TEMPEST
Hi Qu. You wrote: I don't think that the letters stand for anything, rather it is a (British?) set of performance specs, standards, requirements essentially aimed at maintaing confidential communications. E.g. a Tempest monitor will not bleed video or z modulation signals that may be picked up by a sensitive receiver nearby. I've seen a demosnstration at an exhibition where the exhibitor of an 'Intrusive Monitor System' was able to dut up a screen display of all the screens around him at will, just by homing in on their timebases and video signals with a highly directional antenna. TEMPEST, seeks to eliminate this leak of 'intellligence'. It's not only monitors, but data comms, RF, printers, anthing which could radiate, or conduct, data to an interested and well equipped third party. At least I think that's what it is. :-) Chris Dupres Surrey UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: New EMC requirements proposed for IEC60335
Hi Scott. You wrote: < It's sometimes all too easy to forget WHY we perform these tests. While we are trying to comply with written requirements in order to "pass", we are also trying to ensure product performance in the real world,> Time for my favourite hobby horse again... Going back even further than your memory, back in fact to 1972, the Treaty of Rome in Europe. This was when the Euro Nations decided to get into a single trading bed and knock down barriers to trade within Europe. In Europe, we called it the Common Market. In the US it is often called 'Fortress Europe'. Whatever, as a result of this treaty, all Euro Nation States had to follow Directives, one of which was raised in 1989, the EMC directive, which sort to regularise EMC performance within Europe. The purpose of this Directive, I need not remind you, is to ensure that no Euro State, or any other state for that matter, couldn't steal a trading advantage by making their equipment cheaper by building to a lesser standard of EMC performance. I suppose it was levelling the playing field, such that everything had to meet a minimum standard. Since then the standard required is slowly getting stiffer, but whether this improves the lot of the Euro Proletariat or not, I have my doubts, but sure as hell the sales of filters, screening and EMC testing services has gone through the roof. I could ask, "Who are the CISPR committees, who told them what constituted a suitable EMC performance? Who voted them into power, who let them put the price of my TV up?" Who told the BS and DIN people to make my life more complicated and more expensive by constantly making the EMC requirements more difficult to meet? I don't remember voting for them... But as I earn my living supporting exactly that business, it would be churlish to do so, so I wont just now. If you read the Directive, you will note that terms like 'Removal of barriers to trade', and 'free movement of goods across borders' etc. are mentioned so often it gets boring. But not once does it say anything about making the world a less EMC active place, or anything about improvements to the environment or living quality by the reduction of interference. No, the EMC Directive is a financial/political package, the politicians who approved the Directive's publication wouldn't recognise an EMC if it fell on their foot. Our activities in trying to achieve Euro EMC standards is merely to meet the political aspirations of a European Economic Area, and so far that seems to at least stopped big wars in Europe for the last 50 years or so. Maybe that's the real reason for all this. Another self opinionated twopence worth from a tired, cynical, aging EMC hack. Chris Dupres Surrey, UK. p.s. Has anybody heard about the Bad Haircut Directive? - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Copy of: Re: Reducing magnetic influence on PC-monitors
-- Forwarded Message -- From: Chris Dupres, 100014,3703 TO: Dana Dorsett, INTERNET:d...@papillonres.com DATE: 11/12/98 22:56 RE: Copy of: Re: Reducing magnetic influence on PC-monitors Hi Dana and the Group. These sort of problems are typical of the sort of thing you have with Electron Microscopes. Quite often the cure is simply to turn the transformer round so that the leakage flux is in a null or innefective direction. Very rarely have I had to put a Mu-Metal or similar screen around them. Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
The regulatory effect of distribution strategies
Hi Chris. Heres a twopence worth. You asked: Whoever places the stuff 'on the market' in the EEA must take responsibility for CE marking. Software doesn't have any directives to follow, but it's packaging does. Mustn't be poisonous, have sharp edges, give off gas etc. etc. Any hardware must, I suspect, comply with the requirements of the Medical Devices Directive. IEC601 is the relevant standard. If these products are sold in cardboard boxes as individual self-contained units which can be assembled into a multitude of different arrangements, then you should CE mark each component. If however these units CANNOT do anything useful on their own and necessarily require another unit to do anything at all, then they should be CE marked as a system, or sub-system. If your systems are sold in boxes but invariably end up as what could be described as a fairly common or 'standard' setup, then you should CE mark the system. This gives you a few logistical problems as the purpose of the CE mark is to allow free passage of goods across borders, and has no purpose at all in qualifying the 'quality' of the goods. CE marking od 'components' isn't strictly legal, though your unlikely to go to jail over it. < Is software typically CE marked? > The purpose of the CE mark is to allow free trade within Europe. The only thing relevant here is the type of packaging and the actual medium etc., which mustn't be painted in lead based paint, mustn't spontaneously burst into flame, etc. etc. If you shipped your s/w via the Internet, what do you CE mark? < are we still considered the "manufacturer" under the medical device directive?> You are the 'manufacturer' of the bits you supply. The person who actually puts the system together as a functional entity in the EEA is the person who carries the can. Either he carries out the CE qualification exercise, or gets you to supply the stuff already qualified. This is a commercial arrangement twixt you and he. There has to be somebody for the regulatory authorities to terrify, and if you are off shore Europe they can't reach you, so it's the local supplier or the end user who must ensure that the equipment is CE marked. < Yes, as far as the regulatory authorities are concerned. The active term is 'placing on the market', or for a system made in house or put together from a plurality of parts, the person who 'puts into service' the end system. The Regulatory authorities use the 'last person to touch it' principle, though a seemingly valid certificate and CE mark is a good defence (due diligence). There is a natural justice at work here, if you supply something into the EEA which causes someone to fall foul of the Regs, then they are unlikely to buy any more of your equipment, and will go to a competitor. Or they won't pay you!!! :-) Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Active Power Factor Correction
Hi Doug. The ERA in Leatherhead, UK, was doing a lot of work with this stuf, and had a product. Tel:+44 (0) 1372 367030 Fax: +44 (0) 1372 374074 Email: i...@era.co.uk Sorry. I don't recall the chap running the group. Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Ferrites
Hi Colin and the group. You mentioned: I find ferrite sleeves, snap-on and otherwise, incredibly useful for reduction of emissins from cables, but for HF feeder and antenna drive purposes I find them a bit iof a nuisance. I haven't studied these especially, apart from the manufacturers data etc., but I find these ferrites to be very lossy. This 'lossiness' is invaluable for providing an HF dumpng ground for any loose HF resonant energy, or HF ringing energy on high speed digital lines for instance. If you drive coax lines with high speed data, all those 0/1 transitions are very fast, and quite capable of kicking the coax screens into a resonant condition sufficient to provide a very significant peak somewhere, particularly noticeable on video outputs from PC's etc. Especially bad if cables are incorrectly terminated of course. These ferrites provide some impedance to act as a low pass filter, and also provide enough losses for the ferrite to absorb that blocked energy. If there was no losses I reckon the resonance would simply move somewhere else in the spectrum. I suppose that if there was sufficient HF activity in these cables with ferrites fitted, one could expect the ferrites to get hot! I haven't noticed this particular phenomenon yet Has anyone tried the trick of running a 3mm copper wire through the Ferrite with the suspect cable, and soldering it into a 'shorted turn' configuration. Got some interesting results, not spectacular, just interesting Just a twopence worth for the opinion bucket. Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: Supply Frequency Variations
Hi Egon. You wrote: I'm pretty sure that over a 24 hour period, the mains has to be +/- 1 cycle. i.e. in the UK the generators must turn exactly 4,320,000 times in 24 hours. Short term variations are not worried about excessively. At different times of day I see mains hum bars going UP the TV screen, and at other times they go DOWN. Our TV frame timebase is 50Hz. Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: CE+ CE = CE
Hi Pryor. You wrote: < do these products which make up the system require re-testing to the EMC Directive and a DoC issued for the system or are the DoCs for the individual modules sufficient for importing and sale in the EU? Can a system DoC be generated based upon the individual module DoCs?> There is an important divison of catgories in rack mounted equipment. 1. Equipment which comprises 'stand alone' components, where the rack is really not much more than a convenient and aesthetically acceptable way of putting it all in one box. The implication is that these components don't iteract significantly, except maybe a few analogue signals and that the a.c. mains power supplies are common to all units. The removal or addition of rack components would have no effect on the others. Such equipment could be, as I've illustrated before: a) Inverter type motor speed controls where the output goes straight out of the box to motors, no connections to adjacent inverters. b) Instruments, where inputs from the outside world and outputs to the outside world are direct, and with little internal rack connection between instruments. I call these systems 'Independent' systems. 2. Equipment which comprises components which have no 'stand alone' functionality, where the rack is really the outside skin of a unique piece of equipment. Such equipment is characterised by a significant number of connections between the rack components, and the inability of these components to operate without the others. Examples of such equipment could be: a) Industrial batch weighing systems, where each function is carried out by a seperate rack component. e.g. scaling module, amplifier module, tare module, logger module, comparator module, display module, relay module, etc. etc. These equipments are characterised by very many internal connections between the rack components modules, each 'module' being critical to all other modules. b) Rack mounted PC systems, where the PC, keyboard, monitor, printer, etc/ are all mounted in a 19" rack - such as commonly used in industrial process environments, often in desk drawer type racks. I call these systems 'dependent' systems. 3. My feeling is that: a) Independent systems (1. above) can be declared compliant if all the individual rack mounted sub systems are themselves already compliant, INCLUDING the rack itself, with all it's power supply distribution! b) Dependent systems (2. above) are new pieces of equipment and would require a new set of test data and compliance certificate. Your own system that describes 3 computers, disk arrays and a UPS would, in my mind comprise a 'dependent' system (2. above) and I would therefore treat it as a new unique product, and test it accordingly. There you are, another load of unsolicited self opinionated rose fertilizer, perhaps... Have a nice weekend, Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
CE+ CE = CE
Hi Brian and the group. This is a bit of an old chestnut, with as many answers and reasons as you'd care to make. It's just not possible to state a case which covers all situations.. At the one end of the spectrum you have RF equipment emitting all over the place, just under limit, and when you put these together you have additions and subtractions which can entirely change the emissions envelope. At the other end you have essentially low frequency equipment which can have it's emissions very easily predicted with a high degree of certainty. The EC last year allowed for 'systems' to be assembled with CE marked sub systems, and claim compliance. This was a common sense approach to situations in the automation and machine tool and laboratory type industries where, for instance, you have an Inverter motor speed controller which is CE marked in a panel, and another, and another, and another... etc. It doesn't take a brain surgeon to realize that a multitude of inverters = a lot of emissions, and that to make these compliant with 50081 (for instance) would take a great deal of expense and hardware, if indeed it was possible at all. It is not the intention of the Euro EMC directive to make things impossible to market, but to ensure that no-one catches a steal on marketing advantage by taking EMC shortcuts. We had a situation where any machine which had more than a few inverter speed controls was uncompliable(?). The 'Systems' approach gave enough versatility to the regs to enable such equipment to be manufactured and supplied with evidence of 'Due Diligence' being applied. Essentially. this really means that 10 seperate inverters in their own cabinets (all of which have a CE mark) are not really any different to those same 10 inverters placed into one cabinet. Another view might be that of equipment comprising many 19" rack mounted CE marked instruments connected together with cables as an ad hoc 'system'. If these instruments are standing on tables and benches, as would be in a laboratory type situation, should they be subject to different rules than if those same instruments and cables are stacked on top of each other, and yet again if that stack of instruments is housed in a 19" rack. That's my twopence worth, look forward to hearing the views of others. Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
re: Indicator color standard
Mark and the group. Following on from Francis L. Fiedler's question. Can anybody tell me what is the correct lamp colour for Illuminated Mains Switches, the type of thing you see on a PC, or a washing machine, or a TV - whatever?. Usually a rocker switch with an integral neon indicator. PC switches tend to be green. Washing machines and kettle switches are often red. I find it a bit confusing trying to reconcile a switch lamp colour with the need to use 'red for alarm', and 'green for safe'. Is this written down anywhere? Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
EMC limits.
