Adding Value through Accredited Testing to ISO/IEC Guide 25

With barriers to international trade decreasing and more products being designed for the global marketplace, it is increasingly important for manufacturers of electrical and electronic devices to demonstrate compliance with the appropriate EMC standards. To simplify global trade, national accreditation bodies in more than 20 countries now have mutual recognition agreements (MRAs) that facilitate mutual recognition of test reports. Most countries accept testing at a laboratory accredited to ISO/IEC Guide 25¹ by organizations such as NVLAP, A2LA, UKAS, or the National Association of Testing Authorities (NATA) as proof of compliance. Manufacturers can also use a test report bearing the endorsement of a recognized accreditation agency as the basis of a due diligence defense in a dispute with a regulatory agency.

The most direct route to EMC compliance is generally by ensuring that a product meets appropriate EMC standards and then by making a Declaration of Conformity (DoC). In most cases, a technical construction file that contains the proof of compliance (usually including a test report) must be available to the relevant authorities. This article will explain the advantages of using accredited testing and give guidance for selecting the most appropriate test house. The terms accredited testing and MRA laboratories will be used to refer to laboratories that have ISO/IEC Guide 25 accreditation from an organization such as NATA, NVLAP, A2LA, UKAS, or similar organizations that have MRAs in place.

In Australia, NATA has an MRA with the Testing Multilateral Agreement Group of the European Cooperation for Accreditation of Laboratories (EAL). MRAs are also in place with NIST/NVLAP and A2LA. NATA's network of MRAs covers 34 laboratory accreditation bodies in 23 economies. This includes the countries and national accreditation bodies shown in Table I. Reports endorsed by any of the international bodies listed are considered equivalent to NATA reports.

In the event that a product's compliance is called into question, most regulators will conduct an audit of the relevant compliance file and, if not satisfied, may request further evidence to support the claims of compliance. The test report is the key element of the compliance documentation, and it provides the evidence for any claims of compliance. In the United States, a NVLAP or A2LA accredited test report to FCC rules is accepted by the FCC as proof of compliance with FCC Part 15 Rules for Personal Computers. In Australia, the Australian Communication Authority (ACA) will accept a NATA or MRA partner accredited test report as final in any determination. In Europe, reports bearing the endorsement of a nationally recognized accreditation agency such as DKD or UKAS are accepted by regulators as proof of compliance. Severe financial penalties may apply to individuals and companies that willfully violate EMC regulations. Regulators can insist upon product recall and ban products from the market. German and UK regulations have provisions for prison sentences.

ISO/IEC Guide 25 accredited test houses must be thoroughly evaluated by the accreditation agency. Accredited test houses must meet internationally recognized standards for good laboratory practice and calibration traceability of measurement equipment, have the necessary test facilities available, demonstrate an adequate level of technical competence, and operate with the appropriate quality management systems in place. ISO 9002 alone is not acceptable for accreditation of test laboratories because it does not include the key criteria of technical competence and adequate technical facilities prescribed by Guide 25 requirements. ISO/IEC Guide 25 usually requires accreditation of laboratories against each specific EMC standard, and a test report may not be endorsed unless the test house is accredited to the specific standard.

For example, a test house accredited by NVLAP to FCC Part 15 may not endorse a test report to CISPR 11. The NVLAP endorsement may only be applied to tests performed that are covered by the specific scope of the accreditation. ISO/IEC Guide 25 also requires that laboratories perform ongoing proficiency tests and interlaboratory comparison tests in their field of accreditation. Accredited laboratories are subject to rigorous technical and quality systems audit and periodic reassessment.

In Australia, testing by an ISO Guide 25 NATA-accredited laboratory is a safe way to prove compliance. An endorsed report is acceptable by the ACA and most of Australia's trading partners, including all European Union countries. Accredited testing will minimize risks should a dispute arise with a regulatory agency. Nonaccredited testing has its drawbacks because laboratories are not subjected to the rigorous surveillance that accreditation requires and there is often no guarantee of the reliability or accuracy of the results. The use of nonaccredited testing is generally less expensive, but in practice it may be rejected by the regulator. Consequently, the level of risk carried by the person who signs the DoC based on unaccredited testing is greater.

Test Time and Test Costs. The cost of testing is directly related to the duration of the test and the use of the test facilities. The number of applicable tests and the nature of the product will affect the total test time. Devices that are slow to respond or difficult to exercise require longer test times and are therefore subject to higher test charges. Charges also depend on the nature of the test, the technical competence of the test house, the sophistication of the facilities, and the organization's accreditation status.

Appropriate Standards Accreditations. A test house may use NATA or an equivalent MRA partner endorsement when it is accredited for testing to just one standard. Some accredited test houses have a limited scope of accreditation, often being accredited to one standard only. In addition, some consultants (nontest houses) are accredited as Competent Bodies and Conformity Assessment Bodies. The accreditation logo often appears in advertising literature giving the perception that the Competent Body or Conformity Assessment Body consultancy is accredited for testing. The use of the accreditation logo by a test house with limited accreditation may mislead people to think the test house has a wider scope of accreditation than it actually has.

