You can make your own even simpler since the relationship in high pass filters are:
http://www.play-hookey.com/ac_theory/hi_pass_filters.html
So you can build this very quickly and measure either capacitance or inductance; getting a meter really matters if you don't have the time to calculate it as listed here:
https://www.eevblog.com/forum/index.php?topic=533.msg7756#msg7756
That's good math work, safri, but the equation to use is different and far simpler.
Notice how all LCR meters use a specific freuquency for a range of C or L, that's roughly how this works.
Resistor here is a constant, use any thin film or carbon composite. Don't use wirewound as its a inductor too.
Now, put your unknown capacitor or inductor in the circuit above, as necessary.
Get a function or audio generator generator as Vin, and measure its output Voltage with a scope for say 500kHz or 500 Hz, just to copy the frequencies the device in the original post used. Say adjust it for 1 Vp-p so its easy to read.
If your cap is as big as your pinky or your inductor is fairly large, use the 500 Hz.
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.
Now that you have fc, substitute it algebraically into the equation and that's your L or C.
Units:
fc= Hz
R = ohms
C = farads
L = henry
For example, you have an unknown small inductor.
Use the inductor high pass circuit above. You have some resistor lying around that is 500,000 ohms.
You pass 500kHz into it and it comes out 1V p-p. Adjusting frequency down [ since its a high pass filter its already passing everything ABOVE the cutoff] , at 300kHz the Vout is 0.707 p-p.
Solving:
L = R / 2 x pi x fc
L = 500,000 / 2 x pi x 300,000 Hz
L = 0.265 H or 265 mH.
As alm and I suggested in a old post, most hobbyist only need a good scope, like the Rigol 1052E, a function generator, a good DMM and PSU. An LCR meter is nice to have, but if you don't measure C or L often, and a good DMM comes with C meter already too, you can rig one up fairly quickly and get very accurate results with it.
Some modifications of the same rig can calculate ESR, DF, and Q too. But they can be more tedious to do on-the-fly, so it would be worth it to buy or build an ESR meter than a LCR meter without ESR built in.
http://octopus.freeyellow.com/esr.html
Get a function or audio generator generator as Vinok, the explanation and implementation seem simple. but the above quote... is a "houston we have a problem" thing. i dont have any. is there a way generating controlled Fc/Vac through a mcu?
I think using a square wave makes things needlessly complex, since square waves are composed of many harmonics, and the attenuation of the filter is different for the various harmonics. I would stick to sines. You could make an RC oscillator , or use some sort of audio source (don't expect great stability).
I consider a function generator a basic piece of electronic equipment, together with stuff like soldering iron, DMM and scope, so you may consider getting one at some point in time, low-spec used ones can be pretty cheap.
http://www.anatekcorp.com/testequipment/atlaslcr.htm (US distributor)
Get a function or audio generator generator as Vinok, the explanation and implementation seem simple. but the above quote... is a "houston we have a problem" thing. i dont have any. is there a way generating controlled Fc/Vac through a mcu?
I think using a square wave makes things needlessly complex, since square waves are composed of many harmonics, and the attenuation of the filter is different for the various harmonics. I would stick to sines. You could make an RC oscillator , or use some sort of audio source (don't expect great stability).
I consider a function generator a basic piece of electronic equipment, together with stuff like soldering iron, DMM and scope, so you may consider getting one at some point in time, low-spec used ones can be pretty cheap.
Suit yourself:
http://focus.ti.com/lit/ds/symlink/cdc3s04.pdf (5 bucks for a SPI controlled sinewave generator)
Or the ever popular XR2206:
http://www.exar.com/Common/Content/Document.ashx?id=16&LanguageId-1033 (VCO function generator)
Oops! Safri you should make it your mission to get a function generator when you can
I got a model 1003 for $US150 delivered, from tequipment.net.
I got a model 1003 for $US150 delivered, from tequipment.net.I've been eyeballing that, and the version that's ~$20US more expensive with 'voltage display'. It's good to hear positive things from a pro, as I feel I'm looking in the right direction. It's now officially next on my list after a scope.
QuoteOops! Safri you should make it your mission to get a function generator when you canI think he already has one. I believe he wanted to build an LC meter that did all of the calculation using a MCU, not to manually do it with a signal generator and DMM.
btw: any suggestion for a good but "programmable arbitrary anything shaped" function generator, in the range of less than $100-$300? if in case this is the final outcome for me? to buy a FG. or maybe i'm just dreaming for that price?
A post on eevblog:
https://www.eevblog.com/forum/index.php?action=search2didnt work.
the dds3x25 is Amplitude ±3.5V Max. by that alone, its not tempting
sorry, try this:
https://www.eevblog.com/forum/index.php?topic=197.msg1892#msg1892
or something else that will make 0.707Vdd observation near impossible to get the correct L or C value.