Three popular types of digitizer technologies are in use today: resistive, electrostatic, and electromagnetic. The following sections describe these different technologies.
The least expensive type of digitizer is resistive. Resistive digitizers can have one or two layers. A single-layer resistive digitizer is made with a transparent film of known, predictable resistance (hence the name). Voltages can be applied at the four corners of the film. Because the film introduces even resistance across its surface, applying a voltage on one edge of the film creates a gradient of voltage across the entire film. Figure 2-3 shows how applying voltage at the corners can introduce such a gradient. When a single-layer ...