Incremental Encoders

These encoders deliver a defined number of electrical pulses for each rotation, which represent the measurement of the distance or angle moved. Incremental encoders operate on the principle of optoelectronic scanning of index disks operating on the transmitted light principle. The light source is a light emitting diode (LED). The light-dark modulation generated as the encoder shaft rotates is picked up by optoelectronic elements. With an appropriate arrangement of the line pattern on the index disks connected to the shaft and the fixed aperture, the photoelectronic elements provide two trace signals A and B at 90° to one another, as well as a reference signal. The encoder electronics amplify these signals and convert them into different output levels.

The following output levels are available:

In the case of RS 422 encoders (TTL) the resolution can be improved by a factor of four by means of edge evaluation. In order to obtain an even finer resolution, in the case of encoders with sinusoidal signals, these signals are interpolated in the higher-level controller. Encoders with HTL interfaces (High Voltage Transistor Logic) are well suited for applications with counter modules.