EMC Folk. I have been reading all the learned submissions of what constitutes the acceptable emission limits for EMC purposes. Most of you are very clever, very technical, and I'm in awe of all of you. But there seems to be a bit of a missed point here. EMC in Europe relates to the EMC Directive, which was born of the SIngle Market arrangements between Euro States, and which were born of the Treaty of Rome way back before my kids were born. The ultimate purpose of EMC Standards/limits is to provide a level trading platform for Euro countries, so that all conditions are equal in the market place, and that no-one can steal a lead over someone else by dropping technical standards and therefore saving costs and putting cheaper goods on the market. It follows that perhaps we should look at these limits in the same way that the packaging industry looks at filling cans and bottles, or the way car drivers treat speed limits. i.e, that the EMC emission limits are a target in absolute terms, and if you can show honest intent in achieving them, then the legislation has achieved it's aim. If I carry out an honest emissions test on a piece of equipment, and the graph is below the line by the thickness of the pen, then I believe that the spirit of the EMC Directive has been met. If this acceptance level was an absolute amount, such as money in banking, then I would allow a % for measurement error, but it isn't, it's an objective. No-ones head is going to explode if the emissions are 0.5dB over limit, and in all honesty dropping the emissions by 0.5dB can usually be achieved by moving a cable or snapping on a ferrite sleeve. Hardly enough to change the whole balance of trade in Europe is it? So, if I carry out properly conducted tests, with the equipment working normally, and it shows emissions right on the limit, then I think the EMC Directive has been followed, and the equipment can be CE marked with honesty and placed on the market. Just a tuppence worth (what's THAT in Euro's?) Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
re: Doubt on LISN utilization
Hi Barry. You wrote: I've been here before The reason for making the distinction between use at 110V and 220V is precisely because someone is going to supply a Tx for 110V use, so the effect of that Tx can be taken into account. I once tested some 110V production equipment for a company, wrote all the documentation, filled all the certificates, etc. etc. Had to use some big filters to keep the SCR noise down at 150kHz to 600kHz. Then I visited them when they were packing some for despatch, and they put a 2kVA transformer in the case. "What's that?" I asked... "Oh, all the machines go out with those, we only sell to the UK and Europe." I retested, and was able to take away a 70 UKP filter and save them a fortune in parts and labour. I've had a few like that. Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Copy of: Doubt on LISN utilization
-- Forwarded Message -- From: Chris Dupres, 100014,3703 TO: Muriel Bittencourt de Liz, INTERNET:mur...@inep.ufsc.br DATE: 21/10/98 19:12 RE: Copy of: Doubt on LISN utilization Hi Muriel. You asked: Transformer(220/110) => LISN => EUT ( Equipment Under Test ) My questions are: # am i doing right? # is it possible to use a transformer? # isn't the transformer acting like a "unintentional" filter? > It's simple. There are two scenarios. 1. If the equipment is to be used at 220V, then test it with the actual transformer that will be used to provide 110V, AFTER the LISN. Think of the 110V transformer and the EUT in a cardboard box. All you are doing is providing 220V, you aren't particularly interested in what happens in the box, only in the emissions. The transformer is critical to emissions, as you suggest, and will attenuate emissions very usefully. That's why you should place it AFTER the LISN so that you can measure that attenuation. 2. If the equipment is to be used at 110V, then place the 110V transformer BEFORE the LISN, so that the LISN gets to see the actual emissions from the EUT before they get to the transformer. Hope that helps. Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Biological effects of low-level, low-frequency electromagnetic fi elds.
Hi John. You wrote: You'll forgive the healthy cynicism of the British Public when they read statements like that. Opinion polls actually show that such statements can have the opposite effect than that intended. It's like a fatal blow to the 'Power lines are safe' lobby. We remember those 'Oh so many' appeals that 'Beef is safe - honest', and 'We are cutting out all the spinal material - honest', and 'We are not feeding ANY rendered beef to cows - honest'. Recent history is crowded with learned groups making learned statements, only to be shown later that they were completely wrong. Sometimes it's better to say nothing than 'Not Guilty'. Just a cynical twopence worth. Chris Duprés Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Ozone...
Hi Ed. Oh I see you've been sniffing that stuff then Chris - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Ozone...
Good PSTC People. Is Ozone a toxin? Many years ago I had a factory inspector threaten to close down some High Voltage test equipment because there was too much Ozone being produced. Lately we have had bad vibes about a Xerox copier making too much Ozone and threats of ill health etc. to operators. So my questions are: Are there any legal limits on the production of Ozone? Is it dangerous/what are the physiological effects? Where can I find out about it? Why do they sell Ozone generators for use in kitchens and bathrooms, does it get rid of smells etc.? Why do I get a headache and a tight chest when I'm around this stuff? Funny stuff, Ozone. Sure makes screws go rusty very quickly! Any information anybody wants to share? Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Safety concerns w/ Reed Switches
Hi Colin. You wrote: < I am having difficulty finding Reed Switch manufacturers that have a European Safety certification. ( TUV, VDE, etc. )> I don't think that I would ever use a reed switch on it's own for safety purposes. Whenever I use one I ALWAYS use it with a fast fuse rated at approx 25% of it's rated switching current in series. There are reed switches offered described as 'heavy duty, etc., mercury wetted, non-weld, and with various methods of preventing the contacts sticking on overcurrent, but I wont sign the Safety Certificate unless there is a $0.30 fuse in the circuit. There are potted reed switch/fuse (non replaceable) assemblies on the market that require Samarium Cobalt magnets to pull them in (not many people carry these turkeys), and these have BS approvals for use as Guard Interlock switches. Is this the type of thing you are looking for? Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: Forget about WM what about UL?
Matthias and the group. You wrote, in part: This was enough to stir this sluggish finger tip into pushing a few keys. I've been noting all the comments on all the Marks around with interest. But it seems to me that we are not comparing like for like, that all marks perform quite different functions. I have a simplistic and perhaps cynical brain, but I get the impression that these marks exist because it's to someones advantage that they do. In the case of UL, it's because components that have been tested have been shown to be at least risk of starting a fire, or causing litigation problems due to breakdown, i.e. they minimise the risk to Insurance Companies. In the case of EN 61010, equipment is required to be safe in all that that means. i.e., if you eat it it shouldn't poison you, it shouldn't catch fire, shouldn't have nasty sharp edges, shouldn't hurt your back if you lift it, shouldn't hurt your eyes by being too bright, shouldn't electrocute you, etc. etc. But this requirement isn't primarily for safety reasons, it's directly linked to protecting trade through the Euro Low Voltage Directive. Many marks in the past, and perhaps even now, have had the suggestion that they were essentially a device to protect a particular market. This was a 'accusation' often levelled at Germany and it's DIN standards, and the Nordic SEMCO, NEMCO, DEMCO rules, amongst many others. (I very pointedly make NO judgement on these matters...) There were/are many others. I'm not entirely unconvinced that some were just invented by some groups just to justify there existence. Many 'safety' marks exist around the world, but I wonder if these are truly altruistic devices, or whether there are other commercial, political, economic reasons for their existance. Chickens will grow teeth before there is a 'World Mark' for electrical equipment, and those chickens will throw snowballs in hell before all mark issuing agencies have a common objective. Flames, please, to the agencies. Me?... I'm just a chicken with chewing gum and a sledge, waiting for the world to change. Chris Dupres Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.com with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, ri...@sdd.hp.com, or roger.volgst...@compaq.co (the list administrators).
Compliance Requirements for Therapeutic X-Ray Equipment
Hi Robert. You asked: Essentially, this equipment is covered by the EC Medical Devices Directive in Europe, and as such must comply with the relevant standard, EN 60601. This standard covers all aspects of medical equipment safety, electrical, mechanical, etc. so life is relatively easy in that particular respect. The standard needs working through though, lots of parts covering lots of subjects. You will be looking at the parts covering linear accelerators and simulators, all is there! Good luck. Chris Duprés Surrey, UK. - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.com with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, ri...@sdd.hp.com, or roger.volgst...@compaq.co (the list administrators).
Application of Directives
Hi Gail. You wrote: It's very simple, any goods placed 'on the market' after January 1st 1996 must comply with the EMC Directive., and any goods placed on the market after Jan 1st 1997 must comply with the EMC Directive AND the Low Voltage Directive. Existing products had to be redesigned if necessary, or taken off the market. In the UK the enforcing authorities did allow a period of grace for items already 'in the supply chain'. This was intended to allow any stock in warehouses to be sold without penalty, but that was a short term 'one-off'. Remember that the point of the Directive is to ensure that ALL goods placed on the market in Europe are built to the same standard so as to ensure that no state could refuse to take goods on technical grounds. To this end any goods which didn't meet the standards would be denied a market in Europe, or would be cheaper, in both cases the market place would be distrorted thereby creating an uncompetitive situation - exactly what the EEA is meant to prevent. A twopence worth, perchance. Chris Dupres Surrey, UK.
Safety at very low temperature
Hi Juan. You said: < Intuitively, I consider that it should be banned that somebody could touch a metallic tube at -100 ºC for safety reasons, but I have no standard requirement. > If you are building electrical equipment, then as long as you comply with the requirements of IEC 1010 or EN61010 then you can place a CE mark legally. If the standard doesn't quote a minimum temperature, then it need not be taken into account for compliance purposes. However, in operation, if someone is harmed by the equipment then they can sue you, ot you may be causing an offence under your local safety laws. But the CE mark exists primarily to ease free trade, not to prove safety or quality. Just an opinion. Chris Dupres Surrey, UK.
isopropyl alcohol
Hi Ned. You wrote: I use a material labelled 'Isopropyl Alcohol' for the rub test. That's what it says on the tin, and I can only assume that it is 100%. I am sure that it is 100% because spills evaporate very quickly and leave no water behind, I'm sure that if it was diluted the water would remain long after the IPA had gone. Does that make sense?. Chris Dupres Surrey, UK.
re: odd immunity problems ?
Hi Lisa. There are many urban legends of people who could 'fix' slot machines by using 'Phreak', 'squawk' and 'Blaster' boxes. These were allegedly small battery powered gadgets which produced very large amounts of EMI, sometimes as simple as a small unsuppressed electromagnetic buzzer, sometimes a wild HF square wave generator, sometimes a variable frequency spot frequency generator, or a combination of those. The principle was that a winning line was got up in the normal way, the Phreak box switched on, which locked up the processor or electronics, and from then on each pull of the (mechanical) handle obtained an identical win, regardless of the state of the wheels. Another system worked on the fact that one patricular machine always delivered a 3 plum win on switch on, as an automatic coin delivery gate check, so that the owner could be sure the machine was working properly. The phreak box reset the Switch On Reset latch after each pull of the handle and delivered a 3 plum win, whatever that was worth. The cure for most of these problems was a 0.1uF capacitor on the base of every BC108! Good old days Rumours abound of 'boxes' that could induce jackpot payouts etc, but it's always heresay, no hard evidence. Oddly, the machine manufacturers never seemed to put a great deal of effort into fixing these problems at the time. Construction was just plywood and chipboard with little screening in those days. Later microprocessor based machines seem to be effectively bomb proof,highly screened and grounded, but I am no longer involved in design of entertainment machines. Most 'hacking' activity nowadays seems to be pointed at ATM's, much more lucrative... I found details of how to interrogate these things with a hand held terminal on the Internet once! As they say, it's all there - somwhere. Chris Dupres Surrey, UK.
Security light problem
Hi Darrell. I've bounced your question to the group, mainly because it reminded me of how EMC affects every bit of our lives, even our personal habits No, I have to confess we just live with it now. We live with the condition that if we get up in the middle of the night to use the bathroom, when we turn the light on the fan timer starts. When we come out the fan will keep running for twenty minutes and when it turns off, the security light (infra-red triggered 500W halogen) will turn on for it's time period (15 minutes). Now you'll have difficulty believing this bit...Monty Python eat your heart out...Before the 500W halogen lamp we had a high pressure sodium lamp with an inductive ballast. When this switched off it would sometimes start the bedside radio. So the scenario was this. Get up at 2.00 a.m., go to bathroom, turn on light, turn off light, go back to bed, after twenty minutes a bright light shone through the window and woke you up. If you slept through that then when the light switched off the radio would start. The moral of this story? If you have bad EMC immunity make sure you use the bathroom before you go to sleep. Hope the beads work. This seems to be a common problem. Chris Dupres Surrey, UK.
Odd immunity problems.
Hi Keith.
As we wander round this world of Electro-fizz, pop and 2dB-over-limit, we
come across all sorts of strange EMC behaviour, some directly witnessed,
some without an actual source ("I heard of a friend of the wife of the chap
who reads the gas meters" - etc.)
A few more amusing ones have slippped into Urban Legend, or latterday
Folklore, some are much more recent.
1. There is the story of the lady on the ninth floor of a block of
flats who whenever she heated her milk for her bedtime drink, twenty
seconds later there was a loud 'Donk' noise from the wall. Subsequent
investigation showed that whenever the ladies Microwave was started, the
lift was called from the ground floor and stopped at the ninth. The ladies
kitchen was against the lift shaft and the noise was that of the lift doors
closing. - Unattributed
2. There is the story of the short-term car park gates at Gatwick
airport being opened simply by holding an electronic cigarette lighter up
to the exit card reader, and flicking it a few times. This was discovered
by careful TV surveillance, and the surveillance technician using his
lighter to see the time! Indirectly attributable to the BAA.
