Doug, a very timely article. I recently worked with somee others on this same issue. A short (1/4") probe extension caused serious overshoot/ringing on a Tektronix active probe. The solution was a series damping resistor but as you say, you cannot restore the lost bandwidth. SPICE clearly showed what was going on.
Dave Cuthbert Micron Technology From: Doug Smith [mailto:[email protected]] Sent: Monday, October 06, 2003 5:42 PM To: emc-pstc Subject: Heisenberg and signal measurements This month's Technical Tidbit on my site (http://emcesd.com) has been posted (click on waveform graphic at the bottom of the home page). The abstract of the article is: Abstract: Heisenberg's Uncertainty Principle might be adapted in the context of signal measurements to say that one cannot measure a voltage at a node without affecting it. Simulation data is presented to show that under realistic conditions, active probes without damping resistors can significantly affect the signal to be measured. The result can be more serious than just signal loading. I have been increasing my lectures at Universities in recent years and will add another university here in the USA next spring. Although I lose income I could have made during the time spent, the effort does help the universities. My next continuing education lecture of this type is at Oxford University: my 2 day High Frequency Measurements and Noise in Electronic Circuits course in November. For details go to the Oxford site: http://www.conted.ox.ac.uk/cpd/electron cs/courses/high_frequency_measurements.asp Many airlines are running sales to the UK from the USA for as little as about US$200! It may be less expensive to fly from Denver to London than from Denver to Boston. And... Oxford is a great place to visit this time of year and attendance helps the University. Doug -- ___ _ Doug Smith \ / ) P.O. Box 1457 ========= Los Gatos, CA 95031-1457 _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 / /\ \ ] / /\ \ Mobile: 408-858-4528 | q-----( ) | o | Email: [email protected] \ _ / ] \ _ / Website: http://www.dsmith.org 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] Archive is being moved, we will announce when it is back on-line. 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.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] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
