I believe that selecting the right combination of ferrites once, by testing them to provide at least 15 dB S21 should do it. Then it should be a matter of keeping it documented and used in a test-procedure, to ensure that every time one uses the same arrangement.
Regrading the proposal that it must provide at least 15 dB attenuation AND 150 Ohm input impedance at the same time, that sounds somewhat trickier. Neven > > Chris, > > You can indeed make your own, but my bet is that A2LA or NIST NVLAP > inspectors will want to see calibration data, not calculations. > > Now, if we just had a published calibration technique... > > Ghery > > -----Original Message----- > From: Chris Maxwell [mailto:[email protected]] > Sent: Wednesday, January 29, 2003 10:57 AM > To: Pettit, Ghery; [email protected]; [email protected] > Subject: RE: EN55022:1998 + A1:2000 > > > Ghery, > > If the standard is assuming a 50 Ohm system, doesn't this breakdown to a > simple calculation? > > Insertion Loss = IL = 20 x log((50 + Zf) / 50)----where Zf is the ferrite > impedance > > This could easily be solved for Zf if you assume IL to be 15dB (in this > case the dB are truely dimensionless; as you are calculating a pure loss > from an arbitrary level). > > I would think that you would just have to: > > 1. Solve the above for Zf. By the way, I get 231.2 Ohms. Can someone > check this? > > 2. Gather up a box of "doughnuts" such that the total Zf is above the > answer for step 1 at all frequencies from 30Mhz to 1Ghz > > 3. Color code the doughnuts (or whatever) and write a procedure that says > something like "clamp three blue doughnuts and two red doughnuts over each > cable ..." > > Have I over simplified this??? Wouldn't this be proof enough for any > accreditation body? I know that $300 may not seem like alot to some; but it > adds up after a few cables. Besides; we went to college to learn all of > that math; why not use some of it? I don't mind paying for stuff that I > can't make; but this one seems possible to me. > > Chris Maxwell | Design Engineer - Optical Division > email [email protected] | dir +1 315 266 5128 | fax +1 315 797 8024 > > NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA > web www.nettest.com | tel +1 315 797 4449 | > > > > > > > > > > > -----Original Message----- > > From: Pettit, Ghery [SMTP:[email protected]] > > Sent: Wednesday, January 29, 2003 11:59 AM > > To: '[email protected]'; [email protected] > > Subject: RE: EN55022:1998 + A1:2000 > > > > > > Amendment 1 to CISPR 22:1997 (Amendment A1:2000 to EN 55022:1998) requires > > that the clamps provide at least 15 dB of loss in a 50 ohm system over the > > frequency range of 30 MHz to 1000 MHz. The use of extension cords is > > prohibited. Can you guarantee that your bucket of doughnuts will meet > this > > requirement? How will you demonstrate that to your lab's accrediting > body? > > > > > > Fischer's clamps are around $300 each. Compared with what we had to > choose > > from prior to their product, these are not big bucks. > > > > Ghery Pettit > > Intel > > > > > > > > > > ------------------------------------------- > 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] > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc 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] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
