calculating inductance by frequency n capacitance

[zachtheterrible]

Does anyone know of a calculator on the net that will reveal the inductance of my air core coil based upon the capacitance and frequency? It is a simple parralel LC.

the capacitance is 18pf, and the frequency is 90MHZ.

thanx :lol:

 

[Optikon]

Does anyone know of a calculator on the net that will reveal the inductance of my air core coil based upon the capacitance and frequency? It is a simple parralel LC.

the capacitance is 18pf, and the frequency is 90MHZ.

thanx :lol:

why not use the formulas found in the literature? Air core coils are popular. Theoretically, inductance is not a function of frequency nor capacitance. Inductance is strictly a function of the geometries and materials. In the real world, you do get capacitance with any real coil and the parameters do vary as a function of frequency (very high frequency). Why such a strange request?

 

[zachtheterrible]

yea, i guess it is a bit weird.

well, i have the inductance of a coil that i made, it is .08milihenries. @ least that is wut i think. Wen i calculate it though, my calculations are a bit off. i didn't measure the coil correctly, and its too hard to measure it while it is in the circuit because it has a bunch of components around it.

This way would be extremely accurate also :lol:

 

[Juglenaut]

2*PiFL = Inductance

1/(2*PiFC)= Reactance

Most lab books will go into this subject for L networks and Pi and T networks.

Look up on Low and High pass filters.

 

[samcheetah]

2*PiFL = Inductance

1/(2*PiFC)= Reactance

im sorry you are wrong. 2*Pi*f*L is called the inductive reactance and not the Inductance. the inductance is the L. and 1/(2*Pi*f*C) is called the capacitive reactance and not just reactance.

 

[Nigel Goodwin]

It's a simple enough formula:

F=1/(2*Pi*Square Root(L*C))

With F in Hertz, L in Henries, and C in Farads.

 

[zachtheterrible]

thx :lol: . just had to narrow it down

 

[k7elp60]

An other formula that works very well with RF frequencies is:
LC=25330/f^squared.
L is inductance in uH, C is capacitance in pF, f is frequency in Mhz.
therefore LC= 25330/8100, LC=3.127. L=3.127/18, L=0.173 uH
Use it all the time, even works down at the standard AM broadcast band.

 

[Juglenaut]

im sorry you are wrong. 2*Pi*f*L is called the inductive reactance and not the Inductance. the inductance is the L. and 1/(2*Pi*f*C) is called the capacitive reactance and not just reactance.

Inductance is what I originally said. Reactance is what it is an ohmic value and is used as a term place for both inductive and capacitive. Impedance or reactance of a cap, impedance or inductance of a inductor. Caps are basically shorted by a signal frequency and opposed by inductors, using this you can set up impedance networks to vary voltage and current at loads.

The terms used is just that, were as cap reactance> causes the current to lead the voltage, current leads by 90 degrees. Inductive reactance> Current lag the voltage by 90 degrees.

Impedance matching

Square root of Ri*RL-Ri= XL> XL / 2PiF=L where as L is inductor value
RiRL/XL = XC> 1/2PifXC=C where is C is cap value.

Where as Ri = resistance of the input and RL is the resistive load.

 

[samcheetah]

Impedance or reactance of a cap, impedance or inductance of a inductor.

impedance or reactance of a cap ........ yes

impedance or inductance of an inductor ....... no

impedance and inductance is not the same thing. inductance is the L which is an inherent characteristic of the device which depends on the physical construction. but the impedance or more appropriately the inductive reactance is the ohmic value of the inductor which depends on the frequency. you see reactance and inductance are different things. inductance doesnt depend on the frequency but the inductive reactance does depend on the frequency.

 

[spuffock]

L=1/4*pi^2*f^2*C
C=1/4*pi^2*f^2*L
f=1/2*pi*(L*C)^.5
I make your coil 0.1737uH

 

[zachtheterrible]

L=1/4*pi^2*f^2*C
C=1/4*pi^2*f^2*L
f=1/2*pi*(L*C)^.5
I make your coil 0.1737uH

thanx spuffoc, that is EXACTLY what i was looking for :lol: . i was away for a little wile and just got to look again @ this post.