Use of Third Party EMC or Radio Test Laboratories

There are numerous reasons for the use of an external test laboratory by organizations developing, manufacturing or marketing electric or electronic products. These reasons may include lack of or limited testing capability, scheduling conflicts within the organization, etc. Whatever the case may be, the proper selection of an external third party test laboratory is critical since the test results may be used to demonstrate product compliance or to verify changes to a product design.

Due to the importance of test accuracy provided by the external test laboratory, many organizations require that external test laboratories be accredited, to ensure correct and reliable results. Despite the fact that accreditation determines a minimum proficiency level of a test laboratory, the accreditation process itself has some limitations. Therefore, a purchasing organization should not solely rely on the accreditation of a test laboratory. Some additional evaluations should be performed to ensure the adequacy of testing services. This article describes the role of accreditation and its benefits, discusses the basic principles of the quality standard ISO/IEC 17025-2005 and clarifies the difference between accreditation and certification which are often incorrectly used interchangeably. The limitations of accreditation and some scenarios for the purchase of external testing services are provided as well and some relevant issues to be considered are identified for a successful cooperation with an external test laboratory.

The Role of Accreditation
Since 1990, the accreditation of EMC laboratories has become increasingly important in many parts of the world. This development has been mainly driven by the sharp increase in the number of electric and electronic products that have been introduced to the global market place. Technological advances in the high tech areas of data communication, wireless communication, computer networking and many others, lead to a proliferation of products in the business, professional and in the residential environment. This proliferation of electronic products and the trend to shorter product life cycles as well as more rapid consumer product turnovers lead to a drastic increase in the total number of electronic products that are in use today. The compliance of most of these products with national and international Electromagnetic Compatibility (EMC) requirements is to be determined and documented before they can be marketed. In many countries such as the US or economies like the European Union, the manufacturers themselves can declare the conformity of their products with applicable standards. This approach is called “Declaration of Conformity” (DoC) and is applicable to certain product categories, which are determined by the regulatory authority of the different countries. This way of determining and documenting product compliance is more efficient than the verification or certification schemes that were in use in the past and required direct involvement of regulatory authorities to various degrees. A rapid product introduction is of the essence today, in light of decreasing product life cycles and the increasing number of products being introduced. Many other product categories like those with transmit functions, (above a certain level of transmit power) still require specific approval of the regulatory authority in many countries.

The measurements associated with the determination of product compliance with applicable EMC standards and the approvals of products by regulatory authorities, can be very time consuming. Qualified test laboratories can help reduce the test and approval periods, especially when regulatory authorities accept test data and reports documented by the test laboratories without further evaluations. For example, in the US, an EMC test laboratory that is accredited by A2LA (American Association for Laboratory Accreditation), ACLASS (ANSI-ASQ National Accreditation Board) or NVLAP (National Voluntary Laboratory Accreditation Program) to perform EMC testing in accordance with applicable FCC rules, may prepare test reports which can serve as the basis of a declaration of conformity by the manufacturer for Information Technology Equipment (ITE). The regulatory body for EMC in the US, the Federal Communications Commission, (FCC) will not have to be involved in the product approval process for ITE equipment in this case. In the international context, many Mutual Recognition Agreements (MRAs) between the US and foreign economies are in place to allow swifter product introductions into foreign markets and thus stimulate trade. These product introductions involve, among other testing activities, EMC compliance testing by US test laboratories to foreign EMC requirements (like Korean or Taiwanese standards). Accreditation of US EMC test laboratories to these foreign standards serves as a basis for their recognition by the foreign regulatory authority as a conformance assessment body (CAB). There is an additional recognition process established that EMC laboratories in the US must follow to obtain this recognition.

The Benefits of EMC Laboratory Accreditation [1]
Accreditation provides a formal recognition for competent EMC testing laboratories based on the verification of implementation of a quality system in the laboratory (in accordance with ISO/IEC 17025) and the determination of a minimum level of technical proficiency to perform the EMC tests the laboratory is accredited for. This formal and public recognition allows customers to identify and select independently verified testing services. For EMC laboratories to maintain this recognition, regular evaluations by the accreditation body are performed to ensure the on-going compliance with requirements and to verify that the standard of operation is being maintained or improved. The accredited EMC laboratory is also required to participate in relevant proficiency testing programs between reassessments, as a further demonstration of technical competence, or the laboratory must design their own testing activities that demonstrate the quality of their test data over time.

There are at least four distinct groups that benefit from accreditation in general: EMC laboratories themselves, users of laboratory testing services, regulatory authorities (private and public entities that require quality test data to operate) and the general public.

