TESORO GOLDEN SABRE

[Geo]

Hi
I conceive that as long as least it affects the Tx signal in the coil of the receiver we so much more can strengthen the Rx input and gain depth. Simply the subject is "up to who point it is in effect in the practice". From who point and beyond we do not have essential improvement?? And naturally this only in the practice will appear, whenever Ivconic because you make a lot of Coils you can make some trial on this and say us the results
regards

[Max]

The Tesoro coil that I tested is a 9x8 web coil, and it's reasonably new. The residual voltage is actually 13mVpp. I also tested a Laser concentric coil (same as Cortes) and this is 100mVpp! Both of them work absolutely fine. Unfortunately I cannot test my 10" concentric coil, as a wire is currently broken in the plug. Just need to get enough enthusiasm to re-attach it.
I do not own a tesoro widescan DD coil.

Personally I think you're taking this zeroing thing too seriously. The only difference you're likely to notice, if the residual voltage is too high, is worse discrimination for deep targets.

I'm sure that statement is going to spark off some interesting discussions.

Hi,
now I'm really confused too ! I belive your words ... so if you say that 13mVpp and 100mVpp for coils are good about working... OK.

But I cannot explain myself why I get so worse results with e.g. 20mVpp homemade coil... or why I get 3.5mVpp from my 9x8 and you get 13mVpp that's much more ...4 times what I have. Are Tesoro's procedures so different from coil to coil ? Or just your coil (or mine) is damaged ?

The 100mVpp coil I really don't understand how can it work on soil without giving much falsing... this is a real mistery for me.

So... what I read above means that 1 or 100mVpp change nothing about ground balancing ??? Which detector have you used to test them ? Has it the manual GEB pot on panel ?

I've noticed that I can compensate manually by GEB pot a higher "nulled" coil ... nulling ground influence by the axes system rotation but that is very critical do so with e.g. 20mVpp coil... and results are not so good as with 1mVpp coils.

Please explain... I'm really interested in that topic.

Best regards,
Max

[Max]

Hah,hah,hah,hah,hah !!!!!! I KNEW IT!!!!!
Damn! Now i cant sleep whole night!


Also...now....NOTHING CLEAR TO ME!
I dont understand this at all!?

Quiaozhi, tell me than; how the heck i will achieve good, stabile GEB???
If this is not dependable of good coil design....well..????
And i thought i know something!?
Regards!

Hi Ivconic,
I suppose he mean that if you rotate axes system by the right phase angle you actually null ground signal totally... so have no meaning that coil is nulled at 1mVpp or 100mVpp... cause projection of ground signal is always zero (90° to useful signal axis).

If so... you need to ground balance PERFECTLY to really zero out the ground signal... but I found it almost impossible to do if e.g. you don't use a 20turns pot for geb... of course... on the panel.

In theory it MUST work even at 100mVpp or more... BUT

then even slight variation of ground conditions or some fragments of read clay/bricks etc... can make you crazy with retune! That's my experience.

Am I right ?

Best regards,
Max

[ivconic]

"...In theory ..."


If i havent tested theory claims so many times...!!!?? I am dealing practically with things - always!
And my practice says that coil nulled so far from zero is.....unuseable on VLF machines!
OK i can accept totally unbalanced DD coil on PI detector. Never mind in that case...but on VLF???
As i assumed Quiaozhi's coils are more than damaged, that's why produce so much voltage...

Theory...heck!
I respect only things proved in practice. If i cant gain GEB with that coil than its "depth" in air means nothing to me!

...

[rdec4]

I make several test with 6 DD coils with 10mVpp and 20mVpp in my IB detectors (they aren't TGSL, and work in 8KHz).
I tuned these voltages over the table (height=0.7m) in my laboratory, when I made this coils.
When, I put the coil of the flooring in my laboratory, the voltage is changes (decrease with ~8-15 mVpp), and the balanse are: ~2mVpp (-5mVpp?) and 12mVpp (5mVpp).
Also, when I put the coil over the earth of 2-3cm, the balanse is changed.
The detectors with 20mVpp have better depth and stability in laboratory and in the ground.
I think, when the coil is tuned with 0mVpp in the room, she in the ground will have -15mVpp and detector will have less depth and stability. It's a my supposition of this mystery.

