Trend worksheet

The Trend folder enables you to configure history groups that store trend curves. You can use the Trend worksheet to declare which tags must have their values stored on disk, and to create history files for trend graphs. The project stores the samples in a binary history file (*.hst), and shows both history and on-line samples in a screen trend graph.

The Trend worksheet is executed by the Background Task module (see Runtime Tasks). It handles the saving of trend data to the history, but it does not display that data to the operator; the Trend Control screen object, available on the Draw tab of the ribbon, must be created and configured in a screen in order to display trend data.

To create a new Trend worksheet, do one of the following:

• On the Insert tab of the ribbon, in the Task Worksheets group, click Trend;

• Right-click the Trends folder in the Project Explorer, and then click Insert on the shortcut menu; or

• Click New on the File menu, click the File tab, and then select Trend Worksheet.

To edit an existing Trend worksheet, double-click it in the Project Explorer.

The Trend worksheet is divided into two areas:

• Header area (top section), which contains information for the entire group

• Body area (bottom section), where you define each project tag in the group. This section contains several columns (only two are shown in the preceding figure).

Header

Configure the following settings in the worksheet header:

Description

Type a description of the worksheet for documentation purposes.

History Format

Click the arrow button to select a trend history format from the list. The available options are:

Proprietary

Save trend history in a proprietary, binary file. The file is saved in your project folder (on the project runtime server) at: […]\<project name>\Hst\GGYYMMDD.hst

• GG = Trend worksheet number

• YY = Last two digits of the year

• MM = Month

• DD = Day

  A new history file is created for each calendar day that the project runs.

  The utility programs HST2TXT.EXE and TXT2HST.EXE are provided in order to convert history files from binary ( *.hst ) to plain text ( *.txt ) and vice versa. For more information, see Converting Trend History Files from Binary to Text and Converting Trend History Files from Text to Binary.

  Database

  Save trend history in an external SQL database of your choice. After you select this format, click Database Configuration to open the Database Configuration dialog box, where you can configure the connection to the database. For more information, see Database Configuration and Database Interface.

  By default, the history is saved in the table TRENDGGG ( GGG = Trend Worksheet Number; for example, TREND001 for the Trend Worksheet 001).

  Historian

  Save trend history to a Historian database. After you select this format, click Historian Configuration to open the Historian dialog box, where you can configure the connection to the database. The trend history for each project tag is saved separately in the Historian database, but you can use Prefix in the database connection settings in order to keep the tags grouped together.

  Note: When the connection to AVEVA Historian is lost, the Gateway stores data in C:\ProgramData\ArchestrA\Historian\StoreForward\<server>\ and forwards it when the connection is restored. String values longer than the Historian limit are shortened and end with (...).

  For more information, see Support for AVEVA Historian.

  The Historian tag name is <Prefix>.<Historian Tag>. If Historian Tag is blank, the project tag name is used. The period between the prefix and the tag name is added automatically. For more information, see Historian tag naming and data mapping.

  Note:

  You can specify String tags in many fields of the Trend worksheet, to change those values during run time, but doing so may affect how those values are saved in the trend history:
  - When the history format is Proprietary, the value of the String tag is converted to a numeric value (if possible) and then saved in the history file. If numeric conversion is not possible, then a value of 0 is saved.
  - When the history format is Database or Historian, the actual value of the String tag is saved in the database.

  Save On Trigger

  Click (enable) and type a tag name to save trend samples when someone changes the specified tag. (Tag change can be an event from the Scheduler.)

  Save On Tag Change

  Click (enable) to always save the trend sample when a value change occurs in any of the tags from that group.

  When the history format is Proprietary or Database, all of the tags in the group are saved after each change. When the history format is Historian, only the tag that changed is saved.

  Advanced

  Click to display the Trend Advanced Settings dialog. For information about completing the fields in this window, see Batch History Configuration.

Body

For each project tag, configure the following settings in the worksheet body:

Tag Name

The name of the project tag for which trend history will be saved.

Dead Band

Type a value to filter acceptable changes when Save on Tag Change is used. For example, Dead Band has value = 5. If the tag value is 50 and changes to 52, the system will not register this variation in the database, because it is less than 5. If the change is equal to or greater than 5, the new value will be saved to the history file.

Field

When History Format is Database, this is the name of the field (in the SQL database table) where the trend history will be saved. If this field is left blank, the project tag name will be used.

For array tags and classes, special characters ([].) will be replaced by underscores (_), as shown in the examples below:

Historian Tag

When History Format is Historian, this is the name of the tag (in the Historian database) where the trend history will be saved. If this field is left blank, the project tag name will be used.

When you save a Trend worksheet, only the header settings are saved as part of the worksheet file. All of the trend configurations that make up the body of the worksheet are actually saved as tag properties. The next time you open that worksheet, the tags database is scanned for all trend configurations that belong to the worksheet (that is, the trend group), and then that information is used to recreate the body of the worksheet. This happens quickly and automatically every time you open the worksheet, so it might seem like you are opening a static file but that is not the case.

You may think of the Trend worksheet as an editor for those tag properties that are related to history. If you use either the Tag Properties dialog box or the TagsDBSetTrend function to edit the same properties, the updated trend configurations will be included in the body of the worksheet the next time you open it. In fact, you can set trends on tags before you create any Trend worksheets at all; when you do create the worksheets, they will be automatically populated with trend configurations according to their group numbers.

You cannot configure more than one trend on a given tag, and each trend configuration cannot belong to more than one group/worksheet.

If you make extensive changes to the tags database after you save an Trend worksheet, it might not be possible to recreate the body of the worksheet the next time you open it. For example, if you copy all of the tags from the tags database (in Datasheet View) to a spreadsheet program, use that program to sort the tags, and then copy the tags back to the tags database, most or all of the tag properties will be reset in the process.

Note: The Trend task can accept only up to 1000 tags in a single worksheet. If you manually configure more than 1000 tags in the same worksheet, the Trend task will generate an error during project run time.