Re: STP vs FTP Ethernet cables
Hi Paolo, I worked for a few years in the part of Bell Labs that was involved with networking cable systems several years ago. I am suspicious of foil shielded cables as it is difficult to properly terminate the foil shield (360 degrees). I have had a foil shield crack and split if the cable is flexed very much. On a related topic, a good UTP (unshielded twisted pair) system can have lower emissions and higher immunity than most shielded systems. The interface design is not hard to do to make this happen. I have seen cases where the presense of the shield causes immunity problems because a large noise current lands on the chassis of the data equipment. It there are slits and holes in the chassis (back of a PC?) problems result. Take a peek at the paper: http://www.dsmith.org/pdf/roma94.pdf which I authored several years ago and presented at the EMC Roma conference. In that paper a couple of commercial STP systems were compared with a good UTP system at a test lab in Switzerland. The UTP system won hands down on both emissions and immunity! The presense of a shield, by itself, does not guarantee good performance. I seem to remember also that the shielded systems had higher losses for signal transmission than UTP which resulted in shorter permissable cable lengths. Paolo, we can go offline if you want to discuss more details. Either call or email me. Doug Paolo Roncone wrote: Hi all, anybody out there can explain the difference between FTP (Foiled Twisted Pair) and STP (Shielded Twisted Pair) cables used for Ethernet links. In Ethernet standard IEEE 802.3 (2000) I find only a definition of STP (herebelow in copied and pasted from the standard - page 28): In a vendor's catalog, I found a definition of FTP as 1.4.249 shielded twisted-pair (STP)cable: An electrically conducting cable,comprising one or more ele- ments,each of which is individually shielded.There may be an o erall shield,in which case the cable is referred to as shielded twisted-pair cable with an o erall shield (from ISO/IEC 11801:1995).Speci .cally for IEEE 802.3 100BASE-TX,150 . balanced inside cable with performance characteristics speci .ed to 100 MHz (i.e.,performance to Class D link standards as per ISO/IEC 11801:1995).In addition to the requirements speci .ed in ISO/IEC 11801:1995,IEEE 802.3 Clauses 23 and 25 provide additional perfor- mance requirements for 100BASE-T operation o er STP. The reason of my inquiry is that we bought samples of STP and FTP cat.5 cables for 10bT ethernet applications from different vendors and to our surprise we discovered that both STP and FTP types have an overall (external) shield made of aluminum foil, but no shields on individual wires or wire couples (as per 802.3 definition above). Any inputs, suggestions etc. would be appreciated. Paolo --- Paolo Roncone EMC Compliance Engineer - Cisco Photonics Italy via Philips 12 - Monza (MI) 20052 mailto:pronc...@cisco.com phone: +39 039209 1538 fax: +39 039209 2036 -- --- ___ _ Doug Smith \ / ) P.O. Box 1457 = Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-( ) | o |Email: d...@dsmith.org \ _ /]\ _ / Website: http://www.dsmith.org --- --- 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.
STP vs FTP Ethernet cables (2)
This is a re-post with some corrections plus added some letters that got lost on the way from the .pdf file. Sorry for the inconvenience. Hi all, anybody out there can explain the difference between FTP (Foiled Twisted Pair) and STP (Shielded Twisted Pair) cables used for Ethernet links. In Ethernet standard IEEE 802.3 (2000) I find only a definition of STP (herebelow in copied and pasted from the standard - page 28): 1.4.249 shielded twisted-pair (STP)cable: An electrically conducting cable,comprising one or more ele- ments,each of which is individually shielded.There may be an overall shield,in which case the cable is referred to as shielded twisted-pair cable with an overall shield (from ISO/IEC 11801:1995).Specifically for IEEE 802.3 100BASE-TX,150 ohm balanced inside cable with performance characteristics specified to 100 MHz (i.e.,performance to Class D link standards as per ISO/IEC 11801:1995).In addition to the requirements specified in ISO/IEC 11801:1995,IEEE 802.3 Clauses 23 and 25 provide additional perfor- mance requirements for 100BASE-T operation over STP. The reason of my inquiry is that we bought samples of STP and FTP cat.5 cables for 10bT ethernet applications from different vendors and to our surprise we discovered that both STP and FTP types have an overall (external) shield made of aluminum foil, but no shields on individual wires or wire couples (as per 802.3 definition above). Any inputs, suggestions etc. would be appreciated. Paolo --- Paolo Roncone EMC Compliance Engineer - Cisco Photonics Italy via Philips 12 - Monza (MI) 20052 mailto:pronc...@cisco.com phone: +39 039209 1538 fax: +39 039209 2036
STP vs FTP Ethernet cables
Hi all, anybody out there can explain the difference between FTP (Foiled Twisted Pair) and STP (Shielded Twisted Pair) cables used for Ethernet links. In Ethernet standard IEEE 802.3 (2000) I find only a definition of STP (herebelow in copied and pasted from the standard - page 28): In a vendor's catalog, I found a definition of FTP as 1.4.249 shielded twisted-pair (STP)cable: An electrically conducting cable,comprising one or more ele- ments,each of which is individually shielded.There may be an o erall shield,in which case the cable is referred to as shielded twisted-pair cable with an o erall shield (from ISO/IEC 11801:1995).Speci .cally for IEEE 802.3 100BASE-TX,150 . balanced inside cable with performance characteristics speci .ed to 100 MHz (i.e.,performance to Class D link standards as per ISO/IEC 11801:1995).In addition to the requirements speci .ed in ISO/IEC 11801:1995,IEEE 802.3 Clauses 23 and 25 provide additional perfor- mance requirements for 100BASE-T operation o er STP. The reason of my inquiry is that we bought samples of STP and FTP cat.5 cables for 10bT ethernet applications from different vendors and to our surprise we discovered that both STP and FTP types have an overall (external) shield made of aluminum foil, but no shields on individual wires or wire couples (as per 802.3 definition above). Any inputs, suggestions etc. would be appreciated. Paolo --- Paolo Roncone EMC Compliance Engineer - Cisco Photonics Italy via Philips 12 - Monza (MI) 20052 mailto:pronc...@cisco.com phone: +39 039209 1538 fax: +39 039209 2036
