Peter, My understanding is that each series, E12, E24, etc increments approximately according to the corresponding tolerance such that adjacent values approximately meet at the upper tolerance of one value and the lower tolerance of the next greater value. This is rounded off to the nearest integer value, hence 10, 12, 15, 18, 22, etc for a tolerance of ±10%; i.e. E12 series for ±10%, E24 series for ±5%, and so on.
Best regards Neil R. Barker CEng MIET FSEE MIEEE Manager Quality Engineering e2v technologies (uk) ltd 106 Waterhouse Lane Chelmsford Essex CM1 2QU UK Tel: (+44) 1245 453616 Fax: (+44) 1245 453571 Mob: (+44) 7801 723735 P Please consider the environment before printing this email. From: Tarver, Peter [mailto:peter.tar...@sanmina-sci.com] Sent: 13 March 2007 15:24 To: PSTC 1 Subject: OT: standard component values An off-topic question that hopefully someone can shed a little light upon. I have wondered for as long as I've been involved in things electrical, why standard component values are what they are. Text books are of no use and I've done more than a few internet searches on this in the last ten years (or so; maybe I've used the wrong search terms, but I haven't found an answer). I'm interested to hear what others might know or think about this arcane topic. It's probably lost to history now, but it may well be based on some limitations of physical characteristics of early devices or one manufacturer dominating the early production of components and they had some idea that they could sell more components if they were in strange increments. Or maybe there's a mathematical reason that hasn't occurred to me, like some arithmetic progression, or even simple phobias or prejudices. Maybe someone gave it the deepest thought and surmised that particular values would yield the minimum of mixing of components in series/parallel combinations. Maybe they're still laughing from the grave. Regards, Peter L. Tarver ptar...@ieee.org CONFIDENTIALITY This e-mail message and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail message, you are hereby notified that any dissemination, distribution or copying of this e-mail message, and any attachments thereto, is strictly prohibited. If you have received this e-mail message in error, please immediately notify the sender and permanently delete the original and any copies of this email and any prints thereof. ABSENT AN EXPRESS STATEMENT TO THE CONTRARY HEREINABOVE, THIS E-MAIL IS NOT INTENDED AS A SUBSTITUTE FOR A WRITING. Notwithstanding the Uniform Electronic Transactions Act or the applicability of any other law of similar substance and effect, absent an express statement to the contrary hereinabove, this e-mail message its contents, and any attachments hereto are not intended to represent an offer or acceptance to enter into a contract and are not otherwise intended to bind the sender, Sanmina-SCI Corporation (or any of its subsidiaries), or any other person or entity. ____________________________________________________________________________ _ Scanned by Sanmina-SCI eShield ____________________________________________________________________________ _ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Sent by E2V TECHNOLOGIES PLC or a member of the E2V group of companies. A company registered in England and Wales. Company number: 04439718. Registered address: 106 Waterhouse Lane, Chelmsford, Essex, CM1 2QU, UK. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
