Hello,

I found this video on youtube:

There circuit I have drawn and attached. I am not too sure how this works. I have been learning about oscilloscopes and that the ground on both channels is connected inside the oscilloscope. This would be zero volts between the two grounds and a short circuit. The circuit would have 1Mohm between the unknown component and 10ohm resistor. I am not sure how this would work with both grounds attached either end of the 1Meg resistor. The 10ohm would have a negative voltage across it and the unknown device would have a positive voltage across it. The 1Meg resistor would drop most of the voltage across it.
I tried to analyse it by putting a 10 volt source at 1kHz in. If the unknown component was a 10uF cap it would have a impedance of 15.9 ohms. Adding this in series with the 1M and 10 ohm resistor, wouldn't make a lot of difference. The current through the circuit would still be small because the 1M resistor is so high. So a current of 9.99uA roughly through the circuit. The 1M would drop about 9.99 volts across it and the 10 ohm would drop about 99.9uV.
The current across the 10ohm is still approx 9.99uA. In the video the lady calls the 10 ohm a sensing resistor. I looked at sensing resistors and know that this is a direct method of measuring current, it is part of the circuit. The voltage is proportional to the current, from ohms law.
Is any of this correct?

Thanks

Simon

 

View the video in utube and read the comments.
Google 'octopus curve tracer' to find circuits that will actually work.

 

https://www.olymega.org/forum/viewt...cer&sid=3fed8b99f7479932aa57df67905fe739#p421

I'm Polymorph on that board.

I built a component curve tracer with a transformer from a microwave oven, the one that powers the control board because it has multiple voltage taps on it. If you are interested, I can look for the schematic I drew up and post it here, if you wish.

Mine is not nearly as complex as this one:
http://www.techlib.com/electronics/curvetrace.html