When I was measuring the current with varying frequency of an series RLC circuit, I noticed that the graph produced is asymmetric:

Is there any reason for this? (inductance=8.29mH)enter image description here The Q-factor is 2.75 (3 s.f.)

  • $\begingroup$ Are you asking about asymmetry about the resonant frequency? What was the Q of the system you were measuring? Could you reproduce the graph you obtained? $\endgroup$ – Floris Sep 4 '16 at 3:23
  • $\begingroup$ Thanks for your response! Yes I am asking about the asymmetry. $\endgroup$ – Brian Lin Sep 4 '16 at 3:37
  • $\begingroup$ Can you tell us how you are measuring things? If you are using an AC couples scope it is possible you are running into the low frequency cutoff. $\endgroup$ – Floris Sep 5 '16 at 4:14
  • $\begingroup$ In light of the answer given in the duplicate it would be interesting if you plotted the log frequency curve and confirmed the explanation. $\endgroup$ – Floris Sep 5 '16 at 11:49

Probably stray (parasitic) capacitance or inductance. Inductors also have capacitance, and capacitors have inductance. And resistors have both. So in terms of transfer functions, your circuit probably has poles and zeros at frequencies higher than the primary resonance. This causes energy to spill into the higher frequency band.

Try measuring each component individually on an impedance bridge to test that hypothesis. And if you get measures, try estimating your circuit response with the 'additional' components and build a model to see if it matches your original response.

  • $\begingroup$ Check @ArtBrown 's link above. $\endgroup$ – Farcher Sep 4 '16 at 4:16

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