RE: EMC in the news: RFID Medical
TNO made a suggestive title by referring to RFID devices, where most problems are induced by only 2 of the available systems. Probably to draw more attention for their article, and they succeeded. TNO is a Netherlands institute for applied science and have been forced to change their way of being financed from public to private. Apparently, most of the problems occur with high power 868 MHz backscatter RFID systems. These are conditionally allowed to transmit up to 3.8 watts EIRP (Friss tells us that that might be up to 50 V/m ) For frequency power allocations in NL : http://www.agentschaptelecom.nl/nfr/main_nfr_uk.html This is close to the GSM-standard and power range, and we all know that these devices are to be used with care (forbidden) in medical environments. These RFID’s are definitely not the items we usually use as RFID such as Legic, Mifare or other low power RFID systems. The article should therefore be read as a warning against high power RFID backscatter technologies. While we can discuss about if Medical equipment should or should not be immune to this field strength, we may discuss the suitability of these 868 MHz backscatter radar type RFID systems, in medical and residential environments where fields of 3 or maximum 10V/m should be expected. I wonder btw how this allowance of 2W ERP (3.8 W EIRP) got into the European frequency tables. Maybe because the power and frequency are close to GSM. Not taking into account the much closer operating distance that goes with RFID. For the time being we will have to live with RFID technologies that interfere with medical (and other) electronics, until the standards committees again noticed their lag on technology. and raise the immunity levels to 50 V/m or more. (EN 55024 for example still uses 3V/m and limits the test range to 1 GHz only , where 1.8 GHz GSM are used all over Europe, and even higher frequency UMTS systems are being rolled out: new problems are to be expected!) Regarding the discussion: both interfering RFID systems should not be ‘simulated’ with the EN 6100-4-6 method, as the 125 kHz is below it’s f-limits (and would go unnoticed), and the other is way above it’s upper f-limits (80 or 230 MHz) Gert Gremmen ce-test, qualified testing bv Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Ken Javor Verzonden: Friday, June 27, 2008 12:57 AM Aan: Untitled Onderwerp: Re: EMC in the news: RFID Medical None of the below. 61000-4-3 specified rf source impedance is 150 Ohms, calibrated into 150 Ohms load impedance. The 1, 3, and 10 Volt levels are open-circuit quantities, thus the potential developed in the matched load is one-half the limit. The current flowing on a cable under test will depend on the cable impedance, which is not controlled, except on the AE side, because the injection device is designed to insert a high common mode impedance on the AE side of the cable (high relative to 150 Ohms). As far as I know, you do not measure injected current doing the test this way. There is an alternative current injection test when a suitable coupling device is not available, but then you inject and measure current, not rf potential. The current limit is the short circuit current available from the open circuit potential limit divided by the 150 Ohm source impedance, even though you will not have a 150 Ohm source impedance when injecting current. Ken Javor Phone: (256) 650-5261 From: Daniel Roman dan.ro...@dialogic.com List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: Thu, 26 Jun 2008 17:53:59 -0400 To: Ken Javor ken.ja...@emccompliance.com, Untitled emc-p...@ieee.org Conversation: EMC in the news: RFID Medical Subject: RE: EMC in the news: RFID Medical While slightly off-topic, this discussion got me thinking about the measurement of the voltage on the cable. If done with a RF cable current clamp, do you have to do a conversion of some sort if the cable is assumed to be 150 ohms? For a 50 ohm system, a 3V level measured with a clamp would be 96 dBuA minus the transfer impedance in dB ohms. If the cable is 150 ohms though does that mean you are measuring the equivalent of 1V from the clamp instead of 3V because the clamp is measuring current? Stated another way, assuming the transfer impedance of the current clamp is zero to simply things, for an assumed 150 ohm cable should you be reading 96 dBuV on a spectrum analyzer hooked up to the probe or something less that than equivalent to 1V? Never worked with this stuff so I’m curious. Dan From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Ken Javor Sent: Thursday, June 26, 2008 11:14 AM To: Untitled Subject: Re: EMC in the news: RFID Medical Comment (e) is unrealistic. Assuming 61000-4-6 was applied, the amount of power required to directly inject 1, 3 or 10 Volts oc into 150 Ohms is
Re: EMC in the news: RFID Medical
In message 48640ca5.3060...@orionscientific.com, dated Thu, 26 Jun 2008, E. Robert Bonsen robert.bon...@orionscientific.com writes: Assessment took place^ according to an international test protocol. Really? Don't they cite the reference? I don't know of one that covers 125 kHz and 868 MHz. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Either we are causing global warming, in which case we may be able to stop it, or natural variation is causing it, and we probably can't stop it. You choose! John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Power Spectral Density Measurement
