Absolute Encoder Adjustment - Siemens SIMATIC FM 351 Manual

8.6

Absolute Encoder Adjustment

Definition
With absolute encoder adjustment and the reference point coordinate, there is a
defined correlation between the range of values of the encoder and the coordinate
system of the axis.
Finding the Correct Absolute Encoder Adjustment
After the initial parameter assignment, further steps are necessary to establish the
correct relationship between the encoder and the coordinate system. The
procedure is illustrated using the parameter assignment dialogs.
1. Move the axis to a defined, reproducible point to which a unique coordinate is
assigned.
This could be, for example,the "end software limit switch".
2. Call the "set reference point" job with the coordinate of the point defined in 1.
The FM 351 now calculates the correct absolute encoder adjustment for the
reference point coordinate in the machine data. This value is displayed in the
dialogs of the encoders and in the service dialog of the configuration software.
3. Save the parameter settings with the menu command File > Save.
4. Close the parameter dialogs with File > Exit.
5. Save the data in HW Config with Station > Save and Compile.
6. Download the data in HW Config to the CPU.
Note
You make this adjustment once during installation and startup. The FM 351 is
synchronized following parameter assignment during startup as soon as a
complete, error-free frame is received from the encoder following startup.
Data in the Parameter DB
Address Name
44.0 REFPT
48.0 ENC_ADJ
FM 351 Positioning Module
C79000-G7076-C351-02
Data Initial Value
Type
DINT L#0
DINT L#0
Machine Data and Incremental Dimensions
Description
Reference point coordinate
Range:
–1 000 000 000 m to 1 000 000 000 m at
a resolution of 1 m/pulse
–100 000 000 m to 100 000 000 m
at a resolution of < 1 m/pulse
Absolute encoder adjustment:
25
Range: 0 to (2 –1)
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