Configuring Trend View Value Selection in WinCC Advanced TIA Portal

This reference describes how to implement operator-selectable trend channels and runtime-adjustable axis scaling on a WinCC Advanced (TIA Portal V13 SP1 Update 5) HMI running on a SIMATIC KTP400 Basic Panel. Two field-proven methods are documented: a multi-overlay trend view with visibility animation, and a single-trend view with conditional tag-gating logic. Both methods respect the runtime limits of the WinCC Advanced Trend View control, which differ significantly from the WinCC Professional Trend Control.

1. Overview

The WinCC Advanced Trend View is a passive display control. It does not natively expose channel-enable flags per trend. Unlike WinCC Professional, where individual trend pens can be toggled through the Trend Control API, the Advanced control renders only the trends that are statically configured at compile time. Two architectural responses are possible:

• Visibility gating: Stack multiple Trend View objects, each with one pen, and animate the Visible property of each object through an HMI tag driven by an operator selector.
• Value gating: Use a single Trend View with all pens, and copy the source process value into the trend tag only when the operator has enabled that channel; otherwise write 0 (or hold the last value) to the trend tag.

Both approaches preserve the trend buffer and time axis. The choice between them depends on panel size, screen real estate, and the number of channels the operator must inspect concurrently.

Reference: Configuring a trend view for a data log (Panels, Comfort Panels, RT Advanced, RT Professional).

2. Prerequisites

3. Architecture: Selector, Visibility, and Scale Tags

Before touching the Trend View, define the tag schema. The pattern below scales to N trend channels. Only the first five are shown; extend as required.

The minimum panel memory footprint per channel is 8 bytes (REAL) + 1 bit (BOOL) + 4 bytes (REAL gate logic) when using the value-gate method. On a KTP400 with 1 MB project memory, plan for 32 trend channels maximum to stay below the 70% utilization threshold Siemens recommends for archive stability.

4. Method 1 — Multi-Trend Overlay with Visibility Control

This method is preferred when the operator benefits from comparing values on a single y-axis grid (e.g., temperature vs. pressure against the same time line). Stack one Trend View per channel in screen coordinates (0,0) through (W,H), all of identical size. The Visible property of each object is animated by the corresponding TrendSel_n tag.

4.1 Step-by-step

1. Open the screen where the trend will sit. Insert the Trend View five times (one per channel) and align them pixel-perfectly on top of each other. Tip: Use the Arrange > Align > Centered (vertical and horizontal) context menu items.
2. For each instance, open Properties > Trend > Trend type. Select Cyclic real time for live data or Data log for historical.
3. Bind the value source of the n-th Trend View to TrendValue_n. The internal trend tag is bound, not the raw process value; this isolates the gate logic from the pen binding.
4. Open Properties > Appearance > Visible for the n-th Trend View. In the animation dialog, select the TrendSel_n tag, set the trigger to Change, and the action to Visible = (tag value = 1).
5. Repeat for all five stacked objects.

4.2 Performance on KTP400

Each Trend View on a Basic panel redraws the full grid on every acquisition cycle. Five stacked views therefore execute five times the pixel work per cycle. With a 1-second acquisition and 5 channels, the panel CPU will be 8-12% busier than a single-view configuration. If you observe Response time of operator input > 1.5 s, drop acquisition to 2 s or use Method 2.

5. Method 2 — Single Trend with Value-Gate Tag Logic

This method is preferred when screen space is constrained or when more than four channels are required. The operator toggles a Boolean per channel; an HMI-side script (or scheduled task) copies the process value into TrendValue_n only when enabled, otherwise holds the value at 0.

5.1 Tag-gate scheduled task

Create a scheduled task in the HMI (TIA Portal > HMI device > Schedules > Add new) with a 500 ms trigger. Use VBScript inside the scheduled task to update the trend tags. A minimal implementation:

5.2 Single-trend view binding

1. Insert a single Trend View on the screen.
2. Add five trend pens. Bind each pen's Source to the corresponding TrendValue_n tag.
3. Configure one color per pen (Properties > Trend > Pen n > Line color). The operator identifies enabled channels by color and selector state.
4. Drive the selector booleans from five toggle buttons. Configure each button to write its own TrendSel_n tag.

When a channel is disabled, the pen continues to draw — but at value 0, so the line drops to the bottom of the chart. To avoid visual confusion, animate the Pen color property of the trend so the disabled pens are rendered in light gray.

