An experiment

Hello all,
I have a request for those who may be brave enough or kind enough to try something for me and let me know your findings.

During a recent GPZ training session i encountered something that got the old grey matter thinking. We all had our detectors on with speakers off so i could run through the settings with everyone following along. I had already gone through the quick start procedure and the machine was humming and ground balanced nicely. I set my detector down on the ground to talk about some settings and didnt notice the coil very near my pick. When i came to do the next part of the practical demos (maybe 10 mins after putting the zed down) i had everyone turn off, put my speaker back on, and to my surprise the detector was screaming on the ground and would not re-ground balance at all. I performed a reset settings and she was good as gold.
This got me thinking about some of the 'issues' we have been seeing re noisy or unstable zed's. It seems to me that the detector being so close to my pick and in tracking mode had changed my ground balance considerably. I cant understand though why pressing the tracking button would not correct the ground balance afterwards......
I have had many customers tell me they had the zed switched on inside their house for testing (as you do) before their first ourting. And then have reported their machines being noisy and hard to gb in the field. No reset had been performed. Next trip they have performed a reset and the machine has come good. This to me makes a lot of sense and is where my thinking began (perhaps you all heard the gears grinding?)
Many customers have also commented their machines have started out great but as the hrs pass it got more unstable. Watching many people dig their targets i have noticed many that have the coil too close as they are digging, causing a target response from the pick each strike. Now imagine this happening many times in a few hrs in tracking mode- possibly throwing ground balance out thus a more unstable machine.

I would love if some of you brave zed users could try and re create this for me and let me know your findings. When your on smoko, leave your zed on and near your pick (or car or anything big and metal) and see what happens. Be confident that if it does what i think, a reset settings will correct it. For those even more curious, try deliberately causing a target response from your pick as you dig for a few hrs and see how the machine goes- all this must be done in tracking mode obviously.

phew...... i hope this doesnt open up another can o worms but i am very interested to hear from anyone who has found simmilar things.

Ive kept preatty quiet about the zed so far- she is a damn fine piece of kit, especially if you spend the time setting up the supplied harness and learning the settings. Im constantly amazed at what i have been finding with mine just on old patches- the clarity of the signal on small pieces and the depth they have come from has caused a few head shakes when the nuggies pop out. I have not found any dramas with the machine in terms of setup- learning to adjust the settings is the biggest key to success.

Anyway, thanks for reading and i look forward to hearing from anyone with their findings or thoughts.
Cheers,
Cory

G'day Cory,

That makes sense. I'm having to perform a full reset about 3-4 times per session due to the Zed getting chatty. I guess during that time, the zed is finding gold, signalling on junk, having close encounters with my pick etc. etc and perhaps the combined metal encounters are putting the Zed out of balance....

Yes Cory, I have found in the past and first time out that any large metal object, Quad bike and my pick does put the ground balance out. And any small bits of junk (tin, nails, tacks) will eventually put the ground balance out. Once you are aware of this it's not a problem, the pick is the biggest cause, I make sure now to keep the pick well away.

On the smaller junk the auto tracking, just doesn't seem to work fast enough. My thoughts anyway.

Cheers, Peter.

Great info guys!
This was sparked by a video on youtube recently (by another corey i think) where the detector seemed to be reacting just how ive described.
I have been using fixed gb alot and have been having great success with none of the instability issues that may arise from tracking. Ive had as good success in tracking also but need to ajust settings or re-balance frequently to smooth things out. I dont feel i am loosing performance as i have worked the same spot several times in tracking, then fixed, then in normal ground mode with a stupidly slow sweep speed. I have also gone fixed then tracking is spots too. i found the most gold in hy/diff with fixed- checked all targets in tracking too and all were audiable and about the same clarity. I have then gone to hy / norm with fixed gb and slightly lower sens (coil about 30-40mm above ground too) over the same spots and only found the odd tiny bit at stupid depths afterwards.

anyways, keep the info and thoughts coming guys!
Cory

Interesting stuff...have any of you tried leaving the ZED in tracking....with no metal near by for the same amount of time to see how it reacts. Including leaving the ferrite within range of the coil.?

My understanding is its taking a very large means of its proximity to the surrounds....and its doing this over a long time frame.??

Q. Does the ZED have a GB off mode.?
If so, it maybe a lot easier to dump the GB memory than reset it.?...dont know myself...dont have one and have not used one....but iv assembled plenty....lol

Just thinking out loud.

