Resistive touchscreen

Red Palm Centro smartphone
A Palm Centro, an example of a smartphone with a resistive touchscreen.[1]

In electrical engineering, a resistive touchscreen is a touch-sensitive computer display composed of two flexible sheets coated with a resistive material and separated by an air gap or microdots.[2]

Description and operation

There are two different types of metallic layers. The first type is called matrix, in which striped electrodes on substrates such as glass or plastic face each other. The second type is called analogue which consists of transparent electrodes without any patterning facing each other. As of 2011 analogue offered lowered production costs.[citation needed] When contact is made to the surface of the touchscreen, the two sheets are pressed together. On these two sheets there are horizontal and vertical lines that, when pushed together, register the precise location of the touch. Because the touchscreen senses input from contact with nearly any object (finger, stylus/pen, palm) resistive touchscreens are a type of "passive" technology.

For example, during operation of a four-wire touchscreen, a uniform, unidirectional voltage gradient is applied to the first sheet. When the two sheets are pressed together, the second sheet measures the voltage as distance along the first sheet, providing the X coordinate. When this contact coordinate has been acquired, the voltage gradient is applied to the second sheet to ascertain the Y coordinate. These operations occur within a few milliseconds,[3][4] registering the exact touch location as contact is made, provided the screen has been properly calibrated for variations in resistivity.[5]

Resistive touchscreens typically have high resolution (4096 x 4096 DPI or higher), providing accurate touch control. Because the touchscreen responds to pressure on its surface, contact can be made with a finger or any other pointing device.