Have you ever wondered how exactly touchscreen devices are able to pinpoint the exact location of your touch commands? Whether it’s a smartphone, tablet, human machine interface (HMI) or retail point-of-sale (POS) system, touchscreens today offer an exceptional level of precision. When you touch or tap an area of the display, the device will register your command in that precise area. In this post, we’re going to explain how touchscreens are able to identify the location of touch commands.
The way in which a touchscreen identifies the location of touch commands varies depending on the specific type of touchscreen. Capacitive touchscreens, which are the most common type, rely on capacitance to identify the location of touch commands. When turned on, they emit a uniform electrostatic field across the surface of the display interface. Upon touching the interface with a bare finger or conductive stylus, the device’s capacitance changes. As a result, capacitive touchscreens are able to pinpoint exactly where the touch command was performed. If the capacitance drops in a specific area, the device will register that area as being touched or tapped.
Not all touchscreens rely on capacitance to identify the location of touch commands. Some rely on pressure, such as resistive touchscreens. Resistive touchscreens are designed with a top layer and a bottom layer, which are separated by an inert spacer layer. When you touch or tap the display interface, the top layer will press down onto the bottom layer. And because each of these layers have a conductive coating, it creates a closed circuit, thus allowing the device to determine where you touched.
Resistive touchscreens aren’t as precise in detecting touch commands as capacitive touchscreens. However, they offer the benefit of supporting any object, regardless of whether it’s conductive.
While not as common as capacitive or resistive, a third type of touchscreen technology is surface acoustic wave (SAW). Also known as acoustic pulse recognition, it uses ultrasonic sound waves to detect the location of touch commands. SAW touchscreens project ultrasonic sound waves across the display interface. When you touch or tap the display interface, you’ll disturb the sound waves in that specific area.
As you can see, touchscreens identify the location of touch commands using one of several techniques. Capacitive touchscreens work by measuring capacitance; resistive touchscreens work by sensing pressure; and SAW touchscreens work by sensing disturbances in ultrasonic sound waves.