Doug, you’re such a tease! :-) _______________________
I'm here to help you succeed! Feel free to call or email with any questions related to EMC or EMI troubleshooting - at no obligation. I'm always happy to help! Kenneth Wyatt Wyatt Technical Services LLC 56 Aspen Dr. Woodland Park, CO 80863 Phone: (719) 310-5418 Email Me! <mailto:k...@emc-seminars.com> | Web Site <http://www.emc-seminars.com/> | Blog <http://design-4-emc.com/> The EMC Blog (EDN) <http://www.edn.com/blog/The-EMC-Blog> Subscribe to Newsletter <http://www.emc-seminars.com/Newsletter/Newsletter.html> Connect with me on LinkedIn <http://www.linkedin.com/in/kennethwyatt> > On Jul 12, 2016, at 10:33 AM, Douglas Smith <d...@emcesd.com> wrote: > > Here is a bit of suspence for Friday, free webinar on this topic (joining > details available shortly).....the addition of a simple change to the probe > significantly improves, almost eliminates, frequency response problems due to > the ground lead and circuit impedance. Can you guess what it is? Got a patent > on this 30+ ago while at Bell Labs, expired now > so in public domain. It applies to both active and 10x Hi-z passive probes > and is incorporated now in most high speed active probes. It can recover an > octave of well behaved frequency response at essentially no cost. > > No spoilers from alumni of my seminars please! Will give the answer next week > for those that cannot make the free webinar. Just wanted to get people > thinking. > > Doug Smith > Sent from my iPhone > IPhone: 408-858-4528 > Office: 702-570-6108 > Email: d...@dsmith.org > Website: http://dsmith.org > > On Tue, Jul 12, 2016 at 04:17, B Rowland <bfr...@direct.ca> wrote: > Hello PSES crew; > > > T Sato wrote: > > > "Performance of passive probes strongly depends to the oscilloscope, > > so I think it should always be calibrated with a specific oscilloscope > > channel." > > Indeed, not only "should", but MUST, as John Woodgate stressed. > > But, as I mentioned, the calibration is often meaningless, if it does not > account for non-monotonic frequency response, , the Gaussian that is > expected, which results in unexpected transient response. > > Additionally, the calibration becomes "broken" as soon as the probe/scope > combination is used in any "real world" application where the impedance of > the DUT circuit is unknown, or not the same as the calibration circuit, since > the probe reactive loading varies with instantaneous frequency ("typical" 500 > MHz passive probe reaches 50 Ω loading at about 320 MHz), and the combination > of probe capacitance, circuit capacitance and ground lead/ground clip/ground > connection loop size, all cause resonances at rather common frequencies/edge > rates. > > Probably the best 'calibration' is to attach the passive probe to a circuit > to be tested, and attach a low-capacitance active probe to the same point, to > see the "real" signal at the passive probe's tip… this could be quite a > surprise ;-) > > In short, "Your mileage may vary" is good advice when it comes to probing > > If Doug Smith does offer a webinar, please do consider attending, if you are > at all unsure of this whole "can of worms" that probing is! > > Best regards, > Barry Rowland > Formerly " Senior Application Specialist, Oscilloscopes", Rohde & Schwarz > (and FAE at Tektronix and Agilent) > > > > > > > On 12/07/2016, at 12:42 PM, "T.Sato" <vef00...@nifty.com> wrote: > > > On Tue, 12 Jul 2016 02:08:04 +0100, > > John Woodgate <jmw1...@btinternet.com> wrote: > > > >> Slight under-compensation would cause a brief overshoot to 138 V. In my > >> opinion, probes can't be calibrated except with the scope they are > >> exclusively used with. Covering the cal adjuster with a sticker shows a > >> deep > >> misunderstanding of how passive probes work. > > > > Agreed. > > Performance of passive probes strongly depends to the oscilloscope, > > so I think it should always be calibrated with a specific oscilloscope > > channel. > > > > EURAMET cg-7 (calibration of oscilloscopes), > > https://www.euramet.org/get/?tx_stag_base%5Bfile%5D=3611&tx_stag_base%5Bidentifier%5D=%252Fdocs%252FPublications%252Fcalguides%252FEURAMET_cg-7__v_1.0_Calibration_of_Oscilloscopes.pdf&tx_stag_base%5Baction%5D=downloadRaw&tx_stag_base%5Bcontroller%5D=Base > > also says "For multi-channel systems, the measurement result must be > > related with the corresponding oscilloscope channel. A probe > > calibration is only valid in combination with the calibrated > > oscilloscope (indicated in the calibration certificate). The probe > > calibration must be clearly related to the applied channel." > > > > Regards, > > Tom > > > > > >> From: Schaefer, David [mailto:dschae...