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:d...@emcesd.com]
Verzonden: vrijdag 26 januari 2018 23:50
Aan: EMC-PSTC@LISTSERV.IEEE.ORG
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
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