Sorry for my bad english.

[Qiaozhi]

Hi Ivconic,
I suppose he mean that if you rotate axes system by the right phase angle you actually null ground signal totally... so have no meaning that coil is nulled at 1mVpp or 100mVpp... cause projection of ground signal is always zero (90° to useful signal axis).

If so... you need to ground balance PERFECTLY to really zero out the ground signal... but I found it almost impossible to do if e.g. you don't use a 20turns pot for geb... of course... on the panel.

In theory it MUST work even at 100mVpp or more... BUT

then even slight variation of ground conditions or some fragments of read clay/bricks etc... can make you crazy with retune! That's my experience.

Am I right ?

Best regards,
Max

You are correct. Since the GEB sample pulse is positioned at the zero-crossing of the RX signal, then the output from the GEB analog switch (which is part of a sample & hold circuit) will be zero volts. Then only targets that produce a phase-shift (so that the pulse is not longer sampling at the zero-crossing) can cause a voltage to appear at the output of the gate. Neutral ground does not produce a phase-shift, only a decrease in amplitude. In this case the signal in the ground channel does not change.

The result is that 1mV, 15mV, 100mV ... it doesn't really matter that much how much residual voltage is there. The only disadvantages with a high residual voltage are worse discrimination for targets far from the coil, and more difficult (but not impossible) to ground balance.

I do not have a 20-turn pot on my detector, and ground balance is quite easy to achieve. Variation in ground conditions will always cause some falsing in a detector with manual ground balance, and fragments of ferrous brick can also cause some chatter. You should be able to eliminate this by increasing the level of discimination. By the way, the detector I'm using is my own design, but essentially it has the same classic 2-channel architecture used in many other analog detectors (with some refinements). The TX frequency is 10KHz and it uses the same capacitor values for the TX and RX coils on the Bandido. I've also checked this with an original Bandido and the results are the same. Maybe there is some quirk in the TGS design that causes this problem.

One thing you can be sure of is that Tesoro do not spend many hours trimming each coil to reduce the residual voltage. It just wouldn't make economic sense.

[Max]

I make several test with 6 DD coils with 10mVpp and 20mVpp in my IB detectors (they aren't TGSL, and work in 8KHz).
I tuned these voltages over the table (height=0.7m) in my laboratory, when I made this coils.
When, I put the coil of the flooring in my laboratory, the voltage is changes (decrease with ~8-15 mVpp), and the balanse are: ~2mVpp (-5mVpp?) and 12mVpp (5mVpp).
Also, when I put the coil over the earth of 2-3cm, the balanse is changed.
The detectors with 20mVpp have better depth and stability in laboratory and in the ground.
I think, when the coil is tuned with 0mVpp in the room, she in the ground will have -15mVpp and detector will have less depth and stability. It's a my supposition of this mystery.

Sorry for my bad english.

Hi,
yes you are right on conditions change: not the same nulling the coil on lab (e.g. suspended in air or over a wood/glued structure or plastic) and then on real ground. Of course, it's true that on the real ground you get the soil mineralization (iron oxides and the like) that put/increase magnetic histeresys of the whole stuff... then also the conductive part from ground (due e.g. to salts and wet)... then is the coil is not properly shielded also static charges accumulation and capacitive effects that change your TX freq. or your RX resonance... all true, all real and effects could be really heavy if some care e.g. on shielding aren't took.

Now about the lowering to floor of lab and increase... well... you have to know which kind of stuff there is in the floor layer... I mean some concrete e.g. panels are reinforced with iron-bars... some insulating stuff could be present (in some cases even al-foil were used in constructions)... there could be copper wires running over or below or in the floor itself...iron and other oxides and compounds could be present in the structure (that's really easy for concrete materials having aluminium and iron compounds traces but also other stuff like titanium oxides etc etc)

It's not a good test for nulling cause you probably don't know exactly what you actually have under your feet!

It's very difficault predicting what null voltage could be on soil(s)... you know that mutual inductance could change cause of external conditions.

From what I know the BIG companies do null using scopes like we do... but who knows what's the real reference voltage for null.

