TESORO GOLDEN SABRE

[Max]

Hi,
I've checked bandidoII and TGS switching stuff...

and it's this way like in first picture.

The fact you read negative amplitude for non-ferrous is not a problem cause there are 2 inverting amplifiers along channels in the chain... so , at the end, the result is the same as Qiaozhi wrote: non-ferrous will give rise of amplitude on disc channel before comparator, non-ferrous will give fall in amplitude in disc channel before comparator. Both ferrous and non-ferrous items will rise the amplitude of geb channel before comparator.

The combined effect is that the non-ferrous are detected and ferrous are masked out by opposition of signals in the 2 channels.

GEB sample intercepts the positive edge zero-crossing of RX; disc instead intercept the positive peak of RX signal.

Qiaozhi... what do you think ? Is correct now ? (I hope so...)

Now I think I can drink my wiskey and smoke that dang Clint-Eastwood-like cygar...

Kind regards,
Max

[Max]

"..The ground (if not mineralized) only causes a change in amplitude, but no phase-shift. Hence there is no audible beep when the coil is lowered to the ground...."

This is true and very useable to know when nulling coil.
Using ferrite rod man can simulate partially ground conditions.My reference when nulling coils is situation when scoped RX only react by huge amplitude rise without producing any sound, on closing rod to coil surface. Monitoring residual voltage and RX scope i adjust coil to achieve that situation without worries on other things. Once i achieve minimal residual voltage and adjust GEB not to produce audio on rod i know coil is properly nulled.
In theory this method could be argued, in practice such coils are shoving really best performances in 100% cases. Rock stabile and excellent depths.
I didnt scope phase angle preciselly due bad and obsolete scope i have.
Yet i noticed one more interesting thing;
let's presume coils are nulled and RX having residual voltage 5mV, closing iron claws transversely to coil surface voltage rises from 5 to ...let's say 15mV.
But what really suprised me is when i turn same iron claws perpendiculary respecting coil surace, voltage drops fast to 1mV and even zero!!!?
What is going on here? Sheesh! I dont understand this!?
Iron claws in other orientation seems to "suck" voltage?
Same case was with some Cu alloys!? Same Cu alloys are bairly detectable with ordinary PI detector (as i noticed previously)????
Another case is "ring" phenomena; circle shaped piece of metal would be good detected, yet if we drill a hole in it - it would be much louder detected!
Take a coin drill 5mm hole in its center. Than try to detect it. You will be amazed of much stronger signal it would produce than!
Some (very few) alloys do "suck" induced voltage, yet some do amplify it more.
Phase shift meter i tried to achieve turns to be pretty unprecize and unaccurate. I am searching better method (simplier than scope) to monitor this on various items and metals.
Regards!

Hi Ivconic,
how are you ? Hope you're fine... and play a lot with MDs out there... I think you can do that also for me... I mean, bad weather here still and not much searching!

About phase shifts... I see them on scope all the time at now ... but still I don't realize good way how diagrams like in the Gifford's patent were made.

I mean... when I near iron items I get the left shift on RX signal but it become more and more high more the iron stuff is big (of course) and near coil... but I cannot distinguish between phase of little iron item and little gold item at say 20cm from coil and too at 10cm, seems really close. I see phase change BUT seems so few change on screen!

Anyway devices disc the right way so maybe is just that a scope is not enough to see that dang little phase shifts in a good way. That's why I still consider interesting your circuit for phase meter... it will be cool if works good... but I read you had problems with it.

I think that who made diagrams of that phases had really serious phase meter, probably thousands dollars professional instrument will show that phases in a consistent measuring environment within particular distances etc... but seems really inconsistent method to evaluate nature of target cause phase change a lot when items are very near to coil.

What I see that's nice is that the effect of ferrous/non-ferrous over amplitude changes is much more noticeable than phase shifts... I also start seriously thinking that all that mantra about phase shifts in VLFs is just another misleading concept and behind the scene is amplitude variation that makes the real difference, as Qiaozhi wrote... not this way... but I think concept is enough clear.

I can disc the gold item and iron nail from 30cm watching at amplified peak movements of RX signal, but cannot disc by phase even at 10cm watching the dang scope screen!

What do you think ?

