacitive Touchscreens Explained

Infra Red Touchscreens Explained

Resistive Touchscreens Explained