Absolute Encoder Adjustment - Siemens SIMATIC FM 351 Installation Manual

Machine Data and Increments
8.4
Definition
What You Define
Assumption for an
Absolute Encoder
Adjustment
8
8-10

Absolute Encoder Adjustment

The absolute encoder adjustment provides a permanent relationship between
the coordinate system and the encoder.
When you parameterize your FM 351 with the parameterization interface, the
values that you define include the following:
Software Limit Switches Start (SLS) and End (SLE); these are the limits
of the working range.
Reference-point coordinate (REF); this is a value from the working range
of the coordinate system.
Absolute encoder adjustment; this is a value from the value range of the
absolute encoder (0 to total number of steps - 1).
For the example which we want to show in this chapter, the following as-
sumptions apply:
Reference-point coordinate = -125 mm
Working range of SLS = -1000 mm to SLE = 1000 mm
Absolute encoder adjustment = 0
Encoder range = 2048 steps
The absolute encoder used cannot be exactly adjusted mechanically and
also does not have the option of setting the encoder value.
The FM 351 forms pairs of values as shown in the illustration below from the
relationship between the two values for the reference-point coordinate and
the absolute encoder adjustment.
–1000
1
Allocation of the coordinate system to the encoder values with the set encoder
adjustment.
Desired allocation of the coordinate system to the encoder.
2
–1000 –125
2048
2
–125 0
0
1
0
1000
FM 351 Positioning Function Module
EWA 4NEB 720 6001-02