Tags - Siemens SIMATIC S7-1500 Function Manual

Basics
3.12 Actual values
Absolute actual value with the setting absolute (measuring range > traversing range)
The axis position results directly from the actual encoder value. The traversing range must
be within an encoder measuring range. This means that the zero point of the encoder must
not be located in the traversing range.
When the controller is switched on, the axis position is determined from the absolute
encoder value.
Absolute actual value with the setting absolute (measuring range < traversing range)
The encoder supplies an absolute value within its measuring range. The controller includes
the traversed measuring ranges and thus determines the correct axis position beyond the
measuring range.
When the controller is switched off, the traversed measuring ranges are saved in the
retentive memory area of the controller.
At the next power-on, the stored overflows are taken into account in the calculation of the
actual position value.
NOTICE
Movements of the axis while the controller is switched off can skew the actual value
If the axis or the encoder is moved by more than half of the encoder measuring range while
the controller is switched off, then the actual value in the controller is no longer in accord
with the mechanical axis position.
3.12.4

Tags

The tags named in the Homing (Page 58) section are relevant for adapting actual values.
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S7-1500 Motion Control V13 Update 3
Function Manual, 07/2014, A5E03879256-AC