Prediction is indeed possible for ceratin classes of products. Sometimes they can be based on comparison with previously maesured products, sometimes it can be a straightforward prediction - e.g. based on CM current on voltages measurements at the cable-interface. The more you know your product, the better chances are you'd be able to predict based on quick measurements. It is not possible to predict always, but certainly there are methods of efficiently using the bench as opposed to going to a chamber every time one wants to know what impact a modification has or to eyeball the emission perfomance of a product. Elaborating more within this media is not possible. Check current clamps, near-field probes, passive contact probes, and if you are specifically interested in predicting emission from differential-pair interfaces, I have done significant amount of work etablishing the correlation between radiated emisison and common-mode voltage on the diff pairs (specificalyy of Ethernet devices, but it is more generally applicable). Published in Seattle EMC Symposium or search for "Common mode voltage probe" Neven
-------------- Original message -------------- Robert, Predicition sounds to me like clairvoyance - not very common to EMC :-) My opinion on this is: Rather than trying to predict the quantitative EMC impact of a modification, it is preferrable to understand if a certain modification could have an impact and which. Example: Changing the supplier of a resistor is uncritical as long as this type of resistor is used as a pullup on a quasi-static signal (e.g. reset), it may become critical if it is used in the signal path of a RF circuit. When changes are evaluated under a design point of view, it is easier to figure out _what_ ils likely to happen. There is no 100% security, unfortunately. When it comes to IC manufacturers, you may have the situation that components behave differently in function of their date code and the manufacturer did not announce any mask change (we had this). In a few words: I do not see a simple way of predicton, but by using the knowlegde of the involved designers and EMC engineers with the help of a well implemented process (documentation helps a lot in this case) it becomes easier to concentrate on the real issues. Implementing some sort of "risk rating" can help to priorize the different tasks. If GTEM cells would be an option for you - a test can be done quickly compared to other methods. Best regards, Michael Michael Nagel Senior EMC Engineer Motorola Embedded Communications Computing Group Lilienthalstrasse 15 D-85579 Neubiberg/Muenchen - Germany Ph: +49-89-60814-0 Fax: +49-89-60814-376 e-mail: [email protected] Speaking for me. From: [email protected] [mailto:[email protected]] Sent: Montag, 13. Dezember 2004 13:31 To: [email protected] Subject: Simple EMC Prediction Good Morning EMC Gurus, We have the constant issue here in our lab of test time vs. resources. Often we are proposing different design changes for various reasons (cost savings, new supplier because of discontinued component etc.) This deals with existing products that can be updated for various reasons. The problem is we have a hard enough time keeping up with our new business/projects that require full validations. In most cases failures occur and solutions must be implemented to sell the products to the customer. In the case of a current production product often design changes are proposed but of course some sort of validation must be performed before making this design change. The design change can consist of electronic components, material change, and mechanical changes. My question is if anyone else has a similar issue in their lab and what kind of tools can be used as a quick and efficient "filter" to either proceed with a full boat of testing or eliminating the idea and moving on to something else. The most common problem is most design changes require Radiated Emissions testing. With only one Anechoic Chamber and the length of the test this is hard to deal with. Any ideas besides knowledge of a quick and simple test we can use to perform this type of filtering? Our products are automotive so in some cases we are talking PCB level but in most we! are talking about various dc motors. Of course we have the know ledge but as you all know in the EMC world that is far >from the final say all. I would be interested in all responses. Thank you. Rob Kado EMC Engineer VWS - Auburn Hills, USA Tel: 248-340-3828 / Fax: 248-340-3316 Internal Location 3M2 ----------------- ---------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
