Crystal measurement function

[EB4APL]

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[EB4APL]

Crystal measurement can be done with the current versions, but an automated function to directly obtain the motional parameters of a crystal or a set of them could be of interest. I am used to do it with a Scalar Network Analyzer (PHSNA) which have this function and I have done some tests to automate and speed up the procedure. While I have collaborated in the later versions of PHSNA I am not a programmer and I don't know Phyton, but if any author likes the idea of implementing this functionality, please contact with me at [email protected] and I will supply him the methodology and the formulas.

[stdevPavelmc]

Hi Igancio.

This is a interesting feature, can you provide me the methodology and the formulas to try to implement this feature into the software?

BTW: Soy cubano y podemos intercambiar en español internamente (I'm cuban and we can speak in spanish directly)

Please review your mail.

[open-tommie]

Hi,

2021/02/06 1:48、Pavel Milanes (CO7WT) Hi Igancio.

This is a interesting feature, can you provide me the methodology and the formulas to try to implement this feature into the software?

I hope this video helps you.

Measuring Crystals with NanoVNA and other tools https://youtu.be/G9zZRNzhsEE

I want to measure crystals with NanoVNA-Saver.

From Tokyo, Japan.

[stdevPavelmc]

Thanks @open-tommie, very instructive!

@EB4APL please review the video and my notes below and comment, please...

Notes for later (may contain bugs)

• C0: Measured way below the original freq to remove the crystal, let's say 1Mhz below, then run a couple of sweeps to get a mean of that value. (Crystal in parallel to ch0, ch1 not used)
• Setup a fix to put the crystal in series with the signal of the NanoVNA (try to keep the 50 Ohms path matched!)
• Find the series and parallel resonance, set the centre of the span in the middle point of both Fs & Fp
• Set a span that allows to view the entire slope of the curve with a safe margin (typical 50-150 kHz, this curve/settings can be used for later)
• Rm: Set a narrow span ~10khz around the series resonance frequency to determine Fs precisely
• Record S21 to find it
  • Fs that is at S21 at 0 degrees phase (also at minimum s21 value)
• Compute Rm per the video/paper formulas
• G3UUR Oscillator method can't be done with the NanoVNA, or can we?
  • Reading the input and finding the peak at ch1, instructing the user to switch from trough the cap to directly to ground connection on the oscillator?
  • Level issues for DR at the input of the NanoVNA?
  • User formulas from the video/article
• Phase shift method is easier
  • Use the 10k max resolution centred over Fs (Record Fs)
  • Record S21 on Log Mag & Phase
  • Find Fl and Fh at +/- 45 degrees phase shift around Fs
  • Use formulas from video/article to calc Cm & Lm
• 3dB method is similar to Phase shift method, which give us better results?
• Series/Parallel method
  • Use the settings of the full view of the entire entire slope
  • Find rough Fs/Fp, make a closer 10kHz scan to take them precisely
  • Use the formulas and previous C0 values to calculate the values.

Some random thoughts:

• G3UUR is discarded as need an extra oscillator
• Use1/2 of F to check for the holder capacitance, or use a initial 1Mhz span and use the lower freq for that (as the NanoVNA must be calibrated at that frequency)
• 3dB & phase shift method can be carried out with a simple external fixture
• What method must we use, phase shift?
• This can be implemented easily after some effort.

Please review my notes and do comment on them... I will came up with a proposed algorithm for the users point of view for posting later on this weekend.

Cheers

[vadim-dem]

XQ_S11_Lm_calc_05.zip You can try also circle fitting into G/B plot, the attachment is Scilab script with .S2P file example:

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