Every person working in the EMC field has their own techniques when dealing will emissions issues. Mostly based on past experiences, product type, what tools they have handy or can afford plus the political atmosphere where they work.
I am no exception, part of my list of tools include: EMCO 3142B antenna Fischer Custom Communications current clamp F-130B frequency range 100kHz - 1GHz. EMCO 7405 Probe set And a CASSPER "ETS Model 2000 Virtual Chamber" Lots of small hand built probes For me the political atmosphere is time to market and then the cost of the fix, so any tool that speeds up troubleshooting and gives more options is easy to justify. The CASSPER system is mostly billed as an ambient cancellation system, which it does fairly well "up to 30dB" for external outside the building noise. For internal noise in the room/building that you are using it in it has no effect. I vary seldom use this part of the system. Personally I think they are not advertising correctly. The source localization capabilities of the unit are amazing. For reasons unknown the design engineers where I work with like using 4MHz, 12MHz and 24MHz clocks to run the different processors in our systems; talk about stack-up. I think they're punishing me for transgressions in a past life. Our typical test methodology for testing the EUT is to take it to our favorite 10m chamber if it fails, "it does happen once and awhile", we take it back to our lab and troubleshoot it. I can go from looking at the signal with the CASSPER with the 3142B antenna on channel 1 and current clamp on channel 2 using the source localization mode and find the radiating element, "typically a cable". Then switching the current clamp, now clamped on the radiating element to channel 1 and a near field probe on channel 2 I can find the trace and driver circuit which is the source of the emissions. Total time under 10 minutes usually. Solutions about what to do about it sometimes take a bit longer, but now I know the driver, path and radiating element. I can now choose how to attack the issue to bring product into compliance; driver, path or radiating element. I once built a test bed with dithering clocks operating at 24MHz then mixed them together with one of the clock signals having a 10dB attenuator in line with it. The system used an inductively coupled loop antenna to guarantee that it would radiate. Even with the same percentage of dithering I could tell the dithering clocks apart. Like any other tool it has its quirks and limitations that have to be learned but it does the job. It is not however inexpensive. William Morse NCE -----Original Message----- From: [email protected] [mailto:[email protected]] Sent: Tuesday, August 20, 2002 1:35 PM To: [email protected] Subject: Emissions "quick test" Hi all, Does anyone know of a " down- and- dirty" , inexpensive method or equipment for sniffing out emissions issues? I've used a Spectrum Analyzer in the past with a series of different probes, but that tends to be costly. Also, Is there a "universal" probe kit out there? Thank you in advance. Lisa Lisa A. Cefalo, CRE Manager, Reliability and Design Services MKS Instruments 6 Shattuck Road Andover, MA 01810 (978)-975-2350 X 5669 [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [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://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
