Hi Jack, the definition is correct, but it is strongly related to the way the dk is measured (at least for low frequencies). Nowadays, other techniques are used to get material properties for higher frequencies and higher accuracy because it was shown that the "old way" wasn't accurate enough for todays electronic development. I think the definition should be improved to also refer to the impact of the dk. Maybe something like: Dielectric constant of a material surrounding a conductor affects the electric fields of the signal. It reduces the wavelength and the velocity of propagation. Both effects increase along with the dielectric constant. It can be measured as the ratio of capacitance of a two electrode setup separated by material under test vs. air. BR Gert Please visit us at the Hannover Messe from April 4 to 8, 2011. You can find us in hall 11, stand C13. http://www.hannovermesse.de/ -------------------------------------------------------------------------- Absender ist HARTING Electronics GmbH & Co. KG; Sitz der Gesellschaft: Espelkamp; Registergericht: Bad Oeynhausen; Register-Nr.: HRA 5596; persönlich haftende Gesellschafterin: HARTING Electronics Management GmbH; Sitz der Komplementär-GmbH: Espelkamp; Registergericht der Komplementär-GmbH: Bad Oeynhausen; Register-Nr. der Komplementär-GmbH: HRB 8808; Geschäftsführer: Edgar-Peter Duening, Torsten Ratzmann, Dr. Alexander Rost -----Ursprüngliche Nachricht----- Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im Auftrag von Jack Olson Gesendet: Mittwoch, 16. März 2011 20:18 An: SI-LIST Betreff: [SI-LIST] Definitions in IPC-T-50 Greetings, IPC-T-50 (Terms and Definitions) is currently under revision, and as I was browsing the latest entries (ok, I have a boring life...) I noticed the definition they give for DIELECTRIC CONSTANT. Dielectric Constant The ratio of the capacitance of a configuration of electrodes with a specific material as the dielectric between them to the capacitance of the same electrode configuration with a vacuum or air as the dielectric. See “Permittivity.†While that may be technically accurate, I wonder if it really helps the reader understand the significance of the term. As a member of the standards development committee I can submit recommendations for the next publication, so is this a good definition or could we do better? I suppose I should also include the following: Effective Relative Dielectric Constant The relative permittivity (See “Dielectric Constantâ€) of a mixed media configuration, such as air and the solid dielectrics used in microstrip, that has the equivalent electromagnetic wave propagation characteristics of a single dielectric medium. Permittivity The square root of the ratio of the electromagnetic wave propagation characteristics of free space to that of the dielectric medium. The permittivity, ï¥, of a material is, in general, a complex-valued (has real and imaginary parts) parameter. The real and imaginary parts of ï¥ are given by ï¥N and ï¥O. See "Dielectric Constant." (the missing characters above look like a backwards "3") ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu