Few turns Inductor/Coil

[halee awan]

A basic Q:

I've two Coils(air core) that have only 3 turns of copper wire 27AWG.
I'll use them later in my cct
but first i wanna perform a basic test on it
I want to see the flux liinkage or induction effect of one coil to other one at different frequencies .
But i am scared that if i connect it directly to the F.Genrator's output it might damage the F.Generator .due to very low R (Short cct )and impedance mismatching etc ...
If i introduce A known value of R in series what will happen
Wheather it wil effect the actual theam (induced emf)or not?
or what should i do any usefull suggession will be highly appericiated

 

[WimRFP]

You can insert a series resistor without problem. Based on the voltage (amplitude and phase) at the resistor and the resistor inductor node, you can calculate current and voltage through the inductor, hence the real and inductive component.

You may know: L(shorted secondary)/L(open secondary) = 1-k^2.

As long as the wire lengh < 0.1 lambda, I would not expect large change in coupling factor with changing frequency (assuming that both coils are close together of course) .

 

[andre_luis]

You could perform multiple turns in order to take a more accurate result.
That´s because after divide measured inditance, the K^2 factor, also divide the measured error.


+++

 

[WimRFP]

@andre_teprom: Are you sure changing the number of turns doesn't change k in case of an air inductor? In my opinion, depending on the geometry of the coupled inductors, k may change when changing number of turns.

Maybe he can give us more info on the inductors and the frequency of interrest.

 

[andre_luis]

You are right.
I did´t attempted to the fact he is winding around air core.


+++

 

[halee awan]

Thanks to you all for sharing your usefull views tip and suggessions
I'll do the experimnet accordingly then will get back to you with the results we will discuss it in detail

- - - Updated - - -

Thanks to you all for sharing your usefull views tip and suggessions
I'll do the experimnet accordingly then will get back to you with the results we will discuss it in detail

 

[D.A.(Tony)Stewart]

Consider your generator is 50Ω source and your scope can read 10mV/div on 1:1 probe
Consider what load is normally on your filter and apply it.
Then choose a signal for say 100mW reflected back into the generator ( very safe)
That means V=√(.1*50)≈2.2V which gives you a sensitivity range or 2200/10 or 220:1 ratio.
You ought to be able to measure coupling attenuation and resonant frequency easily.
In addition to λ coupling factors, there will be coupling increased due to Q from self resonant frequency as well as orientation in parallel vs orthogonal.

Remember both coils have to be loaded with intended application load.

Bonus points.
I used to use H sweep ramp out of back of scope feed into Vertical and adjust gain and offset then get Vertical Channel out of scope and feed into FM input of sweep generator and then use the probe for the 2nd vertical channel with trigger selecting the 1st channel now you have a linear frequency plot on the scope.

You can also put your probe directly into a Spectrum analyzer and sync SA to Generator to make a Network Analyzer and get Bode plot on screen or use NA if you have one.