TESORO GOLDEN SABRE

[Qiaozhi]

Thanks Qiaozhi.. It works, and best of all it's free!

Exactly! It even reads the latest docx files.
Who needs Microsoft Office Suite?

[08llyj]

cable eduardo1979

Good morning
I am new and i have invested in a tgsl eduardo1979, but I don't know how to link cables k1.2.3 on the pot and which value for this one
Same things for p10.20.30 and for the sensibilitée .
Thank you for your help.

[eduardo1979]

Tgsl Edu conexion

[08llyj]

cables

thx a lot for this good jod eduardo1979

[Dennis the Mennis]

Hi DtM! You'll get there because you have the right approach!

On the general topic:

Even though I've said my piece about the null phase, let's review what we mean.

1. When someone says 20 degrees, what signal is being measured? Rx coil leads, or output of LF353? Is the Rx coil connected to the PCB or disconnected (I assume connected).

2. What is the null signal phase referenced to? (The Tx signal I presume).

3. What does 20 deg mean, leading, or lagging? How do we measure lead or lag?

Diagrams would be useful to make sure we're meaning the same thing here.


-SB

1. I think when the 20 degrees phase shift are mentioned the most would refer to the output of the LF353 vs the Tx signal .

You've a good point here that all these terms can cause confusion or are not well understood.

2. I think that the most are 'suffering' a leading phase shift were the Tx is the reference and triggers the scope just like these video's I've posted recently:

http://www.geotech1.com/forums/showp...&postcount=348

http://youtu.be/3hY4s6_cKw4?hd=1
http://youtu.be/zZTDKBd3Gn0?hd=1
http://youtu.be/iJKx8JJ1A8M?hd=1
http://youtu.be/N7yrp8l_fSU?hd=1

I still can't understand and just don't know why many of us can make a coil with the 'prefered' + 20 degrees and also many of us , including myself , make coils with a bigger ( >> 20 ) phase shift just like Habitbraker just posted.

Allthough we ( Habitbraker and me ) seem to get a good detection .

Perhaps it is less important as I thought ....

What I've tried to point out in the post with the video clips is that when I use unshielded coils with the correct parameters it reacts pretty much ideal (?) : correct phase shift , low residual voltage

BUT

When these same coils are shielded there is such a great difference ...

Of course there is magnetic and capacitive coupling but what is the secret overhere ?

I've used ordinary kitchenfoil not to thick wrapped around the coil and with bare wire wrapped around the shield , just like described in these threads

When I used Mylar ( at least I think it was , stripped down a VGA cable ) just like Don DFBowers did I had better 'results' .

I'm wondering right now if this due to the Mylar or the thicker isolation between the coil and shield


kind regards ,

Dennis the Mennis

[habitbraker]

hello!
Yes, I also was refering to signal from output of LF353 (pin7) and TX (Collector of TR1)
I can get it working with both positive and negative phase and even that Qiaozhi said ono of them should give better results, I dont see them. Sampling places just changes polarity (GB from pos to neg going slope and disc at pos T/2 changes to neg to pos for GB and neg T/2 for Disc.) In both cases I can reject ferrite at middle of GB pot and Disc al foil at same angle of disc pot.

But some phase shift is needed because when RX is in phase if TX, there are problems.

One interesting thing I exp. :
I have made two pairs of coils. First pair(bad) was shielded with thick al foil and after doing that I, my null became 1.5Vpp min. Second pair(good) I shielded with thin kichen foil - i could achieve very small null voltage. Both worked the same.
I choosed the second pair.
Then I decided to change cable (usb I was using). After that my small null became big and phase was positive only. Good became bad too... Very big diffference just changing cable!!
How i solved it? I took RX coil from First pair(thick shield) and my RX became perfect - phase shift from +20 to -20 (about) and null as low as 200mV(at p7)
I guess that many little different coils must be made and best combination choosed (RX,TX, shield, cable).
Other thing - shield (thick or thin) makes difference, but this difference can be fixed(overcamed) with changing other variables.

[simonbaker]

Those are interesting observations by DtM and Habitbraker.


Habitbraker -- what did you mean by "good became bad too..."? Were you talking about actual air-depth detection, or observed phase of null?

There is one electronic consequence of a seriously "wrong" null phase... if you have a large null signal and a phase which makes the voltages on capacitors C12 and/or C15 go negative, you can forward-bias the JFets, which screws up the Synchronous Detector operation and can certainly mess up your detection. So watch for that condition.

It makes sense to me that unshielded coils exhibit a more "ideal" null phase shift. The shield certainly will add some kind of coupling -- my question is, how much of that coupling is "non-magnetic" (not affected by ground ferrite) vs. magnetic.

(side note to self: Something I haven't really considered is: can the ground modulate the "non-magnetic" coupling as well, perhaps through capacitive effects, and to what degree?)

