Understand trend pen historical data retrieval

When an application containing a Trend Pen starts running, a Historian query retrieves data for the entire Trend Pen period. Real-time data is plotted on the trend line during the period that historical data is being retrieved. After retrieving historical data, it is added to real-time data to back fill the trend line for the entire period.

The following procedure shows the steps to configure a Trend Pen. Typically, configuring a Trend Pen includes several steps to place the Trend Pen next to a meter graphic to visually indicate the Trend Pen plot shows the changes in the graphic’s process value over time.

To configure Trend Pen

1. Select Trend Pen from the Visualization folder.

   The cursor changes to a cross hair when placed over the Industrial Graphic Editor canvas area.

2. Place the cursor over the canvas at the position you want to set as a horizontal boundary of the Trend Pen plot.

3. On the canvas, drag to select the rectangle for the Trend Pen control.

   The horizontal and vertical boundaries of the Trend Pen rectangle represent the drawing area of Trend Pen plot during run time. The horizontal axis of the graphic rectangle represents the time period of the trend. The vertical axis represents the range of the trend’s possible values.

   

   The Trend Pen dialog box appears. You can also show the Trend Pen dialog box by double-clicking on the Trend Pen graphic or selecting Edit Animations from the Special menu.

4. Enter a reference in the Reference field.

   The reference is the data source that appears as the value shown by the trend, which can be an external reference like an object’s attribute, an analog tag value, or a custom property. Constants and expressions are not allowed.

5. Select Historian or InTouch Log History/LGH for the Historical Source. If you select Historian proceed with Step 7.

6. On selecting InTouch Log History/LGH you can use the icon against the UNC Path to toggle input to the field as an Expression or Static text.

   • If you select the Expression mode, you can select the ellipsis button to launch your HMI's attribute/tag browser and select a Custom property, attribute or tag.

   • If you select the Static Text mode, you can select the ellipsis button to launch the file browser where you can specify the LGH file name.

7. Select Auto-Detect or Expression for the method to identify the location of the Historian.

   • Auto-Detect:The Historian server is auto-detected from the AppEngine on which the reference attribute is running. For example, if the Reference field is set to UDO.UDA1, then Auto-Detect is set to the Historian server name configured for the AppEngine on which UDO is running. Auto-Detect is only valid for Application Server References.

   • Expression: When an expression or reference is entered in the Server Name field, the Trend Pen connects to the specified Historian Server.

   The icon to the left of the Server Name field toggles input to the field as an expression or Static Text mode.

   A Trend Pen only shows live data if the Server Name field is left blank in Expression mode.

8. Select Moving or Fixed as the type of trend time period.

   • Moving: The start time of a trend period is the current time, and the end time is the duration of the time period from the start time. The start time for the next period is set to the end time of the previous trend period.

   • Fixed: In a Fixed trend time period, the StartTime and EndTime properties do not change automatically. The start time of a trend period is the current time initially. The StartTime property can be changed by a script.

   The EndTime property of a trend period (both Moving and Fixed) is read-only. The end time of a trend period is calculated from the specified start time and duration of the period.

9. Set the X-axis time period of the trend line in the Duration (Minutes) field.

   The trend time period can be specified as a constant, an external reference, an expression, or custom property. If a floating point number is entered, the period is rounded up to the nearest minute.

   The minimum trend period is 1 minute and the maximum period is 10080 minutes (1week).

10. Select Auto-Range or Clip out of Range Values for the scaling method to place process values on a trend line.

    If Auto-Range is selected, the Min Range and Max Range fields are disabled. The Y-axis of the trend line is automatically adjusted to show the full range of trend values within the upper and lower boundaries of the Trend Pen graphic.

    If Clip out of Range Values is selected, the Min Range and Max Range fields are enabled. Min Range and Max Range set the lower and upper limits of the trend’s Y-axis value range. Both fields can be set to constants, external references, or custom properties.

    When a value exceeds the trend’s minimum or maximum limits using Clip out of Range Values, the trend line is truncated at the limit of the value range and appears as a horizontal line for the period when the process value is out of trend’s value range.

11. From Plot Type, select Step Line or Line as the type of trend plot.

    • A Step Line plot draws a horizontal line from a trend data point to the time of the next data point on the trend’s X-axis, and then draws a vertical line to the data point.

    • A Line plot draws a line directly to each successive point within the trend period.