Test HMI localization text paths before you buy

Which HMI text paths can fail after the labels translate fine?

Four text paths reach the operator on a small HMI: object labels and captions, alarm messages, lookup text lists, and the prompts a numeric-entry object throws when a value is out of range, and the font that worked on the first path does not always reach the other three.

Group them by who writes the string, because the two groups fail in different places:

Text you author

• Screen labels and captions. This is the path the sales sheet means, and the one that almost always works.
• Alarm messages you type into the alarm setup. The settings live in the alarm configuration, and our article on operator text in HMI alarms walks the event messages.
• Lookup text entries. The list an operator scrolls to pick a value is a separate object type, so it gets its own test.

Text the panel supplies

• Numeric-entry prompts. The out-of-range message belongs to the object, and on the panel in our example there is no field to edit it.

Whether your panel shares these gaps is what the bench test answers. The sales sheet will not.

How many alarms can the panel's handler hold?

Check the alarm handler limit in the panel's project tool before you price the machine, because compact panels cap it at fixed numbers, 16 entries on the light-duty panel in our example, and a project that needs 14 alarms with growth coming will not fit.

The limit lives in the alarm configuration for the exact panel model, so read it there. Count what the machine needs: distinct conditions the operator has to tell apart to respond correctly. Then compare:

• Below the limit: proceed to the text checks.
• At or near the limit: run the release test on the complete alarm set, so the acceptance you checked is the one you ship.
• Over the limit: group alarms only when the operator can still identify the condition and its response from what the alarm shows, or move to a panel with a bigger handler.

Our article on when a 16-entry handler fits your project carries that arithmetic for a compact panel.

Worked example: does a Russian alarm list fit a 16-entry handler?

A conveyor line needs 14 distinct alarms in Russian on a compact panel whose handler takes 16 entries and whose alarm text field holds 40 characters: the count fits with 2 spare entries, but the longest message, 33 characters in English, needs about 45 in Russian and truncates.

The count. The project needs 14 alarms, the handler takes 16, so the fit is 16 − 14 = 2 spare entries. If commissioning adds 3 more conditions, the total is 14 + 3 = 17 and the panel no longer fits. At 14 with no planned growth, the count passes.

The text length. The longest English message, "Conveyor 4 motor thermal overload", runs to 33 characters. Russian lands at the high end of a rule of thumb from translation practice, 35% longer for European target languages: 33 × 1.35 = 44.55, about 45 characters. The 40-character field in this example is an illustrative number; read the real one from your tool's alarm text box. The Russian string loses 45 − 40 = 5 characters and cuts off mid-message. Shorten the authored text to "CV4 thermal overload", 20 characters: 20 × 1.35 = 27, which fits 13 characters under the field.

The decision. The panel passes on count with 2 spare entries and passes on text once the long messages are rewritten short. Sign the panel only after the same length check runs on every message you author, because the long messages carry the truncation risk.

Does any standard require HMI text in the operator's language?

EU machinery law does: the Machinery Directive requires the instructions and warnings shown on a machine to be in an official EU language understood in the member state where the machine runs, while IEC 61131-3, which defines the PLC programming languages, says nothing about the operator's language.

The directive's requirement covers the warnings and operating instructions on the machine, and buyers repeat it in the specification for every string the operator reads. IEC 61131-3 is the standard behind the project languages, Ladder Diagram, Function Block Diagram, Structured Text and Instruction List, and it leaves operator-language requirements to the machinery rules and the purchase specification. Localization therefore lives in each vendor's text tools, which is why the check is per panel and per project.

One safety note: an alarm the operator cannot read is a hazard, so language sign-off belongs with the process owner, not only the translator.

How do you run the panel test in 30 minutes?

Build a one-screen test project in the panel's own project tool, load about 20 representative strings across the four paths, run it on the physical panel, and you can finish in about 30 minutes per language.

1. Inventory every string the operator can see: normal run screens, alarm screens, lookup lists and numeric entry. Mark each one as authored or panel-supplied.
2. Open the project tool for the panel model you are pricing and read two numbers: the alarm handler limit and the alarm text field length.
3. Type the target-language strings for the authored text. Start from the longest English strings and add the expansion margin, 35% for the languages that expand most.
4. Run the project on the physical panel. Trigger one alarm, open one lookup list, and enter a value out of range on a numeric-entry object.
5. Check each path for four things: target language, no truncation, no substituted glyphs such as boxes or question marks, and a size the operator reads at the working distance. The editor preview misses this; the editor and the panel disagree about text size even in English, as our article on the editor and panel text size mismatch shows.
6. Have a fluent reader confirm meaning, and archive the tested project file with the result.

Pass means all four paths show complete, legible text in the target language. Any English an operator meets in run, alarm handling or entry is a fail for an international machine.

If the panel supports runtime language switching, test that too; our article on switching an HMI between English and Spanish at runtime shows the workflow. Loading the translations is a job of its own, and the export and import steps in translating an HMI project to French without retyping every object apply to any target language.

What do you do when a text path fails?

Treat each failure by its path: untranslatable entry prompts need a workflow that never reaches the prompt, an alarm or lookup font gap is a platform capability no label edit reaches, and an alarm count over the handler limit means grouping or a different panel.

• Entry prompts fixed in English. Redesign the entry so operators never reach the canned prompt: catch the out-of-range value with your own validation and your own authored message before the object raises its fixed text. Prove the redesigned entry still keeps the validation the process needs, in the test project, before release.
• Alarm or lookup text refuses the font. Changing label fonts, translating captions or editing lookup values leaves these paths untouched. Choose a panel whose alarm path passes the same test, or get written acceptance of the remaining English from the process and language owners, document which screens stay English, and do not present the machine as localized.
• Alarm count over the limit. Group only with the process owner's approval and only when the grouped alarm still identifies the condition and the response. Otherwise the handler decides the panel, not the price.

Recommendation: Run the four-path bench test in the panel's own project tool before you sign the machine order, and buy the panel only when labels, alarm messages, lookup text and entry prompts all show the operator's language on the physical panel and the alarm count fits the handler limit with at least one spare entry.

What do you send with the quote?

Send the string list with language and character set, the alarm list with its count, the panel model with its project tool version, and photos of the screens where each text path lives, and the answer comes back as a test plan instead of guesses.

• Language: every language that ships, with the character set named, Cyrillic or Greek for example.
• Text: the string inventory with a count per path, the longest strings, and the alarm list with its count against the handler limit.
• Hardware: the panel model and project tool version, the handler limit and alarm text field length as that tool prints them, and the panel's resolution, for example 800 x 480 pixels.
• Acceptance: who signs off the language, the fluent reader who checked meaning, and the country list that sets the requirement.

If the machine also needs a separate notice or status board beside the HMI, that is a different screen: see our shop-floor signage. It plays the files you load onto it, it is not the HMI, and its ports, software and lead time are confirmed with the quote.

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