supporting Sequence of Events

Publication 1732E-UM002A-EN-P - March 2010
Module Overview 9
High Performance Sequence of Events Applications in the Logix
Architecture
Sequence of Events (SOE) applications span a wide range of industry
applications. Typically any event that needs to be compared against a second
event can be classified as SOE.
• Used on discrete machines to identify failure points
• Used in Power Substations or power plants to indicate first fault
conditions
• Used in SCADA applications to indicate pump failures or other discrete
events
• Used in motion control applications to increase control coordination.
• Used in high speed applications
• Used in Global Position Registration
In today's environment, specifications for SOE applications typically require
1 ms or better resolution on time stamps. There are two types of SOE
applications.
First Fault
First Fault measures the time between events with no correlation to events
outside of that system.
Real Time
Real Time captures the time of an event occurrence as it relates to some
master clock. Typically this is a GPS, NTP server or some other very accurate
clock source. This method allows distributed systems to capture events and
build a history of these events. These events are almost always digital, however
some are analog for which lower performance requirements can be configured.
First Fault Detection
An example of first fault detection would be intermittent failure from a sensor
on a safety system faults a machine and halts production cascading a flood of
other interrelated machine faults. Traditional fault detection or alarms may not
appear in the correct timed order of actual failure making root cause of the
down time difficult or impossible.
Time Stamped I/O
High precision time stamps on I/O allows very accurate first fault detection
making it easy to identify the initial fault that caused machine down time.