Configuring Multiple Trend Curves in WinCC Online Trend Control

1. Overview

The WinCC Online Trend Control is a standard HMI/SCADA active-X widget shipped with the WinCC Graphics Designer. A single control instance can render N independent trend curves, each bound to its own tag, color, line type, scaling, and value axis. When the operator or engineer needs to monitor a homogeneous set of process variables – for example 8 furnace-zone temperatures, 10 vibration channels on a compressor, or 30 power-meter readings – the requirement becomes: configure the first curve to the desired look-and-feel, then replicate that configuration across every additional curve without manually re-entering each property.

This reference documents three field-proven methods to propagate trend-curve properties inside a single Online Trend Control, all of them based on the Index property exposed by the control:

• C script inside the WinCC Global Script Editor for runtime initialization of all curves from one template curve.
• VBA macro invoked from the Graphics Designer for design-time (PDL) property duplication.
• VBScript attached to a button event for online edits while the runtime is running.

All three approaches are built on the same underlying mechanism: each property dialog (color, line width, time axis, value axis, archive selector, etc.) is internally redirected to the curve referenced by the Index property (0-based). Writing a script that walks Index from 0 to N-1 and applies the template's parameter set to every index is the canonical solution.

2. The Online Trend Control Object Model

The control is exposed in the Graphics Designer as a single ActiveX instance named by default WinCC Online Trend Control. Underneath the COM veneer every "curve" is a row in the control's internal TrendCurves collection. The following properties and methods are relevant to property propagation:

The full list of Trend Control properties is documented in the WinCC Information System under Working with WinCC > Visualizing processes > Displaying process values > Working with controls > WinCC Online Trend Control. Siemens Knowledge Base article 50353471 demonstrates ruler read-out, which uses the same Index-based property dispatch.

3. The Index Property Mechanism – Why It Works

Every property dialog opened on the Online Trend Control contains an internal curve selector. When the engineer selects curve #2 in the dialog and changes the color, the dialog writes the color value to TrendCurves[1].Color. The dialog itself does not store a "selected curve" instance – it stores only the index. This means a C, VBS, or VBA client can implement exactly the same pattern by setting Index first and then writing each property in turn:

The mechanism is officially documented in WinCC Information System under Online Trend Control > Configuring the Trend Display > Curve Selection. Setting Index is the only way to direct subsequent property writes to a particular curve without enumerating the TrendCurves collection directly (which is not supported in WinCC V7).

4. C Script Method (Global Script Editor)

This is the recommended approach for engineers who maintain a centralized function library in Global Script > C-Editor. The function can be invoked from any PDL on the project, making it ideal for projects with many screens that all need identically-configured trend controls.

4.1 Sample function – CopyTrendCurve

// CopyTrendCurve.cpp - WinCC Global Script (C-Editor)
// Source curve is always Index 0 (the template).
// Target curves are Index 1..N-1. The script copies every relevant
// property of curve 0 onto each subsequent curve, then re-assigns the TagName.
#include "apdefap.h"

void CopyTrendCurve(char* szScreen, char* szTrend, int iCurveCount)
{
    // 1. Snapshot template (Index = 0)
    SetPropWord(szScreen, szTrend, "Index", 0);

    DWORD  dwColor     = GetPropWord(szScreen, szTrend, "Color");
    WORD   wLineType   = GetPropWord(szScreen, szTrend, "LineType");
    WORD   wLineWidth  = GetPropWord(szScreen, szTrend, "LineWidth");
    WORD   wValueAxis  = GetPropWord(szScreen, szTrend, "ValueAxis");
    WORD   wRelayBits  = GetPropWord(szScreen, szTrend, "RelayCurves");
    float  fGridValue  = GetPropFloat(szScreen, szTrend, "GridLineValue");
    BOOL   bCommonY    = GetPropBool(szScreen, szTrend, "CommonY");
    BOOL   bAutorange  = GetPropBool(szScreen, szTrend, "Autorange");

