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. 

How To Acquire Accurate & Efficient EMC Lab Equipment

Tom Klouda, Elite VP

Tom Klouda, local lightning expert and EMC equipment extraordinaire, tells us what it takes to obtain quality EMC laboratory test equipment that accurately and efficiently tests our customers' products.

Electromagnetic Compatibility (EMC) tests require the use of specialized and costly pieces of electronic equipment.  The electronic equipment must perform the measurements accurately and efficiently.  A process used to acquire equipment at Elite Electronic Engineering, Inc. that has been successful is a collaborative effort between Elite, our customers and the equipment manufacturers.

The process starts by identifying a need for the equipment.  The need can be identified from schedule bottle necks, missed opportunities, operation safety concerns or functionality.  Once the need is identified, various manufacturers of the test equipment are researched. In our research we consider the equipment’s features, cost, warranties and service.  Often, equipment on the market does not have the required features to meet our customer’s needs. This situation is where Elite’s personnel provide valuable insights.  Our customers and equipment manufacturers know everything about the design of their equipment. 

However, Elite is in the unique position of knowing how to test our customer’s equipment and how to use the manufacturer’s test equipment.  Knowing our customer’s need, Elite’s personnel work closely with the manufacturer to design equipment that accurately and efficiently performs the tests. This collaborative relationship has benefited everyone involved.  The EMC test industry also benefits because now the equipment Elite helped to design is available to everyone.      

Tom conducting an internal equipment training session in August.

Do you have any questions about choosing EMC Test Equipment, Lightning Testing, or other related topics? Please share your comments or questions below and this week's expert, Tom Klouda, will get back to you as soon as possible.