X-terra 70 Ground Phase Readings about Mineralization

Oct 19, 2007
656
13
born in 3 sisters, tx. now living west of tilden
Detector(s) used
X-Terra70, X-Terra 50, Ace250, Ace150, GTI 1500,GTA 1000 Ultra, Tejon, Vaquero
Barnacale Bill
GROUND PHASE READINGS:
The ground phase reading i.e. 6, 45, 72 has nothing to do with how mineralized the ground is.
It is an indication of the type of ground, magnetic, conductive, or a combination of the two.
There is a technique to make a relative measurement of not only how magnetic the ground is,
but as to how conductive it is with the X70.

But at the end of the day there is even a simpler technique should you wish to compare notes.
Assuming homogeneous ground (no hot rocks), how high can you run sensitivity without falsing.
I suggest making comparisons using the 7.5khz standard 9 inch coil same mode, auto-noise cancel,
auto-GB, and check in AM mode by bobbing the coil for spitting.

As an example, one person could have a ground reading of 15 and get chatter at Sens=28, while
another with a reading of 15 get chatter at Sens=24.

On a personal basis much of what I see is freshwater sand in the 8 to 12 range. But the big
league stuff are the cobble fields where each cobble is it's own little piece of ground. Many
of the cobbles will deflect a compass needle 45deg, so it drives many machines crazy and wreaks
havoc on correct ID for metered machines. Throw in a little black sand and yehaww! Machines
that do well are the Fisher CZ's, Red Heat Tornado with DD coil, and X-Terras with DD coil.

But I do have a Mount Olympus of bad ground, a train station that no machine or coil combination
has been able to crack, it's just a nightmare. But sadly I keep going back trying to find the
key to unlock it.


One of the ongoing common mis-conceptions is that the Ground Phase Number(Ground Balance)represents
how much mineralization a particular soil matrix contains. The mineralization of course referring
to minerals that cause poorer performance of a metal detector, and not a particular quantity of
an inert material.

The Minelab X-Terra X-70 has a hidden feature which allows you to make a reasonably accurate assessment
of your ground conditions including the iron(Fe3O4, black sand) and/or the conductivity(salinity) of
your soil. To clarify, you can quickly measure in relative terms how magnetic or conductive your ground
is. You can then jot those numbers down and compare them to any other X70 users in the world.

As a matter of fact a database or registry could be set up to compare your conditions to that of others.
Therefore when an X70 user states that they have "high mineralization" which is hampering operation,
it can easily be verified whether such is the case.

The procedure is really just an extension of Auto-GBing the X70. So don't become overly concerned that
it is terribly complicated, it isn't.

Procedure in Normal GB mode with GB Tracking "OFF" and Sens=20:

A. Auto-noise cancel in the area you will hunting with the coil held 3 feet above the ground and
parallel to it.

B. Locate a target free area of soil.

C. Engage Normal GB & remain in the GB screen.

D. Place coil on the soil. Do not press the coil against the ground! This will distort the coil
shape and give an inaccurate result. Simply allow the weight of the machine to lightly keep it against
the ground.

E. Press the Auto GB button and raise coil about two feet above the ground before Auto GB has completed.
If by the time you reach the apex of pulling the coil up to two feet it doesn't complete, then pump up
and down from just above the ground to two feet high as accurately as possible. Recall that Auto GB
signals with a tone when completed.

F. While still in GB mode press and hold Patterns button to get the numbers. The numbers are six digits
in length but read out in three groups of two that will repeat if the Patterns button is held down.
Therefore 99 99 99(almost a million) is the largest number possible and 0(00 00 00) is the smallest.
Forty-six thousand would appear as the following sequence, 04--60--00. Make a note of the numbers which
we will call the "IRON NUMBER"(Magnetite...Black-Sand).

G. As a reference, numbers in the thousands are mild ground, medium grounds tens of thousands , and hot
hundreds of thousands. For clarity:

1. 0(zero) >> 10K mild ground.
2. 10K >> 100K medium ground.
3. 100K >> 1M hot to scorching.

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Procedure in Beach GB mode with GB Tracking "OFF":

The same as above in normal GB except that your are measuring conductivity. Great for Ocean beaches,
salt flats, & dried up lake beds etc. I would also take three samples in the exact same spot and average
them to get an average number, using either of the above procedures.

If their is enough interest, then a registry could be started to compare the various ground reports
with how stable the detector runs, and effect on depth, correct ID etc. The nine inch default concentric
MF should be the only coil used to take the measurements to create a standard. Keep in mind that the
X70 may be able to show you why other detectors you own behave in a certain manner based on soil
mineralization. It may also provide pertinent information about what equipment you should consider
for future purchases.
 

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