Search your PI Server for event
start/end times defined by PI tag Expressions
ExpressionEvent Quick Search is a stand-alone query tool for "events" in your PI Server that are based on PI
tag Expressions.
Once you define the event, you can search PI for all occurrences of the event
over a user-defined time period.
The
ExpressionEvent Quick Search tool is part of
Exele's PI ProcessTemplates
software, yet is also provided as a
free, stand-alone tool for all PI users.
ProcessTemplates allows operators and engineers to monitor key process
measurements during “events” in an attempt to repeat the profile of these
measurements during the events.
“Events” in ProcessTemplates are periods of time for which monitoring should
occur. Examples include equipment startup and shutdown, production cell operations,
batch
operations (PI UnitBatches, SubBatches), and fixed time-interval events
(every hour, every day).
ProcessTemplates allows users
to define their own process events through a powerful, configurable,
expression-based event engine: ExpressionEvents.
For
the first quarter of the year, find each environmental emission exceedance
(defined by the NOx emissions being over a known limit value) along with the
duration of the exceedance
Show
me start/end time and duration when the temperature exceeded 100 degrees
over the last 3 days
Return
all turbine startup events defined by a value range of the RPM tag
Find
all periods or time when the temperature was greater than 100 degrees and, at the
same time, the pressure was less than 50 psi
Event Expression
The Event Expression is the main expression for the event.
The syntax of this expression can be
A
PI Tag expression using the PI PerformanceEquation (PI-PE) syntax. The
result of the expression should be TRUE when the event should start.
A
fixed time interval using the syntax “Every Nx” where N is a number and
x is time units. Time intervals start at midnight and should result in
an even number of intervals in one day.
Click
the [Tag search] button to perform a PI tag search. The selected tag will be
returned to the expression text box.
Click the (?) for examples of supported expression syntax. Click [Syntax
help...] to view the Performance Equation help file.
Maximum duration
Enter the maximum duration for the event in seconds. When searching for
events, ExpressionEvents may need to find the start or end of the event by
looking beyond the search start/end time by the entered “Maximum duration”
duration.
ExpressionEvent type
The primary event expression (above) defines the start time of the event.
The ExpressionEvent type allows you to define the end of the event.
Event starts when expression turns TRUE and ends when the expression
turns FALSE
The main expression defines when the event is active. The event is
active when the main expression result is TRUE.
Event starts when the expression turns TRUE and ends X seconds later
The main expression defines when the event starts. After the events
starts, it will end X seconds later, regardless of the current result
(TRUE/FALSE) of the main expression after the event starts. You can use
this option for events that start with a trigger pulse or trigger event
and should remain active for a fixed period of time.
Event starts when the expression turns TRUE and ends when the
following expression turns TRUE
The main expression defines when the event starts. After the event
starts, it will end when
The second expression turns TRUE
OR
The main expression turns FALSE then TRUE again
Event start/end time resolution
For PI tag expressions, the expression can be evaluated at
The archive times for the PI tags in the expression (Archived data)
A
specified sample rate (Sampled data)
Most
users can utilize the faster method of expression evaluation at the archive
times of the tags in the expression. This is typically true for integer and
digitals tags, as well as float tags that are changing frequently.
Sampled data example The following example demonstrates a case where you may want to evaluate
the expression at a sample rate instead of archive data times of the tags in
the expression.
Expression: ‘my.tag’ > 100
Archive data for ‘my.tag’, a float tag with point attribute “stepped” =
false
Time
Value
12:00:00
0.0
12:30:00
50.0
01:30:00
150.0
If the
expression is evaluated at the archive times of ‘my.tag’, the event start
time will be 1:30.
Yet, it you look at a trend of this tag, you may see that tag value is 100
at about 1:00 (this is an interpolated value using the archive values before
and after 1:00). Setting the start/end time resolution to sampled, 10 seconds,
will result in a start time within 10 seconds of 1:00.
Search for events Once you have defined the search
criteria, click the [Search] button to search for events over the entered
start and end time. Calculation interval (optional). For long search periods, the tool
may return the error "number of archives exceed limit". If this occurs,
enter a non-zero calculation interval in days. A non-zero calculation
interval will perform the search for each calculation interval within the
entire period, then compile the results for the entire period.
Use the [Export] button to export the events to a file.
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