Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a method and a device
for detecti.on of -the presence of metal or mineral in a geological
formation.
~ hen searching for metals or minerals there have been
used different electrical apparatuses and methods. However, all
have been expensive and/or difficult to operate.
The present invention is based on the fact that every
metal or mineral has its own specific electrical potential. Com-
pared to hydrogent which frequently J.S used as a reference and
referred to as "earth", for instance coba:Lt, nickel and tin are
negative, whil.e plantinum, gold and silver are posi-tive. Inert
metals are clearly positive and in relation to said metals almost
all remaining me-tals are nega-tive. Metals and minerals may be
arranged in a so called potentia]. chain
Co Ni Sn
U-1.40 Zn-0.76 -0.29-0.23-0.14 Cu+0.51 Ag+0.80 Au+1.36
-1.5V -lV -0.5V +0 ~0.5V -lV +1.5V
which clearly illustrates the variation in contact potentials.
It is possible to use a two-pole probe connected to a
display member, and to insert the probe into the ground or a
geological formation, whereby the contact between one of -the poles
and metal or mineral grains of the formation result in a deflection
on the display member. However, it is necessary to know with
acceptable reliability what type of material the probe has contac-
ted. When a metal or mineral grain contacts one of the poles the
potential difference between the poles is changed. Changes of
potential may be processed and recorded in several ways, and present
day technology offers a wide varie-ty of amplifying and separating
methods.
The potential difference between the poles of the probe,
inter alia, depends on what type of material the poles are manu-
factured from. If the probe tip contacts a metal grain, or
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generally a grain of electr:i.cally detectable material, the poten-
tial is changed. The magnitude of the change of potential de-
pends inter alia on the size of the grain and the material and
shaped thereof. The poten-tlal change thus obtained in the form
of a signal, may be processed in an electronic unit to give an
indication of the presence of a metal grain. If one pole of the
probe, for instance in the shape of a tip, when being inserted
in the ground contacts a number of grains, there is a shower of
signals- In the elec-tronic unit it is quite possible to incor-
porate several facili.ties in order to separate different signals.
It is possible to give the tip a certain bias to obtain a thres-
hold potential where certain minerals g:Lve positive and othernegative voltage deflections. It is also possible to use threshold
levels for avoiding low level signals. Filtering rnay be done in
several ways and the number of pulses per time unit may be counted
to open a gate to the indicator member when a sufficiently high
pulse frequency exists.
According to the present invention there is provided a
method for detecting the presence of me-tal or mineral in a geo-
logical formation which comprises inserting a probe into the
formation which is connected to a display member, the probe having
two electrodes of diEferent material, between which a known poten-
tial difference exists, the display member including means for
indicating change of potential caused by contact between one
electrode and metal or mineral grains in the formation.
Thus according to the present invention there is provided
a method of detecting the presence of grains of at least one of
the kinds metal and mineral in a geologic formation~ comprising
providing a probe having two exposed electrodes electrically
insulated from each other in said probe and being of different
types of material so as to give a prede-termined potential differ-
ence between the electrodes when in a moistened mass, insertingthe probe in a geological formation having at least a certain
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moisture therein; elec-tronically detec-ting, while the probe is
being inserted, an instantaneous change of the potential difEerence
between the electrodes of the probe caused by a grain of said of
at least one of the kinds me-tal and mineral instantaneously con-
tacting one of said electrodes, thereby chanying the so-called
contact potential of the electrode; and electronically processing
a detected chanye of potential difference between said electrodes
caused by such contact be-tween a grain and one electrode -to pro-
vide an indication of said con-tac-t.
Preferably, the second electrode has a considerably
larger contact surface area than the first electrode. In order
to simplify the identifica-tion of a certain metal or mineral being
searched for, the electrodes are biassed to a voltage of lcnown
level, less than the expected voltage deflection.
The display member preferably is adapted to show mag-
nitude as well as polarity.
An apparatus for carrying out the method comprises a
probe provided with two electrodes of different material and a
display member comprising at least one component arranged for
indicating a change of potential caused by contact between one
pole and metal or mineral grains in the geological formation.
Thus the present invention also provides an apparatus
for detecting the presence of grains of at least one of the kinds
metal and mineral in a geoloyic formation, comprising a probe
having two exposed electrodes electrically insulated from each
other and being of different types of material, the probe being
adapted to be inserted into a geological formation and the elect-
rodes being chosen to give a predetermined potential difference
between the electrodes when in a moistened mass, electronic detect-
ing means for detecting an instantaneous change of the potentialdifference between the electrodes caused by a grain of said grains
instantaneously contacting one of said electrodes while the probe
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is being inser-ted into a yeologic forma-tion having a-t least a
certain moisture thereini and electronic processing means for
processing a change oE the potential difference detec-ted by said
electronic detectiny means, for providing an indication thereof.
