[time-nuts] Frequency of LC Tank.

J. Forster jfor at quikus.com
Fri Apr 11 18:41:15 EDT 2014


That's why you want to look for the phase of the tank impedance. The phase
goes through zero at resonance. It is far more precise. The steepness of
the phase v. frequency plot is steep w/ a high Q circuit...  flatter w/ a
low Q tank. Either way, it does go through zero at resonance.

The phase v. freq looks kinda like this:

Phase:
              /\
-------------/  \  /---------------    Freq
                 \/

                ^ resonance



The dither sweep, amplituse measurement, lock-in will tune the oscillator
to maximize the amplituse.

Either on should pretty much steer you to resonance.

-John

==================




>
>> I have a large LC tank, with a very lossy inductor. ...
>
>> So the question is, when actively driving a tank circuit, how do you
>> know
>> you are driving it with the same frequency ad the same phase it
>> naturally
>> oscillates at.
>
> If it's lossy, the peak will be broad so tuning the driving frequency
> won't
> be critical.
>
> How about just measuring the amplitude and tune for a max?  I'm thinking
> of
> something like a diode and R/C filter feeding an ADC.
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
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