Siemens SIMATIC ET 200S Operating Instructions Manual page 109

Pulse and Direction
The level at direction input B is used as the direction setting.
An unwired input corresponds to the "Up" count direction if you have selected
"Pulse/direction" for the "Signal evaluation" parameter.
Figure 2-45
Rotary Encoder
The 1Count24V can count the edges of the signals. Normally, only the edge at A is
evaluated (single evaluation). To obtain a higher resolution, when assigning parameters
("Signal Evaluation" parameter), you can select whether the signals are to be subjected to
single, double, or quadruple evaluation.
Multiple evaluation is only possible with asymmetric incremental encoders with A and B
signals that are 90 degrees out of phase.
Single Evaluation
Single evaluation means that only one edge of A is evaluated; up count pulses are recorded
at a positive edge at A and low level at B, and down count pulses are recorded at a negative
edge at A and low level at B.
The diagram below illustrates the single evaluation of the signals.
Figure 2-46
Technological Functions
Operating Instructions, 06/2010, A5E00124867-07
Signals of a 24-V Pulse Generator with Direction Indicator
Single Evaluation
2.10 Evaluation of count and direction signal
1Count24V
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