Phil and John,
The NanoVNA is an excellent tool for measuring the inductance and capacitance of components. The S11 shunt method using CH0 (port 1) works well for most measurements. In order to get accurate measurements you need to use the following:
Proper test jig
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- This has been discussed many times in this group and what you use depends on the type of components you want to measure and the accuracy you require. There are jig designs with photos in past group posts for SMD, leaded components and larger coils. The higher in frequency you want to measure the more critical the jig. For HF banana clips on the end of coax will give decent results if you calibrate using a non-inductive 50 ohm resistor.
Calibration
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Calibration must be done on the test jig itself at the point where you are going to measure the component. You will need to do a Short-Open-Load (SOL). Set the Stimulus frequencies for the appropriate range and remember to do a Reset before starting the calibration procedure. Verify once it is done by measuring the short, open and load and observing on the Smith Chart trace. The Short should have a dot at the far left on the horizontal axis, the 50 ohm load a dot in the middle and the open on the far right on the horizontal axis.
Measurement
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You can observe L and C on the Smith Chart by going into the trace menu and selecting R+L/C and moving the marker along using the jog wheel. On later versions of DiSlord firmware you can set any S11 trace to Serial C or Serial L to for a graph. I prefer to use NanoVNA app on my PC but others like NanoVNA Saver.
Things to be aware of
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In the real world there are no ideal inductors or capacitors. A physical inductor will have resistance and stray capacitance and a capacitor will have lead inductance, series and parallel resistance. The NanoVNA and the PC programs do a simple calculation of L and C based on the reactance measured. The calculation of L = Xl/(2*pi*freq) and C = 2*pi*C*freq are not the true values and are referred to in the technical literature as apparent inductance or capacitance.
When measuring capacitors keep the lead lengths short or lead inductance will affect your measurements. Keep inductors away from conductive or magnetic surfaces.
When measuring inductors that use a ferrite core one needs to be aware that the inductance will change considerably with frequency. This is because the permeability of the core material changes with frequency and it is different for each "mix". A decrease in inductance is what occurs but stray capacitance will also have an opposite effect on the "apparent" inductance that is measured.
When measuring capacitors it may not be possible to accurately measure them below or above some frequency range using the S11 shunt method because the reactance may be too high or too low. For example a 1 uF ceramic capacitor will have less than 2 ohm of reactance at 100 kHz.
Experiment
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Users should verify that their jig, calibration and frequency range are suitable by measuring some known components. Air wound inductors that are not tightly wound (low self capacitance) are good for initial tests. 10 to 100 pF caps also yield good results across HF frequencies.
Roger Need