3. A metal detector on a coffee packaging plant dumping 50 lbs of
instant coffee into the scrap-sack whenever a CelNet phone was used within
20 metres.
Witnessed by Chris Duprés.
4. A Tissot Two-Timer digital/analogue wrist watch which went into
time travel mode (about x 60 )whenever a particular Motorola Micro-Tac
portable phone nearby had someone actually speaking into the mouthpiece.
Witnessed by Chris Duprés. It was my damn watch!
5. Motor Vehicles with Capacitor Discharge ignition systems stranded,
unable to run, parked on the A5 at Clifton-on-Dusmore, near Rugby, UK. The
fact that this road goes right through the middle of the NATO 16kHz
transmitter may have been significant. ( Is this EMC, or just total
overload?) Attributable to an AA patrol in The Halfway House Inn, Crick,
Northants, UK.
6. And there is the one where the flame on the gas cooker flared up
red and then went out whenever the phone rang... This was found to be due
to the telephone extension bell up the garden being fitted to the gas
supply pipe, such that whenever the bell rang the rust was shaken off the
inside of the pipe which got carried through to the flame causing the flare
up and then blockage. OK, this is not EMC per se, but it seemed funny
anyway. This was culled from a UK magazine, probably Readers Digest, while
waiting for the Dentist.
7. Lot's of other examples at home, including:
- The TV changing channels or turning off whenever the central
heating came on.
- The TV presenting us with the Gatwick Airport Meteorology
transmissions, albeit at very low level, when the Microwave was running.
(we are about 2 miles from Gatwick).
- A Ceramic firing kiln in the garage going up 10 degrees whenever
a switchmode battery charger was running in the garage.
- The outside Quartz Halogen security light comes on whenever my
office lights (fluorescent) or the bathroom ventilation fan are switched
off.
There must be many, many weirder and funnier ones out there.... :-)
Regards,
Chris Dupres
Surrey, UK.
Re: Copy of: Conducted Emissions Test
Hi Terry. You wrote: Good points. But a Video Camera and Power supply sold in the same box as a CE marked 'system' is likely to have a 2 metre/6' lead between the camra and PSU, and this I based my comments on. You are absolutely right to point out the 'antenna' effect of a long unfiltered cable, but the effect of that once above 30MHz resonance (1/4wave = 2.5M) on radiated emissions is unpredictable, and for that reason alone I wouldn't try to CE mark a camera that didn't include filters in the supply input if it was to be used with a long supply cable. I feel that a camera and power supply designed and intended to be used a long distance (>5 metres) apart would be difficult to include in the same CE declaration, and should really be tested and CE marked individually. However just about all applications such as this have short power supply cables and so this isn't really anything to lose sleep over I suppose. Interesting point, the equipment/d.c.power supply/ long wire thing, let's see if anybody else has any thoughts Anyone? Chris Duprés Surrey, UK.
Copy of: Conducted Emissions Test
-- Forwarded Message -- From: Chris Dupres, 100014,3703 TO: "WOODS, RICHARD", INTERNET:wo...@sensormatic.com DATE: 23/06/98 20:01 RE: Copy of: Conducted Emissions Test Hi Richard. You wrote: <. It is my understanding that the OEM must perform the conducted emission test.> There is no absolute requirement to carry out any tests at all! But whoever 'places it on the market' in the EEC must make a Declaration of Compliance that it meets the essential protection requirements of the EMC Directive, and that's difficult to support without evidence. < Since they do not market or specify a particular power source, I understand that they may test with any source that they may choose.> Yes, but that will not be included in the EMC declaration. Only emissions from the Video Camera are relevant, not the power supply. < I further understand that if my company markets or specifies a particular power source, it is our responsibility to ensure that the final combination complies with the conducted emissions limits. Are my understandings correct?> You can either use a Power Supply that is already CE marked and make sure you use it as the manufacturers describe, or you can supply both as a 'kit' which is described as such, and either you or the person placing it on the market in the EC must make a declaration covering both bits of equipment. If your power supply contains filters to attenuate conducted emissions from the camera, then you must state that the declaration only holds true when used with that particular power supply. Hope that clears the mud a bit. Chris Dupres Surrey, UK.
Copy of: Ground Wire Markings
-- Forwarded Message -- From: Chris Dupres, 100014,3703 TO: POWELL, DOUG, INTERNET:do...@ftc2.aei.com DATE: 23/06/98 19:48 RE: Copy of: Ground Wire Markings Hi Doug. You wrote: OK, I'm in the UK, but I've designed, built, supplied, installed and commissioned equipment in the USA. I have never come across any requirement that ground wires are not Green/Yellow (if that's what you meant), but I am invariably required to use UL or CSA wiring material that is marked with cross sectional area, voltage rating, UL or CSA description, maximum temperature etc. But this is nothing special, it's widely used material called either Thermoplastic Equipment Wire (CSA) or Appliance Wiring Material (UL), and the same stuff in the UK is called BS6231 Equipment Wire. Maximum current won't be marked as this is very dependent on how/where it is run, and what it is meant to do. Resistance won't be marked either as this is very temperature dependent. Cable with all three UL, CSA and BS approvals is named Tri-Rated, it's the same stuff. Another tuppence worth, maybe. Chris Dupres Surrey, UK.
Basic EMC Standards
Hi R.Heller. You wrote: < Are basic EMC standards harmonized? I have yet to see a basic EMC standard show up in the OJ. The 61000-4 series are widely used but are not in the OJ. What gives?> Basic EMC standards must be harmonised, that is the point of national legislation coverings such things. The generic standards are EN 50081 and EN50082. In the UK they are BS EN 50081 etc. EN meaning Euronorm = harmonised. You can only meet the requirements of national legislation if you comply with harmonised standards otherwise the Common Market principle will not be relevant. The 61000 etc series are based on IEC standards to which all European States are signatory, but in many cases I don't think you can claim compliance with them in order to apply a CE mark. The EN standards , though, do call up these standards in the 'Annexes' at the back so in that respect they are relevant. Another couple of cents worth of humble opinion. Chris Dupres Surrey, UK.
Poll, Changes to the EMC directive
Hi Petter. You wrote: What is meant by 'Functional demands'? Could you provide a bit more detail please. I have a very small brain and need all the help I can get Thanks. Chris Dupres Surrey, UK.
Copy of: Re: CE technical file format
-- Forwarded Message -- From: Chris Dupres, 100014,3703 TO: Mark Hone, INTERNET:m...@cjbdev.demon.co.uk DATE: 11/06/98 23:22 RE: Copy of: Re: CE technical file format Hi Mark and the group. The term 'Technical File' has been mentioned a few times. It's worth mentioning that under the UK EMC Regulations SI 1992/2372 the term 'Technical Construction File' is a formal term used to describe one of the legal routes to meeting the compliance criteria. The other two are the 'Standards Route' and the 'EC Type Examination Route'. The form of the 'Technical Construction File' is described in this Law (for that is what it is) in Part V, clauses 41-58, so there can't be much doubt about what that is as clause 43 is quite specific. TCF's are required to be verified by a 'Competent Body' appointed by HM government, and who will happily relieve you of a substantial quantity of Beer tokens for the privilege. However the semantically quite different collection of technical data and declarations which go to support a self assesment and declaration of conformity under the Standards Route is normally called a 'Technical File', and contains all the information that would be required to provide evidence of your compliance to a reasonably well qualified competent engineer. This may include, but not necessarily, emission and immunity test results, photographs of the equipment and test layout (if carried out), circuit diagrams, assembly drawings, installation instructions etc. etc. Competent Body qualification is not required of a TF, you go to jail on your own behalf if you deliberately seek to confuse. ThisTechnical File has to convince the Regulating Authority, in the UK the Trading Standards, and they are not at all stupid! Interestingly, there is no legal requirement in the UK regs to carry out tests, though how you convince people of your compliance with the standards without test results is an interesting diversion. Of course if you make a 100W resitive heater for fish tanks or whatever, the EMC risk would be quite low... and a simple declaration would no doubt suffice. (For these purposes I assume NO triac controls). So, don't mix your TCF's with your TF's. A tuppence worth, perhaps. Chris Duprés Surrey, UK.
Low Voltage directive and IEC1010
Hi Gary. You wrote: IEC 1010 and the LV directive is a long involved thing, and I spend much of my time advising people how to deal with it, unfortunately I'm on the wrong side of the Atlantic... What I would say is that 1010 doesn't only relate to Electrical Safety, but is a general standard describing safety in all it's aspects of equipment which is mains powered. I.e., it mustn't be too heavy, have sharp edges, give off fumes, catch fire, break easily, make too much noise, give off bright light, radiate damaging radiation (RF or nuclear), and presumeably if you eat it it shouldn't make you sick! Electrical safety requires either shock protection by double insulation to live parts, or by earthed accessible metal parts, in order to check this the standard consist of a whole load of 'Tests' which must be done and results recorded. Mechanical safety is fairly well described in the standard. What I do is go through the standard and make a list of all the relevant clauses, then make that list into a check list, and use that as the compliance statement. It will take a couple of hoursto comile the list, and allows you to ignore tests which are not relevant, e.g. the standard is very heavy on transformwer safrty, so if your equipment doesn't have transformers you leave all that stuff off of the 'check list'. British Standards have a draft 'Check List' in preparation, but it is incomplete and of course covers everything, including all the stuff not relevant to your equipment. If you have specific questions, feel free to ask. Good Luck, Chris Dupres Surrey UK.
Re: interceptor voltage stabilizer
Peter, David, Brian et al, et al. Peter, you wrote: The 'Voltage stabiliser', as it is known , is a very simple, but remarkable ingenious device. It is simply a bimetalic self heating device which has a switch contact operated by the bimetalic element. The contacts are normally closed, and the current flowing to the instruments causes it to heat up and it eventually opens. If the volts are low, the current is lower (Ohms Law - remember?) and the contacts remain closed for longer. Conversely if the volts are high the current will be higher (still Ohms Law) and the contacts will be open for shorter times. Thus the power/voltage applied to the instruments is kept fairly constant. The effect of the slow switching (about every 10 secs or so) doesn't have any effect on the instruments as they are bimetalic too, and have very long thermal time constants. That bit was the simple bit. BUT, because the instruments are indeed bimetalic, they are also affected by ambient temperatures, I mean a half full tank is a half full tank whether in 140 degrees F or in minus 40 (F or C). So the bimetalic regulator automatically allows for the ambient temperature, i.e. takes longer to heat up if it's cold, therby exactly allowing for the bimetalic instrument to also receive the extra bit of voost to keep the reading accurate in cold weather. The converse is, of course, true for hot weather. This works because the bimetalic elements in the instrument and the regulator are virtually identical. Making an electronic version is not trivial, the voltage stability is easy-peasy, but the temperature correction requires look-up-tables, design data, temperature measurement etc. etc. etc. I do electronic stuff for a living and I wouldn't even start. :-) Just a twopence worth of not-so-humble-opinion. Chris Dupres Surrey, UK. 74 JH
Twist on Connectors
Hi Ray. You wrote: These are the ceramic internal corkscrews, right? My answer would be that I would not design with these, and I would not recommend anybody use them. I've seen them used all over the world in various forms and I've never seen them fail, but then I've seen wooden houses, Ford Model 'T's and antique clocks all working perfectly, doesn't mean they are the best way to go. Crimped connections done with a proper tool are absolutely repeatable, and infallible. My dog could do a good crimped joint if I put the tool in his mouth. Twist on connectors joints are just too variable in quality, depending on grip strength, oily fingers, thickness of strands, anneal state of the copper, how much wire has been stripped, etc. etc. To meet IEC1010 the tracking and air distances would have to be better than minimum, something not predictable with twist-on's, particularly if they are subject to some pull, when they unwind a bit. If I told a Law Court or Insurance Company that we used these things to save a few cents, there would be a hushed silence before they pulled the lever. Why stop there? Why not use cotton wound insulated wire, or Vulcanised India Rubber mains cables, they were great in their time, but modern materials and methods have made them obsolete, not failures, but obsolete. In the States I saw a chap throw away the DIN standard 40 amp terminal blocks we provided in a motor casing, and wind the feed and motor winding tails round a bolt which had a washer and nut run on, tightened, then wrapped in PVC tape. The chap explained that 'He couldn't be doing with the terminals, he wanted the two wires to actually touch'. To my ultimate shame I couldn't think of anything to say. Just a few not-so-humble self opinionated cents worth... :-) Chris Dupres Surrey, UK.
