A distinction is made between incremental and absolute measuring procedures:

• In the case of incremental encoders, the machine must travel to a reference point after each power?off state, as the position is not usually stored in the controller, and movements of the machine while the power is off are not recorded.
• Absolute encoders, on the other hand, also record these movements while the power is off and return the actual position with power On. Travel to a reference point is not necessary.