How to Flag Stale Values in PI Vision

Before you begin

Use Value+, part of Vision Library+, on a display you can edit. You need a source you can read, a known expected event interval, and a test display for checking the warning. Confirm your installed version exposes Data Quality and Stale warning.

This check applies to live current values. Historical display time, custom-time or offset Value+ reads, and summary values are excluded. A value that stays constant while receiving new timestamps is a different problem: an age check cannot detect that frozen measurement.

1. Convert an existing Value symbol or add Value+

The stale-warning setting described here belongs to Value+. If your display uses the regular Value symbol, convert it before looking for the setting.

Convert an existing Value symbol

Open the display in editing mode. Right-click the regular Value symbol and select Convert Symbol to → Value+. Then check the source label and displayed reading before configuring the warning.

Add a new Value+ symbol

If you are starting with a new symbol, select Value+ in the PI Vision symbol gallery and drag the intended PI Point or Asset Framework (AF) attribute onto the test display. If the display already uses Value+, continue with its configuration.

Right-click the symbol and select Configure. Under Data retrieval, use display end time with the display following current time, and no custom time or offset. The Value+ guide describes the available retrieval and timestamp options.

Check the source label and displayed reading before adding the warning. A correctly configured age check on the wrong source still gives the wrong operational context.

2. Choose the acceptable data age

Choose a Stale after threshold longer than the expected interval between source events. Include normal delays and the effect of scan frequency, PI exception and compression settings, or a scheduled analysis that produces the value.

The example below uses a two-hour threshold. Choose a duration that fits your source and the operational decision; two hours is not a recommended setting for every measurement.

Use the age of the source event, not the time since the browser last refreshed, to make this decision. A display can refresh successfully while still showing the same old event.

3. Enable the stale warning

In the symbol's Data Quality configuration, turn Stale warning on. In the configuration shown below, Stale after (Hours) is set to 2. Enter the threshold appropriate for your source, then save the display.

Check whether the pane indicates a global override. When an administrator enforces site-wide Data Quality settings, those values apply to supported symbols with no per-symbol opt-out. Changing a saved local threshold does not override that policy. Agree the effective threshold with the administrator if it does not suit this source.

The saved local settings are retained underneath the override. If the administrator later disables it, the symbol resumes those local settings.

4. Read the warning on an old test event

Use a non-production source whose latest event is known to be older than the effective threshold, while keeping the display at current time. Do not move the display into history to simulate an old live value: historical reads are excluded from stale checking.

Value+ keeps the reading visible and adds an amber clock. Hover over the warning to inspect the last event time, current data age, and threshold in the normal Value+ tooltip. These details explain why the reading is flagged.

Compare with a recent event on the same test source when one becomes available. Once the current event's age is within the threshold, the stale condition should no longer apply. Verify both states before using the configuration on an operational display.

If the result is unexpected

• An old reading has no warning: confirm Stale warning is enabled, check the effective threshold, and verify that the symbol is displaying a live current value rather than an excluded historical, custom-time, offset, or summary read.
• A steady value never becomes stale: inspect its event timestamp. New events containing the same value keep the event age recent; investigate a suspected frozen sensor separately.
• The warning appears during normal operation: compare the threshold with actual event intervals and expected delays. Adjust it only after deciding what data age is acceptable.
• Local settings appear to have no effect: check the global override indication and ask the administrator which values are enforced.

Using the warning on other symbols

Linear Gauge+ and Radial Gauge+ also support stale warnings. Their warning appears when any displayed pointer is stale, and the tooltip identifies the affected sources. Check the expected event interval for each pointer when choosing a threshold.

Alarm Sound+ has different consequences: while stale, it shows an amber stale state, does not evaluate the old value as Default or Alarm, and plays no alarm audio. Review that behavior before enabling it in an audible workflow. Combo Chart+ does not support this stale-warning option.

The warning makes the event's age visible; it does not repair the source. If it reveals an unexpected delay, continue with the source investigation described in the PI System data-quality guide.

For supported symbols, exclusions, and global settings, refer to the Data Quality documentation.