Displaying Curve Names and Live Values in WinCC TrendControl

To display the descriptive technological tag name (e.g., 'Motor Temperature M1') and live cursor values directly alongside curves in the WinCC TrendControl in SIMATIC PCS 7, interconnect the WinCC RulerControl with the WinCC TrendControl, or configure the integrated Trend Window Table. In the WinCC Graphics Designer, place a WinCC RulerControl adjacent to the TrendControl and link its 'Trend Control' source property to the trend display object. When an operator moves the ruler cursor across the trend, the RulerControl dynamically displays the curve name, exact timestamp, and numerical value with engineering units in a fixed, high-legibility readout pane.

Trend Visualization Architecture in WinCC and PCS 7

In SIMATIC PCS 7, real-time and historical process values are visualized using the WinCC TrendControl (OnlineTrendControl). Whether embedded in plant overview screens or launched dynamically from APL faceplate 'Trend' views, the control plots up to 12 distinct analog curves across shared or independent Y-axes.

When multiple curves (e.g., motor bearing temperature, winding temperature, and motor current) share the same trend display area, differentiating curves solely by line color can cause operator confusion. Control engineers frequently seek a mechanism to affix technological names (such as 'M1 Bearing Temp') directly to the moving graphic curve.

Why Static Curve Labels Are Impractical on Real-Time Trends

In scrolling real-time trend displays, affixing a physical floating label directly onto a curve is impractical for several reasons:

Continuous X-Axis Movement: As time progresses, process values shift continuously to the left. A floating text label would either obscure the waveform or collide with neighboring curve labels during rapid process swings.
Dynamic Scaling: When an operator zooms in or auto-scales Y-axes, coordinate offsets shift dynamically.
Standard Ergonomic Solution: Siemens resolves this through two standardized mechanisms: the Integrated Trend Table (legend bar at the bottom of the trend) and the WinCC RulerControl (interactive cursor tool).

Interconnecting WinCC RulerControl with TrendControl

The WinCC RulerControl is a dedicated companion object for the TrendControl:

Cursor Synchronization: When the operator clicks anywhere on the trend canvas or enables the ruler tool, a vertical hairline cursor appears spanning all active curves.
Data Extraction: The RulerControl automatically reads the exact timestamp, curve name, technological tag comment, interpolated historical value, and engineering units at that exact cursor position.
Fixed Readout Window: The values are displayed in a clean, tabular format positioned above, below, or inside the trend frame, providing instant curve identification without graphical clutter.

Comparison of Trend Legend and Curve Identification Options

The table below contrasts the different methods for identifying curves in WinCC TrendControl.

Identification MechanismVisual PresentationInteractivitySurvives Zoom & Pan?Operator ErgonomicsWinCC RulerControlLinked separate table windowHigh: Interactive cursor clickYes: Tracks precise time sliceOptimal: Highly detailed diagnosticsIntegrated Trend TableTable row at base of TrendControlMedium: Shows min, max, currentYes: Static layoutStandard: Excellent baseline viewColor Legend BarSmall colored squares with namesLow: Static text displayYesGood for basic differentiationStatic Text BoxesText objects pasted on canvasNone: Fixed screen coordinatesNO (Waveform moves away)Unusable on real-time scrolling trends

Step-by-Step Procedure to Link RulerControl to TrendControl

Follow this procedure in the WinCC Graphics Designer to interconnect RulerControl and TrendControl:

Insert TrendControl and RulerControl Objects:
- In Graphics Designer, open the target picture (e.g., Motor_Trends.pdl).
- From the Object Palette under Controls, insert a WinCC TrendControl.
- In the same picture, insert a WinCC RulerControl (typically positioned directly below or above the trend).
Name the Graphic Controls:
- Open the properties of the TrendControl: set object name to Control1.
- Open the properties of the RulerControl: set object name to RulerControl1.
Establish Software Linkage:
- Open the Configuration Dialog of the WinCC RulerControl (double-click the object).
- In the General tab, locate parameter Trend Control.
- Select Control1 from the dropdown list: this establishes the bidirectional communication link between the two controls.
Configure Displayed Columns in RulerControl:
- In the RulerControl dialog, switch to the Columns tab.
- Enable columns: Trend Name, Value, Unit, and Time.
- Click OK and save the picture.

Verification

Verify trend and ruler functionality through the following operational tests:
1. Launch WinCC Runtime and open the trend screen.
2. Click the 'Ruler' button on the TrendControl toolbar (or click anywhere on the trend graphic canvas).
3. Verify that the vertical cursor line appears on the trend and that the linked RulerControl immediately populates with the curve names (e.g., 'M1 Bearing Temp'), live values, and units.
4. Drag the ruler line left and right: confirm that values in the RulerControl update dynamically to match the historical waveform.

Limitations and Operational Precautions

When configuring trend curves linked to archive tags in WinCC Tag Logging, ensure that the archive cycle is sufficiently fast to capture process dynamics. If an analog value is archived every 10 seconds, zooming in to a 1-minute window will show stepped, interpolated line segments. For high-speed mechanical drives, configure cyclic selective archiving with deadband compression.

Engineer FAQ

Can I show curve names in the APL faceplate Trend view?

Yes. In standard APL faceplates, clicking the Trend tab opens @PG_[blocktype]_Trend.pdl. The integrated TrendControl includes a lower table bar where curve names, units, and limits are displayed automatically.

Can I customize the color and thickness of individual trend curves?

Yes. In the TrendControl configuration dialog under the 'Trends' tab, you can customize line color, line style (solid, dashed), line weight (1 to 5 pixels), and point markers for each configured curve.

How do I export data displayed in the RulerControl to Excel?

Click the 'Export' icon on the WinCC TrendControl toolbar. The control exports all logged points within the selected time window to a CSV file that can be opened directly in Microsoft Excel.