    // 2. Replay onto curves 1 .. iCurveCount-1
    for (int i = 1; i < iCurveCount; i++)
    {
        SetPropWord (szScreen, szTrend, "Index",       (WORD)i);
        SetPropWord (szScreen, szTrend, "Color",       dwColor);
        SetPropWord (szScreen, szTrend, "LineType",    wLineType);
        SetPropWord (szScreen, szTrend, "LineWidth",   wLineWidth);
        SetPropWord (szScreen, szTrend, "ValueAxis",   wValueAxis);
        SetPropWord (szScreen, szTrend, "RelayCurves", wRelayBits);
        SetPropFloat(szScreen, szTrend, "GridLineValue", fGridValue);
        SetPropBool (szScreen, szTrend, "CommonY",     bCommonY);
        SetPropBool (szScreen, szTrend, "Autorange",   bAutorange);
    }

    // 3. Restore selection to the template curve
    SetPropWord(szScreen, szTrend, "Index", 0);
}

4.2 Assigning 8 temperature tags

// Called from a PDL open-event, e.g. "OnOpen" of screen "Trend_8Temperatures.pdl"
void OnOpen_PDL()
{
    const int N = 8;
    char* szScreen = "Trend_8Temperatures.pdl";
    char* szTrend  = "Trend_Control";

    // (1) Build the curve set – assumes TrendCurves 0..7 already exist
    //     and curve 0 is the fully-styled template.
    CopyTrendCurve(szScreen, szTrend, N);

    // (2) Re-bind TagName for curves 1..7 only
    char* taglist[8] = {
        "TEMPLATE_DO_NOT_BIND",   // curve 0 stays as visual reference
        "Furnace1_Temp",          // curve 1
        "Furnace2_Temp",          // curve 2
        "Furnace3_Temp",          // curve 3
        "Furnace4_Temp",          // curve 4
        "Furnace5_Temp",          // curve 5
        "Furnace6_Temp",          // curve 6
        "Furnace7_Temp"           // curve 7
    };

    for (int i = 1; i < N; i++)
    {
        SetPropWord(szScreen, szTrend, "Index", (WORD)i);
        SetPropChar(szScreen, szTrend, "TagName", taglist[i]);
    }
    SetPropWord(szScreen, szTrend, "Index", 0);
}

4.3 Parameter glossary for SetProp*/GetProp*

5. VBA Method (Design-Time, Graphics Designer)

Use VBA when the requirement is to build the PDL with N curves in the Graphics Designer and have all curves written into the picture file (so that the configuration survives a CS upgrade or a runtime re-installation). VBA operates on the in-process WinCC Graphics Designer automation model; it is the only way to perform mass property edits at design time without opening the property dialog 8 times.

5.1 Macro – DuplicateTrendCurves

' WinCC Graphics Designer - Tools > Macros > Visual Basic Editor
' Paste into a new module: "TrendMacros.bas"

Public Sub DuplicateTrendCurves(ctrlName As String, nCurves As Integer)
    Dim hm As HMIGO ' WinCC HMIGO automation handle (provided by WinCC VBA ext)
    Dim trend As Object
    Set trend = Application.ActiveDocument.HMIObjects(ctrlName)

    Dim i As Integer
    Dim colorRef As Long, lineTypeRef As Long, lineWidthRef As Long
    Dim valAxisRef As Long, gridValRef As Double, relayRef As Long

    ' Snapshot template (Index = 0)
    trend.Index = 0
    colorRef    = trend.Color
    lineTypeRef = trend.LineType
    lineWidthRef = trend.LineWidth
    valAxisRef  = trend.ValueAxis
    gridValRef  = trend.GridLineValue
    relayRef    = trend.RelayCurves

    ' Replay
    For i = 1 To nCurves - 1
        trend.Index = i
        trend.Color        = colorRef
        trend.LineType     = lineTypeRef
        trend.LineWidth    = lineWidthRef
        trend.ValueAxis    = valAxisRef
        trend.GridLineValue = gridValRef
        trend.RelayCurves  = relayRef
    Next i
    trend.Index = 0
End Sub