From my experience I've noticed much more stable working on soil with under 1mVpp null at lab.

I still think that the Qiaozhi's 100mVpp coil has something wrong inside.

Just my 5cents.

Best regards,
Max

[Max]

You are correct. Since the GEB sample pulse is positioned at the zero-crossing of the RX signal, then the output from the GEB analog switch (which is part of a sample & hold circuit) will be zero volts. Then only targets that produce a phase-shift (so that the pulse is not longer sampling at the zero-crossing) can cause a voltage to appear at the output of the gate. Neutral ground does not produce a phase-shift, only a decrease in amplitude. In this case the signal in the ground channel does not change.

The result is that 1mV, 15mV, 100mV ... it doesn't really matter that much how much residual voltage is there. The only disadvantages with a high residual voltage are worse discrimination for targets far from the coil, and more difficult (but not impossible) to ground balance.

I do not have a 20-turn pot on my detector, and ground balance is quite easy to achieve. Variation in ground conditions will always cause some falsing in a detector with manual ground balance, and fragments of ferrous brick can also cause some chatter. You should be able to eliminate this by increasing the level of discimination. By the way, the detector I'm using is my own design, but essentially it has the same classic 2-channel architecture used in many other analog detectors (with some refinements). The TX frequency is 10KHz and it uses the same capacitor values for the TX and RX coils on the Bandido. I've also checked this with an original Bandido and the results are the same. Maybe there is some quirk in the TGS design that causes this problem.

One thing you can be sure of is that Tesoro do not spend many hours trimming each coil to reduce the residual voltage. It just wouldn't make economic sense.

Hi,
yes I think too they don't spend much time on that...also cause they use standard housings...all the same...same turns for every model of coil they made... and just move the last half-turn maybe to get the "null".

I think that they null within 5mVpp tollerance... but then something could happen (relative movements of temporary fixings) during sealing process.

Just my thoughts.

Best regards,
Max

[Qiaozhi]

Maybe there is some quirk in the TGS design that causes this problem.

I've just been studying the TGSL schematic. It is the same double-differentiating architecture that I'm using. However, there is one interesting thing about the TGSL design that I think could make the TGSL easier to ground balance, which is even more of a mystery why you're having problems. When it's switched to All-Metal mode the DISC channel is still active, but instead of being sampled with the DISC sample pulse it is sampled by a slightly delayed version of the GEB sample pulse. This has the effect of creating a small dead zone that should make it easier to locate the GEB sample pulse over the zero-crossing, with the result that there is also some tolerance to changing ground conditions built into the design.

Here's an interesting thing you could try (see attached diagram).
Disconnect pin 1 of U106a, which will effectively disable the DISC channel, and let us know how this affects the ground balance.

[Max]

I've just been studying the TGSL schematic. It is the same double-differentiating architecture that I'm using. However, there is one interesting thing about the TGSL design that I think could make the TGSL easier to ground balance, which is even more of a mystery why you're having problems. When it's switched to All-Metal mode the DISC channel is still active, but instead of being sampled with the DISC sample pulse it is sampled by a slightly delayed version of the GEB sample pulse. This has the effect of creating a small dead zone that should make it easier to locate the GEB sample pulse over the zero-crossing, with the result that there is also some tolerance to changing ground conditions built into the design.

Here's an interesting thing you could try (see attached diagram).
Disconnect pin 1 of U106a, which will effectively disable the DISC channel, and let us know how this affects the ground balance.

Hi Qiaozhi,
yes right... it uses the 100k+15pF network that introduce a delay respect to GEB main signal (actually there is a phase shift cause of the respect main GEB signal... so the second gate is driven by a signal shifted by a particular angle that depends on components and frequency of triggering).

A similar thing you can see on one line of bandidoII schematic GEB+delayed GEB control 2 analog gates... though it's different from TGS that has a more basic approach.

The difference is that on BandidoII , in all-metal, you have a total disconnection of the 2 disc channels (non-ferrous/ferrous) and the delayed signal directly drive the "magnitude" output stage (integrator+threshold amplifier) in TGS the upper channel (used also in DISC) is actually as the "output stage"... cause TGS hasn't a separate just "magnitude" driven output stage... maybe cause it hasn't motion/non-motion all-metal and so don't need that 3rd route.