Narrawa,  I don't think the ZED has a GB off mode. My understanding is when hitting the quick track button all memory for the gold/ground mode you are in will be lost.

Have never left the ZED switched on for long periods of time unattended, and probably never will, I always turn it off for for a break. WE are all learning wish I could get out more.
We seem to learn something new every time out.

Cheers, Peter.

peterinaust wrote:Narrawa,  I don't think the ZED has a GB off mode. My understanding is when hitting the quick track button all memory for the gold/ground mode you are in will be lost.

Have never left the ZED switched on for long periods of time unattended, and probably never will, I always turn it off for for a break. WE are all learning wish I could get out more.
We seem to learn something new every time out.

Cheers, Peter.

Well you might be right, but hitting the quick track button does not appear to be helping from what im reading....hence the reason for a full reset.?

Narrawa wrote:

Q. Does the ZED have a GB off mode.?
If so, it maybe a lot easier to dump the GB memory than reset it.?...dont know myself...dont have one and have not used one....but iv assembled plenty....lol

Just thinking out loud.

G'day Narrawa

The Zed doesn't have a GB off mode like the 4500/5000, it has a manual GB mode which is the same as the fixed GB mode on the 4500/5000

This is how I have been using the 7000 in fixed mode and if the ground is different from where you last detected the use the ferrite and GB over it and leave the thing in fixed, it works for me.

cheers dave

Narrawa wrote:

peterinaust wrote:Narrawa,  I don't think the ZED has a GB off mode. My understanding is when hitting the quick track button all memory for the gold/ground mode you are in will be lost.

Have never left the ZED switched on for long periods of time unattended, and probably never will, I always turn it off for for a break. WE are all learning wish I could get out more.
We seem to learn something new every time out.

Cheers, Peter.

Well you might be right, but hitting the quick track button does not appear to be helping from what im reading....hence the reason for a full reset.?

hi fellas, just back from another couple of weeks with the 7000. i mostely ran in auto ground balance, experienced many times when the resting z was not far enough from the dig hole, then moved it, but not once did i have to do a "reset from scratch". all thats required is a quick pump up and down with the quick track button held in, and bobs your uncle.

i know about the memory of the ground balance, but if the machine didnt get quiet enough, again, with the above, i just repeated it again. never got into any trouble.
a few things i noted -----
when on a target, suspicion it is ground noise or charcoal, just slow down a bit, wave the coil over it a few more times, you will get your answer by it not disappearing or becoming quieter, if its a target.

when in filthy rubbish, the slowness of the sound receding from a large metal object, makes it very hard to cover any amount of ground, definately inferior to previous machines. and because the z hears metal objects out to the side, its near impossible to detect any ground between two metal bits of rubbish.

found i didnt like the difficult mode, it gave me a singsong response, like a piece of twisted wire, and the signal was reversed, that is, a down and up sound. gets confusing. so i mostely kept the machine in normal, and if the ground was noisy, the use of smooth at low or even at high smoothing was better than going into difficult.

redone a very productive area over the years, that has a noisy red anthill type of ground, that really needs the difficult mode, but i was able to find a couple of nugs that were missed, by running in deep, normal, with the smoothing at high, purred like a kitten, and testing (which i do all the time when changeing settings, with a .3 and .7gram testers) confirmed very sensitivity to surface smalls, so i knew i wouldnt be missing anything significant by running in deep.

was a good two weeks with a get of 64 pieces for 48grams.

i pitted myself, during the last couple of days, to find a piece at any new spot, by firstly getting the machine to run quiet, then upping the sensitivy to get the best response to my testers. worked a treat. i came home confident this new machine has now been tamed by me, and i will be confident i will be able to go to any sort of soil and if i walk over a piece, i will find it. great feeling ... kev

All Minelab detectors with auto ground balance and auto tracking from the GT16000 on wards use an algorithm that relies on the so-called X component to decide if it should attempt to null a signal or leave it alone.

The ground gives a (+X) signal whereas non-ferrous targets give a (-X) signal so a (+X) signal tells the GB circuit to activate and a (-X) tells the GB circuit to hesitate.

The problem though is that the pick also gives a (+X) signal and this activates the GB and tends to drive the balance way out of whack if you can hear the pick when digging the hole.

So, the GB should be fixed when digging or is anywhere near a ferrous target.