Inductance Measurement

[chunlee]

1nh measurement

May I know PNA network analyzer can measure inductance less than 1nH? such as 0.5 nH accurately? Somebody try before?

Thanks.

 

[vfone]

inductance measurement technique with 1nh

No, is not accurate below 1nH.
For greater accuracy try to use a dedicated LCR meter.
**broken link removed**

 

[chunlee]

Hi Vfone,

What is the uncertainty if I use PNA to measure sub-nH inductor? below 10%?

 

[vfone]

Below 1nH I would go for an accuracy no better than +/-30% (maybe worst).
Inductance measurement in a PNA is an indirect measurement, calculated from an impedance measurement.

 

[madengr]

You can use a VNA to measure inductance. You just need to measure at a high enough frequency so 1 nH presents a impedance near 50 ohms. That also means you need a good calibration. You can use either 1 port or 2 port measurements, preferably both.

The 4287A is just a 1-port VNA anyway. The bridge type LCR meters are probably too low in frequency to measure 1 nH, however they are very accurate for certain ranges.

You don't have to measure the inductance directly. You can resonant it with a known capacitance and measure the suck out. There are methods using transmission lines too. One method may be better a finding the Q, another better for L or SRF. You need to research the different methods.

 

[chunlee]

Hi all,

Thanks for your reply.

In this case, I would prefer to measure L and Q over wide frequency band. Hence using LC oscillator is not suitable for my application.

But madengr gives a very good idea: Is it if |Zin| near to 50ohm, measurement accuracy can be greatly improve, assume inductor are measured using 2ports VNA?