Why Are Uncertainty Budgets Necessary?

Fanning, EMC Lab Manger

Today, Elite's EMC Lab Manager Craig Fanning gives us a few reasons why uncertainty budgets are worth the work to ensure proper CISPR 16 compliance.  Find out the other benefits he lists in this week's blog.

Uncertainty budgets…why??? I hear a lot of people in the EMC industry complain that uncertainty budgets are painful and not necessarily worth the time expended. That is a little bit understandable since we go through all the work to generate uncertainty budgets but don’t generally use them during everyday measurements. However, uncertainty budgets are necessary and can be pretty good tools for the laboratory.

CISPR 16 Compliant Measurements - Uncertainty budgets must be done for CISPR 16 compliant measurements. If the uncertainty budget of the laboratory meets the U_cispr values shown in Table 1 of CISPR 16-4-2, then no correction of the data is needed to determine EUT compliance. If the uncertainty budget of the laboratory does not meet the U_CISPR values shown in Table 1 of CISPR 16-4-2, then the measurement must be adjusted by the difference (U_lab - U_cispr) to determine if an EUT complies with the standard.

EMC Lab Personnel Training - Uncertainty budgets make the laboratory realize how good (or not so good) their measurements really are. We all need to have a good understanding of how the various parts of the test system contribute to uncertainty. We also need to know how measurement uncertainty can be reduced by purchasing higher quality (lower uncertainty) equipment. If the lab management and personnel understand the contributing factors, then the lab can do a better job at reducing measurement uncertainty (providing a better service to their customers).

Customer Education and/or Lab Differentiation - Many years ago a customer told me that he wanted a 200V/m radiated immunity test “no more no less” says the customer. The young electrical engineer did not realize that a radiated immunity test is not accurate to within 0.1 V/m (although the measurement instrument tells us so). Customers also wonder why a radiated emissions measurement made in one chamber is slightly different (a couple of dB) from a measurement made in another chamber. The people who make EMC measurements everyday (and understand measurement uncertainty) know that this is pretty good chamber-to-chamber or lab-to-lab repeatability. When you can show a customer how the accuracy of all parts of the system contribute to measurement uncertainty and that your uncertainty is better than the “standard” (or another lab), then that helps to educate the customer and differentiate your laboratory from the competition.

So the next time you have to work on uncertainty budgets, don’t think about how painful they are. Think about how they can be beneficial to your lab, personnel, and business. This will make the time (and money) expended more palatable.

Do you have any questions about EMC Lab Management, EMC Standard Changes, or other related topics? Please share your comments or questions below and this week's expert, Craig Fanning, will get back to you as soon as possible. 

Automotive Standards Development 2014 Recap

Today, Elite's EMC Lab Manager Craig Fanning fills us in on what's been brewing in Automotive and Military standards so far this year. As a featured speaker at this year's ROACH Conference in Seattle, he presented a “Review of Automotive Standards Utilizing Reverberation” and participated in the “Emerging Technologies in EMI/EMC testing” panel discussion.  He also attended several other meeting concerning EMC standards this spring and was kind enough to pass along some notes and a couple snapshots  Read below to see what he has for us this week.

Automotive standards development at the North American and International levels continues to be hectic in 2014. The SAE EMC committees had a meeting in January of 2014 and will be having another in April. At the international level, CISPR/D WG1, CISPR/D WG2 and ISO/TC22/SC3/WG3 had their first of two meetings scheduled for 2014 in February. 

 

Craig at the IEEE EMC Society Seattle sponsored ROACH meeting

Experts from eight countries convened at the ETS Lindgren facility in Cedar Park, Texas to continue work on the CISPR 12, CISPR 25, ISO 11451-xx, ISO 11452-xx, and ISO 7637-x standards. ETS Lindgren was kind enough to host the meetings per the request of the CISPR and ISO USTAG Delegates. The meetings were a great success and a lot of progress was made towards next revisions of the subject standards. The CISPR/D and ISO committees greatly appreciated the support of ETS Lindgren and their staff again for the meetings. The next international level meetings for these standards groups will be held in Frankfurt, Germany in October 2014.

