Ground Balancing in iron rich and or salty ground
In WA much of our ground is iron rich, we export the stuff.
Swing a magnet and it comes back with a fuzz of magnetite attached.
Generally however we know when an iron rich terrain is encountered, the ground is blacker than that nice deep red brown loam.
On a 1 km walk to try and find a patch we could easily encounter both types of ground and gold is found in both.
While we may not see crystalline salt on the surface the term salty refers to not only NaCl but other salts associated with the rocks we are walking over.
These salts become highly conductive to electric current when moisture is present.
It takes a long time for the ground to dry out to an extent that this salt conductivity is reduced.
Now both iron and salt strongly affect ground conductivity and need to be cancelled out by ground balancing (GB) leaving other conductive metals to be detectable.
Both the 5000 and the 7000 have Fixed or Tracking modes that enable the machine to either be locked into some initial GB setting or to track the ground under the coil as we wander over the terrain.
From what one can read the 7000 GB procedure is not only very different from the 5000 but continues to use the ground signals to update its "algorithm".
This can even be upset by swinging over a tin can so it is recommended to switch to Fixed when digging a target.
Minelab has issued several changes in the GB procedure and the latest is the introduction of the need to use a Ferrite toroid in the GB process.
This indicates that the GB procedure for the 7000 is critical.
Furthermore as the 7000 is continuously updating its GB it implies that the Ferrite toroid must be frequently used to keep the GB optimised. Imagine that!
Before the toroid procedure came along I experienced a situation in an iron rich patch where my 7000 would not detect a sub grammer lying on the surface whereas the 5000 produced a very strong signals and a 2300 an equally strong result.
This was not a one off event, moving several hundred Km to another location the same disappointing result was experienced.
Minelab insisted the anomoly was " operator inexperience" but strangely the following week they changed the GB procedure yet again and pulled the Ferrite toroid out of their magic hat.
Yes the 7000 can produce marginally superior results in loams with low iron or salt but my experience is that I have walked over WA ground with a 7000 and left gold there.
This whole GB issue is not resolved and for me the machine is unusable in the normal range of WA conditions.