Troubleshooting Empty Alarm History on SIMATIC TP900 HMI Panels

Problem Description

A SIMATIC TP900 panel connected to a S7-1200 CPU 1214C via TIA Portal V15.1 displays real-time alarms correctly in the alarm view, but the alarm history screen remains empty. No archived or logged alarm records are shown when the operator navigates to the historical alarm view, even though the runtime is online and discrete alarm tags are actively triggering.

This is one of the most common configuration faults when commissioning SIMATIC Comfort Panels, because alarm logging involves four separate layers that must each be correctly configured: a storage location, a logging task, an alarm class assignment, and a view filter. If any one of them is missing or misconfigured, the history view returns an empty result set without raising an error in the engineering environment.

Affected Hardware and Software

The reference documentation for alarm logging on this generation of Comfort Panels is the SIMATIC STEP 7 Basic/Professional V15.1 and SIMATIC WinCC V15.1 system manual, available from Siemens Industry Online Support: SIMATIC STEP 7 / WinCC V15.1 system manual (109755202).

Root Cause Analysis

Five independent root causes can each produce this exact symptom. Identify which applies before changing settings.

Diagnostic Procedure

1. Open the HMI project in TIA Portal V15.1 and expand HMI_1 → Alarm logs in the project tree.
2. Right-click the configured log (default name AlarmLog) and confirm a storage location is assigned. If the field is empty, this is RC2.
3. Open the log's Properties → General tab and verify the Runtime persistence checkbox is enabled. If unchecked, the buffer exists only in memory and is lost on power-off or panel restart. This is RC1.
4. Compile the project, download to the TP900, and let it run for at least 60 seconds with at least one alarm active.
5. Check the configured storage path (typically /media/simatic/HMI/alarms on the USB stick) on a PC. If the .csv or .rdb log file is missing or 0 bytes, see RC2 or RC3.
6. On the panel, navigate to Control Panel → System Messages and look for messages 130001–130005. These identify the exact failure path.
7. Open the runtime alarm history view on the panel. Right-click the view and select Filter. Confirm the Display archived alarms / Display logged alarms box is checked. If unchecked, this is RC4.
8. Confirm the filter time range covers the current shift. By default, the history filter may be set to "Today" only and will hide logs from the previous day.

Solution 1: Enable Runtime Persistence for the Internal Buffer

The single most common root cause is a missing persistence flag. On SIMATIC Comfort Panels the alarm log is a segmented circular log; the segments are written to a file only if persistence is enabled, and the storage location points to a writeable runtime medium.

1. In the project tree select HMI_1 → Alarm logs → <your_log>.
2. In the work area switch to the Properties inspector.
3. Open General → Storage location and select Storage medium (USB) or Network (mapped SMB share).
   If the field is greyed out, the runtime license does not include archiving — required option: WinCC Comfort/Advanced with the "Archives" option set.
4. Set Runtime persistence = Enabled (the property labelled "Persistent storage" in some builds).
5. Set Number of segments = 1 (minimum) and Segment size = 1000 records for a typical commissioning log.
6. Compile → Download (full, not delta) → Restart runtime.

Solution 2: Configure USB Storage for the Alarm Log

Comfort Panels recognise only a constrained set of USB media. The supported envelope is:

1. Format the USB stick as FAT32 (Windows: format X: /FS:FAT32 /Q). Do not use the exFAT default offered by Windows 10/11 on large media.
2. Insert the stick into the TP900 before powering the panel.
3. Power on. The panel mounts the medium as /media/simatic/<label>. The label is taken from the volume name.
4. In the project, under Runtime settings → Alarm logs, set the storage path to /media/simatic/<label>/Logs or simply /media/simatic/ to let the runtime create its own subdirectory.
5. Verify the runtime detects the medium: trigger a known alarm and check the USB stick contents from a PC. The expected file is AlarmLog_<hmi_name>_<date>.csv or .rdb depending on the export format configured.

Solution 3: Review the Alarm Viewer Filter Configuration

The alarm viewer has two tabs in its properties that govern what is shown in the history view: the Display tab and the Filter tab. Both must permit archived records.

1. Open the screen that contains the alarm history control and double-click the control.
2. In the Properties → General pane, ensure the control type is Alarm view and the View mode is set to History (not Active and not Statistics).
3. Switch to the Properties → Filter pane. Check:
   – Show logged alarms = true
   – Show archived alarms = true
   – Filter by time range = disabled, or set to cover the full shift
   – Filter by alarm class = "All" or include Errors, Warnings, System as needed
4. If a PLC-side filter is also configured via the AlarmViewConfig tag, verify the tag value at runtime. The filter bitmask is bit 0 = Acknowledged, bit 1 = Unacknowledged, bit 2 = Logged, bit 3 = Archived.

System Messages and HMI Event Log Reference

When the log cannot be created, the TP900 runtime emits a system message. Use the table below to map the message to the root cause and the corrective action.

Verification Procedure

1. With the panel in runtime, force a known alarm: set a bit in the PLC that is mapped to a discrete alarm in the HMI tag table.
2. Acknowledge the alarm, then clear the trigger condition.
3. Open the alarm history view. The alarm must appear with timestamp, state, and acknowledgement status.
4. Power-cycle the panel. After the restart, navigate back to the alarm history. The record must still be present (proves persistence is working).
5. Remove the USB stick and connect it to a PC. Confirm the file AlarmLog_*.csv exists and contains the same record.
6. If the history is empty but the CSV is populated, the filter on the alarm view is the cause (RC4).
7. If the CSV is empty but the live alarm appeared, persistence is disabled (RC1) or the storage path is not being written to (RC2/RC3).

Best Practices for TP900 Alarm Logging

• Use the internal buffer for commissioning, USB for production. During commissioning keep persistence off and the storage location empty; the runtime keeps the last 1024 alarms in volatile RAM and the history view shows them. Switch to persistent USB logging only when the system is handed over to operations, so the volatile buffer is not consumed by commissioning noise.
• Match the engineering version to the runtime image. A V15.1 engineering project compiled against a V15.0 or V16 runtime can produce silent logging failures. Use Online → HMI operator panel & version to confirm.
• Configure segment size based on alarm rate. With 200 alarms/min and a 1000-record segment, you retain 5 minutes of history per segment. Size for the longest expected investigation window plus 50% margin.
• Set the storage path relative to a label, not a serial number. The volume label of the USB stick is stable; the device node (sda1, sdb1) is not. Always reference /media/simatic/<label>/....
• Test the fail-state before handover. Pull the USB stick during runtime. The panel must either buffer to RAM (persistence off) or emit a system message (persistence on). An undetected failure is worse than a logged one.
• Tag the log file with the HMI station name. In the log's Properties → General → File name, use the placeholder <hmi_name> so each panel writes to a uniquely named file when multiple TP900s share a network share.
• Disable the alarm filter by default. Many field engineers enable the time-range filter during commissioning to keep the test record short, then forget to widen it for production. Add a reminder in the project's release notes.

Frequently Asked Questions