Inductance meter

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I ordered an LC100 via Amazon which showed up quickly. A premium over the eBay price but the fast shipment is worth the extra $7 or so.
It works and seems to have potential but its calibration is off and the errors increase as the value increases. Its more accurate if I do not Zero it. This came with no instructions so I'll need to chase them down.
in any case as delivered, checked against a reference CDE cap decade- 100 pF to 10nF 2% (verified) the readings are typically 10% high all the way up.

Hi C range measure 5% low.

If I can find info on proper calibration I'll calibrate and recheck. As is its not really useful And if they all need a real calibration I may start a small side business supplying stable cal standards for these.
 
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OK, the junk box yielded 1% parts for the three reference components. I managed to fit them and now it measures reasonably close in a 2-5% sense. It won't replace my ESI Videobridge but could be useful for quickly identifying a part on the bench. I would not use this for a small inductor or a small cap if precision is required. In the small parts frequency has significant influence as does many other things. The best instrument for that would be a Tek 130 LC meter which was designed to measure interelectrode capacitance in tubes.
 
Very interesting! THANKS for posting! However, it is almost painful to watch the dude in the "Faulty LC100-A" replace the surface-mount IC---he's worse with soldering these small components than I am, and I'm an old fart with not-so-good eyesight!! Not exactly clearly evident in the "Hackaday" video, but evidently replacing the cheap surface mount components with some quality Murata and Wima Thru-Hole parts helps significantly. I will definitely do that, as the parts are only <$2 TOTAL!!!
 
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Mine had a quality TI lm311 it seems and it doesn't seem to be an issue. The caps were both off by 10-20% and the inductor was off by 50%. Without the ESI I would have been chasing hard to get parts but the junk box yielded 1% 1nF and 100nF parts i acquired many years ago and a small pile of random inductors in which I found a 100uH inductor. Now it measures my GR reference 10H as 10.09H, really good. Low C and High C are OK, not great.
The soldering was painful to watch and seems pointless. If you know what you are doing just point at the parts. If you don't, watch a video on soldering. Its not that hard.
 
..... The caps were both off by 10-20% and the inductor was off by 50%. .......the junk box yielded .......a small pile of random inductors in which I found a 100uH inductor. Now it measures my GR reference 10H as 10.09H, really good. Low C and High C are OK, not great.
I can buy a lot of 10 of each of the capacitors (2.5% and 5%), and with my trusty B&K capacitance meter, probably get pretty close to 1%. But I can't seem to find any 100uH inductor at <10%. How close were the uH measurements after you up-graded?
 
Just to support jackinnj's comment about REW. I have just been through a setup phase with my EMU0404 soundcard and confirmed it is not only simple and accurate for measuring passive R, L and C parts, and of course electromechanical speaker devices, but also for more complex parts like valve amplifier output transformers where frequency spectrum impedance plots show inductance variations with frequency (including leakage inductance) as well as high frequency resonance effects out to 96kHz (if you have a suitable soundcard) and with an accuracy that is dependant on your best accuracy tolerance resistors used for calibration - as such, that form of tool is on steroids compared to single frequency small signal measurement tools.
 
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Thanks a lot jackinnj
(earlier today I found some notes from 2008 referencing this Omicron App. Note but haven’t found the App. Note itself).
I will read it carefully, and will do in due time REW impedance sweeps on one of the transformers I had measured manually in the past( Implementing a “Y Out” on an Oscilloscope ). I will setup an Excel spreadsheet and see how it goes.
Thank you again.

George
 
In attempting to find the best 100uH 5% inductor for the LC-100 meter, I am finding the specs a bit confusing. I would think that the higher the Q factor, the lower the DC resistance and therefore the most accurate. But the specs on the inductors I am finding seem to go the exact opposite way---the higher Q inductors have MORE DC resistance. Why is that?
 
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What Steve wrote above.
If you run an impedance sweep on the choke and then extract real and imaginary parts of Z, you will focus on the real part variation with freq.
There, apart from the DCR (constant) and the skin and proximity effect (rising with freq) of the winding, you will also see the core loss contribution which is related to the composition of the core material.

