Internal and External EMC labs
If the designer/manufacturer is part of a large organization, they most likely will have an internal EMC lab that they can approach and schedule time for a preliminary or final (qualification) test of their product. However, if the internal EMC lab is tightly-scheduled; the project manager may be invited to look outside the company for an external source of EMC lab expertise in order to meet his/her project schedule. In the ideal case, the project manager may have the opportunity to investigate several competing labs and solicit bids from the same.
If the designer/manufacturer is not part of a large organization, then the project manager for the development project is immediately put into the position of soliciting bids and information from external EMC labs.
First Impressions
When soliciting bids from external EMC testing labs, first impressions are significant. If the EMC testing lab does not return phone calls, that is an indication of a lack of interest in new business or a lack of an organizational structure to respond to customer inquiries. Either way, you may want to seek another EMC testing lab.
If the lab returns your phone call, then the next step is to ask for a bid to do certain tests that will allow you to verify your design or qualify it for shipment to customers. The EMC tests needed for your commercial product will, in general, consist of both emission and immunity tests. These tests will encompass United States emission requirements, European Union and International emission requirements, and European Union and International immunity requirements.
Once the bids are received and compared, you are ready to make an on-site visit to the potential EMC lab. Again, the first visit to the EMC lab is critical for both you and the lab. First impressions of the lab are just as important as the first phone-call impression. The first impression of the lab consists of both a “gut check” and an “intellectual check.”
The gut check is a feeling about the lab and its people. If you don’t feel right about the lab personnel nor the lab’s facilities or equipment; you might surmise that your “uneasy feeling” is based on a deeper issue you will uncover when you use the lab.
The intellectual check is more of a “technical checklist” concept where you either have a mental checklist or a written checklist on specific administrative or technical items that you want to investigate. These items could include test equipment, calibration of the test equipment, test facilities, and sample test reports.
Geographical Proximity
Most EMC testing labs used by designers/manufacturers are geographically situated in close proximity to a concentration of intended users. This should allow for an easy inspection of the lab. The EMC lab should be proud to show you their lab and to discuss their capabilities. They should also have an open-door policy that allows their customers to observe the testing of their products through the entire battery of EMC tests.
A lab that is geographically close to its customers also allows engineers and technicians who designed and developed the product the freedom to troubleshoot the product easily if it fails one of the EMC tests during preliminary testing. That is, they can readily make modifications to the products because the electrical engineers, mechanical engineers, and power-supply engineers are close at hand. An EMC lab that is distant from the design center makes it more difficult (telephone consulting), more time-consuming (extra travel time), and more costly (travel costs).
If the lab is geographically close, the first visit leaves you with a positive impression, and the financial bid is in the acceptable range, then, it is time to check on some of the other attributes that a high-performing EMC lab will possess.
Accreditation
One of the key qualities that a high-performing EMC testing lab will possess is that it will be an “Accredited Laboratory.” In the United States we have three accreditation bodies that are recognized by the United States Federal Communications Commission (FCC) for EMC testing, the American Association for Laboratory Accreditation (A2LA), the United States Department of Commerce’s National Institute of Standards and Technology (NIST), National Voluntary Laboratory Accreditation Program (NVLAP), and ACLASS (an ANSI-ASQ National Accreditation Board Company). A2LA and ACLASS are private organizations while NVLAP is part of the United States Government. It should be noted that there are other qualified accreditation bodies outside of the United States that can accredit labs internationally. In some cases, EMC testing labs in countries other than the USA will ask to be accredited by one of the three United States accreditation bodies. The International Laboratory Accreditation Cooperation (ILAC) is the international-body that designates accreditation bodies around the world and assures they are meeting standard accreditation requirements.
Accreditation bodies will assess EMC testing labs to the requirements of ISO/IEC 17025 – General Requirements for the Competence of Testing and Calibration Laboratories. The latest version of this standard is dated 2005. It superseded the first edition of 17025 which was released in 1999 (it replaced ISO/IEC Guide 25 and European Norm 45001).
Laboratory accreditation has been incorporated into the laws of the United States by the Federal Communications Commission (FCC). The Commission allows a large number of electronic products that are tested in accredited EMC testing labs to be placed on the market with no further government approval for EMC criteria. The specific process using accredited EMC testing labs is called the Declaration of Conformity (DoC) by the FCC. It is preceded by a Manufacturer’s Declaration of Conformity or a Self Declaration of Conformity before the official declaration based on testing in an accredited EMC testing lab.
