Rockwell Automation 1771-QDC, D17716.5.85(Passport) MNL. PLASTIC MOLDING MODULE - Manual (Page 48)

Configure the QDC Module's I/O
Chapter 3
3-17
Configure a Digital Filter for the Position Input from the Ram (Screw)
You may enable an optional digital filter on position inputs to reduce
electrical noise from a potentiometer-type position sensor or picked up by
your input circuits.
To determine if you need a digital filter, move the ram (screw) very slowly.
With your programming terminal, look for erratic position numbers
reported for ram (screw) position by examining SYS25 (N40:177).
Configure the QDC Module for a Digital Input Filter as Follows:
To determine the time constant (0 - 00.10 sec), start with a small value
such as 00.01 and enter it into MCC16 (N40:12). A value of zero disables
the filter.
ATTENTION: Increasing the value of the time constant
decreases the QDC module’s capability to respond quickly to
travel limits and/or to accurately locate programmed positions.
We recommend that you keep the time constant under 00.10.
For example, with a ram (screw) linear velocity of 10”/sec, a 00.01 time
constant allows 0.10” of travel before the QDC module can react to a
travel limit.
Important: If you have a noisy potentiometer-type position sensor and
digital filtering slows the QDC module’s response time too much, consider
replacing the sensor with a non-contact linear-displacement type.
Download time constants to the QDC module using the procedures
presented earlier in this chapter.