Best regards,
Max

[ivconic]

...

Good points from all of you. I enjoyed reading these. Thanks for suggestions Quiaozhi and Max!
I am in a hurry so wont be able to debate much here(less pain for you).

Today i made another coil. 255x137. Same turns,wire....etc.
Nulled to 0.001mV. Connected to TGSL and checked. Depth as usuall - great.
Disc as usuall - accurate.
But still bleeps ocassionaly... So i put smal iron washer in coils overlaping area. By moving it i achieved induction of 0.4mV (Not 4mV but 0.4mV on my multimeter)...and know what? All bleeps stopped!? Detection&Disc remains same!? What the heck is this?
At the end it will turn that your coils are not damaged...
I am starting to suspect this multimeter...!? How come that i so easy null coils to absoulte zero? Is it faking? Probably. I'll have to find another and compare. More and more i beleive that it should read 4mV not 0.4mV...?
Let's reconsider again: i switched it on 200mV range, and it usually reads cyphers like 0.009...0.012mV..How should i understand this?
Anyway, coil with washer works PERFECT for real. 2cm coin detect at 34cm distance with Sense pot at "6" and Disc pot at "3"..
I still have bleeps if Disc pot is settled less than "3"...?
Rising Sense pot to "10" (max) gives me extra 3cm on depth but also ocassional bleeps...not so often. I dont have problem with this. I have problem with Disc.pot. Can not understand why it bleeps when Disc is low?
As time goes by i suspect device itself more and more. Dont have any doubts on coils, any more. Coils are perfect...
Regards!

[Qiaozhi]

Good points from all of you. I enjoyed reading these. Thanks for suggestions Quiaozhi and Max!
I am in a hurry so wont be able to debate much here(less pain for you).

Today i made another coil. 255x137. Same turns,wire....etc.
Nulled to 0.001mV. Connected to TGSL and checked. Depth as usuall - great.
Disc as usuall - accurate.
But still bleeps ocassionaly... So i put smal iron washer in coils overlaping area. By moving it i achieved induction of 0.4mV (Not 4mV but 0.4mV on my multimeter)...and know what? All bleeps stopped!? Detection&Disc remains same!? What the heck is this?
At the end it will turn that your coils are not damaged...
I am starting to suspect this multimeter...!? How come that i so easy null coils to absoulte zero? Is it faking? Probably. I'll have to find another and compare. More and more i beleive that it should read 4mV not 0.4mV...?
Let's reconsider again: i switched it on 200mV range, and it usually reads cyphers like 0.009...0.012mV..How should i understand this?
Anyway, coil with washer works PERFECT for real. 2cm coin detect at 34cm distance with Sense pot at "6" and Disc pot at "3"..
I still have bleeps if Disc pot is settled less than "3"...?
Rising Sense pot to "10" (max) gives me extra 3cm on depth but also ocassional bleeps...not so often. I dont have problem with this. I have problem with Disc.pot. Can not understand why it bleeps when Disc is low?
As time goes by i suspect device itself more and more. Dont have any doubts on coils, any more. Coils are perfect...
Regards!

Would it be possible for you to disconnect pin 1 of U106A (as mentioned earlier) and tell me what effect this has on finding the ground balance point?

[ivconic]

I'll do that.
Are you awake still? For how long you will be here?
If you plan to stay a while (30minutes) i can do that now and later inform you...

P.S.
Damn! Now we need chat here...!

[Max]

Good points from all of you. I enjoyed reading these. Thanks for suggestions Quiaozhi and Max!
I am in a hurry so wont be able to debate much here(less pain for you).

