Taking a look at GROUND BALANCE on the bench

[Ferric Toes]

Only Aziz is not Betonkopf because he knows that we should make Fourier transform.

Für alle Betonköpfen (To all ConcreteHeads):

Your motto is:
I hate to think, I prefer to experiment.

For those who prefer to think, I will place suitable information in the WIDEBAND thread.

I've heard much about vapour detectors, now you are proposing a thought detector. When you have finished thinking, imagine you are completely cancelling the ground with no loss in range and completely noise free, then feel the imaginary weight of that huge nugget. Think what that will do for your bank account.

No Mikhail, the trick is to think and experiment, and not necessarily in that order.

Eric.

[mikebg]

I've heard much about vapour detectors, now you are proposing a thought detector. When you have finished thinking, imagine you are completely cancelling the ground with no loss in range and completely noise free, then feel the imaginary weight of that huge nugget. Think what that will do for your bank account.

No Mikhail, the trick is to think and experiment, and not necessarily in that order.

Eric.

This is absolutely true. I know two Bulgarian physicists working at CERN. They divide physics into two categories: theoretical physics and experimental physics. Theorists point to the experimentalists what to experiment. Then the experimental physicists spend huge money to satisfy curiosity of the theorists. Fortunately the experimentalists of metal detectors spend their time (and our time sometimes :-).
http://public.web.cern.ch/public/en/lhc/lhc-en.html

[Qiaozhi]

Your motto is:
I hate to think, I prefer to experiment.

Apart from being untrue (you only have to browse through the many forums to confirm that for yourself) it does lead to me to ask ... when are we going to see the results of your experiments? Or perhaps there aren't any?

I am very much in favour of exploring new ideas and new ways of doing things, but eventually you have to actually build something to prove whether it works or not. You cannot continue to push different methods or ideas as fact, when there is no concrete (pun intended) proof.

[Ferric Toes]

Hi Eric,


This confirms what I have read in several documents about magnetic viscosity. However, among the many samples I tested there are some with slightly different decays. How similar should they be?

Below are some decay curves. Test setup is a small cylindrical mono coil, samples are in film containers inside the coil, standard PI waveform with 50µs on and 2µs off. Decay curves start approx. 5µs after the 2µs pulse. The TX coil decay curve was removed in the oscilloscope by subtraction, i.e. the plots show the pure decays of the samples. All initial amplitudes are equal so that the curves can be superimposed as in plots D) and F).

I actually made these to show how close the viscosity decay can be to that of metallic targets. It is very easy to get almost the same decay curve with two rings with different TCs by simply varying their distance and angle. This simulates the problem with the detection holes in GB systems that subtract a later sample from an earlier one.

Samples:
A) Hematite powder (alpha-Fe2O3, could also contain some amount of gamma-Fe2O3/maghemite):
http://www.kremer-pigmente.com/en/pi...ght-48100.html
The data sheet says the predominant particle size is 90nm
http://www.kremer-pigmente.com/media...lic/48100e.pdf
Maybe I try to convert some into maghemite as Aziz suggested here:
http://www.geotech1.com/forums/showt...ace-!!!/page59

B) Magnetic viscosity soil from my area (concentrated with a magnet)

C) A thin gold ring with one TC of 13.5µs

E) A thick silver ring with at least two TCs of approx. 15µs and 120µs

Thomas

[ATTACH]23599[/ATTACH]

Hi Thomas,

Nice set of curves, but it is difficult to see any differences between magnetic soil and metal targets with a linear display. If you can, try and convert them to 1) log amplitude/linear time. 2) log amplitude/log time. Targets like a ring will have a single exponential and have a straight line slope in 1), while ground will still appear like an exponential. Ground in 2) will appear as straight line slope, while the ring will curve downwards at late times.

Eric.

[mikebg]

So mikebg, do you have a working detector based on your many postings. Do you have any YouTube clips showing it's operation, if not we are all really interested to see what you have come up with, please post some YouTube clips.

