Minelab 8000

[moodz]

Hey Aziz ... the challenge is on. E class amplifier with only 4 components.

power in is 25 ma at 5 volts. Coil current is +/- 450 ma peak with L= 0.5 mh and R=0.5. @32 Khz

Now the big challenge ... if we vary the coil R from 0.1 to 10 ohms the coil current varies by less than 4 %

This means the TX coil is ground invariant ( which it is ).

As the coil "sees" more losses the circuit compensates automagically. ( which means it ____ ___ ______ ) Guess the missing words.

Stick that in your AI.

[Aziz]

Hi Paul,

Hey Aziz ... the challenge is on. E class amplifier with only 4 components.

power in is 25 ma at 5 volts. Coil current is +/- 450 ma peak with L= 0.5 mh and R=0.5. @32 Khz

Now the big challenge ... if we vary the coil R from 0.1 to 10 ohms the coil current varies by less than 4 %

This means the TX coil is ground invariant ( which it is ).

As the coil "sees" more losses the circuit compensates automagically. ( which means it ____ ___ ______ ) Guess the missing words.

Stick that in your AI.

this is very nice!
Class E will provide more voltage to get the current flowing through the "variable" TX coil current due to ground conditions.

"which means it ____ ___ ______"
"which means it will ??? ??????"
"which means it will ??? Minelab"

I don't have any idea. Help me please.

[Aziz]

Hi all,

my comments on following coil configurations according to the figures 1 to 7 of the coil patent.

Figure-1:
Irrelevant. No good. TX is smaller than RX.

Figure-2:
Good and simple. Fully anti-interference possible.

Figure-3:
Good and simple. Same as Figure 2.

Figure-4:
Irrelevant. Too complex.

Figure-5:
Irrelevant. Too complex. Bad. TX is smaller than RX.

Figure-6:
What's this? I didn't read the patent. I'm looking at the figures only. And one table for the figure-7 coil data.

Figure-7:
Irrelevant. No good. TX is smaller than RX.

Figure 2 and 3 are the only options to look at it.

[Carl-NC]

There is no bucking coil. Two anti-phase RX coils (85 and 86).

Bucking can be done either with a TX- coil or an RX- coil, so in this case coil 86 is the bucking coil.

[Aziz]

Bucking can be done either with a TX- coil or an RX- coil, so in this case coil 86 is the bucking coil.

Well, I intended to keep the naming convention to the standard definition of bucking coil. Isn't this for TX side?
The patent is also calling the RX side "bucking" coil the nulling coil.
The naming of nulling coil is more clearly in my opinion.
Therefore my definition of bucking coil is for the TX side only.
Anyway.

BTW, the RX and nulling coil will produce a detection hole zone for particular targets. If the RX coil is small, the nulling coil is large and you have a deep large target, the nulling coil can begin to detect the target signal, whereas the smaller RX coil keeps quiet. So there is a point, where both RX coils will induce same signal strength, which will be subtracted to zero.

[Carl-NC]

"Bucking" means you are injecting an opposite signal to cancel a primary signal. That can be done with either coil. Or even both. You are correct about the cancelation problem.

[moodz]

Hi Paul,



this is very nice!
Class E will provide more voltage to get the current flowing through the "variable" TX coil current due to ground conditions.

"which means it ____ ___ ______"
"which means it will ??? ??????"
"which means it will ??? Minelab"

I don't have any idea. Help me please.

"draws more power" / "draws more current" etc etc as ground loss saps transmit field.

I have not tested it but if you supply a large battery this circuit will maintain tx current upto kilowatts - so it might be useful for cooking or wireless charging or heated dunny seat for those cold mornings.

For air and regular ground the consumption is around 100 mW.

[moodz]

"draws more power" / "draws more current" etc etc as ground loss saps transmit field.

I have not tested it but if you supply a large battery this circuit will maintain tx current upto kilowatts - so it might be useful for cooking or wireless charging

For air and regular ground the consumption is around 100 mW.

Obviously sampling the power draw gives you a ground signal to play with.

[Aziz]

"Bucking" means you are injecting an opposite signal to cancel a primary signal. That can be done with either coil. Or even both. You are correct about the cancelation problem.

Ok thanks for clarification.
My understanding wasn't correct.

[Aziz]

I have looked at some infos about the Z-coils.

The coils aren't really bad. They are for different purposes.
We will understand it more clearly, if we can see some magnetic fields below the coil structure. I should do some coil simulations models. But I don't have enough infos for the coils yet.

[Aziz]

"draws more power" / "draws more current" etc etc as ground loss saps transmit field.

I have not tested it but if you supply a large battery this circuit will maintain tx current upto kilowatts - so it might be useful for cooking or wireless charging or heated dunny seat for those cold mornings.

For air and regular ground the consumption is around 100 mW.

This could be a game changer.

[Aziz]

Figure-7 coil is very likely the Z18 coil. From the patent application, we can reconstruct the dimension and placement of each coils for a coil model simulation. I can even measure the TX wire thickness. What I need is the "donut" height and width. The diameter of the coil is 18 inch.

Who knows the missing parameters of the nice seat?

[moodz]

I have challenged the AI to build a Z space coil designer with "optimiser" button ... and it just works like magic. Just tap in your TX coil parameters and RX parameters and it works out the bucking and Z spacing.

It shows a nice BS / complete integral field map of the magnetic field on the field map tab.

what is interesting is that a simple 3 coil system can achieve nearly 90 db of null at the rx coil but only under certain conditions.

The maths identified that field "uniformness" is very very important if you want to have any hope of nulling using only mechanical means ... that means CNC accurate coil formers and precision machine wound coils on an absolutely rigid former.

There is a PDF of the report generated attached below ... the null is a realistic 32 db.

[Aziz]

I'm now unemployed!

[Aziz]

Hi Paul,

let's design a better coil for real big deep nuggets.

Which can fit and pinpoint in the digged hole better. A large TX coil (1 m diameter or so), which comes into the region of ground loop TX.
At the lower shaft the smaller RX coil. In the upper shaft the RX bucking coil. RX coil approx 6 - 8 inch diameter, which fits into the hole.
Somewhere in the middle of the shaft the large TX coil. So the TX coil is approx. 20-30 cm above the RX coil (or more). With fully anti-interference RX coils.

Aziz