Actually Earl - I am in complete agreement with you. I think you may have misunderstood my comments. Let me explain:
1. On the CE+CE maybe = CE comment. No question here. I agree. Many systems fail emissions (maybe immunity) testing due to incompatible combinations. BUT... As I am sure you know, the FCC has a Class B compliance system that allows for exactly that. PCs can be assembled from sutiably marked components (such as video cards) and marketed WITHOUT furthur testing. This results in non-compliant units (admitted by the FCC) released on the market place with NO intent by the FCC to enforce the rules. (BTW - The Australians have released an equivalent scheme with the proviso that a metal enclosure be used) 2. Here is the crux of my issue with the FCC. The logic and the physics don't match. To illustrate: A recent thread has described the origin of the emissions standards and generally everyone agrees what a jolly good thing it is too. That being the case, how could the the FCC put into law a process that allows for systems to be released on the market place WITHOUT testing. To me the existing FCC Class B procedures render the emissions standard irrelevant. After all why should any manufacturer concern themselves with the standard when the FCC blatenly ignore it themselves? 3. If you have monitored this list recently, you should have seen my comments regarding the emissions limits. To reiterate: Raise the limits 20db but make EVERYONE test. Although this may seem ridiculous - compared to the FCC Class B process it makes a lot of sense. This process maintains the INTENT of the emissions spec in the first place - that is to maintain a KNOWN level of interference. OK -OK so folks will bleat about cycle time etc... So an alternate solution is to truely engineer the EMC at the component level. Design tests/procedures to adequately test at the componet level AND (this is key) have the regulatory agencies redesign the emissions limits to meet the 21st Century. Call me if you want to chat furthur. -----Original Message----- From: Morse, Earl [mailto:[email protected]] Sent: Friday, June 18, 1999 3:36 PM To: Grasso, Charles (Chaz); 'Lou Gnecco'; [email protected] Subject: RE: NEAR/ FAR FIELD CORRELATION ISSUES I beg to differ. It is ludicrous to believe that components or for that matter subassemblies can be certified and then combined to make a compliant system. CE + CE doesn't always equal CE The reduction of emissions is highly reliant on component placement. The same parts can be arranged on circuit boards in compliant and non-compliant patterns. Same with subassemblies. While the current measurement techniques are difficult they are about as close to the "truth" as we can get. Even if that means an 8 dB swing from site to site. The reason that we see PCs consistently fail by as much as 20 dB is because of a lack of enforcement. Many computer manufacturers sneak through the requirements with their one of a kind golden units never to worry about compliance again. Very few get caught and it is worth the bucks to keep the production lines going rather than shutdown the lines. Who was the last computer manufacturer you heard of that was forced to shutdown until an EMC problem was fixed? I have a book of test reports on competitor's products. They fall into the categories of compliant, near compliant (looks like they tried), and fails miserably (didn't try, didn't care, and outright lied on any self declarations). The failing companies seem to be doing just as brisk a business as the passing companies without having to worry about the cost of EMC. Earl Morse Portable Division EMC Design Compaq Computer Corporation Phone: 281.927.3607 Pager: 713.717.0824 Fax: 281.927.3654 Email: [email protected] <mailto:[email protected]> -----Original Message----- From: Grasso, Charles (Chaz) [mailto:[email protected]] Sent: Friday, June 18, 1999 10:33 AM To: 'Lou Gnecco'; [email protected] Subject: RE: NEAR/ FAR FIELD CORRELATION ISSUES I cannot agree more!! We, not the government, need to drive the technology for EMC. I have followed this thread with interest. I have long believed that if EMC was to maintain credibility we (EMC ) would have to come up with a method of demonstrating compliance in spite of the many and varied combinations. One way is to test at the component level - like our Safety brethren - and call the assembly of tested components good!! This is methodology can be made consistent with good engineering design practice unlike the existing FCC rules for Class B equipment. On the surface the FCC Rules appear to be similar to component level testing - but under the hood, they are completely different. There are PCs out there that fail by as much as 20dB. I am all for a more logical and consistent design approach to EMC!! Thank you Charles Grasso Advisory Engineer StorageTek 2270Sth 88th Street Louisville CO 80027 M/S 4247. Tel:303-673-2908 Fax:303-661-7115 email:[email protected] Web Site: http://www.ewh.ieee.org/r5/denver/rockymountainemc/ -----Original Message----- From: Lou Gnecco [mailto:[email protected]] Sent: Friday, June 18, 1999 6:52 AM To: [email protected] Subject: Re: NEAR/ FAR FIELD CORRELATION ISSUES For this to work, the government would have to change the rules completely, setting a new set of near field procedures and limits. This is doable but hard to sell. A good way to start would be if we did it. If someone in industry writes up a procedure and a set of limits, then everyone could use that as a "straw man", (criticizing and refining it) until eventually most people agreed. Eventually it could become an industrial (such as IEEE) standard. Then the govt would find it much easier to adopt it as is or after making their own modifications. lou --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