Mickstv,
My hobby is design of TXs, RXs and antennas for QRP amateur radio. Just for that I'm posting here information for my hobby friends, who are ham designers. They do not need the circuit diagrams, PCBs and TV videoclips. They need theory that predict experimental results, they need analysis of block diagrams to design suitable circuit diagrams and they need algorithms to make suitable software.

There is a lot information in the WEB for builders like you. The builders like me need more knowledge because we are always dissatisfied with what is achieved. We allways think what to improve. Perhaps that supports our hobby still alive, although over 30 years all know that the HamRadio is a dying hobby.

As for PCBs, this forum is rich on worldclass experts for design and manifacturing. They can make this for you at highest professional level and manufacture PCBs of highest quality.

I can be useful to you only if you want to build a circuit diagram. I can show you the shortcomings of your diagram and how to improve it. Simply point me a circuit diagram.

[Ferric Toes]

Mickstv,
My hobby is design of TXs, RXs and antennas for QRP amateur radio. Just for that I'm posting here information for my hobby friends, who are ham designers. They do not need the circuit diagrams, PCBs and TV videoclips. They need theory that predict experimental results, they need analysis of block diagrams to design suitable circuit diagrams and they need algorithms to make suitable software.

There is a lot information in the WEB for builders like you. The builders like me need more knowledge because we are always dissatisfied with what is achieved. We allways think what to improve. Perhaps that supports our hobby still alive, although over 30 years all know that the HamRadio is a dying hobby.

As for PCBs, this forum is rich on worldclass experts for design and manifacturing. They can make this for you at highest professional level and manufacture PCBs of highest quality.

I can be useful to you only if you want to build a circuit diagram. I can show you the shortcomings of your diagram and how to improve it. Simply point me a circuit diagram.

However, I am sure that there are many on this forum, like myself, who are not so compartmented. I think I qualify as a researcher, developer, designer and builder. I have all those hats, and a few more, which I wear as appropriate.

Eric.

[Aziz]

Who got it?

Let's look how BW is doing the GB.

Aziz,
curing the huge greed of the big evil company

[ODM]

Let's look how BW is doing the GB.

I'd like to see how BW is doing with GB in the field, as it's touted on this forum about as eagerly as the Jeohunter, with equally few amounts of actual neutral demonstrations - surely you don't want it to look similar?
We might also need a cure for big mouths, or enough pudding to fill them. As we have some quotes, yet another quote goes, "Proof of pudding is in the eating" - or this time, perhaps the proof of a pudding recipe.


On a more serious note, thanks everyone for the reference documents posted in this thread. Along with the coil configurations documented elsewhere in the site and forums, it helps clarify the issues of GB in both balanced coil configurations and others. No tool of analysis is the perfect tool for all situations either, if there was the world's best micrometer it would still be a hassle to use it as a scale. Occam's razor is also a decent tool - it's best applied with caution, of course, but it helps with analysis of "unoptimal" designs. The first assumption shouldn't be that the people investing a long while of genuine research into something have their facts wrong. Best regards!

[PiTec]

Hi Eric,

Nice set of curves, but it is difficult to see any differences between magnetic soil and metal targets with a linear display. If you can, try and convert them to 1) log amplitude/linear time. 2) log amplitude/log time. Targets like a ring will have a single exponential and have a straight line slope in 1), while ground will still appear like an exponential. Ground in 2) will appear as straight line slope, while the ring will curve downwards at late times.

Below are the same decay curves with log/lin and log/log axes. Y= amplitude from 10 to 1000mV, X= time from 0 to 200µs. The problems I mentioned earlier are still visible:

• The curves for hematite and MV soil are not exactly the same (also easy to see in the lin/lin plot, there the red and blue curves are slightly different during the first 100µs). So my question was, how similar should they be? Also, they do not appear as a straight line slope in my plots. Maybe the TX fields I used were too strong and there is a distortion by saturation effects?
• First order (one TC) targets like the gold ring have a straight line slope in the log/lin plot, but as soon as there are more TCs involved (like the silver ring), the delay can become very similar to the viscosity decays.

