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Calculating the frequency based on LC circuit 
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#1
Mar2313, 11:23 AM

P: 4

Hi all,
I am currently building up a lightning detector based on this website: http://www.techlib.com/electronics/lightningnew.htm as the diagrams shows, the resonance tank included a 10mH inductor and a 10pF capacitor. As I want to calculate the resonant frequency (using the formula f = 1/2pi*sqrt(LC)), the answer was 5Hz, which is far from the desired range (should be around 200kHz) is there any mistake in my calculation or concept? Thanks for your help. Guns 


#2
Mar2313, 12:00 PM

Mentor
P: 11,889

How did you get your answer? Did you consider the SI prefixes (milli, pico)?
I think there are brackets missing in your equation. 


#3
Mar2313, 12:34 PM

P: 4

mfb,
I did it this way: 1/2pi*sqrt(10^(3)*10^(12)) which approxmately equals to 5 Hz. 


#4
Mar2313, 01:02 PM

P: 484

Calculating the frequency based on LC circuit
Following up on mfb's post, you're missing brackets and are using the wrong values for the SI units:
10 mH = 10*10^(3) H 10 pF = 10*10^(12) F 1/(2*pi*sqrt(10*10^(3)*10*10^(12))) Hz = 503.3*10^3 Hz = 503.3 kHz 


#5
Mar2413, 09:30 AM

P: 4

oh my, silly me.
Thanks mfb and milesyoung! 


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