The distance to be measured is divided into equal elements (increments), which are then counted. The distance covered is obtained from the total for the increments from a single point of reference.
The increments are applied as a bar pattern on a linear scale (graduated glass scale) or a disc (incremental position encoder) and optically scanned (Figure I 9). For absolute measurements, a zero mark can be added to the scale, with the counter returning to this each time.
Figure I 9: Incremental position measurement