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Патент USA US2108463

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Feb. 15, 1938.
T. zuscHLAG
2,108,463
APPARATUS FOR ELECTRICAL. PROSPECTING
Filed June 25, 1936
Z
INVENTOR
,
I.
2,108,463
Patented Feb. 15, 1938
UNITED STATES
PATENT OFFICE
2,108,463
APPARATUS FOR EIIEEgTRICAL PROSPECT
Theodor Zuschlag, West Englewood, N. J., assign
or to Hans T. F. Lundberg, Montreal, Quebec,
Canada
Application June 25, 1936, Serial N0. 87,230
4 Claims. (Cl. 175-182)
This invention relates to the art of electrical
prospecting in respect to minerals in the earth,
and more particularly involves a method of and
apparatus for investigating and determining the
nature and characteristics of alternating mag
netic ground ?elds arti?cially created in the
earth.
It is well known to those skilled in this art
that the nature and characteristics of such arti
?cially created ground ?elds is dependent upon
and varies with the nature and characteristics of
the earth that is permeated by and lies within
the e?ective range of such ground ?elds. This
‘established fact may be utilized when it is desired
to determine the nature and, particularly, the
subterranean character of certain sections of the‘
earth, by arti?cially setting up within the said
sections of the earth electric and electromagnetic
ground ?elds, then systematically analyzing the
resultant structure of said ground ?elds, and
20 ?nally interpreting the geological signi?cance of
the resultant structure in respect to its relation
25
mination of the ?eld strength ratio that ‘is being ,
investigated.
It is generally practicable to avoid di?iculties
of the character just described by making use of
an auxiliary balancing network to which the GI
pick-up or search coils are connected, which
auxiliary balancing network provides means to
adjust the apparatus not only for the ratio but
also for the phase variation of the ?eld strengths
that are being investigated. However, such aux 10
iliary balancing networks usually include vari
able impedance circuits which do not possess a
great range of operation, and which do not
readily yield the ?nal desired result by a simple
evaluation of a single adjustment.
The reason 15
for this last named de?ciency lies in the fact that,
in networks of the type generally employed for
these purposes, any compensation for different
ratios of the induced electromotive force usually '
is dependent upon the condition that the same
ratio also holds true with respect to the im
pedances contained in the various branches of
to the sections of the earth that are being in
the compensating network.
vestigated.
understood that this last named condition or re
The better known and most followed proce
dures designed to accomplish the above described
quirement renders it quite di?icult to measure 25
ratios which vary substantially from unity, be
cause it is apt to become quite di?icult to e?ect
or obtain corresponding impedance ratios, par
ticularly when using inductive impedance com~
30
binations.
It is a primary object of this invention to
result involve the use of one ofmore pick-up or
search coils, and aim at determining the ratio of
electromagnetic ?eld strength in one or more
planes
at one or more locations. For instance,
30
one well known procedure utilizes two frames or
coils that are connected in opposition to an in
dicator, theresultant de?ections of the indicator
being reduced to zero by suitably rotating one of
said coils until the electromotive force induced
in the said coil equals the electromotive force in
duced in the other coil which is disposed in an
arbitrary plane and at an arbitrary location.
Without going into technical details, it may be
40 stated that the ratio of the effective ?eld strengths
acting in a direction perpendicular to such arbi
trarily ?xed and located planes, may be computed
as a function of the number of turns of said coils
as well as of the angle of compensation required
45 to produce zero de?ection of the indicator. This
procedure or mode‘of investigation, while com
paratively simple, is not highly accurate because
it includes no provision to compensate for a
phase displacement of the two ?eld strength
50 values of which the ratio is to be determined.
Quite often, the failure to make provision for
compensation of said phase displacement makes
impossible the obtaining of a sharp minimum ad
justment of the angle of compensation and, thus,
55 may lead to an uncertain or inaccurate deter
It will be readily
overcome the handicaps and de?ciencies above
described by providing a new balancing method
and network apparatus that eliminates these
drawbacks; which method and apparatus is
adapted for accurate determination of the ratio
and phase displacement of ?eld strength values
in ground ?elds that have been arti?cially cre
ated in the earth for electrical prospecting pur
poses.
My new network apparatus is primarily char
acterized by the fact that the values of the im
pedances incorporated in the balancing circuit
remain constant and are independent of the
electromotive force ratio that is to be measured.
40
45
This improvement in the said apparatus not only
makes it possible to simplify the operation of
the balancing network but also, within reason
able limits, directly to translate or evaluate the 0
setting of the balance adjustment into elecro
motive force ratio or ?eld strength ratio. As
a result of this improvement my network ap
paratus is especially useful and desirable for
that large class of operators or investigators who 55
2
2,108,468
are not speci?cally or thoroughly trained in
electric engineering.
