The function and accuracy of encoders from HEIDENHAIN are determined essentially by the measuring standard and scanning principle used.
In the incremental measuring method the position information is obtained by counting the individual increments (measuring steps) from some point of origin. Since an absolute reference is necessary in order to determine the positions, a reference-mark signal is output as well. As a general rule, encoders that operate with the incremental measuring method output incremental signals. Some incremental encoders with integrated interface electronics also have a counting function: Once the reference mark is traversed, an absolute position value is formed and output via a serial interface.
With the absolute measuring method the absolute position information is gained directly from the graduation of the measuring standard. The position value is available from the encoder immediately upon switch-on and can be called at any time by the subsequent electronics. Encoders that operate with the absolute measuring method output position values. Some interfaces provide incremental signals as well.
Absolute encoders do not require a reference run, which is advantageous particularly in concatenated manufacturing systems, transfer lines, or machines with numerous axes. Also, they are more resistant to EMC interferences.