Eddie All Z0 calculators have a built in "fudge factor" to make modelled results agree with emperical data. It is called "dielectric constant" Gerry From: Eddie Rocha <[log in to unmask]> Reply-To: TechNet E-Mail Forum <[log in to unmask]>, Eddie Rocha <[log in to unmask]> To: [log in to unmask] Subject: Re: [TN] impedance testing Date: Tue, 15 Nov 2005 11:53:11 -0700 I've evaluated multiple impedance calculators. I did as you are doing, used actual x-section data with actual TDR results and compared it to the calculators results. Some calculators worked well with some stack-ups but not with all types of stack-ups. A good calculator should have a "fudge factor" that allows you to determine the best "factor" that works for a particular stack-up. Actual data is needed to make an impedance calculator accurate. Thank you, Eddie Rocha South Bay Circuits Hello, If there are any impedance testing gurus out there I have a question for you. We are testing an edge coupled offset strip line coupon. We modeled the stack up to give us 100 ohms differential. When we test the coupon we get around 130 ohms. We have done a microsection of the coupon and modeled the coupon data and Polar says we should have 105 ohms, within tolerance. We had a 4 panel lot and it is consistent across the board. The coupon is constructed correctly. My question is, other than what I am seeing on the microsection should I look for to find the culprit of the high reading? Any help would be great. Jim Henderson Colonial Circuits --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------