Ideas to tinker

[Orbit]

The concentric coil I have I don't how it's made its for the SD/GPX series which I just obtained but intend to put into some good work.
Never liked the GB method (target hole) of the TDI.
I think they tried to advertise it like a "discrimination" feature (*some dealers/or just users which aren't aware of how this turns out to work)
but anyway it's what it is - a drawback. I guess you're right it's hard to beat the game and come winning every-time.
Cheers!

Sometimes you should be satisfied what we have! Minelab and Whites have invested a lot and in the end it all comes down to something similar! Better a sparrow in the hand than a dove on a branch!

[eclipse]

Well speaking of Whites I will slightly disagree.
PI wise what they did is obtain already working circuit (Eric's foster GS5) and put it for sale. After few models later they've slapped a MCU which basically is a timing generator and nothing more advanced (TDI SL). Un-released models in-lab beta circuits I'm not speaking.
Minelab is somewhat more advanced because I give them credit they've actually invented something and put it for sale 20+ years ago and probably still using it today for their latest models in some form.

[Tinkerer]

The Minelab GPZ 7000 is definitely not a traditional PI.

[eclipse]

Well it has to be if you look at the price.

[waltr]

You keep mentioning GB. Don't you like the "Eric Foster Ground Balance Method". Why? Because of the target hole?
Yes, there are other methods to do GB, but like everything, nothing is perfect. It always ends up with a compromise between desired features and undesired features.

The concentric coil I have I don't how it's made its for the SD/GPX series which I just obtained but intend to put into some good work.
Never liked the GB method (target hole) of the TDI.
I think they tried to advertise it like a "discrimination" feature (*some dealers/or just users which aren't aware of how this turns out to work)
but anyway it's what it is - a drawback. I guess you're right it's hard to beat the game and come winning every-time.
Cheers!

I use a variation of the "Eric Foster Ground Balance Method" using three samples and it does work very well.
The 'hole' tends to be very narrow in mid-conductors so haven't consider it an issue.
On my HH2 the hole tends to fall on only a certain size rusty nail (one about 1-2cm long). Never found it good for disc'ing out iron but handy to determine a high verse a low conductor target.

[Tinkerer]

Magnetic field simulation

I came across an old simulation I did years ago. It shows the magnetic field and how it interacts with a copper target andwith an iron target. Left side target is copper.
Right side target is iron in 2 different position.
Note how the iron target pulls the magnetic field lines into the target.