Positive Guided Relays
Hi Prior. You wrote: < A client uses PONZ-1 relays in a safety circuit for packaging machinery. This circuit has been approved by US & EU agencies. He would like to change to EE Controls positive guided relays. The circuit would be re-evaluated with the EE Controls type SH0! 4 positive guided relays. His questions is "what are the chances of these EE Control relays being approved?" He does not want to present the circuit to an agency for evaluation without some assurance that these relays are acceptable.> US approval and EU approval may well be in relation to quite different things. PNOZ relays enable Guard and Emergency stop circuits to comply with the EU Machinery Directive safety requirements, but id they comply with a US agency, this is probably not related to the very high integrity guarding requirements of the EC, but more to do with UL approvals. (fire and electric shock protection) I don't know the EE Controls relay, but if you are evaluating these for interlocked guarding systems you should not only consider the 'guided contact' attribute, but also the 'dual redundency' attribute that will cause the system to be safe in the event of a single fault. PNOZ relays have a dual input which provides this level of protection, many simple guided contact relays do not. A two cents worth, maybe... Chris Dupres Surrey, UK.
Re: EMI Site Interference
Hi Scott, You wrote: 1 GHz, at levels up to 70 or 80 dBuv. It is not like a flat carrier but > rather more like PWM driven motor noise. It lasts from 15 seconds to 1 > minute in duration. Then ambient returns to normal.> I've had a very similar problem, 20-30dB over limit, wideband from 30MHz to 1GHz. Once was continuous, and was found to be a fluorescent fitting in a corridor about 60 feet away inside the building. Another incident, with identical EMI characteristics, but happening about 4 times a day for durations of 1 to 2 minutes, was traced to a fluorescent fitting in the Secretaries toilet! The source may be closer than you expected. Just a suggestion, Chris Dupres Surrey, UK.
Copy of: CE Technical Documentation
-- Forwarded Message -- From: Chris Dupres, 100014,3703 TO: "Farnsworth, Heber", INTERNET:hfarn...@physio-control.com DATE: 24/03/98 22:24 RE: Copy of: CE Technical Documentation Hi Heber. You wrote: In the UK Electromagnetic Compatibility Regulations SI 2372/1992, the only term that is specifically mentioned is the title of Section V, the Technical Construction File. The content and structure of this document is described in the Act, and this is the document which is used to provide evidence of compliance under the 'Technical Construction File Route'. Any other sets of technical documentation used to support claims of compliance under the 'Standards Route' should be labelled 'Technical Files' or 'Design Files' etc. Hope that helps, Chris Dupres Surrey, UK.
Automobiles and CENELEC?
Hi PSTC Folk. Not a strictly EMC or Safety question, but could be... European Automobile components such as relays, switches, etc. have terminal markings that are rather similar to the CENELEC markings found on relays etc. used on many switching components used in Europe. CENELEC markings have the first digit as 'contact group number' and the second number to describe function, i.e. 1-2 = NC, 3-4 = NO, 5-6 = 'special function' NC. and 7-8 = 'Special function' NO, such tht contacts on a relay may be 11-12, 21-22, 33-34, 43-44, and delay close contacts be 57-58, etc. But the similar markings on Automobile components have, on single contact components, numbers such as 80, 80a, 30 and so on, which seem to be out of line with the 'rules'. Can anyone enlighten me as to where these component markings originate, I'm sure they are rooted in DIN somewhere, but a standard number or document reference would be nice. Many thanks Chris Duprés Consulting Engineer Surrey, UK.
emc-pstc@listserv.ieee.org
Hi Alan. You wrote: < unfortunately you do not declare your organisation maybe knowledge of this would help.> Yup. Mea Culpa... I've been active with this group for about three years now, and I get lazy. I'm in fact a 'Compliance Consultant' and work with people all over the world supporting their activities in achieving compliance with the Euro LVD, EMC and Machinery Directives. I have no 'organisation' apart from myself in that respect. >From todays mail I note that not many other people seem to have an opinion on the matter, I suppose we can take that as an unqualified 'approve'? Good luck. Chris Dupres Surrey, UK.
emc-pstc@listserv.ieee.org
Hi Alan. You wrote: Just a comment... or two. This mailgroup is a self-help/mutual support Forum with members all over the world who have a common interest in compliance matters. It has a strict non-commercial philosophy and using the content for commercial advantage is, I believe, against the principles which are the backbone of the group. Tom Bao, of the Regulatory Compliance Information Centre (RCIC) is an avid supporter of this group and publishes on the 'Net a full listing of the traffic that appears on this group. I may be wrong, but I think there is a connection to Compliance Engineering magazine, which is in the same market sector as yourself. We would value, as No.5 said, 'More Input' rather than more output. The group is succesful because of the people in it, from all over the world, who give their accumulated knowlege freely. If your Q%A's include the Groups Email details and instructions on how to join then that may be a valuable addition to the Groups membership, though each applicant is vetted by the relevant IEEE committee (I believe). My feeling is that the more 'Question Answerers' we have, rather than 'Question Askers', the more valuable the group. If your Q&A's generates more Answerers, then that may be a good thing. Just a few humble, simple, thoughts... maybe a tuppence worth. Chris Dupres Surrey, UK.
CE question
Hi Lisa. You wrote: < I have a question regarding a unique piece of equipment to be shipped to the EC. It is is a training system used specifically at schools for vacuum training courses. Several components which make up this system are CE marked while a few are not. My question is "Is there an exception to the the EMC/LV directives which allows such training products to be shipped without compling?" If so, what and where? and also, what paperwork would be required to accompany the equipment? > There is some confusuion around 'Educational Equipment' inrealtion to CE marking. The UK EMC Regulations state: Part II, Application, Clause 8, 'Educational Equipoment'. 8.-(1) In the application of these Regulations to educational electronic equipment, a reference to the protection requirements - a) in so far as it relates to the electromagnetic disturbance generated by that equipment, shall be construed as a reference to the elctromagnetic disturbance capable of preventing relevant apparatus situated outside the immediate electromagnetic environment of that equipment from operating as intended; and b) in so far as it relates to the immunity of that equipment, shall not be taken to refer to any susceptibility to electromagnetic disturbance which is a necessary feature of that equipment to facilitate the study of the effects of electromagnetic phenomena. (2) In these Regulations, "educational electronic equipment" means apparatus designed or adapted for the purpose of its being studied for electromagnetic phenomena in any educational, training or research establishment. --- This is saying that in the UK, you can supply or use equipment that is designed to be susceptible to EMI, but you can't emit EMI. And that the susceptible equipment must be used for investigating EMI phenomena, and not, for example, measuring vacuum with capacitive manometers etc. Anything placed into service in the UK must be CE marked, and therefore be compliant with the relevant standards. Hope that helps. Chris Dupres Surrey, UK.
Ground Hog Day.
Hi EMC and safety folk. Is it me, or is something re-sending a load of mails from the group over and over again. I clear my mail box, and during the next few hours a whole load of mails dated 20 Feb re-appear in my box. I clear them, and it happens again. I've received the same mails on FCC stuff and CTI about five or six times thus far. They were interesting the FIRST time! Anyone else getting this phenomenon? Chris Dupres Surrey, UK.
RE: FCC Questions.
Hi Gert. At the end of your interesting response you said: I've worried about this. The Euro rules are in place, as I need not remind you, (but the left hand side of the Atlantic mayneed a reminder), because of the Treaty of Rome in the '60s which brought about the need to get all Euro products to the same technical standard for the purposes of Free Movement Of Goods across borders within Europe. i.e the Common Market. The primary reason for the Euro EMC rules being there is therefore political/trade related, and not the need to reduce EMC emissions - though that is not a bad thing. The USA and other countries round the world have quite different reasons for introducing EMC controls, some of which may protectionist, some born of the need to keep interference down. The reasons are many, and because of this technical standards have a different bias. In order to trade with Europe, the USA and others will need to climb over the CE walls of Fortress Europe which they will almost certainly do, but I doubt that they will need to go as far as, for instance, BSEN 61000-3-2, and -3-3. Harmonics and dips, for their own internal purposes. Just a thought... Chris Duprés Surrey, UK.
Responsibility for DoC
Hi Jim. You asked: < Who is the responsible party for issuing the declaration of conformity with the EMC and Low Voltage Directives? > In the UK we are covered by law thus: 1. The Electromagnetic Compatibility Regulations, Statutory Instrument 1992, No. 2372 Part IV, Clause 40.-(1) 'This regulation shall have effect for prescribing the form of an EC declaration of conformity issued IN THE UNITED KINGDOM in respect of relevant apparatus in relation to which the conformity assesment requirements have been complied with pursuant to the standards route to compliance.' (My caps) It implies that the certificate should be raised by your re-seller in the UK. 2. The Electrical Equipment (Safety) Regulations 1994, Stautory Instrument 1994, No. 3260 Clause 10. 'Subject to regulation 12 (2nd Hand equipment) the MANUFACTURER of electrical equipment OR his AUTHORISED REPRESENTATIVE shall draw up in respect of all electrical equipment to which these Regulations apply a written declaration of conformity which shall comprise:-' (My caps) It implies that you or your re-seller can raise the certificate. 'Authorised representative' is strictly interpreted in clause 3 as: 'means a representative established within the Community appointed by a manufacturer of electrical equipment to act on his behalf in relation to these regulations.' Hope that helps a bit. Chris Dupres Surrey, UK.
Re: Shielded power cord, seeking source for
Hi Tim. You wrote: My problems have been that filters are often guilty of resonances at particular frequencies, providing substantial gain rather than attenuation. With 'white noise' things like phase angle controllers in the box, these filters put (in one instance) 32MHz out on to the mains cable, which radiated beautifully. The screen was sufficient to drop those emissions by about 15dB, thereby bringing it back into compliance. The transmission line characteristics of screened three core cable are very poor, and the conducted emissions of the 32MHz past the mains lead were clearly very much reduced by the inductance/capacitance of the cable, in that the -15dB results were perceived. The radiated emissions included those from the mains supply to the equipment. The mains cable on this thing was 3 metres long, and made up from component's, not moulded. The screen was grounded at the Supply end. Interesting stuff... Chris Dupres Surrey, UK.
RE: Notified or Competent Body?
Hi Mel. You wrote: Yes, it can be. We have three routes to compliance, according to the Electromagnetic Compatibility Regulations. Statutory Instrument 1992/2372. Which is the law in the UK governing such things. 1. Part IV Descrbes the 'Standards Route', where you build to the relevant standard, and sign a declaration (self declare) that you have done so. This normally requires proof in the form of testing, but a statement may suffice in the case of, say, a simple heating device. 2. Part V describes the Technical Construction File route, where a Competent body will qualify your own, or generate a file which adequately describes the equipment and design processes, together with test results etc. This can be used where suitable standards don't exist. 3. Part VI describes the EC Type-Examination route, which is for radio comms equipment, and is compulsory. Route 1. above is cheapest and most risky, Route 2. is safest and most expensive Hope that's interesting, Chris Dupres Surrey, UK.
RE: Shielded power cord, seeking source for
Hi Rick. You wrote: Not as far as I am aware, and I have been designing mains powered stuff since I was too young to know better... But then I'm not aware of any manufacturers of Moulded Screened Mains Cable assemblies, they are invariably home made. Screened mains cable is freely available on the reel (in the UK from people like RS Components for instance) and I have used it when I have had problems with radiated emissions or susceptibility on long mains cables. Usually when a filter demonstrates a particularly arkward resonance. Any component which is safety or EMC critical, and which may be changed by a subsequent user can be made a condition of compliance by a relatively simple statement in the instructions. i.e. under the general heading of 'Using as intended'. Use of the equipment without the particular cable is therefore 'Not as intended' and therefore shouldn't be expected to comply (and shouldn't be put into service). A thruppence worth perhaps. Chris Dupres Surrey, UK.
EMC test for travel iron
Hi Raymond. You wrote: I would opine 'NO'. When this gadget is in use it will be used in a domestic environment, hotel toom, washroom, wherever. Unlike a power tool which will be used everywhere there are 'things to be done'. The fact that you carried it there is not relevant to it's EMC performance. I would definitely call it a Household Appliance. Also, I wouldn't worry too much about testing for harmonics if it is only a resistive heating element with mechanical thermostat, i.e. no non linear devices. I would be tempted to describe it in your techy documentation as EMC benign. ( Unless of course the product has built in solid state temperature control, and that would be a very dodgy product in terms of electrical safety without a contact backup.) A humble opinion, a couple of pence worth perhaps. Chris Dupres Surrey, UK.
