PI Detector Coil Design — Offset TX/RX with Self-Powered Bucking (Prior Art Disclosure)

[detectormods]

Thoughts?
When a bucking coil is not.


https://youtu.be/ZAXOePkerOk

[Detectorist#1]

Hello detectormods,
24 hours of silence - maybe your idea is too unusual. The scheme is very unclear. Maybe this is one of the reasons for this silent state.
Attached is more clear scheme of your idea.

[detectormods]

Hello detectormods,
24 hours of silence - maybe your idea is too unusual. The scheme is very unclear. Maybe this is one of the reasons for this silent state.
Attached is more clear scheme of your idea.

Nice schematic, it’s more like most people do not understand what it does. I built a test coil and it greatly reduces mineral ground response.

[Carl-NC]

In my case, I have been on planes for the last 24 hours. I'll try to watch the video tomorrow.

[Detectorist#1]

Maybe the bucking coil in this case is more exactly to be named "load coil" similar to used in US4,255,711 patent.

[Detectorist#1]

The silence has been going on for 6 days now. We await for the opinions of the gurus in PI detectors - whether this idea is a revolutionary solution to improving the "ground balance" feature in PI detectors.
Also, the resistor R3 (0.22oHms) in the scheme is not "current sense" resistor. This is only base, minimal resistor for controlling of the time-constant of the additional circle.

[Aziz]

I haven't much time to look at the concept yet. But there are much simpler coil designs to get more performance. I don't see any benefit right now.

[moodz]

The TVS diode PESD5VDS1BA clamps at 14.5 volts and breakdown at 9.5 volts. I suppose its there to control flyback excursions.

The problem with the circuit is RV1 ... the need to adjust is missing the fact that you could easily have a feedback loop that optimises the circuit on a continous basis.
Besides a trimpot is asking for reliability issues down the track especially if it is located in the coil.

There are too many new ideas floating around at the moment and so little time ... so maybe woody could build a version of this and demonstrate something.

.. he has more gear in his workshop than most people.

[Carl-NC]

Here is what I understand of the concept:

1. A passively loaded "bucking" coil is placed between the TX and RX coils.
2. The bucking coil produces an exponential decay response that couples to the RX coil.
3. The hope is that the bucking signal is equal and opposite to the ground response, thereby canceling it.

Here are the issues I see with the idea.

1. The response of viscous ground (what we are concerned about) is not exponential, it is a power-law response. So a generated exponential cannot cancel it.
2. Unless I missed something, the RX bucking signal amplitude is constant whereas the RX ground signal depends on the height of the coil above the ground.
3. Again, unless I'm missing something, the bucking signal will be in-phase with the ground signal so it will add, not cancel.

I admit I have not given this a lot of thought so take it with a grain of salt.

[detectormods]

Here is what I understand of the concept:

1. A passively loaded "bucking" coil is placed between the TX and RX coils.
2. The bucking coil produces an exponential decay response that couples to the RX coil.
3. The hope is that the bucking signal is equal and opposite to the ground response, thereby canceling it.

Here are the issues I see with the idea.

1. The response of viscous ground (what we are concerned about) is not exponential, it is a power-law response. So a generated exponential cannot cancel it.
2. Unless I missed something, the RX bucking signal amplitude is constant whereas the RX ground signal depends on the height of the coil above the ground.
3. Again, unless I'm missing something, the bucking signal will be in-phase with the ground signal so it will add, not cancel.

I admit I have not given this a lot of thought so take it with a grain of salt.

An extension to the coil is the addition or a servo control loop, as per ADC and DAC or a variable decay plus signal level feed back inside the detector, there is also ways to add servo loop control interfaced to another interwoven buck winding thus controlling magnetic interaction with both the ground and signal responses.

[Detectorist#1]

And what is the final verdict for this idea - this candidate for patent go to the trash?

[detectormods]

The offset is not patented

[Detectorist#1]

The offset from TX and RX coil is OK as written in "Minelab 8000" tread with "double side search coil" but what about the real profit with "self powered GB coil"?

[detectormods]

It’s a cancellation or reduction of ground phucking up the signal to noise ratio .

[Detectorist#1]

Hi detectormods,
Thank you for this explanation. Unfortunately, It is not easy to make real tests - special coil, different soils and enough free time we need.