Inductances etc..

[ivconic]

Ahahahahah! Dear friend! I know that! I know how is "made" as manufactured!
I reffered "how is made" to how is projected, calculated, planned!
Anyway thanks!

[Mustafa]

I always wanted to know how is made at major manufacturers.

Hi ivconic,
Watch this video http://www.garrett.com/media/how_its..._its_made.html

Garrett Metal Detectors featured on
"How It's Made" episode on Science Channel

[ivconic]

I always wanted to know how is made at major manufacturers. Nobody so far exlained that here, on these forums. How come?
Ok...i do not ask for delicate details, but would be good to see generally how is done.

[WM6]

Otherwise i know my deal; trial&error and lot of trivial things to do!

You are experienced developer, but coils are neverending story and lifelong challenge for all of us.

Coils do not allow free simplification. I am sure you knov by experience that calculating 1 turn inductance from 10 turns are not valid by simple multiplication 1 turn inductance for 100 turns. Here is catch which required huge lab test to overcome (formulas) simplification to usable reality (and at the end new simplified formulas).

[WM6]

"Mutual coupling" is the right term here! WM6 you are right there.
So... how to calculate Cancel coil ( connected in serie with TX coil and wounded over RX coil ) for this setup and at the same time to maintain 6mH inductance of TX coil keeping im mind "Mutual coupling" effect between TX coil and Cancel coil.

I think there not only question of simple inductance formula. Probably lab started from TX stage and defined here all: best circuit and adequate TX coil. Then they define RX stage: best RX circuit and adequate RX coil. Next step is coupling both stage (coils) togheter and reverse corrections of previous step. I think there is no primary formula and calculate question, but question of hard lab work (sistematic lab test and measurements). From results they can calculate simplified aplicative formulas for future needs and use.

[ivconic]

All can be calculated by given data. You havent data for mutual coupling level of magnetic fields of both inductor. Maximal coupling level we can find by tighten turns on one coil where inductance is not linear depended on Nr. of turns. By two coupling coils you change many parameters at same time not only coupling level, but inductance of both coils, parasitic capacitance, Q, Z, resonance... And all this by only small movement. By changing position everything given data changes in the unknowns. But you want to calculate from unknown data? Like labs do.

How labs do such things? All can be reversed, formula too. Labs do first some targeted and sistematic tests and measurement (see table in my first post) then do some calculations and simplified aplicative formulas.

But you do not have patience to do sistematic tests and measurement. Do you?

I do have patience for this things. Besides...it is winter time, i have plenty of time to do such things.
Problem is that i dont have lab!
Was thinking to hear other opinions here, might be some help from those.
Otherwise i know my deal; trial&error and lot of trivial things to do!

Like i said: it is not my goal to make one cc coil for this particular TGSL. Real goal would be to learn and fully understand principles! Right thing!

[WM6]

But i presume there must be the known method to calculate exact needed inductions as for given setup.

All can be calculated by given data. You havent data for mutual coupling level of magnetic fields of both inductor. Maximal coupling level we can find by tighten turns on one coil where inductance is not linear depended on Nr. of turns. By two coupling coils you change many parameters at same time not only coupling level, but inductance of both coils, parasitic capacitance, Q, Z, resonance... And all this by only small movement. By changing position everything given data changes in the unknowns. But you want to calculate from unknown data? Like labs do.

How labs do such things? All can be reversed, formula too. Labs do first some targeted and sistematic tests and measurement (see table in my first post) then do some calculations and simplified aplicative formulas.

But you do not have patience to do sistematic tests and measurement. Do you?

[ivconic]

"Mutual coupling" is the right term here! WM6 you are right there.
So... how to calculate Cancel coil ( connected in serie with TX coil and wounded over RX coil ) for this setup and at the same time to maintain 6mH inductance of TX coil keeping im mind "Mutual coupling" effect between TX coil and Cancel coil.

[ivconic]

Here is the photo of mentioned setup...

