A possible point of clarification, step "e" does not say what the +/- 3 dB is referenced to. I assumed it was of the mean, though it does not explicitly say that. Thoughts?
Best regards, Don Umbdenstock > ---------- > From: UMBDENSTOCK, DON > Sent: Friday, May 17, 2002 11:38 AM > To: 'EMC Forum' > Subject: Compact Chamber Calibration > > Hi All, > > I read the standard EN 61000-4-3:1996 with amendments to gather a deeper > understanding of the requirement and the procedure. It appears the > procedure is at odds with the requirement. Please allow me to explain. > > The requirement is to establish 75% of the field points to be within -0 dB > to +6 dB. Exploring the uniformity by means of constant field strength > invokes Clause 6.2 a, d, e, f, and h. I have trouble with clause e. > > Paraphrasing for simplicity, > > - take the data > - find the mean in V/m > - throw out the worst 25% > - the remaining points shall lie within +/-3 dB > - use the lowest of the remaining points as reference. > > The 4th step does not make sense to me. I can still maintain a -0, +6 dB > spread without invoking a +/- 3 dB window about the median. > > As an illustration, suppose I have data that establishes a spread from -15 > dB to +4 dB about the mean. My worst 4 points are -15, -14, -13, -12 dB. > So these points are clearly further from the mean than +4 dB and are > deleted. The remaining points are clustered between +1 and +4 dB. Step > "e" says the remaining points shall remain within +/- 3 dB, so the point > at +4 dB is considered non-compliant, even though it is only 3 dB away > from the lowest point. Step "f" says to make the lowest point the > reference for -0, +6 dB. This being the case, my non-compliant point, > originally identified as +4 dB from the mean is now well within the -0, +6 > dB range of the reference, but is considered non-compliant. > > I realize the standard allows up to 3% of points to fall between +6 and > +10 dB, but that is not the issue. This point should not have been > identified as non-compliant in the first place, but clause "e" requires it > to be identified as non-compliant. > > Does anyone know the rationale to clause "e"? What am I missing? Are > there any committee members out there who can shed some light on this? > > Kind regards, > > Don Umbdenstock > TEPG -- Sensormatic > 561 912 6440 > ------------------------------------------- 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"
