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.
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.
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/xwink.gif.pagespeed.ic.cldandycH0.png)
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)