Induction Balance Stuff - Single/Multi Frequency Response, GB, Disc, Measurements, Ideas, Fun, etc.

[Aziz]

Hi all,

I am chatting with the AI about the Hilbert Transform, envelope extraction and FFT of the envelope.

It says, that the mono coil VLF with dual-frequeny mode around the resonant frequency will work on severe ground conditions (iron ore gold fields).
Even there is a High-Q LC-tank (of approx. 30 in my case).

Well, let's look at this feature in detail.... a quick & dirty hack to the software is required..
My mate Donald is going to be very very rich soon ...

[Aziz]

The AI says, that the Hilbert-Transform -> Envelope -> FFT
isn't really required.

The Goertzel demodulation (or Lock-in amp) delivers enough and more efficient information for GB and target detection.

This is quite a funny chat.

I should do more chat with the AI.

[Sergey_P]

<High-Q LC-tank (of approx. 30 in my case).>
A change in the ground signal level causes a phase shift in the resonant circuit due to the change in its parameters, not due to the induced signal from the ground/targets. This phase noise will interfere with target detection and cannot be compensated for.

[Aziz]

Hi Sergey,

<High-Q LC-tank (of approx. 30 in my case).>
A change in the ground signal level causes a phase shift in the resonant circuit due to the change in its parameters, not due to the induced signal from the ground/targets. This phase noise will interfere with target detection and cannot be compensated for.

but I can do it. There are more ways to do it. Note, that I have 2 / 4 I/Q vectors for processing.
A robust mono/IB-coil VLF design in severe ground conditions is possible.
Even with an extremely High-Q design.

[Aziz]

Hi all,

lets think of big, bigger and max!

I wonder, whether it is possible to operate the High-Q VLF detector as a Ground Loop VLF detector.
5 m or more diameter coil layed on the (severe mineralized) ground. The operating frequency can be set to the ground conditions (automatic).
A thick 3 or 5 core power cable can be realized as TX coil (all cores connected in series to form a big TX coil).
A thin cable for TX coil powering (due to High-Q, less power drain is required).

A second smaller coil as RX (20 - 30 cm diameter). The real search coil.
There won't be high voltage induced there. But the RX coil will pick-up target resonse. And the local mineralisation change. Plus the coil position change (pure X-response).
Searching inside the big TX coil.
X-response due to search coil sweep can be really handled.

I have to ask the AI sometime...
Aziz

[moodz]

Hi all,

lets think of big, bigger and max!

I wonder, whether it is possible to operate the High-Q VLF detector as a Ground Loop VLF detector.
5 m or more diameter coil layed on the (severe mineralized) ground. The operating frequency can be set to the ground conditions (automatic).
A thick 3 or 5 core power cable can be realized as TX coil (all cores connected in series to form a big TX coil).
A thin cable for TX coil powering (due to High-Q, less power drain is required).

A second smaller coil as RX (20 - 30 cm diameter). The real search coil.
There won't be high voltage induced there. But the RX coil will pick-up target resonse. And the local mineralisation change. Plus the coil position change (pure X-response).
Searching inside the big TX coil.
X-response due to search coil sweep can be really handled.

I have to ask the AI sometime...
Aziz

Its been done and patented Aziz .. woody did one some time ago.

[Aziz]

Hi Paul,

Its been done and patented Aziz .. woody did one some time ago.

No problem.
It will be a fully different technology. It's a VLF not pulse induction. Nor synchronized to the transmitter.

A very simple one:
High power, single frequency, stable and free running LC-Oscillator with a big ground loop (10 - 20 m or larger diameter).
No cables to the detector at all. The power transmitter with big battery can be placed on the ground.

The detector consists of only an anti-interference concentric co-axial (small) RX coil (+ processing unit).
Single channel, single frequency VLF processing.
Hilbert-Transform or SPLL with phase-tracking info.

TX coil current may be 1 - 5 A. TX voltage can go 500 - 2000 V (depending on the capacitors). Better a High-Q TX LC-tank for more power efficiency.
The TX coil won't "detect" ground response: it isn't changing its inductance anymore when it is placed on the ground.

Most of the time the RX coil will pickup in-phase response (X-response). This is due to coil coupling change during swinging and changing position. This can be handled.
Any off-phase response is target response (R-response).

This is feasible.
You may ask your AI mate too.

