Hi all, This thread has been interesting. However it has taken a somewhat philisophical turn. I'd like to "distill" it a little bit. In short, FCC + FCC does equal FCC in certain circumstances just like CE + CE = CE in certain circumstances.
You need to ask yourself: (honestly and sincerley without the influence of mind altering substances) Self, 1. Do I manufacture all of the pieces of this system? 2. Are all of the pieces of this system already FCC approved? 3. Is the FCC approval appropriate for my intended environment (i.e needs Class B for residential)? 4. Am I satisfying the test assumptions for the pieces that are already FCC approved? (i.e am I using shielded cables where required, am I following the grounding recommendations?) 5. Am I using the pieces of this system in their intended environments? 6. Do I have design control over the pieces of the system? (i.e did you or your company layout the circuitboards, choose the components ...) 7. Will my system be used in situations in which interference could comprimise public or personal safety? (as opposed to simply screwing up the neighbor's reception of "I Love Lucy".) 8. Have I spent a couple of years in compliance engineering? Do I feel comfortable making these decisions? Have I reviewed the test data? If you can answer: 1. No (A "yes" hurts only slightly) 2. Yes 3. Yes 4. Yes 5. Yes 6. No (A "yes" hurts only slightly) 7. No (This one MUST be "No") 8. Yes, Yes, Yes Then you can be 95% certain that FCC+FCC = FCC. Only 95%!!!!!! Oh no! Hold on, before you write that $5,000 check for EMC testing, remember that most EMC tests themselves have double digit percentage errors. One warning. If you are going to make a "Large Number" of IDENTICAL systems, and you plan to make "alot" of money off of them; or if you have any gut feeling that someone could get hurt; do the test anyway. It's just good sense. (I'll let you decide what "Large Number" and "alot" mean :-) You can use the same reasoning for CE + CE = CE (from an EMC perspective) Yes, yes I know that there are some that will say that every system must be tested, even if you build it in your basement. But the reality is that EMC measurements are a "fuzzy" realm. Tests are fuzzy approximations of real world conditions. Some of the tests have error margins of 30-40%. The emissions and immunity standards have a built in 120dB "safety margin" to account for this (or you could argue that the "safety margin" was accidentally put there because the emissions standards were designed to protect antenna coupled receivers). Either way, it is there. It doesn't mean that we can be cavalier with EMC; but we can use good judgement to save time, money and hassles. The same time and money that can be better spent mitigating real EMC and safety problems. All of these rationales are behind why both the EMC directive and the FCC rules give some leeway with the Declaration of Conformity process. With many "fuzzy" logic questions the best piece of test equipment that you can use is a trained neural network. An experienced brain is a prime example. Why not call a vertically- applied manulo-pedally-operated quasi-planar chernozem-penetrating and excavating implement a SPADE? BECAUSE SOMETIMES IT'S A SHOVEL!!!! My opinions only. Chris ------------------------------------------- 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: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
