Festo CECX-X-C1 Series, Manual

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System manual CECX / Incremental encoder interface module CECX-C-2G2
CECX-II 27-16
27.6.4 Speed measurement
The velocity measurement function can be used to obtain a good accuracy
of the evaluation when using a rotary encoder with a low resolution.
This is done by measuring the period duration between two incremental
encoder pulses by means of an internal time basis.
The velocity measurement can be made in either direction.
The velocity value is measured four times for each period duration.
If the direction is changed during an ongoing measurement, the measure-
ment is started anew.
Once the measurement is completed the value is marked as new.
The input pulses are scanned with an internal tact of 50 MHz. At a maxi-
mum input frequency of 250 kHz this will result in a resolution of at least 8
Bit.
Frequencies that are smaller than 3 pulses per second are evaluated as ze-
ro velocity.
27.6.5 Pulse counter without direction evaluation
This function provides a pulse counter at track A (edgeCount=4). Direction
information will not be taken into consideration. Track B and Zero are not
evaluated.
27.6.6 Pulse counter with direction evaluation
This function provides a pulse counter at track A. The status of track B de-
cides on the direction of counting.
Track B = 0 -> forward
Track B = 1 -> backward
Track Zero is not evaluated.