George
 
Well, I got my little (80x50x30mm) Chinee LC100-A L/C Meter today! The good thing is....it DOES work!!
The bad thing is....it's not terribly accurate---per my B&K capacitance meter, about 3.5% on LARGE (47,000uF) capacitors, but about 15 % on lower value caps (0.1uF). I have no reference for inductors, but it does give a reading on all I've tried. SO....next I will replace the 2 capacitors on it with 1% polypropylenes, and replace the inductor with the best I can find for 100uH, which is 5%. All in all, though, not bad at all for $14!! Would be nice to find a little box for it; I'll look around. One guy on the internet also suggested a 7805 regulator and a 9 volt battery (it runs off of a USB connector now), which prolly ain't a bad idea.
 
Well, I got my little (80x50x30mm) Chinee LC100-A L/C Meter today! The good thing is....it DOES work!!
The bad thing is....it's not terribly accurate---per my B&K capacitance meter, about 3.5% on LARGE (47,000uF) capacitors, but about 15 % on lower value caps (0.1uF).
I've been using these generic LC100-A LCR meters for a couple of years. They are the best value out there for a simple easy-to-use LCR meter which will measure a wide range of both capacitance and inductance.

There ARE some issues with getting accurate readings from the LC100-A:


1) MOST IMPORTANT: None of the published "self-calibration" instructions are complete. They all omit a critical step (calibrating with probes shorted together)
Here is the correct (and only) way to self-calibrate the "small capacitance" range of the LC100-A:

Mode: “small C.” All buttons released
Probes open
Press/hold Zero button until “data saved” appears in display
Next: Short probes together
Again press/hold Zero button until “data saved” appears again
The highlighted calibration step (with probes shorted together) is the key to getting accurate readings. If this calibration step is omitted the accuracy will be absolutely awful when measuring capacitors >.047uF

Quick sanity check for "small C" mode:
With probes open the readout should be <5pF
With probes shorted together the readout should be "over range"​


2) The quality of the LC100-A toroid reference inductor varies enormously depending on which vendor the LC100-A came from.

The original manufacturer of the LC100-A is MingHe. Their units have a white label underneath the PC board with the MingHe logo on it. Genuine MingHe units have turned out to be very accurate. Note, however, that the full "small C" calibration procedure must still be followed (calibrate with probes open followed by calibrating again with probes shorted). Even MingHe doesn't provide proper instructions for"small C" calibration.

It turns out the uH value of this inductor isn't nearly as important as its "Q." I've replaced the inductor in a couple of "generic" LC100-A which originally came with low-Q inductors. After installing a decent quality inductor they became as accurate as genuine MingHe units. Note: The uH value can be anything from 47uH to 100uH. The Q of the inductor is what's important.

I started a thread for the LC100-A on the "Antique Radio Forum" a couple of years ago. Since then several other forum members confirmed my observations and added additional information. That thread can be read here:

Antique Radio Forums • View topic - LC100-A, LC200-A, and similar low-cost digital LC meters?

-EB
 
Thanks for posting the link to the Radio Forums' thread on the LC100-A meter! I read through the whole deal, but I'm still not totally sure what inductor to use. Indeed, it appears that the inductor used on the no-name-brand of LC100 is of poor quality on a powdered iron core; much better results were obtained with shielded inductors with ferrite cores and high Q. Most posters reported that their "stock" inductors were closer to 47 uH, despite the schematic's posted value of 100uH, and one fellow reported that inductance values between 47 and 220 uH didn't affect measurement accuracy much. However, another guy said that his conclusion was that accuracy was best when he adjusted a variable inductor until the LC100's internal oscillator operated at ~500KHz. Unfortunately he didn't say what that inductance was. In any case, an inductor that provided the highest amplitude test frequency was deemed to be the best. My best guess from this is to use a 47uH high Q shielded inductor with a ferrite core. Anyone else come to a different conclusion?