RE: EMI trouble shoot inquiry
Ouch! Having an interference source that is only a slightly longer wavelength than the RFID frequency is a real tough problem. If the bombarders are only interfering with transmits/receives and not actual writing false data to the pallet markers I would suggest altering the system programming to read the pallet while the bombarders are off, and then disable the RFID system during the bombardment process. If the transponders actually are having garbage written to them by the bombarders you need to contact OMRON for help. Scott Lacey -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of wmf...@aol.com Sent: Monday, October 15, 2001 2:43 PM To: emc-p...@ieee.org Cc: jim.gi...@hedus.com Subject: EMI trouble shoot inquiry 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 Healddavehe...@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. --- 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 Healddavehe...@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.
Re: EMI trouble shoot inquiry
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 Healddavehe...@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])
Re: EMI trouble shoot inquiry
You don't say what the rf generator frequency is. If it is also MF (300 kHz - 3 MHz) ferrite tiles won't work. hard to give useful info without more definition of the culprit emitter and its purpose. If the rf generator drives a load through coax then it ought to be easy to shield it and contain the radiation. If the rf generator feeds an antenna then the problem is more difficult. If the rf generator operates at HF or above then filtering of the victim might be possible. But there simply isn't enough info here. -- From: wmf...@aol.com To: emc-p...@ieee.org Cc: jim.gi...@hedus.com Subject: EMI trouble shoot inquiry Date: Mon, Oct 15, 2001, 1:43 PM 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 Healddavehe...@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. --- 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 Healddavehe...@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.
RE: EMI trouble shoot inquiry
Without knowing anything about your system, RFID and RF bombarders, I will merely offer a SWAG. My guess is that the RFID system is a magnetic loop system? If so, copper will not have significant effect on shielding the system. Ferrous material will. Try a galvanized sheet steel for a shield. This is a commonly available material and will afford much better shielding effectiveness at that frequency than copper will. You will be using the sheet steel to guide the flux from the bombarder around instead of through the RFID system. If the shield is too close to the RFID system, you will warp the field of the intended RFID signal also. It might also be that you are on the threshold of receiver blocking for the proximity of the 400 kHz bombarder frequency compared to the desired 530 kHz RFID frequency . How sharp can you make a notch filter that is sufficiently stable for your environment? Good luck, Don Umbdenstock Sensormatic -- From: wmf...@aol.com[SMTP:wmf...@aol.com] Reply To: wmf...@aol.com Sent: Monday, October 15, 2001 2:43 PM To: emc-p...@ieee.org Cc: jim.gi...@hedus.com Subject: EMI trouble shoot inquiry 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 Healddavehe...@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. --- 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 Healddavehe...@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.
