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Re: Pitfalls of measuring components with the NanoVNA #measurement

 

Here is the method we use to measure very low impedances in PDNs (power distribution networks).

The figure and equation were extracted from the paper at the link below (authored by Istvan Novak and published at the 2003 Designcon in Boston).

The equation is reasonably accurate when the measured impedance is << than 50 ohms (say < 5 ohms). The parasites of the measurement cancel out during the vna calibration allowing accurate measurements at very low impedances.

BTW, check out some of the other papers on the site. Many are relevant to VNA use.

-Ray
WB6TPU





On Feb 21, 2021, at 7:30 AM, Arie Kleingeld PA3A <pa3a@...> wrote:

?The Low-Z measurements.

The way to do that is using S21 measurement and short CH0 to CH1. Then switch the low-Z impedance parallel to that. Ofcourse calbration is necessary for Z=infinite and Z=0, just like the normal S21 calibration.

Enclosed are Excel graphs of S11 en S21 together.


For you information: 0,2 ohm = 5 times 1 ohm in parallel, 0,33 ohm is 3 resistors of 1 ohm in parallel.
Just to give you an idea of the simple measurements and performance of the H3.2 on HF.

Of course the S21- file needs to be saved and imported into Excel and then calculate The S21 values to value of R.


73,

Arie PA3A

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