ISO 17025 Traceability: Challenges with Proprietary Calibration Systems

By SIMCO | April 28, 2026

In calibration and testing, traceability is a core requirement of ISO/IEC 17025. Measurement results are expected to be linked to the International System of Units (SI) whenever technically possible through an unbroken calibration chain, with uncertainty defined at each step.

But this becomes more complicated when equipment manufacturers restrict access to calibration processes. Proprietary software, locked adjustments, and limited documentation can make it difficult to fully evaluate and demonstrate traceability and measurement uncertainty.

This raises an important question for laboratories and quality teams: can proprietary systems meet ISO 17025 traceability requirements, and how should the associated risks be managed?

The Requirement: Traceability and Uncertainty

ISO/IEC 17025:2017, Clause 6.5 requires:

  • Traceability to SI units whenever technically possible
  • An unbroken chain of calibrations
  • Documented measurement uncertainty at each step

A practical explanation of what this chain must include is covered in ISO/IEC 17025 Calibration Audit Guide: Requirements and Common Pitfalls

This is reinforced by ILAC P10, which explains how traceability must be established and supported. ILAC P10 also reinforces that traceability includes a stated measurement uncertainty, not just a reference to a standard.

Traceability is not just documentation. It directly affects risk. If uncertainty is unknown or incomplete, you cannot confidently determine if a result meets specification.

This connection between traceability and risk is discussed further in From Sticker to Strategy: Using Calibration Certificates to Protect Quality and Safety

The Reality: Proprietary Calibration Systems

Some OEMs design systems where:

  • Adjustments can only be made using proprietary tools
  • Verification steps are embedded in closed software
  • Calibration constants are hidden or inaccessible
  • Uncertainty data is not provided or is incomplete

From a laboratory perspective, this creates a gap. You may be able to operate the instrument, but you cannot fully demonstrate traceability in the way ISO 17025 expects.

Does ISO 17025 Allow Exceptions?

Yes, but only in limited cases.

Clause 6.5.3 allows other approaches when SI traceability is not technically possible. Examples include:

  • Certified reference materials
  • Consensus standards or agreed methods
  • Inter laboratory comparisons

However, this is not a broad exception. The key condition is technical feasibility. If SI traceability is possible but restricted by a manufacturer’s design or business model, this does not meet the intent of the exception in Clause 6.5.3.

A proprietary lock does not automatically justify an exception.

What Accreditation Bodies Expect

Accreditation bodies such as A2LA, ANAB, and UKAS generally expect:

  • A clear justification if SI traceability cannot be achieved
  • Evidence that alternative methods are technically valid
  • A defined uncertainty budget, even if it uses some manufacturer data
  • Transparency about limitations on the calibration certificate

If a lab accepts OEM results without evaluating traceability or uncertainty, that can lead to findings during assessment.

Similar risks are seen when calibration shortcuts are taken, which can increase uncertainty and weaken traceability, as discussed in Calibration Requirements for Defense Contractors: Risks of Shortcuts and How to Stay Compliant

Common Misconception

Myth:
“If the OEM controls the calibration, it must be compliant.”

Reality:
OEM control does not guarantee compliance with ISO/IEC 17025. The responsibility for traceability still sits with the laboratory or the user of the data.

Practical Options for Customers

When dealing with proprietary systems, there is no single solution. The right path depends on risk, application, and available information.

1. Request Full Documentation from the OEM
Ask for:

  • Calibration methods
  • Measurement uncertainty
  • Traceability chain

Some OEMs will share this under agreement. Others may not.

2. Use the OEM as an External Provider
ISO/IEC 17025 Clause 6.6 requires evaluation of external providers. This includes:

  • Assessing the OEM’s competence
  • Reviewing their calibration certificates
  • Confirming traceability and uncertainty statements

If this information is incomplete, the risk must be documented and managed.

3. Use an Accredited Lab for Verification, OEM for Adjustment
This is often a practical hybrid approach.

  • An ISO/IEC 17025 accredited lab performs independent verification and reports measurement results with stated uncertainty and traceability
  • The OEM performs adjustments or repairs when required using their proprietary tools

Why this works:

  • The accredited lab provides objective evidence of performance and traceability
  • The OEM maintains control over adjustments that cannot be accessed otherwise
  • The user retains visibility into measurement uncertainty and risk

For a deeper look at accredited vs. non-accredited calibration, see Accredited Calibration vs. Quality Calibration. What’s the Difference?

Important considerations:

  • The verification scope must be technically sound and cover critical parameters
  • Any limitations must be clearly documented
  • The relationship between “as found,” “adjusted,” and “as left” conditions should be understood

This approach does not eliminate all gaps, but it provides objective evidence of performance that can support audit defensibility when full traceability through the OEM is not transparent.

4. Apply a Fit-for-Purpose Approach
If full traceability cannot be achieved:

  • Define how the instrument is used
  • Evaluate the impact of missing uncertainty elements
  • Document known limitations

This supports risk-based decision making, which is a core part of ISO 17025.

5. Use Independent Checks
Where possible:

  • Perform check measurements against known standards
  • Use interlaboratory comparisons
  • Trend data over time

These actions provide supporting evidence, but they do not replace full traceability.

6. Consider Equipment Selection Risk
Long-term, procurement decisions matter.
Selecting equipment with open calibration methods can:

  • Reduce compliance risk
  • Improve transparency
  • Lower lifecycle cost

Why This Matters

Traceability supports:

  • Reliable pass or fail decisions
  • Regulatory acceptance
  • Defensible measurement results
  • Customer confidence

This is one reason ISO/IEC 17025 accreditation is often considered the benchmark for defensible measurement results. Learn more in Why ISO 17025 Accreditation Matters: The Benefits Behind the Gold Standard

When uncertainty is unclear, every decision based on that data carries hidden risk.

Key Takeaway

ISO/IEC 17025 allows flexibility, but not convenience-based exceptions. Proprietary systems do not remove the requirement for traceability and uncertainty. They shift the responsibility to the user to evaluate, justify, and manage the risk.

Using a combination of accredited verification and OEM adjustment can be a practical and defensible path, but it still requires careful documentation and technical judgment.

Need Help Navigating Traceability in Proprietary Systems?

Proprietary calibration systems can introduce gaps in traceability, uncertainty evaluation, and audit defensibility. Knowing how to evaluate and manage those gaps is critical to reducing risk and maintaining confidence in your measurements.

SIMCO works with organizations to assess calibration processes, verify traceability, and build defensible approaches that align with ISO/IEC 17025 requirements.

  • Evaluate traceability and uncertainty in OEM-controlled systems
  • Strengthen your calibration program with independent verification
  • Identify and document risks before they impact compliance

Contact us to talk to a calibration expert to review your current approach and identify opportunities to improve measurement confidence.

 

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