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Show us your square wave
joeqsmith:
Recently someone was asking about how to use a scope and signal generator to measure the self resonance frequency of an inductor. I provided several examples, the later using a square wave to cause the inductor to ring at at the SRF.
https://www.eevblog.com/forum/beginners/measuring-the-self-resonant-frequency-of-an-inductor/
As long as I have the pulser out... shown is a Mini-circuits 6.3 - 15GHz high pass. Data sheet may be found at:
https://www.minicircuits.com/pdfs/VHF-6010+.pdf
I attached this to the old Tektronix pulser and then into my LeCroy 8500A. This scope has a BW of 5GHz. They claim a typical rise time of 90ps. Obviously the filter is outside the limit of what the scope can measure. Ignore that. The signal was stable and I used RIS to get a clearer picture what is going on. What I thought was interesting is it appears to have a dominant SRF of about 6.2GHz.
In the end, who smacks a filter like this anyway....
Grandchuck:
tggzzz and Joe are great motivators. Look and see what happens.
Now, why would Tektronix do that? One would think that their pictured result would exemplify best practices???
joeqsmith:
--- Quote from: Grandchuck on November 12, 2023, 03:48:08 pm ---Now, why would Tektronix do that? One would think that their pictured result would exemplify best practices???
--- End quote ---
Well ... Back in the 80's my mind set was a PC with a clock frequency of 50MHz, never going to happen. I will never need a scope with more than 100MHz BW. .... Our high end scope where I worked was a large 100MHz Tektronix DSO. I was using a Tektronix Polaroid camera to record data... I'm not surprised at all by the demo boards layout. Wouldn't surprise me to find out it was an intern's project.
The trigger and missing pulse test was a problem for some of our scopes at that time. :-DD
I keep a spook of wire on-hand to make these springs from scratch. 1) I start by tightly wrapping the probe's ground. 2) I remove the spring and give it a half turn. Round need nose pliers work fine. This gets enough tension on the spring to lock to the probe. 3) Ground strap is made from copper foil. Sometimes I use braid. All depends... 4) Solder the spring to the strap. 5) For insulation, I use Kapton. With braid, some heat shrink or woven high temp fabric. Depends. 6) Solder the ground strap to the board we leaded solder. I won't use that lead free stuff for home use. 7) attach probe and measure.
Still not a great setup, but consider these are pretty slow edges we are dealing with. Here was a home made probe where we were playing with much faster edges. I was attempting to get the ground inductance and loop as small as possible.
https://www.eevblog.com/forum/testgear/12-ghz-active-probe-project/msg5006290/#msg5006290
Gerhard_dk4xp:
< https://kh6htv.com/pspl-app-notes/ >
Most interesting reading. When the founder/owner of Pico Secod Puls Labs retired,
he sold the farm to Tek.
First thing that TEK did was to axe the app notes from the PSPL web site.
Probably too many independent comparisons. ;)
Gerhard
the Chris:
--- Quote from: David Hess on November 11, 2023, 02:12:48 am ---
--- Quote from: the Chris on November 10, 2023, 07:38:40 am ---
My pulse generator from Leo Bodnar arrived yesterday, so I would like to contribute with my slow-but-I-am-loving-it EDUX1052A. (...)
--- End quote ---
I wonder where that aberration came from; it is much greater than I would expect considering the much faster settling time of the pulse generator compared to a 60 MHz oscilloscope. My guess is that the oscilloscope does *not* have a Gaussian or single pole response.
--- End quote ---
Yes, I did not expect to see this kind of overshoot on a scope with 50MHz bandwidth. For reference, this is the same pulser on the EXR104 I am using at work. This time without inline terminator in native 50R mode.
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