Regarding this: "I don't think we are testing efficiency of cable pick-up. I think we are testing immunity to whatever is picked up regardless of cable efficiency."
I feel like Mr. Spock: "That is illogical." A field impinges upon a cable. An rf potential/current is coupled to that cable. That coupled potential is a function of electrical length. The immunity of the test sample to the coupled potential is then assessed. The efficiency of the coupling, or the transfer function, has to be accounted for. The specific transfer function follows sin (2 p l/l) In case the symbols don't come through, that is sin (2*pi*cable length/wavelength) The RTCA/DO-160D/E and MIL-STD-461D/E conducted immunity limits follow this equation asymptotically, using the peaks as the limit; the 1000-4-6 approach was a fixed limit with a low frequency truncation. From: Bill Owsley <[email protected]> List-Post: [email protected] Date: Mon, 26 Feb 2007 09:16:25 -0800 (PST) To: Ken Javor <[email protected]>, [email protected] Subject: Re: Conducted immunity lower frequency I don't think we are testing efficiency of cable pick-up. I think we are testing immunity to whatever is picked up regardless of cable efficiency. If cable length and thus efficiency determined the lower cutoff frequency, what is the formula to make a determination? Is it a half wave, quarter wave, 1/5, 1/6, 1/10, 1/20 ? to use some of the various "rules of thumb" for relative efficiency. - Bill Ken Javor <[email protected]> wrote: I disagree with what I perceive is being stated here - that if any portion of a system has a connection to a long conductor, then all system-attached cables must be tested down to 150 kHz. The purpose of the Annex B wording is to allow for basic physics to be applied to the limit - short cables are inefficient pick-up at low frequencies. It is the length of the individual cable-under-test which should drive the low-frequency cut-off limit. Ken Javor > From: "Oliver Betz" > Date: Mon, 26 Feb 2007 11:30:21 +0100 > To: [email protected] > Subject: Re: Conducted immunity lower frequency > > Bob Richards wrote: > >> Twice recently I've seen where annex B of 61000-4-6 ed2.2 is >> referenced by someone and used as a reason for not requiring testing >> down to 150 kHz "since the cable is specified as being less than x >> meters in length". (Of course, this is after the EUT failed at a low >> frequency!) > > Was Annex B applied correctly? Only very special setups are subject > to higher starting frequencies, e.g. the keyboard attached to a > battery powered PC, never used with AC adaptor. > > Most devices are galvanically coupled to sources of low frequency > disturbances, in this case the starting frequency must not be raised. > > I read this from Annex B and it makes sense. > > Oliver > -- > Oliver Betz, Muenchen > > - > ---------------------------------------------------------------- > 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/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] > > 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. 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