Dear Members, Thank you very much to those whe have commented. FYI. We found out the data discrepancy was caused by a test fixture/board (support test commands to set up channels and power level) and the length of power lead (from EUT to DC power supply). Best regards, Grace On 6/18/08, Grace Lin graceli...@gmail.com wrote: Dear Members, I need your help to find out what may be wrong/inaccurate for the power spectral density measurement per 47 CFR 15.247. I was told the data I took was about 6 dB higher. I follow the measurement procedure (PSD Option 1) for the digital transmission system, published by the FCC ( https://fjallfoss.fcc.gov/oetcf/kdb/fo ms/FTSSearchResultPage.cfm?id=21124switch=P). The antenna port of the transmitter was connected to the RS ESU40 receiver (in spectrum analyzer mode). Data was taken with and without 30dB attenuators to avoid overload issue. RBW=3kHz, VBW=10kHz, Span=1.5MHz, Sweep=500s. I couldn't figure out where might be wrong. Thank you and look forard to your instructions. Best regards, Grace - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: EMC in the news: RFID Medical
Whilst I've seen the original article (Journal of the American Medical Association), unfortunately I can't circulate it without breaking our subscription license agreement. The investigation was apparently commissioned by the Dutch Ministry of Health. Standard they refer to is - American National Standard Recommended Practice for On-site Ad Hoc Test Method for Estimating Radiated Electromagnetic Immunity of Medical Devices to Specific Radio-frequency Transmitters (Standard C63.18). (AAMI:/ IEEE; 1997). (not a rigorous EMC product test standard - but rather a suggested basic methodology for equipment users to investigate possible EMI in a consistent way) The project was apparently driven by the search for a system to monitor blood products, which influenced their choice of RFID systems to test, as follows - The selection of 2 RFID systems tested in this study was based on 3 characteristics: (1) the systems needed to comply with RFID standards set by the European Telecommunications Standards Institute; (2) radio frequencies needed to fall within the most common internationally used RFID frequency bands and (3) performance needed to fulfill the operational requirements of the project including availability of temperature sensitive RFID tags, low-cost tags suitable for disposable materials, contemporary integration with the local communications network, and location accuracy within a health care facility. Tests were performed in a 1-patient room, free of reflective objects, based upon methodology in the standard above. Ged Dean Nottingham University Hospitals NHS Trust ___ _ -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org mailto:emc-p...@ieee.org ] On Behalf Of John Woodgate Sent: 27 June 2008 08:29 To: emc-p...@ieee.org Subject: Re: EMC in the news: RFID Medical In message 48640ca5.3060...@orionscientific.com, dated Thu, 26 Jun 2008, E. Robert Bonsen robert.bon...@orionscientific.com writes: Assessment took place^ according to an international test protocol. Really? Don't they cite the reference? I don't know of one that covers 125 kHz and 868 MHz. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk file://www.jmwa.demon.co.uk and www.isce.org.uk file://www.isce.org.uk Either we are causing global warming, in which case we may be able to stop it, or natural variation is causing it, and we probably can't stop it. You choose! John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - The information contained in this email may be the subject of public disclosure under the Freedom of Information Act 2000 - unless legally exempt from disclosure, the confidentiality of this email and your reply cannot be guaranteed. Copyright of this email and any attachments created by us remains vested in the Nottingham University Hospitals NHS Trust. This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. This footnote also confirms that this email message has been swept by security software for the presence of known computer viruses. Nottingham University Hospitals NHS Trust City Hospital campus | Hucknall Road | Nottingham | NG5 1PB | Tel: 0115 969 1169 QMC campus | Derby Road | Nottingham | NG7 2UH | Tel: 0115 924 9924 If you have received this email in error please notify the sender. ID:QMCICT1 - B486510b70002.0001.0001.mml - 17:09:27 06/27/08 - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: EMC in the news: RFID Medical
In message c1bb4f6866f4d144bb37968587d03a64e47...@cexc01.nuh.LOCAL, dated Fri, 27 Jun 2008, Dean Gerard (Medical Physics) gerard.d...@nuh.nhs.uk writes: Whilst I've seen the original article (Journal of the American Medical Association), unfortunately I can't circulate it without breaking our subscription license agreement. Thanks for the information you have given, anyway. The elephant in the room is the field strength information. Is there anything about that in the paper? -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Either we are causing global warming, in which case we may be able to stop it, or natural variation is causing it, and we probably can't stop it. You choose! John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
FW: EMC in the news: RFID Medical