5.2 Macro execution

1. Open the target PDL in the Graphics Designer.
2. From the menu choose Tools > Macros > Visual Basic Editor (Alt+F11).
3. Insert > Module, paste the code above, save the module as TrendMacros.bas.
4. Back in the Graphics Designer, ensure the trend control has already had N curves added manually (curves are not creatable through VBA in WinCC V7; they must be pre-created or the macro can call a C-script helper).
5. Run the macro: Tools > Macros > Run, pick DuplicateTrendCurves, supply "Trend_Control" and 8.
6. Save the PDL. The curve properties are now persisted in the picture file.

6. VBScript Method (Runtime, button event)

For operators who want to clone the current trend configuration at runtime – for example to swap the 8 temperature tags to 8 vibration tags without restarting the runtime – use VBScript attached to a button event:

' WinCC Graphics Designer - Button "Reconfigure" - Event > Mouse Click > VBS Action
' Re-bind all 8 curves to a different tag family.

Dim screenName, ctrlName
screenName = "Trend_8Temperatures.pdl"
ctrlName   = "Trend_Control"

Dim newTags(7)
newTags(0) = "Vib_Motor_1"
newTags(1) = "Vib_Motor_2"
newTags(2) = "Vib_Motor_3"
newTags(3) = "Vib_Motor_4"
newTags(4) = "Vib_Motor_5"
newTags(5) = "Vib_Motor_6"
newTags(6) = "Vib_Motor_7"
newTags(7) = "Vib_Motor_8"

' Snapshot the visual properties of curve 0 (template)
Dim tColor, tLineType, tLineWidth, tValueAxis, tGrid
tColor    = HMIRuntime.Tags("@TREND_" & ctrlName & "_Color").Read       ' indirect read - placeholder
' In VBS you can also call:
tColor    = ScreenItems(ctrlName).Color       ' if control is on the active screen
tLineType = ScreenItems(ctrlName).LineType
tLineWidth = ScreenItems(ctrlName).LineWidth
tValueAxis = ScreenItems(ctrlName).ValueAxis
tGrid     = ScreenItems(ctrlName).GridLineValue

Dim i
For i = 0 To 7
    ScreenItems(ctrlName).Index = i
    ScreenItems(ctrlName).TagName = newTags(i)
    ' Reapply template properties
    ScreenItems(ctrlName).Color         = tColor
    ScreenItems(ctrlName).LineType      = tLineType
    ScreenItems(ctrlName).LineWidth     = tLineWidth
    ScreenItems(ctrlName).ValueAxis     = tValueAxis
    ScreenItems(ctrlName).GridLineValue = tGrid
Next
ScreenItems(ctrlName).Index = 0

7. Color and Line Type Reference

For 8-color curves the standard Microsoft Office 2016+ palette is recommended to maintain adequate contrast on black and white printers:

8. Workflow Checklist for the 8-Temperature PDL

1. Pre-flight. Verify WinCC V7.4 SP1 or later is installed and the trend control licence is present (WinCC/RC license, not just WinCC/CS).
2. Create the PDL. In the Graphics Designer, insert a WinCC Online Trend Control, name it Trend_Control, size it to the screen.
3. Add curves. In the property dialog open the Curves tab, add 8 curve entries. Configure curve 1 (Index 0) entirely – color, line type, width, time axis, value axis, archive selector, trigger tag.
4. Author the C script. Open Global Script > C-Editor, paste CopyTrendCurve into a new project function, compile.
5. Wire the script. Open the PDL, on the picture's Open event attach a C action calling CopyTrendCurve("Trend_8Temperatures.pdl","Trend_Control",8) followed by the tag-list re-binding.
6. Compile the PDL. Use File > Check > Compile to detect syntax errors before activating runtime.
7. Activate runtime. Start WinCC Runtime, navigate to the PDL, verify all 8 curves appear with identical visual properties but distinct tags.
8. Validate. Right-click the trend, choose Online Configuration, and confirm curves 2..8 show the same Y-axis range, color, and line width as curve 1.
9. Archive validation. Open the Tag Logging editor and confirm the 8 tag archives are correctly selected for each curve's archive-selector property.
10. Ruler readout. Right-click the trend and toggle the ruler. Use the technique in Siemens Knowledge Base 50353471 to script the readout if it must be exported.

