Problem Overview
When configuring a Trend View on a WinCC Comfort Panel in TIA Portal V13.0, engineers frequently report that the HMI can only display roughly 1 minute 40 seconds (1:40) of historical process data before the left edge of the chart begins to overwrite. This symptom appears even on projects that have just been compiled, and it persists regardless of which HMI tag is bound to the trend.
The observed boundary is directly tied to the Trend value property in the Trend View configuration dialog. In TIA Portal V13.0 this property has a maximum permitted value of 999, which under the default 100 ms acquisition rate corresponds to 999 × 0.1 s = 99.9 s ≈ 1:40.
Root Cause Analysis
The Trend View in WinCC Comfort and WinCC Advanced Runtime is a circular in-memory buffer on the HMI panel. The buffer is dimensioned by two parameters:
| Parameter | Location | Effect |
|---|---|---|
| Trend value (Number of trend values) | Properties → Trend → Trend value | Total count of samples kept in the rolling buffer |
| Acquisition cycle / Sampling rate (1 cycle / sample) | Trend tag settings / Trigger | Time interval between two consecutive samples |
| Update cycle | Properties → General | Refresh interval of the display (not the sampling rate) |
The maximum visible time window is given by:
T_window = N_samples × T_acquisition
where N_samples is the value of Trend value and T_acquisition is the configured acquisition cycle. The default of 100 ms with 999 samples therefore yields ~99.9 s. Any value older than T_window is overwritten in the ring buffer and is no longer displayable on the HMI.
Solution: Extend the Display Window by Adjusting the Sampling Cycle
The maximum number of trend values (999) is fixed in V13.0, so the only way to stretch the on-screen time window without upgrading is to lengthen the acquisition cycle. The trend then shows fewer samples per second, but the total history window grows proportionally.
Step-by-Step Procedure
- Open the project in TIA Portal V13.0 (or upgrade to V13 SP1 / V14 for the highest sample counts).
- In the project tree, navigate to Devices & Networks → the Comfort Panel → Screens and double-click the screen that hosts the Trend View.
- Click the Trend View object to select it, then open the Properties inspector (right pane, Properties → Trend).
- Set Trend value =
999(already at the V13.0 cap — do not reduce). - Under the Trend tag area, change the Acquisition cycle from the default 100 ms to a slower value such as 500 ms, 1 s, 2 s, or 5 s.
- Compile the HMI (Project → Compile → Software (rebuild all)) and download to the panel.
- Verify the new time window on the runtime using the Trend View's built-in ruler (right-click → Show Ruler).
Worked Calculation Examples (V13.0, N = 999)
| Acquisition cycle | Display window T_window | Use case |
|---|---|---|
| 100 ms (default) | ~1 min 40 s | Fast motion / current loops |
| 250 ms | ~4 min 10 s | Temperature trends |
| 500 ms | ~8 min 19 s | Pressure / level |
| 1 s | ~16 min 39 s | Slow process monitoring |
| 2 s | ~33 min 18 s | Batch overview |
| 5 s | ~1 h 23 min | Long-term shift overview |
| 10 s | ~2 h 46 min | Multi-shift reporting |
Apply the formula:
T_window [s] = 999 × Acquisition cycle [s]
To target a 5-minute (300 s) minimum window with V13.0, set the acquisition cycle to at least:
T_cycle = 300 / 999 ≈ 0.300 s ⇒ round up to 500 ms
T_cycle will be invisible. Always pick the slowest cycle that still preserves the smallest event the application must reproduce.
Alternative Solution: Use the f(x) Trend View (V13 SP1+)
For projects that must keep a high acquisition rate and a long display window, upgrade the project to TIA Portal V13 SP1 or later and replace the legacy Trend View with the f(x) Trend View control. Per the official Siemens application note, the f(x) Trend View is configured through the Tools → Task Card → Controls (Advanced) palette and supports:
- Up to 50,000 samples per trend channel on Comfort Panels, depending on available panel memory.
- Multiple value axes (left/right) and free Y-axis scaling.
- Statistics (min/max/mean) and online configuration.
- Trend transfer to a CSV file via script.
