TESORO GOLDEN SABRE

[Molzar]

Hi,

Did some more testing, All aspects of descrimination, sense, and notch feature work properly. Coils are connected properly, still Rx always shift to the right when triggering on Tx. First gate of GEB (LM358, pin7, Max's Test point #9) rise when metal exposed to coil, like Qiaozhi said.

Problems are some erratic noises and only 18-20 cm depth on 2cm copper (or silver coin) Using LM308 or TL081 same. Only changes from schematic are 4.7ZD instead 4.3ZD, 3.9K instead 3.3K, and am using 10K instead 2.2K (or 33K) like Ivconic suggested, sound seems good. LF442 is TLC2262, FETs are TIS75s.

Haven't made many DD coil, but have made many PI coils. Am using 30 AWG enameled wire 100 and 105 turns wound on fixture (see photo), 0.8mm thick spiral wrap to bind coil, then .05mm thick aluminum foil for shield with 1 cm gap, then .2mm vinyl electrical tape to secure all. Null is ~8mV pp. Below are some photos. Sorry for the crappy images....

Any suggestions?

Many Thanks for everyones help, this has been a good (interesting) project!

Molzar

[nelson]

Yesterday i null with the scope very easy the same coil, but know i need to know how to do fine tuning of the RX coil. Should i use caps parallel to each lead of RX coil? If so wich value should i have to use?.
This questions is because i had noted that sensitivity of my TGS is to poor, a 27 mm coppper coin is just detected at 18 centimeters.
TX coil is working at 14.6 Khz.
Any help, please write about.
Thanks
Nelson

Hi,
use Ivconic's data:

TX= 100turns
RX= 105turns

wire 30AWG (0.25mm bare diameter, without varnish); you can use 0.30mm but require change a bit turns.

Coil diameter will be around 27cm DD type.

Null at less than 15mV peak-peak

Resistance is for each coil... around 20ohm and you have match tx frequency of 14.5 - 14.7Khz.

Kind regards,
Max

[Max]

Essentially this is correct. This is the way the older T/R detectors manage to discriminate ferrous from non-ferrous, simply by an amplitude change. Only the good stuff causes the amplitude to increase.


I have also tested other Tesoro concentric coils, and they all have the same phase-shift to the left.


The Gifford patent is confusing because the reference point for the phase measurements is offset by 90 degrees.


It is possible to construct your own coil with different characteristics than the 9x8 concentric, and with some adjustments it can be made to work. However, these configurations are not optimal.


Although the basic mechanism for discrimination relies on a change in amplitude at the output of the DISC channel, it is also affected by phase changes. By adjusting the DISC control you can alter the sample point on the received waveform in order to reject higher conductivity targets. It is not only Tesoro that use this method of discrimination. This is the same technique used by Whites, Fisher, Viking, C-Scope, etc., in their analog detectors. The digital detectors that have some sort of VDI indication, are actually measuring the phase-shift.

It's not really a puzzle .... just a bit confusing.

Hi,
thanks, now I understand it better: is more complex than what I expect from Tesoro's VLFs disc section but sure, it works pretty good.

I don't know if what I made about DD is optimal but I get really good results with them and disc is perfect. I think Ivconic's recipe for the large DD coil is perfect for it, I have no dubt about that cause made different and not a single one will beat that numbers on TGS within same diameter and shape.

The fact phase shift is both sides with DD means really few if detector actually rely on disc channel amplitude rise or fall to say about target composition.

I think the real trick is made on amplitude changes... if the coil will give a rise with non-ferrous and a drop with ferrous it will works good on TGS, with minor impact of TX/RX phase shift when no target, just need something 200° out of phase to avoid troubles with sync.

The interesting thing is that , a TGS will not actually compute the phase shift but just comparing amplitudes at both GEB-disc channels. This way a very essential disc indicator could be realized using an e.g. differential amplifier connected with e.g. some bicolor led... very easy stuff and reliable also.

No need to compute phase shift, no need of accurate phase meter there... just some amplifier and maybe an hold circuit + analog instrument is enough to understand what kind of metal is detected. Old way...

Kind regards,
Max

[Qiaozhi]

Hi Qiaozhi,
let me ask same question to you:

what about disc in Tesoro's... it's made just by amplitude variations at RX signal then ?

Essentially this is correct. This is the way the older T/R detectors manage to discriminate ferrous from non-ferrous, simply by an amplitude change. Only the good stuff causes the amplitude to increase.

I noticed that phase shift is always one way with 9x8'' original coil... and this fact is really interesting cause disc works perfect on TGS/TGSL like Ivconic stated!

I have also tested other Tesoro concentric coils, and they all have the same phase-shift to the left.

Now the problem is... that I cannot recognize the stuff that is in the Gifford's patent with behaviour of device: I have no left or right phase shift related to target composition, like expected, but just amplitude variations(rise for non-ferrous and drop for ferrous) and always same left phase shift there, with both ferrous and non-ferrous.

The Gifford patent is confusing because the reference point for the phase measurements is offset by 90 degrees.

