Square DD coil

[green]

I am trying to build a PI detector. I've been playing with a square DD coil, 4.5 x 4.5 inches. I started small to save wire while playing. I thought square might be easier to build. I'm including a graph. My questions are. Does the graph make sense? Would a round DD coil be more sensitive? Would some other shape be better? Would making the coil 10 or 15 inches change the answers?

[bernte_one]

the voltage that is generated in the rx coil depends on the inductivity and the resistance of the coil, the target feedback (big- small, deep-low) and the power which comes from the tx

so the graphic should make a sense

[Carl-NC]

Generally round works best in terms of inductive coupling efficiency. Build 2 identical round mono coils, then shape one into a square and do air depth comparisons.

Round is also least susceptible to ground lift-off effects. That is, a OO coil (as used by Nexus) is best, a 00 coil (such as an SEF coil) is next best, and a DD coil is next to last. Only a double-square coil would be worse than a DD. A tight corner radius produces a field non-uniformity that creates lift-off.

[Aziz]

Hi all,

one can use the "rounded" corners rectangular coil. *LOL*
Wait wait!, the "rounded" corners being patented by Apple (iPhone). *LOL*

The rounded corner rectangular coil comes close to the round coil. But you have a combination of a small and large "round" coil.
Wait, an elliptical coil can be considered to be a "rounded corner" rectangular coil as well. *LOL*

Cheers,
Aziz

[Funfinder]

> Wait wait!, the "rounded" corners being patented by Apple (iPhone). *LOL*

No way, the rounded corners have been patented by rivers which polished the rocks corners round.


Seen from a practical point of view the eliptical DD is the best shape.

Technically seen its like a ground scanning rod - with one sweep and a good DD coil its possible to scan with the complete coils lenght 30cm deep for coins -
at its center region up to 40cm or more.

45cm coil size x 3m sweep = ca. 1,5 square-meter searched ground per sweep (per second).

Seen from the weight and that the front side of the coil better can penetrate bushes or handle ground with all kind of vegetables or stones
the eliptical DD also is the best solution.

btw there also is an upside down DD variante possible - using 2 almost round coils where just the upper and lower end is slightly more shaped like a tip.
(2 egg shaped coils) But because while sweeping the overlapping DD area is horizontally, the scan area is pretty small compared with the usual eliptical DD configuration.