Re: [PSES] FCC Part B questions

[Lfresearch]

Patrick, Put me down as an MU abolitionist.  I don’t see it adding any value, just workload and cost.  I’d like to see it gone completely  Yes I know others don’t agree, such is life.  Derek  Sent from my iPhone On Jul 14, 2023, at 3:30 AM, Patrick <conwa...@gmail.com> wrote:  I've been busy last couple of days and only now seeing the additional convo around measurement uncertainty(MU).   I like the comments.  Most folks appear to be either agnostic or in support of MU for use as a quality and confidence builder.  I notice there are no MU-deniers?? Ok, I'll break the ice..., I think MU is a waste.  It wastes a labs (and engineers) most precious resource: time.   I also cannot think of a single customer, internal or external, that was ever willing to pay for this metric.  If your experience is different, hit reply-all with an anecdote. Here's an idea:  If customers are willing to pay, then wouldn't they also be willing to pay for any upgrade? Would they pay for a better MU for their product test? Maybe a lab can offer two levels of MU service?  Similar to a how a lab offers Data Report(lower cost) vs Accredited Formal Report(full cost)?  Maybe call it... 'Certified GMO & MU-free test data'?  Hmm, I should trademark that idea. Another thought... a two question survey for customers.   This is for the P&L owner, the one that pays the invoice...   #1) Ask if they are willing to pay 10% extra for each dB of uncertainty you remove.   #2)  Ask them if lab can ignore MU for their product and give them 10% discount. Drop the response here in the mail list. ... all in good fun! As always, I wish all the best for my friends in EMI world ! Patrick. On Wed, Jul 12, 2023, 13:53 John Woodgate <j...@woodjohn.uk> wrote: Quite right. We don't need to add uncertainty to EMC measurements, because they are uncertain enough already.😉 ====================================================================================== Best wishes John Woodgate OOO-Own Opinions Only www.woodjohn.uk Rayleigh, Essex UK I hear, and I forget. I see, and I remember. I do, and I understand. Xunzi (340 - 245 BC) On 2023-07-12 21:17, Elliott Martinson wrote: A fun thing to do if you have access to a semi-anechoic chamber is use lots of duct tape to make sure absolutely nothing changes between measurements other than a certain design change--one accepted long ago that already went into production, which cost $$$ (cable ferrites, wrapping cables multiple times through ferrites, various black magic/witchcraft-based ideas)--and end up with evidence that a pass at a compliance lab years ago was misattributed to an expensive design change instead of a new test setup. Even all the duct tape in the world, however, doesn’t bring the uncertainty to 0.   The standard  almost addresses this as you’re supposed to (as best as I can remember) adjust the EUT’s position on the turntable relative to the cables, which are also to be individually adjusted (position/orientation) to maximize emissions for each frequency “of interest” (along with mast height if I remember right). Try that with a console with 20+ cables at even one frequency… with a simplifying assumption that a cable can either be laid out in state “A” or state “B”, that’s still over 1 million combinations. Good thing for the lab techs (and whoever pays the labs’ hourly rates) to have some “uncertainty” cushion   -Elliott     From: Brian Kunde <bkundew...@gmail.com> Reply-To: Brian Kunde <bkundew...@gmail.com> Date: Tuesday, July 11, 2023 at 9:31 AM To: <EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] FCC Part B questions   If I may pile on late, keep in mind that measurement uncertainty is Plus or Minus (±). Years ago when I was with a previous company, we had a buy/sell piece of junk product that we were selling with our company's brand/name on it. It was audited in Sweden as part of their surveillance program and it failed by 2dB.  The test lab said they could not say it FAILED because 2dB was within their measurement uncertainty, so we could continue to ship and sell this product in Sweden.    Has anyone else ever experienced this?     Thanks, The Other Brian     On Sat, Jul 8, 2023 at 8:28 AM Brent DeWitt <bdew...@ix.netcom.com> wrote: Hi Brian.  It's not entirely clear which measurement range you are asking about, but I'll assume conducted emissions in the range of 150 kHz to 30 MHz. Short answer: You can skip QP and Avg detection if the peak detection level is below the Avg detection limit. No margin is "required" to pass any emissions limit.  Zero dB margin is still passing.  That said, measurement uncertainty in that range is generally 3-4 dB, so having a passing margin greater than that gives you some confidence that a re-test at another time and lab will still pass. Hope that helps. respectfully, Brent DeWitt Milford, MA On 7/8/2023 12:38 AM, Brian Gregory wrote:    Hi there,   A question came up that I can't answer w/o a copy of Part 47. Does the FCC report require Quasi-Peak (QP) data, or just Avg and Peak.  When do peak readings trigger the need to report QP?  I'm pretty sure Part 15 has AVG and QP limits listed.   Next was what sort of margin is expected in order to pass CE emissions requirements (CISPR 16 or 32)?  Memory serves that one wants 3dB of margin, but memories can be imperfect!    "Colorado" Brian 720-450-4933 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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