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Impedance Curves

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Importing text impedance curves and splicing

In this series we import two text-files with FFT impedance measurements and finally splicing these curves to form a single broadband curve with high resolution at the resonance poles.

Download example files

Select the two files in the file-dialog or drag from File-Manager. Because these files are text-files of unknown format the Import Control Dialog opens.

VACS-Screenshots-Importing MLSSA Impedance - Import Control Dialog

These MLSSA generated files store in their first column the frequency, in the second the amplitude in ohm and in the third column the phase angle in degree.

  MLSSA-Imp-AmplPhase - 24kHz.txt        MLSSA-Imp-AmplPhase - 5kHz.txt

  "Impedance Bode Plot - ohms (eq)"      "Impedance Bode Plot - ohms (eq)"
      "Hz"       "Mag"       "deg"           "Hz"       "Mag"       "deg"
  5.859375,   5.610211,   16.46252       1.220703,   5.492231,   -2.49283
  11.71875,   7.757777,   27.38552       2.441406,   5.625942,   6.395455
  17.57813,   9.982823,   31.87035       3.662109,   5.902278,   12.01649
  ...                                    ...

On import VACS tries to estimate the format and presents these estimations in the above Import Control Dialog. Here, everything looks alright and we can click Apply. VACS should display two impedance curves.

VACS-Screenshots-Importing MLSSA Impedance - OrgCurves

These two measurements are taken from the same device under the same conditions, only that the frequency steps are different. The broad-band (24kHz) file has approx 5Hz resolution, whereas the narrow-band file has approx 1.2Hz resolution. The broad-band data-set misses out the details at the resonance poles, whereas the narrow-band set stops working at 5kHz.

The idea is to splice both curves in order to form a single data-set with high resolution around the resonances and to offer broad-band characteristic as well.

First we need to decide on the cutting-frequency, say f=1kHz, which also would remove some art-fact from the measurement data.

VACS features a Splicing-Processing for curves. Issue menu Processing > Splicing and select the setting so that the narrow band-curve forms the lower part of the resulting curve. Enter "1kHz" as splicing x-axis-value:

VACS-Screenshots-Importing MLSSA Impedance - SplicingDialog

The Splicing Processing creates a new curve, where points below 1kHz are taken from the narrow band curve and above 1kHz points are taken from the broadband curve.

VACS-Screenshots-Importing MLSSA Impedance - SplicingResult