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Old 10th June 2012, 06:02 PM   #251
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by jackinnj View Post
you'll improve the contrast of the pictures if you put some black tape over the foil facing the scope.

My Canon G12 has a "TV" setting which is useful when I pull pictures off the 576 curve tracer, 2465B or HP3577. You can then use "Graph Grabber" to obtain XY values for spice models. Much easier to use than my Fuji D-Cam.
I have a G10 and it seems it doesn't have such feature.
I have to play around with the exposure and speed to ensure the refresh is not a problem. Unfortunately the phone camera is useless here as refresh is an issue.
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Old 10th June 2012, 06:09 PM   #252
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you'll improve the contrast of the pictures if you put some black tape over the foil facing the scope.
Yes, the darker the better. Need to do that.

Quote:
Originally Posted by jackinnj View Post
You can then use "Graph Grabber" to obtain XY values for spice models. Much easier to use than my Fuji D-Cam.
As an alternative you can use Engauge Digitizer. What I like about it is that when you export the data you can set it to extrapolate the y values from the x grid points. I take this data into program called Graph where I can easily draw load lines and plate dissipation curves.

Alfredo
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Old 10th June 2012, 06:38 PM   #253
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Originally Posted by avincenty View Post
Yes, the darker the better. Need to do that.



As an alternative you can use Engauge Digitizer. What I like about it is that when you export the data you can set it to extrapolate the y values from the x grid points. I take this data into program called Graph where I can easily draw load lines and plate dissipation curves.

Alfredo
Hi Alfredo,
Tried Engauge digitizer and is really easy to extract data for Excel, etc.
Which is the application "Graph" you are refering to draw loadlines, etc.?

I use Dmitry's tool to create SPICE models, and after a bit of practice you can create very accurate models...
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Old 20th September 2012, 02:51 AM   #254
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Ale,

What did you end up for the current sense, is it just switchable 1R and 10R? And is the return of the sense resistor tied to one end of the rectifiers as Merlin suggested? Also, what're the Ia x1 and x10 switches on your control panel, is it a 10x voltage amp?

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Jaz
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Old 21st September 2012, 09:08 AM   #255
mogliaa is offline mogliaa  United Kingdom
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Ale,

What did you end up for the current sense, is it just switchable 1R and 10R? And is the return of the sense resistor tied to one end of the rectifiers as Merlin suggested? Also, what're the Ia x1 and x10 switches on your control panel, is it a 10x voltage amp?

Thanks,
Jaz
Hi Jaz,
Yes, current sensing is 1R and 10R. Typically I use 1R for most valves, unless testing low current / low transconductance valves as 10R may be better subject to scope input sensitivity and environment noise. 90% of the time I use 1R, but at some points during the day I switch to 10R given mains noise, etc.

Havent implemented return as Merlin suggested, a very good idea though.

x1/x10 switch is for my diff amp picking up the voltage across the sensing resistor. I had this circuit build beforehand so reused it here. It gives more flexibility to use the tracer with any oscilloscope...

Keep posted on progress!!
Cheers,
Ale
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Old 21st September 2012, 01:55 PM   #256
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Hi Jaz,
Yes, current sensing is 1R and 10R. Typically I use 1R for most valves, unless testing low current / low transconductance valves as 10R may be better subject to scope input sensitivity and environment noise. 90% of the time I use 1R, but at some points during the day I switch to 10R given mains noise, etc.

Havent implemented return as Merlin suggested, a very good idea though.

x1/x10 switch is for my diff amp picking up the voltage across the sensing resistor. I had this circuit build beforehand so reused it here. It gives more flexibility to use the tracer with any oscilloscope...

Keep posted on progress!!
Cheers,
Ale
Will do, I am still debating if I should use my tube tester as the "platform" and just build the grid drive circuit, or go for a scratch build...

Thanks,
Jaz
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Old 21st September 2012, 03:24 PM   #257
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Originally Posted by jazbo8 View Post
Will do, I am still debating if I should use my tube tester as the "platform" and just build the grid drive circuit, or go for a scratch build...

Thanks,
Jaz
Tube tester has a "short" test which is the first test you should (always) perform!

I just got an Arduino Leonardo which is going to form the basis of a new, open source, tube and transistor tester.
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Old 21st September 2012, 03:40 PM   #258
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Which is the application "Graph" you are refering to draw loadlines, etc.?
My apologies Ale, never saw the notification for this post.

This is the link to the Graph application Download | Graph

Alfredo
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Old 21st September 2012, 03:57 PM   #259
mogliaa is offline mogliaa  United Kingdom
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Originally Posted by jackinnj View Post
Tube tester has a "short" test which is the first test you should (always) perform!

I just got an Arduino Leonardo which is going to form the basis of a new, open source, tube and transistor tester.
Yes, agreed. I'm thinking of adding either a classic neon testing point or a transistor sensing circuit similar to the Sussex valve tester. I do have a tester, but is always handy to identify leakage before attempting any curve tracing work

RE Arduino, that is a great option and would be great to hear progress on that!

Ale
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Old 21st September 2012, 03:57 PM   #260
mogliaa is offline mogliaa  United Kingdom
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My apologies Ale, never saw the notification for this post.

This is the link to the Graph application Download | Graph

Alfredo
Thanks Alfredo, will look at this!
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