Copy of: Official Journal
-- Forwarded Message -- From: Chris Dupres, 100014,3703 TO: "Flinders, Randall", INTERNET:r_flind...@emulex.com DATE: 18/12/97 06:33 RE: Copy of: Official Journal Hi Randy. You asked: The OJ is published daily, and contains EVERYTHING related to the business of the European Communities that happened the previous day. It's very big I doubt very much that it is available on a web site, it would be a monumentous task updating it on a daily basis. < Also, I am currently looking for a service which can keep me updated on changes to the OJ and the Norms. > ERA Technology of Leatherhead in the UK (branches in the USA) publish regular reviews of worldwide standards and compliance information. 'Standards Update' and 'Safety and EMC'. They are obtained by subscription and I have found these to be invaluable. I have no connection at all with them, but am glad to recommend them. ERA Technology Ltd. Cleeve Road, Leatherhead, Surrey KT22 7SA UK. tel +44 (0) 1372 367030 fax +44 (0) 1372 374074 Email i...@era.co.uk Hope that helps, Chris Dupres Surrey, UK.
Re: CE & Demo Units f.u.
Martin et al... Sorry about dragging this out a bit, but the comments : We need to remember that the EU Directives were born of the Treaty of Rome, which is a treaty which relates to Trade, and removing barriers to Trade. EMC, LVD, Machinery, Low Pressure, Toys etc. etc.all have directives which seek to level the playing field, and ensure that no one European Economic Area (EEA) state gets a trading advantage over another EEA state by selling products which have lower technical standards. By adopting the same standards (the Harmonised standards) all EEA states offer the same level of basic technical performance in terms of intrinsic common impact non-commercial characteristics like safety, EMC etc. Demo units are not placed 'On the Market', but are 'Placed into Service', which is an equally valid reason for compliance. It follows that if you knock up a bit of testgear for yourself, or a quick prototype for demo it should comply, in as much as if it causes interference, or an electric shock to a person or domestic animal, then an offence has been committed. The same with a prototype on an exhibition stand, or at a customers facility, it should comply or have a bluddy good reason why not. It need not be CE marked however, which is the mechanism by which the 'Free Trade' objectives are met, and clearly not relevant to something which will not be traded. I'm reliably informed that enforcement officers prowl exhibitions, particularly in Germany, with equipment which will identify wild non-compliers, and invite the equipment to be switched off, often with a legal prohibition notice. Prosecutions are unlikely, but if you can't demonstrate it at an exhibition you might as well have a cardboard box with knobs painted on. In reality you are not likely to be 'caught' during a customer demo, but your conscience may stop you sleeping.. :-) I suppose the route to take is simple, if you are going to demonstrate something at a customers site or an exhibition in the EEA, put screening, filters and screened cables on everything, and point it out as a major selling point. "Even the prototype is CE compliant!". A tuppence worth, maybe. Chris Dupres Surrey, UK.
Re: (off topic) GFI history.
Hi Hans. You wrote: < I had read once (long ago) that fribilation would occur starting at 7 or so mA in a statistical significant portion of the populace. To hear 30ma is surprising!> I'm not a Doctor, so I have to go to learned tomes for my data. This time I used the IEC document "Effects of Electric currents on human beings", the IEC number which I don't have to hand, but I can find it if you want it. This is a morbid, but very enlightening document which goes into significant detail about currents, times, heart phases, heating, voltages, etc. etc. A torturers almanac no less. The forward describes how they got the data for publication. Bleaahh! The same data appears as a reference chart in the UK Machinery Guarding standard, BS5304. In each case the current which can cause the onset of Fibrillation is given as c. 30mA at 50Hz. In the UK we tend to have only one non-electronic RCCD in our houses, and this is usually on the main incomer to the house. Spur circuits to garages and garden equipment should be connected by an RCCD, but this is not a legal requirement. The nuisance problem is primarily due to h.f. oscilatory currents in mains leads etc. coupling to earth and providing sufficient imbalance to the summing coil to cause a trip. As the UK RCCD's are non-electronic, they are not frequency selective! Nowadays they have copper slugs/shading pieces and stuff to slow down the response for a cycle of mains, this seems to have pretty well stopped nuisance tripping. We have electronic RCCD trips which are plug-in devices through which we power lawn mowers etc. The one I took apart (it started to smoke!) had an RC circuit of about 100mS to prevent nuisance tripping, it still tripped when used with long leads sometimes. Chris Dupres. Surrey UK.
Re: (off topic) GFI history.
Hi Rich and a few others on this topic. you wrote: In the UK we use 30mA for people protection on RCCD's, this is because the onset of ventricular fibrilation will occur with a very high level of probability at currents flowing around heart muscles above this. 50/60Hz is about twice as dangerous as d.c., it being the Change of Current that has the physiological effect, i.e. d.c. is dangerous above 60mA. (I'm ignoring I^2R effects for this purpose). The danger is also related to the actual time the current is flowing, and particularly relevant to the moment in relation to the actual phase of the heart beat. I.e. it's quite possible to be hit by lightening and just walk away, albeit with your trousers on fire. Electronic RCCD's are not used in the UK because of their lack of intrinsic safety, i.e. safety is related to fallible electronic components, and also the increased sensitivity can cause nuisance tripping when highly inductive loads are switched on, the most common being the trip that feeds the freezer switching off when the food gets too hot! The rationale being that it's better to have no RC protection at all, than rely on RC protection that may have failed. A tuppence worth I think, certainly no more... Chris Dupres Surrey, UK.
Robin Instruments
Hi Raymond. Looking at a catalogue on my desk right now, they are available from: RS Components Private Ltd., 39 Ubi Road 1, #03-00 World Publications Building Singapore 408695 tel +65 291 fax +65 382 6766 RS Components Ltd., Wyler Centre, Phase 2, 13/F, No 200 Tai Lin Pai Road, Kwai Chung, N.T. Hong Kong, Tel +852 2421 9898 fax +852 2421 0339 RS Components also have outlets in India, Auatralia and New Zealand.. RS Components International, in the UK (head office) is on: tel +44 1536 201234 fax +44 1536 204237 They can probably help you further. Hope that helps. Chris Dupres Surrey, UK.
RE: Antenna Calibration/Site Attenuation
Hi Cortland. You asked: <(As an aside, can anyone here say if the COmmission has ever specifically ruled on how far away from residences Class A equipment must be kept? > In my meanderings around the Compliance Biosphere, I've spoken to many enforcement people, competent bodies, even Government administrators. The general opinion seems to be 'If you meet the general intention of the Directives via the Standards, then the world will be a better trading place'. Note the deliberate absence of the word 'distance' and 'field strength, and 'interference'. In general, the advice I live with, and give, is that you shouldn't expect a TV to work perfectly on top of a Microwave cooker, and you wouldn't expect an electric pencil sharpener to reverse if you use a portable phone nearby. I feel that in any one typical domestic situation, the RF signature of a location is so far removed from an OATS or screened room as to be almost meaningless in practical terms, but you gotta put some rules down somewhere. I akin it to judging how fast a car can go by the shape of the hub caps. (They only put Hot Hub Caps on fast cars?) I had a case of a TIG welder interfering with a VHF radio some 200 metres away, awful wide band hash whenever the TIG fired up. I've also had Quadrupole Mass Spectrometers (pico and femto amps) behaving perfectly when 600mA 2kV Argon Arcs are being started in the same vacuum chamber. In answer to your question, I'm not aware of any requirements for distances between emitters and receptors, notwithstanding that there may be local by-laws which prohibit people camping beside arc furnaces, or something. In the UK, if you regularly get nuisance interference from anything at all, one can approach British Telecom, the monopoly holder, who will investigate and find the source of the intereference, and politely suggest to the source that they do something about it, but I'm not sure what teeth they have. The point is, is that they don't seem to take distance into account. It's all to do with the Wireless Telegraphy act, I think. That should be as clear as mud... Chris Dupres Surrey, UK.
Which EMC Directive Standards might apply here?
Hi Bob. You wrote on 19th March. I think that this defaults to EN50081 / EN50082, the Generic EMC standards, the Goop Agitator standard hasn't been published in the OJ yet. It probably isn't isn't ISM equipment (EN55011) because it could also be used for making cakes presumeably - or maybe a cup of tea - and it doesn't use RF. You need to make a decision as to whether it is used in an Industrial, or domestic/light industrial environment. The primary criteria for that choice is whether the place it is likely to be used is on a 'street' supply, or in an establishment which has it's own transformer and local distribution. It's not important to whom you sell, or supply it, it is only relevant that it is placed on the market, or placed into service. If it leaves you and goes to Europe, it must have a CE mark and certificate to back it up. What LVD standards do you meet? Chris Dupres Surrey, UK.
Three phase wiring.
Hi Phil. You wrote: Basically, in the UK three phase distribution in a building is Red/ Blue/Yellow (IEE Regs) Three phase inside a Control System for a Machine (BSEN60204) is Black, and single phase live wire is Brown. Neutrals are all blue, but under BSEN60204 so is D.C. power, so you need Dark Blue, and Light Blue sometimes. The cable that connects from the wall distribution to the Control main isolator is in a bit of a grey area, my own attitude is that the RBY stops at the wall socket/terminal box (6491X cable), and Black starts at the free plug/tails (BS6231 or Tri-rated cable). That might help a bit. Chris Dupres Smallfield, Surrey
X-Caps
Hi Richard. Sorry, I'm a bit late with this. You wrote: < Must the cap be X-rated in this particular application? In general, when does a cap connected to the mains no longer need to be X rated?> Basically, an X rated cap is one that can safely be placed before the inlet overcurrent protection because in the event of a short circuit, it heals itself, and is therefore not going to need protection. So, any caps connected before your first fuse or MCB should be X types, or Y types, depending on where connected. (Y's go to earth). Hope that helps. Chris Dupres Surrey, UK.
EFT testing of three phase industrial equip
Hi James You asked: I've been using the Schaffner EMC equipment with some success over the last few years with some success. Chris Dupres, Surrey, UK.
Graphics in Posts. Signatures.
Good folk of the EMC-PSTC. 1. Graphics. My Email is all managed by my Compuserve connection, and that now automatically, seamlessly (their word), and transparently (my word) decodes anything that comes in very succesfully, I simply get a screen message that xxx file is save as in the DOWNLOAD directory. It uses the MIME protocol, recognises most encoding, and - so far- is totally useful and succesful. I have a 28.8 phone connection, and simply click on the 'GET ALL' button and downloads, including all graphics, texts, WAV's, dogs, chickens and the smell of a pink rose at dawn rarely take more than 2-3 minutes to complete. I typically have 30-40 mails waiting when I connect. On a good day, simple text files complete downloading in 20-40 seconds, and it dials up, and hangs up in less than a minute. 2. Signatures. Compuserve (WinCim 2.6) doesn't have a facility for auto signatures, and I would spend a day typing out Email addresses, post adresses, phone numbers, dates, jokes, etc. on each mail I send/reply to, so I rely on the mail header (picked up by just about all mail software when the REPLY button is pressed) as my route back to me. One thing I do do, is add my geographical location to my signature, that has to be sensible. I dont supply my full address as I don't want Claudia Schiffer and Jennifer Aniston to find where I've moved to. On a world-wide forum such as this, we have submissions from all over the world, and probably some from Mars as well, and it puts a perspective on things if we know the source of the comments. Just an unsolicited bar of chocolates worth from the UK. Chris Dupres Surrey, UK. Email: chris_dup...@compuserve.com tel: +44 (0) 1342 843154 fax: +44 (0) 1342 844219 mobile: +44 (0) 831 785514 page: +44 (0) 839 495284 in car pager +44 (0) 336 707070 ident No. 128163 Technical Manager, Scancard Inspection Systems Ltd., 8, Westminster Court. Hipley Street, Old Woking, Surrey GU22 9LQ UK Tel: +44 (0) 1483 728230 Fax: +44 (0) 1483 768815 Email 73041.3...@compuserve.com <> Home page: http://ourworld.compuserve.com:80/homepages/chris_dupres/ etc. etc.
Copy of: reduction of leakage current
-- Forwarded Message -- From: Chris Dupres, 100014,3703 TO: INTERNET:mvald...@netvision.net.il, INTERNET:mvald...@netvision.net.il DATE: 7/16/97 7:11 AM RE: Copy of: reduction of leakage current Hi Moshe. You asked: A simple, but expensive and bulky, method is to simply fit a good isolation transformer to the input, (I assume you are describing mains powered equipment). Another advantage of that is that conducted emissions are often reduced and can allow you to use a smaller filter, or even remove it altogether! Otherwise, as the only components you have connected to your mains input can't be changed, your choices seem to be, in a word, almost zero! (Sorry, two words.) Hope that helps a bit. Chris Dupres Surrey, UK.
Brazil stuff.