A practical embodiment of apparatus in
cluding my new balancing network is diagram
matically represented in the accompanying draw
ing, in which a suitable generator for alternating
current is denoted by I, and is connected by
means of the exciter wires 2, 2 to ground contacts
3 and 4 that are suitably spaced from each other.
10 The arrangement just described constitutes an
mathematical calculation, which uses the desig
nations
E5 to represent the electromotive force induced
by ?eld intensity H: in coil 5
Es to represent the electromotive force induced
by ?eld intensity He in, coil I
r 7
dr and dc to represent the equal impedances of
transiormer primaries 1 and 8
do and do to represent the equal impedances of
the search coils I and I
exciter circuit and is calculated to set up an
electric and electromagnetic ground ?eld between
the points 3 and 4. In order to investigate the
an and an to represent the two sections of 10
potentiometers II and I! connected in circuit
?eld strength disposition of said ground ?eld, two
15 search or pick-up coils 5 and 6, each consisting
of an identical number of insulated copper wires,
bu and bi: to represent the two sections of
potentiometers II and I! connected in circuit 15
with coil 6
are located at arbitrarily selected points trans
verse to arbitrarily selected components of the
?eld strength to be compared.
The said coils 6 and 6 are connected in series
20
with the primaries 1 and 8 of phase shift trans
formers 9 and I0, and to the ends of two identical
potentiometers which are denoted by H and I2.
The said transformers are preferably of the air
25 core type, as this somewhat simpli?es part of the
mathematical calculations in using the appara
tus; although transformers of the iron core type
are operative in thisapparatus.
The sliders of the two potentiometers are
30 directly connected with each other and mechani
with'coil 5
'
C1’! to represent the section of potentiometer I'I
enclosed between the centertap and the slider
of this potentiometer
I5 and Is to represent the currents set up by the 20
electromotive forces Es and E0
and
.
In to rlepresent the current through potentiom
eter ‘I.
With this premise, the following equation pre
vails for zero de?ection of the indicator:
In this equation the values of Is, In and In are
given by the expressions:
30
cally coupled in such a manner that a shift of
the sliders to the left or right, in the drawing,
does not change the total impedance of the cir
cuits 5, ‘I, II and I2 on the one hand, and 8, 8,
35 II and I2 on the other hand. In order to main
tain this condition, the secondaries II and I‘ of
the phase transformers 9 and III are connected
25
IFEL
dri-dri-bn-i-bu
and Iiv=kIs where k is the complex relation
35
to two electrically identical circuits, each of which
consists of a condenser and a resistance of equal
40 value.
The secondary I3 is connected to the
?xed condenser
is and to a center tapped
potentiometer I1; while the secondary.“ is con
nected to the ?xed condenser l8 and to the fixed
resistance IS. The center of potentiometer II is
I6
Considering the fact that d5=dc, d7=da and 40
an+a1z=bn+b1z the two expressions for Is and
Is may be written:
45 connected to the common point of potentiometer
l2 and the primary ‘I, while the slider of poten
tiometer l1 and the other end of potentiometer, l2
are connected to the input of an amplifying de- .
where C is the constant impedance of the two
network branches.
‘
Substituting these various expressions in Equa
vice [9, which is of suitable standard construc
50 tion. The output of the ampli?er I9 is connected - ti n (1), the following equation obtains:
to an optical or acoustical indicatorglllfwhich
may also be of suitable standard construction.v
In carrying out my improved method by use i
of the apparatus just described, the search coils
55 5, 6 are connected in such a manner as to cause
opposing current ?ow through the different sec
tions of potentiometers II and I2, under which
condition the normal de?ection or reading of
the indicating device 20 may be reduced to zero
60 by suitable movement of the sliders of poten
tiometers ll, l2, and the slider of poten
tiometer l'l.
‘
50
Cancelling the constant impedance value C and
dividing with the value of E5, this equation may
be written:
is)
Be
In
011
This equation indicates
Bibithat
bu the electromotive
force ratio Ee/Es, and therefore the ?eld strength
ratio He/Hs, is directly proportional to the poten
tiometer ratio a12/b12 whenever the value of po
tentiometer section on approaches zero. As al
5, 6 are not phase displaced, then it is not neces
65 sary to introduce a phase compensating complee ' ready stated, this condition occurs whenever the
ment by operation of the potentiometer l1, and two ?eld intensities He and H5 are in phase or
If the two electromotive forces induced in coils
the slider oi’ potentiometer II will come to rest
upon the center tap connection.
this- case,
only slightly phase displaced from each other.
