Siemens SIMATIC FM 351 - Signal Waveforms from Incremental Encoders; Quadruple Evaluation

10
10-2
FM 351 Positioning Function Module
EWA 4NEB 720 6001-02
10.1 Incremental Encoders
The FM 351 Positioning Function Module supports two types of incremental
encoder:
 Incremental encoders (25 V) with asymmetrical output signals.
 Incremental encoders (5 V) with symmetrical output signals.
The signal waveforms from encoders with asymmetrical and symmetrical
output signals are illustrated in Figure 10-1.
asymmetric
symmetric
A*
B*
N*
A
B
N
A
B
N
Figure 10-1 Signal Waveforms from Incremental Encoders
The FM 351 Positioning Function Module employs quadruple evaluation of
the encoder pulses.
Quadruple evaluation means that both edges of the pulse trains A and B are
evaluated.
A
B
1234
Quadruple evaluationIncrements
Signal period
Figure 10-2 Quadruple Evaluation
Incremental
Encoders
Signal Waveforms
Pulse Evaluation
Encoders