G'day folk. Can anyone give me a quick review of the EMC/LVD/Machinery requirements for equipment destined for Brazil? The equipment is Automatic Machinery, packaging lines, and would be made in the UK to EEC Directives. Any information would be very much appreciated. Chris Dupres Surrey, UK.
intrinsic safety requirements
Hi Mel. You asked: Intrinsic Safety is pretty well as you suggested, devices operating at such low power that they are 'intrinsically safe'. It's related to ignition of flammable atmospheres, primarily in the Oil and Gas industries, but also on any system which uses flammable materials such as flour dust, alcohol, etc. etc. The rationale is that you keep the maximum possible energy dissipatable in a fault to below that necessary to cause ignition of a flamable atmosphere. This is done by things called Zener Barriers and Safety relays which have very low excititation circuits. Zener barriers are essentially a network via which EVERYTHING in the flammable area is connected through (the ZB's are in the safe area). The ZB's limit the maximum voltage on the hot side, and series resistors limit the maximum current such that in an Open Circuit or Short Circuit fault the let-through energy is limited. High Voltage stuff, motors etc. are cabled up in high quality cables and conduits which are gas proof etc. and have cast junction boxes with wide metal/metal joint faces such that inthe event of an explosion within the motor/box the flame propagation is limited by the gas having to squeeze through a very small gap between cooling metal, and the cases so thick that they won't burst. In the UK etc. these things are built to Baseefa requirements, and have labels marked Ex or EEx. People such as Measurement Technology Ltd. in the UK specialize in such equipment and have an excellent set of (free) Application reports that describe things much better than I. I'm sure others on the group will give you much more information, hope that helps a bit. Chris Dupres Surrey UK.
USA 72 Mhz model radio control equipment
Hi Paul. Lots of questions, but one that struck home with me: < - CE EMC requirements are not applicable to Radio Control equipment (for me its applicable to ALL equipment's, what's your opinion?)> Radio Control, like CB and ISM (Industrial Scientific and Medical) frequencies do not usually have limits to emissions, and don't usually have immunity requirements. The ISM frequencies are specd (in the UK) at 13.56 MHz, 27.2, and harmonics upwards, and I think I'm right in saying that there are no limits to emissions WITHIN THOSE FREQUNCY BANDS... ISM, CB and RC equipment emits RF, that's what it does, that's what it's meant to do, if it didn't it woulldn't be working. So, the rationale is that anyone can do what they like in those frequencies, but don't complain to the authorities if then band is already full of interference. It seems to me that the Radio Control, CB and ISM frequencies are the interference dustbins of the RF world, and you use them at your peril, it follows that subjecting such equipment to EMC rules would be quite innapropriate. I assume, of course, that your equipment operates ONLY at the marked frequency, with a bit of distortion to produce odd and even harmonics, but that your stuff doesn't have FM, or sidebands, or parasitics that would create emissions OUTSIDE the ISM bands. A couple of Euro's worth? Chris Dupres Surrey, UK.
shop's neon sign (lights)
Hi Robert. You wrote: For my money, you are on the right track with 55015. This standard makes allowances for the fact that lamps which use Ionized gases as the light source often behave badly on start up, and I think the standard allows 5 minutes running for the lamp to 'settle down' before measurements need be taken. I used that standard to qualify a very low pressure high intensity UV source used for metal surface analysis - now THAT was nothing like a domestic lamp, but did behave very badly while it sorted it self out, vacuums stabilized, temperatures got high enough and the rough edges of the internal metal parts got etched away! Luminous signs are usually neon or a rare gas, and after switch-on must behave a bit erratically, at least until they warm up and reach a stable operating condition. 55015 allows for this. Good luck. Chris Dupres Surrey, UK.
New guy
Hi -joArnold. Welcome to the Group. Here you will find Wisdom, joy, humour, and the occasional bit about Jensens! ... and people selling real estate in the Everglades, which brings me on to the subject you alluded to in your mail. Zapor Charger. I am wary of people who use words like "It is based upon a new set of physics principles in the unified field theory." when selling hardware. I may be wrong, I've only been in Electrical and Electronic Engineering for 25 years, but I've never come across a charger of that ilk, that can charge telephone batteries in seconds without it getting hot.. But, as he says, it's a new invention, and so was that guy who sold a gadget to let your car run on tap water. Agnostics rule.OK. :-) Chris Dupres Surrey, UK.
Re: Interlock - PCB Spacings -- OPINION PLEASE
Hi Bob. You wrote: You are quite right of course, but the point I allude to is... the final device which stops the motorised flailing blades is a contact! I know of no solid state devices that I would use to make a dangerous motion 'safe'. Many guarding systems use statistically sound methods with solid state sensors providing data to a machine guarding system, but the thing that stops the motor is necessarily a couple of bits of metal which are pulled apart in a contactor. I don't think that solid state devices, SCR's, Triacs, whatever, can be described as intrinsically safe, in the same way that MCB's can never be as failsafe as a simple fuse. i.e., fuses can only fail, but MCB's can get stuck, break, weld, catch fire, etc.etc. I use guarding systems which are intensely electronic, for instance the voting logic in Oil and Gas fire protection systems, but the thin part of the hourglass, the actual power control device, is always a couple of contactors, contacts in series, coils in parallel, with cross wired auxiliaries to detect a welded contact. These contacts are my primieval safety...When the guard is opened or the Emergency stop button hit, these contacts open, and the electron that can get across that air gap is named Houdini. Just a twopence worth.. Chris Dupres. Surrey, UK.
Interlock - PCB Spacings -- OPINION PLEASE
Hi Israel. You wrote: ---snip--- < The Interlock protects against severe mechanical and laser radiation hazards. The interlock system comprises of circuitry implemented on PCB.> ---snip--- < Components (Integrated circuits) that comprise the interlock system have pin spacings of less than 1.2 millimeters.> ---snip--- Wow, you are using semiconductors for an interlock system! Maybe I misunderstand what you are doing Surely an interlock system for a system with hazards as you describe requires a level of intrinsic safety way ahead of board level electronics. The failure analysis would list far too many modes of failure that would allow your interlock to be compromised. An interlock designed for compliance to the Euro Machinery Directive, etc. etc. would require a minimum of two independently powered relay contacts in series, with cross connected contacts to detect a seized relay and prevent re-energisation. Two 3mm airgaps in series (open relay contacts) are orders of magnitude more reliable than anything laid down on a non conducting plane like a pcb, when the degree of pollution on that material is unpredictable under any conditions. Interlocks need to be intrinsically safe, i.e. will always fail OFF in the event of a faultAny fault, including a spider crawling across your pcb, or electrolytically grown trees across your conductors in high humidity, or a solder splash, or whatever, will cause your interlock to be negated. Semiconductors are best avoided like the safety plague they are in interlocks. They fail in quite unpredicable ways, sometimes S/C, sometimes O/C, and for a multitude of reasons. Safety is two bits of metal separated by a nice air gap. Safety is not a PN junction a couple of microns thick that happens to be missing a few free carriers, on a bit of insulating material that is the perfect vehicle for conductive media such as water, dust, corrosion effects, dirt generally etc.to accumulate on. I'll get down out of my tree now, interlocks and intrinsic safety is a bit of a hobby horse with me. Have a good day. Chris Dupres Surrey, UK.
gfc's and vacuum cleaners
Hi Eric. You wrote: We don't call them GFC's.We call them ELCB's (Earth Leakage Circuit Breaker) or RCCB's (Residual Current Circuit Breaker) or RCD's (Residual Current Device). Apart from medical use, which is <1ma, our normal trip values tend to be : 30mA - Personnel protection. 100mA - Electrical integrity protection. 300mA - Fire protection. The 30mA may also have intrinsic delays built in to prevent 'nuisance tripping'. a) The Low Voltage Directive 72/23/EEC b) The Electromagnetic Compatibility Directive 89/336/EEC c) The CE Marking Directive 93/68/EEC Surprisingly, vacuum cleaners do suffer immunity problems with EMC. Many have variable speed controls (Suck Control) and the Triac circuits which control the motor are susceptible to mains borne noise. We have an old Electrolux VC which when in use 'kicks' when the kitchen fluorescent lights are switched on... These same Triac controllers put out copious amounts of conducted emissions. This is why I have to explain to my wife that I can't possibly do the cleaning because I am morally bound not to make EMI. Hope that helps. Chris Dupres Surrey, UK.
LVD and standards listed on the OJ
Hi Martin. You wrote about LVD and PLC's. Don't lose sight of the fact that the LVD states that the equipment as described should be safe. EN61010 (measurement and control equipment, which may loosely describe PLC's) requires that the equipment should be safe in all interpretations of the word. i.e. that it shouldn't be too heavy, have sharp edges, mustn't be too loud, too smelly, too hot, mustn't fall over, mustn't break, etc. etc.. In short, shouldn't cause damage to people, property or domestic animals. Protection against electric shock is mentioned, but they don't make a big thing of it. I'm not terribly clear as to whether EN61010 is mutually exclusive to EN61131-2, or additional to. I tend to treat them as mutually exclusive, otherwise you'd spend your life chasing standards, and in many cases they are conflicts. Probably not, but if they do they should give you the clauses that you must comply with. If the PLC is used in a machine control system, it should comply with the Machinery Directive, EN60204 is more relevant here. If used in a measurement system, use EN61010. What none of these standards mention is that if you eat a PLC, it shouldn't poison you That would be a non-compliance with the LVD! Hmmm. Chris Dupres Surrey, UK.
ESD - Membrane switches and LCD Displays
Hi Jim. You wrote: ---snip--- In my experience, if you use a 'normal' proprietary membrane switch/panel, with the half inch dead zone at the edges that you describe, you wont have an ESD problem, at least not by breakdown of the membrane at 8kV. However, ESD discharges at the periphery of your membrane panel, if mounted on a conductive (metal) panel, will cause highly intrusive spikes to be generated within the membrane conductors. It would be wise to decouple the ultimate destinations of these conductors with a small capacitor to avoid spurious operation of the related electronics, particularly if you have high speed latches etc. being driven by the membrane switches. LCD panels are temporarily visually affected by the 8kV potential present on an ESD probe while it looks for a discharge path, happily the front glass of the LCD panel is easily capable of holding off 8kV, and I've never had an LCD driver fail due to induced energy from adjacent discharges. (YET!) Another tuppence worth... Regards, Chris Dupres Surrey UK.
Copy of: Bonding of structures
-- Forwarded Message -- From: Chris Dupres, 100014,3703 TO: Rick Busche, INTERNET:rbus...@es.com DATE: 6/3/97 7:03 AM RE: Copy of: Bonding of structures Hi Rick. You wrote about earthing screws etc.: < The intent of the toothed washer is to bight through the paint to ensure conductivity.> A few years back, on a Machine Control Panel door, we used such an earthing screw method (Screw, crimped terminal ring, toothed washer, painted panel, spring washer, nut). For whatever reason, the main incomer cable had one phase wire come out of the main isolator and it sprung back and touched the panel door inside. We know this because the location of the Earth bolt was now a very badly burnt hole, and no sign of the toothed washer. The opinion at the time was that the washer itself took the whole of the fault current, and being high carbon steel, was high resistance, and got so hot that it caught fire! (hold a guitar string in a gas flame and see what happens!) Also.. The initial heating of the washer annealed the 'spring' of the washer, which collapsed, therefore reducing contact pressure and giving rise to an arc which simply burnt back like an arc welder with a high carbon steel rod. Initial heating is excacerbated because the point contacts of the teeth have very poor thermal conductivity to the steel case, and therefore any overheating due to I2R wont be dissipated into the case metal. I've come to the conclusion that star/toothed washers for protective earthing purposes are intrinsically poor, and bound to fail when you need them most. A spot faced surface and a ring terminal with NO intermediate washers, but a flat spring or wavy washer on top of the crimped terminal ring is almost infallible, and a welded stud is far superior to a bolt/nut, as the fault current can also find it's way through the wavy washer/nut to the stud. Subsequent tests with a car battery (Hardly precision, but informative) showed that star washers failed at about 25A, and flat spot faced contacts didn't fail, but the cable caught fire! Re. the zinc paint. I don't think thats a very good idea... zinc paint is paint, with zinc in. Zinc paint, while being conductive, is fundementally metal in a resin matrix. Not the sort of material that makes a good fault path. Just put a sticky round label over the screw hole or run a screw into the hole prior to painting. Star washers seem to be fine for EMC/noise/RF grounding purposes. Just a humble opinion from a chap who has to take the blame for brand new machines catching fire and people getting electric shocks from machines. Chris Dupres Surrey, UK.
