TESORO GOLDEN SABRE

[ivconic]

Heck! I forgot to attach photo today!?
Here it is;

[ivconic]

Power drain is actually not an issue, especially at TGS/TGSL.
With last audio mod (2xBC547+BD140) it bairly drains 22mA up to 30mA in some cases. Conversion from 12 to 8 volts also is not an issue.
On TGSL, Delta Pulse and few other detectors, i am always using small accu. 12V/1.3Ah. So it lasts for days on terrains outdoor. Last time i checked it, it was my 5-day expedition, without charging i worked with TGSL approx. 10 hours per day, 5 days... So..it is not an issue at all.

Refering 7660...it is cute, but if you need more power than 78S40 is better solution. It costs
some 40 eurocents in local shops.

[simonbaker]

I think that is a Great Idea , and also run audio on a separate supply voltage . Speaking of voltage , can anyone tell me why engineers / Technicians use the ICL7660 on circuit designs ?? I would like to see an "Equivelent Circuit" of voltage conversion....................Regards.......Eugene

That is a neat chip, especially since you can drive it from an external oscillator, which we want to avoid unsynchronized signals floating around. The limitation seems to be it doesn't provide too much power, especially at high efficiency. But I'm interested in the idea of using power conversion somehow to use more convenient batteries and waste less power. TGSL wastes a lot of power going from 12V to 8V.

-SB

[ivconic]

"..But we better do not discuss this more here.."

[Qiaozhi]

Scientists lack imagination *

Fred.

* free provocation....muuahaha!!!.

Not that sort of example!

But to answer your provocation ... in reality I think it's quite the reverse. Scientists have too much imagination. Parallel universes, quantum teleportation, worm holes, time travel, to mention a few.
However, we are now going off topic. There's some danger of getting caught in the dark side.

[Fred]

For example???

Scientists lack imagination *

Fred.

* free provocation....muuahaha!!!.

[Qiaozhi]

Also "basic physics.." turned to be disproved by real practice many times so far.

For example???

[ivconic]

Unfortunately you are up against some basic physics here. The way the Whites (or any other digital detector) displays "accurate" VDI numbers, is by having a lookup table in ROM of various phase angles measured for specific targets at various depths. By monitoring the amplitude and cross-referencing this with the lookup table, it is possible to "guess" the identity of the target. This is only really accurate when the target is relatively close to the coil, or when performed in an air test. The ground causes lots of distortion in the RX signal, which makes the target id inaccurate.
There is no easy way around this problem with an analog detector.

"..Unfortunately you are up against some basic physics here..."

Ha,ha,ha! I know that already, very good.
Don't tell ME that, tell that to ALL metal detector manufacturers as remark on their wild advertisments!
When i said "..smart done.." - i reffered that to smart White's strategy to elegantly solve disc inaccuracy above some depth limits. Good done - audio is further produced, BUT VDI do not respond above some limits. So operater is not fooled with their detector, as with majority of other models from other manufacturers.
I hope this is now more understandable?

Reffering this issue at "analogue" detectors...yes, i do seriously think there is certain way to overcome it. But i will not discuss that now. Time will come and we will discuss it in future.
Do not plead on some " basic physics.." here. Problem is tied up on more than just "basic...". Also "basic physics.." turned to be disproved by real practice many times so far. But we better do not discss this more here.
Regards!

[Fred]

Hi Eugene,
The 7660 is a specialised circuit, it need few external components and works well, it´s like with the 7805 for voltage regulation but oher solutions are possible....:this one is said to deliver up to 40ma .

[Eugene52]

TESORO GOLDEN SABRE

I think that is a Great Idea , and also run audio on a separate supply voltage . Speaking of voltage , can anyone tell me why engineers / Technicians use the ICL7660 on circuit designs ?? I would like to see an "Equivelent Circuit" of voltage conversion....................Regards.......Eugene

[ivconic]

Yes i was thinking to try like that. More power there would do some good i presume. I will try in next TGSL.

[simonbaker]

Indeed, and real goal would be to achieve less phase shifts, influenced by depth rises. Same old problem; some medium sized iron at greater depths will be detected as "coloured" by many detectors not only TGSL in the soil especially.
TGSL has weak TX. Is it possiblle to overcome phase issue with stronger output? At least to expand accuracy at a bit greater depths... I think it is possiblle. Stronger output will expand accuracy and phase would be slightly shifted at greather depths than it is now. But stronger TX will cause many other problems, stabillity issue at first place...
Would be good to analyze disc circuitry at White's Eagle, XLT,MXT,M6 and DFX serie. Those are accurate up to some point and VDI shows real numbers, but after some point those do not showing any number, just undefined audio on deep detections.... So problem is not solved at those models but also those do not "claim" deep items as "coloured" or iron. Just producing audio at detection of those deep items. Smart done.

Did you try running oscillator straight from battery, any difference in depth and discrimination depth?

-SB

[simonbaker]

You need to do the actual experiment, and not rely just on the simulation.

You're right!

-SB

[Qiaozhi]

Not really IMHO. The phase shift of the combined signal (null residue + target) is dependent on depth. That's because the null residue dominates for weak (deep) targets, and the target signal dominates for strong (shallow) targets.

You need to do the actual experiment, and not rely just on the simulation.

[simonbaker]

Simply monitor the output signal from the pre-amp relative to the TX signal. You will need a 2-channel scope to do this. Trigger on the scope channel that is connected to the TX, and watch the RX signal shift as you bring a target close to the coil. It is then easy to see that the phase-shift of the target is dependent on depth.

Not really IMHO. The phase shift of the combined signal (null residue + target) is dependent on depth. That's because the null residue dominates for weak (deep) targets, and the target signal dominates for strong (shallow) targets.

But the absolute phase of the target part of the signal is not dependent on depth. The TGSL responds only to the target signal, so the design should discriminate independent of depth (theoretically).

The reason is the bandpass filters. They remove the effect of the null signal. Therefore, theoretically, the exact null value is not important for the TGSL design.

At least that is what the math indicates. I don't see any other explanation. The received signal Vrx = Vnull + Vtarget. The synchronous detector converts each part of the signal into a DC (or very low frequency) voltage. Because Vnull is a steady signal, it becomes a constant voltage which is blocked by the bandpass filter. The Vtarget becomes a very low frequency pulse, which passes through the bandpass filters.

The math indicates that Vnull does not affect Vtarget, they are independent. It doesn't matter what the combined signal Vrx looks like. Even if you can't see Vtarget, it is there. Vnull will not go through the bandpass filter, only Vtarget will. Even if Vtarget is very small, the discrimination should work the same.

If in reality the discrimination does change with depth, it is because of some reason we are not talking about. I would guess noise is blurring the phase of the target signal or some other effect. I don't believe it is directly due to the relative size of the null residue and the target signal. That would be true if zero crossings were use to detect phase, but the synchronous detector works differently.

There probably is a good reason to set the null voltage precisely, but the basic design and equations don't show it. The equations say don't worry too much about the null. However, because the LM358 U103 is directly coupled to the output of the synchronous detector, too large a null residue would saturate it or overload it -- that is a real reason to keep the null residue quite small. The amount of coupling with the TX coil also has complex effects because the TX coil is also a receiver for noise and target, and also can couple a load to the RX preamp input.

That's how I see it so far, I enjoy the discussion and ideas of everyone, just trying to understand it better and better.

Regards,

-SB