Experience has shown that this is the rule rather
than the exception, and that in most cases it is
quite admissible to neglect the numerical value
the ratio of the two portions of. potentiometer 1.2,
as de?ned by the location of contactqpoint, ' of the second expression in Equation 3 and com
directly represents the ratio of theftwoelcctro— pute the electromotive force ratio solely from 70
motive forces and, further, the ratio ,ofthetwo the potentiometer ratio air/biz. On the other
?eld intensities which induce theseelectromotive hand, this'statement does not imply that the
forces in coils 5, 6.
> - a .
This last assertion may be
a‘
adjustment of potentiometer I1 is of no impor
tance for the purpose of obtaining zero de?ec 75
3
2,108,468
tion of the indicator. In fact, without help from
the phase displaced current component intro
duced by adjustment of potentiometer II, it fre
quently is di?icult, if not impossible, to establish
such zero deflection of the indicator.
After having thus obtained the value of the
?eld strength ratio at points 5 and 6, the appa
ratus, including the search coils, may be moved
to another combination of points and the above
prising, a plurality of pick-up coils, a plurality
of potentiometers, and a plurality of phase trans
formers, said elements being electrically con
nected in such a way that current induced in
the coils produces a potential across the poten
tiometers and energizes the transformers, the
sliders of said potentiometers being connected
with each other and movable in such a way that
the impedance of each of the two coil circuits
10 described operation repeated. By systematically
as a whole remains constant, and an additional 10
proceeding in this manner, the ground to be
investigated may be easily covered with a net
work of points of known ?eld intensity ratio.
which then may be interpreted, by any well
15 known and approved method, to determine its
geological meaning with respect to the ground
thus explored.
I have found that, in ?eld operations, it is
potentiometer having a slider electrically con—
nected to the ends of one of the said ?rst named
‘often desirable and advantageous to employ the
20 subject matter of this application in connection
or in combination with the subject matter of my
application, Serial No. 723,669, ?led May 3, 1934.
now Patent No. 2,062,630, of Dec. 1, 1936. This
enables the exploration, to be conducted on the
basis of both ground potential and electromag
netic ?eld investigations.
While I have set forth, in the foregoing, a
speci?c form of apparatus and have detailed
speci?cally a method of using the same to obtain
30 the desired results, I do not intend to be limited
to the details of apparatus or steps thus de
scribed, since my invention contemplates the
practicability of resorting to equivalents both in
the apparatus and in the method of procedure.
35 Hence, I intend the claims to be construed as
broadly as may be in the light_of the. existing
prior art.
What I claim is:
1. Apparatus of the character ‘described com
40 prising, a plurality of pick-up coils, a plurality
of potentiometers, and a plurality of phase trans
formers, said elements being electrically con
nected in such a way that current induced in
the coils produces a potential across the poten
45 tiometers and energizes the transformers, and
the sliders of said potentiometers being con
nected with each other and movable in such a
way that the impedance of each of the two coil
circuits as a whole remains constant.
50
2.‘ Apparatus of the character described com
potentiometers.
3. Apparatus of the character described com
prising, a plurality of pick-up coils, a plurality 15
of potentiometers, and a plurality of phase trans
formers, said ‘elements being electrically con
nected in such a way that current induced in
the coils produces a potential across the poten
tiometers and energizes the transformers, the 20
sliders of said potentiometers being connected
with each other and‘movable in such a way that
the impedance of each of the two coil circuits
as a whole remains constant, an additional po
tentiometer having a slider electrically connect 25
ed to the ends of one of the said ?rst named
potentiometers, and an amplifying device having
its input electrically connected to the slider of
said additional potentiometer.
4. Apparatus of the character described com 30
prising, a plurality of pick-up coils. a plurality
of potentiometers, and a plurality of phase trans
formers, said elements being electrically con
nected in such a way that current induced in
the coils produces a potential across the poten 35
tiometers and energizes the transformers, the
sliders of said potentiometers being connected
with each other and movable in such a way that
the impedance of each of the two coil circuits
as a whole remains constant, an additional po
40
tentiometer having a slider electrically connect
ed to the ends of one of the said ?rst named
potentiometers, and an amplifying device having
its input electrically connected to the slider of
said additional potentiometer, the ends of said 45
additional potentiometer being electrically con
nected with the ends of the secondaries of a said
phase transformer.
'I'HEODOR ZUSCHLAG.
50
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