Chris, My experience is that we don't tend to have problems running unscreened power to electronics on cars(and that includes running cables under a latest spec. F1 V10) ......but I can't know your "set-up". We do however have very high quality Pi fitering at PSU inputs to modules, are very careful in using multiple layer boards with good planes / partitioning etc etc. with metal or Carbon fibre housings....and we are very careful in how we run grounds....... Our application is F1/Indycar/WRC Race cars, with serious electronics, logging and control, ECU/semi-auto gearbox etc. so I believe we are an extreme real world case.
On test/validation I don't normally go above 50V/m but have done in the past without ill-effect. Also I only use free field above ~400MHz, below this I use bulk current injection as its a little closer to the real world in my opinion. What standard are you using? RI 100V/m sounds like Ford to me! I too would guess that leaving your screen in but unterminated is a bad idea - and presumably will resonate at some frequency related to its length ~ seen that one.....! regards Peter From: Chris Chileshe [mailto:[email protected]] Sent: 09 February 2004 14:44 To: EMC-PSTC Discussion Group Subject: Automotive application - Unterminated cable shield Group, I have an application which is causing me some grief because it is a departure from a setup I am used to. I hope you can help. The application is automotive. I have a cab mounted microprocessor based automotive product which runs off a dedicated PSU. The product case is all plastics and the PSU case is all metal. To picture the product, imagine if you will, an intelligent gear lever (stick shift) with buttons on the top for changing gears (this is only an analogy)! The cable between this product and its PSU is multi-way screened (shielded) and has a proprietary connector on one end for my product and a standard multi-way connector on the other end for a PSU. The cable is about 30cm long. On my product, the cable shield terminates on the PCB (separate plane) to which all my small RF filters are connected. This plane is not quite the same as battery -ve on the PCB. I have filters between battery -ve and this plane. At the PSU end, the general regime has been to terminate the cable shield onto the chassis of the PSU. A new application has arisen which does not require this PSU, and must use non-shielded cable. I have the option to cut off the PSU-end connector and supply my product with a flying lead. My concerns are as follows: 1 - Opting for non-shielded cable could reduce the effectiveness of my EMC measures 2 - Opting for shielded cable that is not terminated could upset my filter circuits on the PCB. I fear that leaving the cable shield unterminated at the PSU end might be worse than having no cable shield at all Unfortunately, I am at design stage so have no product to test. I need to make a quick call so as not to hold up the cable manufacturers. Is there some judgement one can make based on experience with shielded and unshielded cables (I have little)? I have the option to terminate the shield on a metallic bracket near the PSU, but for technical reasons, this bracket is not connected to chassis. Would this help, make no difference or actually make things worse? As usual, apologies that the description is probably not very clear, but I would gladly supply further info if anyone feels it may be a scenario they have encountered before. BTW, the RI test level is 100V/m. Thanx in advance. Rgds - Chris This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ 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://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ 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://www.ieeecommunities.org/emc-pstc
