WinCC Quality Codes: Decoding Tag Status in Database Exports

Overview

When exporting tag data from Siemens WinCC through the Connectivity Pack OLE DB provider, the resulting Recordset exposes five fixed columns: ValueID, TimeStamp, RealValue, Quality, and Flags. Engineers consistently report confusion around the Quality column because the value is delivered as a raw 4-byte integer with no inline documentation. A value of 128 (decimal) is the most common observation and, once converted to hexadecimal (0x80), resolves to Good — the most desirable state, indicating the tag value is reliable and free of acquisition errors.

This reference consolidates the WinCC simplified quality codes, the underlying OPC quality byte layout, the sub-status bits, and the recommended handling logic for VBScript, VBA, C#, and SQL consumers reading tag archives via WinCC OLE DB or the RT/UNO archive providers.

Recordset Schema Reference

WinCC Simplified Quality Codes

The following codes are returned in the Quality field of any Recordset produced by the WinCC OLE DB Provider for tag archives, alarms, and the Connectivity Pack CC_AlgRtHmiRuntime interface. The codes conform to the major quality byte of the OPC DA 2.0/3.0 specification.

Bit-Level Quality Structure (OPC Mapping)

Although the Recordset returns the simplified byte, the full OPC quality word is 32 bits and follows this structure. The simplified codes above are the most significant byte (bits 31–24) when WinCC writes the full OPC quality word, which matters for clients using the OPC DA / OPC UA tunnel.

To extract just the major quality category (Bad / Uncertain / Good) in a script, mask with 0xC0 (192 decimal) and shift right by 6:

major = (quality AND &HC0) \ 64       ' VBScript
major = (quality & 0xC0) >> 6             ' C# / VB.NET
major = (quality & 192) / 64              ' VBA

To extract major + sub-status (the simplified code column), mask with 0xFC (252 decimal) and shift right by 2:

Where to Find the Official Documentation

Siemens publishes the canonical code list inside the WinCC Information System, the CHM help installed with every WinCC runtime and configuration client. The codes are not duplicated in the Connectivity Pack manual — they live in the shared Communication section. Navigate:

1. Start → SIMATIC → WinCC → WinCC Information System (opens the consolidated CHM, including all installed WinCC options).
2. Expand Communication.
3. Open Communication — Diagnosis.
4. Open Quality of Tags.
5. Open Quality Codes of Tags — this is the canonical list of simplified codes. Codes are presented in hexadecimal.

The same list appears in the printed WinCC V7.x / WinCC Professional manuals under chapter Communication > Diagnostics > Quality Codes of Tags, and in the WinCC TIA Portal help under WinCC Runtime Professional > Communication > Quality Codes.

Quality Code 128 in Practice

A value of 128 means the tag was successfully polled, the value is within the configured engineering-unit range, the PLC connection is up, no operator override is active, and the archive segment accepted the value without substitution. In production telemetry dashboards this is the “all clear” state and no special handling is required.

Common reasons quality is not 128:

• 0 (Bad) — PLC powered down, S7 connection in OPFAULT, or the tag was removed from the project but the archive table still references it.
• 8 (Bad / Not Connected) — Channel diagnostics show the partner is unreachable. Check NetPro / connection configuration.
• 20 (Bad / Last Usable Value) — Driver is in “freeze last value” mode. Adjust the channel’s “Behavior on failure” setting.
• 64 (Uncertain) — Often a sign of a SIMATIC S7 stop / run transition; some drivers mark values Uncertain during the first scan after a restart.
• 72 (Uncertain / Substitute) — Operator used the “Set/Modify Tag” function to inject a manual value for testing.
• 96 (Uncertain / EU Exceeded) — Raw process value is outside the tag’s configured linear scale (e.g., -32000 to 32000). Investigate scaling or sensor over-range.
• 192 (GoodLocal) — HMI is in simulation mode. Confirm the runtime is talking to the real PLC before trusting the values.

Scripting Examples

VBScript / VBA — safe read for export consumer

Function IsValueUsable(quality)
    Dim major, qcode
    qcode = (quality And &HFC) \ 2
    major = (quality And &HC0) \ 64
    Select Case major
        Case 3  ' 11 binary = GoodLocal
            IsValueUsable = True
            Exit Function
        Case 2  ' 10 binary = Good
            IsValueUsable = True
            Exit Function
        Case 1  ' 01 binary = Uncertain
            IsValueUsable = (qcode <> 36) ' 36 = Initial Value
            Exit Function
        Case 0  ' Bad
            IsValueUsable = False
    End Select
End Function

C# / .NET — bitmask helper

public static class WinCCQuality
{
    public enum Major { Bad = 0, Uncertain = 1, Good = 2, GoodLocal = 3 }

    public static Major GetMajor(int quality)
        => (Major)((quality & 0xC0) >> 6);

    public static bool IsUsable(int quality)
        => GetMajor(quality) >= Major.Uncertain
           && ((quality & 0xFC) >> 2) != 18; // 0x48 Substitute

    public static string Describe(int quality)
        => $"Q=0x{quality:X2} major={GetMajor(quality)}";
}

SQL — filter archives to “Good only”

SELECT TimeStamp, RealValue, Quality
FROM   dbo.Archive_<ProjectName>_LTG_<TagName>
WHERE  (Quality & 0xC0) = 0x80         -- Good major
   AND (Quality & 0xFC) = 0x80         -- No sub-status bits
   AND TimeStamp >= DATEADD(hour, -24, GETUTCDATE());

TIA Portal / WinCC Unified — GraphQL — filter alarms by quality

query LiveQuality {
  tags(name: "Tank1_Level") {
    value { value quality }
  }
}
// quality field returns the same simplified byte: 0x80 = Good

Troubleshooting Matrix

Channel and Driver Settings That Affect Quality

Two project-level settings change how the simplified quality code is built and forwarded to the archive:

1. SIMATIC S7 Channel → Properties → “Provide full quality code”. When disabled, the channel collapses all sub-status into a single Bad / Uncertain / Good bit. When enabled, the full 8-bit sub-status reaches the archive and is what the connectivity pack then exposes in the Quality column.
2. Tag → Properties → Limits → “Upper/lower limit”. Crossing a configured high/low limit flips bit 23 (High Limited) or bit 22 (Low Limited) of the full OPC quality word, which in turn changes the simplified code to 0x88 (Good + High limited = 136) or 0x84 (Good + Low limited = 132). Filter these out of compliance reports.

Verification Procedure

1. Open the WinCC Information System at Start → SIMATIC → WinCC → WinCC Information System and confirm the CHM build number matches your installed WinCC version (e.g., WinCC V7.5 SP1 Update 4 ships help dated 2021-08).
2. In the runtime, open the Tag Management editor and watch the “Quality” column while forcing a Bad condition (cycle PLC power).
3. From a VBScript on the same HMI, open a ADODB.Recordset against CC_AlgRtHmiRuntime and read the Quality column into the immediate window: ? Hex(rs("Quality")) should print 80 during normal operation.
4. Cross-check the OPC quality word using an OPC client (e.g., OPC Scout V10) on the same node.
5. Document the observed codes per tag; the simplified code list above is the contract your downstream exporter (Power BI, Excel, SQL warehouse) must honor.

FAQ