LCR meter for sub 10nH inductors?

[G0HZU]

Another methodological question:

What are you doing that needs accurate values around 10nH? Surely you're dealing with transmission line segments by then?  Would it not be better to evaluate the system (filter or whatever) as a whole, not on a per-component basis?

In which case, a frequency sweep, spec + TG, network analyzer or whatever would be the way to go.

Tim

In my case, I would use sub 10nH inductors for the design of lumped RF filters up at UHF. Eg at a GHz or so.

I'd normally use SMD parts and model each inductor individually as a 1 or 2 port model and do the same for capacitors and also use an EM simulator to model the PCB layout.

It's possible to get very good agreement between a filter/PCB model and the real filter circuit when these procedures are carried out. So normally I would model a small inductor as a 1 or 2 port s parameter file based on measurement data taken from a VNA across several GHz.

[Solder_Junkie]

I've recently been working on the design of Cauer low pass filters in the HF frequency range. Getting the toroid inductor values correct is proving quite tricky. The usual low cost LC meters use 500 KHz as a test frequency, which is OK for the lower frequencies using Amidon "2" cores, but gets increasingly inaccurate as you go higher in frequency.

The best method of measurement I have found is to wind the inductor based on the formula/chart then use a small 1% capacitor which is estimated to bring the inductor to resonance near the frequency it is to be used,  measure it's resonant frequency, then calculate the unknown inductance -however, this is quite tedious. Neither winding the toroids based on a formula, or using a basic "500 KHz" meter,  seem very accurate.

Adjusting the turns spacing of a coil while observing the results on a spectrum analyser/tracking generator sometimes leads to poor input matching.

Is there an easier way to get the inductors to the correct value?

[reagle]

It's been a while, but I finally ended up getting a Keysight U1733C 100Khz LCR. It works surprisingly well for my purpose- to be able to roughly confirm that the inductor I am about to solder on the prototype is indeed 5nH and not 10nH for example.  I tried a few benchtop units (lowish range ones) and ended up getting the high end handheld instead

[dannyf]

Looking for an LCR meter that could handle measuring inductors down to nH

Consider measuring it through an oscillator.

[cdev]

I'm interested in conical inductances.

They have useful properties with regard to self-resonance.

[RFDUK]

Here is low cost but very capable solution to measuring low inductance with impressive accuracy and repeatability, the HP 4342A Q-meter. Mine cost about £200 each and have been in regular use over about 15 years.

The direct dial calibration provides a bottom end of 85nH, but by dialing in the maximum frequency of 70MHz and using a manual calculation from the capacitance dial, I can measure down to a couple of nH.

For surface mount I use an FR4 jig as per the photo. Shorted with copper tape, this calibrates to about 14nH and is deducted from the calculated inductance of a component under test. Just measured a 4.7nH 0603 wire wound inductor as 5.2nH, Q 47 at 70 MHz.  Also measures Q up to 1000.