A current source connected between the electrodes pre-
ferably is arranged for biassing the electrodes at a known volt-
age. The display member preferably comprises a component arranged
to indicate the magni-tude as well as the type of potential differ-
ence.
The other electrode preferably is shaped as an elonga-
ted, electrically conducting pipe, at the one end thereof having
a tip electrically insulated from the res-t of the pipe and form-
ing the other electrode. The ti.p may be resiliently connected
to the pipe to prevent damage to the probe and facilitate the
penetration into the Eormation.
The tip may be divided into several parts and also
comprise parts of different material. Furthermore, the pipe
may be of a flexible, resilient material having an electrically
conducting surface layer. It may be sufficient to use only one
type of display member, but there are also other types of such
members, for instance a hidden, movable part within the hand but
invisible to others.
The accompanying drawing is a vertical section through
a rod~shaped probe, inserted into the geological formation to-
gether with display and/or indicator members.
In the method of the present invention an easily trans-
portable probe 10 is used, comprising a pipe 11 of suitable
length, at least one end 12 being formed of a strong, metallic
material, for instance stainless steel. The probe is provided
with a handle 13 which facilitates the pushing down or screwing
into the formation.
At the end 12 of the pipe remote from the handle there
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is a pointed body 14, for ins-tance man~Eactured from a hard me,al,
insertable into -the pipe so as to be electrically insulated from
the pipe 11. Suitably, the insulation may comprise a glue 27
making it possible to change the bo~y when required.
The tip as such of the body cornprises a 21urali-ty of
disks 16 separated from each other hy grooves comprising an
electrically insulating mass 15. Each disk 16 has a relatively
small con-tact surface, while the pipe 12 has a considerable con-
tact surface and is "yrounded". The la-tter contact surface will
not be noticeably affected by rnineral grains around the surface.
Via a cable 17 the probe 10 is connected to a display
member 18. A lead 19 of the cable is connected to the tip 14,
and a lead 20 is connected to the pipe 12.
The display member 18 is connected to a current source
21, for instance an accumulator type of battery, and comprises an
amplifier and other type of conventional electronic e~uipment.
Signals that are received are indicated by audio visual members
of conventional type, for instance a lamp or light diode 22, volt
meter 23, and/or display 24 and ear phones 25.
In the drawing, the presence of different types of metal
or mineral grains is indicated by the references 26a, b, c.
There are different types of material in the two electro-
des 12 and 14, and by utilizing for instance common type of soil
or water as an "electrolyte" this results (preferably after fil-
terins) in a low level signal in the ear phones. Contact between
a disk 16 and a metal or mineral grain of any type results in a
"click" of variable strength. An experienced operator is able to
estimate the reilability of the existence of a certain mineral,
merely by means of the sound, but for a more exact registration
there is used one or some of the members 22-24.
As mentioned hereinbefore, each metal or mineral has its
own typical potential of a certain level, and by using the magnitude
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of the change of poten-tial it is possible to identify what type of
mineral the probe has contacted. Frequently, it is suitable to
arrange for instance the display 24 such that it also i.ndicates
the pol.arity in addi-tion to the magni.tude of the change of poten-
ti.al.
If one is look.ing for a certain metal, for instance gold,
which is to be found ~ui-te a dis-tance ou-t on the positive side of
the contact potential chain, it is possible to blas the poles 12
and 14 via the cable 17, and eventually filter away certain sig-
nals. This re.sults in that, :Erom a practical point of view, merelythe gold grains looked for are able to cause any change of the
potential pattern.
In order to reduce the risk for damage, the tip 14 may
be mounted resiliently in the pi.pe, and the tip itself may be
shaped as an obliquely cut cylinder simplifying the passage past
stones and the like in the formation. In certain layers of a
formation it may be of advantage to shape the tip, or the pipe,
; such that the probe is screwed down. For the surveillance of the
sea-bottom where the depth of the water is such that a rod-shaped
probe is not well suited, the probe may be formed as a heavy body,
which hanging on a wire is "pushed" down into the sea-bottom.
A certain moisture in the formation is a requirement
for obtaining a potential difference between the electrodes. When
operating in a very dry formation it may be necessary to provide
the probe with means for spraying moisture around the tip and/or
the pipe.
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