While it has absolutely nothing to do with compliance measurements, I like to have the phase response of my two single wire LISNs match as close as possible as I use 0 degree and 180 degree combiners for CM/DM discrimination and filter design.
Brent DeWitt Framingham, MA > -----Original Message----- > From: [email protected] [mailto:[email protected]] > Sent: Tuesday, April 19, 2011 5:36 PM > To: [email protected] > Subject: Re: [PSES] LISN Phase angle, why? > > I suppose the correct measurements-based answer is to preserve the > proper > impulse response. After all, the makers of EMI receivers go through > some > trouble to make sure that the IF filters they use are within certain > specified limits for both impulse bandwidth and group delay. Using a > LISN > with weird phase characteristics could mess up measurements where you > have > multiple correlated sidebands/harmonics inside the measurement > bandwidth. > > Having said that, at least for my (pre-compliance) measurements (150 > kHz - > 30 MHz using 9 kHz IF bandwidth), I think it hardly matters. All I am > seeing are harmonics of the switching power supply frequency, which > around > here are designed to place the fundamental frequency somewhere around > 125 > kHz. With this wide spacing of harmonics relative to the measurement > bandwidth, phase and impulse bandwidth don't matter too much. I say > 'not > too much' because I do see 120 Hz modulation of the lower order > harmonics > as the diodes of the input bridge rectifier turn on and off (I deal > almost > exclusively with low wattage switchers for use in industrial > environments, > thus no harmonic/power factor correction). So there are the 120 Hz > modulation sidebands, and the exact impulse bandwidth and phase > probably > do make some difference. Even then I wonder how much they matter when I > turn on the average and quasi-peak detectors, as opposed to what I see > when I do the initial peak measurement. > > Don Borowski > EMC Engineer > Schweitzer Engineering Labs > Pullman, WA, USA > > > > From: [email protected] > To: Derek Walton <[email protected]> > Cc: [email protected] > Date: 04/18/2011 03:20 PM > Subject: Re: [PSES] LISN Phase angle > Sent by: [email protected] > > > > > I wonder why the committee thought that was all important? I would > have > kept it simple and asked for an ampl-freq response check, because > I think that accomplishes the same thing. > _______________________________________________________________________ > ______________ > > > Ralph McDiarmid | Schneider Electric | Renewable Energies > Business | > CANADA | Regulatory Engineer > > > From: > Derek Walton <[email protected]> > To: > [email protected] > Date: > 04/18/2011 01:03 PM > Subject: > [PSES] LISN Phase angle > > > > > Hi All, > > I understand that it is now important we measure LISN phase as well as > impedance. Can anyone point me to the document requiring that please. > > Thanks, > > Derek Walton > L F Research > > - > ---------------------------------------------------------------- > 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://product-compliance.oc.ieee.org/ > 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://product-compliance.oc.ieee.org/ 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]>