Declaration of Conformities can apply to such digital devices as Class B personal computers, Class B computer peripherals, citizens band (CB) receivers, television-interface devices, and consumer Industrial, Scientific, and Medical (ISM) equipment. The DoC concept has allowed products to be marketed more quickly and aided in improving our quality of life while at the same time protecting licensed communications services in the United States.
International Ramifications
Because the laboratory accreditation process is built around an international standard, this allows products to potentially flow more smoothly in the world trade arena. This is accomplished by the EMC lab being accredited for appropriate test methods, by the EMC lab writing a test report that complies with ISO/IEC 17025 report requirements, and by the EMC lab properly using the accreditation body’s symbol and logo on the test report.
The accreditation body’s mark on the test report signifies that the testing was done in an accredited lab and that the tests performed by the lab were within the scope of its accreditation. (Note – the test report must indicate in the body of the report if tests were performed that were not on the testing lab’s scope of accreditation). This sends a clear signal to any country importing the product that it is in compliance with the stated requirements.
Often times, this means that the product will be cleared quickly through customs and be place on the market. Without the mark on the test report, the product could be destroyed, returned to the country of origin (originating manufacturer), or retested in an accredited laboratory in the country where the product is to
be marketed.
ISO/IEC 17025 – Management Requirements
The international standard on criteria for testing labs is ISO/IEC 17025 which includes both Management Requirements and Technical Requirements. The Management Requirements are very similar to those found in ISO 9001:2008 – Quality Management System – Requirements.
The Management Requirements in ISO/IEC 17025 encompass the following areas:
- Organization
- Management System
- Document Control
- Review of Requests. Tenders, and Contracts
- Subcontracting of Tests (and Calibrations)
- Purchasing Services and Supplies
- Service to the Customer
- Complaints
- Control of Nonconforming Testing (and/or Calibration) Work
- Improvement
- Corrective Action
- Preventive Action
- Control of Records
- Internal Audits
- Management Reviews
The organization of the EMC testing lab is its management structure (for example, who is the president of the lab and who has key areas of responsibility under the president such as quality control). It is also the organizational entity that can be held legally responsible for the actions of the EMC testing lab. A potential user of the EMC lab should look at the organizational structure and be comfortable with the organizational chart and with the qualifications of the individuals filling the key slots.
The EMC labs management system must be appropriate to the scope of the EMC activities offered. The management system must be documented; it shall have detailed policies, procedures, programs, and specific work instructions sufficient to assure a high-quality test effort on a consistent basis. The management system must be in written form; it can be available in hard-copy format or stored on a server in a soft-copy format.
The document control portion of the Management Requirements can be checked by looking at the EMC testing labs quality manual and by examining some representative documents. The key element is that the lab should demonstrate a process that is under control; that is, a process in which all documents are identifiable and controllable.
The fourth Management Requirement is Review of Requests, Tenders, and Contracts and it is very important for a potential user of the lab. This requirement will encourage the lab to review your request for a test and establish a contract between the lab user and the lab. The contract should specify the requests of the lab user
and it should allow for amendments to the contract assuming agreement by both parties.
For testing labs, the Management Requirement that is stated as Subcontracting of Tests and Calibrations should be read as Subcontracting of Tests. That is, because ISO/IEC 17025 is written for both testing labs and calibration labs, the testing lab must read the requirements as stated for a testing lab and not as stated for a calibration lab (For example, calibration labs would read the Management Requirement as Subcontracting of Calibrations.) An accredited testing lab may subcontract some of its tests to another accredited testing lab due to a temporary lack of test equipment or other similar legitimate reasons. In general, a long-term subcontract relationship is not allowed since an accredited testing lab shall have the capability to perform the tests on its scope of accreditation.
For an EMC testing lab, the management requirement Purchasing of Services and Supplies – which are critical to the operation of the lab – is most often focused on its purchase of calibration services. The calibration of the EMC testing labs equipment is a key factor in making proper measurements that are traceable to fundamental national and international standards. A user of the EMC testing lab should feel confident that the calibration labs being used by the EMC testing lab are accredited for calibration services.
Service to the Customer is that aspect of the EMC testing labs operation that makes a user feel comfortable about the lab. For example, the user should be allowed to observe the labs performance in testing their products. Excellent communications between the customer and the EMC lab is also consistent with this area of the Management Requirements.
If you, as a customer, complain to the EMC testing lab, how does the lab react? Do they investigate the complaint and make changes? Or do they ignore your complaint and continue on with the approach that this is the way we always do this test. A high-quality lab will respond to customer complaints and, if warranted, make appropriate changes in their procedures after a thorough investigation.