(Another issue I need to think about -- how the null signal phase is affected by the "balance" of the magnetic fields between the coils. Ideally, the balance shouldn't affect the phase, just the magnitude of the pure magnetically coupled signal, since it should just affect the net flux in one direction or another. But is there more to it...?)

I would ask you to do the "ferrite blob" test:

Put a large blob of ferrite in the overlap between your coils. Observe the phase (zero crossings) of the (now much larger) null signal. Is the phase now more similar to the null phase with unshielded coils???

-SB

[Dennis the Mennis]

I would ask you to do the "ferrite blob" test:

Put a large blob of ferrite in the overlap between your coils. Observe the phase (zero crossings) of the (now much larger) null signal. Is the phase now more similar to the null phase with unshielded coils???

-SB

What should be considered as 'a large blob of ferrite' ?
I've got two ferrite rods of 10 cm , is this enough blob ?

kind regards

DtM

[mikebg]

It makes sense to me that unshielded coils exhibit a more "ideal" null phase shift. The shield certainly will add some kind of coupling -- my question is, how much of that coupling is "non-magnetic" (not affected by ground ferrite) vs. magnetic.
-SB

Simon, the shield generates an eddy current signal.
Is the following your meaning of term "blob"?

[salim]

The resistance of 22 ohms in parallel with the 220uF capacitor, it was a mistake of mine and has been corrected. I posted the correct PCB in a previous post. The audio I've used is the audio of Eldorado and I like more.

thanks can you post your typon file to make the project br!

[fmnotes]

Ok...metaldetector107;
here is what i want you to do!

Disconnect ONLY RX wires from your detector and connect those on digital multimeter. Switch multimeter to AC~200mV range. Switch ON detector. And measure residual voltage. Than post here.
See on posted sketch bellow, it is how should be done.
Post what you measured here and we will see what to do... OK?

HELLO.
I WILL REQUEST YOU, IT HELPED WITH.
I HAVE MADE THIS MEASUREMENT,
THE CLUE IN THE DIGITAL VOLTMETER THEY IS 4VOLT.
THEY IS WELL?
WHAT PUZZLES ME THEY IS, THE CLUE THEY IS 4VOLT AND WHEN I CLOSE INSTRUMENT (TGS) THAT IS TO SAY WHEN THEY IS EXCEPT OPERATION, THE MEASUREMENT AGAIN THEY IS 4 VOLT.
I REQUEST YOU YOU CAN MY EXPLANATIONS WHAT BECOMES.

I THANK

[simonbaker]

What should be considered as 'a large blob of ferrite' ?
I've got two ferrite rods of 10 cm , is this enough blob ?

kind regards

DtM

Hi DtM!

I think those should do it (although they sound long and skinny rather than "blobby" - but may work if positioned within the overlap) -- give it a try! Look at the zero crossings, and maybe also note the center of the peak signal, to see if the phase shifts around. Let us know what you find. Photos would be great.

Regards,

-SB

[simonbaker]

Simon, the shield generates an eddy current signal.
Is the following your meaning of term "blob"?

I think the one with honey sounds rather nice...

I guess a question is: how much is that eddy current field modulated by ferrite in the ground compared to the basic magnetic field. This would relate to whether certain shielding can cause some null signal phase problems which interfere with GB pot settings, and whether we need to avoid some kinds of shields and prefer others.

This relates to the elusive "20 deg" null phase shift that many pursue with frustration. But first we need to establish:

1. Has anyone made a good detector with a coil that does not have a 20 deg null phase?

2. Has anyone made a bad detector with a 20 deg null phase?

There may be different reasons a coil does not have a 20 deg null phase -- perhaps some may be detrimental, some not.
It may be we need to look at cables more closely -- capacitive coupling can change the null signal phase, but perhaps not a problem because not affected by ferrite.

The ferrite blob test is one experiment to look into this.

-SB

[simonbaker]

HELLO.
I WILL REQUEST YOU, IT HELPED WITH.
I HAVE MADE THIS MEASUREMENT,
THE CLUE IN THE DIGITAL VOLTMETER THEY IS 4VOLT.
THEY IS WELL?
WHAT PUZZLES ME THEY IS, THE CLUE THEY IS 4VOLT AND WHEN I CLOSE INSTRUMENT (TGS) THAT IS TO SAY WHEN THEY IS EXCEPT OPERATION, THE MEASUREMENT AGAIN THEY IS 4 VOLT.
I REQUEST YOU YOU CAN MY EXPLANATIONS WHAT BECOMES.

I THANK

Are you saying that you measure 4 volts AC at your RX coil when your TGS is turned on and also when it is turned off?

-SB

[fmnotes]

Are you saying that you measure 4 volts AC at your RX coil when your TGS is turned on and also when it is turned off?

-SB

HELLO AND I THANK FOR YOUR CORRESPONDENCE IN MY QUESTION THAT I PLACED

YES PRECISELY.

THEY IS PHYSIOLOGIC? YES OR NO?