Translation Quality Assessment: How to Check a Translation Supplier Before You Hire
Translation quality assessment, for a manufacturer, means checking how a supplier controls quality before you sign, then measuring the result on your own documents. Start with ISO 17100 and the second linguist, ask questions that match what you are buying (machine translation, post-editing or human translation), and score a test with a simple error typology. DEMA Solutions answers each of these questions in writing.
Who answers for a translation once it reaches the customer?
This guide is for the people who live with a translation long after the invoice is paid: technical documentation managers and technical writers who own the manuals, procurement teams who must qualify and document every supplier, and quality or operations directors who answer for what reaches the customer. Most work at manufacturers of complex equipment, such as HVAC systems, lifting and handling equipment, packaging and process machinery or automation lines, where a manual, a safety label or a spare parts list is part of the product.
Perhaps a terminology error has reached a customer, a distributor says the German manual reads like a machine wrote it, or an audit asks how translation suppliers are qualified. In each case, someone has to judge quality on evidence rather than promises.
What translation quality means for technical documentation
Every supplier says it delivers quality, and very few define it. For technical documentation, quality is not an impression of fluent text; it is a set of properties you can check one by one.
Accuracy. The translation says what the source says, no more and no less. An instruction to close valve B before opening valve A must not reverse the order, soften it or lose the condition. Accuracy errors are the most serious because they change what the reader does.
Terminology. The same component, function or action carries the same name in every document and release, and it is the name your engineers, service team and customers use. A manual that disagrees with itself, or with the machine’s interface, creates hesitation exactly when the reader needs certainty.
Numbers, units and references. Torque values, pressures, temperatures, tolerances, part numbers and cross-references come through unchanged, with the right decimal separators and unit conventions for the market. These errors matter most and are the easiest to miss when reading for style.
Completeness. Table cells, callouts in illustrations, footnotes and text embedded in graphics are all translated, and nothing from an earlier version is left behind.
Readability for the intended user. A maintenance technician, a line operator and a facility manager need different writing. The translation should read as if it had been written for them, with the conventions they expect for instructions and warnings.
A usable file. The delivered document opens, prints and publishes correctly, with layout, fonts and graphics intact. Loose text that someone in your office must paste back into the layout is not a finished translation.
Translation quality assessment is the practice of checking these properties systematically: first in the supplier’s process, then in its output.
What ISO 17100 actually requires
ISO 17100 is the international standard for translation services and the most useful single filter when shortlisting suppliers. It does not certify a translation; it certifies a process, audited by an independent certification body, covering people, workflow and records.
On people, the standard lists the competences a translator must have (translation, linguistic and textual competence in both languages, research, cultural, technical and domain competence) and the ways to demonstrate them: a recognised degree in translation, a degree in another field plus professional translation experience, or a longer period of full-time professional experience. Revisers need the same competences plus experience in the domain they revise, and project managers need their own documented competence.
On process, the defining requirement is revision. Every translation must be revised by a second person, not the translator, who compares the target text with the source for accuracy, terminology, consistency and suitability for purpose. The translator checks their own work first. Further steps, such as a monolingual review by a domain specialist or final proofreading, can be agreed with the client. The standard also defines what happens before production (enquiry, quotation, agreement, preparation of reference material) and after delivery, including the handling of client feedback.
On records, an ISO 17100 certified translation supplier keeps project documentation and evidence of qualifications, so it can show procurement who translated and revised your project and how issues were closed. Ask for the certificate, the certification body, the scope and the renewal date. A certificate you cannot see is not a filter.
What ISO 17100 does not guarantee
Certification tells you the process exists and is audited. It does not tell you whether the linguists assigned to you know hydraulic systems, refrigeration circuits or safety PLCs; domain competence is required, but how well it matches your products is something to ask about. It does not tell you who owns your glossary and translation memory, or whether the same people will still work on your documents next year, which is what keeps terminology stable across releases.
It also does not cover machine translation. The standard places raw machine translation output plus post-editing outside its scope; post-editing has its own standard, ISO 18587. A certified supplier can therefore still deliver machine-translated, post-edited text on your project. That may be appropriate, but you need to know.
Machine translation, post-editing and human translation: different questions
The questions that reveal quality depend on what you are buying, and many quotes do not say. Establish which of three services each supplier is offering before comparing anything.
Machine translation only. The text goes through an engine and nobody checks it against the source. It can suit internal reading or large volumes of low-risk text, but for anything that reaches a customer it is a risk. Ask which content it is used for, whether it runs on your approved glossary and translation memory, how your data is kept confidential, and who decides that a text is suitable for raw output.
Machine translation post-editing. An engine produces a draft and a linguist edits it. Ask whether post-editing is light (correct meaning, understandable text) or full (terminology, style and consistency corrected to a level comparable with human translation), who the post-editor is, and whether a second linguist then revises the result. Our guide to when post-editing is good enough for technical documentation explains where the line usually falls, and the machine translation post-editing service page shows how the levels are defined in practice.
