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| Accuracy of LCR meter? |
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| Martin72:
--- Quote from: bd139 on July 01, 2022, 05:51:39 am ---Ergo it’s better not to worry about a couple of percent and a few counts and work out what the tolerance and device spread of your design is and make sure you window values within that. --- End quote --- Exactly. You won´t design a coil into a circuit with a tolerance under 5% in most of the cases. The AL value of the used core makes it impossible for mass production without cost intensive pre-selections. So tolerances about 20% are not uncommon - Every LCR should handle this.. Of course there are some exceptions, e.g. coils for filters to suppress unwanted harmonics. We (company I work for) make most of our used coils and transformers ourselves. And test/adjust them. We got several different LCRs and therefore different values of the same coil. ;) For the most the measuring with one of the LCRs are enough, for other we use resonant test circuits* for adjusting them. Further we use Voltage-Time-Area function** or, with our self build tester, testing coils with large currents up to 200A***.. Based on this experiences, I can recommend LCRs building like the DE 5000 for most of the needs of a hobbyist. Martin *) Example: Filter-Coil, Air-Gap adjustment to reach given value 90µH +/- 3µH. Using resonant circuit with additonal cap of 10µF/1%, adjust amplifier to 10Vrms, adjust airgap in such manner, that on 1.64....1.65khz the flowing current gets his minimum value. **) Special case, self satured coils for zero switching, define windings on the coils per feeding in an impulse with high voltage, use math from scope, building integral function for voltage-time-area. ***) High power coils for output filters....normal LCRs didn´t have current, only a few mA max, our self build tester can deliver pulse-current up to 200A, adjustable. The circuit based on a µC, some electrolytic caps for the current and a IGBT for switching. L will be calculated based on the formular L= U*t/I (linear current is a must of course) |
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