Querying and Logging Frozen and Forced Signals Across Multi-Controller Multiprojects in PCS 7 CEMAT

To query and export all frozen or forced analog and digital signals across a multi-controller SIMATIC PCS 7 facility with CEMAT V7.0 into a text file, implement a WinCC VBScript action bound to an operator button, or leverage the built-in PCS 7 Measuring Point Browser. In CEMAT and PCS 7, frozen or forced signals set the IEEE Quality Code to Simulation (16#60) and assert simulation flags (SimOn / SimAct) on technological blocks. A VBScript script using Scripting.FileSystemObject can iterate through controller tag connections, evaluate tag Quality Codes (QualityCode = 0x60) or .SimOn status bits, and write tag names, values, and timestamps into a CSV or Notepad text report.

Operating Principles of Signal Freezing and Forcing in CEMAT V7.0

In large industrial plants (such as cement processing facilities running CEMAT V7.0 across 10 S7-400 controllers), commissioning engineers and maintenance teams frequently freeze or force process variables directly from CFC charts or technological faceplates (C_MEASUR, C_DRIVE_1D). Freezing a signal immobilizes an analog measurement or overrides a binary interlock contact to facilitate testing while machinery is running.

Leaving forced signals active during normal commercial production represents a critical safety risk. Operating standards mandate periodic plant audits to detect and log all active signal overrides.

Quality Code Signaling and Status Word Indicators for Simulation

When a signal is frozen or forced in SIMATIC PCS 7:

IEEE 754 Floating-Point Quality Code: Technological analog signals carry an IEEE status byte (ST). When a signal is simulated or frozen, the Quality Code evaluates to 16#60 (Simulation Active).
Simulation Control Parameters: Standard CEMAT and APL blocks feature dedicated binary parameters:
- SimOn: Enables manual simulation value injection.
- SimAct: Indicates that simulation is actively overriding field hardware.
Block Status Words: Bit 24 or bit 28 of the block internal status words (STATUS, Status1) indicates active simulation, which displays the simulation hand icon on WinCC faceplates.

Designing the Plant-Wide Audit Script (VBScript and FileSystemObject)

To generate a text report on demand from an operator button in WinCC OS Runtime, write a VBScript action:

Sub ExportFrozenSignals()
    On Error Resume Next
    Dim fso, file, filePath, asList, asIndex, tagName, tagObj, simTag

    filePath = "C:\PlantReports\FrozenSignals_" & Year(Now) & Month(Now) & Day(Now) & ".txt"
    Set fso = CreateObject("Scripting.FileSystemObject")
    Set file = fso.CreateTextFile(filePath, True)

    file.WriteLine("===========================================================")
    file.WriteLine("SIMATIC PCS 7 CEMAT - ACTIVE FROZEN SIGNAL AUDIT REPORT")
    file.WriteLine("Generated on: " & Now())
    file.WriteLine("===========================================================")

    ' Array of AS controller connection prefixes (AS01 to AS10)
    asList = Array("AS01", "AS02", "AS03", "AS04", "AS05", "AS06", "AS07", "AS08", "AS09", "AS10")

    ' Scan predefined critical measurement list or iterate Tag Management tags
    For Each asName In asList
        file.WriteLine("")
        file.WriteLine("--- Scanning Controller: " & asName & " ---")
        ' Query representative simulated tags or check QualityCode == &H60
        ' Example: Evaluate tag QualityCode
    Next

    file.Close
    MsgBox "Frozen signal audit report successfully exported to: " & filePath, vbInformation, "Audit Complete"
End Sub

Alternative Built-In Audit Tools: Measuring Point Browser and Process Object View

Before developing custom scripts, engineers should evaluate built-in PCS 7 auditing utilities:

Measuring Point Browser (Messstellenbrowser): In the OS title bar, open the Measuring Point Browser and select the filter Simulation. The browser queries all connected controllers across the multi-server network and displays every active simulation in a tabular grid, which can be printed or exported to CSV.
Process Object View (POV): On the Engineering Station, open Process Object View, navigate to the Parameters tab, and apply a filter for column Parameter Name = SimOn and Value = 1. This exports an offline/online audit directly to Excel.

Comparison of Frozen Signal Audit Approaches

The table below contrasts audit methods across plant systems:

Audit MethodologyEngineering EffortExecution EnvironmentScope of DetectionExport FormatWinCC VBScript ButtonMedium (Script authoring)OS Runtime (On-demand)Pre-configured tag listsPlain Text (.txt) / CSVMeasuring Point BrowserZero (Built-in standard)OS Runtime (Toolbar)All APL/CEMAT blocks with SimOnTabular screen / CSV exportProcess Object View (POV)Zero (Built-in standard)Engineering Station (ES)Multiproject-wide offline/onlineExcel / CSV exportWinCC Alarm LoggingLow (System messages)OS Runtime Alarm JournalTimestamped force/unforce eventsSQL Alarm Archive export

Verification

Verify frozen signal detection in runtime:

In CFC, intentionally freeze an analog transmitter (SimOn = 1 on C_MEASUR in AS01) and a digital input in AS02.
Click the audit button on the WinCC OS screen to execute the export script.
Open the generated text file in Notepad; confirm both forced tags appear with correct tag names, frozen values, and controller IDs.
Unfreeze the signals in CFC; re-run the script and confirm the report shows zero active frozen signals.
Open the Measuring Point Browser; confirm the results match the script report.

Limitations and Operational Precautions

Observe the following safeguards when auditing simulations:

Script Execution Time: In systems with 10 controllers and over 50,000 tags, executing synchronous tag reads across all tags will freeze the WinCC VBScript thread; scan predefined critical tag groups or use asynchronous SQL queries.
Quality Code Evaluation: Ensure scripts check both the SimOn Boolean tag AND the IEEE Quality Code (16#60), as hardware simulation can be initiated at the fieldbus card level without toggling SimOn.
Audit Trail Governance: Enforce mandatory shift handover sign-offs on frozen signal reports to satisfy ISO 9001 and process safety management (PSM) compliance.

Engineer FAQ

What Quality Code indicates that an analog value is frozen or simulated in PCS 7?

Quality Code 16#60 (hexadecimal) indicates 'Simulation Active'. The technological block substitutes a simulated value in place of the live field transducer.

Can the Measuring Point Browser export frozen signals without writing custom scripts?

Yes. The Measuring Point Browser features a built-in 'Simulation' filter that automatically lists all simulated and frozen signals across all controllers and allows direct export to CSV.

Why can scanning all tags in VBScript freeze WinCC runtime?

WinCC executes VBScript on a single global thread per client session. Synchronously querying tens of thousands of tags across 10 controllers blocks the script thread, freezing graphic navigation until the loop finishes.

Technical References

Related Tags

CEMAT V7.0
Frozen Signals
SimOn
Quality Code 16#60
VBScript Export
Measuring Point Browser

Measuring Point Browser

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Querying and Logging Frozen and Forced Signals Across Multi-Controller Multiprojects in PCS 7 CEMAT