Bob, I usually look for anything that is cyclic regarding the product. Regardless of the duration. For instance, many moons ago, I ran across a hard drive that would seek home once every three minutes. At that time the servo motor in the hard drive would cause an emissions failure. Because it was cyclic and wasn't isolated I classified that as a failure.
With electro-mechanical devices broad band emissions are not uncommon. Based on many factors, the broad band may have been a random occurrence or cyclic in nature. With this I look at the operating environment: is the RH outside the product specification or is the product grounded properly. However, If a charge is continually being built up on moving parts and discharging causing emissions failure, I would classify that as a problem. With data transfer over I/O you can also see issues that seem random. It's usually a matter of peeling back a layer to see what is causing the problem. As with most EMC issues if you can't repeat the failure, you're hard pressed to classify it as such. My 2 cents..... Dave Spencer EMC Engineer Xerox Corp. From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Wednesday, February 11, 2009 11:07 AM To: [email protected] Subject: Brief and Isolated In Clause 6.1 of EN55022:2006 A1:2007 it states: "The EUT shall meet the limits of Table 5 or Table 6 when measured at the measuring distance R in accordance with the methods described in Clause 10. If the reading on the measuring receiver shows fluctuations close to the limit, the reading shall be observed for at least 15 s at each measurement frequency; the highest reading shall be recorded, with the exception of any brief isolated high reading, which shall be ignored." Does anyone know what "brief isolated" could mean or am I left to my own to devices to define it as I see fit? Bob Heller 3M EMC Laboratory, 76-1-01 St. Paul, MN 55107-1208 Tel: 651- 778-6336 Fax: 651-778-6252 - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/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]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/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]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
