Comparing manufacturer impedance curves is only a start. I know of no standard that all the manufacturers use to obtain their data. The best way is to use a network analyzer yourself and compare a sampling of the two beads in question. Saturation curves add a whole dimension to ferrite measurements. Some manufacturers will provide you with saturation curves, others current rate their beads depending on a certain level of saturation or reduction in impedance. There were some companies that rated ferrite current carrying capability by temperature rise in the ferrite and some that rated their ferrite chips at the current they burned themselves off the PCB. Since most ferrite is rated by impedance at 100 MHz there are procurement folks who have bought ferrite beads from separate vendors that only matched impedance at 100 MHz. The curves above and below that point were not even close. A quick glance at the curves could have averted that. Earl
From: [email protected] mailto:[email protected]]On Behalf Of Georgerian, Richard Sent: Friday, May 21, 2004 12:59 PM To: IEEE Subject: Ferrite core test methodology Greetings All, In regards to measuring for the Z impedance for ferrite cores and beads, is there a specific standard that ferrite vendors use to create such curves? For that matter, are there any such standards? I would suspect that if test set-ups and methodologies are different from vendor to vendor, comparing curves would not be too helpful. Any thoughts and comments would be appreciated. Thanks. Richard ===== Richard Georgerian Compliance Engineer Carrier Access Corporation 5395 Pearl Parkway Boulder, CO 80301 USA Tele: 303-218-5748 Fax: 303-218-5503 mailto:[email protected]