9. Verification Procedure

Verification consists of three checks:

1. Visual check. At runtime the 8 curves must be visually identical in style except for color and tag values. Place a ruler at a known time and verify each curve reports the expected value.
2. Diagnostic dump. In the C-Editor add a temporary line:
   printf("Curve %d Color=%u LineType=%u ValueAxis=%u\r\n", i, GetPropWord(...,"Color"), GetPropWord(...,"LineType"), GetPropWord(...,"ValueAxis"));
   Capture the WinCC diagnostic window output (Alt+PrtSc on the diagnostics viewer) and confirm the values for curves 2..8 match curve 1.
3. Clipboard round-trip (optional). Right-click the trend, choose Copy (available since WinCC V7.3). The clipboard receives the values for all traces; paste into Notepad or Excel to compare the timestamps. The clipboard mechanism is described in Geo SCADA documentation for analogous trend export behavior, and in EcoStruxure Building Operation for trend log export – the WinCC Online Trend Control behaves identically: Edit > Copy or right-click Copy places tab-separated (curve/timestamp/value) rows on the clipboard.

10. Troubleshooting Matrix

11. Cross-Platform Notes (TIA Portal / RT Professional)

Engineers migrating WinCC V7 PDLs to TIA Portal V17..V20 should note the following differences when copying curve properties between trend views:

• The TIA WinCC RT Professional Trend View and Trend/Table View expose an Automation Interface where the same property names exist but the curve collection is accessible through HMIGO.TrendView.TrendArea.TrendCurves instead of being hidden behind an Index property.
• RT Professional supports a runtime Copy lines command in the trend/table view – the selected table rows (timestamps + values) are placed on the clipboard and can be pasted into Excel. This is documented at the TIA Portal V20 documentation portal.
• RT Professional does not support the legacy SetPropWord C-API. The equivalent in TIA is the WinCC Unified / Professional JavaScript API, e.g.:
  HMIRuntime.UI.SysFct.TrendView_SetProperty(lpszPictureName, "TrendView_1", "Index", 0);
• The clipboard mechanism for runtime trend export is conceptually identical to WinCC V7's Copy command and to the Schneider Electric Geo SCADA clipboard export – all three platforms produce a tab-separated rows of timestamp, curve1, curve2, …, curveN.

12. Field-Proven Caveats

• CS upgrade wipes runtime-only properties. If the C script that propagates properties runs only on OnOpen in runtime (not at picture compile), a WinCC Configuration Studio re-deployment will discard the runtime values. Either re-run the C script after every CS deploy, or commit the values into the picture file by running the script in the Graphics Designer before saving the PDL.
• Tag list order must match the curve order. The tag binding loop in section 4.2 assumes that curves 1..7 are physically the 2nd..8th entries in the control. If a colleague has reordered curves in the dialog, the binding will mis-align. Always re-bind by curve index, not by name.
• RelayCurves is a bitmask, not a per-curve boolean. Writing SetPropWord(..., "RelayCurves", 1) in a loop for each curve will overwrite all bits. Use RelayCurves = (1 << i) or pre-compute the final bitmask once and apply it identically to every curve.
• VBA cannot save if a project function has a compile error. Run a full Check > Compile before invoking VBA macros.
• Ruler readout in WinCC V7.0..V7.2. The output window for ruler coordinates must be enabled via the registry key HKLM\SOFTWARE\Siemens\WinCC\RT\TrendControl\RulerOutput (DWORD = 1). Knowledge Base 50353471 lists the exact procedure.