What Every Electronics Engineer Needs to Know About: Working with EMC Test Labs

Introduction

Choosing an EMC test lab to work with is one of the most important decisions any electronics design engineer or product developer has to make. Selecting the wrong EMC test lab could mean non-acceptance of test reports, incorrectly performed tests and associated added rework, inability to sell product into specific countries, late product launches, excessive test budgets, added liability, added overhead and other headaches that are usually associated with inefficient test and certification processes. With this background in mind, this article will quickly highlight what every engineer can do in order to ensure they select the best EMC test lab to work with.

Pre-compliance Testing

Before we get started, here is a quick note about the importance of performing pre-compliance testing early in the product development cycle. Taking your product out to a third-party test facility is expensive and time-consuming. Often times it is the last step in the product development process to occur before production units can ship. Now is not the time to find out your product fails radiated emissions or some other EMC test. In order to solve EMI problems during this late stage of the product development program, the available techniques are few and relative costs of them are high. Think about going to the EMC test lab to pass, not to fail. This means performing some kind of pre-compliance testing very early in the program to ensure a higher probability of passing formal EMC qualification tests when the time comes. Setting up an internal pre-compliance testing capability is not that hard or expensive. There are several resources available out there which can get you pointed in the right direction and reference #1 described at the end of this article is one that is highly recommended.

Accreditation

Determine if you need to use an accredited EMC test lab. Sometimes this will be driven by your customer and other times by the type of approval you need in order to ship your product legally. For instance, under the Code of Federal Regulations, Title 47, Chapter I, Subchapter A, Part 2, Subpart J, Section 2.948, the FCC requires that equipment authorized under the certification procedure be tested at an FCC-recognized accredited testing laboratory with the appropriate scope of accreditation (meaning the tests you need performed are included on the lab’s scope of accreditation). For equipment authorized using the Supplier’s Declaration of Conformity (SDoC) procedure, it is not necessary to perform the testing at an FCC-recognized accredited testing laboratory if that is the route you need to take; however, an accredited testing laboratory may be used if desired. Be sure to check if accreditation is required and, if so, that the EMC test lab is properly accredited. A list of FCC-recognized accredited testing laboratories is provided on the FCC website at: https://apps.fcc.gov/oetcf/eas/reports/TestFirmSearch.cfm.

Take note that just because a test lab is accredited does not necessarily mean they are going to be perfect EMC test solution providers. It’s not that accreditation is meaningless, it does establish that a test lab has met certain credentials and qualifications, but it doesn’t make it clear whether or not any particular test lab will be a good fit for you and your particular EMC testing needs.

Overall Considerations

Some other important items to consider when selecting an EMC test lab to work with include things like turnaround times for reports, technical expertise, cost, layout of the facilities and accommodations, responsiveness to request for quotes, and thoroughness of quotes.

Look for other services the test lab may be able to provide that may also save you time and money such as their ability to act as an FCC telecommunication certification body (TCB) for the U.S. or as a Notified Body for the European Union’s EMC Directive, should you require those services.

Perhaps you want to also perform other non-EMC tests like environmental, enclosure protection testing (IP Code), salt fog, safety, vibration, etc. at their facility instead of sending your device out to many laboratories. Just be sure the test lab can perform these other tests as well as they can their EMC tests.

It might be a good idea to visit the test lab and perform a mini quality audit. Ask about their typical test report turnaround times. Good labs should be able to have a test report back to you in less than two weeks. I have seen test reports completed as fast as a few hours and as long as a few months!

The test lab should have experts on staff who can help diagnose and suggest design improvements should the product fail testing. Make sure you’re not just getting button pushers who do not thoroughly understand the purpose of the test and what to look for if test anomalies arise. A good EMC test technician or engineer will be able to quickly recognize when something goes wrong with a test and when to take appropriate action. A person trained to just push buttons won’t be able to recognize a difference between a good and a bad test and over or under testing. A quality check should be performed prior to the start of any test to confirm test equipment is operating correctly and the test setup is sound. This is a very important step in the test process. While you’re there, ask if they have ever had to repeat testing because they found out later that it was performed incorrectly. You can ask for training records to see how properly trained their staff is.

Look at their facilities and see if it is well-organized or cluttered. If it’s a cluttered environment, most likely they are disorganized and you will have to spend extra effort managing the test lab and your device as it goes through testing.

Check equipment calibration certificates. If they are an accredited lab, the equipment calibration certificates should be up-to-date and come from accredited calibration service providers as well.

Some test labs sub-contract out some of their testing to other test labs. Be sure to ask about this if it is important to you. You don’t want to show up at one location expecting to run all tests in that one location only to find out you need to visit some other facility in order to witness all tests. This will especially be the case if you ask the lab to perform other types of tests besides just EMC.

Ask to see how they capture customer complaints and take a look at a few of them. See if they have implemented actions to correct any deficiencies. They should have a process for handling customer complaints.

Finally, if your equipment under test has unique power, size, filter, or other non-standard requirements, make sure the test lab can accommodate these unique needs. There is nothing worse than going through the entire quoting and scheduling process only to find out on the day of planned testing that the test lab does not have the correct accommodations to properly test your device. When all else fails, remember the quote from Benjamin Franklin that “An ounce of planning is worth a pound of cure.”

References

  1. Ott, H., Electromagnetic Compatibility Engineering, John Wiley& Sons, 2009.
  2. Eadie, A., How to Choose the Best EMC Test Lab, https://emcfastpass.com/emc-testing-beginners-guide/emc-test-lab-guide/
  3. Hoolihan, D. EMC Lab Selection – Revisited, https://incompliancemag.com/article/emc-lab-selection-revisited/

 

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