Siemens SIMATIC FM 351 Manual page 80

Machine Data and Incremental Dimensions
Example of Absolute Encoder Adjustment
In the example, the following is assumed:
Reference point coordinate = –125 mm
Working range of SSW_STRT = – 1000 mm to SSW_END = 1000 mm
Absolute encoder adjustment = 0
Encoder range = 2048 increments with a resolution of 1 mm/pulse
The absolute encoder used cannot be exactly adjusted mechanically and also
does not have the option of setting the encoder value.
Current
2047
Encoders
Desired
1) Correlation between the coordinate system and the encoder values with the set abso-
lute encoder adjustment. The encoder value 0 corresponds to the actual value -125.
2)
Required correlation of the coordinate system with the encoder. At this position the
coordinate should be -125.
Result After Setting the Reference Point
After "set reference point", the relationship is as follows:
The reference point coordinate on the axis (-125) is assigned to the encoder value
(1798) calculated from the absolute encoder adjustment.
8-20
Actual value
–1000
0
–1000
–125 0
1)
Encoder value 0
2)
–125 0 1000
FM 351 Positioning Module
C79000-G7076-C351-02