How to sync CS320A with external signal source for FRA

How to sync CS320A with external signal source for FRA, a forum discussion on Cleverscope Mixed Signal USB Oscilloscopes. Join us for more discussions on How to sync CS320A with external signal source for FRA on our Questions forum.

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davidJiang

12th May
Posts: 3

Hello,

Since i don't have a build-in CS700 or CS701, how to sync my CS320A with external signal generator for frequency response analysis? Any guide-line/documents for reference?



Thanks!
David

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bartschroder

13th May
Posts: 451

Hello David,
Unfortunately the FRA relies on using a tracking generator to do the maths needed to calculate the complex response at a particular frequency. We don't have a way of linking to an external frequency generator to control it's frequency.

You can use Peak Averaging to do a response based on an FRA function that is not frequency dependant (eg RMS, Power, Power Density, Gain/Phase), but frequency dependant functions ( Impedance, Capacitance, Inductance) will not work. Set Settings/Averaging/Weighting Mode to Peak. Determine the frequency step you are going to use in your generator. The dwell time at each frequency should be longer than the time it takes the CS320A to capture and process a spectrum. Start off slow - say 50 ms per step. If the frequency generator sweeps continuosly there will be smearing in the spectral response so make the sweep slow. Make sure the Scope graph time width is at least 1/Frequency Resolution you want to achieve. Capture some signal to make sure the Spectrum Display knows what data is available. Ensure the amplitude range is sufficient to capture your signal. The Frequency resolution should be about twice the frequency step you are using, to minimize window errors.

Open the Spectrum Display, and set the Frequency Resolution to twice your external signal generator frequency step (otherwise you will get inaccuracies in the estimated value). Set the Settings/Spectrum/Transform Type to the function you want. Set the Settings/Spectrum/FFT Window to Flat Top to minimize frequency bin to signal generator frequency offset errors.

Now set your frequency generator to the minimum frequency, start capturing, and click the Avergeing button ON. This will now capture the peak value at every frequency. This will be noisier than we achieve with the FRA, but will give the best estimate. Sweep the frequency. You should now have a response. Stop capturing.

This setup will be limited in frequency range, because you cannot dynamically set the scope graph width or the spectrum parameters, as the FRA does.

Much easier to buy a CS701 signal generator!

Good luck.
davidJiang

13th May
Posts: 3

Hi Bartschroder,

Thank you very much for so detailed reply!


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