Siemens Sinamics S110 Function Manual page 226

Drive functions
7.3 Function modules
Virtual multiturn encoder (p2721)
The virtual multiturn resolution is used to set the number of resolvable motor rotations for a
rotary absolute encoder with activated position tracking. It can be edited only for rotary axes.
With a rotary absolute encoder (p0404.1 = 1) with activated position tracking (p2720.0 = 1),
p2721 can be used to enter a virtual multiturn resolution.
Note
If the gear factor is not equal to 1, then p2721 always refers to the load side. The virtual
resolution, which is required for the load, is then set here.
For rotary axes, the virtual multiturn resolution (p2721) is preset to the value of the multiturn
resolution of the encoder (p0421) but may be changed.
Example: Singleturn encoder
Parameter p0421 is preset to p0421 = 1. However, parameter p2721 can be altered
subsequently, e.g. the user can program p2721 = 5. As a result, the encoder evaluation
initiates 5 load rotations before the same absolute value is achieved again.
For linear axes, the virtual multiturn resolution (p2721) is preset to the multiturn resolution of
the encoder (p0421) extended by 6 bits (max. overflows 32 positive/negative)
The value for p2721 cannot be edited again afterwards.
Example: Multiturn encoder
For a linear axis, the value for p2721 is set to 262144 for an encoder with p0421 = 4096.
That means, +/- 131072 encoder revolutions or load revolutions can be reproduced in this
way.
If, as a result of extension of the multiturn information, the displayable area of r2723 (32 bits)
is exceeded, the fine resolution (p0419) must be reduced accordingly.
Tolerance window (p2722)
After switching on, the difference between the stored position and the actual position is
ascertained and, depending on the result, the following is triggered:
Difference within the tolerance window → the position is reproduced based on the current
actual encoder value.
Difference outside the tolerance window → an appropriate message (F07449) is output.
The tolerance window is preset to quarter of the encoder range and can be changed.
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
gearbox teeth must be requested from the gearbox manufacturer.
224
CAUTION
Function Manual, 01/2011, 6SL3097-4AB10-0BP3
Function Manual