Ground balance compensation coil

[Ivont]

Give me some document.

[moodz]

A good summary of ground related stuff in this short paper ... but there are some very good pointers in there.

https://abl.gtu.edu.tr/dosya/102/~sa...0BALANCING.pdf

[Ivont]

A good summary of ground related stuff in this short paper ... but there are some very good pointers in there.

https://abl.gtu.edu.tr/dosya/102/~sa...0BALANCING.pdf

Thank you moodz for the document. I will read it and make sense of it. It seems quite useful.
Some time ago, I had done a project on the principle I had indicated above, but it turned out to be a waste of time. Nothing worked. That's why I asked here if anyone had tested it. I received signals that did not cover anything from the earth effect.

[Ivont]

Here is a solution that I'm not sure is correct.

[pito]

make both Rx coils the same inductance and balance them using potentiometer

[Ivont]

make both Rx coils the same inductance and balance them using potentiometer

. And does the compensating one disappear? I was thinking of connecting the two RX in one direction, and the com in the opposite direction.

[pito]

You can make a Rx coil #1, 150T with diameter 100 mm, Tx coil 100T, diameter 200 mm, Rx coil #2, 100T diameter 300 mm. The number of turns of the second coil Rx should be adjusted to obtain the same induced voltage as on coil Rx # 1.
Wire diameter, Tx -0.5 mm, Rx (not important ) 0.3 mm.

[pito]

. And does the compensating one disappear?

= yes

[Ivont]

= yes

Does what is in the picture make sense? So far, the greatest depth, in an air test, gave a similar DD, butterfly type. I called it that because it has a similar shape. That was more than 20 years ago. Since I did not see it made by anyone, I did not test it in the field. This coil gave almost twice the distance of a double D.

[pito]

That is the case when both Rx coils are the same as on picture

[pito]

[Ivont]

I liked the one above with the trimmer. I'll replace it with resistors until the potentiometer value becomes the smallest.
It's better to have zero without a trimmer (in series). Maybe with a winding.

[Detectorist#1]

Hi pito & Ivont,
7 years ago I was very impressed from this solution with one outside TX coil and two inside RX coils with differential connecting. On the air tests all was excellent. No influence of 50(60)Hz fields and very good sensitivity for small nuggets. But in real tests on real ground the results was very disappointing. First, the magnetic field of the Earth have to be eliminated with bipolar TX pulses (when the coils are moved - not the targets) . Second, the technic of searching is not very convenient - the balance of the RX signals is loosed when you dig the hole in the ground. At this point, the advantages of good symmetrical RX coil is loosed. After digging of the hole you have to use other sensor.

[Ivont]

Hi pito & Ivont,
7 years ago I was very impressed from this solution with one outside TX coil and two inside RX coils with differential connecting. On the air tests all was excellent. No influence of 50(60)Hz fields and very good sensitivity for small nuggets. But in real tests on real ground the results was very disappointing. First, the magnetic field of the Earth have to be eliminated with bipolar TX pulses (when the coils are moved - not the targets) . Second, the technic of searching is not very convenient - the balance of the RX signals is loosed when you dig the hole in the ground. At this point, the advantages of good symmetrical RX coil is loosed. After digging of the hole you have to use other sensor.

[Ivont]

You guys have a lot of experience overall. Of these coils, which one do you think will work better, all things considered.