GROUND BALANCE ( without the ground :-) )

[Orbit]

Thanks Modz!

[boilcoil]

Thank you for all support.

[Detectorist#1]

Hi Orbit,
I agree with you - have a lot of magic in the PI-IB region.
First, the RX signals from the targets are appr. 10 times stronger at the beginning of the TX-ON time than the RX signals at the beginning of the TX-OFF time (after delay of 3-4us in both cases) and the signals after SAT stage haves well different polarity for Fe/non-Fe targets (high-low or low-high tones). I'm sure, this is old information for you but I'm new in this area and I'm impressed from the discrimination possibilities of the PI design with IB coil.

[Carl-NC]

My application uses a waveform that is characterised by a half sine voltage waveform ( at both the TX and RX coil ) ... I will let you work out what sort of current waveform in the TX coil generates a half sine bipolar voltage waveform

Basically you get a square wave current with quarter-sine rise & fall.


During the transitions you get both reactive & resistive components and a strong response from ground. If your targeting response is taken only during the dead time then a ferrite response will have vanished but viscous responses will still be present. I could see that if the power-law coefficient of viscosity was constant then you could then combine a sample from the transition with a sample from the dead time to cancel any such target. But the coefficient varies so I'm not so sure this will work for all hot rocks.

This is exactly what I was working on with the White's half-sine. The patent claims omitted the GB technique because I was still working on that and it was to be a follow-on patent. That never happened.

[moodz]

Basically you get a square wave current with quarter-sine rise & fall.


During the transitions you get both reactive & resistive components and a strong response from ground. If your targeting response is taken only during the dead time then a ferrite response will have vanished but viscous responses will still be present. I could see that if the power-law coefficient of viscosity was constant then you could then combine a sample from the transition with a sample from the dead time to cancel any such target. But the coefficient varies so I'm not so sure this will work for all hot rocks.

This is exactly what I was working on with the White's half-sine. The patent claims omitted the GB technique because I was still working on that and it was to be a follow-on patent. That never happened.

That is the waveform I use (general form of it anyway) ... though the GB technique will work with other waveforms.
This one was chosen because it has partial di/dt = 0 and partial di/dt = sin(x) there is no need for a waveform where i = 0 for some time because this waveform does have i = 0 for an instant and that is all that is required mathematically.
Sudden transitions are very hard to sample using an ADC unless the ADC is much faster than the transition rise / fall.

[moodz]

...so when you discover a fundamental technique and you are thinking about patents. Below is a serious product patent discussion ....


The IP Legal Herald spoke to Subtle Technologies’s CEO, Mark Subtleworth, and asked him why, if the company’s product worked as advertised, it had not been able to discover Seaward Innovations’ submarine patent before it surfaced.

“SubIntelligence is a submarine submarine patent finder,” Subtleworth told our reporter. “That is, it finds submarine patents covering submarine technology. It does not find submarine patents covering submarine submarine patent finder technology. Doing so would require some kind of submarine submarine submarine finder patent finder. We could, perhaps, have built a such a product, but who’s to say there aren’t submarine patents covering techniques to find submarine patents that cover submarine submarine patent finding techniques?”

“The problem repeats itself infinitely.”

[Carl-NC]

Indeed.

[moodz]

...so there is always stuff you think of "after" submitting a patent.

So I submitted an additional updated provisional patent application No 2025901098 METAL DETECTOR WITH IMPROVED GROUND BALANCE UTILISING VIRTUAL GROUND MATRIX

Now you might have a clue how it works.

[boilcoil]

Bravo Moodz,
Good move, you thought of everything.