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Old 19th Feb 2009, 10:29 pm   #11
Skywave
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Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
Lightbulb Re: Measuring Resonant Frequency

Here's the germ of an idea that you might like to investigate to develop your work into a useful piece of test gear.

You have an approximate idea (at least) of the variable capacitor's max. capacity. From this, estimate the mid. value of its capacitance. Now replace the var. cap. (at this setting) with a fixed value cap. of close tolerance and re-measure the resonant freq. (Should be very near to that found previously). Since you now know (a) this freq. and (b) the cap. value, you can calculate the value of the inductor. Now replace the fixed cap. with the variable C. By selecting various freqs. and adjusting the variable cap. for resonance, you can calculate the capacitance of the capacitor for any particular angular setting of this capacitor (since you know the inductance of the coil). Thus, you have calibrated the variable capacitor.

Pop the var. cap. into a box with a scale showing the capacity at various angular settings. With the same test set-up (sig. gen. & 'scope) you can measure, by calculation, the inductance values of a range of coils - always a useful facility.

Al / Skywave.

Last edited by Skywave; 19th Feb 2009 at 10:32 pm. Reason: Find huge amount of blank space at end of text! Deleted it
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