Human translation with revision. A qualified translator works from the source with your memory and glossary, and a second qualified linguist revises the result. Here the questions are about people: who are the translator and reviser, what do they know about your type of equipment, and will they stay on your account.
Two prices that look very different may simply be prices for two different services, so a quote that does not say which one you are getting is the first thing to clarify.
The second linguist: the question to ask first
In our conversations with buyers, the first question is almost always whether a second qualified linguist really checks every translation against the source. It is the right instinct: revision is where most errors are caught, and it is also the step most easily shortened under deadline pressure.
Ask how revision is documented. A credible answer names the role (a reviser who is not the translator), describes the work (a bilingual comparison against the source, not a read-through of the target text alone) and explains how you would know it happened, for example through project records. Ask whether it applies to every language and every job, including small urgent updates, and what happens to text reused from the translation memory. “Our team checks everything” is not the same as a named second linguist comparing the translation with the source, and the difference only shows when something goes wrong.
Translation quality assessment in practice: how to run a fair test translation
Questions show how a supplier says it works. A test shows how it works on your documents, provided the test is fair, representative and assessed the same way for every supplier.
Choose one to three pages of real content that contain what makes your documentation difficult: product-specific terms, numbers and units, a safety warning, a table, a cross-reference and some text that refers to the machine’s interface. A marketing paragraph tells you little about how a supplier will handle a maintenance procedure. Our guide to translating technical manuals at lower cost describes the traps manuals contain, and they make good test material.
Give every supplier the same text, the same reference material and the same instructions about the target reader, and ask each to state which service the sample represents, so you do not compare a revised human translation with a light post-edit. If layout matters, send the source file rather than a PDF extract and judge the returned file too.
The best assessor knows the product and reads the target language natively, such as an engineer at a subsidiary or a trusted distributor; a general reader notices awkward phrasing but misses the wrong term for a component. Anonymise the samples if you test several suppliers, and remember that a short test shows competence, not consistency over the fortieth update.
Scoring the sample: a simple error typology
“The second one reads better” is hard to defend to procurement and impossible to repeat. A short error typology turns the assessment into something you can record, compare and reuse later for ongoing linguistic quality assurance. Industry error typologies and the ISO 5060 guidance on evaluating translation output follow the same logic, but a manufacturer rarely needs more than these categories:
- Accuracy: meaning changed, added or omitted; untranslated text.
- Terminology: a term that differs from the glossary, the interface or earlier documents.
- Language: grammar, spelling and punctuation.
- Style and readability: correct but unnatural, too literal or wrong for the reader.
- Locale conventions: decimal separators, dates, number formats and units.
- Numbers and references: changed values, part numbers, figure or chapter references.
- Layout and file: broken formatting, truncated text, a file that cannot be used.
Each error then gets a severity. A critical error could cause injury, damage, a regulatory problem or a recall: a wrong value in a safety procedure, a reversed instruction, a missing warning. A major error changes meaning, would confuse a competent reader or breaks a key term. A minor error is visible but does not change what the reader understands or does. In many companies a single critical error fails the sample regardless of the rest. Count errors per page or per thousand words so samples of different length compare fairly, keep the scored samples, and use the same yardstick for spot checks once the supplier is working for you.
Numbers, units and safety warnings
For equipment manufacturers, two parts of a document carry more risk than everything else combined: the numbers and the safety text. Quality directors are right to check them separately.
For numbers, ask whether automated checks compare every number, unit and tag in the translation with the source before human revision, how decimal and thousands separators are handled per market, and whether unit conversions are ever made (they should only be made on your explicit instruction). In your test, include decimals, ranges and units, and check them one by one.
For safety warnings, the questions are about consistency and register. Signal words, hazard descriptions and consequences should be translated the same way every time, ideally from approved phrases in your glossary or memory. A warning that varies from chapter to chapter loses authority, and one that is softened in translation becomes a product liability question. Our guide to user manual translation summarises what translated instructions have to achieve under EU product legislation.
Reused translations: the memory is not automatically right
Translation memory makes technical translation cheaper and more consistent, but it introduces a risk no test reveals: old text reused without anyone reading it again. Exact matches are often not revised, on the assumption that they were approved once. That fails when the memory holds text never properly reviewed, segments aligned from old documents or outdated terminology, and a memory built over years with several suppliers usually holds all three.
Ask whether reused content is reviewed in sensitive material such as safety warnings and regulated documents, whether aligned segments are flagged until a linguist confirms them, and whether a wrong match noticed by a translator is corrected in the memory and reported. Ask also who owns the memory and in which format you receive it; our article on who owns your translation memory explains why the answer should be you, at any time, without cost.
In-country and subsidiary review without bottlenecks
Many manufacturers, and almost every Italian subsidiary of an international group, have colleagues abroad who re-check translations before release. Their knowledge is valuable; their availability is not, and review by a busy sales engineer in another country is a common reason for missed release dates.