Just nominal power outputs and separation distances between interfering and susceptible equipment. Output info given is - The passive RFID system selected for this study (OBID, Feig Electronic, Weilburg, Germany) had an 868-MHz reader (2-4 W). The active RFID system (Eureka RFID, Avonwood, England) had a 125-kHz reader (68_10E-3 µT at 1m) that forces tags to transmit in its proximity. The active RFID tag had an operational frequency of 868 MHz at 2 µW Interference effects were provoked at separation distances ranging from 5 - 600cm, depending upon equipment affected. Ged Dean Nottingham University Hospitals NHS Trust -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org mailto:emc-p...@ieee.org ] On Behalf Of John Woodgate Sent: 27 June 2008 17:28 To: emc-p...@ieee.org Subject: Re: EMC in the news: RFID Medical In message c1bb4f6866f4d144bb37968587d03a64e47...@cexc01.nuh.LOCAL, dated Fri, 27 Jun 2008, Dean Gerard (Medical Physics) gerard.d...@nuh.nhs.uk writes: Whilst I've seen the original article (Journal of the American Medical Association), unfortunately I can't circulate it without breaking our subscription license agreement. Thanks for the information you have given, anyway. The elephant in the room is the field strength information. Is there anything about that in the paper? -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk file://www.jmwa.demon.co.uk and www.isce.org.uk file://www.isce.org.uk Either we are causing global warming, in which case we may be able to stop it, or natural variation is causing it, and we probably can't stop it. You choose! John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc http://www.ieeecommunities.org/emc-pstc The information contained in this email may be the subject of public disclosure under the Freedom of Information Act 2000 - unless legally exempt from disclosure, the confidentiality of this email and your reply cannot be guaranteed. Copyright of this email and any attachments created by us remains vested in the Nottingham University Hospitals NHS Trust. This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. This footnote also confirms that this email message has been swept by security software for the presence of known computer viruses. Nottingham University Hospitals NHS Trust City Hospital campus | Hucknall Road | Nottingham | NG5 1PB | Tel: 0115 969 1169 QMC campus | Derby Road | Nottingham | NG7 2UH | Tel: 0115 924 9924 If you have received this email in error please notify the sender. ID:QMCICT1 - B48651855.0001.0001.mml - 17:41:57 06/27/08 - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: EMC in the news: RFID Medical
This is great information. Thank you for providing some details. The comment: had an 868-MHz reader (2-4 W). is informative. It indicates that the RFID was not the only transmitter in the proximity of the medical EUT. This RFID reader adds another parameter that requires control and investigation during the test. continuing the list of possibilities: f) is it possible that the RFID tag has much less effect than that of the RFID reader? Would be informative to find out if the RFID reader, in the absence of the tags themselves, can duplicate any of the EUT problems. Best Regards, Patrick. p.con...@hp.com From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Dean Gerard (Medical Physics) Sent: Friday, June 27, 2008 11:48 AM To: emc-p...@ieee.org Subject: FW: EMC in the news: RFID Medical Just nominal power outputs and separation distances between interfering and susceptible equipment. Output info given is - The passive RFID system selected for this study (OBID, Feig Electronic, Weilburg, Germany) had an 868-MHz reader (2-4 W). The active RFID system (Eureka RFID, Avonwood, England) had a 125-kHz reader (68_10E-3 µT at 1m) that forces tags to transmit in its proximity. The active RFID tag had an operational frequency of 868 MHz at 2 µW Interference effects were provoked at separation distances ranging from 5 - 600cm, depending upon equipment affected. Ged Dean Nottingham University Hospitals NHS Trust - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: EMC in the news: RFID Medical
Hi John: No, the article doesn't mention field strength. However, the test procedure is one I'm not familiar with: ANSI C63.18-1997, 'American national standard recommended practice for an on-site, ad hoc test method for estimating radiated electromagnetic immunity of medical devices to specific radio-frequency transmitters' In short, they vary the separation between the RFID device and the medical equipment from 600 cm (20 feet) down to 0 cm (touching the equipment case), and record the distance where the equipment failed. Random RFID devices, random power levels, with a test distance down to zero? I appreciate RFID interference is something to be considered. However, it's not fair to compare the immunity standard used in the report, to the pass/fail testing with the fixed amplitude/fixed distance conditions in present IEC immunity tests (mentioned elsewhere in the email thread.) Pat Lawler EMC Engineer SL Power Electronics Corp. John Woodgate j...@jmwa.demon.co.uk wrote on 06/27/2008 09:28:20 AM: In message c1bb4f6866f4d144bb37968587d03a64e47...@cexc01.nuh.LOCAL, dated Fri, 27 Jun 2008, Dean Gerard (Medical Physics) gerard.d...@nuh.nhs.uk writes: Whilst I've seen the original article (Journal of the American Medical Association), unfortunately I can't circulate it without breaking our subscription license agreement. Thanks for the information you have given, anyway. The elephant in the room is the field strength information. Is there anything about that in the paper? -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Either we are causing global warming, in which case we may be able to stop it, or natural variation is causing it, and we probably can't stop it. You choose! John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
