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Inductor Coil Testing

Discussion in 'Radio and Wireless' started by Rajinder, Dec 29, 2020.

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  1. Rajinder


    Jan 30, 2016
    Hi all,
    I have a transponder coil 7..2mH and 125KHz resonant freq. The transponder has been tested with a LCR bridge meter.

    I need to design a circuit to test that is fr is at 125KHz.
    How can I do this? Would I need a LC parallel circuit and feed with freq generator at 125KHz?
    Any help would be aporeciated.
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    A coil alone does not have a useable resonant frequency. For resonance you need an LC circuit (and considering that each inductive coil also has a small capacitive component there is indeed a resonant frequency but it is not well defined).
    The resonant frequency of an LC circuit is easily calculated from the component values. There are several methods to verify or determine the resonant frequency of a circuit. See e.g. here.

    You should learn how to use Google or another search engine. The information you request is widely published.
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    A coil's resonant frequency is where the reactance due to inductance is matched by the capacitance between the windings. it is the point at which it effectively becomes more capacitive than inductive with increasing frequency.

    You shouldn't plan to use any inductor near it's self resonant frequency.

    It's possible that this isn't the self-resonant frequency, in which case, see Harald's comment above.
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