Kind regards,
Max

[Max]

Hi Max,

I don't think this is quite correct.
The Gifford patent can be a bit confusing, especially when you start building your own detectors, and the results don't appear to match.
I think the main problem is that the Gifford patent shows the phase-shifts associated with an under-nulled coil, whereas the Tesoro coils are over-nulled. (See my previous reply to zzy.) This means that all the phase-shifts are to the right, and the metal sampling point is on the negative-going zero-crossing, not the positive-going, as for the Tesoro. You should also note that the MINERAL signal is actually the RX signal in it's ground balanced position (i.e. no metal present) and this has been assumed to have a starting phase-shift (relative to the TX) of -90 degrees. For the Tesoro coils, this phase-shift is something like +30 degrees.

Hi,
sorry if this story is going long time... but I'd like to understand which are correct diagrams for both the patent and the tesoro mds like TGS and this stuff is bocoming really confusing now.

Please look at corrections. Do you think are right this way ?

Kind regards,
Max

[Qiaozhi]

Hi Qiaozhi,
I don't know if it is right... maybe you could say that.... but I tryed to make a diagram of tesoro's coil response to targets like in original patent but considering left phase shift as happens on it and we see on the screen.

I've added also points where I think sampling is done...

Maybe this could make more easy to figure out device working...

Do you think it is right or I made a big mess ?

Kind regards,
Max

Hi Max,

I don't think this is quite correct.
The Gifford patent can be a bit confusing, especially when you start building your own detectors, and the results don't appear to match.
I think the main problem is that the Gifford patent shows the phase-shifts associated with an under-nulled coil, whereas the Tesoro coils are over-nulled. (See my previous reply to zzy.) This means that all the phase-shifts are to the right, and the metal sampling point is on the negative-going zero-crossing, not the positive-going, as for the Tesoro. You should also note that the MINERAL signal is actually the RX signal in it's ground balanced position (i.e. no metal present) and this has been assumed to have a starting phase-shift (relative to the TX) of -90 degrees. For the Tesoro coils, this phase-shift is something like +30 degrees.

[Qiaozhi]

No, my test is all metal the RX signal shift always to the right,but the ferrite is shift to the left.

I think you have to reverse RX coil leads to gain good disc and have same kind of shift there.

This is not because your RX coil leads are reversed. It is because your coil is under-nulled, rather than over-nulled. During the nulling procedure, as you move the two coils together (I assume it's a DD configuration) the residual RX voltage will be reduced. You need to pass through this minimum and null your coils on the other side of this zero-voltage point. In other words - on one side of the null, all metal targets gives a phase-shift to the right, and on the other they give a phase-shift to the left. Although you can get both configurations to work, the left phase-shift position gives the most sensitivity and better discrimination.

[Max]

Hi Qiaozhi,
I don't know if it is right... maybe you could say that.... but I tryed to make a diagram of tesoro's coil response to targets like in original patent but considering left phase shift as happens on it and we see on the screen.

I've added also points where I think sampling is done...

Maybe this could make more easy to figure out device working...

Do you think it is right or I made a big mess ?

Kind regards,
Max

[Qiaozhi]

This is true and very useable to know when nulling coil.
Using ferrite rod man can simulate partially ground conditions.

Yes - this is a good method to use, and gets you closer to the real ground conditions.

Yet i noticed one more interesting thing;
let's presume coils are nulled and RX having residual voltage 5mV, closing iron claws transversely to coil surface voltage rises from 5 to ...let's say 15mV.
But what really suprised me is when i turn same iron claws perpendiculary respecting coil surace, voltage drops fast to 1mV and even zero!!!?
What is going on here? Sheesh! I dont understand this!?
Iron claws in other orientation seems to "suck" voltage?
Same case was with some Cu alloys!? Same Cu alloys are bairly detectable with ordinary PI detector (as i noticed previously)????

When you say "closing iron claws" do you mean an iron ring?

Another case is "ring" phenomena; circle shaped piece of metal would be good detected, yet if we drill a hole in it - it would be much louder detected!

Take a coin drill 5mm hole in its center. Than try to detect it. You will be amazed of much stronger signal it would produce than!

This is easy to explain ... any metal object formed into a ring (possibly by drilling a hole in it) will promote the formation of eddy currents, thus making the target more detectable. This may also be the answer to your previous question concerning the "closing iron claws".

[ivconic]

Hi,
Ivconic.
Did you ever tryed to test TGSL with that original coil that you have from your broken RH?
Buy the way what is the probleme with this preshes piece?

