10
10-3
FM 351 Positioning Function Module
EWA 4NEB 720 6001-02
10.2 Selecting an Incremental Encoder
Only incremental encoders with two pulses having zero marks and offset by
90° are supported:
Encoders with symmetrical output signals with 5 V differential interfaces
conforming to RS422
– Cut-off frequency = 500 kHz
– At 5 V supply voltage: max. 32 m line length.
– At 24 V supply voltage: max. 100 m line length.
Encoders with asymmetrical output signals with 24 V level
– Cut-off frequency = 50 kHz: max. 100 m line length.
The following response time applies to incremental encoders:
Response time = Hardware switching time
Note
You can compensate the response time with appropriate parameterization of
the switchover and switch-off differences.
An example of the response time:
Hardware switching time: approx. 150 µs
Response time = 150 µs
Blurring affects the positioning accuracy. With incremental encoders the
blurring is negligible.
We recommend that you use incremental encoders from SIEMENS
(see Appendix B).
Incremental
Encoders
Response Times
Example:
Response Times
Blurring
Manufacturer
Encoders
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