Coil Q

[1843]

Hi all,

How do we know that what coil Q is suitable for each PI?

High inductance & high resistance => less current & high gain, also high capacitance while low inductance & low resistance => more current & less gain and capacitance.

Thanks in advance,
1843

[JC1]

Good Read

Hi 1843,

George Payne on fixed (preset) vs adjustable GB
and coil design

http://jb-ms.com/Baron/gb.htm



The Transmit and Feedback coils can have the same wire gauge. Here is a very very important point! The end of the Receive wire nearest the Feedback Coil must be connected to ground. In other word it must be connect to the loop shield and to the ground in the circuit. If you don’t do this the completed coil will not operate correctly. The R null component of the coil will be excessive and may overdrive the detector. This has to do with the high capacitive coupling between the Receive and Feedback windings. Connecting the coils as I have outline above will solve the problem.

{that capacitance between the receive and the feedback

causes some other "fun" problems when trying to null

these coils, i.e. you now have capacitive feedback and

magnetic feedback, I recommend more insulation between

these two}

{Thought I would breakout this grounding point so you

guys don't miss it, George thinks it is important, so do I.}

I won't cut and paste the Q stuff but give the whole thing

a read. Litz wire is also good read.

[1843]

Hi JC1,

If I am not wrong this article is about IB coil design...

I want to know:
Is the coil Q important for a PI or not?

Kind regards,
1843

[JC1]

OK

Hi 1843,

Yes Q is important on a PI.

Actually alot of that article is appliciable to PI with

balanced coil design. I already posted the Nexus

stuff, it mentions PI.

[JC1]

...

Hi 1843,

Of course on a PI you do not make a tank circuit with a

capacitor, but just damp with resistor, so Q is not high

and for most of these PI designs you can probably just

take any ol wire and wrap up a coil, and may or may not

notice a bit of difference.

[JC1]

Repost

From this point of view it will be safe to state that the sensitivity of any IB metal detector will depend mostly on the electro-
magnetic properties of the search head loops. The most important of those properties is the Q, quality factor.
This article will not get any further in to the academic aspect of the Q ,but wish to tell that the Q is the main of all factors which
could influence the performance of any search head or single loop.
The Q is of equal importance when PI metal detectors are concerned.

http://www.nexusdetectors.com/Science1.html

http://www.nexusdetectors.com/Science2.html

http://www.nexusdetectors.com/Science3.html

[1843]

Thank you very much!

[Righteous]

Can you read the coil Q with a multimeter and if so how ?
Thanks Righteous

[Max]

Can you read the coil Q with a multimeter and if so how ?
Thanks Righteous

With a multimeter ?

Set multimeter to "Q" ! But first you have to find it!

You can't... with a multimeter... but... I've done on an HP pocket programmable calculator

Use this instead:

Q = wL/R

w = 2*pi*freq
L = inductance of coil at the given freq.
R = internal resistance of coil

And have fun!

Kind regards,
Max

[Max]

Hi JC1,
I've read the "science" pages on the nexus website... uhm... ok Q is the quality factor... yes all true... less losses in the wire... so better energy transfer but but but....

Now one thing is puzzling me... if this is the "secret" (I mean full-resonant coil and maximum Q both sides for TX and RX) how Georgi patented that ?

If he patented that I mean...

I think that all this stuff cannot be patented... cause many other people do it before... am I wrong ?

All electronic course explain that you have maximum e.g. oscillation peaks at highest Q... but then maybe Fisher or some others patented that stuff for making MD coils in 1940 or the like!

Ok ok... maybe patent expired... so Georgi can produce the Nexus without paying fees to Fisher but then... all is about manifacturing ???

The secret is actually about Nexus coils manifacturing ??? I've understud well ???

If so... if someone dismantle one of these coils and understand how to replicate it there isn't any legal safety network ??? I'm shocked.

Of course... I'm not interested in dismantling one... also cause I think that one couldn't gain any good information looking at some broken epoxy and copper... but think if someone do it !

Then how to protect Nexus business ???

Georgi I suggest you make lot of patents like Bruce Candy actually do everyday! Who knows... maybe they could be good one day or another!

Kind regards,
Max

[JC1]

Maybe

If you can read inductance with your multimeter.

And resistance with your multimeter.

You might be able to

calculate it from that.

[Max]

If you can read inductance with your multimeter.

And resistance with your multimeter.

You might be able to

calculate it from that.

Hi,
uhm... his multimeter will read inductance at the multimeter internal frequency... depending of strategy used by meter to give readings of inductance...no good that way...

You know that "real" coils could slightly change inductance with frequency variations... so he have to measure (or calculate) inductance at exact TX operating frequency.

Then he must consider the effect of shields too... that's another important parameter... then he must consider the effect of mineralization making resonance and Q optimization for a medium soil model (few iron minerals)... etc etc etc

If we want split hairs we need at least to find params at operating conditions !

Or not ?

Best regards,
Max

[JC1]

Huh?

Hi JC1,
I've read the "science" pages on the nexus website... uhm... ok Q is the quality factor... yes all true... less losses in the wire... so better energy transfer but but but....

Now one thing is puzzling me... if this is the "secret" (I mean full-resonant coil and maximum Q both sides for TX and RX) how Georgi patented that ?

If he patented that I mean...

I think that all this stuff cannot be patented... cause many other people do it before... am I wrong ?

All electronic course explain that you have maximum e.g. oscillation peaks at highest Q... but then maybe Fisher or some others patented that stuff for making MD coils in 1940 or the like!

Ok ok... maybe patent expired... so Georgi can produce the Nexus without paying fees to Fisher but then... all is about manifacturing ???

The secret is actually about Nexus coils manifacturing ??? I've understud well ???

If so... if someone dismantle one of these coils and understand how to replicate it there isn't any legal safety network ??? I'm shocked.

Of course... I'm not interested in dismantling one... also cause I think that one couldn't gain any good information looking at some broken epoxy and copper... but think if someone do it !

Then how to protect Nexus business ???

Georgi I suggest you make lot of patents like Bruce Candy actually do everyday! Who knows... maybe they could be good one day or another!

Kind regards,
Max

Why are you asking me? I'm not a patent lawyer. Yea just good

engineering, not supposed to be patentable, but maybe just his

country, not all coutries, maybe worded funny. Who knows.

Almost all this "regular" stuff has been done in the past, so have to

read any patents, like some don't patent Q, but special way of

winding special insulated special wire with special glue, that you

can patent and then "beat up" anyone new in court, with money you

already made and he has to fight without much money in new deal.

That's all stuff for lawyers and liars.

Doesn't concern me. Or most of us, we will copy whatever for our use.

So does the Nexus/Georgi have any patents? what is the number?

[JC1]

Not

Hi,
uhm... his multimeter will read inductance at the multimeter internal frequency... depending of strategy used by meter to give readings of inductance...no good that way...

You know that "real" coils could slightly change inductance with frequency variations... so he have to measure (or calculate) inductance at exact TX operating frequency.

Then he must consider the effect of shields too... that's another important parameter... then he must consider the effect of mineralization making resonance and Q optimization for a medium soil model (few iron minerals)... etc etc etc

If we want split hairs we need at least to find params at operating conditions !

Or not ?

Best regards,
Max

Not.

[JC1]

Q meter

http://www.noding.com/la8ak/m1.htm

Now of course anything you do to a coil will change

the Q like when it is over this soil or that soil

so what.

you measure them in the air if you want to compare.