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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On 02/21/2021 6:30 AM Arie Kleingeld PA3A < pa3a@... > wrote:
Hi Roger and all,
This one attracted my attention. Thanks for the nice graphs and foto's
Roger. Love your test-jig.
About 4months ago I wrote an article about measuring high impedances
with the nano. Also did one on low impedances.
For the Hi-Z story:
The nano did pretty well on 47 and 470 ohm resistors . 4k7 was worse and
10k was far off. All using *S11 measurement*. I enclosed de S11
measurement on a 10k resistor.
Using a *S21 measurement (series)* gave a very good value voor de high
impedance 10k and that result is also enclosed. It is an Excel graph
where Rs+jXs were derived from the S21 data, and then converted to Rp
and Cp (so series to parallel). Amazing result by the nanoVNA, which is
an old version H3.2 .
I did the same KIND OF thing for low-Z measurement with S21 with
resistor in /parallel /so to speak. I tried 1, 0.5 ,? 0.33 and 0.2 ohm.
Came up with 0.33 ohm accurate measurement. And I did not take any
special precautions. ). The 0.2 was OK on lower frequencies and a bit
off at the high side of HF. That might be my mistake. I do not carry a
lab here and only a junkbox full of old fashioned solderable components.
I'll post the Low-Z results in another message if someone would like to
see it. Not enclosing them now because we don't need any confusion here
:-)
73,
Arie Kleingeld PA3A
