Ground Balanced On The GPZ

[Reno Chris]

There does seem to be some ground balance issues, and its hard to tell in the video exactly what is going on, but I wanted to make a comment on the issue overall. In the video the operator runs his GPZ coil as if it were a mono coil (which he probably used on his last Minelab PI). The construction of the DOD coil is that it is made to swing from side to side, not to be pushed forward in and out. A mono coil is symmetrical all the way around the edge and it makes no difference if one swings from side to side or forward and back or out of angle from upper left to lower right or vice versa. The doubled D and DOD coils are made to be swung from side to side, not forward and back or in some other direction. You will not get the best performance out of your DOD coil by pushing it forward and back as the operator did the video and problems with going over uneven and differentially mineralized ground will be made worse as the operator effectively demonstrates in the video. In the white paper just released by Bruce Candy, he makes a point that trying to design a coil for the ZVT technology was a bit difficult because of the inherent sensitivity to uneven ground and mineralization changes. The DOD called design was the answer to this problem, but it really does need to be swung from side to side, not in and out as if it were a mono coil. The DOD coil does behave a bit differently than the coil's most operators have used in the past - it has a different geometry. You cannot just assume that it is exactly like all the coils (especially mono types) which you have used previously.

[normmcq]

I have noticed when digging a target, if stabbed in to the hole the target signal keeps getting weaker until I think I have dug a ghost signal. It is only after the target is completely out of the hole and am swinging from side to side that the signal gets stronger. I think many people will bury a legitimate target, This beast is different.

[Gold Hound]

Simple just flick into fixed gb when recovering the target problem solved.

I will make flicking to fixed part of my modus operandi if I get the same problem.

[mn90403]

In my first two days of using the Zed I had a similar 'event' on a much smaller target when trying to pinpoint.  I'll try the switching to fixed next time.

 

This does bring up the question of 'what is the shape of the signal?'  

 

We have been told to use these as reference but I know Steve has different ideas about it.

 

PI Mono = cone

PI DD = blade

VLF = cone

ZED = ???

 

Where is the best place to swing your target over the coil in a scoop?  front, sides?  sideways only?

[DDancer]

Zed= Blade similar to the DD profile but with a double positive when targets are presented from side to side. 

 

I have not been able to track out a good target in testing yet however I'm not testing in hot soil.  For me its testing till I get in the gold fields this summer.

 

One thing I would like to see return if its possible is a mono function like that for using DD coils.  Don't know if

its possible but it would help for pinpointing with the edge.  Targets seem to present themselves at the front of

the hole or to the side on itty bitties.

[Reno Chris]

I've been pinpointing with it in a manner more like a double D even where the target is a shallow double blip on each coil overlap. I figure it swinging side to side in one direction then turn 90 degrees and swing over it again to locate it in that direction,marking an X where I think it is.   

[G.B.]

Information is that GB is an averaged item.  From what I've experienced this is so.  As the video goes on the averaging continues and eventually the signal is lost even with the inadvertent pumping that occurs when dipping into a small hole. Other video's show the same pumping on good targets but the target is not lost.  A hot spot is a hot spot and the GPZ is only a bit less immune to them than current PI's... goes to show the advice JP and others are pointing out... the GPZ is not a PI in the classic sense. Again I'll point out that there was no re-doing of the GB in the video, one would have heard it in the audio of the recording by the cut out.  There was not one nor any attempt to Quick track the GB.  GP and GPX audio are different in the GB signal when working them.

What gets me is the other GPZ in the video.  I'm sure his mate took a swing.

I was his mate with the other detector and can honestly say I was a bit stunned when the target signal disappeared that I didn't even think of swinging my detector over the hole. As I walked over GH was swinging over the area around the hole to chk the ground balance and when he swung over the target I was certain it was a target signal so grabbed my pick and told GH to detect and video. We have arranged to go back and re check the hole.

 

It's all a learning curve at the moment and as time progresses and more ground time gets put in then I'm sure it will rewards will match the effort.

 

I will say that since reading the White Paper it has explained a few issues I was having and put to bed some bad habits I was developing and I do believe that Tech Paper should have been the second item Minelab put in the box.

[G.B.]

Looks like he is running in "normal ground". Should have been in "difficult ground" if it is making that much noise? I only have a couple hours on my 7000 but I was getting similar reactions in the area I was in with "normal ground" He might have been able to balance it out better with more  tracking in that mode? 

 

strick

The ground was highly mineralised and GH was running in Difficult General.  The area we detect in the Golden Triangle normal ground is as rare as hens teeth.  Very mineralised and highly variable.

[Steve Herschbach]

In my first two days of using the Zed I had a similar 'event' on a much smaller target when trying to pinpoint. I'll try the switching to fixed next time.

This does bring up the question of 'what is the shape of the signal?'

We have been told to use these as reference but I know Steve has different ideas about it.

PI Mono = cone

PI DD = blade

VLF = cone

ZED = ???

Where is the best place to swing your target over the coil in a scoop? front, sides? sideways only?

Detection patterns are far more complex than the blade and cone mythology sold by the marketers. One only need observe reality in the field to see that patterns for large targets and small targets are entirely different, even on the same coil. How many people know that the detection pattern for a small nugget on a large PI mono coil is a hula hoop, not a cone?

Same with GPZ. With large targets it acts like a mono coil but smaller targets react more to proximity to the coils winding overlap. The small targets also reverse tones in relation to where they are relative to said windings, producing some complex signals.

From the GPZ owners manual:

More information on the GPZ 14 coil http://www.detectorprospector.com/forum/topic/670-gpz-14-coil-for-minelab-gpz-7000/

[DDancer]

Appreciate the input GB Thanks.  Yeah the white paper would have put a halt a lot of things, but there's still plenty to chew on.

May I ask why you were stunned?

 

Steve I feel the myth holds some validity.

I've some understanding of the complexities of wave forms however the mythology works for a visual, and in a few ways a practical, way of training the mind on how a pattern is set up when working with various coil designs.  I've seen square coils and triangular ones as well but its the way the fields are set up relative to the receiver that make the difference.  Where the sweet spots are if you will.  The GPZ coil will pick up targets on the fringes if they are large enough just like a mono but it wont sing... only sound as a break in threshold hum.  It wont sing like a mono till the sweet spot is hit along the middle~ a blade.  Mono's will pick up targets as well on the fringe but dependent on depth will often sing out at the edge, mid or center of the coil so you've a cone visual.  DD's do the same thing but on the center line.

Basically proximity and depth relative to the area of highest sensitivity.  My thoughts.

 

As to pinpointing most of us are aware of the how mono and normal DD coils hit.  The GPZ makes it a little trickier.  I for one am still working on the sweet spot(s)   So I go with a blade mentality as it works for my visualization in nabbing the target.