3 possibilities: 1/
I am not sure where exactly it comes from , maybe whit the SI definitions? http://physics.nist.gov/cuu/Units/index.html At school I learned: “ When no tolerance is given, +/- half of the number of significant digits is assumed. “ When writing down 10 there is only one significant digit, so +/- 5 cm will do. Note : 10. (10dot) has 2 significant digits http://en.wikibooks.org/wiki/FHSST_Phys cs_Units:Scientific_Notation,_Significant_Figures_and_Rounding 2/ At the other hand, the 10 cm is not a result of a measurement, so “ A defined value is infinitely accurate” 3/ Good knowledge of the used EM model and the required accuracy of the incident current to be realized in EUT cabling might help you in reverse engineering the needed accuracy. These are not a reasons to omit the 10cm tolerance in the standard, But this is something to fall back to. Gert Gremmen Ce-test, qualified testing bv Van: [email protected] [mailto:[email protected]] Namens Brent G DeWitt Verzonden: woensdag 1 april 2009 4:58 Aan: 'Price, Edward'; [email protected] Onderwerp: RE: [PSES] 10cm above GRP requirement for 61000-4-6 I also find this to be a constant irritant in standards. From my old (very old) days in machining, I’ve used the definition of plus or minus one half the least significant digit of the measurement. Bummer for “3 meter” radiated emissions measurements! Brent DeWitt Westborough, MA From: Price, Edward [mailto:[email protected]] Sent: Tuesday, March 31, 2009 4:35 PM To: [email protected] Subject: Re: [PSES] 10cm above GRP requirement for 61000-4-6 ________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of Bob Richards Sent: Tuesday, March 31, 2009 1:10 PM To: [email protected] Subject: 10cm above GRP requirement for 61000-4-6 Fellow EMCers, 61000-4-6 says that the EUT must be 10cm above the GRP. There is no tolerance. However, anyone that has worked in a machine shop or in metrology knows that there is no such thing as "no tolerance". What would be considered an acceptable tolerance for the 10cm requirement? If an auditor says that the support for the EUT has to be exactly 10cm, "no tolerance", how can one argue with them that 1mm is not going to affect the test? The EFT standard, 61000-4-4, says 10cm +/- 1cm. Could this be used as a basis for an argument? Bob Richards, NCT Bob: FWIW, MIL-STD-461, which has been around longer than 61000 (and thus was probably the inspiration for "10 cm"), says, in Paragraph 4.3.1., "Unless otherwise stated...tolerance shall be... Distance: +/- 5%" Ed Price [email protected] <blocked::mailto:[email protected]> WB6WSN NARTE Certified EMC Engineer Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 Military & Avionics EMC Is Our Specialty - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]>
