Resolving Disabled 'Acknowledge Error' Button in CEMAT C_MEASUR WinCC Faceplate

In SIMATIC PCS 7 running the CEMAT Minerals library, the 'ACKNOWLEDGE ERROR' button on the C_MEASUR (FB1006) faceplate becoming disabled or greyed out after operator login is caused by missing User Authorization levels in the WinCC User Administrator. While anonymous or default engineering sessions may permit open button access, logging in with an operator user activates WinCC security checking. In CEMAT, resetting latched measuring point errors and acknowledging faults requires User Authorization Level 5 (Process Control / Operation) or Level 6 (Higher Process Control / Interlock Override). Assigning these authorization levels to the operator's user group in WinCC User Administrator immediately restores the acknowledgment button.

CEMAT Security Architecture and Measuring Point Fault Latching

In heavy industrial plants operating with the SIMATIC PCS 7 CEMAT Minerals library (6ES7658-2BC58-0YA5), the Measuring Point Block (C_MEASUR, FB1006) monitors critical process transmitters (bearing temperatures, motor vibrations, kiln pressures, gas analyzers). To prevent equipment damage, CEMAT implements safety latching: when an analog measurement crosses a critical limit (e.g. Upper Limit 2 - Trip), the fault condition latches in controller memory.

Even after the physical process variable returns to a safe operating band, the measuring point remains in a faulted, interlocked state until an authorized plant operator clicks the ACKNOWLEDGE ERROR button on the @PG_C_MEASUR.PDL faceplate.

Root Cause of Disabled Acknowledgment Buttons Upon User Login

Commissioning engineers frequently encounter an apparent paradox:

Before User Login: In a freshly opened WinCC Runtime session where no specific user is logged in (or where default administrator bypass is active), the 'ACKNOWLEDGE ERROR' button appears highlighted and clickable.
After Logging In as an Operator: The moment a plant operator logs in via the WinCC login dialog, the 'ACKNOWLEDGE ERROR' button immediately grays out and becomes disabled.

The technical mechanism: The C-action script driving button property Enable inside @PG_C_MEASUR.PDL calls the CEMAT security function cemat_user_auth.c. This function queries the active user's permissions in the WinCC User Administrator. If the logged-in user account lacks Authorization Level 5 (Standard Operation) or Authorization Level 6 (Higher Operation / Fault Acknowledgment), the script actively locks the button to enforce operational security.

Comparison of CEMAT User Authorization Levels in WinCC

The following table compares standard CEMAT authorization levels and their operational authorities:

Authorization LevelLevel NameFaceplate Capabilities GrantedAcknowledge Error Enabled?Level 1System Monitoring / View OnlyOpen faceplates, view trends, inspect diagnosticsNO (Disabled)Level 2Basic OperationAcknowledge standard alarms, toggle overview displaysNO (Disabled)Level 5Process Control (Standard Operator)Start/stop drives, stroke valves, auto/manual mode switchYES (Standard faults)Level 6Higher Process Control (Supervisor)Acknowledge trip errors, override interlocks, reset faultsYES (All fault classes)Level 20CEMAT Engineering / MaintenanceForce simulation, alter filter times, edit limit parametersYES (Full engineering control)Anonymous / Logged OffDefault Guest UserDetermined by fallback security level in User AdministratorDepends on guest configuration

Step-by-Step Procedure to Grant Authorization in User Administrator

Follow this procedure in WinCC Explorer to restore the acknowledgment button for operator groups:

Open User Administrator in WinCC Explorer:
- Launch WinCC Explorer on the Engineering Station (or OS Server).
- Double-click the User Administrator editor.
Verify User Authorization Levels Configuration:
- In the navigation pane, expand Authorizations.
- Verify that Authorization Level 5 is defined as Process Control and Level 6 is defined as Higher Process Control.
Assign Levels to Operator User Group:
- Expand Groups and select the operator group (e.g. Operators or Plant_Area_A).
- In the right-hand permissions table, locate Level 5 and Level 6.
- Check the boxes to enable both authorization levels for the group.
- Ensure the specific operator user account belongs to this group.
Deploy and Download to OS Servers:
- Save the User Administrator configuration.
- Download the updated WinCC project to the OS Server and OS Client stations (or compile OS if required).
- On the runtime workstation, log out and log in again with the operator user account.

Verification

Verify fault acknowledgment operation in WinCC Runtime:
1. Log in with the updated operator credentials.
2. Open the faceplate for a faulted measuring point (C_MEASUR).
3. Confirm that the ACKNOWLEDGE ERROR button is illuminated, blue/grey, and fully clickable.
4. Click ACKNOWLEDGE ERROR. Confirm that the latched fault status clears and the measuring point indicator returns to green (healthy).

Limitations and Operational Precautions

Process Safety of Fault Acknowledgment: Acknowledging an error on a critical measuring point (e.g. bearing over-temperature) permits equipment restarts. Operators must physically verify field conditions before acknowledging trip faults.
Domain Controller vs Local User Management: In domain-integrated PCS 7 installations using SIMATIC Logon, authorization levels are mapped to Windows Active Directory security groups. Update the corresponding AD security group in User Administrator.
Web Navigator Clients: For operators accessing faceplates via WinCC Web Navigator, ensure the Web Navigator user profile is assigned identical User Administrator permissions.

Engineer FAQ

Why was the button enabled before I logged in?

Before logging in, WinCC evaluated permissions against the default guest profile or an unauthenticated engineering session that lacked permission enforcement. Logging in activated user-level security checking.

What authorization level is required to acknowledge CEMAT errors?

Authorization Level 5 (Process Control) or Level 6 (Higher Process Control / Interlock Override) is required in WinCC User Administrator to enable error acknowledgment on CEMAT faceplates.

Can I acknowledge measuring errors from the group faceplate?

Yes. The CEMAT group block C_GROUP features a collective fault acknowledgment command that broadcasts error resets across all child measuring points and drives assigned to that technological group.