re: Acoustical noise - summary and more questions
Moshe, There are several noise regulations in Europe that may be relevant, but most are dealing with ambient noise levels (all sources). There is very little that deals with the issue of product noise emission levels. This tends to be a competitive issue for many manufacturers. The one guideline document that may help was issued by a Swedish agency STATSKONTORET; the standard is STK 26; the second edition was issued in 1989; not sure about anything more recent. This document include noise emission guidelines for ITE. (I assume that is the area of interest). Another source for more recent information on ITE would be ECMA. Regards, Lyle Luttrell TUV Product Service - Original Text From: mvald...@netvision.net.il, on 4/17/97 11:48 PM: Hello everyone, thanks for pointing me to standards in this area. I did some reading and here is a summary: ISO 7779 Acoustics-measurement of airborne noise emitted by computer business equipment.: deals with HOW TO MEASURE (free field, reverberation room, sound pressure at the operator bystander position etc. The main idea is: define how to measure so that different products may be COMPARED. This is a relatively new standard (1996) ISO 3740-3746 (seven documents) Acoustic determination of sound power levels of noise sources-guidelines: this is also a HOW TO MEASURE. it is older (1980) ANSI S1.13 (ASA 118-1995) This is the american new standard of HOW TO MEASURE. It seems the americans would rather use sound pressure than sound power. I DID NOT FIND ANY LIMITS IN THESE STANDARDS I know offices have some 55dbA requirement (pressure level) but I did not find the source for that. I know there are also safety related requirements (I think the IEC1010 states one) which are much higher than the office requirement (which is based on noise not interfering with office work and human concentration) - Name: moshe valdman E-mail: mvald...@netvision.net.il Phone: 052-941200, 03-5496369 List-Post: emc-pstc@listserv.ieee.org Date: 17/04/97 Time: 23:48:06 -
Attachments (as in e-mail not telephoney)
I have noticed more and more of the people who subscribe to this list server are using attachments to send their e-mail. Usually the attachment is named without a three letter extension. For those of us using WIN95 and IE 3.0x these documents cannot be opened by clicking on them unless there is an extension (Thank you Bill Gates). This forces us to save and rename the document to view it. If people who use the attachment form of sending e-mail could please include some form of commonly used extension for your attachment (such as *.txt *.doc) it would be very helpful. Thank you Kevin Harris Manager, Compliance Engineering Digital Security Controls Canada +1 416 665-8460 Ext 378 e-mail comp_...@dscltd.com
Re: Attachments (as in e-mail not telephoney)
In message 199704232053.qaa24...@istar.ca Kevin Harris writes: I have noticed more and more of the people who subscribe to this list server are using attachments to send their e-mail. Usually the attachment is named without a three letter extension. For those of us using WIN95 and IE 3.0x these documents cannot be opened by clicking on them unless there is an extension (Thank you Bill Gates). This forces us to save and rename the document to view it. If people who use the attachment form of sending e-mail could please include some form of commonly used extension for your attachment (such as *.txt *.doc) it would be very helpful. Agreed, but may I humbly suggest it would be much better to send only straight ASCII text and save all the bother at the other end. This is, after all, a text discussion list, and graphics are simply a pain, and so is a graphical representation of character-based text. I use a simple, fast, pure ASCII editor (PCWrite) to email and to post to newsgroups. If you do use a wordprocessor, they can all export text in ASCII (DOS) form, stripping off all confusing formatting symbols. After all, the recipient may not have the same wordprocessor even if he/she can identify it. Just my $0.02! Regards to all, Bill. -- Bill Lyons - b...@lyons.demon.co.uk / w.ly...@ieee.org
Spark Gaps
Item Subject: cc:Mail Text Thank you all who responded. I had failed to mention that this printed wiring spark-gap has a slot in between the sharp points (electric field enhancers to facilitate breakdown) and yes, the solder mask is removed so that only bare copper shows. The creepage is fully compliant to table 6 so carbon tracking is not an issue (except for excessive high voltage transients). I also know that the exact voltage of spark gap operation is not fixed as many variables will control that. Now, having clarified that, is there an exemption to the clearance rules of table 3 if the spark gap could be treated as a pwb component? Thanks in advance Hans P.S. The radioactive material in encased spark gaps is usually Ni63 and the gas used is usually SF6 although other materials and gases have been used.