Today i made another coil. 255x137. Same turns,wire....etc.
Nulled to 0.001mV. Connected to TGSL and checked. Depth as usuall - great.
Disc as usuall - accurate.
But still bleeps ocassionaly... So i put smal iron washer in coils overlaping area. By moving it i achieved induction of 0.4mV (Not 4mV but 0.4mV on my multimeter)...and know what? All bleeps stopped!? Detection&Disc remains same!? What the heck is this?
At the end it will turn that your coils are not damaged...
I am starting to suspect this multimeter...!? How come that i so easy null coils to absoulte zero? Is it faking? Probably. I'll have to find another and compare. More and more i beleive that it should read 4mV not 0.4mV...?
Let's reconsider again: i switched it on 200mV range, and it usually reads cyphers like 0.009...0.012mV..How should i understand this?
Anyway, coil with washer works PERFECT for real. 2cm coin detect at 34cm distance with Sense pot at "6" and Disc pot at "3"..
I still have bleeps if Disc pot is settled less than "3"...?
Rising Sense pot to "10" (max) gives me extra 3cm on depth but also ocassional bleeps...not so often. I dont have problem with this. I have problem with Disc.pot. Can not understand why it bleeps when Disc is low?
As time goes by i suspect device itself more and more. Dont have any doubts on coils, any more. Coils are perfect...
Regards!

Hi,
I suppose that when you put the iron washer inside middle of coils you get a shape variation of TX signal due to the magnetic losses and added histeresys(and eddy current flowing in) influence of the washer. If so... you'll end-up with a not perfect sinus also at RX and then when you measure it the multimeter just cannot read it well cause of distortion of the sinus... and you get 0 or near that... where I suppose you have greater voltage in the 10-15mVpp range.

About bleeping Qiaozhi is right about the two channel config of TGS... this actually could introduce problems when the 2 gate signals are separated by few delay due to the 100k-15pF network... expecially due to the differential comparator config you see before output stage.

I think that using an LM393AN , with less offset than standard 393N, could minimize that (and of course I have it on PCB)...but don't solve it totally.

If Qiaozhi found the real problem we could just add a section to the switch of mode... then disconnecting the pin1 when in All-metal position.

I cannot test now cause my PCB is so difficault to extract from case that I have to force it... and I need detector today ! Also I have reverse situation... disc at min, sens at max and no bleeping!

Best regards,
Max

[ivconic]

"...Disconnect pin 1 of U106a, which will effectively disable the DISC channel,
and let us know how this affects the ground balance..."
I did that. When switched ON it producing "beep,beep,beep,beep..." non-stop and
now way to calm it down, whatever i did.
"..I do not have a 20-turn pot on my detector, and ground balance is quite easy to achieve.."
So i replaced ordinary with multui-turn pot at GEB. Fine adjusted with it to produce
0.000vV. Zero - crossing you've explained above...It was easy (as you said) to adjust to
0 volts. Of course without any metal arround coil. When metal is presented near the coil
this voltage is not 0V any more but respecting signal strength it raises...
I made some measurements at analogue switches.
Rotating GEB trimm. gave me range from -7.66mV to +180mV at switch output (TR5).
Rotating Disc. pot gave me range from -130mV to -190mV at Fet output (TR4)...BUT!
Rotating Disc from one side to other, as approaching to middle point, voltage reversed
and somewhere at the midddle of pot it reads +330mV, further rotating lowered it to -190mV..
I checked everything again and again...still no solution!
Only way this TGSL to work very good without beep's is to Set Disc. at "3" and higher and
Sens to "6-7" in Disc mode. GEB trimmer is adjusted as described above. Adjusted like
this, TGSL is very deep,good discrimination...on the field it can produce very rare...but
very,very rare "beep's"...usually when coil hit some stone or bulky grass, harder...
In All metal mode i have to lower Sens at minimum to make it at least a bit useable..?
I do beleive that source of problem is somewhere after front end. Why?
OK, when switched ON it is silent. Than i provoke it to "sing" with some coin or simillar.
It wont stop as i move away that coin. So, i noticed if touch 3 lead cable (5cm long) from
pcb to Disc. pot...it stops with "beep's" at once??? When cable released it still remains
calm - no sound. Again when coin is moved over coil, it "beep's" without stoping?
If touch randomly other parts on pcb, sometimes i can stop it. But most significant is
that cable and Disc. pot. It stop with "beeping" always, when those are touched with finger?
Also rotating Disc pot has much more influence on detector behavior than anything else.
Rotating Sense pot doesnt affect anything noticeable. Also rotating GEB trimmer wont stop
once provoked "beeping" at all...??? Damn!
I have feeling that solution to this problem is right infront of my eyes...only i cant see it!