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Review: High-precision L/C Inductance Capacitance meter (35-50 USD)

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Mechatrommer:
the analysis is moved to https://www.eevblog.com/forum/index.php?topic=1869.msg25864#msg25864

alm:

--- Quote from: saturation on December 01, 2010, 04:08:02 pm ---Now connect the generator to Vin and the scope to Vout.  Adjust the output frequency precisely until the output voltage is 0.707Vp-p.  That's the fc.

--- End quote ---
I would probably measure both Vin and Vout with two scope channels (or DMM's if they're accurate at that frequency), to account for your circuit loading the generator's output circuit. Making sure the impedance is significantly larger than the output impedance of your generator (probably either 50ohm or 600ohm) is another solution.

vizer:
The move of some analysis and design (and maybe more to move, too) is surely appropriate, even if I am happy as punch to have had such fine material show up in a thread I started!

saturation:
Yes, these are very good ideas; if you have a Rigol 1052E you can put one channel each as Vin and Vout.

To minimize loading, its a good idea to use high resistance, 100x the expected generator and scope impedance, say 5000 ohm and up.

That said, there was enough curiosity in this that I tried measuring a few caps with the Rigol, as I used to do this with my old analog Trio scope.

I've posted my experiences on the 'design' thread.

Thanks a bunch alm for pointing out those reminders.



--- Quote from: alm on December 01, 2010, 06:56:21 pm ---
--- Quote from: saturation on December 01, 2010, 04:08:02 pm ---Now connect the generator to Vin and the scope to Vout.  Adjust the output frequency precisely until the output voltage is 0.707Vp-p.  That's the fc.

--- End quote ---
I would probably measure both Vin and Vout with two scope channels (or DMM's if they're accurate at that frequency), to account for your circuit loading the generator's output circuit. Making sure the impedance is significantly larger than the output impedance of your generator (probably either 50ohm or 600ohm) is another solution.

--- End quote ---

saturation:
You're very welcome, some analog approaches are far simpler than the digital and require just the very basics tools in a lab and a calculator.  But, a digital meter is something that makes life easier in the long run; if you had to measure caps all day, the method I show will eventually lead to user measurement error from repetitive measurement fatigue.


--- Quote from: vizer on December 01, 2010, 08:51:08 pm ---The move of some analysis and design (and maybe more to move, too) is surely appropriate, even if I am happy as punch to have had such fine material show up in a thread I started!



--- End quote ---

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