Control of Nonconforming Testing is that area of the Management Requirements that addresses mistakes made by the EMC lab in its testing service. Does the lab offer to redo the test that was done incorrectly for no additional charge? A user of the lab should familiarize himself with the testing labs philosophy in this area.
The next area of Management Requirements is Improvement. The EMC testing lab should have a continual improvement philosophy consistent with Quality Assurance theory and practice. One location that this emphasis on Improvement can be illustrated is in the EMC testing labs Quality Policy Statement which should be prominently displayed in the lab and it should be clearly understood by the employees of the lab.
The next part of the management requirements; Corrective Action is closely related to Complaints and Improvements. This part of the Management Requirements addresses the actions the lab takes to satisfy Customer Complaints. When a user identifies a problem, it is essential that the lab institute a root cause analysis and follow their logical trouble-shooting to a solution to the problem. A fair question for a potential user to ask the EMC lab is “What corrective actions have been taken in the past to satisfy customer requirements?”
Preventive Action is more difficult for a potential user of the EMC testing lab to identify. It involves the continuous improvement aspect of the ISO/IEC 17025 standard. One example of a Preventive Action situation is a lab that has calibration complaints on antennas in the frequency range below 1 GHz should also look at potential calibration problems on antennas above 1 GHz as a preventive measure.
The next management requirement is Control of Records. In the context of ISO/IEC 17025, the records can be either a quality record or a technical record. Quality records include reports from internal audits, minutes of management reviews, records of corrective actions, and records of preventive actions. Technical records include accumulations of data and information which result from carrying out tests and which indicate whether specified quality or process parameters are achieved. They may include forms, contracts, work sheets, work books, check sheets, work notes, control graphs, external and internal test reports, customers notes, customers papers, and customers feedback. The records should include the identity of personnel responsible for the performance of tests and checking of the test results. How does the lab protect and control its records? What evidence do you see that the lab has its records held securely and in a manner to maintain confidentiality? Your test results will become part of the record-keeping system; make sure your privacy and confidentiality are protected.
Every EMC testing lab should perform an internal audit at least yearly. This is a semi-formal audit done by member of the lab and it is intended to review the operations of the lab including both management and technical requirements. The lab should have a record of its past internal audits and a plan and schedule for future audits.
Management Reviews are intended to be performed by upper management of the lab. There are 11 specific areas that shall be reviewed in Management Review. They include: (1) the suitability of policies and procedures, (2) reports from management and supervisory personnel, (3) the outcome of recent internal audits, (4) corrective and preventive actions, (5) assessments by external bodies, (6) the results of inter-laboratory comparisons of proficiency tests, (7) changes in the volume and type of work, (8) customer feedback, (9) complaints, (10) recommendations for improvements, and (11) other relevant factors such as quality control activities, resources, and staff training. The Minutes of the Management Reviews should reflect the above eleven items. The Management Reviews should be done annually.
ISO/IEC 17025 – Technical Requirements
The Technical Requirements section of ISO/IEC 17025 is what differentiates it from the ISO 9001 Standard. An EMC testing laboratory can meet ISO 9001 and still not be in full compliance with ISO/IEC 17025 unless it also meets the Technical Requirements. On the other hand, a lab that is accredited to ISO/IEC 17025 can be considered to be in compliance with ISO 9001 and its management requirements.
The ISO/IEC 17025 Technical Requirements are:
- General
- Personnel
- Accommodation and Environmental Conditions
- Test (and Calibration) Methods and Method Validation
- Equipment
- Measurement Traceability
- Sampling
- Handling of Test (and Calibration) Items
- Assuring the Quality of Test (and Calibration) Results
- Reporting the Results
General is the first section of the Technical Requirements. It is basically a listing of the requirements in the technical requirements portion of ISO/IEC 17025 plus a comment on the total uncertainty of measurement.
Personnel is the next section of the Technical Requirements. People make a testing laboratory successful. An EMC testing lab provides an engineering service, and a service business must be people-oriented. So as a customer of a lab you should feel comfortable with the technical personnel you are going to be spending 8-hours a day with on your testing needs. You should check their technical qualifications (engineering degrees, technical associate degrees, years of experience in EMC, personnel certificates from iNARTE and other similar personnel certification bodies). On-going education is also important. Do you see the individuals from the EMC lab attending local meetings of the IEEE EMC Society? Are the technical personnel actively attending workshops and seminars on EMC. Test results on your product are a function of the technical training of the technical personnel coupled with excellent test equipment and test facilities. The customer of the lab should make sure the lab personnel have had adequate training and that they are keeping up to date on the latest changes in EMC standards, EMC design, EMC test equipment, and similar pertinent
EMC areas.
