Rockwell-automation 1769-HSC Compact High Speed Counter Module Manual de usuario descargar pdf (Pagina 33)

Rockwell Automation Publication 1769-UM006E-EN-P - July 2013 33

Module Operation Chapter 2

The generalized rate calculation is Rate =  count/  time.

The cyclic method is better suited to high pulse rates.

Hysteresis Detection and Configuration

Because physical vibration can cause an encoder to generate pulses that you do

not wish to consider as valid motion, a hysteresis value is used to eliminate a

certain number of pulses in either direction as vibration-generated. These pulses

are not used to calculate the Ctr[n].CurrentRate value. You program the

minimum number of counts that are considered to be valid motion, using the

CtrnHysteresis configuration word/menu. If the change in counts over the

update time cycle is equal to or less than the minimum number of programmed

counts, the Ctr[n].CurrentRate is reported as zero.

This concept is not used to alter actual count values.

IMPORTANT

The rate calculation is based on net counts. If a counter goes up 500

counts and down 300 counts, the net count is 200. Therefore, changes in

direction and speed affect the Ctr[n].CurrentRate value.

IMPORTANT

Hysteresis does not depend on the direction of the change in count.

Therefore, creeping, a slow change in count in one direction only, can

also be reported as zero frequency when it falls below the hysteresis

threshold.

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Rockwell-automation 1769-HSC Compact High Speed Counter Module Manual de usuario Pagina 33