Marco is correct. The inductance L does not change with frequency (except
for the small non-linear effects of the core materials).
HOWEVER, all real inductors also have parasitic capacitance and resistance,
which causes the Z (impedance, not inductance) to change with frequency.
And these effects are real, and can be quite large. So when the VNA
measures an inductor across a frequency range, you will see the impedance
(not inductance) change from something close to the pure 'L' inductance at
very low frequencies, to where the parasitic capacitance completely cancels
out that inductance at higher frequencies (at the LC resonant frequency)
and then the C becomes dominant at even higher frequencies. So it is often
useful to measure this impedance (or apparent inductance) at the frequency
the inductor will be used - where the modeling of its required valued was
done.
At DC and low frequencies, the Z of an inductor is dominated by its
inductance, and the Z and L are essentially the same. But at higher
frequencies the Z will be dramatically different, and depends highly on the
materials and construction techniques used in the inductor.
The nanovna and other vna's (and/or the software used to control them)
calculate the Z from the measured S11 or S21 parameters, often with a good
degree of accuracy. Then they calculate the L from the Z. There are more
limitations to the accuracy of this calculation.
A good LCR meter is likely a better tool to measure the 'L' of an inductor.
Stan
On Mon, Jul 18, 2022 at 10:11 AM Marc et Nicole Feuggelen-Verbeck <
f8voa54@...> wrote:
What you say is correct but that is nitpicking : The value of an
inductor does not change with increasing or decreasing frequency . 100?H
now equals 100?H just as 100KOhm is equal to 100KOhm .
If not , the laws of physics must be rewritten . F=1/2(pi)(sqrt(LC))
An inductor is *a passive electronic component that stores energy in the
form of a magnetic field*. In its simplest form, an inductor consists
of a wire loop or coil. The inductance is directly proportional to the
number of turns in the coil , the used materials and the envirement but
not the frequency.
End of story
Marco
Op 18/07/2022 om 15:42 schreef Jim Lux:
On 7/18/22 2:20 AM, Marc et Nicole Feuggelen-Verbeck wrote:
The value of an inductor is a given and depends on several factors,
but CERTAINLY NOT on the frequency
An ideal inductor, perhaps, but any sort of practical real inductor
with parasitic C between turns and the surroundings varies with
frequency. The loss also changes with frequency due to skin depth
changes (although that's a small effect).
There's also a small inductance change effect due to different
distribution of current in windings due to skin effect.
Finally, if the inductor is on a core, pretty much every core material
has frequency dependent properties.
--
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