DD-Flatcoil for IB/TR (and PI )

[cyclops]

I would like to ask the coil specialists if it would make a sense constructing a DD-flatcoil (pancake-coil) for IB/TR (and maybe PI) detectors.

Reason (my reflection): Making a larger coil (giving more search area and depth penetration) and getting more sensibility to small items as well.

Shielding: Graphite spray or a copper based spray

If it could make a sense, which would be the formulas applicable?

HH & kind regards,

Cyclops

[Kev]

Works good on my PI

Hi Cyclops,
Flat wound is very good for minimal coupling, and great sensitivity.
As expected I found I needed a couple more turns to equal the inductance of a bundle wound coil.

Cheers
Kev.
http://www.findmall.com/cgi-bin/foru...y.pl?read=8378

[cyclops]

TNX for the link!!!

Hi Kev,
Thank you for the link.
At least I know now that it is worth trying a little bit.
Good to know that one needs some more turns.
I did the inverse, with fewer turns and did not get any result on my IB300, that's why I posted the question.
I will try with more turns now and post later when I have the next results.

BTW, how did you adjust the coils? With a loose single turn that has been fixed later or have you found an other way? Which one?
TNX again and HH,
Cyclops

[Kev]

Tuning

Hi Cyclops,
Because I made these for a PI there wasn't as much precision required, such as with a IB/VLF/TR type detector. I was looking to minimise the response from certain hot rocks in a given area so I adjusted the overlap to give the best response to small gold and least to the rock samples.

Obviously there was a bit of a compromise, at the final point there was a slightly reduced resopnse to very small gold and conversely a little more from the rocks. I could have nulled the rocks completely at the exclusion of small gold.

A bit long winded sorry. If you do a search on the PI Technology forum for balancing DD coils you should come across one Eric posted a while back, that used a 1khz oscillator and scope to find the point of least mutual inductance.

Cheers
Kev.