[ivconic]

Not only of polarities but depend on level of mutual coupling of magnetic fields between individual inductors. (I added some obout serial inductance in my previous post).

Problem is that this level of mutual coupling of magnetic fields between individual inductor is hard to define or set (not like tighten turns).

Simple formula
Ltotal= L1+L2+ ...Ln is valid only for non mutual coupled (by magnetic field) serial inductor. On other site number of mutual coupling levels (by magnetic field) can be countless. So there is no easy calculation for such hard to define configuration.

Tell me something about it!
That's why i started this thread after all.
But i presume there must be the known method to calculate exact needed inductions as for given setup.
How they calculated it at the first place? At White's, Fisher, Minelab, Garrett...??
For example i would take any concentric White's or Fisher coil...
How to calculate Cancel coil for some White's (or Fisher) concentric coil?

[ivconic]

I tried to draw the situation. Former used here is taken from scraped Garrett GTI coil. Looks something like this.. ( Showing "Mutual coupling" effect between 2 coils on setup)

[WM6]

How to calculate (predict) that third inductance? Even more complex; those 2 inductances in serie will give different third inductance depending on polarities. Is there any calculation for serial cuopling inductances?

Not only of polarities but depend on level of mutual coupling of magnetic fields between individual inductors. (I added some obout serial inductance in my previous post).

Problem is that this level of mutual coupling of magnetic fields between individual inductor is hard to define or set (not like tighten turns).

Simple formula
Ltotal= L1+L2+ ...Ln is valid only for non mutual coupled (by magnetic field) serial inductor. On other site number of mutual coupling levels (by magnetic field) can be countless. So there is no easy calculation for such hard to define configuration.

[ivconic]

"...There is no simple (+-) linearity between turns and inductance..."

Yes it is fact.
But here problem is even more complex. 2 coils with certain inductances, put togather in space with some relative relation to each other, and connected in serie are giving third inductance. How to calculate (predict) that third inductance? Even more complex; those 2 inductances in serie will give different third inductance depending on polarities. Are coils placed with windings in same direction or those are placed in oposite direction - not the same result at the end.
Is there any calculation for serial cuopling inductances? Serial coupling where coils are wounded in same direction and serial coupling where coils are wounded in oposite direction...

[WM6]

*Connected in serie in same direction (end of TX to start of RX) those are giving 16.5mH.
*Connected in serie in oposite direction (end of TX to end of RX) those are giving 8.7mH.

See?

Those results from inductivity formula in which we have product of two squares:

d2 x n2
------------- = L(uH)
18d + 40l

where:

L = inductance in micro henrys
d = coil diameter in inches (from wire center to wire center)
l = coil length in inches ( 1 inches = 25.4 mm)
n = number of turns

in practical calculation used from page:
http://www.hamradioindia.com/HRI-Calc/AIRCoils.html

we get results:

Number of turns - Inductance (nH):
3 - 77
4 - 122
5 - 177
6 - 240
7 - 306
8 - 379
9 - 470
10 - 582
11 - 644
12 - 656
13 - 745
14 - 789

So we can stated by 3 turns inductance of 77nH, but by 6 turns we do not get double as much (154nH) but about triple as much 240nH and so on. There is no simple (+-) linearity between turns and inductance.

Therefore is not a simple linear interpretation of the successive joining of two coils with a variable polarization.

So this (lower) formula can be interpreted (according wiki)



that these simple relationships hold true only when there is no mutual coupling of magnetic fields between individual inductors.

Maybe Aziz can simulate this problem and represent results graphically.

[ivconic]

Or focus just on this:

Same former/holder with two circles (channels), one 21cm and another 15cm.
Ok.
On 21cm there is 6mH coil and on 15cm ther is 6.5mH coil.
*Connected in serie in same direction (end of TX to start of RX) those are giving 16.5mH.
*Connected in serie in oposite direction (end of TX to end of RX) those are giving 8.7mH.

See?