Touch Sensor

Resistive single-touch screens have been then workhorse of the touch screen market for 20 years. Until now, multi-touch capabilities were reserved for non-resistive touch technologies such as surface or projective capacitive and surface acoustic wave, etc. Resistive touch sensor responds to pressure on its surface.
There are 2 common type of touch sensor that is Resistive type and Capacitive type. in resistive type there are 2 configuration:
1. 4-wire type
2. 5-wire type
3. 8-wire type
here i explain a little bit about basic operation of 4-wire type.
A 4-wire resistive consists of 2-sheets of clear material with a transparent linearly resistive coating applied to one side of each. The two sheets are brought close to one-another with the coated sides facing one-another. Small spacer dots arranged in a grid pattern hold the two sheets apart when the sensor is at rest. A uniform, unidirectional voltage gradient is applied to the first sheet. When contact is made to the surface of the touchscreen, 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 uniform voltage gradient is applied to the second sheet to ascertain the Y coordinate. The controller alternately drives the X and Y axes on the glass layer with a +5V current and reads the resulting voltage from the cover sheet. This operation occurs instantaneously, registering the exact touch location as contact is made.