Re: Emissions testing with support equipment
Can I ask, please? How do you verify that these support PC's actually fail to meet class B emissions? Do you test them when you first remove them from their packaging, before adding your interface and peripheral? In my experience PC manufacturers qualify their PC's by creating the famous 'typical' system. What is a 'typical' system? Most interfaces also require their own certification, however, again they tend to be qualified using a 'typical' peripheral arrangement. One of the main problems is that a peripheral/interface may be qualified using 'typical' systems x, y, z but that does not mean that typical systems a, b c will pass. To some extent this brings us back to the subject of margin. If the PC manufacturer tests his PC in a number of 'typical' system arrangements and sticks to a decent margin, say ~6dB, and makes use of the 80-80 rule then it might be fair to say that his PC is reliably compliant. So, is your PC non compliant or have you found one of the non compliant arrangements? I believe that the governing bodies are well aware of this and tend to be more interested in knowing how much interference your part of the system introduces, both directly and indirectly. Peter - 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: Emissions testing with support equipment
Joe, Lots of us have the same problem. We always make it a point to isolate the PC from the test area. Since it is support equipment, we decided I cannot afford to fix other manufacturer's equipment along with ours, we don't have either the time nor the resources. Even though we might bring the computer into our building, configure and test it with our equipment for performance purposes, then ship the entire package to the customer, we do not concern ourselves with their EMC problems unless it affects our testing. One key point is that we require the customer to order the computer from the maker and not us. We are just a transition point in the shipping process. While we may configure the computer, we do not modify it in any way, simply set it up and make sure it runs correctly with our equipment using assemblies provided by the computer maker. I am sure there are some that will argue with our methods. It is debatable if this method meets the spirit and intent of the standards in force. But if there is only one computer that can handle our equipment and they are a world recognized maker and have all the compliances, what's a body to do? This is a great example of the problem of CE+CE=CE. It may not be reality but we choose to look at it this way. If we ever get questioned, we will simply say that if you can provide a computer that meets the performance specs and runs with our equipment, then you can buy whatever you want. But we have not tested it and will not guarantee its performance with our product. Regards, Scott s_doug...@ecrm.com - 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: Emissions testing with support equipment
-- Forwarded -- From: CollinJJ at USABDMFG List-Post: emc-pstc@listserv.ieee.org Date: 11/10/98 3:05PM To: MartinJP marti...@pebio.com at INTERNET Subject: Re: Emissions testing with support equipment --- Joe, This a very common problem throughout the EMC community. Your question of how different companies are handling this issue is a good one. However, I think the real question you should be asking is what does the law (standards) require. As I am sure you know, if you are selling this PC with your system, it must be tested and pass as a system. I am not aware of any standard,that allows the mfg. to isolate part of the OEM support equipment, from the test setup that is intended to ship with the host unit. The decision EMC professionals must make falls under risk management: 1. What are the risks of self certifying a system when the OEM (PC) does not meet the EMC requirements ? 2. Can I find an Approved Test Lab to write a report for this test setup? If so, what is the labs liability should there be a problem with the EU/FCC. 3. What liability am I putting on my company by labeling a complete system as being compliant, when I had prior knowledge of the OEM (PC) as being non-compliant? 4. Will the EU/FCC go after the PC manufacturer only or will my company share in the responsibility for the violation? Although I view the risk of being caught and prosecuted for the above scenario as being low, I would not want to be one of the few that get caught. It is my practice to select a PC mfg. that meets the requirements and then manage them very aggressively when there are compliance issues. Ultimately, if they can not deliver what they are advertising, I would select another vendor. I have had good luck with this issue by doing the following: 1. Conversing with fellow EMC professionals about compliant PC's they have used or have heard about. 2. Selecting and evaluating my PC well before I start my project. 3. Selecting several (3-4) PC vendors for my pre-qualification. 4. Not specifying and selling a particular PC with my unit. Regards, Jeff Collins EMC/Product Safety Engineer PE Applied Biosystems colli...@perkin-elmer.com __ Reply Separator _ Subject: Emissions testing with support equipment Author: MartinJP marti...@pebio.com at INTERNET List-Post: emc-pstc@listserv.ieee.org Date:11/10/98 4:05 PM EMC Professionals, Our equipment requires the use of a personal computer to operate. We sell these PC's with our system. We test radiated emissions as a system including the PC. We have recently tested PC's from two very well known PC manufacturers. They have both failed Class B limits. This makes it impossible for our system to pass Class B limits. When we isolate the PC from the test chamber, our instrument passes. I am sure that we are not the only company that has this problem. Can you please provide me with your experiences on this issue and what solution you came up with. All responses are appreciated. Regards Joe Martin EMC/Product Safety Engineer P.E. Biosystems marti...@pebio.com - 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). - 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).
Emissions testing with support equipment
EMC Professionals, Our equipment requires the use of a personal computer to operate. We sell these PC's with our system. We test radiated emissions as a system including the PC. We have recently tested PC's from two very well known PC manufacturers. They have both failed Class B limits. This makes it impossible for our system to pass Class B limits. When we isolate the PC from the test chamber, our instrument passes. I am sure that we are not the only company that has this problem. Can you please provide me with your experiences on this issue and what solution you came up with. All responses are appreciated. Regards Joe Martin EMC/Product Safety Engineer P.E. Biosystems marti...@pebio.com - 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: Emissions testing with support equipment
Ooooh, you're bringing up the snakes nest again. We just had this conversation on this forum not too long ago. First of all your experiences are unique, others have commented upon the problem, and yes it included some big names. One of the things that can happen to you is that you get a signal out of the PC that rattles around in you equipment. Your note suggests that this is not true, but do make certain. After that you really only have two choices. 1) Disqualify the vendor of PC your using and find another. (this could take a bit of a search), 2) Examine the PC and make sure that all of the mating edges, enclosure, I/O pcB's and connectors etc, are clean and making contact. One of the problems is that in shipping these things around they loosen up and lose their shielding capability. A very common cause of failure seems to be the monitor, and possibly the fact that the monitor is sitting on the case and deforming the computer enclosure. The debate still rages whether or not you can modify equipment made by others to allow you to pass. The FCC was strangely quiet on this issue when one of the members asked them about it. I would read that as a no. I have had to find a computer that was quite for some of my tests as well. Once you find it (and it won't be that difficult). Hang on to it. Not only do I allow others to use this computer, I try my darndest not to ship it anywhere. The test house I use is very good about allowing me a little space to store it in. Good luck. Gary -Original Message- From: MartinJP [SMTP:marti...@pebio.com] Sent: Tuesday, November 10, 1998 10:25 AM To: emc-p...@ieee.org Subject:Emissions testing with support equipment EMC Professionals, Our equipment requires the use of a personal computer to operate. We sell these PC's with our system. We test radiated emissions as a system including the PC. We have recently tested PC's from two very well known PC manufacturers. They have both failed Class B limits. This makes it impossible for our system to pass Class B limits. When we isolate the PC from the test chamber, our instrument passes. I am sure that we are not the only company that has this problem. Can you please provide me with your experiences on this issue and what solution you came up with. All responses are appreciated. Regards Joe Martin EMC/Product Safety Engineer P.E. Biosystems marti...@pebio.com - 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). - 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).
