Electronics > Beginners
Dirt cheap and simple scope-based component tester - curve tracer
george graves:
Love the video - it was so easy to follow along. Really great stuff.
Is there any reason why I can't use a function generator to generate the test signal?
Fraser:
George,
If you take a look at the "ACTracer FG" webpage link that I provided earlier in the thread, you will see that the designer of that unit has added the capability of an external function generator as the excitation oscillator. The ability to change frequency is useful when testing capacitors of varying values.
Aurora
opticpow:
--- Quote from: Aurora on June 09, 2012, 11:20:07 pm ---
The Hameg oscilloscopes used to include an 'Octopus' mode in their design, named a Component Tester mode (CT for short). I have always thought them forward thinking to have done so. You can often pick up an HM203 series 20MHz CRO for a very low price or even free if you are lucky... if you do, you get a simplified version of the Huntron Tracker included for free !
--- End quote ---
I'm happy to say that the current series Hameg Scopes still include the component tester as standard as can be seen on my HMO724.
Cheers,
Wayne.
w2aew:
--- Quote from: george graves on June 11, 2012, 07:04:54 am ---Love the video - it was so easy to follow along. Really great stuff.
Is there any reason why I can't use a function generator to generate the test signal?
--- End quote ---
George - in this very simple Octopus design, the only reason that you can't directly use a function generator is because the scope's Ground reference is not connected to either side of the signal generator (the transformer in this case). On a function generator, the output is generally earth referenced. Of course, you could use a transformer at the output of the function generator.
To tell the truth, I didn't have a 6.3V transformer as shown most online Octopus schematics, and I was playing with different test frequencies, so I was really using a my function generator to drive the secondary of the 12V transformer that is shown in the video, and the primary was driving the simplified circuit. Thus, I was able to use very little drive from the function generator, since the transform stepped the voltage up. I simply adjusted the amplitude on my generator as needed to get the output voltage I wanted. The transformer provided the earth isolation so that I could use the junction of the DUT and current limit/sense resistor as the ground reference.
jackasspenguin:
Hmm, while I'm considering buying a filament power supply I'm trying to think of a way to use something I either already have or buy something more financially appropriate. I'd love to build this. Although I would rather not have an 8lb iron core step down transformer to live with it. I mean in reality, if I had a filament transformer I'd rather build a tube amp to put it in. So my considerations would be something like this perhaps... This is a 220V input 12V AC output transformer, but wouldn't the output simply be half of whats rated? 110V ac input you'd get 6V AC out right? I Googled octopus component tester and what I found asks for 3 volts off the center tap of a 6V ac transformer. I'm just not sure what values or component I'd need to tweak in order to conform the circuit to suit the power supply. I'm not dead set on this power supply. I just thought there may be something out there over the shelf that might be a better choice. Johnny W :)
http://www.ebay.com/itm/20W-Max-220V-to-12V-AC-0-086A-Home-LED-Light-Power-Supply-Electronic-Transformer-/400303095053?pt=LH_DefaultDomain_0&hash=item5d33ec7d0d
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