Reference: Creating an f(x) Trend View for Comfort Panels and Runtime (Siemens, DOC_v10).
Steps to Add the f(x) Trend View
- Upgrade the project to TIA Portal V13 SP1 or higher (File → Project → Upgrade).
- Open the screen editor and drag f(x) Trend View from the toolbox (Controls (Advanced)) onto the screen.
- Bind the trend channels to the desired HMI tags.
- Set Number of values per channel (e.g. 5000) and the Sampling interval.
- Compile and download.
Alternative Solution: Data Logging with Tag Logging
If long-term retention (hours, days, weeks) is the actual goal — not just the on-screen scroll-back — use the Tag Logging subsystem of WinCC Comfort / Advanced instead of the Trend View buffer.
| Feature | Trend View buffer | Tag Logging (HMI log) |
|---|---|---|
| Storage | RAM only (volatile) | Flash / SD card (persistent) |
| Capacity | 999 values (V13.0) | Limited only by media size |
| Display via | Trend View | Trend View, f(x) Trend View, Tables |
| Export | No | CSV export possible |
| Power-cycle safe | No | Yes (with ring/swap logging mode) |
Configure a Data log in Historical data → Data logs, then bind the Trend View to that log rather than to a live tag. Trend View will then scroll through logged history instead of an in-memory ring buffer.
Distinction from the S7-1500 / S7-1200 Trace Function
Engineers regularly confuse the HMI Trend View with the Trace function in S7-1500 (and S7-1200 firmware V4.0+). The two are independent:
| Property | WinCC Trend View (HMI) | S7-1500 / S7-1200 Trace (PLC) |
|---|---|---|
| Configured in | TIA Portal → HMI screens | TIA Portal → PLC → Traces |
| Storage | HMI RAM | PLC work memory / SIMATIC memory card |
| Max samples (typ.) | 999 (V13.0) / up to 50 000 (f(x), V13 SP1+) | Up to 524 288 per trace (S7-1500) / 16 384 (S7-1200 FW4) |
| Trigger model | Time / event | Bit, tag, FMC, math, time |
| Display | HMI screen | TIA Portal → Traces → Online view |
For PLC-side high-resolution capture, configure a Trace in Project tree → PLC → Traces. The trace can be downloaded to the PLC and triggered by an event (e.g. bit flip, threshold), then read back into TIA Portal for offline analysis — independent of any HMI display.
Runtime Professional (RT Professional) Considerations
On WinCC Runtime Professional (PC-based HMI), the Trend View operates differently. Refer to Using the trend and table view in Runtime (RT Professional) for current behaviour. In RT Professional:
- The trend buffer is configured by the property BufferSize of the TlgTrendWindow / F(x)TrendWindow control.
- Buffer size is in number of value pairs, not seconds; the time window depends on the configured Trigger (cyclic or event-driven).
- Toolbar buttons (Start, Stop, Print, Export, etc.) can be operated by C / VB scripts by passing the button's ID to the script. This is the standard pattern for automated trend exports.
Verification Steps
- Open the runtime on the Comfort Panel (or start RT simulation in TIA Portal).
- Right-click the Trend View and enable Show Ruler.
- Drag the right ruler handle to the rightmost data point; the timestamp label should now show the new end-time.
- Wait for the buffer to roll past
T_window; the oldest samples should disappear from the left. - Compare the displayed time span with the calculated
T_window = 999 × T_cycle— the values must match within ±1 acquisition cycle. - For tag-logged trends, power-cycle the panel; the history should reappear after restart (data logs only).
