Ground balance

[ZED]

Bayu you could make a separate pulsing circuit for your sampling and run a sample through a circuit that changes the phase of the sample and run that to your demods as a means of ground balancing,i did exactly that on a SD2200 and it worked a charm.

[ZED]

eclipse the noise from both channels will combine,it was a generic suggestion to keep the noise to a minimum,im always playing with filters,i cant speak as to the reasons why or why not the other circuits do or dont use them,i just see it as an opportunity to reduce noise.

Also if one lives in a region of the world where the ground mineralization is mild and ground balancing is not so frequent then i suppose auto GB is not as much of a necessity.

[Bayu]

master, because in my country the majority of red soil is high in mineral, so it really needs GB, many relics of royal residues made of gold, for MD here the popular type of pi is our local product mimiti, and the very qualified product is nokta, and there some who use minelab, it is very financially draining for most people, there are Chinese products tx850 but many are easily damaged, I have made pi polones with my modification that is cheap enough for the community, but constrained by the Gb, for that I ask for help from the master at this forum.

[Orbit]

Hey ZED I'm looking at a circuit that has ground balance and there's a 100nF cap on the mixer amp as you say. If you look at TDI/GS5 designs you won't find any.
What is the benefit of the cap in there?

The circuit above is similar to what's described in ITMD book but honestly it came off Whites TDI circuit I have (there's a bunch of these TDI/GS5 floating around the forum have a look but watch out for errors).

Yes there are a lot of mistakes!Otherwise I do not notice that once set geb if we change location searches it must again be adjusted here in Serbia! Otherwise auto geb could be done on the TDI it came to my mind to take the signal from the exit from the comparator that signal I lead in mcu where it is checked whether the signal is o-volts if it is positive or negative over the mcu moves the digital potentiometer where adjustment is made that is, to bring the output to zero by pumping but without turning the analog potentiometer like before, I don't know how clear I was..Automatic tracking think it's wrong because of what Zed stated!I also have an idea of how it is done to device in the first thirty seconds automatically he chooses the frequency himself to avoid interference!

[eclipse]

Hey ZED I'm looking at a circuit that has ground balance and there's a 100nF cap on the mixer amp as you say. If you look at TDI/GS5 designs you won't find any.
What is the benefit of the cap in there?

The circuit above is similar to what's described in ITMD book but honestly it came off Whites TDI circuit I have (there's a bunch of these TDI/GS5 floating around the forum have a look but watch out for errors).

[ZED]

You could use that circuit but as 6666 says,theres a lot more to it,you would add caps to the circuit,particularly the mixer amp,you would need to duplicate the signal channel for the GB signal then pulse circuits for the extra demods,its a job and a half,plus each detector design has its own circuit topology and GB circuit,there is no one circuit fits all.

[6666]

Can this be installed on Pi? and what ic is used because there is no ic number information ,, thanks

There is a bit more to it.

[Bayu]

How about automatic ground balance ? Is not something that I believe has been discussed.

Can this be installed on Pi? and what ic is used because there is no ic number information ,, thanks

[ZED]

Auto GB can be done with an additional signal channel,which would be used for mathematical purposes or for determining coil direction,tracking on the other hand (ground balancing while walking) has a tendency to balance out very weak target signals.Alternatively it can be done without an extra signal channel but it would be limited to the lowering or the raising of the coil,not both...this is within the context of using an mcu.

[eclipse]

The LM13600 in the SD2000 is for the audio circuit and not related to the ground balance. Look in the previous stages how the GB is done, right before the channel selector switch, but if you are talking about absolute value audio circuit then perhaps you can use ideas from this audio to apply it to your design.

[Bayu]

can auto zero using ic lm13600 on sd2000 be applied to the pi scheme ?? I am still formulating the scheme!

[eclipse]

So maybe Auto Ground balance for a PI with adjustment (Slow/Normal/Fast) switch would be nice to have.
Also will help accommodate different sweep speed. Only thing left is to figure out how to do it ...

[6666]

Often thought about a auto ground balance, the highly mineralized ground in the gold fields here in Australia can vary quickly over a short distance

[green]

METAL DETECTOR BASICS AND THE0RY by Bruce Candy suggests ground X signal varies, ground R signal doesn't. Maybe PI doesn't need auto ground balance. Needs manual GB adjustment if delay time or sample time is changed.

[waltr]

No this is just answer to the question of the topic (just a regular TDI/GoldScan ground balance with manual adjustment).
I'm curious about doing auto GB and I don't see this being discussed anywhere.

Ahh.understand.I will try thinking about how to do auto GB with a PI.
Off hand nothing comes to mind as to what 'signal' to obtain and use.

I do have GB on mu HH2 PI but of course it is manual adjust which is done by 'pumping' the coil up and down on 'bad' ground then adjust until no audio response.
Possibly this could be done with a switch to enable 'auto-gb' then 'pump' coil.