Soft Shoulders and Dangerous Curves

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CJ

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Jun 3, 2004
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I accidently hooked up the scope wrong when doing some B-H curves on a transformer and I got some really starnge curves. They almost look like some polar equations that I use to plug into some graphing software:

weird_1.jpg



weird_2.jpg


weird_4.jpg
[/img]
 
Yes, they are real.
Here is the schematic. The scope probes on the secondary should have gone across the cap, not the resistor.
Use a poly cap if you want to experiment at home.
Your scope must have the "Persist" option, which goes over the same trace over and over and thus fills in the very faint traces.
Use x-y mode, not x-t time base.
cj

weirdcurve_setup.jpg
 
These look a whole lot like phase plane plots, where you plot the signal on one axis, and the derivative (rate of change) on the other axis. A good engineering tool for determining limit cycles, and other phenomenon.

Cheers,

Kris
 
I've been busy...mostly with the day job. But on the DIY front I am 3/4 through the construction of an 18W Marshall clone. I've been in 'lurk' mode here for the past couple months with hardly any time to post responses.

I am starting to order parts for the Forssell comp though....

Cheers,

Kris
 
Yeah, who says transformers aint musical?
Looks like a treble cleff to me, eh?
I was in a hurry so I did not take pics of all the weirdmess.
There were a ton more.
 
[quote author="cjenrick"]
weirdcurve_setup.jpg
[/quote]
Nice curves, but bad connection.
You measure B-H curve.
H is simple input resistor drop.
derivation of B is output winding voltage.
But you want to draw B. Then must output voltage INTEGRATE =
connect scope input to C.
(At your schemo you derivate, if you scope drop at R in RC network)

... And measure with somewhat like sinus.

Late reply, I had problems with connection
xvlk
 

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