EMC test laboratories benefit from a technically sound assessment and accreditation by an internationally recognized accreditation body. Some of these benefits are:

1. An independent and public statement of a recognized third party that designates the laboratory as qualified to provide services in the EMC field
2. A regular and objective surveillance that aids the management of an EMC laboratory to continuously improve its operation
3. In an increasing number of instances, an entry to a given market that would otherwise be closed to the laboratory
4. Increased laboratory productivity, resulting from a decrease in the number of clients who insist on having their own staff members audit the laboratory. More of these clients now base their confidence on a third-party accreditation
5. International recognition of the competence of an accredited EMC laboratory is obtained if the
6. accreditation body is a signatory to the mutual
7. recognition arrangement of the International Laboratory Accreditation Cooperation (ILAC)
8. On-site assessments help the technical staff members of the accredited EMC laboratory to verify that the latest requirements in applicable standards are properly implemented and applied
9. Improved performance by laboratory staff members. Undergoing regular assessments enhances staff discipline and its sense of professionalism. Employees are more likely to be committed to observing the quality management system and standards of performance of the laboratory

Users of EMC laboratory testing services are a second group of beneficiaries of laboratory accreditation. Customers have greater confidence in the accuracy of the test report they are purchasing because it has been generated by a competent facility. This is particularly true for an educated client, one who is aware of the scope of the laboratory’s accreditation.

Manufacturers (for example in the automotive industry) may also gain efficiency through accreditation since these organizations do not have to perform their own on-site assessments themselves but can defer to the assessments of competent accrediting authorities. Other manufacturers who have in-house EMC testing capabilities may reduce or even eliminate these overhead costs by using external accredited laboratories with the assurance of technical proficiency.

Regulatory authorities often require accreditation to national or international standards. With restricted budgets, many regulatory authorities can no longer perform EMC testing and product approvals themselves and must rely on third-party laboratories to support their regulatory efforts. When they do so, these authorities need a comparable and meaningful basis for identifying qualified EMC test service providers, which can be achieved through the accreditation process.

Accreditation also has a positive impact on the general public, by stimulating higher standards of quality within EMC testing laboratories. This leads to more consistently reliable test data, thereby contributing to more effective EMC regulations, more consistent product quality and the proper functioning of electronic devices within close proximity of each other.

ISO/IEC 17025 – The Standard for Laboratory Competence [1]
The general requirements for laboratory competence are described in the ISO/IEC 17025:2005 standard.
This standard establishes a global baseline for accreditation of all types of laboratories. Since its origin in the mid-70s, ISO/IEC 17025 (formerly ISO/IEC Guide 25) emphasizes competence of laboratories to perform specified tests, not just mere compliance with requirements.

Several important principles are imbedded in the requirements of the standard. These principles are summarized as follows:

Capacity
An EMC laboratory must have the resources (staff members with the required skills and knowledge, test environment with the required facilities, equipment, instrumentation, procedures to ensure consistency of test processes and quality control for the key steps in the testing processes) in order to carry out the tests and produce reliable results.

Responsibility
An EMC laboratory must have staff members in the organization who have the authority to execute specific functions with the overall scope of test work. They also must be able to demonstrate accountability for the published test results.

Scientific Approach
An EMC laboratory should conduct its work based on accepted scientific principles, preferably following published EMC standards. If deviations from accepted methods are necessary to perform an evaluation of a specific device, they must be substantiated and documented in a manner considered generally acceptable by experts in the field.

Objectivity
The test results produced should be based upon measurable quantities. If results are subjective (applicable to some immunity tests) they must be produced by testing personnel deemed qualified to make subjective judgments.

Impartiality
The pursuit of reliable results through the use of accepted scientific principles, is the primary and overriding influence on the persons carrying out the testing. All other influences are secondary and not permitted to take precedence.

Measurement Traceability
The results produced are based on a recognized system of measurements that are derived from accepted known quantities (i.e., SI system) or other well-characterized references. The chain of measurement comparison between these accepted known quantities and the device providing the objective measurement result is unbroken for the transfer of measurement characteristics, including uncertainty, for the whole of the measurement chain.

Reproducibility
The EMC test methods used to achieve measurement results will produce results that are comparable to future testing results, which will be produced under similar circumstances. These circumstances are defined primarily by the applied EMC standard, the equipment used and the knowledge and technical proficiency of test personnel.

Transparency
The test and quality processes within an EMC laboratory must be open to both external and internal scrutiny in order to easily identify factors which may adversely affect the laboratory’s pursuit of objective results based on published standards.

