Fix an HMI pop-up numeric field that will not update until reopened

Why does the pop-up show the old number until you close and reopen it?

Because the new value reached the tag and the open window stopped redrawing the field; the reopen draws the field from the current tag value, which is why the correct number appears the instant the window comes back.

A numeric entry on a pop-up carries two jobs. It writes the number you touch into the controller tag, and it keeps the number on the screen matched to that tag. The documentation for numeric entry objects states the first job plainly: the object exists to enter or change a tag's value from the panel screen, and it refuses entries outside the limits you configured for it. A pop-up holding a stale number has lost one of those two jobs, and the reopen tells you which one. A window that shows the new value after reopening had the write all along; what died is the live redraw while the window stays open.

Is the write failing, or is only the display stale?

Watch the tag in the controller's online monitor: a link that is polling normally shows your entry there in under 1 second, so a monitor that moves while the pop-up stands still clears the write and names the display as the failed half.

The screen looks identical either way, so run your observations through this table:

Fields that also go stale on base screens after you navigate fit a different fault, covered under numeric displays showing old values after a screen change. On other platforms the same signature, a healthy tag behind a dead field, is read as stale values that point to a local redraw fault.

What do you check first on the running machine?

Open the controller's online tag monitor beside the panel, make one entry inside the field's configured limits with the pop-up open, and watch both numbers for 5 seconds before you touch the project.

One safety line first: run this with the machine in a safe state and a value the process tolerates, and if operators read that pop-up before an action with risk in it, the stale number is the hazard and the redraw gets fixed before the screen returns to service.

1. Pick a test value inside the field's configured limits. If the process needs a harder bound than the field enforces, clamp the entry limits in ladder logic.
2. Record the number on the open pop-up and the number in the online monitor for that tag.
3. Enter the test value and watch the monitor for 5 seconds. Record both numbers.
4. Close and reopen the pop-up once. Record what the field shows.
5. Force the tag from the controller side with the pop-up open, watch 5 seconds, then reopen once more and record.

Five observations, about 15 minutes, and the table above turns them into a diagnosis.

What does a worked example with a set-point look like?

An oven set-point, on a tag this page calls Oven_SP, reads 175.0 °C on the open pop-up; the operator enters 185.0 °C, the monitor shows 185.0 °C inside 1 second, and the pop-up still reads 175.0 °C after 5 seconds.

Work the numbers:

• Requested change: 185.0 °C − 175.0 °C = 10.0 °C. The field sits 10.0 °C behind a tag that already moved.
• Close and reopen: the field shows 185.0 °C. The write path passed in the panel-to-controller direction.
• Force Oven_SP to 190.0 °C from the controller with the pop-up open: after 5 seconds the field still shows 185.0 °C, so it is 190.0 °C − 185.0 °C = 5.0 °C behind. Reopen once and it shows 190.0 °C. The write path passed in the controller direction too, and the redraw failed in both directions while the window stayed open.
• The same tag on the base screen moved both times within 1 second.

Decision for this example: the link is good, the write path is good in both directions, and the fault lives in that one open window on the panel. Reopen procedure today, minimal project to the vendor this week.

Why does the simulator update when the panel does not?

The simulator renders the project with your PC's resources while the panel runs its own runtime from its own deployed copy, so once the same project is on both, the difference belongs to the panel.

Make the comparison honest before you act on it:

1. Confirm the project on the panel is the one you are simulating: compare the project version and the download date.
2. Use the same tag and the same starting value in both tests.
3. Make one entry in the simulator and one on the panel, watching the online monitor both times.

If both environments leave the tag unchanged, the fault is in the project configuration, and the redraw is the innocent half. If the tag moves in both and only the panel's pop-up stands still, the fault is in the panel runtime or in what was deployed to it, and that package goes to the vendor. Record the panel's firmware version with the report; reading the panel's firmware version for field maintenance is its own five-minute job.

What keeps operators working today?

Close and reopen the pop-up after each entry, and fold the reopen into the entry itself: an accept button that closes the window gives the operator one touch and a freshly drawn field.

Write the procedure as four steps: enter, close, reopen, read. It suits set-point entries, recipe numbers and counters, where the operator asks for a change and the window's job is done once it closes. Check the displayed number against the monitor once per shift until the redraw is fixed. If the project runs reset logic when the pop-up closes, every reopen fires that logic, so confirm the cycle does what you intend before it becomes procedure.

How do you get the redraw fixed for good?

Cut a copy of the project to one pop-up, one numeric entry field and the one tag, reproduce the stale field on the panel with that project, and send that project to the vendor's support with the panel's firmware version.

1. Save a copy and leave the production project alone.
2. Strip it to one pop-up, one field, one tag, built the way your real window is built; if the real one uses a screen window, keep a screen window, as covered in building an HMI pop-up screen with a screen window.
3. Run the two-direction test on the panel, then once in the simulator, and write down all five observations.
4. If the vendor lists newer firmware for the panel, test the minimal project on it before anything else changes; updating the panel firmware from a USB stick is the usual route.
5. Change documented settings one at a time and retest on the panel after each. Leave undocumented refresh parameters alone.
6. Pass this acceptance test before you close the job: with the pop-up open, a panel entry and a controller-originated change each show on the field within 1 second, with no reopen, and still do after you navigate away and come back.

Recommendation: Diagnose with the tag monitor before you change anything: one safe entry, 5 seconds of watching, one reopen. If the tag moves and the field stands still, put the close-and-reopen procedure into the operator's steps today and spend an evening on the one-field project for the vendor. If the tag stands still too, stop calling it a display fault and work the field's tag, data type, scaling and limits, because the redraw had nothing to do with it.

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