Re: frequency scanner for EMC
Hi Moshe/Gabriel. Re: low cost scanners. I've been using a Tandy handheld scanner with the supplied 8" whip antenna for going round 'look-seeing' equipment for years. The antenna has sufficiently low gain at frequencies below 100 MHz to make it useful as a localized sniffer. The scanner is a Realistic PRO-something-or-other, about 6 years old, and has an unsophisticated AGC, so is more useful than a modern hyper-performer. i.e. I can get subjective differences in amplitudes without the AGC making everything the same volume. Set the scanner off about 1 metre (near field) from the equipment, from 30MHz, with the squelch set to just suppress background at 27MHz (ISM stuff)and 100MHz (broadcast in the UK), and scan to 1GHz noting where it stops on non-music. After the first scan, go back and home in on the frequencies found, using the scanner as a sniffer. It's success at finding emissions is amazing, but alas often sends you off chasing ghosts which are really significantly lower than compliance levels. It's difficult ot calibrate an audible 'squawk'. Final compliance is done with a full antenna/spectrum analyser kit of course, the scanner is used to identify hot spots. Thats a tuppence worth. Chris Dupres Surrey, UK.
IEC - 1326 -1 EMC for lab equipment?
Hi Moshe. You wrote: I found this about a month ago, and ordered it then. So far, nothing has turned up (from British Standards) They may yet come back and say it's not published, or something, but so far nothing. BS don't give out tech info, only prices, for their standards so I haven't got any more information at this time though I confess I haven't exactly camped on their doorstep. If anything turns up I'll post you. Have a nice day. Chris Dupres Surrey, UK.
Large piece of metal pacts
Hi Raymond. You wrote: You don't say what 'it' is, but you allude to the fact that most large bits of metal form part of the case of equipment, or may have mounted on it power switching devices. If it isn't grounded, it can radiate, or not screen, but there is no 'Law' or 'Standard' which states that large metal parts must be grounded, it's just that unless you do you may have a problem. Floating metalwork can often act as no screen at all, but you knew that... If you need an explanation of that effect then do please come back and I'll try and oblige. More importantly, for LVD or safety reasons, large metal parts should be grounded. Chris Dupres Surrey, UK.
Copy of: Fire Enclosures
-- Forwarded Message -- From: Chris Dupres, 100014,3703 TO: "Kendall Wilcox", INTERNET:kwil...@fcpa.fujitsu.com DATE: 4/27/97 6:13 AM RE: Copy of: Fire Enclosures Hi Kendall. You wrote: < No matter what the size of the openings on the top of the unit, if you can pass the abnormal tests above without flame spreading from the unit, can a regulatory agency deny approving the construction ? (assuming of course the enclosure meets all other requirements for enclosing electrical/mechanical hazards etc.) I don't think so. Rich Nute mentions that he has received different interpretations from various regulatory agencies regarding top enclosure openings. Rich, do you think there would be differing interpretations if the abnormal test passes ?> I've always worried about the nature of the 'fire' in relation to these tests. Some fires are simply fuseholders etc. getting very hot, i.e. forming a local hot spot, maybe an arc or something, and the local flammable material forming a fairly low energy fire that is primarily the effects of this local hot spot. These fires are characterised by flames which lick around a bit and are easily contained by a simple enclosure, and heat is spread by convection (goes upwards). These fires often go out when the power is removed. Some fires however are extremely aggresive, and may be caused by something like a short circuit transformer which produces very large amounts of flammable gas which 'jets' all over the place like gas burners. Or highly flammable material may burn, such as Perspex, Polystyrene etc., producing highly exothermic reactions which fuel themselves. In these cases heat doesn't just go upwards, but comes out of any hole it can find. These fires don't go out when the power is removed. It seems that the 'rules' don't differentiate between these types of fire, I think this puts the onus back on the designer to anticipate the nature of a fire and show that it has been taken into account when the enclosure was specified. Another thing I worry about is the nature of the gas given off. Some of these plastics are much more dangerous in the gas they give off while burning, than any risk of fire. This is covered in general terms in IEC 1010, but materials are not specifically listed, but that's outside the scope of this thread. Chris Dupres Surrey, UK.
input current rating versus input circuit protection
Hi Bob. You wrote: I don't recall seeing any protection choosing rules in any standards, though I stand to be corrected. Circuit breakers, like fuses, should have their characteristics chosen according to the circuit they are protecting. I.e.: If your protected circuit is a resistive heating load you would have no 'inrush' current, and therefore your circuit breaker would be chosen with an 'instant to constant' ratio of say 2:1, where a 10A circuit breaker would allow 20A for , say, 60mS. If your circuit is a motor or a small transformer input power supply, then your ratio would need to be something like 6:1 If your circuit is a large transformer or a tungsten lamp load, you may need 10:1 or even 20:1. The circuit breaker (CB) constant (continuous) rating should be chosen to protect the wiring downstream of it, and the wiring upstream of it should be sized to cope with the CB continuous rating regardless of the actual current used. There isn't much future is trying to protect downstream components with a circuit breaker, with the notable exception of transformers, as they are often caused to trip by the failure of the component being protected. The CB tripping being an indication that the component has failed! And the range of CB trip values available gives limited scope for finding one which will be exactly 125% of your actual demand current. A rule of thumb I use is to measure the actual current, double it, and choose the nearest CB/fuse value upwards, choose the 'Instant' ratio according to anticipated inrush, and make sure that the wires are big enough. You have to be happy that short circuits anywhere will pull enough current to trip the CB, but not allow the CB to trip on the switch on event. If you do this the equipment will be both functional and safe. That's another twopence worth. Chris Dupres Surrey, UK.
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.
CE Procedures - Manufacturer traceabilit
Hi Jim. You wrote: I've been here. In order to maintain the source of the original equipment confidential, the equipment was bought in with the OEM's certificate and CE mark, but built with our name on the front and on the label. I simply wrote out a new D of C for the equipment, but in the file put a covering document that gives the OEM certificate as justification for us writing a new certificate in our name. The end user sees our name on the CE certificate. The Enforcement Authorities can see the files and the original OEM certificate, and the covering document ties it all together for ISO 9000. It worked for us. Chris Dupres Surrey, UK.
Fuses & Switches
Hi Randy. You wrote: <1) I have equipment which will be tested according to IEC 1010-1. This particular piece of equipment requires a mains 10 amp fuse at 230V line. I looked at some fuse manufacturers and they have fuses rated for what I need, but aren't necessarily IEC approved or are not approved for certain countries (like Denmark only accepts up to 8 amps when using IEC 127 fuses). Are there any fuses which are approved for all countries which can handle the current requirements? I would prefer using the standard 5 mm X 20 mm size fuse. > 20mm fuses are often glass, especially if with 'T' characteristics. This often makes them only suitable for secondary protection, i.e. their interrupt current capacity is often very low, down to 50A or less even. 20mm fuses for use on direct mains connections should be the ceramic tube, sand filled types. In the UK I found some 20mm fuses used on 230V equipment that were only rated at 110V, these fuses were mounted in a filter and simply exploded with some violence when they did blow. With direct mains connections a fuse should really be capable of stopping a prospective short circuit of a few thousand Amps at the supply voltage. 20mm fuses are not ideal, being mainly useful for current limited circuits like transformer secondaries etc. Wherever there is room, I prefer to use 1.25" fuses, ceramic, on mains connections. These turkeys can break 10kA @ 400V. I feel happier with those. In a perfect world you'll use circuit breakers, but you probably don't have room, nobody ever does. Just a tuppence worth... Chris Dupres. Surrey, UK
Thoriated-tungsten wire
Hi Jack. You wrote: < Is there a Directive in the European Community related to radioactive materials and do individual countries have more stringent regulations? > You refer to the Euratom Directives, of which there are a few, and which are regularly 'updated'. Many have 'a plurality' (meaning a hundred or so) of pages of Isotopes etc. And seem very specific. Germany seems to have tighter local regs, having something called Betrieb Algerbnis or something like that which I understand relates to local 'Permission to Operate'. In the UK we have the Ionizing Radiation Regs, which I think cover everything down to 10keV (low level X-Rays) with maximum dose rates of 5uSv/h at 500mm etc. That may help a bit, I thought some vague knowledge may be better than none at all. Good luck, Chris Dupres Surrey, UK.
Demos and Eval Units Now Require CE Mark???
Hi Andy. You wrote: --reply--- I don't have a copy of the EC EMC directive infront of me, but I'm fairly certain that an Article in that tome gives equipment destined for exhibitions a free run, and that may describe your Demo equipment. France is a proud and individualistic nation with a long history of unique scientific achievements and the world owes them much gratitude for such things as the Metric System and a singularly large statue situated at the entrance to New York's waterways. This individuality shows at the extremes of the national behavioural map as a particularly introspective view of the world which may seem to the Cosmopolitanly Challenged amongst us as slightly 'difficult' or 'protectionist', but I am sure that this is a distorted view. Europe has spent many years and expended much effort in finally getting all the European States to agree a common date for the time change used for Daylight Saving. Just as that was agreed, the French (for very good reasons which are extensively discussed in the French technical press) have had to pull out of the arrangement so painfully arrived at after so many years, and make entirely different plans. I'm sure they had no other choice, being uniquely placed so near the edge of the European land mass. Many years ago, I recall it was reported that in order to import Video Recorders into France, all had to be subject to the paperwork being arranged in one particular small office in the middle of France, rather than at the port of entry. This was a magnanimous gesture to speed things up, as the office in question was very small, and underworked, and so could concentrate on the task rather than making the applicants wait in a queue at a noisy and smelly port. It also provided this office with valuable work and alleviated the task placed hitherto on the port workers. This arrangement was to everybody's advantage, though the more cynical amongst the bitter baling hounds of the uninformed press suggested that this was a slowing tactic to give local products an advantage. Pish, let their pens turn to Grissini. Have a good day, Chris Dupres. Surrey, UK
Compliance to the rules
Hi Paul. You wrote: Isn't that in fact the basic and general purpose of the EMC rules: > - Protection against pollution and > - Assurance of reliable operation in that polluted world?> Let's step back a bit a take a wider view If I was a cynical person, and of course I'm not at all, I would suggest that the EMC rules are there because the Treaty of Rome (remember that) in 1970 or thereabouts started this EEC thing, and that the EMC rules are there to support the aims of that treaty in breaking down the barriers to free trade within the European Economic Area. (Not European Noise-Free Area) Yes, the rules do mention EMC, but I don't think that the Directive states anywhere that the intention is to make the world an Em quieter place, but it does say in lots of places that barriers to trade must dissappear. (in between Euro States) The LVD is the same, that was the first in 1973, and that doesn't say things must get safer, but it does scatter about the Directive the requirement to 'remove barriers to trade', and 'free movement of goods'. In four places I think. Well, it's a point of view, if through a jaundiced eye Take care, and DON'T PANIC. Chris Dupres Surrey, UK.
HV connector safety.
Good Folk. A question re. interpretation of the Creepage and Clearance tables in IEC 1010-1. BS EN 61010-1 etc. The Facts: 1.I have a cable terminated with a female connector that carries 15kV to a fixed device (an electron gun on a vacuum system in this case). This is rather similar to a screened aircraft Spark Plug lead. 2. The cable is screened, and the connector is all metal (grounded) with a ptfe piece inside which supports the female contact, and provides an insulating sleeve up the inside of he connector body to provide the necessary clearance and creepage path lengths for reliable operation. 3. The ptfe inner does not extend all the way along the inside of the connector case, leaving a few mm of uninsulated (grounded) metal. 4. It is possible to put the IEC1010 Annexe B Test Finger into the connector and to touch the live receptacle, but it is impossible to do this without grounding the Test Finger on the Connector case. The Question... Am I right in assuming that using the Test Finger to locate (IEC 1010 6.2.) and measure (IEC1010 6.3.) the voltage on the accessible part, then using the circuit in IEC 1010 Figure A.2. I will show that the actual volts measured will be zero, so under those conditions claim that the connector can be described as 'safe'? In reality, if someone was to put their finger into the connector and touch the HV contact, they would provide a current path to earth (the body of the connector) through their finger, and one that would effectively bypass conduction through their body to earth. The source impedance of the 15kV is approx 150Kohms. So, does providing an unavoidable earthed 'guard ring' at the access to the high voltage terminal provide protection such that the Creepage and Clearances required in IEC 1010-1 can be disregarded? What do you think folks, Reasonable? Sensible? Safe? or What? Your opinions are, as always, most valuable. Thanks Chris Dupres Consulting Engineer Surrey UK
LVD, and portable equipment.