Accreditation versus Certification
Laboratory accreditation uses criteria and procedures specifically developed to determine technical competence. Qualified technical assessors, conduct a thorough evaluation of all factors in a laboratory that affect the production of test or calibration data. Very often these criteria are based on ISO/IEC 17025, which is used for evaluating EMC test laboratories throughout the world. Laboratory accreditation bodies use this standard specifically to assess factors relevant to the laboratory’s technical competence. These factors include:

1. Technical competency of staff members
2. Validity and appropriateness ofEMC test methods
3. Traceability of measurements to national standards
4. Adequacy, calibration and maintenance of test equipment(for example in accordance with CISPR 16-1-1/2/3/4)
5. Adequacy of test environment(for example in accordance with CISPR 16-1-4)
6. Handling and transportation oftest samples
7. Quality assurance of test dataover time
8. Reporting of EMC test results

By applying this process, laboratory accreditation aims at assuring the accuracy and reliability of test data of an EMC test laboratory. The ISO 9001 quality system standard, is widely used in manufacturing and service organizations to evaluate their system for managing the quality of their product or service. The goal of certifying a quality management system of an organization against ISO 9001, is the confirmation of compliance of the management system to this standard. An EMC test laboratory may be certified to ISO 9001, but such a certification does not make any statement about the technical competence of a laboratory. Despite the fact that accreditation also covers certain elements that are evaluated during a certification process, no minimum level of technical proficiency is established, which is very often required by regulatory bodies, for example within the frame work of the product approval process.

Limitations of the Accreditation Process
As discussed above, the accreditation process establishes a minimum level of technical proficiency and ensures the implementation of a quality system based on ISO/IEC 17025-2005. Due to time constraints, assessors must select a number of test methods for a detailed review during the on-site assessment. This means that some test methods on the scope of accreditation cannot be reviewed in detail during the on-site assessment. The assessor as well as the accreditation body must rely on the proper implementation of relevant processes, such as equipment calibration and traceability, supervision of testing activities, adequate training of personnel, etc. for technical proficiency related to these methods. It should also be kept in mind that the on-site assessment is a snapshot in time, meaning, assessors can only observe the testing activities during the on-site assessment. Since there is no continuous monitoring of testing activities on-site over time (other than the re-assessment as part of the re-accreditation process every two years) and no unannounced assessments are performed, the accreditation body must again rely on the proper implementation of all relevant procedures that ensure the quality of testing activities over time.

Accreditation of tests methods does not guarantee accuracy of test results, nor can it prevent mistakes. However, through the implementation of quality system requirements called out in ISO/IEC 17025-2005, the potential for errors is significantly reduced but not eliminated. Many of these requirements are implemented as procedures which the laboratory staff members must apply when performing testing activities. The level of detail of these procedures is defined by the laboratory itself. The laboratory must also determine the necessary training activities to support the proper implementation of such procedures. Without objective evidence of a nonconformance, the accreditation body cannot prescribe the level of detail of procedures nor request training activities to ensure the proper implementation. In addition, the laboratory must ensure within the frame work of the established quality system that adequate supervision is provided when necessary, the test results as well as test reports are properly reviewed and supporting activities such as equipment calibration, test environment maintenance, control of environmental parameters, technical training and that quality assurance measures are in place to reduce the possibilities for errors and improve the accuracy of test results.

Another important factor for prevention of mistakes is a proper contract review process. Whenever an accredited laboratory receives a request for testing it must ensure that the technical content of the request is properly understood.

All relevant parameters related to the testing activities must be defined (e.g., supply voltage and frequency, operating modes of EUTs, specifics of EUT test setups, etc), and the laboratory must verify that the requested tests can be performed within the requested time frame. This review process is essential to meet the expectations of the requestor. Any discrepancy between the submitted request and the review of the laboratory are to be resolved before testing commences. On part of the laboratory, a technically competent staff member must approve the test request, indicating that the test laboratory can perform the defined activity under the scope of accreditation, as stated in the contract review results. If parts of the requested test cannot be performed under the scope of accreditation, the requestor must be informed of this fact. The level of detail and the actual review process are within the responsibility of the test laboratory, not the accreditation body. Therefore, any test laboratory that puts emphasis on quality in testing work will have a suitably detailed contract review process and will prepare a detailed review summary for consideration and/or approval by the requestor.