Also, like you described the GEB signal always goes up with both kind and of course ferrite material.

The strange if that on some handmade DD I have I got different stuff, and disc works also perfect ! I got left and right shifts in that coils, but always the same amplitude rise/fall behaviour.

It is possible to construct your own coil with different characteristics than the 9x8 concentric, and with some adjustments it can be made to work. However, these configurations are not optimal.

That's why, I think, disc is mostly related to amplitude variations at RX, not phase in Tesoro's designs that then give alway-rise on GEB channel and rise/fall at disc channel depending on material.

The effect is the same at the end... but does not rely on phase shift between RX signal and TX signal as one could expect from reading the patents.

It's a puzzle !

Kind regards,
Max

Although the basic mechanism for discrimination relies on a change in amplitude at the output of the DISC channel, it is also affected by phase changes. By adjusting the DISC control you can alter the sample point on the received waveform in order to reject higher conductivity targets. It is not only Tesoro that use this method of discrimination. This is the same technique used by Whites, Fisher, Viking, C-Scope, etc., in their analog detectors. The digital detectors that have some sort of VDI indication, are actually measuring the phase-shift.

It's not really a puzzle .... just a bit confusing.

[Max]

This might be true. I think it is ok for the phase-shift to be to the right, but in that case you need to swap over the RX leads. The important thing is that the signal at the output of the sample gate in the GEB channel must increase in amplitude when a metal target passes next to the coil. If it decreases, then swap the RX leads. I don't remember if the DD coil has the same characteristics as a concentric - need to recheck this.

Hi Qiaozhi,
let me ask same question to you:

what about disc in Tesoro's... it's made just by amplitude variations at RX signal then ?

I noticed that phase shift is always one way with 9x8'' original coil... and this fact is really interesting cause disc works perfect on TGS/TGSL like Ivconic stated!

Now the problem is... that I cannot recognize the stuff that is in the Gifford's patent with behaviour of device: I have no left or right phase shift related to target composition, like expected, but just amplitude variations(rise for non-ferrous and drop for ferrous) and always same left phase shift there, with both ferrous and non-ferrous.

Also, like you described the GEB signal always goes up with both kind and of course ferrite material.

The strange if that on some handmade DD I have I got different stuff, and disc works also perfect ! I got left and right shifts in that coils, but always the same amplitude rise/fall behaviour.

That's why, I think, disc is mostly related to amplitude variations at RX, not phase in Tesoro's designs that then give alway-rise on GEB channel and rise/fall at disc channel depending on material.

The effect is the same at the end... but does not rely on phase shift between RX signal and TX signal as one could expect from reading the patents.

It's a puzzle !

Kind regards,
Max

[Qiaozhi]

Hi,
I'm not sure... but think Qiaozhi report is valid only for concentric coplanar coils, expecially original tesoro's ones.

I have a 9x8'' spider from tesoro and on my TGS I see RX signal go to the left not to the right, as Qiaozhi stated.

Probably also you have reversed rx leads, try to swap them and let us know if it goes to the left then.

Kind regards,
Max

This might be true. I think it is ok for the phase-shift to be to the right, but in that case you need to swap over the RX leads. The important thing is that the signal at the output of the sample gate in the GEB channel must increase in amplitude when a metal target passes next to the coil. If it decreases, then swap the RX leads. I don't remember if the DD coil has the same characteristics as a concentric - need to recheck this.

[ivconic]

Hi,
no problems... just I asked you about what do you think of disc in Tesoro's designs.

Qiaozhi pointed right way when said that original coils give always left shift on RX signal, no matter if target is ferrous or non-ferrous.

Also, non-ferrous give a rise in amplitude at RX coil and ferrous give instead a drop.

The question was/were:

What do you think of how Tesoro's disc works if phase shift is always one way ? Is it related instead to amplitude rise/fall only ?

Cause I think the important information there is about amplitude if phase shifts are always same side...

Kind regards,
Max

Actually i noticed pretty unsignificant phase movements to both sides related to type of metal. This is mostly due fact that i dont have good scope. My is old,obsolete and totally unaccurate. Yet,with same scope i noticed large amplitude jumps on various metals. Most significant is huge amplitude jump on ferrite rod - but without any sound, which leads me to conclusion that GEB/DISC stage works almost perfect at TGSl. Same perfection i experienced so may times on real field,under real condition. That's why i am pushing this project as most suitable for to be hand made.Really easy to achieve excellent performances.
Unlike at other principles, the way how GEB/DISC is soluted at TGS (and few other Tesoros) turns to be most efficient when compared to most of other analogue designs.
I've done many copies of White's Classic III so far. At that specific design GEB suffering from to many lacks which directly influencing further DISC stage. Fer instance, although CL3 do have extra resistance switch to rise "imunity" on hot rocks and black sand, still it is suffering much from those. Other hand, TGSL does not "see" hot rock even big like a house! Splendid!
On same terrains where i had much of hot rock signals and therefore much problems....on those very same terrains i do not have problems at all with TGSL.
This is just an example which will help you to understand differences in this approach by Tesoro.

