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500ppm LCR-meter - V 3.0.0

Equipment, circuits, projects, procedures

Postby ricks » Tue Nov 05, 2013 12:00 am

Fixture looks good Kjell, methods sound fine, so as before, you have found out the limitations of this equipment and it basically does not perform as advertised.
And I was thinking that when I measured 100nH it had to be my kelvin probes.
Makes you wonder, how in the world they came up with a spec for
when it is having so much difficulty in measuring 100nH.
I can only think it is a printing error and should be 0.1uH on the low side.
Now that I look at the L measurements, looks like they purposely did not measure/report L values at the extremes.
I suspect that these finding will be ignored, as before and things will be silent, or saying that we are nit picker.
Over all, I am fine with my investment, but a bit unhappy that this device was not fully tested, to the published specifications, and they did not uncover/report it's deficiencies or limitations during testing.
Like most stuff, you get what you pay for. Even then, you have to do your due diligence by doing your own testing to verify claims.

Take care
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Postby hadihf » Tue Nov 05, 2013 12:00 am

May be I am wrong but for the above setup, I think when measuring small inductances, any flux remains, and PCB base material properties will also effect the results. Best is to hold a clean DUT in two pointed tips in air with low humidity at 25degC. Also each time heat is applied the value changes a bit. I have checked it many times and it always happens, particularly for inductors, even NPO ceramics show very small change.
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Postby snoopy_94 » Tue Nov 05, 2013 12:00 am

The measurement of very low L is not simple!
The first thing is to have a non-deformable fixture. Indeed, with your, you can easily see that the simple act of moving a bit coaxial change the measured value. It 's virtually impossible to have a good Trim-short, the absolutely necessary condition for accurate measurement.
The second thing is to use a frequency test in line with the ratio reactance / resistance. I have a few 82 nH (0805) with series resistance of approximately 350mΩ. At 10 kHz the reactance of an inductance of 82nH is 5mΩ! It is difficult under these conditions to have accurate measurement of L, because it is the secondary parameter.
You are right, the 0.1nH in the spec is a typo, it is the resolution not the low range value. Low range value, for accurate measurement, is about 200nH (ideal inductor, not in the real life!).
The only real solution is to use higher test frequency (100kHz or better 1MHz), but it's an another tool!

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Postby hadihf » Thu Nov 07, 2013 12:00 am

Fab Done...caliberation to make test leads.
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Postby hadihf » Tue Nov 12, 2013 12:00 am


I made the preliminary probes (waiting for Kelvins from China..)
I measured 0.012 ohm 1% resistor as 0.013 ohm. This is without hardware mod. For probes..

1- The shield of coxial cable should be of good quality with tightly woven thick mesh.
2- terminate the cable shield 1~2mm from end and make test points as small as possible.

I checked almost my whole inventory and the meter measues everything within tolerence.

I can hold most components in these jaws!

Thanks JJA and EE for this great project.

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Postby hadihf » Wed Nov 13, 2013 12:00 am

Impedance changes considerably with frequency but ESR little.
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