Re: Spark-Gaps and clearance rules
On Wed, 23 Apr 1997 hans_mellb...@non-hp-santaclara-om4.om.hp.com wrote: I have another question regarding class II equipment. My power supply intends to use a printed wiring spark-gap for transient/lightning protection. It's inherent design requirements are such that the air-gap spacing are less than those specified for double insulated (4mm). If the gap is increased to 4mm then this spark-gap will not work except at voltages too high to provide protection. Is anyone familiar with exceptions to the clearance rules when using spark-gaps? I have heard that some European countries don't like using MOVs (an alternative to a spark-gap) but a spark-gap cannot fail in a short circuit like a MOV could. It is a dangerous assumption to make that spark gaps do not go short circuit. With sufficient energy in the arc generated, the printed circuit base material can carbonise and leave a conductive path. Additionally we have used spark gaps in low voltage circuits and to be effective any conformal coating or screen must be left off in this area. This can cause leakage due to dust and moisture build up. If the spark gap may bypass other protective insulation, then I believe this is just as dangerous as an MOV in the performing the same function. My views only, Bruce Hunter
Re: Spark-Gaps and clearance rules
Hi Hans: Regarding your several questions: 1) Printed wiring spark-gap. This is a problem because the manufacturing variances of printed wiring makes the spark gap extremely variable in breakdown voltage. This is a further problem because when it operates, it creates a carbon path across the surface of the PC board. This reduces the breakdown voltage with every sparkover incident until finally the creepage finally becomes a resistor. 2) Spacings less than those required in safety standards. This simply cannot be done on a printed wiring board -- even if the spacing is intended to be a spark gap. In fact, it cannot be done even if it is a clearance gap rather than a creepage gap. And, it cannot be done even though a clearance is a renewable insulation and the construction is used to protect a safety insulation from catastrophic failure. This is the way the certification minds operate. 3) Discrete spark gaps. Strangely, these are usually accepted by the various certification houses even though an air gap is not accepted!. Usually, the certification houses will require them to be certified. 4) MOVs. No comment. Best regards, Rich
Spark-Gaps and clearance rules
Hi Hans. You wrote, amongst other things.. My power supply intends to use a printed wiring spark-gap for transient/lightning protection. Not a good idea... Mains transients and lightning etc. have a very low source impedance. If the volts get high enough to switch on your spark gap, you won't get a little blue spark accompanied by a 'tick' sound, you'll get a very big red flash that will effectively conduct a few thousand amps until your little fire ball takes out the local HRC protection device. When the flames eventually go out your 'spark gap will be a highly conductive black hole in the PCB about an inch diameter! PCB spark gaps are great on high impedance/current limited devices such as TV tube bases, where the current can't exceed a few microamps, and where the spark current drops the circuit voltage to the ionized air volt drop of the gap (say 60V), but if you try to drop your mains supply to the ionized volt drop of a 4mm gap, you'll need a lot more amps than your building will supply. MOV's don't have this problem, nor do proprietary gas-gaps which are already ionized by the addition of a radioactive material inside (that is the dust you see inside a gas gap, dispose of carefully). Serious lightening protection is achieved by stuff like the Phoenix Contact TRABTECH products, serious spike and surge protection is still achieved by MOV's. Of course, if you are intending to place your PCB spark gap as a 'component' before the mains get to your mains powered PCB, then you are proposing a sacrificial protection device, but you're still better off with a MOV. Just a thought or two. Chris Dupres Surrey, UK.
