technical matter

[getsa]

How it can be solved / improved problem seen in all dual-channel detectors, namely:
When discrimination is zero strokes work flawlessly in any angle, and depth, achieved in the air; increasing the discrimination began to decrease depth, sound becomes shorter, the "target" begins to detect only part of the strokes ...generally-almost every one knows what I mean…!
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[Skippy]

Modern machines that use a microprocessor to determine the discrimination/ target ID do not suffer this problem. As an example, the Fisher F75 has an all metal mode which still gives target ID values. The microprocessor measures the R and X channels and calculates phase angle with mathematics (division).Acheiving this with analog circuitry introduces compromises.

[ivconic]

Modern machines that use a microprocessor to determine the discrimination/ target ID do not suffer this problem. As an example, the Fisher F75 has an all metal mode which still gives target ID values. The microprocessor measures the R and X channels and calculates phase angle with mathematics (division).Acheiving this with analog circuitry introduces compromises.

Ain't that a truth!
Plain truth!
I am in a middle of process in solving similar issue.
Compromises, compromises .... truth!

[holyuser]

The microprocessor measures the R and X channels and calculates phase angle with mathematics (division).

http://youtu.be/oSA9ywMrZWc

http://www.md4u.ru/forum/viewtopic.p...edb50a6#p93948

[ivconic]

http://youtu.be/oSA9ywMrZWc

http://www.md4u.ru/forum/viewtopic.p...edb50a6#p93948

That's nice!
I made Cyclop Eye. It is working. Not so deep. But "bar drawer" is working very nice!
This new one is more "universal" and can be included much easier in other designs!
Cheers!

[Qiaozhi]

http://youtu.be/oSA9ywMrZWc

http://www.md4u.ru/forum/viewtopic.p...edb50a6#p93948

Very nice!
Is this your design?

[mikebg]

Very nice!
Is this your design?

The majority of Bulgarian designers of metal detectors are anonymous (for fear of customers anger :-).
By the way, I noticed a difference in reporting VDI of Bulgarian coin 5 cents.
In one video, the coin makes VDI = +13, and in other video showing VDI = 20. The reason is that in the first case the coin is nonferrous (minted in 1999), while the latter is ferrous (minted in 2000).

Болшинството български дизайнери на метал детектори са анонимни (защото се страхуват от гнeва на клиентите :-).
Между впрочем, аз забелязах разлика в отчитането VDI на български монети 5 стотинки.
В единия видеоклип монетата дава VDI=+13, а в другия видеоклип показва VDI=20. Причината е, че в първия случай монетата е немагнитна (сечена е през 1999г), а във втория случай е магнитна (сечена е през 2000).

[Carl-NC]

How it can be solved / improved problem seen in all dual-channel detectors, namely:
When discrimination is zero strokes work flawlessly in any angle, and depth, achieved in the air; increasing the discrimination began to decrease depth, sound becomes shorter, the "target" begins to detect only part of the strokes ...generally-almost every one knows what I mean…!

In disc mode the phase response is the "gate" for the audio response. But the target phase response is not instantaneous, it ramps up to a peak value as the coil sweeps over the target. The audio doesn't kick in until the phase exceeds the threshold set by the disc pot; the higher you set the disc threshold, the shorter the audio response becomes. Also, the peak target phase depends on signal strength, so exceeding the disc phase threshold gets harder if the signal is weaker. Therefore, increasing the disc threshold reduces effective depth.

This is why I prefer detectors with "mixed-mode" audio.

[holyuser]

The majority of Bulgarian designers of metal detectors are anonymous (for fear of customers anger :-).
By the way, I noticed a difference in reporting VDI of Bulgarian coin 5 cents.
In one video, the coin makes VDI = +13, and in other video showing VDI = 20. The reason is that in the first case the coin is nonferrous (minted in 1999), while the latter is ferrous (minted in 2000).

Болшинството български дизайнери на метал детектори са анонимни (защото се страхуват от гнeва на клиентите :-).
Между впрочем, аз забелязах разлика в отчитането VDI на български монети 5 стотинки.
В единия видеоклип монетата дава VDI=+13, а в другия видеоклип показва VDI=20. Причината е, че в първия случай монетата е немагнитна (сечена е през 1999г), а във втория случай е магнитна (сечена е през 2000).

You have mistake. In both cases the coin is minted in 1999.
The reazon of the difference is a correction in the shematic - RV2 is added to "shift" the foil indication arround zero degrees.
By the way, i do not fear of the customers anger, because I do not have customers.
Building metaldetectors is my hobby, not more.

[Funfinder]

Hi MikeBG and holyuser,

I am your very angry customer of bulgarian MD! No, don't believe it, I'm just joking!

The Blisstool LTC64 made in BG works really good even for very small objects
and has not much difference in depth if disc is on or off.
It uses a special method where the disc is connected with depth so it's possible
to disc very shallow rusty nails while deep rusty stuff still gives clear signal.


Getting better depth without disc principally has to do with the ground balance.
If it's set to zero or low mineralized makes the detector automatically tuned to
best sensitivity at around iron level.

Logically seen noble metals should give much better eddy current detection because
they have much better conductivity. But iron has better permeability. However
MDs are no magnetometers so it must have something to do with ground settings.

The Jeohunter seems to confirm this fact because when I set the GB to plus 201,
the upper maximum, silver coins are much better detectable, but iron not so good
as before at 0 ground balance.

[getsa]

Dear "funfinder"!,-because this method is a special "secret" kept by the engineer who designed blistol-detectors, this does not answer the question I'm looking at this forum. I even think that you advertise these detectors. This is not what I'm looking for here. I rather liked the answer to "Carl-NC"-It sounds reasonable and logical. Carl-What do you mean when you talk about detectors with "mixed-mode" audio???

[Carl-NC]

Carl-What do you mean when you talk about detectors with "mixed-mode" audio???

Both the all-metal and the disc audio are presented at the same time. Therefore, if the disc audio doesn't respond -- either because the target was too deep to exceed the disc threshold, or because the target was correctly rejected -- you will still hear the all-metal response of the target.

Nautilus detectors have this feature, and a few models from White's.

[getsa]

Thanks Carl!

[Funfinder]

Dear "funfinder"!,-because this method is a special "secret" kept by the engineer who designed blistol-detectors, this does not answer the question I'm looking at this forum. I even think that you advertise these detectors. This is not what I'm looking for here. I rather liked the answer to "Carl-NC"-It sounds reasonable and logical. Carl-What do you mean when you talk about detectors with "mixed-mode" audio???

Dear "Getsa"!, stop your snotty responce as thanks that I wanna tell you the facts!

Not everything that sounds reasonable and logical hits the true point because this world consists of huge "camoflage" and deceiving and besides you always have to search for the best possible question and reason to get the best answer and result.

What I told you has nothing to do with advertising and I even don't know if Blisstool makes a big secret out of his electronic or not but infact it is logical what I told you, too:

If you want to distinct between very slightly changes in the spectre of red color you need a device that is able to find the slightest changes in color temperature measured in kelvins. And not a colorblind person as funny example!

Distincting what kind of metal it is is the same, but here you have to consider the influence of the ground. You cannot find a mineralic stone in high mineralic ground with iron off disc. But you can find it with a detector that is extremly sensitive to the whole range.

btw. I never heard that Nautilus or Whites would be much better than any other MDs just because those have this special feature.