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The trend system described here operates under the TSENTRY real time control system.  It is a data collection system that supports the following functions:

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titleReal-time vs. Historical Trending

The trend system simultaneously supports data collection in two separate modes.  The first mode is real-time trending; in this mode the trend system records the latest trend data into a combination of memory-based and disk-based circular buffers.  As a new point is recorded the oldest point is removed from the circular buffer, so that at any given time only the last n hours, minutes and seconds-worth of data is stored on the system (n is a configurable parameter).

In addition, the trend system can record historical trend data sets and store them as files on disk for later review. The historical trend system is driven by triggers, which are definitions of events and the data that should be recorded when the event is detected.  The historical trend system and triggers are defined in more detail on the Historical Trend Triggers [LINK] section of this manual.

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titleProcesses

The following host processes comprise the Trend System:

  • TrendMgr [LINK] – the trend manager process

  • TrendGsm [LINK] – the data acquisition process acquiring data from global shared memory regions

  • TrendSvr [LINK] – the server process that services client requests for trend data

  • TrendTrig [LINK] – the server process that manages historical trend data acquisition

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titleScreens

The following screens are available as part of the Trend System:

  • TrendX [LINK] – trend display and analysis

  • TriggerMgr [LINK] – trigger configuration and activation

  • TrendFileMgr [LINK] – historical trend file manager

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A historical trend trigger is the definition of an event along with a list of data to be recorded when that event is triggered.  An event is triggered when a set of variables meet some prescribed conditions.  In an aluminum smelting plant, for instance, a trigger could be defined to capture data during an anode effect.  The trigger could watch for when the pot resistance gets too high, and when it does record a set of data including the pot resistance, volts, and line amps.  Once this trigger is configured in the historical trend system, all anode effect events would be captured to individual historical trend files on disk for later review.  

Once a trigger has been activated, the historical trend trigger system monitors each of the trigger conditions and continuously evaluates each of them to determine when they have all been met. During this time the trigger is Waiting for trigger event detection.  If this occurs, and all trigger conditions are met, then data collection begins and the trend system begins to write data to the file.  This will continue until the trigger conditions are no longer all met.  At this point the data file is closed and left on the disk for later review.

Several options are available to enhance data collection:

  • A pre-trigger time period may be configured so that when a trigger event is detected the trend system will actually go backwards in time to retrieve the data leading up to the event and save this in the historical trend file before the data for the event itself.  In many cases this information is crucial for determining the cause of a given event.

  • A post-trigger time period may be configured so that once the trigger conditions are no longer satisfied the trend system will continue to record data for a period of time and append it to the historical trend file after the data for the event itself.  In many cases this information is useful for determining how the control system reacts after a given event.

  • A maximum trend time period may be specified to keep file sizes small and manageable.  This value limits the maximum amount of time of historical data that can be stored in a single file; if the event lasts longer than this amount of time then the data recorded for that event will span multiple files.  This option is useful for continuously recording data (i.e. the event is defined as always triggered) and generating files of finite size.

 

Triggers can be created, modified, activated, and deactivated using the TriggerMgr [LINK] screen.

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titleTrigger File Format

Historical trigger files are stored on the host as ASCII text files.  Following is an example file:

Code Block
[Trigger]
Name=TrackTime
Description=Record the drift constants for the time tracking algorithms.
TagVar=PidCom.rtDrift.filtDrift
PreTriggerTrendTime=30
PostTriggerTrendTime=45
MaxTrendTime=1440
SaveDate=127592326792807993
 
NumTriggerVars=2
TriggerVar0=/TrendGsm/PidCom.rtDrift.bTrack != 0
TriggerVar1=/TrendGsm/PidCom.pcDrift.bTrack != 0
 
NumTrendVars=4
TrendVar0=/TrendGsm/PidCom.rtDrift.filtDrift   PidCom.rtDrift.filtDrift
TrendVar1=/TrendGsm/PidCom.rtDrift.instDrift   PidCom.rtDrift.instDrift
TrendVar2=/TrendGsm/PidCom.pcDrift.filtDrift   PidCom.pcDrift.filtDrift
TrendVar3=/TrendGsm/PidCom.pcDrift.instDrift   PidCom.pcDrift.instDrift

NumScalarVars=2
ScalarVar0=PidCom.rtDrift.filtDrift   PidCom.rtDrift.filtDrift
ScalarVar1=PidCom.rtDrift.instDrift   PidCom.rtDrift.instDrift

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titleO-Buttons and Controls
Menu

In the bottom left of the display is a button labeled Menu.

Clicking this button will navigate back to the most recent menu screen.

TriggerMgr

In the bottom left of the display is a button labeled TriggerMgr.

Clicking this button will display the TriggerMgr screen pre-loaded with a trigger definition created from the current TrendX screen configuration.  That is, all trended variables shown on the TrendX screen will be added in the trigger Trend list.

TrendSet Loader Control

To the right of the TriggerMgr button are a set of buttons used to create, load, save, and delete TrendSets.

A TrendSet is a configuration file stored on the host system that contains all of the configuration parameters for the current trend display.  This allows the user to configure a trend graph, including all of the display variables and axis parameters, and store it on the host for later use. This control panel is described in detail in the TrendSetLoader [LINK] section of this manual.

Trend Playback Controls

To the right of the TrendSet loader control is the TrendPlayback control used to control the playback speed and direction of the trended data.

This control panel is described in detail in the TrendPlayback [LINK] section.

Reset Cursors

To the right of the trend playback controls is a button labeled Reset Cursors.

Clicking this button will move the two data cursors to the far right and far left edges of the current trend view.  This is helpful for regaining access to the cursors while zoomed in to a small section of the trended data.

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