Hi Ed and all:
Ed asks: "BTW, does anyone know when component manufacturers started using this tolerance progression? From my own observation, the system was in place for 1930's era design. Was it codified under some old EIA standard, or is it even older?" The EIA did not exist in the '30's. The '30's was the era of the RMA, Radio Manufacturers Association. These folks as well as resistor and capacitor manufacturers published cards with wheels so you could decode the color stripes and dots on resistors and capacitors. I believe the standard values for resistors and capacitors came >from RMA, or at least they were used in that era. RMA evolved to RTMA, RETMA, and then EIA. I'll leave it to the reader to guess the names for the RTMA and RETMA acronyms. If you're stuck, do a Google search and all will be revealed (but not for RMA). Of course, us old timers remember the color code memory jogger for BBROYGBVGW. ;-) Best regards, Rich - 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 [email protected] 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] 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 ______________________________________________________________________
