Most low cost touch screen applications use a 4-wire resistive touch screen. 4 wire resistive touch is typically glass bottom and film top, but they can be film + Film. It consists of a conductive bottom layer of either glass or film and a conductive top film layer, separated by extremely small, transparent spacer dots. A voltage is applied across the conductive surface. When pressure from a touch is applied to the top layer, it is compressed and makes contact with the bottom layer resulting in a voltage drop. This change is detected by the controller. By alternating the voltage signal between the top layer and the bottom layer, the X and Y coordinates of the user’s touch are computed. Each layer serves as one of the axes. No ITO patterning is required so costs remain lower.
Position detection on analog type resistive touch panel is made by measuring the voltage appeared on the resistive films where panel surface is pressed. When two points or more are pressed under conventional method, detection circuit picks up the mean value between those points as the point where panel is pressed. It was impossible to detect two points or more separately by conventional method.