RE: Spark-Gaps and clearance rules
Below, Bruce Hunter assumes Hans Mellberg is using an air gap comprised of traces on a printed wiring board. When I first read Hans' message, I thought he was discussing discrete components. I have seen both used, but would like to ask you, Hans, to clarify your application, before we get off on a tangent. Regards, Peter L. Tarver Nortel ptar...@nt.com -- From: Bruce Hunter[SMTP:bru...@wormald.com.au] Sent: Wednesday, April 23, 1997 1:51 PM On Wed, 23 Apr 1997 hans_mellb...@non-hp-santaclara-om4.om.hp.com wrote: I have another question regarding class II equipment. My power supply intends to use a printed wiring spark-gap for transient/lightning protection. It's inherent design requirements are such that the air-gap spacing are less than those specified for double insulated (4mm). If the gap is increased to 4mm then this spark-gap will not work except at voltages too high to provide protection. Is anyone familiar with exceptions to the clearance rules when using spark-gaps? I have heard that some European countries don't like using MOVs (an alternative to a spark-gap) but a spark-gap cannot fail in a short circuit like a MOV could. It is a dangerous assumption to make that spark gaps do not go short circuit. With sufficient energy in the arc generated, the printed circuit base material can carbonise and leave a conductive path. Additionally we have used spark gaps in low voltage circuits and to be effective any conformal coating or screen must be left off in this area. This can cause leakage due to dust and moisture build up. If the spark gap may bypass other protective insulation, then I believe this is just as dangerous as an MOV in the performing the same function. My views only, Bruce Hunter
RE: Surge currents when powering up equipment..
The safety agencies will primarily look to see if the inrush will cause nuisance tripping of any overcurrent protection devices, including the branch circuit protection, and sometimes effects on additional earth leakage current. For your application, the North American agencies will assume branch circuit protector is rated 15A (assuming your using an ANSI/NEMA 5-15P attachment plug). Inrush current is typically monitored, but isn't generally a show-stopper without some secondary effect. Regards, Peter L. Tarver Nortel ptar...@nt.com -- From: Paul Herrick[SMTP:0007515...@mcimail.com] Sent: Tuesday, April 22, 1997 7:09 PM Does anyone know of any regulatory reason to control the startup surge current to ITE units? We have measured this startup current to be up to 90A for the first half cycle of applied voltage. The unit is cord set connected and uses four switching power supplies and has a rating of 100-120/220-240V 7/3.5A. Do safety agencies (UL/CSA/TUV) ever measure this start up current as part of a certification investigation? ++ Thanks, Paul Herrick 7515...@mcimail.com
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Re: Surge currents when powering up equipment..
Paul, UL 478 had a Starting Current Test in it, which was used to verify that start-up currents would not cause nuisance tripping of the overcurrent protective device. The main offenders tended to be devices with large motors. I believe you can still get UL to evaluate a product to 478 if you want to until 4/1/2000. The March 1988 IAC meeting report indicated that the intent of UL 478 clause 28.1 and 28.3 is implied in clause 1.7.2 of IEC 950, therefore the test method was not added to UL 1950. Kendall Wilcox kwil...@fcpa.fujitsu.com __ Reply Separator _ Subject: Surge currents when powering up equipment.. Author: Paul Herrick 0007515...@mcimail.com at SMTP-MAIL List-Post: emc-pstc@listserv.ieee.org Date:4/22/97 9:09 PM -- [ From: Paul Herrick * EMC.Ver #2.3 ] -- Does anyone know of any regulatory reason to control the startup surge current to ITE units? We have measured this startup current to be up to 90A for the first half cycle of applied voltage. The unit is cord set connected and uses four switching power supplies and has a rating of 100-120/220-240V 7/3.5A. Do safety agencies (UL/CSA/TUV) ever measure this start up current as part of a certification investigation? ++ Thanks, Paul Herrick 7515...@mcimail.com
RE: Three meter Pre-compliance tests /room shielding