When selecting a test house, the supplier must be satisfied that the laboratory is accredited to the appropriate standard and to all the applicable clauses of that standard. An accredited test report may only carry the endorsement of the accreditation agency if it is issued by a laboratory that is accredited to the specific EMC standard, including all the relevant clauses.

Are you an accredited test house? Some non–test house consultants are accredited Competent Bodies or Conformity Assessment Bodies and their role is to review documentation; they must not perform testing in support of a technical construction file (TCF) assessment unless they are specifically accredited by the appropriate agency for that testing. It is important that in any TCF assessment, the Competent Body prevents the occurrence of a conflict of interest. In Australia, testing by consultant Competent Bodies and Conformity Assessment Bodies is against NATA rules and the EMC framework.

What is the actual scope of the accreditation? Find out if you will receive an unconditional endorsed test report. It is important to ask whether the test house has specific accreditation for the appropriate test standards that your product must satisfy to earn compliance. For example, a test house accredited only for EMI testing to CISPR 22 cannot issue an endorsed report if testing to CISPR 14 or to any other standard not covered by the terms of the accreditation. A copy of the actual scope should be requested if in doubt.

Does the scope of accreditation cover the complete standard? An accreditation for a particular standard may limit the frequency range or exclude some of the clauses in that standard. A test house's limited accreditation may mean that it may not be possible for that test house to establish your product's compliance with the complete standard. For example, a test house accredited to CISPR 22 may be restricted to frequencies up to 1000 MHz. If your product requires FCC testing for harmonics up to 4 GHz, then the test report may not be endorsed for frequencies above 1000 MHz.

Is the testing subcontracted to another test house? It is important to know whether the test house has an in-house test capability or if the test will be subcontracted to another test house. Some consultants including Competent Bodies and Conformity Assessment Bodies advertise testing and certification services but actually subcontract the testing to local or overseas test houses. Such double handling is likely to inflate test costs, delay report generation, and inevitably frustrate the flow of correspondence if a failure occurs and fixes are required. ISO/IEC Guide 25 requires that the test house notify the client in advance of any subcontractor testing and that the subcontractor must have the appropriate accreditation. Unaccredited subcontractors should not be accepted.

Will an endorsed test report be provided? Companies also should inquire whether there is a surcharge for an endorsed report and how many copies of the final report they are entitled to receive.

What is the level of test house expertise? You may want to ask about the experience of the staff who actually perform the tests. The experience and proficiency of the test house personnel will directly affect the test duration and accuracy. You may want to inquire about the test house's use of automated compliance test equipment and its test procedures, which can affect efficiency in testing time and costs.

Does the quoted price include a desk/design review prior to the testing program? The probability of test failure is very high for first-time testing. A brief desk/design review by an experienced EMC test house can quickly identify potential trouble spots and help to minimize potential test failures, and thereby reduce test time and testing costs.

What happens if the product fails the EMC tests? You will want to know the test house policy for when a product fails the compliance test. Ask whether testing proceeds to conclusion followed by the issue of a noncompliance report. Also, determine if the test house automatically performs simple diagnostic tests once a noncompliance has been recorded. A brief fault investigation at this stage can save one pass through the test house.

Does the test house supply spectrum plots of EMI measurements? Spectrum plots of different test configurations can help diagnose and rectify an EMI failure. You will want to ask about the additional costs for a retest if a product fails the initial test. Inquire whether the original fee applies again.

What is the test house policy on witnessing the testing of the product? If the test house does permit you to view the testing, you will want to know if there is a surcharge. Witnessing testing provides companies with valuable insight into the EMC issues relating to your product, and this can benefit future product design.

Does the test house provide a consultation service to assist in achieving compliance? If consultation is offered, ask about the levels of experience and qualifications of the consultant. Your company can benefit from the test-house practical experience gained from thousands of tests and fixes.

Most countries have regulations that mandate compliance with EMC standards before products can be legally marketed. When selecting an experienced EMC test house, companies can be well served to work with one that is also a Competent Body and Conformity Assessment Body. By asking the right questions, you can locate a test house that is accredited to test to all of the relevant EMC standards and that can assist with the complexities of regulatory approvals, standards, and specifications.

Employing MRA-accredited testing is the lowest risk approach to EMC compliance and can help facilitate global regulatory acceptance of your product. MRA-accredited reports are accepted by Competent Bodies and Conformity Assessment Bodies and may be used to support a TCF. ISO/IEC Guide 25 accredited test reports can serve as your product's passport through trade barriers into overseas markets.

Chris Zombolas is technical director for EMC Technologies Pty Ltd. in Australia. He can be reached at chris@emctech.com.au.