Hi Amund, You only require the one piece of 20 meter cable and it has to be attached to your EUT. Only one thing can be the EUT at a time. I don't know if the EUT is your control and indicating equipment ( CIE ) or your other devices on the cable or if it is all of them. Assuming (worst case) that it is all of them, then you need to select each part in turn as the EUT add the 20 meter cable to it and isolate all the other devices from the surge. Trying to surge all 20 devices at the same time is not proper either. In the case you state, you have whatever protection scheme you have implemented in each device in parallel with 19 others and therefore improperly distribute the surge energy across all of them. BTW are your devices on the cable earthed? If they are not, be sure to check that the test house has a 10nF cap from the screen to earth at the EUT end of the cable as per Fig 3 in EN 50130-4 I may be reading things in to far, but I inferred from your wish to surge all devices on the cable at the same time that you have 20 different things that you want tested and not 20 identical devices. I can't imagine that you actually have 20 completely different fire detectors. If you have devices that have various options test only a fully loaded one and apply the results across the whole line. It's a whole lot cheaper testing that way :)
Best Regards, Kevin Harris Manager, Approvals and CAD Services Digital Security Controls 3301 Langstaff Road Concord, Ontario CANADA L4K 4L2 Tel: +1 905 760 3000 Ext. 2378 Fax +1 905 760 3020 Email: [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] Sent: Thursday, October 31, 2002 10:48 AM To: [email protected] Subject: Surge - injection point on screened cable [fadr] According to IEC/EN 61000-4-5, the surge pulse shall be injected onto a screened cable 20 meters from the DUT. We have a fire alarm system with 20 detectors connected on the same screened cable, 1.5 meters between each detector. We have been told from the local test lab that we have to add a 20m cable between each detector in order to surge test each detector. I'm sure our local cable distributor like that idea ... , but do we really have to do this ? Why is this 20 meters cable needed ? Is it to induce the surge pulse from the screen into the cable lines? The 20 detectors make a total cable distance of 30 meters and the screen is continuous. Is it possible to insert a pulse in the beginning of the cable and test all detectors simultaneous ? Regards Amund ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
