Historical Trend Express VI

LabVIEW 2013 Datalogging and Supervisory Control Module Help

Edition Date: June 2013

Part Number: 371618J-01

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Owning Palette: DSC Module VIs and Functions

Requires: DSC Module

Reads historical data from the Citadel database and displays the data on an XY graph. You must wire a VI Server reference of this XY graph to the Trend Reference input to use this Express VI. You must place the Historical Trend Express VI inside a While Loop.

Dialog Box Options
Block Diagram Inputs
Block Diagram Outputs

Dialog Box Options

Database URLContains the source Citadel database.
BrowseDisplays the Browse Citadel dialog box from which you can select an existing Citadel database on the network.
Select Historical Data TracesDisplays a tree from which you can select one or more existing historical data traces in the Citadel database you specified in Database URL.
AddAdds the selected item(s) from Select Historical Data Traces to Added Historical Data Traces.
RemoveRemoves the selected item(s) from the Added Historical Data Traces list.
Added Historical Data TracesLists the historical data traces to display on the XY graph.
Enable updatesEnables or disables the data updating. By default, this checkbox contains a checkmark, which means the XY graph updates the data every n seconds automatically.
Time between updatesSpecifies the time, in seconds, that this Express VI waits before attempting to read data from the Citadel Database. The default value is 15.
Use 'localhost' in URL?Uses localhost as the computer name in the URL of the shared variable or trace.
Time AxisContains the following options:
  • Absolute—Displays data for the period specified in Start Time and Stop Time.
  • Relative—Displays data for the specified amount of time.
  • Start Time—Specifies the start time of the data to display. This option is available only if you select Absolute.
  • Stop Time—Specifies the end time of the data to display. This option is available only if you select Absolute.
  • Display last—Specifies the amount of time to display data for a historical trend configured for relative time. The format is HH:MM:SS. This option is available only if you select a Time Axis of Relative.

Block Diagram Inputs

Trend ReferenceIs the control reference to the XY graph.
Relative TimeSpecifies the range of data to display, in seconds, since the current time.
Time Between Updates (s)Specifies the refresh interval of the XY graph.
Database URLSpecifies the computer name and the database name where the Citadel database resides. Enter the database URL in the format \\computer\database. For example, if you have a copy of the LabVIEW Datalogging and Supervisory Control (DSC) Module and Citadel service installed on a computer named datalogger and the name of the database on that computer is data, you can access the data on datalogger from another computer by using the path \\datalogger\data. If you provide a database name only, this VI searches for the database on the local computer. If you do not wire database URL, this VI reads data from the database associated with the default DSC Module process.
error in (no error)Describes error conditions that occur before this node runs.
Shared Variable ListLists the shared variables to display on the XY graph. This list corresponds to the Added Historical Data Traces list in the configuration dialog box of this Express VI.
Start TimeSpecifies the start time of the data to display on the XY graph.
Stop TimeSpecifies the stop time of the data to display on the XY graph.

Block Diagram Outputs

error outContains error information. This output provides standard error out functionality.
Historical TracesContains the array of historical data points retrieved from the database. Wire this output to an XY graph.


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