Parts are manufactured to the published AL values; permeability listed for each material is for reference only. All standard parts are manufactured to a ±8% inductance tolerance (AL value) with the exception of toroidal cores of outside diameter 0.44 inches (~11.2 mm) or smaller made with MS (Sendust) material. Toroid sizes with MS (Sendust) material with OD 0.25 to 0.44 inches have ±12% inductance tolerance and sizes less than OD 0.25 have ±15% inductance tolerance.
Toroidal cores are tested with an evenly-spaced full single-layer winding in order to minimize leakage effects. Powder cores tested with a small number of turns or turns that are not evenly spaced around the core will produce higher inductance readings than expected.
Refer to individual part datasheets for full dimensional tolerance, inductance tolerance, test winding and testing conditions. Magnetic curve graphs and equations listed on this website, published catalogs and datasheets have typical tolerance of +20%/-10%. Core loss characteristic curves and equations have typical tolerance of ±15%.
AL values are expressed in nanohenries (10-9 Henries) per turn (N) squared (nH/N2).
To calculate the number of turns required for a desired inductance (L) in nanohenries (nH) use the following formula:
Binning and marking in 1% grades is possible upon request.