Sorry for the pedantry, but a failure with respect to a logarithmic limit is given in dB, not dB with respect to the measurement unit. The failure is specified as a ratio relative to the limit. The measurement uncertainty is +/- 3 dB, not dBuV, and the outage is 0.5 dB above the limit, not 0.5 dBuV above the limit. If the outage really were 0.5 dBuV above the limit, that would TRULY be within the measurement tolerance of any rf equipment!
IMO, if you are out, you are out. You cannot use measurement tolerances to rationalize an above limit condition. If you claim you are within measurement tolerances, I can postulate that your measurement system is measuring 2.9 dB low, so that a 0.5 dB above limit reading could actually be 3.4 dB above the limit, putting you outside the tolerance band. Since you are very close, it would be nice to nail down just how accurate your measurement is. Depending on how good quality your measurement equipment is, I could see injecting a known signal at the spec level at the outage frequency into the LISN and seeing how your measurement system reads it. If it reads enough off that it affects your pass/fail status, then it is worthwhile to troubleshoot your test set up. MIL-STD-461E has detailed procedures for doing this. > From: Dave Grant <da...@alisonlabs.com> > Reply-To: Dave Grant <da...@alisonlabs.com> > Date: Fri, 31 Oct 2003 14:01:33 +1300 > To: <emc-p...@majordomo.ieee.org> > Subject: Window of Uncertainty > > > > > > > Hello all, > > We have been doing development of our product here and have been testing > the conducted emissions with respect to CISPR 14.1. > > There is a window of uncertainty of +/- 3dBuV with respect to this test? > > The testing here that has taken place so far shows that the product fails > by 0.5 dBuV at a certain frequency. > > My question is, is this an Assumed Pass as this fall within the Window of > Uncertainty? > > or > > Is any measurement above the limit irrespective of the uncertainty error a > fail? > > > This is with for the European, Australasian and American markets. > > Cheers ... > Dave > > > ------------------------------------------- > 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: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: emc_p...@symbol.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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
