New concentric coil geometry. Will it work?

[dbanner]

Twin buck coils should be easier to balance Rx coil. By just sliding them closer together or further apart. What do you think?

[pito]

Nop, you can balance coils if you remove big Tx coil, with it no balance can be achieved.

[pito]

Second thought, it can be done, for example, a large Tx produces 10V in Rx, so each small one must produce -5V,

[Gwil]

Looks like it would work, but you don't actually need two buck coils. If you have just one buck coil overlapping the Rx coil then you've basically got an adjustable omega layout. (There is a different type of adjustable omega shown in ITMD 2nd Ed, page 136.)
However, having two buck coils might give some advantage, I don't know. Try it?

[kt315]

depth is increased just due a principle - more size more depth. i do not see here more size. look on OO coil and you will see - RX coil is O, TX coil is also O.
and O is more than D, in square, vs DD coil. no secret for you DB.

[pito]

and a differential sensor will come out of it = ground cancellation

[pito]

more size more depth..

or more Tx power
or more sensitive Rx

[kt315]

TX preamplifier in coil adds "1-2 to a depth vs one without it. ML has easily proven that. so the deal is not in a configuration....

[Carl-NC]

Gwil is right, this is basically the same as the Omega/4B type coil:



In practice, the TX coil was folded to produce the reverse bucking loop and the RX coil was moved up/down to achieve balance. But there is no reason why the bucking coil can't be a separate winding.

The partially overlapped bucking coil requires a stronger bucking field to achieve balance, and a stronger bucking field reduces depth. As the bucking coil is slid to be exactly concentric with the RX coil you can achieve balance with a weaker bucking field. This means that a concentric bucking coil will have the least impact on depth. Probably why concentric coils completely displaced Omega coils.

[dbanner]

Patents

[dbanner]

Where is the cancel coil in this arrangement? This search loop has 2 Rx coils.

[dbanner]

In practice, the TX coil was folded to produce the reverse bucking loop and the RX coil was moved up/down to achieve balance. But there is no reason why the bucking coil can't be a separate winding.

The partially overlapped bucking coil requires a stronger bucking field to achieve balance, and a stronger bucking field reduces depth. As the bucking coil is slid to be exactly concentric with the RX coil you can achieve balance with a weaker bucking field. This means that a concentric bucking coil will have the least impact on depth. Probably why concentric coils completely displaced Omega coils.

But wouldn't 2 overlapping buck coils(as proposed above)only require half the strength each to provide the same cancellation required to null the Rx coil as a single buck coil slid over the Rx coil? I don't know. Seems intuitive, yes?

[Carl-NC]

You could connect the 2 RX coils out-of-phase and carefully set their turns to create a nulled signal. I doubt Garrett is doing that because the patents says each coil is fed to a separate preamp. More likely, each RX coil has a bucking coil, just not shown.

[pito]

Where is the cancel coil in this arrangement? This search loop has 2 Rx coils.

= post #3, Rx1 produce +10V and Rx2 produce -10V

[Carl-NC]

But wouldn't 2 overlapping buck coils(as proposed above)only require half the strength each to provide the same cancellation required to null the Rx coil as a single buck coil slid over the Rx coil? I don't know. Seems intuitive, yes?

I don't think so. If adding a second coil were to help, then 4 bucking coils would help even more. You have to take into account the fact that the bucking field wraps around inside the RX coil, resulting in poor cancellation efficiency. This is eliminated by making the bucking coil exactly coaxial with the RX coil. It's an interesting idea and really requires building it to see what happens, but I suspect it will never match a concentric coil.