No, doesn't make any sence. RH coil is designed for 5kHz.
What is "preshes piece"? RH? Burned permanently!

[Max]

Hi Max,

I am pleased that you have independently confirmed that all the phase-shifts are to the left. Otherwise this was going to get complicated to explain.

As far as the GEB channel is concerned, only metal targets cause a phase-shift. As these shifts are always to the left, a positive signal is generated that causes an audible beep in the headphones. That's why sampling at the zero-crossing is necessary. The ground (if not mineralized) only causes a change in amplitude, but no phase-shift. Hence there is no audible beep when the coil is lowered to the ground.

For the DISC channel, the discrimination relies soley on amplitude changes - increase for non-ferrous and decrease for ferrous.

The confusing thing about the diagram in the Gifford patent is that the phase readings are taken relative to the TX signal, and this is why you end up with positive and negative phase values.

Hi,
I've made a little mod to diagram... and this is what I think could be related to a real situation following your last posts.

Please let me know what do you think about, if is correct or not.

The sample for geb is where RX goes from negative to positive: since ground itself doesn't give phase shift (or that cause one rotate knob to compensate phase related to minerals in soil in mineralized ground) we have no phase shift if bobbing the coil up-down for say 20cm from soil level , so the peak-peak amplitude rise due to to bobbing coil up-down is made of a positive and negative components of equal amplitude, thus resulting in no change in amplitude at geb channel cause of moving coil up-down during e.g. a sweep cycle.

This, virtually, eliminate any ground influence on amplitude of signal at geb channel; when a metal is near coil the effect will be always the same, rise or fall in amplitude due to phase shift (in diagram is fall but nevermind cause the negative half-wave slide to right due to metal presence).

About disc channel, instead, we can find a pi/2 (90°) shift for ideal sampling of a quadrature demodulator; in practical terms usually the sample is delayed a bit more and then a better "separation" of target composition is realized.

Since we are (on disc channel) sampling near the positive peak of wave and rx signal slide to right when metals are present, there will be positive readings for relative phase shifts under 90° or a bit more degrees, then after we'll see negative readings of amplitude for larger phase shifts.

This way, in that diagram, we'll end up with a positive reading for e.g. iron and a negative reading for the "coin".

Now, actually, what happens in Tesoro coils is the opposite we see in drawing, cause RX shift happens to the left respect TX reference but apart this the system works exactly like explained. Then e.g. inverting amplifiers will convert negative rise into a positive rise etc giving right signs to voltages.

I miss something along the road ?

Kind regards,
Max

[ivconic]

"..The ground (if not mineralized) only causes a change in amplitude, but no phase-shift. Hence there is no audible beep when the coil is lowered to the ground...."

This is true and very useable to know when nulling coil.
Using ferrite rod man can simulate partially ground conditions.My reference when nulling coils is situation when scoped RX only react by huge amplitude rise without producing any sound, on closing rod to coil surface. Monitoring residual voltage and RX scope i adjust coil to achieve that situation without worries on other things. Once i achieve minimal residual voltage and adjust GEB not to produce audio on rod i know coil is properly nulled.
In theory this method could be argued, in practice such coils are shoving really best performances in 100% cases. Rock stabile and excellent depths.
I didnt scope phase angle preciselly due bad and obsolete scope i have.
Yet i noticed one more interesting thing;
let's presume coils are nulled and RX having residual voltage 5mV, closing iron claws transversely to coil surface voltage rises from 5 to ...let's say 15mV.
But what really suprised me is when i turn same iron claws perpendiculary respecting coil surace, voltage drops fast to 1mV and even zero!!!?
What is going on here? Sheesh! I dont understand this!?
Iron claws in other orientation seems to "suck" voltage?
Same case was with some Cu alloys!? Same Cu alloys are bairly detectable with ordinary PI detector (as i noticed previously)????
Another case is "ring" phenomena; circle shaped piece of metal would be good detected, yet if we drill a hole in it - it would be much louder detected!
Take a coin drill 5mm hole in its center. Than try to detect it. You will be amazed of much stronger signal it would produce than!
Some (very few) alloys do "suck" induced voltage, yet some do amplify it more.
Phase shift meter i tried to achieve turns to be pretty unprecize and unaccurate. I am searching better method (simplier than scope) to monitor this on various items and metals.
Regards!

[Max]

HI Max

"The RX signal shift always to the left, no matter of target composition."
???
No, my test is all metal the RX signal shift always to the right,but the ferrite is shift to the left.