Terry, Since you have been recording good results with your existing setup, I would favor lining the wall between the lab room and the offending equipment room with hardware cloth which has a smaller opening than chicken wire (about 1/2inch squares), and trying that out. Of course, bond the bottom of the screen every foot or two to a good earth ground. This would be a relatively inexpensive modification to your existing setup and may give you good results. If not, you are not out a lot of time or money and you can stiil persue other avenues. My opinion of course. Gabriel Roy Hughes Network Systems MD (61 days). snip -- Hello again: I would like some advise. I have been doing Pre-compliance testing in a room at 3 meters, using corrected limits, with good results. The room has large windows behind the UUT and a lunch room an stock room to the side and hall and offices across the hall to the other side. Behind the antenna has been a room for storage. Do to business success the space is needed for more offices. So corporate is moving the lab. The new options are not as attractive. One adjacent room will have open development equipment at times for long periods, the problem! The outside wall is a cement block wall facing a woods not too bad, I think. The other side is a dock area, not too bad. The question is, I have recently read of using chicken wire , cheap, to suppress the ambient and prevent distracting ambient.. This is attractive to me, if it works, since some of the clocks in the development equipment will have the same clock frequencies I will be trying to monitor in the UUT. 1. How serious a problem can I expect from reflections? My correlation has been good to this point and we would like to maintain it. 2. Would it be better to fight the ambient, possibly missing some frequencies, or build the `economical' screen room? Any advice will be appreciated! Thanks! Best regards, Terry J. Meck Senior QA/Test Engineer 215-721-5280 tjm...@accusort.com Accu-Sort Systems Inc. Telford, Pa USA
May 6-8, Boston
Join us at Electronics Industries Forum, World Trade Exhibition Center, Boston, Massachusetts, May 6-8 The EIF+97 Conference program has over 100 sessions organized into five major Summits, among them Technology and International Standards. Approximately 150 industry, government, and academic leaders will be speaking in these Summits. Chairmen of international EMC standard committees, FCC Chief, distinguished lecturers, recognized EMC and Product Safety experts accepted invitations to share their knowledge with the audience. If you are looking for update on FCC Part 15, CENELEC EMC specs in the pipeline or compliance design hints for your product at EIF+97 you will be at the right place. The EIF +97 Exhibition will bring together over 300 exhibitors, that are manufacturers of electronic devices, systems and components, with 10,000 decision-makers and qualified buyers from communications, medical, computer, networking and aerospace industries. If you are looking for a shielded room, antenna, LISN, ferrite suppresser, gasket, receiving system or EMC/Safety/Telecom test house at EIF+97 you will be at the right place. Special Focus Pavilion has been created as a special attraction on the exhibition floor. It will feature highlighted technology and advancements in the EMC. EIF +97 is sponsored by IEEE, IEEE EMC Society, Central New England Council, ERA and many other professional organizations. For information, please contact EIF +97 at phone: (800) 322-9332, fax: (203) 855-3003, Web Site: www.eifne.com Mirko Matejic IEEE EMC Society Boston Chapter, Chair Few confirmed presentations are: - Dan Hoolihan, Vice President, IEEE EMC-S, Medical Devices - ANSI Issues - Art Wall, Chief, FCC, Recent Advances in FCC EMC and Equipment Authorization Requirements - Ronald Storrs, Chairman, Swedish EMC Committee, Chair or member of EMC Standard bodies: IEC TC 65, CISPR, CENELEC, Update on European EMC Standards and Regulatory Issues - Stephen Berger, Vice Chair, IEEE EMC-S Standards Committee, Hearing Aid Digital Cell Phone Interference Issues - Joe Butler, IEEE EMC-S BoD Director of Technical Services, Shielding Effectiveness - Why Don+t We Have a Consensus Industry Standard? - Bill Ritenour, IEEE EMC-S BoD Distinguished Lecturer, ESD - A Tutorial - Lee Hill, IEEE EMC Distinguished Lecturer, Noise Filtering on Cables - Ron Brewer, IEEE EMC-S Distinguished Lecturer, EMC System Design - Peter Boers, Digital Equipment EMC Domain Manager, co-author of many European and U.S. EMC Standards, EMC: What are the Worldwide Regulatory Requirements And Their Impact on ITE Design, Marketing, and Importation - Richard Belanger, Digital Equipment, Group Manager, The Journey to a Compliant Product: International Regulatory Requirements And Their Impact on Product Design And Marketing; Today And in The Future - Michael Neuffer, Digital Equipment, Product Safety Domain Manager, International Product Safety: A Discussion of Product Liability Laws, Regulations, and Third Party Certification Agency Requirements for ITE - Valerie Watt, Digital Equipment, Manager, Telecommunications Domain and Test Laboratory - Eric Waters, Medical Device Directive Manager, TII, Medical Devices and International Regulatory Requirements: What are They and How You Can Assure Compliance to Them?
