View Accreditation & Traceability

FIG. 01 · Reference standards and calibration records

In this guide

1. Accreditation

   What it confirms about laboratory competence and assessed scope.

2. Traceability

   How measurement results connect through an unbroken chain.

3. Scope

   Why accreditation applies only to specific capabilities.

4. Measurement uncertainty

   Why every result carries an uncertainty contribution.

5. Certificate evidence

   What buyers and auditors should verify.

What ISO/IEC 17025 covers

ISO/IEC 17025 is the international standard for the competence of testing and calibration laboratories. It describes what a laboratory must have in place for its results to be technically valid — not only a working quality system, but demonstrable technical competence for each kind of measurement it performs.

An accreditation body assesses a laboratory against the standard and, where it is satisfied, grants accreditation for a defined scope. The assessment typically looks at:

Technical note

Standard edition

This guide refers to ISO/IEC 17025:2017, the current edition at the time of writing. Confirm the edition named on the accreditation certificate.

Accreditation vs certification

The two words are often used interchangeably, but they describe different things. Certification — for example against ISO 9001 — confirms that a management system conforms to a standard. Accreditation to ISO/IEC 17025 confirms technical competence to produce valid results for a specific scope.

Technical note

In practice

Some customers and quality systems ask for accredited calibration specifically. Check the wording of the requirement rather than assuming either is sufficient.

Traceability

Metrological traceability means a result can be related to a reference — ultimately the SI units — through a documented, unbroken chain of calibrations, each contributing to the measurement uncertainty.

1. L1 SI / national standard

2. L2 Reference standard

3. L3 Laboratory working standard

4. L4 Customer instrument

Each link is itself calibrated and has its own certificate. Uncertainty accumulates down the chain, which is why the customer instrument carries the largest uncertainty of all.

EvidenceSee the full traceability chain

Definition

Traceability

Property of a result whereby it can be related to a reference through a documented unbroken chain of calibrations.

Accredited scope

Accreditation is never granted to a laboratory as a whole. It applies to the capabilities listed in its scope, and only to those. A scope typically lists, for each capability:

• the parameter or quantity measured

• the range over which the method applies

• the calibration and measurement capability (CMC) — the smallest uncertainty achievable

• the method or procedure used

• where the work can be performed: in the laboratory, on-site, or both

Example scope extract Representative template data

EvidenceView the accredited scope

Definition

CMC

Calibration and measurement capability: the smallest uncertainty a laboratory can achieve for a measurement under normal conditions, as listed in its scope.

Technical note

Read the scope, not the logo

An accreditation mark on a website says nothing about a specific range. The scope does.

Measurement uncertainty

No measurement is exact. A calibration result is only complete when it is reported with its uncertainty — the interval within which the true value is expected to lie, at a stated level of confidence.

U = k × u c

• U — expanded uncertainty, as reported on the certificate

• k — coverage factor, usually 2 (approximately 95 % confidence)

• uc — combined standard uncertainty of all contributors

Typical contributors include the reference standard, repeatability of the readings, resolution of the instrument, environmental conditions and the method itself. Each is evaluated, combined by root sum of squares, then expanded.

Example · representative

A digital multimeter reads 10.0003 V against a 10 V reference with an expanded uncertainty of 63 µV (k = 2). The true value is expected to lie between 10.00024 V and 10.00036 V with approximately 95 % confidence.

Technical note

Conformity decisions

If a reading sits close to a tolerance limit, the uncertainty decides whether a pass is defensible. Agree a decision rule before calibration.

Calibration certificates

The certificate is the evidence. Whatever the laboratory, a calibration certificate should allow a reader to identify exactly what was calibrated, how, against what, and with what result.

1. Instrument — Unique identification of the unit

2. Method — The documented procedure used

3. Date — When the measurements were made

4. Results — Readings before and after adjustment, with uncertainty

5. Standards used — Reference equipment and its calibration status

6. Traceability — How the result links to national standards

7. Accreditation — Which results fall within accredited scope

8. Authorised — Who approved the certificate

EvidenceSee the full certificate anatomy

Definition

As-found / as-left

Readings before any adjustment (as-found) and after adjustment (as-left). As-found data is what tells you whether past work was affected.

Accredited vs traceable calibration

Both accredited and traceable calibration may link results to national standards, and both may use the same reference equipment and methods. The difference is scope: only calibration performed within the accredited scope can be presented as accredited, and only that may carry the accreditation mark.

Traceable calibration is often entirely appropriate — for ranges outside the scope, or where a requirement asks for traceability rather than accreditation. What matters is that the certificate states which it is.

EvidenceCompare accredited and traceable in full

What quality teams should check

Before accepting a certificate into your records, a short review catches most problems.

• [ ] Is the instrument correctly identified — make, model, serial or asset number?

• [ ] Is the required parameter covered?

• [ ] Is the calibrated range appropriate for how the instrument is used?

• [ ] Is the accreditation status clear for each result?

• [ ] Is uncertainty stated where needed, with its coverage factor?

• [ ] Is the traceability statement clear?

• [ ] Are as-found and as-left data included, if your procedure requires them?

• [ ] Is the certificate authorised and dated?

0 of 8 checked · not savedDL-03Certificate review checklist

Technical note

Keep it

Download the certificate review checklist (DL-03) to run this review the same way every time.

How accreditation, scope, traceability and the certificate fit together

1. Accreditation

   assesses competence

   Body assesses the laboratory

2. Scope

   defines capability boundaries

   Parameters · ranges · CMC

3. Traceability

   connects the measurement result

   Unbroken chain to SI

4. Certificate

   records the evidence

   Result · uncertainty · status

carried on every accredited result

FIG. 02 — Accreditation sets the boundary; the scope defines it; traceability and the certificate carry it into each result.

Terms used in this guide.

Plain-language definitions for reference while reading.

What this means when you send an instrument for calibration.

Four common situations, what to decide in each, and where to go next.

1. The instrument and range are within accredited scope.

   You can receive an accredited certificate. Confirm the range in the capability directory before sending.

   Check capability

2. The instrument is supported but the exact range falls outside scope.

   Traceable calibration may still be available. Decide whether your requirement accepts traceable results.

   Compare accredited and traceable

3. You need traceable calibration; accreditation is not required.

   A traceable certificate with stated uncertainty is usually sufficient. Say so in the request.

   Request calibration

4. You need audit evidence for a regulated or customer-controlled process.

   Check the exact wording of the requirement and keep certificates, scope revision and out-of-tolerance records together.

   Audit preparation checklist

From this guide to the evidence behind it.

Each step opens the METRILAB page that holds the detail.

1. 01 · Guide Understanding ISO/IEC 17025

2. 02 · Accreditation View scope, traceability and certificate evidence

3. 03 · Capability Confirm instrument, parameter and range

4. 04 · Service Select the relevant calibration discipline