AMX coils

[moodz]

I still need a parts list

I would wait a while and read up more on the AMX thread.

AFAIK no-one has even built one AMX yet .... its still being developed.
Unless you are skilled enough in electronics and design you will have to wait till AMX release version.

[lxs17757414132]

Thank you very much, Master Moodz. I have also seen your work on the forum, which is very excellent

[moodz]

Thank you very much, Master Moodz. I have also seen your work on the forum, which is very excellent

Thanks .. the AMX guys will get there eventually. Tinkerer is persistent and the board he has made looks good for hobbyists ... ( ie not too small ).

[Tinkerer]

So, here we are again for a concentric 18" coil for the AMX.
The AMX is an "open-source" project. All information is available to everybody who wants to build it.

Nova wants it to go deeper than the DS2200d.
So far, we have no other wishes.

Wishes please!

We will have to make some compromises:
Ergonomics
If it needs to be solid, it will have a considerable weight. How much? We need to discuss the options in the design stage.

Power
We want to beat the SD2200d for depth, power consumption and sensitivity. The coil design is an important part. Suggestions how we could achieve that?

Shape
It is to be a round coil without openings. For nugget hunting one tends to drag the coil on the ground or very close to the ground. Vegetation, roots, rocks tend to snag in the openings of the coil.

Color
Whitish, dark colors can get very warm in the sun. The temperature changes induce drift that we want to avoid.

What else? Now is the time to make suggestions or clarify questions.

[Carl-NC]

IMO, I would look at the trade-offs in topologies first. This can be done with a smaller, more manageable coil, say 10-12". Namely, look at the difference between mono coils and concentrics, which can be IB or not. On the mono, vary N to see what produces the best depth with acceptable settling. On the concentric, use an optimal TX and vary the RX in both diameter and N to see what gives the best sensitivity to particular target sizes. All of this can be done on the bench without concern for a housing or even shielding; it's all an exercise in magnetics. Whatever answers are found can be scaled up to a bigger coil.

[Tinkerer]

IMO, I would look at the trade-offs in topologies first. This can be done with a smaller, more manageable coil, say 10-12". Namely, look at the difference between mono coils and concentrics, which can be IB or not. On the mono, vary N to see what produces the best depth with acceptable settling. On the concentric, use an optimal TX and vary the RX in both diameter and N to see what gives the best sensitivity to particular target sizes. All of this can be done on the bench without concern for a housing or even shielding; it's all an exercise in magnetics. Whatever answers are found can be scaled up to a bigger coil.

Good idea,
I will start with a 300mm diameter mono coil. Can we consider the attached simulation as a reasonable representation of a Minelab SD2000 TX?

[moodz]

This thread is becoming confusing ... first there is talk of a bipolar pulsing "AMX" solution .. Now there is talk of the SD2000 which is monopolar pulsing and not AMX technology.

The AMX comparable GPZ7000 punches much deeper than an SD2000 .. mainly because the GPZ is an evolutionary stage better than the SD.
I know becuase I have dug the holes.

[Tinkerer]

This thread is becoming confusing ... first there is talk of a bipolar pulsing "AMX" solution .. Now there is talk of the SD2000 which is monopolar pulsing and not AMX technology.

The AMX comparable GPZ7000 punches much deeper than an SD2000 .. mainly because the GPZ is an evolutionary stage better than the SD.
I know becuase I have dug the holes.

I fully agree with you.

Few people understand the bi-polar pulsing.
This is why I try to show the advantages of the bi-polar pulsing, compared to the mono polar pulsing of a traditional PI.
I try to show the target response of same Amperes, at the same field strength.

[Carl-NC]

I guess I don't understand how the SD2000 relates... it's not a comparison of the TX current or even the field strength, it has to be a comparison of overall sensitivity to a particular target.

[Tinkerer]

I guess I don't understand how the SD2000 relates... it's not a comparison of the TX current or even the field strength, it has to be a comparison of overall sensitivity to a particular target.

Do you have a better suited simulation we could use for comparison?

[Carl-NC]

I don't know what you're trying to compare. If it's sensitivity of the SD2000 vs the AMX I don't know how you can do that in a simulation. You need to wave a target, which means having a reasonably working AMX. A better comparison for now might be the SD2000 vs the GPZ7000.

[Tinkerer]

I don't know what you're trying to compare. If it's sensitivity of the SD2000 vs the AMX I don't know how you can do that in a simulation. You need to wave a target, which means having a reasonably working AMX. A better comparison for now might be the SD2000 vs the GPZ7000.

The SD2000 represents a traditional PI
The GPZ7000 represents a CCPI

Maybe I should explain the difference between the function of the TX of a traditional unnamed PI and an unnamed CCPI?
The difference between 2,000 pulses per second and 20,000 pulsed per second.
The difference between monopolar pulses and bipolar pulsed for handling the Earth Magnetic Field.
What happens inside the target with Traditional PI pulsing.
What happens inside the target with CCPI pulsing.
The difference of the target Eddy currents of the traditional PI and the CCPI.
Target TC's 1us, 5us, 20us, 200us.
The difference of a TX coil of 30cm diameter with 20 turns or 100 turns. How does it affect the targets with a TC of 1us, 5us, 20us, 200us.
The difference of the induced Eddy currents in the targets from a 20 turn coil or a 100 turn coil with the same 50KHz TX pulse.

These are a few of the things I wanted to explain here. If somebody is interested.
I am thankful for any suggestions I can get, to make my explanations easier to understand and help in clarifying the points.

[Carl-NC]

Now I'm more confused over what the goals are. If it is to optimize the coil design for depth, then things like the pulse rate and bipolar-vs-monopolar don't really matter. They do matter if the goal is simply to get more depth (what Nova wants) but they are generally independent of the coil design. That is, regardless of the coil design, a higher pulse rate will always help, and bipolar will always help get you a higher pulse rate.

Some of the other stuff is relevant in varying ways. How eddy currents behave can be important in determining the highest useful slew rate and (by extension) the minimum useful sample delay. IMO, start with the assumption of CCPI and start with the assumption of a medium-high target TC. I would then start with a mono coil and with a fixed diameter (again, it doesn't really matter, the physics are the same) and determine what topology, wire type, gauge, N, etc produces the best target depth. Then move on to concentric.

First thing to nail down is the TX driver because what works well for CCPI is probably very different than for a monopolar driver. That's the biggest apples-vs-oranges issue; you cannot directly compare the two.