Hi,
I'm totally sure of that. I checked yesterday with my original tesoro coil (9x8'' )and shift happens to the left with metals.

I tested many stuff, iron, copper, silver, gold, brass, bronze... etc always RX signal shift to the left side.

I think you have to reverse RX coil leads to gain good disc and have same kind of shift there.

Kind regards,
Max

[zzy]

Hi,
I've tested again my Tesoro coil... and got results like you wrote about (now I remember I saw this stuff during bandidoII cloning but then forgot about).

The RX signal shift always to the left, no matter of target composition.

The question is now... what's the purpose of the diagram of above when in their coils the phase shift is always one way no matter of target?

I understand even less now!

Maybe the reference point is somewhere else than at zero crossing of TX ???

Kind regards,
Max

HI Max

"The RX signal shift always to the left, no matter of target composition."
???
No, my test is all metal the RX signal shift always to the right,but the ferrite is shift to the left.

[Qiaozhi]

Hi,
I've tested again my Tesoro coil... and got results like you wrote about (now I remember I saw this stuff during bandidoII cloning but then forgot about).

The RX signal shift always to the left, no matter of target composition.

The question is now... what's the purpose of the diagram of above when in their coils the phase shift is always one way no matter of target?

I understand even less now!

Maybe the reference point is somewhere else than at zero crossing of TX ???

Kind regards,
Max

Hi Max,

I am pleased that you have independently confirmed that all the phase-shifts are to the left. Otherwise this was going to get complicated to explain.

As far as the GEB channel is concerned, only metal targets cause a phase-shift. As these shifts are always to the left, a positive signal is generated that causes an audible beep in the headphones. That's why sampling at the zero-crossing is necessary. The ground (if not mineralized) only causes a change in amplitude, but no phase-shift. Hence there is no audible beep when the coil is lowered to the ground.

For the DISC channel, the discrimination relies soley on amplitude changes - increase for non-ferrous and decrease for ferrous.

The confusing thing about the diagram in the Gifford patent is that the phase readings are taken relative to the TX signal, and this is why you end up with positive and negative phase values.

[Max]

Hi,
I've tested again my Tesoro coil... and got results like you wrote about (now I remember I saw this stuff during bandidoII cloning but then forgot about).

The RX signal shift always to the left, no matter of target composition.

The question is now... what's the purpose of the diagram of above when in their coils the phase shift is always one way no matter of target?

I understand even less now!

Maybe the reference point is somewhere else than at zero crossing of TX ???

Kind regards,
Max

[Max]

Hi Max,

How the RX signal phase-shifts, and what happens to the amplitude for various targets, very much depends on the coil configuration. For the Tesoro coils they all produce a phase-shift to the left for all targets, and the amplitude increases for non-ferrous, and decreases for ferrous. This can be easily confirmed by monitoring the RX signal at the output of the preamp with a scope, while triggering from the TX signal.

Yes - you could directly measure the phase-shift in the RX signal relative the TX and display this on a phase meter, but the phase measurement is also dependent on the distance of the target from the search coil. This is why target ID is so unreliable, and you can often end up digging a really deep hole and finding a nail.

The 2-channel approach is a simple elegant way of solving the discrimination problem, even though it's not perfect.

Hi,
I noticed some stranges on my original Tesoro-coil (8x9'' spider) but cannot understand when you say that all targets give left shifts, cause also Gifford's patents report devices rely strictly on phase shift detected at RX coil signal.

In picture I captured a part of patent reporting phase shifts for various metals and mineral soil.

How could be possible that targets produce just left shifting of RX waveform and detectors works just considering amplitude of RX signal there ??? Seems impossible to me the things go that way.

Let me explain... I know the amplitude shift happens and are present on RX signal at preamp out BUT on disc channel ,after demodulator, this is due to positive or negative phase shift the RX signal is subject to cause of a target.

The demodulator idea rely on this stuff: if you can disc just considering the rise or fall of amplitude signal at preamp out, why the need of a sync demodulator there ?

Consider the dashed line in the picture: there is the sample for disc channel... as you can see sampling there "good" targets (non-ferrous) will give a rise in amplitude and "bad" (ferrous) like iron nail will give zero and mineral soil negative amplitude shift. But this just cause of RX signal phase shift.

Am I wrong on this ? Maybe I miss something or made some mistake...

Kind regards,
Max