  

The  Chapter hosted the Reverberation Chamber, Open Area Test Site and Anechoic Chamber (ROACH) Users Group meeting in Seattle, Washington in March 2014. The ROACH meetings are a “think tank” for key players in the EMC industry. Standards updates and new technologies regarding reverberation chamber, anechoic chamber and TEM cell testing were presented. This meeting drew experts from around the world. The experts were there to make presentations and were also available for sidebar discussions. This meeting was a great opportunity for people in the EMC industry to talk “shop” with others in the industry. Pat Hall and I had a great time both during and after the formal meetings. Take a look at that pile of Pacific coast seafood… 

Pacific Seafood Feast for the Sake of Science!

Do you have any questions about EMC Standard Changes, Testing in Reverberation Chambers, or other related topics? Please share your comments or questions below and this week's expert, Craig Fanning, will get back to you as soon as possible.

Why SAE EMC Standards Are Being Withdrawn

Craig Fanning, EMC Lab Manager

Today's Elite Expert is Craig Fanning. Our EMC Lab Manager since 1995, Craig has overseen scores of test projects over the past 27 years with the company. He is also an iNARTE Certified EMC Laboratory Engineer and author of several papers for the IEEE EMC Symposium.  Finally, as a member of SAE EMI and EMR Committees, as well as a US National Committee technical advisor for CISPR-D, he undoubtedly likes to stay active in the EMC community. Read below to see what he has for us this week.

Users of SAE EMC standards may have noticed that many of the SAE J551 and SAE J1113 standards have been withdrawn over the past few years. These withdrawn standards are no longer being revised and updated. As these standards are withdrawn, the base standard of the series (SAE J551-1 or SAE J1113-1) is updated to indicate that the particular SAE standard has been withdrawn. The base SAE standard also directs the user to reference the equivalent CISPR or ISO standard. Unfortunately this results in having to purchase the more expensive international standard which replaced the SAE standard.

So, why are the SAE EMC standards being withdrawn???  A few years ago, SAE noticed that some of the SAE EMC standards were, for the most part, technically identical to some equivalent CISPR and ISO (international) standards.  This became a concern of SAE as they do not want to get into copyright conflicts with the international standards bodies. Therefore, the SAE EMC committee was given the directive to start withdrawing any SAE standards which were technically identical to an international standard.
 

How did this similarity of SAE and International standards come to happen??? The SAE EMC committee has developed many vehicle and component EMC standards over the years. The SAE standards were referenced mainly by the North American vehicle manufacturers in their corporate EMC standards. As the NA vehicle manufacturers evolved to Worldwide vehicle manufacturers, the trend to reference SAE standards in their corporate standard changed to the desire to reference international standards (if they existed) in their corporate standards.

Many of the same experts involved in the SAE EMC committee in the United States are also involved with at the International Standards development level (CISPR and ISO standards). During meetings at the international level, the need to develop a standard to address a particular field issue may be discussed. If an SAE standard which addressed the issue already existed, then the international standards committee would use the SAE standard as the basis for development of a new CISPR or ISO standard. Although the process to publish the international standard would take several years, the two standards (SAE and International) would eventually become very similar.

What is the long term benefit of using international standards over the SAE standards??? Although it may seem like a burden to purchase a more expensive CISPR or ISO standard, the use of the international standards does have its benefits. The test methods used to evaluate the EMC performance of vehicles (and vehicle modules) should be similar around the world to assure consistent performance. Products initially developed for sale in the North American market may also be more easily marketed worldwide when tested against the international standards.  

Ultimately, standardization helps to assure consistent performance and reliability no matter where the product is being used. By using international standards to evaluate the EMC performance of products (when available), this will help the product manufacturers to better achieve the consistent performance and reliability desired by the consumer. 

Do you have any questions about EMC Standard Changes, EMC Testing, or other related topics? Please share your comments or questions below and this week's expert, Craig Fanning, will get back to you as soon as possible.