Troubleshooting Matrix
| Symptom | Likely cause | Corrective action |
|---|---|---|
| Trend stops at exactly 1:40 | V13.0 cap on Trend value with default 100 ms cycle | Increase acquisition cycle (e.g. 500 ms → 8:19 window) |
| Trend shows gaps | Acquisition cycle faster than the tag update from the PLC | Match cycle to PLC scan / update; verify tag acquisition is set to “On demand” or “Cyclic continuous” |
| Trend resets at reboot | Using RAM buffer only, no tag log | Configure a Data log and bind the trend to it |
| Cannot find “Trace” node in PLC | CPU does not support trace (e.g. S7-1200 FW < 4.0) or Trace license missing | Update firmware / use Trend View only |
| Trend View property Trend value greyed out | Trend is bound to a Log, not a live tag | Switch the source to a live tag, or extend the Data log configuration instead |
| f(x) Trend View not visible in toolbox | Project is still on V13.0 (no SP) | Upgrade to V13 SP1 or later |
| RT Professional trend does not scroll | Trigger set to “On change” with no tag changes | Change trigger to “Cyclic” with appropriate period |
Field-Proven Caveats
- Comfort Panel RAM. Setting Trend value to its maximum still consumes panel working memory. On TP700 Comfort a 999-sample buffer per channel is fine; on KP400 Comfort keep it under 500 to avoid memory alarms.
- Acquisition vs. Update cycle. These are independent. Acquisition cycle sets the sample rate; Update cycle sets how often the display redraws. Setting the update cycle shorter than the acquisition cycle wastes CPU.
- Logging rate on SD card. If the tag log writes faster than the card's write throughput, the HMI may drop samples silently. Use a Sandisk Industrial or Siemens SIMATIC SD card rated for industrial use.
- Project upgrades. After upgrading from V13.0 to V14 / V15 / V16 the legacy Trend View is kept unless you manually swap it. Consider the f(x) control for new projects.
Summary of Limits by TIA Portal Version
| TIA Portal version | Trend View type | Max samples | Typical 100 ms window |
|---|---|---|---|
| V13.0 (no SP) | Trend View (legacy) | 999 | ~1:40 |
| V13 SP1+ | Trend View (legacy) | 10 000+ | ~16+ min |
| V13 SP1+ | f(x) Trend View | Up to 50 000 | ~83 min |
| V14 / V15 / V16 / V17 | f(x) Trend View (RT Advanced) | Up to 50 000 (panel) / unlimited (RT Pro) | Configurable |
| V20 | WinCC Unified Trend Control | Configurable in Properties → Trend → Buffer size | Configurable |
Why does my WinCC Comfort Trend View only show 1 minute 40 seconds of data in TIA Portal V13.0?
You are hitting the V13.0 hard cap on the Trend value property (maximum 999) combined with the default 100 ms acquisition cycle. The time window equals 999 × 0.1 s ≈ 1:40. Lengthen the Acquisition cycle of the trend tag (e.g. 1 s → ~16:39 window) or upgrade the project to V13 SP1 and switch to the f(x) Trend View, which supports up to 50 000 samples.
How do I display more than 5 minutes of trend history on a Comfort Panel?
Two options: (1) keep V13.0 and set the acquisition cycle to at least 500 ms — this gives ~8:19 with 999 samples; or (2) upgrade to TIA Portal V13 SP1 or later, insert the f(x) Trend View, and set Number of values per channel to 10 000–50 000 with a 100 ms cycle for a 16–83 minute scroll-back. For retention across reboots, bind the trend to a Data log in Historical data.
Is the HMI Trend View the same as the S7-1500 / S7-1200 Trace function?
No. The Trend View is a WinCC Comfort / Advanced HMI feature that lives in panel RAM (max 999 samples in V13.0). The Trace function is a PLC-side feature in S7-1500 and S7-1200 (firmware V4.0+) that records up to 524 288 samples on the S7-1500 into controller memory and is viewed in TIA Portal → PLC → Traces → Online. They can be combined, but they are configured and stored independently.
Can I save trend data permanently and reload it after a power cycle?
Yes — use Historical data → Data logs in the HMI configuration. Define a logging tag, choose a logging cycle, select a storage path on the panel's internal flash or SD card, and bind the Trend View to that log instead of a live tag. The log persists across reboots and can be exported as CSV.
Does RT Professional have the same 999-sample limit as Comfort Panels?
No. WinCC Runtime Professional uses the TlgTrendWindow / F(x)TrendWindow controls, whose buffer is configured via the BufferSize property in number of value pairs. Buffer sizes of hundreds of thousands of values are typical, limited only by PC memory. See the official TIA Portal Help for RT Professional trend and table view for the exact property names and toolbar button IDs for scripted operation.