Siemens SIMATIC S7-300 FM 350-1, Руководство пользователя

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Encoder signals and their evaluation
8.2 5-V differential signals
FM 350-1 Counter module
Manual, 05/2011, A5E03648639-01
161
8.2 5-V differential signals
Count signals of 5-V incremental encoders
RS422 signals returned by the 5-V incremental encoder to the module:
●
A and /A
● B and /B
● N and /N
The signals /A, /B and /N are the inverted signals of A, B and N. Signals A and B are phase-
shifted by 90°.
The tracks A and B of 5-V incremental encoders are used for counting. Track N is used to
initialize the counter with the load value, if programmed accordingly.
Encoders featuring these six signals are symmetrical encoders.
The diagram shows the time profile of the encoder signals:
6LJQDO$
6LJQDO$
6LJQDO%
6LJQDO%
6LJQDO1
6LJQDO1
'LUHFWLRQRIFRXQW
8S
'RZQ
Figure 8-1 Signals of the 5-V incremental encoder
The module detects the count direction by evaluating the ratio of signals A and B. The
diagrams in the chapter "Signal evaluation (Page 166)" show which edges of signals A and B
are counted in down or up direction.
Changing the count direction
You can change the count direction using the "Count direction normal" and "Count direction
inverted" parameters without having to modify the wiring.