If anyone wants to take a look at the data, here is the Excel file: decay_curves.rar

Thomas

[mikebg]

. . .
I am very much in favour of exploring new ideas and new ways of doing things, but eventually you have to actually build something to prove whether it works or not. You cannot continue to push different methods or ideas as fact, when there is no concrete (pun intended) proof.

George, the Frequency domain is not new idea and new way of doing things. It is old powerful tool for analysis, design and measurement. Only it is used for design of radio equipment because the Time domain is not suitable. It is not suitable even for design of narrow band metal detectors. Then why should we use it for analysis, measurement and design of PI, TEM, triangular wave and other type wideband metal detectors?

Look above how two professional designers - Eric Foster and Thomas Breuer are compartmented in time domain. They even do not suggest how more useful information will be obtained from their diagrams if they are represented in Frequency domain. Every time function will be splited into two frequency functions which show what is happening and what needs to be done. Then they will see that gold and silver generate first order response and only conductive permeability generates second order response.

The "worlds best" BBS, FBS and FBS2 technologies of MINELAB are not new ideas and new ways.
http://www.minelab.com/emea/consumer...chnologies#FBS
They use Frequency domain, the old tool born about 200 years ago. Scientists of 19-th century also need several decades to understand that the most powerful tool is born. No need to prove whether MINELABs technologies work or not. Engineers need knowledge to understand how they work. They should read patent US4506225. It describes the discrete signal processing at WIDEBAND technology. Described is the modern technology despite the patent pending is written in 1981.

[bklein]

Useful?: http://www.st.com/st-web-ui/static/a...DM00075867.pdf

[KahlesMilcon]

Sorry for the Post.

KM, the soil in NC (I lived there 21 yrs) doesn't come anywhere close to Oz. Even the reddest NC dirt doesn't have much viscosity effects. Oz detectorists sometimes refer to their soil as "corrugated iron." If you can get a hold of a sample, you'll appreciate NC conditions more.

I thought I had proofed the post , I guess I did not.

I should have said " is not" as strong ....

I was in now way trying to say that NC soil was any where near as problematic as AZ soils, I was only trying to say that the hot rocks that we have are if nothing else interesting and will when hit with a MD will blow your eardums out .



Thanks for the correction.


Ken

[Qiaozhi]

The first assumption shouldn't be that the people investing a long while of genuine research into something have their facts wrong. Best regards!

This is a very good point, and something many people seem to forget.

George, the Frequency domain is not new idea and new way of doing things. It is old powerful tool for analysis, design and measurement. Only it is used for design of radio equipment because the Time domain is not suitable. It is not suitable even for design of narrow band metal detectors.

At no time did I state that the frequency domain was a new idea. However, I have stated [twice already] that you cannot use frequency domain [small-signal] analysis for PI detector design, as the models are linearised around the operating point prior to the start of the simulation. PI circuits are inherently large-signal, and a frequency domain simulation will give incorrect results.

The "worlds best" BBS, FBS and FBS2 technologies of MINELAB are not new ideas and new ways.

This is true, but they are also not pulse induction detectors. BBS, FBS and FBS2 are VLF designs that transmit a series of square waves instead of the usual sine wave.

[Carl-NC]

The "worlds best" BBS, FBS and FBS2 technologies of MINELAB are not new ideas and new ways.
http://www.minelab.com/emea/consumer...chnologies#FBS
They use Frequency domain, the old tool born about 200 years ago.

Actually, BBS is closer to time-domain. It transmits 2 frequencies sequentially and processes them much like a PI. I suspect BBS and Fisher Impulse look a lot alike.

[Carl-NC]

However, I have stated [twice already] that you cannot use frequency domain [small-signal] analysis for PI detector design, as the models are linearised around the operating point prior to the start of the simulation. PI circuits are inherently large-signal, and a frequency domain simulation will give incorrect results.

Obviously you can't use FD sims for most PI hardware, so I wonder if Mike is referring more to "frequency domain thinking" rather than "frequency domain simulation."