An EMC testing lab relies heavily on its laboratory facilities. So, the technical requirement titled Accommodation and Environmental Conditions is a key aspect of a testing laboratory. For example, does the lab have both 50 Hz and 60 Hz power available? Does it have a variety of voltages for alternating current available? Make sure that the lab has a power source for alternating current that will satisfy your product design. You will also want to see a separation of emission and immunity testing activities so that the immunity testing does not adversely affect the radiated and conducted emission profiles of the product. Does the lab have the capability to test for radiated emission at a 10-meter antenna distance? As mentioned earlier in this article, good housekeeping can be an indication of the quality of the lab. Look for a well-maintained lab and the lab results will usually reflect a high-quality lab.
A testing lab should read the next Technical Requirement as Test Methods and Method Validation. (Again, calibration labs would read the requirement as Calibration Methods and Method Validation). It is important to ask the lab about their Scope of Test Methods. How many tests do they have the capability to run?
The test methods should be documented including frequency ranges and amplitudes of various tests. The testing lab should have a verification process for each test method so that the lab knows the test equipment is operating properly for the test on the customers product. This verification is a system check that assures the EMC Test equipment and the corresponding test method are both in synchronization. This verification process can be combined with intermediate checks and daily checks of test equipment to assure a repeatable and reproducible test of the customers products.
Equipment for EMC testing labs is expensive especially for large semi-anechoic (SAC) and fully-anechoic chambers (FAC). As a potential user of the EMC lab, you may want to ask for a list of the labs EMC test equipment as well as a description of the labs test facilities. Once you arrive at the lab, you should double-check the calibration status of the labs test equipment. Each piece of equipment that is being used for the testing should have a calibration tag on it with a current in-calibration status indicated on the tag. High-quality test equipment will help assure a high-quality testing experience.
The next technical criterion for an ISO/IEC 17025 accredited lab is Measurement Traceability which is closely associated with the labs test equipment. A calibrated piece of test equipment has to be traceable to the International system of Units through a direct path to a National Metrology Institute. In the United States, the National Metrology Institute is the National Institute of Standard and Technology (NIST). The best way to do this is to assure that the calibration labs used by the testing lab are accredited to ISO/IEC 17025. This assures that the calibration labs measurement standards and measurement instruments are linked to relevant primary standards through an unbroken chain of calibrations.
Sampling is an important aspect of the technical characteristics of a testing lab. However, for most independent testing labs they will test products brought to the lab not knowing what sampling plan, if any, was followed by the customer in selecting the product to be tested. Internal EMC labs sometimes have more input to a sampling plan of manufactured products and their selection for occasional testing of their companys manufactured products.
Handling of Test Items is the eighth technical requirement of the ISO/IEC 17025 standard. This deals with how test items are delivered to the EMC lab for testing; are they hand-carried, delivered by a company truck, delivered by a common carrier such as UPS, Federal Express, etc. This topic also covers identity of the products while they are in the lab, security and confidentiality of the products while they are in the lab, and, finally, the shipment of the test items back to the customer.
Assuring the quality of test results is usually combined with intermediate checks and daily checks. The EMC lab may also participate in inter-lab proficiency testing and other techniques for checking and verifying the quality of the labs test results.
The last part of the Technical Requirements is the Test Report or as ISO/IEC 17025 refers to it: Reporting the Results. A prospective user of a test lab should ask to see a test report template for the lab. The test report should comply with the requirements of Clause 5.10 (Reporting the Results) of ISO/IEC 17025.
Summary
Look for laboratory accreditation to ISO/IEC 17025 as a first step in finding a high-quality EMC testing lab. However, it should be noted that even accredited testing labs can make mistakes.
It is important to check the scope of tests for an accredited lab to make sure the scope of tests encompasses the tests required for the customers product.
An accredited lab that is qualified to perform the necessary scope of tests will provide the customer a complete test report that will ease the acceptance of the product in national and international markets.
In general, you will be satisfied with accredited EMC labs because there is a higher probability of a successful test using calibrated and high-quality test equipment. This should allow easy marketing of your product relative to EMC requirements. 
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Daniel D. Hoolihan is the Founder and Principal of Hoolihan EMC Consulting. He is Chair of the ANSI-ASC C63 Committee on EMC. He is a Past-President of the EMC Society of the IEEE and is presently serving on the Board of Directors. He is presently an assessor for the NIST NVLAP EMC and Telecom Lab Accreditation program. For further information, contact Dan at danhoolihanemc@aol.com or 651-213-0966. |
