Rockwell Automation 1756-IH16ISOE ControlLogix Sequence of Events Module - Manual (Page 60)

Publication 1756-UM528A-EN-P - April 2004
5-8 Using the Sequence of Events Module Features
Chatter Detection
To detect a faulty input device wired to the Sequence of Events
module, the module can use Chatter Detection to detect a
chattering signal from a device connected to one of its inputs (e.g.,
rapid transitions from a failed contact) and ignore the data. If not
accounted for, chatter can cause the module to timestamp invalid
input transitions. Typically, chattering signals cause inputs to
transition falsely many times in a relatively short period of time.
To configure Chatter Detection for an input, you must define an
acceptable number of input transitions within a specific
time period.
• If the number of input transitions meets the number specified in
the configured time period, the module considers the point in
chatter, the input device defective and ignores the last transition
(i.e., clears any timestamp data for the transition from its buffer)
and all subsequent transitions while still chattering.
• If the number of events in the specific time is less than your
defined number, the input will not go into chatter and
timestamps are produced for all transitions.
• If an input is chattering, the corresponding fault bit for that
input is set.
• Once a point is in chatter, all transitions on that input are
ignored until the point is no longer chattering; an input is no
longer chattering if the configured chatter time elapses and no
new transitions occur on the input.