Advanced PI coils

[Mechanic]

This is very quiet and works well in noisy areas. You can crank up the gain too. These coils are light and the differential setup is not too cumbersome to use. However, in quiet EMI areas I take the top coil off.

Eric.

Hi Eric,

I love it! Have you tried with smaller coils for the top coil? Obviously the configuration you have shown is optimal, but even a smaller coil should show significant emi reduction.

I like the way you have mounted it too, very elegant.

Cheers Mick

[6666]

Hi Aziz
thanks for the test on the figure 8 coil
much appreciated
cheers

[Sergey_P]

Ok?

http://www.nemfis.ru/MaloglGF.pdf (57p..)
http://emf.ipgg.nsc.ru/mpg/geoelectr...s/ems/ems5.pdf
...

[Bill512]

Hi Eric,

I love it! Have you tried with smaller coils for the top coil? Obviously the configuration you have shown is optimal, but even a smaller coil should show significant emi reduction.

I like the way you have mounted it too, very elegant.

Cheers Mick

a smaller RX coil attached somewhere on the lower shaft at 30-60cm above the main coil, maybe is better solution. Two identical RX coils at a relative small distance, may have a "differential action" on reception ( possible cancellation on very deep targets).
Not tested, just a guess.

[johnandles]

[ATTACH]22993[/ATTACH]

I would call it the....
Shamisen

[Brian Deese]

I have an idea,forgive me if this has been gone over already.I wound a moodz bifilar Balun coil and I plan to experiment with it. However I like the idea of separate TX and and Rx coils Like Eric posted where the rx is .7 the diam of tx. So the idea is to use the moodz coil as the Rx inside of the Tx. So I was reading on Tinkerers projects and see he is balancing his coil,with a third bucking coil. So I furthered my idea.We take standard mono for tx coil,and use moodz balun coil for the rx. Then we use the unbalanced side of moodz's balun coil tied to the Tx in rev polarity to act as our bucking coil adjusted with series resistance. Does this work? What do you guys think?

[Brian Deese]

Ok so I just read the coil chapter of inside the metal detector,and Carl's Coil basics and it seems to me the moodz coil will be ballanced anyhow,unless there is a problem with twisted pair in that configuration. I'm also in need of education as to the mechanical placement of the coils and the benifit of moving the rx coils out of the same plane as the tx coil. The figure 8 seems to be a favorite,and its coplaner.I dont see how a coplaner concentric with 1/2rx+ and 1/2rx- is any different at all from the figure 8 coil.

[Carl-NC]

Sometimes it's hard to envision a coil question without a drawing or a link to a prior post.

[Brian Deese]

Sometimes it's hard to envision a coil question without a drawing or a link to a prior post.

Ok I'll see if I can draw something up.

[Brian Deese]

Sometimes it's hard to envision a coil question without a drawing or a link to a prior post.

Ok here goes it

[Davor]

IMHO coplanar solution will not get us any further depth-wise with PI or any other technology. It is already clear to me that the only way of reaching any deeper is by means of planar field, or at least less squashed than what we have with mono or coplanar. A 2box does it for IB while also maintaining induction balance, but the key is in a field being applied to the targets with less gradient depth wise than the planar coils provide.
2box are built with large coils to be able to pick deep targets - no wonder they suck at pinpointing. It can be easily remedied.
So top hat is so far the only real competitor in this direction, and my vision is that it can be put on steroids.
I think now I'm ready to pursue some PI as well, but my primary technology will remain IB CW. I know how to reduce the cyclostationary signal so IB CW will perform just as good, but with discrimination.