All,
I received the following email from a customer today via their customer addressing our application of surge testing. We are testing laboratory equipment per IEC/EN 61326-1 and IEC/EN 61326-2-6 and specifically are having failures with respect to surge on a system that has multiple power cords. We are testing one power cord at a time. Here are their comments we have never tested a system comprised of multiple instruments in this way before. i.e. applying surge to one unit at a time - we have always, with agreement from our customers, applied surge (and in fact all tests) to all of the units plugged into e.g. a mains distribution block all at the same time. Especially for surge, it seems unlikely that in the real world any real surge on the mains supply would not affect all things in a system as it is very likely they are all plugged into the same mains circuit in e.g a particular room. To further bolster this, we have made comment to customers in the past that it could be noted in the manual to ensure this is the case. By applying surge to all units at the same time, we maintain all of their supply voltages at the same level. I can see how, by applying a surge to a single part of the wider system, communications issues could occur as suddenly the points of reference (i.e. reference voltages) for different parts of the system could be pulled away from each other by the surge. Testing a system by applying the tests to all at once, rather than a single item at a time, isn't necessarily an "easy way out" either. For other tests e.g. conducted emissions, where noise transmitted from the unit under test back onto the mains supply is measured, passing is made more difficult by measuring all units at once. Where in this case one at a time would be much more favourable. Our test house has always advised that we can choose, either all tests one at a time, or all tests applied to all through a mains block, but we cannot mix and match between different sections for the conducted EMC tests. I know this brings up all sorts of questions, however I would like to focus on the surge testing at the moment. I am pretty sure at least one of the standards says conducted emissions shall be tested on each port individually, but we don't need to go there right now ;-) Thoughts when you get responses like this? Larry K. Stillings Compliance Worldwide, Inc. Test Locally, Sell Globally and Launch Your Products Around the World! FCC - Wireless - Telecom - CE Marking - International Approvals - Product Safety 357 Main Street Sandown, NH 03873 (603) 887 3903 Fax 887-6445 www.complianceworldwide.com <http://www.complianceworldwide.com> Privileged/Confidential Information may be contained in this message. If you are not the addressee indicated in this message (or responsible for delivery of the message to such person), you may not copy or deliver this message to anyone. In such case, you should destroy this message and kindly notify the sender by reply email. Please advise immediately if you or your employer do not consent to Internet email for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of my firm shall be understood as neither given nor endorsed by it. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
