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Recommendation for low cost LCR meter

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kc1980:
Can anyone recommend me an inexpensive LCR meter for hobby use?  I'd prefer a hand-held over a bench unit.  Thanks in advance.

...or, maybe I should make one???  ;D

alm:
I believe the leader in the hobbyist market is the AADE L/C meter. It doesn't do the R part, only L and C. It's available as a kit or pre-assembled. The build quality is not on the level of a professional case, but better than many hobby projects. I like the high resolution, I can accurately measure a few pF (assuming the parasitic capacitance in my test setup is constant). It's much better than the capacitance range of my Fluke DMM's in that respect. It won't do large capacitors (like most electrolytic caps), but I don't often find a need to measure them anyway. For testing for broken ones, an ESR meter is much more useful. >1uF capacitors are rarely in places like filters were accurate capacitance is important.

Polossatik:

--- Quote from: kc1980 on May 05, 2010, 12:16:21 am ---
...or, maybe I should make one???  ;D

--- End quote ---

I don't have this, but the http://electronics-diy.com/lc_meter.php looks pretty neat.
I found no download of the pic source code, but they sell kits.

kc1980:
I have somewhat of a theoretical question regarding impedance.  Are the resistance, capacitance and inductance of real-world, non-ideal discrete resistors, capacitors and inductors (respectively) frequency-dependent?  I understand that reactance is proportional to frequency, but what about the actual value of L or C, which is ideally constant.  I'm assuming that it does change with frequency, but is the effect negligible?

This leads to my next question: What frequencies are typically used to measure R (i.e. ESR), L, C?

Thanks!
Ken

mkissin:
Yes, they can be heavily dependent on frequency, but that's a sweeping generalisation that will be of no real help to you.

Take the easiest case: resistance.

The resistance of a small, straight piece of single-stranded copper wire at DC at 25° is really simple to calculate. As soon as you put AC into it, that value is no longer valid. Skin effect (which is itself a complicated magnetic thing) dictates that the current will tend to flow preferentially at the surface of the conductor, meaning that less current will flow in the centre of the conductor. Take that a wee bit further and you can get to a high enough frequency (which often isn't that high, a few kHz) where there will be no current flowing in the centre of the conductor. Which means you might as well use a copper pipe rather than a solid piece of wire. The AC resistance will have increased due to the fact that you now have less area of copper which is actually being used to conduct the current.

Capacitance and inductance also vary wildly with frequency, but are much more complex as you now have to take into account the properties of the dielectric material of the capacitor, or any core material used in the inductor. That's in addition to the geometry of the component itself. Often your choice of package will have a large effect on how well the component performs over a frequency range. Surface mount capcitor packages will naturally have lower values of parasitic inductance than through-hole simply due to the lack of long leads.

In extreme cases, the inductor you carefully wound can end up looking like a resistor (at one very precise frequency), or even a capacitor!

Typical test frequencies offered by cheaper test equipment are 50/60Hz, 1kHz, 10kHz, and sometimes 100kHz. Ideally, you want to measure the properties of your component at the frequency it will be operating at.

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