Step-by-Step Configuration of Online and Archive Trends Using WinCC Trend Control in PCS 7

In SIMATIC PCS 7 V9.0 SP2 (WinCC V7.4 SP1), configuring process value trends requires distinguishing between Online Trends (displaying transient live values directly from AS controller communication tags) and Archive Trends (displaying persistent historical curves retrieved from WinCC Tag Logging database archives). To configure an archive trend, first define the archive tag in the Tag Logging editor by selecting the process variable, acquisition cycle (e.g., 1 s or 5 s), and archiving parameters. Then, in Graphics Designer, insert the WinCC Online Trend Control from the standard controls palette, configure a trend curve linked to the Archive Tag source, set up time and value axes, and save the graphic picture. APL block faceplates automatically provide built-in trend views upon AS-OS compilation.

Executive Summary

Visualizing analog process dynamics through historical and real-time trend plots is essential for process optimization, batch tracking, and fault analysis in industrial control rooms. In PCS 7, engineers can provide operator trend displays via two primary mechanisms: the automatic trend views embedded inside standard APL faceplates, or custom full-screen trend displays embedded in WinCC process graphics. Control engineers frequently require guidance on properly establishing Tag Logging archives, assigning sampling cycles, and configuring the WinCC Online Trend Control ActiveX component. Understanding the workflow from AS tag acquisition to WinCC graphic display ensures responsive and accurate trend visualization.

Architecture and Fundamental Mechanics

The trend visualization and logging architecture in WinCC operates through distinct acquisition and presentation layers:

Online Trends vs. Archive Trends:
* Online Trends: The trend control queries the active WinCC Tag Management image cyclically. Data points are retained only in temporary client memory; closing the process screen or toggling views immediately purges the curve history.
* Archive Trends: The trend control queries historical database partitions (TagLoggingFast or TagLoggingSlow) managed by Microsoft SQL Server. Data remains permanently accessible across operator shifts, restarts, and historical audits.
The Tag Logging Acquisition and Archiving Hierarchy:
* Acquisition Cycle: Determines how frequently WinCC polls the AS controller over the Industrial Ethernet connection (e.g., every 500 ms, 1 s, 2 s).
* Archiving Cycle: Determines how frequently the acquired samples are written into the SQL database. An archiving cycle can evaluate mathematical algorithms (actual value, average, minimum, maximum) or apply deadband filters to reduce disk storage.
WinCC Online Trend Control Architecture:
* The WinCC Online Trend Control is a highly customizable container that supports multiple simultaneous curves (up to 300 trends per control).
* Each curve can have independent value axes (Y-axis), line colors, linear/stair interpolation modes, and statistical rulers.

Step-by-Step Implementation Procedure

Follow these procedures to configure an Archive Trend in PCS 7 V9.0 SP2 (WinCC V7.4 SP1):

Configure Archive Tag in Tag Logging Editor:
* In WinCC Explorer, double-click Tag Logging to open the editor.
* In the navigation tree, expand Archives and select Process Value Archive (or Fast/Slow archive).
* In the table, create a new archive tag (e.g., TT_101_PV_Out).
* In the Process tag column, browse WinCC Tag Management and select the engineering variable (e.g., Plant/Area1/TT_101.PV_Out#Value).
* Set Acquisition cycle (e.g., 1 s) and Archiving cycle (e.g., 1 s or 5 s).
* Save and close Tag Logging.
Insert WinCC Online Trend Control into Graphic Picture:
* In WinCC Explorer, open Graphics Designer and open the target process screen (.pdl).
* In the Standard palette under Controls, select WinCC Online Trend Control and draw a rectangle on the canvas.
* The configuration properties dialog opens automatically.
Configure Trend Curves and Data Source:
* In the properties dialog, go to the Trends tab.
* Click New to create a trend curve and assign a descriptive name (e.g., 'Reactor Temp').
* In the Data source drop-down menu, select Archive Tag.
* Click the Select... button and choose TT_101_PV_Out from the Tag Logging archive.
* Set the line display style (solid line, 2-pixel width, color red).
Configure Time and Value Axes:
* Go to the Time axes tab. Set the time range (e.g., 'Last 1 hour' or 'Last 15 minutes').
* Go to the Value axes tab. Configure scaling (e.g., minimum 0.0, maximum 150.0 °C, or select 'Auto-range').
Enable Toolbar and Ruler Controls:
* Go to the Toolbar tab.
* Check standard operator buttons: Zoom In/Out, Pan, Ruler, Export Data, and Print.
* Click OK to save the control properties and save the graphic picture (.pdl).
Activate Runtime and Verify Process Plotting:
* In WinCC Explorer, verify that Tag Logging Runtime is checked in Computer Properties under the Startup tab.
* Activate WinCC Runtime and open the newly configured process screen.

Verification

In WinCC Runtime, open the graphic screen containing the trend control. Verify that the trend curve displays the historical line smoothly. Click the Ruler button on the trend toolbar; move the cursor along the curve and confirm that the tooltip and ruler window display exact historical timestamps and temperatures. Toggle away to another graphic screen and return; confirm that the trend curve retains its full historical data without clearing.

Limitations and Operational Precautions

Ensure that the 'Tag Logging Runtime' component is checked in the OS Computer Startup properties; if unchecked, archive trends will display blank grids. High-frequency archiving of thousands of tags with 100 ms acquisition cycles can saturate SQL disk I/O; utilize deadband compression to optimize storage.

Engineer FAQ

What is the difference between an Online Tag and an Archive Tag in Trend Control?

An Online Tag reads transient memory values directly from the AS and clears upon screen change; an Archive Tag reads persistent historical data stored in the SQL Tag Logging database.

Why is my trend control blank in WinCC Runtime?

A blank trend typically occurs if 'Tag Logging Runtime' is disabled in Computer Startup properties, if the archive tag is unassigned, or if the OS Server archive is frozen.

How do I view trends in standard APL block icons?

Clicking the block icon opens the standard faceplate; clicking the 'Trend View' icon inside the faceplate automatically opens the pre-configured APL trend curve.