[Max]

Sorry Max!
What was the question?
Last days i am very rare near my pc. Usually do check this forum pretty skim..
Come again.

Hi,
no problems... just I asked you about what do you think of disc in Tesoro's designs.

Qiaozhi pointed right way when said that original coils give always left shift on RX signal, no matter if target is ferrous or non-ferrous.

Also, non-ferrous give a rise in amplitude at RX coil and ferrous give instead a drop.

The question was/were:

What do you think of how Tesoro's disc works if phase shift is always one way ? Is it related instead to amplitude rise/fall only ?

Cause I think the important information there is about amplitude if phase shifts are always same side...

Kind regards,
Max

[ivconic]

Sorry Max!
What was the question?
Last days i am very rare near my pc. Usually do check this forum pretty skim..
Come again.

[Max]

Hi Max,

Yes,I thought of that but the way coils are connected they give correct looking traces at all test points you outlined previously in posts.

The coils are DD 140 x 255 mm, 30 gauge enamled wire

Tx = 100 turns, 23.0 ohms, 5.78 mH, Q= 1.65
Rx = 105 turns, 24.1 ohms, 6.18 mH, Q= 1.67

Tx Freq =14.1 KHz

Nulls down to about 8 mV using 1K res / .015uF cap setup. Measure about 850 mV at the RX test point on the pcb.

Do your DD homebrew coils shift to the left also?

Left shift should be in All Metal and Discrimination mode, correct?

Molzar

Hi,
yes the shift is to the left on 9x8'' spider both ways, disc and all-metal.

Now I don't remember about DD, must check again but I remember that DD behave different... I remember that on my DDs I get left and right shifts depending on composition of target.

If remember well I get left shift with non-ferrous like copper and right shift with soft iron, or the reverse.

In the 9x8'' concentric coplanar I get instead like Qiaozhi said, always left: just amplitude rise with non-ferrous and drop with ferrous.

That's why I asked Ivconic about but didn't reply me...maybe didn't see my message: I think that in 9x8'' and other concentric-coplanar from Tesoro (originals) the only information about disc came from amplitude variation.

But seems nobody knows for sure.

Kind regards,
Max

[Molzar]

Phase shift

Hi Max,

Yes,I thought of that but the way coils are connected they give correct looking traces at all test points you outlined previously in posts.

The coils are DD 140 x 255 mm, 30 gauge enamled wire

Tx = 100 turns, 23.0 ohms, 5.78 mH, Q= 1.65
Rx = 105 turns, 24.1 ohms, 6.18 mH, Q= 1.67

Tx Freq =14.1 KHz

Nulls down to about 8 mV using 1K res / .015uF cap setup. Measure about 850 mV at the RX test point on the pcb.

Do your DD homebrew coils shift to the left also?

Left shift should be in All Metal and Discrimination mode, correct?

Molzar

[zzy]

Molzar

Hi,
I'm not sure... but think Qiaozhi report is valid only for concentric coplanar coils, expecially original tesoro's ones.

I have a 9x8'' spider from tesoro and on my TGS I see RX signal go to the left not to the right, as Qiaozhi stated.

Probably also you have reversed rx leads, try to swap them and let us know if it goes to the left then.

Kind regards,
Max

Hi
My TGS is just like Molzar's. MAXreversed rx leads,no change,still RX signal go to the right.mabe DD coil is not fit to TGS.

[erolunall]

Hello

good quality tgsl pictures at links

http://www.postimage.org/image.php?v=aV1OM0B9

http://www.postimage.org/image.php?v=aV1OLRCA
http://www.postimage.org/image.php?v=PqMil19

My friend said it is working good.

Regards
Erol

[Max]

Hello,

Recently completed TGS and am now trying to tune it properly.

I also get Rx phase shift to the right when triggering on the Tx. I tried Qiaozhi suggestion of under / over nulled coil. This changes the amplitude charateristic (goes higher only (over nulled?), goes lower than higher (undernulled?) but the Rx always moves to the right vs the Tx.

The above happens when metal is in the overlapped area of the DD.

When the metal is in the other area of the coils it does shift somewhat to the left.

What am I doing wrong?

Molzar

Hi,
I'm not sure... but think Qiaozhi report is valid only for concentric coplanar coils, expecially original tesoro's ones.

I have a 9x8'' spider from tesoro and on my TGS I see RX signal go to the left not to the right, as Qiaozhi stated.

Probably also you have reversed rx leads, try to swap them and let us know if it goes to the left then.

Kind regards,
Max

[Max]

Hi!
I fineshed my TGS.Now I need only good coil.Please what is the best coil type and how meny turns i must made.

Thanks and sorry for my English

Hi,
use Ivconic's data:

TX= 100turns
RX= 105turns

wire 30AWG (0.25mm bare diameter, without varnish); you can use 0.30mm but require change a bit turns.

Coil diameter will be around 27cm DD type.

Null at less than 15mV peak-peak

Resistance is for each coil... around 20ohm and you have match tx frequency of 14.5 - 14.7Khz.

Kind regards,
Max