Coil Q

[1843]

Thank you very much!

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

...

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.

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.

[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

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 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