The way to keep review useful is to move most of it upstream. Approve terminology once in a shared glossary instead of correcting the same terms in every document; our article on keeping technical terminology consistent across translators and suppliers explains how. Agree what reviewers check (terminology and technical meaning, not personal style), give them a fixed time window and decide what happens if they do not respond.
Ask suppliers how they handle reviewer changes: genuine corrections should go back into the memory and glossary, and preferential edits should be discussed rather than applied blindly, so the same comment does not return on the next release. When several suppliers serve different subsidiaries, the same principles apply across them, as our article on how enterprise organisations manage translation across multiple vendors and markets describes.
Feedback, claims and quality over time
No supplier is error-free, so the real question is what happens after an error is found. A documented claims procedure is a fair requirement: the issue is logged, its cause analysed with the linguists involved, the translation corrected, and the memory and glossary updated so it does not recur. Ask for an anonymised example of a past complaint. A supplier that answers “it won’t happen” has no process.
Quality also has to be judged across revisions, because each release brings its own risks: a new translator, a changed term, a rushed update before a trade fair. Spot-check each release with the same error typology you used for the test, track the results and review trends with the supplier at regular intervals. A stable or falling error rate across releases says more than any single outstanding sample. For selection criteria beyond quality, such as capacity, formats and pricing, our guide on how to choose a technical translation company covers the rest.
The questions to ask a translation supplier
Ask these in writing and compare the answers side by side; the way a supplier answers is itself informative.
- Which service is this quote for? Machine translation, post-editing (light or full) or human translation with revision, per document type.
- Who translates and who revises? Native speakers who know your type of equipment, and a second qualified linguist comparing every translation with the source.
- Can we see your ISO 17100 certificate? Certification body, scope and renewal date.
- How are numbers, units, tags and terminology checked? Automated checks before human revision, not only a final read.
- Who owns the glossary and translation memory? You should, with export at any time.
- How is reused text treated in sensitive content? Reviewed again, and corrected at source when wrong.
- How do you work with our in-country reviewers? A defined loop that feeds approved changes back into memory and glossary.
- What happens when something is wrong? A documented claims procedure, with an example.
- Will the same linguists stay on our products? Continuity keeps terminology and style stable.
- Can you return files in their original layout? For manuals and catalogues, multilingual desktop publishing should be part of the service.
You should not take any supplier at its word, including us. What separates suppliers is whether they can show, in writing and before you sign, how each part of quality is controlled, and whether a test on your own content confirms it.
How DEMA Solutions answers these questions
Here are our own answers. The translation process is certified to ISO 17100 by CSI under certificate TRD21015 and audited every year. Each text is translated by a native speaker with experience in the subject and then revised against the source by a second qualified linguist. Before delivery, numbers, units, tags, glossary terms and consistency are verified, and the glossaries and style guides prepared for your content apply in every language and every update.
Translations reused from the memory are not treated as automatically right: in sensitive projects they are checked again. Your glossary and translation memory belong to you and are exported in TMX and TBX whenever you ask, and manuals and catalogues come back from our in-house DTP team in their original layout. With more than 20 years in technical documentation, we answer every question in this guide in writing. Our quality page describes the full process, and the page on our technical translation services shows how it applies to manuals, catalogues and interface texts.
Where TUBE fits
Alongside project-based translation, TUBE serves manufacturers who update documentation continuously and want the wording of each update under their own control. Your glossary and translation memory guide machine translation in an AI-managed process, and DEMA sets them up for you or builds a memory from your past translations, with nothing to install or program. Every approved translation is stored in a memory you own and can export.
Frequently asked questions
It is the evaluation of a translation, or of a supplier's process, against defined criteria such as accuracy, terminology, numbers and units, completeness, readability and file usability. For buyers, it combines checking a supplier's process before hiring with scoring results on real content.
ISO 17100 is the international standard for translation services. It sets competence and qualification requirements for translators, revisers and project managers, requires every translation to be revised by a second person against the source, and defines the process and records from enquiry to feedback.
It is a strong first filter, not a complete answer. It does not show whether the linguists know your products, how your terminology and memory are managed, or whether results stay consistent over time. Combine it with written questions and a test on your own content.
No. Raw machine translation output plus post-editing is outside its scope and covered by a separate standard, ISO 18587. If machine translation is used on your project, ask which level of post-editing applies and whether a second linguist revises the result.
Typically one to three pages, long enough to include specific terminology, numbers and units, a safety warning, a table and cross-references. Give every supplier the same text and reference material, and have the samples assessed blind by someone who knows the product.
Classify each error by category (accuracy, terminology, language, style, locale conventions, numbers, layout) and severity (critical, major, minor), weight critical errors heavily and count errors per page or per thousand words, so results can be compared and tracked over time.
In sensitive content, yes. Memories can contain unreviewed, aligned or outdated text, so safety warnings, regulated documents and any segment a linguist flags deserve a second look, with corrections fed back into the memory.
Check before you choose
If you are choosing a translation supplier, or reviewing the one you have, ask us the same questions. Tell us what you translate and we will answer them in writing, and translate a sample of your own content so you can judge the result.
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