Hello Wm: Troubleshooting an EMI problem by telephone or email is usually a very tall order. The best that could probably happen is for someone to point you in the right direction.
1) I agree with Ken, a clue lies in the generator frequency 2) Does the problem occur only at the station where the signal generator is used? If so, this gives a big clue to the nature of the coupling 3) If by "ferrite tiles" you mean "broadband absorbers", these are usually intended for absorption of incident RF at frequencies above 30 MHz. Their reflection coefficient is poor by design, so they wouldn't help nearly as much as a localized conductive shield or high mu material (if these turned out to be appropriate solutions) 4) I bet the stationery read/write heads drive a high Z input amplifier/IC. That is the most likely place for the system to be disturbed. Chances are you have either capacitive coupling into the amplifier, or inductive coupling in to the head/amp interconnect. Were your copper shields tied to the low side of the amplifier? 5) If the problem is occurring at the RFID read frequency (530 kHz), and some absorption is the key, then steel is not necessary, thick copper (~ 0.5mm) will give > 40 dB attenuation at this frequency. But it may easier to either reduce the read circuit loop area, and/or provide a local capacitve (copper/tin/any good conductor) shield at the receive amp/IC. You need schematics and pictures to solve this problem effectively and quickly. Lee Hill Founding Partner Silent Solutions LLC EMC Consulting and Training 10 Northern Blvd., Suite 1 Northwood Executive Park Amherst, NH 03031 (603) 578-1842 x203 (V) (603) 578-1843 (F) lh...@silent-solutions.com www.silent-solutions.com In a message dated 10/15/2001 2:57:03 PM Eastern Daylight Time, wmf...@aol.com writes: > Subj: EMI trouble shoot inquiry > Date: 10/15/2001 2:57:03 PM Eastern Daylight Time > From: wmf...@aol.com > Sender: owner-emc-p...@majordomo.ieee.org > Reply-to: wmf...@aol.com > To: emc-p...@ieee.org > CC: jim.gi...@hedus.com > > > > > > Group: > I attach an RF interference inquiry from a customer; I have no 'smarts' > where RF ID is concerned, so I turn to this august body... > > ==paste==We have an OMRON RFID data transfer system operating within the > same room as 12 RF generators (bombarders). The transmission frequency for > the RFID system is 530 kHz and the transmission frequency for the > bombarders is 400 kHz. The RFID system works through an antenna embedded > in a pallet and a stationary read/write head. The bombarders are > positioned on a platform overhead. The normal sequence is for a pallet > containing a bulb to move via conveyor to a read/write station where > information is taken from and added to the pallet. The pallet is conveyed > through several different processes, being read/written on roughly 8 > occasions. One of the processes contains an RF generator. We are > experiencing problems with the RFID system when the RF generators are on. > The read/write system operates properly when the RF generators are off. We > have determined that the RF generators are creating an interference that > does not allow the RFID to operate properly. Initially, w! > e built copper shields in the area of some > of the RFID stationary heads. This did not seem to help. We also placed > EMI suppressors on the RFID cables(near the read heads). This also was not > helpful. I have spoken to a company that suggested the use of Ferrite > tiles to absorb the interfering waves. The problem with these tiles is > that they are very brittle and difficult to use for shields. The concept > sounds good but I don't have much flexibility in where I can place the > shields. I am currently trying to use ferrite magnets attached to the > copper guards. Any help/suggestions you could give me would be greatly > appreciated. > ===end paste== > Thanks for any suggestions; reply as you see fit. > > WmFlanigan > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: pstc_ad...@garretson.org > Dave Heald davehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server. > > > ----------------------- Headers -------------------------------- > Return-Path: <owner-emc-p...@majordomo.ieee.org> > Received: from rly-xe02.mx.aol.com (rly-xe02.mail.aol.com > [172.20.105.194]) by air-xe01.mail.aol.com (v81.9) with ESMTP id > MAILINXE14-1015145703; Mon, 15 Oct 2001 14:57:03 -0400 > Received: from ruebert.ieee.org (ruebert.ieee.org [140.98.193.10]) by > rly-xe02.mx.aol.com (v80.21) with ESMTP id MAILRELAYINXE24-1015145643; Mon, > 15 Oct 2001 14:56:43 -0400 > Received: (from daemon@localhost) > by ruebert.ieee.org (Switch-2.1.0/Switch-2.1.0) id f9FIhbY05915 > for emc-pstc-resent; Mon, 15 Oct 2001 14:43:37 -0400 (EDT) > Date: Mon, 15 Oct 2001 14:43:20 EDT > From: wmf...@aol.com > Subject: EMI trouble shoot inquiry > To: <emc-p...@ieee.org> > Cc: <jim.gi...@hedus.com> > Mime-Version: 1.0 > Content-Type: text/plain; charset=ISO-8859-1 > Content-Transfer-Encoding: 7bit > X-Mailer: Unknown (No Version) > Message-ID: <16c.2654a1e.28fc8...@aol.com> > Sender: owner-emc-p...@majordomo.ieee.org > Precedence: bulk > Reply-To: wmf...@aol.com > X-Resent-To: Multiple Recipients <emc-p...@majordomo.ieee.org> > X-Listname: emc-pstc > X-Info: Help requests to emc-pstc-requ...@majordomo.ieee.org > X-Info: [Un]Subscribe requests to majord...@majordomo.ieee.org > X-Moderator-Address: emc-pstc-appro...@majordomo.ieee.org >