Dear Gentlefolk of the emc-pstc. A trivial question, but one that I'd appreciate the views of the group. 1. The equipment consists of a 24V psu, with a hand tool plugged into the power supply, rather like a soldering iron. 2. The hand tool is 'unpluggable' from the psu, i.e. it is not permanently connected. 3. The hand tool consists of a heated probe, which can reach 300 deg Celsius. 4. 'Probes' are entirely passive, i.e. there are no voltages present except those driving the 24V heater. My questions are: a) Does the power supply AND the hand tool have to meet the requirements of the EC Low Voltage Directive? - i.e. does the hand tool have to meet criteria of power supply marking, temperature, mechanical protection, carrying handles etc. etc. as well as the power supply? OR b) Can I simply test the power supply on it's own, and ignore the plug-in hand tool as it is outside the scope of the LVD in terms of supply voltage? OR c) Must I test the two items plugged together as would be used in practice. d) I'm assuming that the relevant standards ie EN 61010-1, Controls and lab equipment..., but should this come under EN 60204-1, Electrical equipment of machine tools? Or is there another? The same question must be asked of soldering irons, modelling drills, low voltage tools not powered by batteries but from a variable or controlled dedicated mains powered controller, I suppose. Thankyou for listening :-) Chris Dupres Consulting Engineer Surrey U.K. tel 01342 843154 fax 01342 844219
Moving on....
Hi Folks. For those of you that know me, I'll be leaving this position today, and taking on more consultancy work. I'll unsubscribe on this email address and resubscribe on my other address. So DONT PANIC!!!I know how much you all worry. Take care. Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Moving on...
Hi folks. For those that know me, I'm moving out of this position to take on more consultancy work. Therefore I'll be unsubscribing, and re-subscribing on my 'other' Email pad. DON'T PANIC I know how much you all worry... Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Machinery Directive.
Hi Folk. Anyone know if the EU Machinery Directive is available on the Net? Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Re: Harmonic current measurement and input power
Hi Rich. You dropped a p.s. which caught my cynical eye... > > ps: My personal opinion is that the mains is to serve us, > the consumer. We don't have to correct for linear > non-unity power factor loads, why do we have to correct > for non-linear non-unity power factor loads? My understanding is that the Committee (s) which grew IEC1000.3.2 and 3.3. were comprised of, in the majority, representatives from the Power Generating Industry, and the poor old consumer didn't get a look in. Subsequently, the principle was set that any problems with the mains supply is the users, not the makers. Perhaps that is a gross over simplification, but that's how it seems to me. They never had these problems with steam, or coal, or water mills, or windmills..... maybe we should go back. Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Re: EMI Window for LCD needed.
Hi Brian. You wrote: > > I am in need of an EMI solution for an old mono EL Panel that radiates > right through the front of the panel. A fine mesh screen works great > but difficult to manufacture because it is so flimsy. To have a > custom frame made to hold the screen taught is to costly. > > Does anyone know of a manufacture that has fine mesh screen that is > laminated onto a thin mylar sheet (or something like that)? > > I have tried several conductive mylar materials (sputtered with some > kind of conductive material) but I can not seem to get enough > attenuation through it. Any recommendations or alternate solutions > will be most appreciated. Here's a few... RFI Shielding Ltd.fax +44(0) 1376 346442 Precision Optical Plastics Ltd. fax +44(0) 1993 700240 ROMAG glass productsfax +44(0) 191 414 0545 Warth International Ltd. fax +44(0) 1342 312969 Tecknit Europe Ltd. fax +44(0) 908 320324 All these guys do EMC screened transparent windows, either embedded mesh or conductive coatings. Most have US outlets. Hope it's useful. Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Re: ERGONOMICS/Color Red Restrictions
Don. You wrote: > Does anyone know if there are any formal restrictions to using red > colored lights for front panel displays and indicators? > > Is there a harmonized European standard or regulation or a specific > national regulation that requires the restriction of the color red for > warning, danger, etc. > > It seems it may have been a German ergonomic requirement before various > standards were harmonized. Can anyone shed some light on this issue? IEC204, EN 60204, BSEN 60204 (all essentially the same) reserves red as the colour for Fault or Abnormal conditions on Electrical Equipment of machines. i.e. should not be used to indicate the ON condition only etc. On a related subject, anyone in the PSTC got an opinion on what colour an illuminated mains rocker switch (those with an illuminated rocker) should be on non-machinery equipment. e.g. my washing machine is red, my computer is green, my fan heater is red, my kettle is red, my central heating controller is green, a bench power supply is red, a soldering iron green, an oscilloscope green Is there a 'standard' or reccomendation somewhere? Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Re: EMC Seminars
Hi Bill. You wrote: > Does any know of any good EMC Seminars? Not just a seminar but one where I > could actually learn something. Any help would be greatly appreciated. Probably not a great deal of use to you, geography being what it is, but ERA Technology are running a one day Introduction To EMC course, on Thursday 13th Feb 97, at Leatherhead, UK. This is aimed at Technical and Administration tasks, and looks like a good wide footprint introduction to those just pulling their heads out of the sand. Email: conferen...@era.co.uk home page: http://www.era.co.uk/techserv/conf/confpage.htm Well, you did ask... p.s. I don't work for these guys, just use them a lot. Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Re: Where can I find 92/59/EEC...
Hi Jon, You wrote: > Where do you get the EEC directives? > > I see some directives on web pages so I assume the directives are > 'free.' > > I'm looking for > 92/59/EEC - General Product Safety Directive, > 85/374/EEC - Product Liability Directive. Your local standards organisation should be able to sell you reprints from the OJ. > Where do you get the Official Journal of the European Communities? The OJ is published daily!, and is quite big, and covers everything from knitting needles, to tax laws, to BSE, to use of corporate cars, to. it is a complete record of that day's business of the EU. Organisations such as the ERA in the UK filter out the non techy dross, and can provide excerpts. ERA phone is +44(0) 1372 367000 fax is+44(0) 1372 377927 Email i...@era.co.uk That may help a bit. Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Re: DC Power entry
Hi Bob. You wrote: > Does anyone know any reason why the IEC 320 C-14 connector style cannot > be used for DC power? Specifically, we have an application for primary > power entry in the 48-70 Vdc range, typical of telecom applications, and > I see no clear reason for redesign to implement a different connector. > > It is commonly used for 100-250 Vac and 50-60 Hz. However, does common > usage exclude it from other similar applications? Are ther code > restrictions somewhere which would interfere with it? > > The connectors are typically marked with an ac rating, but I would > expect approval in the application would be achievable, at least for the > electrical characteristics. I suppose someone would gripe about its > conventionality. > I've always come up against IEC 1010 clause 6.10.3.(b) which seems to cover ambiguous connectors. > Regarding alternatives, is there a "typical" appliance connector used in > the telecom industry for this DC power distribution? > The only common thread that I've noticed is the use of Molex type mulipole connectors (e.g. FCI Qikmate) for d.c. supplies, often used on both the supply itself and the associated equipment. Thats a couple of Euro's worth... Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Re: Re[2]: Shiep rules
> Date: 05 Jan 97 20:35:39 EST Hi Cortland. You wrote: > Don't you agree it is fair to have one set of laws for everyone? > > Don't you agree we should be able to listen to radio even if the neigbhor > turns > on his computer? > Here my natural cynicism comes out... Don't lose sight of the fact that the Euro Directives, such as the EMC, LVD etc. were born out of the Treaty of Rome in 1968 (wasn't it?) and are colloquially known as the Single Market Rules. Their main purpose is to provide a common technical standard so as to allow the free passage of goods across European borders, or at least preventez certain states from stopping goods at le border because they don't meet some rule or autre. The reduction in Electronic Fog in our universe is a secondary effect of these rules, an admirable one, but nevertheless an effect rather than a cause. I think that the enforcement authorities would get far more excited if goods with CE marks were stopped at a border, than if the goods made too much EMI. There's a few centimes/Deutchmarks worth... Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Re: German Army EMC Stds..
Hi Chaz. You wrote: > We have a bid on sales to the German Army. However, they (the German Army) > want to know if we meet low emissions to avoid data pick up. > > Does any one have any info on this? I think you are looking at TEMPEST type equipment. This is stuff that is not so much 'low' on emissions, as 'zero' emissions. E.g. Computer monitors with total magnetic screening such that line timebase and video amplifier operation cannot be picked up and displayed on a screen nearby. This stuff is seriously expensive and very specialised... Stealth technology is very different to EMC. A lot of this technology hides behind 'SECRET' folders unfortunately, but I wish you luck anyway. Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Re: regarding fusing ac-mains
Hi Mike. You wrote: > Where do you put the AC mains fuse relative to the "X" capacitor used for the > EMI filter? > > How does the "accross the line" safety rating of the capacitor affect this > answer? > > Specifically. Would you put an X cap in the unfused area of the AC inlet > like the EMC fellow wants? What about a "Y" cap? X caps and Y caps are designed to be very high reliability components, self healing etc. and in the case of X1 caps, good for 4kV peaks. Filters that use these things generally need to be mounted right at the point where the mains supply enters the equipment, this invariably means before the fuse. The caps are designed to be as reliable as the wire that feeds them, and so can safely be put before the fuse without affecting the safety integrity of the equipment. I use these caps in filters that are permanently live from day one, before the fuse, but in the happy knowlege that there is a fuse up line somewhere rated to protect my mains supply cable. That's me anyway. Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Re: Toroid Isolation Power Transformers -Reply
Hi Jim, You wrote: > The isolation aspect is limited to 60Hz > isolation. The prime power is > ungrounded. It will be fed through the > isolation transformer whose secondary > will be grounded to form a green wire > ground/neutral connection. For this I > don't think I need interwinding screens. You still have the problem if there is a primary feed/secondary short, where full mains voltage can appear on the secondary. Low voltage secondaries my be sufficiently low impedance to take out your fuse, but high voltage secondaries(>120V) may simply get very hot while the external circuit suffers overvoltage. The Earthed interwinding screen effectively removes that possibility by providing a short circuit path to blow the supply fuse. > > However, I don't quite understand your > comment supporting switch on voltage > peaks. This seems to me to be counter > productive - or am I under a > misconception. I thought I would need a > switch on zero to minimize inrush > current. This is merely acknowledging that inductive circuits have 90 degrees lag on current. If your transformer is unloaded on switch on, the current will be at a minimum when the voltage is at a peak. These peak switching SSR's are produced just for that purpose, and are, in my experience, a God send. Conventional resistive or loaded transformer switching can use Zero Cross Over switching, as the I and V are in phase. Sorry about the confusion, Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Re: Toroid Isolation Power Transformers
Hi Jim. You wrote: > Looking for info on using toroid transformers for power isolation in > applications up to 10 kVA. Their advantages are great - half the > size, half the weight, and less costly. I understand they have higher > inrush current, but I don't know how much. Looking for advice. I'm not sure about their use as IsolationTransformers, I always use E cores with separate bobbins for that. The Toroids MUST have earthed interwinding screens if used for isolation. Inrush currents can be very high, it's best to switch them with a Peak Voltage switching solid state device (Not zero voltage) if you can, or use circuit breakers with an 10:1 instant / long term trip ratio. They are much better at tranferring EMI from the secondary to the primary as well, they can't be used as an adjunct to filters as E cores can. Thats a tuppence worth.. Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
Re: EMC - Upgrades
Hi Phil. You wrote: > Can anyone help with the following EMC question? > > It concerns equipment shipped to a customer prior to 1996 [ not EMC > tested and not expected to comply ]. > > We want to upgrade the equipment on the some customers' sites to add new > functions.This will involve adding some new PCBs & a new wiring loom . > The equipment is still not expected to comply with EMC regs.Is this > acceptable? > > If, instead of doing the work on the customers site, we brought it back > to our factory and did the same work here. Would this be acceptable? > > If, to save the customer down time, we modified a similar piece of > equipment in our factory and then swapped it for the customer's > instrument. Would this be acceptable? Does it depend where the equipment > we modify comes from ?(i.e. It could be unsold factory stock or could > have been returned from a (different) customer). Assuming that the customer is in the EEA, the situation seems to be this: a) If you 'repair' the equipment to bring it to the same performance/standard as before the repair, no compliance is required. b) If you 'upgrade' the equipment, or 'refurbish' the equipment to a higher performance/standard, then the extra bits need to be compliant. Whether the work is done at the customers site, or at your site, or on the moon is not relevant, what matters is where the equipment will be put into service. The significant point being that if it's put into service in the EEA after the 1st Jan 96, the added bits must comply. If the modifications are substantial, then the whole equipment should be compliant as the term 'modified' becomes a bit nebulus. Second hand equipment that has already been in use in the EEA before the 1st Jan 96 need not be CE marked, if it has not been modified. New stock items from your stores that have not been 'placed in the supply chain' must be CE marked when delivered. That a tuppence worth. Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
RE: How long for continuous? -Reply
Hi All. Gordon wrote: > How long is this "continuous" going to go. Its a waste of everyones time! > Looks like some of us were a bit miffed by Gordons words, but isn't he making a jolly funny joke?. You know, continuous 'continuous'. Maybe I'm simple. Ha Ha Ha, nice one Gordon, next time put a Smileycon :-) Chris Dupres EMC Specialist. VG Microtech. cdup...@vgmicrotech.com tel +44 (0) 1825 761077 fax +44 (0) 1825 768343 'Opinions expressed are personal, not necessarily Corporate'