Re: CE marking 'e' mark products
I read in !emc-pstc that Chris Chileshe chris.chile...@ultronics.co.uk wrote (in 01c13473.83e6a9e0.chris.chile...@ultronics.co.uk) about 'CE marking 'e' mark products', on Mon, 3 Sep 2001: Most of my designs have been engineered for the 'e' mark i.e. vehicle automotive EMC. This means the front end is ISO 7637 (transients) compliant. I now have a requirement to extend the operating environment to any 12-30V DC power supply running off mains, in a bid to CE mark the product. I believe I need to perform ESD and RF emissions and immunity, but what about the Fast Transients and Surge tests? Is my product exempt because it does not actually connect to the mains supply, Almost certainly, but since we don't know which EMC standard applies to your product, one cannot be sure. and if so, is there a requirement I can place on the user's power supply (apart from the usual tolerances) that in someway guarantees that any EFTs and Surge voltages are dealt with satisfactorily i.e. not coupled through? Simply that it conforms either to the product standard applicable to your product or to the standard for stand-alone power supplies. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Eat mink and be dreary! --- 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.
CE marking 'e' mark products
Hello Group, Most of my designs have been engineered for the 'e' mark i.e. vehicle automotive EMC. This means the front end is ISO 7637 (transients) compliant. I now have a requirement to extend the operating environment to any 12-30V DC power supply running off mains, in a bid to CE mark the product. I believe I need to perform ESD and RF emissions and immunity, but what about the Fast Transients and Surge tests? Is my product exempt because it does not actually connect to the mains supply, and if so, is there a requirement I can place on the user's power supply (apart from the usual tolerances) that in someway guarantees that any EFTs and Surge voltages are dealt with satisfactorily i.e. not coupled through? Would appreciate your advice. Best regards - Chris Chileshe http://www.ultronics.co.uk _ This message has been checked for all known viruses by Star Internet delivered through the MessageLabs Virus Scanning Service. For further information visit http://www.star.net.uk/stats.asp or alternatively call Star Internet for details on the Virus Scanning Service. --- 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: Medical application-Isolation voltage
Ron, The Mains to Applied part isolation (Sub-clause 20.2, category B-a) is typically achieved by selecting a power-supply that meets IEC 60601-1 requirement. This also helps meet Sub-clause 20.1, category A-a1 A-a2 of the standard. Most medical grade Power-supplies will meet 4KV isolation, as well as the required creepage/clearance distances. If you have BF applied part - you will need isolation at the Applied part as well. This is more trickier than isolating mains since you need to assure that your Applied part signals are not affected. This isolation is greater of the two - double insulation (dependent on the voltages on your applied part) or basic insulation (at 240 Volts) - which assumes that if another equipment with probes into the patient fails, you will be applying 240V to your applied part. Hope this helps. Thanks Dan Modi Asst. Director - Product Certification Alcon Surgical (Note: All opinions are personal, and do not reflect that of my employer). -Original Message- From: owner-emc-p...@majordomo.ieee.org [mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Ron Sent: Wednesday, August 29, 2001 11:26 AM To: EMC Subject: Medical application-Isolation voltage I have a medical application that requires double insulation from the Mains to an applied part according to IEC60601. IEC60601 states that for a reference voltage of 250v and double insulation, the test voltage is 4000v for 1 min. I am assuming that the voltages are RMS values. How does one go about meeting the 4000v test when the highest rated ac-dc converter I can find is 3500v RMS continuous. Any help is appreciated. Thanks. Ronald Cyprowski Vascor Inc. 566 Alpha Drive Pittsburgh PA 15238 412-963-7438 x139 r...@vascor.com --- 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. --- 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: Isolation Transformer improvements article
Dear all, I belive it should be Vol 43 No: 3. However, I canot verify this because as of today have not received my copy via snail-mail in Singapore. :-( Tim Foo, (or just call me 'Tim') ECE, School of Engineering, http://www.np.edu.sg/ece/ Tel: + 65 460 6143 Ngee Ann Polytechnic, Fax: + 65 467 1730 535 Clementi Road, Singapore 599489 Pete Perkins peperkin...@cs.com To: PSNet emc-p...@ieee.org Sent by: cc: (bcc: Wan Juang Foo/ece/staff/npnet) owner-emc-pstc@majordomSubject: Isolation Transformer improvements article o.ieee.org 09/02/01 11:54 PM Please respond to Pete Perkins PSNet, Here is a reference to an article describing an improved isolation transformer design. It may be of interest to some here. It can be found in the IEEE Transactions on EMC, Vol 443, No 3, Aug 01. Title Author: 'Characteristics of a Special-Isolation Transformer Capable of Protecting From High-Voltage Surges and Its Performance' by Akihiko Yagasaki. snip --- 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.