@tuvam.com] > >> Sent: Monday, July 11, 2016 10:50 PM > >> To: EMC-PSTC@LISTSERV.IEEE.ORG > >> Subject: [PSES] Oscilloscope probe calibration > >> > >> All, > >> > >> We're seeing an issue with scope probes, and I'd appreciate suggestions, or > >> just information on how others handle calibration. I've got two problems > >> with passive scope probes. > >> > >> First, probe compensation. Compensation depends on the capacitance of the > >> scope being used, so the probe would be adjusted to match that capacitance. > >> Well if the cal house is using a different scope, they'll adjust it to > >> match > >> their capacitance, which may not be what we need. Also, many times the cal > >> sticker then covers the adjustment port, implying the user should not be > >> adjusting that value. I disregard the stickers, but it isn't a good habit > >> to > >> get into. > >> > >> Second, we're seeing variance between in cal probes based on what they're > >> measuring. I had four probes measuring a 1 microsecond rise time transient > >> signal. All were within 5% of the expected peak voltage. Next, all four > >> probes measured a 5 ns rise time transient. Three peak voltages were within > >> 10-15% of the measured 100V(not great, but acceptable). The fourth > >> consistently read around 138 V. Nearly 40% off, just by changing the rise > >> time. 5 ns might be at the edge of the probe's bandwidth, but I'd expect a > >> decrease in level, not an increase. > >> > >> These were all calibrated probes, and three were identical models. The one > >> that was way off wasn't the odd model. Our cal house measures a DC voltage > >> for accuracy, and bandwidth. > >> > >> What's causing the inaccuracy? How can I prevent this problem in the > >> future? > >> Moving to all active probes isn't an option right now. > >> > >> Thanks, > >> > >> David Schaefer > >> > >> - > >> ---------------------------------------------------------------- > >> 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 <mailto: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) <http://www.ieee-pses.org/list.html> > >> List rules: http://www.ieee-pses.org/listrules.html > >> For help, send mail to the list administrators: > >> Scott Douglas <sdoug...@ieee.org <mailto:sdoug...@ieee.org> > > >> Mike Cantwell <mcantw...@ieee.org <mailto:mcantw...@ieee.org> > > >> For policy questions, send mail to: > >> Jim Bacher <j.bac...@ieee.org <mailto:j.bac...@ieee.org> > > >> David Heald <dhe...@gmail.com <mailto:dhe...@gmail.com> > > >> > >> - > >> ---------------------------------------------------------------- > >> 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> > > > > - > > ---------------------------------------------------------------- > > 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> > > - > ---------------------------------------------------------------- > 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> > > - > ---------------------------------------------------------------- > 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 <mailto:emc-p...@ieee.org>> > > 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 <sdoug...@ieee.org <mailto:sdoug...@ieee.org>> > Mike Cantwell <mcantw...@ieee.org <mailto:mcantw...@ieee.org>> > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org <mailto:j.bac...@ieee.org>> > David Heald <dhe...@gmail.com <mailto:dhe...@gmail.com>> > - ---------------------------------------------------------------- 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>
