Minelab GPZ 7000

[greylourie]

What is the scope measuring?

Hi green,

The device has some operating modes. High Yield/General/Extra Deep. The scope shots show frequency and duration of tx.

[Qiaozhi]

Who is saying what exactly ? Can you attribute your question to anything my above post might have said ? Bit surprised, that coming from Geotech admin. Especially when your posts are something I relish reading for their clarity of purpose.

I'm quite startled !

It's the bit where you said "Feel bit guilty not following through.", that prompted the question. I couldn't understand the "guilty" part, and thought I must have missed something here.

I wasn't sure whether this meant a major manufacturer (ML?) had acquired the design, especially when coupled with Kev's comment of "maybe if some of deemon's ideas make their way into the next revision".

Just asking ... but probably got hold of the wrong end of the stick.

[green]

Hi green,

The device has some operating modes. High Yield/General/Extra Deep. The scope shots show frequency and duration of tx.

Reason I asked. I understand the current is on all the time, most if the time at a constant current either positive or negative. The short glitches are getting to a constant current. Maybe I'm all wrong.

[greylourie]

Feel guilty, considering that deemon presented a project and I personally, never made the effort to try and follow through in attempting to repeat it/experiment with it. The requirements to get the main parts up are minimal. And it presents so many opportunities for someone like me to learn basic electronic circuit behaviour and loop control. Besides being quite a different approach and view to the normal offerings posted. His creation lets us look closely at how to manipulate pulse, and gives an the option to further study any benefit or positive attributes. It is novel and has great merit.

For a horrible moment I thought you had been possessed by some long banned "individual". And I was being cross-examined...

As for another's comment. I guess that is based on a generally perceived "aura" that some new idea, concept or refinement discussed on forums might end up becoming an element in some manufacturers patent. And/or end up incorporated in some manufacturers next generation/version of product. Without benefit to the community as free for use by all.

Maybe we all ate too much cheese in our youth.

[homefire]

Not to Muddy the waters but I have a Question. A Square Wave comprises a Infinite number of Odd Harmonics. Due to the Coil Inductance and Resistance The field going into the Ground is anything but uniform. (All Harmonics ) . The Return Signal is even more Warped ( Wire Inductance, Capacitance + Ground Effect ) . Do you think the Square wave use is Beneficial ? My bet is it DOES expand the Target signal some what.

[greylourie]

Reason I asked. I understand the current is on all the time, most if the time at a constant current either positive or negative. The short glitches are getting to a constant current. Maybe I'm all wrong.

I'm guessing, green. But maybe Kev used some non-invasive means to get the data. What I understand about volts and current would get me into trouble. All I see is alternating flat topped pulses 5-6µs long repeating at different intervals for the two main frequency modes ?

[Kev]

Well said Greylourie, very astute of you.........I too was feeling bad I didn't investigate deemon's ideas earlier, I could've saved myself $10 grand, but at first the xformers sent shivers through me.

I was closely following the to and fro between deemon and Aziz, over yonder forum, and an amazing development was taking place as I'm sure you're aware, when pride of a certain individual put a stop to what could of been a paradigm tech shift.

I mentioned that deemon's ideas might be snaffled, because it was uncanny how minelab PI's suddenly became much more immune to mains interference after Bug's kit was confiscated by the former. Maybe they didn't realise just how easy sync mains rejection really is until they inspected his code????

The only time the coil appears to maintain a field, is during those short pulses, if the current was flowing all the time, I would expect to see an exponential decline towards zero once the coil TC was reached.

I would expect a rectangular current pulse to have the highest di/dt of any form and by virtue of this, highest target field strength and coil/target uniformity.

Cheers
Kev

[greylourie]

Kev, the way you describe the field appearing during those short pulses. Just trying to imagine the amplitude/output and how it is accomplished is exciting. As for spending 10k, the product seems very sensitive and capable. Plus its backed by a name and has good resale value. Just at that price its a bit elitist, and seems to engender the wrong values in a certain group.

[Qiaozhi]

Feel guilty, considering that deemon presented a project and I personally, never made the effort to try and follow through in attempting to repeat it/experiment with it.

I suppose we're all guilty of that, me included.
The problem is that there's just not enough time to investigate every novel solution that comes along, especially when other work gets in the way, or when you're already deep into an experiment of your own.

For a horrible moment I thought you had been possessed by some long banned "individual". And I was being cross-examined...

No chance of that!

It looks like I tried to add 2 and 2 ... and got 5.

[Carl-NC]

When viewing the pulse train from afar, to my uneducated eyes, they almost look like flyback periods.

Probably what they are. I'd guess that is you looked at the coil current, it would be close to a square wave.

[Monolith]

Not to Muddy the waters but I have a Question. A Square Wave comprises a Infinite number of Odd Harmonics. Due to the Coil Inductance and Resistance The field going into the Ground is anything but uniform. (All Harmonics ) . The Return Signal is even more Warped ( Wire Inductance, Capacitance + Ground Effect ) . Do you think the Square wave use is Beneficial ? My bet is it DOES expand the Target signal some what.

That is not the way it works.

The current is switched from positive to negative. The switching itself is the transient that generates the eddy currents.
During the ON time, no eddy currents are generated, because it is a steady current, non varying.

[Kev]

The scope is seeing what a target sees (small inductor placed above the coil) so does this mean it is "the flyback that is kicking the target"?

Seems a waste of power unless power recycling is employed.

[Mechanic]

The scope is seeing what a target sees (small inductor placed above the coil) so does this mean it is "the flyback that is kicking the target"?

Seems a waste of power unless power recycling is employed.

Sure is the flyback that kicks the target, same with pi, however the beauty of the cc method is that the target eddy currents will be much lower at the point of the kick therefore the kick is a bit more effective as it does not need to first cancel eddy currents built up during the tx on period before building opposite polarity eddy currents in the target.

Cheers Mick

[Teleno]

Hi green,

The device has some operating modes. High Yield/General/Extra Deep. The scope shots show frequency and duration of tx.

By Tx do you mean the current in the coil (magnetic field) or the voltage across the coil?

If it's the former then long tau targets (big, deep nuggets) are visible right after the initiation transient of the pulse and short tau targets after the end transient.

This is so because from the target's point of view there are two pulse widths: a wide pulse (time lapse between the short pulses) and the short pulses themselves.

The receive signals would be something like this:

[Monolith]

Green trace = TX pulse

Red trace = long tau target response
Blue trace = short tau target response