Scenarios for Purchasing External Testing Services
The reasons for purchasing external testing services can be numerous, but usually two main categories of the testing services can be distinguished, which are compliance and pre-compliance testing. The purpose of compliance testing is the determination of product conformance with identified standards or regulations. The test result is used as evidence of compliance, and therefore, the measurements have to be made in accordance with a standardized method and in a defined test environment using specified test equipment. In addition, requirements generally exist for the setup of the equipment under test (EUT). Some regulatory authorities such as the FCC in the United States, require the test laboratory be accredited to perform specific compliance tests, which rules out the use of a non-accredited test laboratory for such purposes. The FCC regulations, for example, define the requirements for the equipment authorization program which stipulate the use of an accredited test laboratory when testing products subject to Declaration of Conformity (DoC) procedures and which may be used to test products to be authorized under the Certification and Verification procedures. The FCC rules allow for recognition of test laboratories as “2.948 listed”, per section 2.948(a)(2) and as an “accredited” test laboratory under 2.948(d) for domestic testing laboratories and 2.948(e) for foreign test laboratories. However, test laboratories that are “2.948 listed” and are not accredited, cannot test devices subject to DoC procedures to demonstrate compliance with FCC technical regulations.

When compliance test services are requested, the purchasing organization must verify the existence of accreditation of these test methods. This can be done by carefully reviewing the scope of accreditation of the laboratory. For testing laboratories, the scope of accreditation is usually identified in terms of standard test methods that are prepared by national, international, and professional standards writing bodies. If a laboratory wishes accreditation only for a superseded version of a standard test method, the date of the version used is identified in the scope of accreditation. When the date is not identified in the scope of accreditation, test laboratories are expected to be competent in the use of the current version within one year of the publication date of the standard test method.

If testing services in accordance with foreign requirements (e.g., Korea or Taiwan) are to be purchased from a test laboratory based in the US, the inclusion of such test methods on the scope of accreditation and the proper designation of the US test laboratory by the designating authority (i.e., NIST) is to be verified.

In order to ensure adequacy of the purchased testing service, the purchasing organization should consider addressing the following subjects with the test laboratory for emissions testing:

1. If a product is to be tested for equipment authorization using the DoC approach, the measurement standard to be applied is ANSI C63.4. At this point in time, the FCC permits the use of two versions of this standard, namely ANSI C63.4-2003 or ANSI C63.4-2009, until further notice. The two versions differ significantly in the areas of antenna calibration requirements, site validation requirements above 1 GHz, setup of Video Display terminals and much more. Therefore, the purchasing organization must specify which version of ANSI C63.4 is to be used for the tests and verify that the test laboratory is accredited for the selected revision of ANSI C63.4.
2. The test site used to perform radiated emission measurements below 1 GHz may be evaluated by a broadband NSA measurement using broadband antennas or by NSA measurements at specific frequencies using tuned dipole antennas. It is preferable to have broadband NSA data available to more completely characterize a test site. An accreditation body cannot require that a test laboratory performs broadband NSA measurements if the applied standard (ANSI C63.4-2003 or ANSI C63.4-2009 in the US) supports both the discrete and the broadband NSA measurement approach for site validation. Hence, it is up to the purchasing organization to ensure that the site validation is suitable for their purposes.
3. For radiated emission measurements above 1 GHz, the suitability of the test site is defined differently in the two previously mentioned versions of ANSI C63.4. In the 2003 version, no real requirements for the test site specification in frequency range above 1 GHz exist. It is only stipulated that a test site meeting the NSA criterion below 1 GHz must be used. This requirement has changed in the 2009 version of the standard. In addition to meeting the NSA requirement for the frequency range below 1 GHz,
4. the test site must now also either meet the SVSWR requirement called out in CISPR 16-1-4 (up to 18 GHz) or measurements above 1 GHz must be performed with absorbing material of a given size that must be placed on the ground plane between the antenna and the EUT. The purchasing organization should clarify which approach is used to meet the site requirements above 1 GHz. The absorber placement primarily aims at the reduction of reflections from the ground plane. The SVSWR requirement on the other hand, evaluates the test volume including the walls and the ceiling of a test environment, in addition to the ground plane reflections. Again, an accreditation body cannot require the test laboratory meet the more stringent SVSWR requirement since ANSI C63.4-2009 offers both approaches.
5. For the frequency range above 1 GHz, the purchasing organization should verify the test distance that will be used to perform the measurements. FCC rules allow performing measurements at distances different from the distance at which the applicable limit is defined. A shorter test distance is usually required to provide adequate sensitivity for the measurement. The reduction of the test distance will then require a mathematical “correction” of the measurement data before comparing the levels to the applicable limit. It is certainly preferable to perform any test at the measurement distance in which the limit is defined. Simple mathematical adjustments made to compensate for different test distances are error prone and can cause significant repeatability problems. The purchasing organization should know at which actual distance the measurements are made.
6. The purchasing organization should ask for a sample test report. Despite the fact that accreditation requires a certain minimum content of test reports, the report layout and inclusion of supporting information is the decision of the test laboratory. Therefore, the purchasing organization should have a clear understanding about the test report structure and content before testing commences. This may be of particular importance if such a test report is to be used for product approval purposes at a later time. Some organizations or regulatory authorities have specific requirements as far as content and layout is concerned; the test laboratory has to be made aware of these requirements in order to provide the proper documentation.
7. The purchasing organization should also inquire about how the test laboratory keeps abreast of changes in technical standards and how interpretations of technical standards are obtained. This is a particularly critical aspect since standards are constantly revised and new standards are introduced (e.g., ANSI C63.10 as a test standard for intentional radiators) which may have a direct impact on the test result. Test laboratories must keep their test methods updated and understand how the new requirements affect their operations. Accreditation bodies cannot require a specific approach to ensure that test laboratories keep current with standards and regulations. Therefore, it is upon the requestor of testing services to determine if the approach chosen by the test laboratory in question seems adequate.
8. The purchasing organization should also inquire about the test equipment that will be used to perform the test, if manual or automated testing will be performed and which test environment will be used (e.g., OATS versus semi-anechoic chamber). The underlying standards permit the use of different types of test equipment (e.g., EMI receiver versus spectrum analyzer) and also allow manual as well as automated testing. The required skill as well as the test procedure content may vary significantly, based on the chosen equipment, measurement mode and test environment. A purchasing organization should clearly understand how the measurements will be performed before testing commences.