A ground breaking big deep gold monster chaser.

Cheers,
Aziz

[Aziz]

The only problem will be the free-running LC-oscillator (phase/frequency instability may be too much).
But this can be replaced with a programable frequency oscillator (crystal source, adjustable to ground mineralization, via MCU).
With blutooth-link.

[Aziz]

Hi all,

ground loop systems are really not much practical to use. Especially on virgin ground.
But a larger portable frame coil is the next best option.

------
Back to my previous dual frequency VLF:

TX coil (either mono or IB):
Thick litz coil wires for High-Q LC tank are going to be a problem with the cabling.
Best option is to keep the thick litz coil wire inside the coil housing. And the parallel tuning capacitor Ct too. So the huge current keeps flowing inside the coil housing and not through the cabling system. The feed-in cabling can be thin wire (low current flowing).
The two series capacitors and the two resistors for the voltage divider fits into a thin plastic tube (must be shielded). No bread board required at all.

Well, I could take much thicker tinned litz wire for the TX coil now (min 2.5 mm²).
Max Q, max bang, max sensitivity, max muscles (heavy TX coil ).

I could rise the Q back again (Q > 60 or more).

It doesn't matter, when the LC tank is out of tune due to heavy ground mineralisation and TX inductance change.
We have two frequencies f1 and f2. And they can be adapted to ground conditions.

Aziz

[Aziz]

I forgot to mention:

The feed-in can be also made with rectangular pulses (PWM output of MCU). Take a simple push-pull driver (a two channel mosfet driver) with external power supply and you are on game.
The mosfet driver delivers enough power for this purpose.
This project can be well fitted fully into an embedded MCU project (STM32.. ) .

Aziz

[Aziz]

Hi all,

this is my latest KISS Dual-Frequency Induction Balance VLF Detector Controller for sound card use.
Operated at moderate power consumption in high-gain mode of G6 (mid-level output, TX coil voltage up to 100 Vp).
The Q of the LC tank is still high enough (approx. 10).

At maximum output level (7 Vp), the TX coil voltage will go up to 250 Vp and the sound card may get hot too. It is very likely, that it switches itself off due to high current protection triggering.
Anyway, this is a KISS power beast.

The search coil is an IB coil. You will get very high sensitivity and depth.
The very sophisticated digital signal processing will also allow operation of heavy ground mineralisation.

All parts must be placed inside the coil housing. The coil cable bears only low voltage and low current and can be a thin and flexible shielded stereo earphone cable (2x Stereo, Input, Ouput).
You need low loss, high voltage rating FKP (Foil) capacitors.


Cheers,
Aziz

[Aziz]

PS:

On very mild ground mineralsation:
It can be operated at single frequency in differential mode.

On heavy to severe ground mineralsation:
Two frequency mode (f1, f2) -> 4 I/Q vector processing required.

[Aziz]

We have a good IB-VLF base now.

Now back again to pure mono coil VLF:
- It must have high Q.
- Less power drain. High power efficiency.
- Must work with standard line output level (1 V rms) and with every sound card this time.
- KISS & cheap design.
- All parts in the coil housing.

I know, the circuit can be made much more elegant this time.
We need a KISS masterpiece.
AI isn't smart enough to help me.

But I'm working on this right now:

Differential input mono coil. So we are processing both input channels at two frequencies now.

And I have found a real bug in LTspice in AC analysis.
I had to destroy the symmetry of the circuit by adding 1 pF to C1. It helped to override the bug.

Cheers,
Aziz

[Aziz]

Hi all,

I have made the modification to the latest mono coil VLF bread board. It is working very nice.

DSP path:
Differential input: Signal = right-channel - left-channel (or vice versa)
Demodulation of Signal at frequency f1 -> I/Q vector 1
Demodulation of Signal at frequency f2 -> I/Q vector 2
Demodulation type: Goertzel or Lockin

So a two I/Q vector processing is enough. As there isn't any transmit reference anymore, we are working with changes of I/Q vector (dI/Q).
This detector handles even the heavy ground mineralisation. Very robust operation.

For most sensitivity and detection depth, we need the IB type circuit. We can process the TX coil signals (as mono coil VLF) + RX coil signals. At two frequencies. We can refer to the TX coil signal (phase relation), it has huge TX power, etc., etc., .. and it handles heavy ground mineralisation too.

Aziz