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Old 26th May 2005, 12:12 PM   #1
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Arrow Anyone major in maths? please correct this

See my calculation here:

L=2.91mH
C=68.2pF + 180pF=248.2pF



L=2.91mH=0.0291H
C=248.2pF=0.0000000002482F

Rs=sqrt(L/C)
Rs=sqrt(0.0291/0.0000000002482)
Rs=sqrt(117244157.937147461)
Rs=10827.9341


Cs=[2*pi*sqrt(LC)]/Rs
Cs=[2*(22/7)*sqrt(0.0291*0.0000000002482)]/10827.9341
Cs=0.000000000156010404798

If 10^-9 = n
Then Cs=1.56nF

So I get
Rs=10k8
Cs=1.56nF


Sorry that I have only O level maths and that was grade B I got many many many years ago!!
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Old 26th May 2005, 12:31 PM   #2
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Default Re: Anyone major in maths? please correct this

Quote:
Originally posted by chris ma
See my calculation here:

L=2.91mH
C=68.2pF + 180pF=248.2pF



L=2.91mH=0.0291H
L=0.00291H -- you missed a zero.
btw, a scientific calculator makes life a lot easier -- and the Texas Instruments version can even talk to your DVM. (I am embarrassed to say that I use an HP41 which is over 20 years old.)

four decades ago when I took physics and calculus we had to do this stuff with a book of logarithms and a slide rule.

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Old 26th May 2005, 12:42 PM   #3
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Default Re: Re: Anyone major in maths? please correct this

Quote:
Originally posted by jackinnj
...I am embarrassed to say that I use an HP41 which is over 20 years old...
You should be proud, not embarassed! Not succumbing to the modern disposable mentality is one step closer to a sustainable existence. Plus old stuff is often the best

I have a not-so-old TI-86 myself, although I never use it anymore, instead preferring to use 'Virtual TI' (a TI calc emulator for Windows), since it is far faster than any real calculator.
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Old 26th May 2005, 08:36 PM   #4
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Default Re: Re: Anyone major in maths? please correct this

Quote:
Originally posted by jackinnj
and the Texas Instruments version can even talk to your DVM. (I am embarrassed to say that I use an HP41 which is over 20 years old.)
Hey... the HP is RPN, i can't use those other silly calculators that aren't... i'd still be using my HP25C if it hadn't gotten left in an ex's glovebox.

My HP is virtual these days (althou i have a rarely used HP (maybe 15 years old) somewhere in the lab -- needs fresh batteries)

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Old 26th May 2005, 09:08 PM   #5
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I told my kids I had to get an RPN calculator as my mom is Polish. I used to program little magnetic tapes -- worked out the tractrix horn formula in RPN.
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Old 26th May 2005, 09:29 PM   #6
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Quote:
Originally posted by jackinnj
-- worked out the tractrix horn formula in RPN.
I think i was using an HP11 when i figured out my 1st tractrix horn... then i did a FORTH program, now i have a Trapeze spreadsheet.

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Old 27th May 2005, 10:44 AM   #7
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Default RPN

I am an RPN addict and simply cannot use anything else than an RPN. And I use my trusty HP32SII because it's awake INSTANTLY when I need it; I do not have to PLEASE WAIT for anything to get it's act together.
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Old 27th May 2005, 12:47 PM   #8
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Default Re: Re: Re: Anyone major in maths? please correct this

Quote:
Originally posted by Mr Evil

You should be proud, not embarassed! Not succumbing to the modern disposable mentality is one step closer to a sustainable existence. Plus old stuff is often the best

I have a not-so-old TI-86 myself, although I never use it anymore, instead preferring to use 'Virtual TI' (a TI calc emulator for Windows), since it is far faster than any real calculator.

I can beat that. 1978 Casio fx-451 scientific calculator with Solar Cell - 27 years of calculation with zero batteries - and I have two of them!

Jan Didden
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