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500ppm LCR meter: BOM/Schematic Errors & assy notes

Equipment, circuits, projects, procedures

Postby ricks » Thu Jul 11, 2013 12:00 am

Hello Folks & Jean-Jacques,

I have assembled/soldered the meter pcb's, all but one part that I was short because of my error, need 3 of OPA365, so am currently stuck at the Offset adjustment procedure because I am missing the OPA buffer that drives the diff ADC. Also need some Kevin cables, so have a set on order as well. I will get this OPA part today and solder it in and hopefully I can continue with the setup.
I found that the BOM as printed in May 2013 issue has a few errors:
1) 20R0 is to be a 1206 pkg, not 0805 as indicated. i did manage to solder a 0805 in the 1206 footprint however.
2) Schematic shows R31 to be 1K6, BOM indicates 750R. Since R31 is the only one that is to be 750, I assumed that the BOM is correct & schematic has the error?
I apologize if the BOM error was corrected in the .xlsx file, but I have a old version of Excel, so it will not read this new format (.xlsx).

P.S.
1) Would be glad to modify accordingly to fix the low R and low L measurement issues, as reported by others!!
2) Next rev, if there ever is one!! The 0805 footprint length could be opened up bit more, to allow for a proper toe on the solder fillet and a bit more solder volume on the pad land.
Cheers Rick
ricks
 
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Postby ricks » Thu Jul 11, 2013 12:00 am

See this thread for my continued journey of discovery.
Topic: 500ppm LCR: Bringup stuck at Sinus generator offset adjustment
ricks
 
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Postby eguy » Tue Nov 12, 2013 12:00 am

@ RickS: What do you mean with "20R0"? I don't see a resistor of 20 ohms in the BOM which I downloaded recently.

@ Jean Jacques: The issue about R31 stil exists. It would be nice if the correct value could be confirmed.
eguy
 
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Postby snoopy_94 » Tue Nov 12, 2013 12:00 am

R31 and C30 form a HF filter. I had tried different values such as 1.6kΩ and 1.5nF or 750Ω and 4.7nf. The important thing is that C30 is a NPO capacitor. With C30 = 1.5nF, R31 value may be 750Ω to 1.6kΩ!

Jean-Jacques
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Postby eguy » Tue Nov 12, 2013 12:00 am

Thanks for your answer Jean Jacques. Your promp reactions (in most cases) ar much appreciated! And, I must say, in spite of the flaws, I very much admire you for your creating this project (500 ppm LCR-meter).
eguy
 
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Postby hadihf » Wed Nov 13, 2013 12:00 am

Hi,

RF inductors have L specified at some test frequency which usually is in MHz range. This meter has max test frequency of 10KHz and is not suitable to measure RF inductors. I measured a Toko 7k inductor with 0.27uH specified at 50MHz. This meter measures 0.22uH at 10Khz which is probably OK.

Regards
F
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