6. Configuring Dynamic Y-Axis Scale via Tags

Open the Trend View properties and expand Left value axis (or Right value axis). Each axis exposes four properties:

To allow the operator to change scale, assign the HMI tags Trend_LeftY_Start and Trend_LeftY_End to the Begin value, tag and End value, tag properties respectively. Two numeric I/O fields on the screen write into these tags. As soon as the tag value changes, the trend redraws within the new range.

7. Configuring X-Axis (Time Axis) Scale via Tags

The X axis on a Cyclic real time trend is dynamic: its start and end are tags of type DATE_AND_TIME (8 bytes, BCD-encoded). On a Data log trend, the X axis is bound to the log's own timestamp; tag-driven scaling is not supported on this trend type.

For cyclic real-time trends, open Properties > Time axis > Begin/End, tag and assign the DATE_AND_TIME tags Trend_TimeX_Start and Trend_TimeX_End. The minimum window on a KTP400 is 1 minute; the maximum is bounded by the trend's Number of values and acquisition rate. With 1000 values at 1 s, the maximum window is ~16 minutes.

8. Trend Type Constraints: Cyclic Real-Time vs Data Log

The choice of trend type drives the entire feature set available to the operator. The constraints below are observed in WinCC Advanced V13 SP1 Update 5 and confirmed against the official Siemens documentation.

Reference: Siemens TIA Portal V20 documentation: Configuring a trend view for a data log.

9. KTP400-Specific Performance Considerations

The KTP400 Basic has the lowest CPU budget in the Comfort/Basic line. Limits that matter for this configuration:

• Concurrent animations: Maximum 50 simultaneously animated properties per screen. Five visibility animations plus four axis-tag animations is well within budget.
• VBScript scheduled-task budget: Total scheduled-task CPU share is limited to 30%. The 500 ms script in Section 5.1 costs ~3% with five channels.
• Display refresh: The Trend View does not use double-buffering; at 1 s acquisition with five pens, faint flicker is normal. Set Appearance → Update to Cyclic in background if the operator reports ghost lines.
• Trend buffer: Maximum 1,000,000 values per trend across all pens. Plan acquisition period and trend duration accordingly.

10. Step-by-Step Implementation Guide (Combined Method)

This procedure produces a single screen with five operator-selectable trend pens, both Y axes tag-scaled, and a date-driven X axis. Estimated build time: 45 minutes.

10.1 Create the tag schema

1. In the project tree, expand HMI Tags. Add the 19 tags listed in Section 3.
2. For ProcessValue_1..5, set the Connection property to the PLC. For all others, set Connection to Internal tag.
3. For Trend_TimeX_Start/End, set the data type to Date and time.

10.2 Build the trend view

1. Insert a Trend View object. Size it to fill the upper 80% of the screen.
2. Open Properties > Trend > Trend type and select Cyclic real time.
3. Add five pens. Bind each to TrendValue_n. Assign distinct colors (e.g., red, green, blue, orange, magenta).
4. Set Properties > Trend > Trend → Index to Time axis.
5. Set Time axis → Acquisition cycle to 1000 ms.
6. Set Time axis → Begin, tag to Trend_TimeX_Start and End, tag to Trend_TimeX_End.
7. Set Left value axis → Begin, tag to Trend_LeftY_Start and End, tag to Trend_LeftY_End.

10.3 Build the selector panel

1. Place five toggle buttons in a vertical column to the right of the Trend View.
2. Each button's Tag property writes its TrendSel_n tag. Set Mode to Toggle.
3. Add a small color square next to each button. Animate the Background color with: (TrendSel_n ? PenColor_n : 0xC0C0C0).

10.4 Build the scale panel

1. Place two numeric I/O fields at the bottom of the screen.
2. Bind one to Trend_LeftY_Start, the other to Trend_LeftY_End. Set Field type to Input/output.
3. Add an Auto scale toggle bound to Trend_AutoScale.

10.5 Add the gating scheduled task

1. Open HMI device → Schedules. Add a new schedule with a 500 ms trigger.
2. Set the event to Updated. Paste the VBScript from Section 5.1.
3. Compile and download the project to the panel.

11. Verification and Commissioning Tests

Run the following tests after download. Record results in the FAT/SAT protocol.

12. Troubleshooting Matrix

13. Frequently Asked Questions