Pre-compliance measurements usually do not follow a standardized test method in all details since the purpose of such measurements is different from compliance measurements. These measurements are performed, for example, to verify designs or evaluate design changes and may deviate considerably from established test methods. Therefore, the purchasing organization may have to define many measurement parameters, such as frequency range (possibly specific frequencies to be evaluated), detector and resolution bandwidth, test distance, etc. to ensure that the measurement result meets the purpose of the evaluation process. In this context, the accreditation of the test laboratory may be of secondary interest; it must be ensured that the test laboratory can perform the measurements to meet the requestor’s needs. The test request review plays a particularly important role since the required measurements may be mostly based on the definition of the purchasing organization. In addition, the content and layout of the test report should be agreed upon before testing commences.

Summary
The accreditation of EMC and Radio test laboratories around the world becomes more important with the globalization of trade and the proliferation of electronic and electric products in all aspects of life. Regulatory authorities in many countries have changed product approval processes for various product categories and now allow manufacturers to determine and declare product compliance with applicable standards. Furthermore, qualified EMC and radio test laboratories may now test products in accordance with foreign requirements and prepare test reports that serve as the basis for product approvals in foreign markets. EMC and Radio test laboratories must demonstrate their technical proficiency to perform these tests and also establish a quality frame work that allows testing under repeatable and consistent conditions. The laboratory accreditation process applied by recognized accreditation bodies, that is based on the generally accepted standard ISO/IEC 17025-2005, allows test laboratories to obtain this independent determination and documentation of technical proficiency in the field of EMC. However, the accreditation process also has limitations that must be understood, especially by customers of accredited test laboratories. Further investigations may have to be undertaken to clearly understand the capability of a test laboratory. This will ensure the adequacy of future testing services and will lead to a smooth and satisfactory cooperation between organizations and external test laboratories.

Acknowledgements
The author would like to thank Mrs. Tori Barling for proof reading this manuscript.

References

1. Peter S. Unger, “The Benefits of Laboratory Accreditation,” October 2002

Werner Schaefer is a compliance quality manager and technical leader for EMC and RF/uwave calibrations at Corporate Compliance Center of Cisco Systems in San Jose, CA. He has 25 years of EMC experience, including EMI test system and software design, EMI test method development and EMI standards development. He is the chairman of CISPR/A/WG1 and a member of CISPR/A/WG2 and CISPR/B/WG1. He also is the US Technical Advisor to CISPR/A and a member of ANSI C63, SC1/3/5/6/8, and serves as an A2LA and NVLAP lead assessor for EMI and wireless testing, software and protocol testing and RF/microwave calibration laboratories. He also serves as an ANSI representative to ISO CASCO, responsible for quality standards like ISO 17025 and ISO 17043. He is a member of the Board of Directors of the IEEE EMC Society.

He was actively involved in the development of the new standard ANSI C63.10 and the latest revision of ANSI C63.4, mainly focusing on test equipment specifications, use of spectrum analyzers and site validation procedures.

Werner Schaefer is also a RAB certified quality systems lead auditor, and a NARTE certified EMC engineer.

He published over 50 papers on EMC, RF/uwave and quality assurance topics, conducted numerous trainings
and workshops on these topics and co-authored a book on RF/uwave measurements in Germany.