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What Do The Ground Balance Numbers Mean?


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Would my understanding of this be correct then: if pushing the coil towards the ground produces signal, it means that the GB value is set too high for this ground (on Fisher's scale) and too low on Minelab's scale (and when pulling the coil up, the reverse is true)?

 

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Basically, yes, you've interpreted the relationship correctly.

But it's only valid if you're lowering the coil to the ground, if you're lowering it from 20cm to 10cm, you're not doing it correctly.

It's a good question, because it then brings up the question "What is the audio signal indicating in ground balance mode??"

It's not simply indicating ground strength. If this were the case, lowering the coil to the ground would ALWAYS give an audio response. II guess it's pretty obvious that if the coil is 2cm above the ground, it's going to have strong ground pickup, and if it's 40cm above the ground, the pickup will be very much lower.

What's not so clear, is that the phase angle caused by the ground also changes as the coil is raised, and not in a particularly intuitive way. It actually changes towards 'Salt' as the coil is raised. So lowering the coil from, say, 15cm height down to a low level will cause an increase in ground strength, and a change in phase lag from, perhaps 25 degrees to 10 degrees.

If you're performing the 'pumping' procedure, ( groundgrab, fastgrab etc ) the micro brains can continuously read this signal, and work out that at the strongest point, that's the ground-balance value it has to calibrate to. But it can't use that value alone , it also needs to know what signal the coil gives when it's in free air, a long way from metal/ground/water. How it works that out, when you only raise the coil to 15/20cm high, I dunno.

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When hunting in mild ground as measured by the mineralization meter on the Deus I have seen a range of Equinox numbers displayed mostly low but occasionally high too.  In hot ground the Equonox numbers are consistently high.  But I have seen a wide disparity in balance numbers when swapping modes on the Equinox while GB pumping over the same patch of ground.  My conclusion is that there is not necessarily a lot of correlation between the displayed "ground phase" number and actual ground mineralization conditions (or even the ground phase for that matter - though the mode variations can be potentially explained by the different mode frequency weighting effects).  In fact, I am not sure that it is anything other than a convenient reference point for showing an initial balance point and subsequent deviations if you swap modes or move about the site.

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46 minutes ago, Chase Goldman said:

When hunting in mild ground as measured by the mineralization meter on the Deus I have seen a range of Equinox numbers displayed mostly low but occasionally high too.  In hot ground the Equonox numbers are consistently high.  But I have seen a wide disparity in balance numbers when swapping modes on the Equinox while GB pumping over the same patch of ground.  My conclusion is that there is not necessarily a lot of correlation between the displayed "ground phase" number and actual ground mineralization conditions.  In fact, I am not sure that it is anything other than a convenient reference point for showing an initial balance point and subsequent deviations if you swap modes or move about the site.

I have had my Deus 1 and Equinox 800 on various moderately to highly Fe304 mineralized ground where magnetite is visible on the surface and ranges in size from tiny particles to ping pong ball sized. These sites completely fill up the Deus 1 mineralization meter and my Equinox 800 ground balances between +1 and -3. Deus 1 ground balances in the low 90s at the same sites.

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59 minutes ago, Chase Goldman said:

When hunting in mild ground as measured by the mineralization meter on the Deus I have seen a range of Equinox numbers displayed mostly low but occasionally high too.  In hot ground the Equonox numbers are consistently high.  But I have seen a wide disparity in balance numbers when swapping modes on the Equinox while GB pumping over the same patch of ground.  My conclusion is that there is not necessarily a lot of correlation between the displayed "ground phase" number and actual ground mineralization conditions.  In fact, I am not sure that it is anything other than a convenient reference point for showing an initial balance point and subsequent deviations if you swap modes or move about the site.

Never seen my Equinox GB near zero in Culpeper.  Weird.

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What complicates the business of Ground Balance on multi-freq machines is the obvious: they have two, three, four operating frequencies. Hence multiple ground balance figures.

So on the Eqx: Park1 and Park2 both use the same transmitted selection of freqs, but the 2 modes will GB differently. It seems clear that as well as giving more emphasis to certain freqs in normal operating mode, the GB value also has a bias towards that same frequency.

( In my opinion, Park1 will have its GB dominated by the 7.8kHz freq; Park2 will be dominated by the 18.2kHz freq. )

Strong iron/magnetite etc ground will likely give similar GB values regardless of which mode/freq profile is being used, a near-zero phase angle is still near-zero at a different frequency.

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1 hour ago, Chase Goldman said:

Never seen my Equinox GB near zero in Culpeper.  Weird.

I also have hunted in North Georgia red clay a lot with Deus 1 and the Equinox. Deus 1 mineralization bar is usually 1/3 to 1/2 full with ground balance of 86 to 88. Equinox ground balances there between 20 and 40.

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My Equinox always has a lower GB number in Park1 than it does Park2 in the same dirt. The lowest GB number in Park1 I ever hunted was a 9-12 range multiple GBing during the hunt. The same place Park2 was in the low to mid 20's GB number. This dirt achieved the maximum depth of targets over any place I have ever hunted. It was almost pure sand. My hometown dirt is a red Loess that always GB's in the 30's Park1 and upper 40's to mid 50's Park2. Depth in this dirt is still very good, but as mentioned not as deep as the places my detector GB's to lower numbers.

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