About pulse emission and ground balance

[6666]

some more

[green]

Still trying to define the problem. Charted some signals that I think should be similar to gold rings? Trying to understand the advantage of sampling with an A-D vs an integrator. Signal greater with an A-D but don't know if S/N is better. Planning on charting US coins. Wondering if charts make sense or should be done different. Is doubling target sample time for ground sample time best or would a different ground sample time be better?

[ivconic]

I think maybe pulse technology is now at the top part of the S-curve in terms of any giant leaps. Now it is just tiny, incremental improvements.

Just as all other "conventional" md technologies too.
Reason more not to share in public possible improvements.
I don't think we will see anything "revolutionary" any sooner.
Direct sampling and everything hidden in code; that's the certain future of this any any other similar technology.
I am afraid that everything that could be done; ML did it already.

[Skippy]

I know very little about PI machines ... but isn't Alexandre Tartare's AquaManta / Fisher Impulse PI design using a dual coil, that reverses polarity every alternate pulse, apparently cancelling ground signal somehow?
I know that a basic circuit was posted by him on here, but no-one seemed interested in it.

[waltr]

I know very little about PI machines ... but isn't Alexandre Tartare's AquaManta / Fisher Impulse PI design using a dual coil, that reverses polarity every alternate pulse, apparently cancelling ground signal somehow?
I know that a basic circuit was posted by him on here, but no-one seemed interested in it.

Alternate pulse polarity cancels Earth Field Effects not Ground signal.

[dbanner]

Why not have 16 channels and the use of harmonic frequencies. Now that would be something!

Of course you would have to pull a wagon full of batteries behind you and have a wind powered turbine on top of the head for recharging.

Need to wait until 2050, when AI can write it's own software to process all the info from those channels.

[Skippy]

This is the 'twin-coil' thread I was referring to:
https://www.geotech1.com/forums/show...Metal-Detector

[green]

This is the 'twin-coil' thread I was referring to:
https://www.geotech1.com/forums/show...Metal-Detector

Thanks for the reminder. Looking at #1 I'm wondering how it eliminates ground.

[6666]

Thats about all he posted then he went commercial.

[dbanner]

In the Manta thread, the author states that the two coils are wound together for maximum coupling, yet they are wound in opposite directions.
I'm trying to visualize this arrangement. Are the two coils of the same diameter?
Next he states that the two coils have a resonance that HARMONIZE. This could be important point.
Next he states that the ground cancels (-g+g). So we can infer that there are two seperate channels that are summed, with one of the coils acting as the recieve coil for both transmit pulses from the two coils, however one of the recieved signals will contain a negative ground component (-g) because the coils are counter-wound(180 degrees) to each other.

Now when he states that the two coils have resonances which harmonize, Does he mean at full resonance (the fundamental frequency f)? or at some harmonic interval?

[green]

In the Manta thread, the author states that the two coils are wound together for maximum coupling, yet they are wound in opposite directions.
I'm trying to visualize this arrangement. Are the two coils of the same diameter?
Next he states that the two coils have a resonance that HARMONIZE. This could be important point.
Next he states that the ground cancels (-g+g). So we can infer that there are two seperate channels that are summed, with one of the coils acting as the recieve coil for both transmit pulses from the two coils, however one of the recieved signals will contain a negative ground component (-g) because the coils are counter-wound(180 degrees) to each other.

His second reply contains some scope pictures. https://www.geotech1.com/forums/atta...5&d=1462902729 The signals are opposite. After pulse decay nonferrous targets and ground have the same polarity so I'm wondering how it cancels ground and not the target.

[dbanner]

He stated he ends up with 2V. Don't know how.

[dbanner]

There is pulse 1 and pulse 2, and pulse 1 Rx then pulse 2 Rx
So pulse 1 first then pulse 1 rx, followed by pulse 2 and pulse 2 rx
Pulse 1 rx =+v+s (where s is ground effect)
Pulse 2 rx = +(-v+s)=+v-s (+ sign because the rx coil in counterwound 180 degrees and pulse 2 comes from coil 2)
Pulse 1 rx ADDED to pulse 2 rx=(+v+s)+(+v-s)=2v. (s is cancelled)
So I speculated two gated channels followed by a summing amplifier later down the signal path. I am just guessing.

[dbanner]

His second reply contains some scope pictures. https://www.geotech1.com/forums/atta...5&d=1462902729 The signals are opposite. After pulse decay nonferrous targets and ground have the same polarity so I'm wondering how it cancels ground and not the target.

Because with one recieve coil and two pulse sources (one in antiphase), only ground is cancelled. This is the author's assertion, I don't know.

[waltr]

In the Manta thread there is a schematic: BMC TECHNOLOGY MANTAMETALDETECTORS.jpg
This show that the two coils are energized in the same polarity in the circuit but their magnetic polarities are opposite by the location of a 'dot' on the coil symbol.
The way to wind such a coil is use bi-filar wire then connect the each TX MOSFET on opposite ends.

BMC TECHNOLOGY MANTAMETALDETECTORS 2.jpg
Is a scope capture that show of RX signal. Seen is the opposite polarity of the TX pulses.
What is not as obvious is the fly-back 'decay' polarities are the same. This is due to the coupling.

I first thought that the GB cancellation equation they presented was wrong but studing the schematic and scope capture I see have this could work.

Now when he states that the two coils have resonances which harmonize, Does he mean at full resonance (the fundamental frequency f)? or at some harmonic interval?

No idea what he means but wonder if this is a translation issue of technical words.