Siemens SINAMICS S120 Function Manual page 357

Note
The position can only be reproduced if, in the powered-down state, the encoder was moved
through less than half of the range that it can represent. For the standard EQN1325 encoder,
this is 2048 revolutions or half a revolution for singleturn encoders.
Note
The ratio stamped on the gear rating plate is often just a rounded-off value (e.g. 1:7.34). If,
for a rotary axis, it is not permissible to have any long-term drift, then the actual ratio of the
gear teeth must be requested from the gear manufacturer.
Note regarding using synchronous motors with a measuring gear
Field-oriented control of synchronous motors requires a clear reference between the pole
position and encoder position. This reference must also be carefully maintained when using
measuring gears: This is the reason that the ratio between the pole pair number and the
encoder revolutions must be an integer multiple ≥ 1 (e.g. pole pair number 17, measuring
gear 4.25, ratio = 4).
Commissioning
The position tracking of the measuring gear can be activated in the drive wizard (STARTER)
during the configuration of the drive. During the configuration there is an item for encoder
parameterization. In the encoder dialog, click the "Details" button and activate the checkbox
for position tracking in the displayed dialog.
The parameters p0412 (Measuring gear, rotary absolute encoder, revolutions, virtual) and
p0413 (Measuring gear, position tracking tolerance window) can only be set via the expert
list.
Requirement
● Absolute encoder
Drive functions
Function Manual, (FH1), 04/2014, 6SL3097-4AB00-0BP4
Basic functions
7.21 Position tracking
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