Mary, Probal\bly the truest definition I've come across is in IPC-2141 and some of the other IPC specs. In IPC-2141 look at section 3.4.2 thru 3.4.3. Here's a partial: 3.4.2 Relative permittivity (Dielectric Constant) The relative permittivity, Er, of a substance is defined as the ratio of the permittivity of the material to the permittivity of free space, which has a value of 1.00. Dielectric constant is the term in common use in industry even though "dielectric constant" varies with certain parameters. Factors that influence the relative permittivity of a givcen material include the electrical frequency at which the measurement is performed, temper- ature, and extent of water absorption. (snip) The effective relative permittivity, Er', is the relative permittivity that s experienced by an electrical signal transmitted along a conductive path. etc,etc,etc I've heard the arguements in interpertation before also, so I always keep this spec handy. Hope this helps, Mitch Morey Sr PCB Designer ComStream Corp San Diego CA 92121 Email: [log in to unmask] Check out: www.comstream.com >>> Doug McKean <[log in to unmask]> 02/09/98 01:54pm >>> You're on. Permittivity is also dielectric constant. Ok, so what? Time for real simple terms. Think of it like lens. It's the ability of a material to *focus* an electric field (electric lines of force) as a result of electric charges. The higher the dielectric constant, the better the capacitor. A material with a dielectric constant or permittivity of 4 is four times better a capacitor than say a capacitor with just air between the plates. The *air* cap will have a voltage breakdown at 1/4 the voltage that the cap with a dielectric constant has across it. Higher dielectric constants increases the electrical strength of the material. You can do the same type of analogy with permeability. Permeability is the ability of a material to focus *magnetic* lines of force. And so forth ... That do it fer ya? Regards, Doug ---------- > From: [log in to unmask] > To: [log in to unmask] > Subject: [DC] Permittivity > Date: Monday, February 09, 1998 4:03 PM > > To: IPC > Date: 2/6/98 > Re: Permittivity > > From: Mary Sugden [log in to unmask] > The Copper Connection, Inc. > Ph(408) 970-9838 Fx(408) 970-9184 > hhtp//www.copperconn.com > ________________________________________________________________ > > I would like to have a clear and consise definition for the term > "permittivity" as it relates to dielectric materials. I have > read no less than fifty different definitions and descriptions > and still do not have a clear and consise definition. In > several of the references, it simply states, ...see dielectric > constant. However, the other descriptions and definitions of > permittivity lead me to believe there is a subtle difference > between the two terms. The definitions for relative dielctric > constant are fairly clear and consistent between the various > references I have used, but the definitions for permittivity are > ambiguous and inconsistent. > > For the best definition, I will send the dude or dudette a > nice bottle of California White Zinfandel > > _________________________ Shareware ____________________________ > > > "Will you teach your children what we have taught our children? > That the Earth is our mother? What befalls the Earth, befalls > all of the sons and daughters of the Earth. > > This we know; The Earth does not belong to man, man belongs to > the Earth. All things are connected like the blood that unites > us all. Man did not weave the web of life, he is merely a > strand in it. Whatever he does to the web, he does to himself.." > > ...Chief Seattle In a letter to President Pierce, 1852 > > ################################################################ > DesignerCouncil E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c > ################################################################ > To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: > To subscribe: SUBSCRIBE DesignerCouncil <your full name> > To unsubscribe: SIGNOFF DesignerCouncil > ################################################################ > Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. > For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 > ################################################################ ################################################################ DesignerCouncil E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE DesignerCouncil <your full name> To unsubscribe: SIGNOFF DesignerCouncil ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################ ################################################################ DesignerCouncil E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE DesignerCouncil <your full name> To unsubscribe: SIGNOFF DesignerCouncil ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################