I was thinking only that people who have had my course not reply because they should already know. Will post the answer discussion later tomorrow. I have really enjoyed the replies and learned from them. And you are right. Ground lead parasitic inductance plays a major part.
Doug Smith Sent from my iPhone IPhone: 408-858-4528 Office: 702-570-6108 Email: [email protected] Website: http://dsmith.org On Sun, Jan 28, 2018 at 18:42, Ken Javor <[email protected]> wrote: Re: [PSES] Measurement dilema As long as we’re all chiming in here that was my guess as well (probe ground lead parasitics) but I thought the ground rule :-) was no group replies... Ken Javor Phone: (256) 650-5261 From: Dale Reid <[email protected]> Reply-To: Dale Reid <[email protected]> Date: Sun, 28 Jan 2018 20:38:56 -0500 To: <[email protected]> Subject: Re: [PSES] Measurement dilema How about the different size loops the ground leads on your probes are making. Dale Reid Product Safety Engineer O +1 859 825 4733 [email protected] <http://www.lexmark.com/> [http://www.lexmark.com/] www.lexmark.com <http://www.lexmark.com> [http://www.lexmark.com] On Sun, Jan 28, 2018 at 7:54 AM, Bart De Geeter <[email protected]> wrote: Hi Doug, Could it be that there is just a piece of transmission line inside the box terminated with a certain impedance? You might be measuring in the middle of this transmission line. If the input impedance selected on channel A of your oscilloscope is f.e 50 ohm and the other input channel has 1Mohm input impedance selected, you will measure a different voltage at this particular point (as the measured signal is the sum of the direct wave+ reflected wave on this transmission). So far, my guess 😉 Greetings, Bart Van: Doug Smith [ mailto:[email protected]] [[email protected]]] Verzonden: vrijdag 26 januari 2018 23:50 Aan: [email protected] Onderwerp: [PSES] Measurement dilema Hi All, Can you explain the result in this video I just made? Scope plots of the same two nodes are completely different. Probes and scope are operating normally, no problem with the equipment itself. If you have been to my seminars you know the answer, please do not post the answer unless you have not seen this experiment until now. Hint 1: There are no EM fields radiating from the shielded box affecting the probes. Hint 2: There are no active components inside the box. https://youtu.be/qj-HBFMEJiY Doug - ---------------------------------------------------------------- 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 <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html [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/ [http://product-compliance.oc.ieee.org/] can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ [http://www.ieee-pses.org/] Instructions: http://www.ieee-pses.org/list.html [http://www.ieee-pses.org/list.html] (including how to unsubscribe) <http://www.ieee-pses.org/list.html> [http://www.ieee-pses.org/list.html] List rules: http://www.ieee-pses.org/listrules.html [http://www.ieee-pses.org/listrules.html] For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- 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 <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html [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/ [http://product-compliance.oc.ieee.org/] can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ [http://www.ieee-pses.org/] Instructions: http://www.ieee-pses.org/list.html [http://www.ieee-pses.org/list.html] (including how to unsubscribe) <http://www.ieee-pses.org/list.html> [http://www.ieee-pses.org/list.html] List rules: http://www.ieee-pses.org/listrules.html [http://www.ieee-pses.org/listrules.html] For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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To post a message to the list, send your e-mail to < [email protected] [[email protected]] > All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html [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/ [http://product-compliance.oc.ieee.org/] can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ [http://www.ieee-pses.org/] Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) [http://www.ieee-pses.org/list.html] List rules: http://www.ieee-pses.org/listrules.html [http://www.ieee-pses.org/listrules.html] For help, send mail to the list administrators: Scott Douglas < [email protected] [[email protected]] > Mike Cantwell < [email protected] [[email protected]] > For policy questions, send mail to: Jim Bacher < [email protected] [[email protected]] > David Heald < [email protected] [[email protected]] > - ---------------------------------------------------------------- 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
