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Dec. 3, 1946.
2,412,046 .
s. c. HoARE
RESONAN'I‘ cmcun' SATURABLE CORE MEASUREMENT APPARATUS
‘ Filed Sept. 8, 1943
FREQUENCY
$0 CYCLES
i
3A.
23'':
26
Inventor:
Stepheh C.Hoar~e,
by k’ ‘ 6.’ .dwlw
Hus Attorney. .
Patented Dec. 3,
>
‘ 2,412,046
a
UNITED STATES PATENT oer-1c}:
BESONANT CIRCUIT SATURABLEbORE
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MEASUREMENT APPARATUS
Stephen C. Hoare, Manchester, Mam, asei'g'nor
to General Electric Company. a corporation of
New York
Application September a, 1943. sci-lame. 501,549
4Clalms. (01. 175-183) ~
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It is known that anarrangement similar to that
here shown in Fig. 1, omitting the condenser I‘.
My invention relates to unidirectional ?ux satu
rable core measuring apparatus and circuits, and
its object is to provide such apparatus of high sen
sitivity and amplifying ability. An important as
can be used to measure direct current by measur- .
pect 01' my invention is the use of a tuned circuit
or circuits in which there is included, as a variable
inductance, a saturable core. Where two tuned
circuits are employed, a diil'erential amplifying
of the core ll.
ing the alternating current by a meter ll, due to v
the variation in the inductance of the alternating
current circuit by-various degrees of saturation
However, when the alternating '
current circuit is tuned by means of a condenser‘
and the circuit is properly used .over the slope of
e?ect may be obtained by operation of the two cir
cuits on di?‘erent slopes or in‘reverse direction on 10 the resonance curve, a large increase in sensitivity
is obtained. Let it be assumed that with no di
the same slope of their resonant curves over the
rect current ?owing in coil l2, the alternating cur
detecting or measuring range. These and other
rent circuit has a resonant curve a, Fig. 2, and
features of my invention will be explained in con
operates at the point a: of such curve for the fre
nection ‘with the accompanying drawing, while
the features which are considered to be novel and 15 quency 01' source iii which is assumed to be con
stant at 60 cycles. Hence, at such time a current
patentable will be pointed out in the claims -ap-‘
:6 will ?ow in instrument l‘l, but its indication may
pended hereto.
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be suppressed as, for example, by adjustment of
' Fig. 1 represents a simple embodiment of my in
the zero return spring so as to have-a scale-read
vention involving a resonant circuit inwhich a
change in tuning isvobtained by a saturable core 20 ing of zero. Now with direct current ?owing in
coil l2, corresponding to the upper limitof the
reactor. Fig. 2 shows resonant curves explanatory
direct current to be measured, the circuit con-.
of Fig. 1. Fig. 3 shows an arrangement where a
stants can be so arranged that resonant curve
pair of saturable core resonant circuits are em
characteristic of the alternating current circuit
curves explanatory oi the arrangement of Fig. 3. 25 will be represented by curve b, because due to sat
uration of core i I the inductance in the alternat
Fig. 6 represents a compass application of my in
ing current circuit has been decreased, and hence,
vention where the degree of saturation is con—
the alternating current circuit will be, tuned to
trolled by the earth’s ?eld. Figs. 7 and 8 are res
ployed differentially. Figs. 4 and, 5 are resonant .
resonance at a‘ higher frequency than before.
onance curves explanatory of Fig_‘6, and Fig. 9
represents a further embodiment of my invention 30 , However, the frequency remains constant, so that
a current 11 now. flows in the instrument ll. ‘ I
where the di?'erential resonant circuit principle
is combined with a push-pull alternating current
excitation ampli?er scheme.
have found that the sensitivity of the arrange
ment can thus be greatly increased by simply add
ingth'e condenser and taking advantage of the
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In Fig. 1 let i0 represent a'direct' current circuit
in which it is desired to measure the current. H
represents a saturable-core of high permeability
magnetic material having a, low saturation point,
such for example, as mu metal. This core is mag
netized by unidirectional ?ux in proportion to the
direct current to be measured by a winding 12 con
nected across a shunt IS in the circuit I0. I 4 rep
resents another winding on core Ii energized by
as
resonant principle.
,
In Fig. 3, I have provided two saturable cores
' l8 and I9'each provided with saturating direct
current windings .20 and 2| energized in series
from a source ill, and alternating current wind
ings 22 and 23 energized in parallel from a, con
stant frequency source i5. Condensers 24 and 25
are provided in the parallel circuits of coils 22.
and 23. A full wave direct current recti?er in
strument 2615 connected to respond to the differ
ing i4 is in series with a condenser l6 and an al-v
ternating current responsive instrument II. It 45 ence, if any, in voltage across the coils 22 and 23.
It is noted that the direct current coils on the two
is seen that the alternating current circuit con
cores are wound in the opposite direction, while
tains an inductance H which is varied by the de
the alternating currentwindings are wound in the
gree of saturation of the core II, and the con
same direction. The same e?ect would beobl.
denser “5 which may also be variable for calibra
tion purposes. However, the saturable core in so tained if the direct current coils, were wound the
same and the alternating ‘windings were wound
ductance is the measurement variable of the A. C.
in opposite directions.
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circuit. The circuit will also contain some re
I'n,the arrangement _of_ Fig, Liv when therefisnq
sistance, and the sharpness of the resonance curve
alternating current from a source l5.. The wind
of the circuit will depend upon the amount of re
sistance therein.
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direct. wrrent , ?owing, the altcrnatinai current;
circuits‘are vso‘ adjusted that‘ theclr'cuit contaim‘
2,413,040
ing winding 22 and condenser 24 operates at
about the midpoint of the high irequency slope
of its resonance curve as at point 1:, curve 0, Fig.
4, while the circuit containing winding 23 and
condenser 25 operates at about the midpoint of
the low frequency slope oi its resonance curve as
mum amount oi the earth's ?eld in a given di
rection.
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The adjustment oi the apparatus is as iollows:
When the earth's ?ux pickup strips l8 and I!
are turned in an east-west direction so as to pick
up none of the earth's magnetic ?eld, the current
in coils 28 and 23 is adjusted so that the strips
at point 1:, curve 11, Fig. 5, and iurther, so that
I8 and I9 are partially saturated and the con
equal currents a: ?ow in the parallel alternating
densers 24 and 25 are adjusted so that the circuit
current circuits. Under these conditions it will
be apparent that the voltage across which the l0 oi.’ condenser 24 operates at point 11:, curve ‘la,
Fig. 7, and the circuit oi condenser 25 operates
recti?er instrument “is connected will be zero.
at point 3:: on curve 8a, Fig. 8.- At this. time,
and no current will ?ow in the recti?er instru
then, the currents in coils 32 and 33 are equal
ment. Now when direct current flows in wind
> and the instrument 2’! has a central de?ection
ings 23 and 2| to more or less saturate the cores
and indication opposite the designation E-—W,
i3 and IS, the reactances oi.’ the alternating cur 15 indicating
that the ship is headed either west or
rent circuits will decrease and at the upper limit
east. Inasmuch as this condition will prevail
of direct current ?ow the resonance curve 01' the
when the strips I 8 and I3 are at right angles to
alternating current circuit containing winding 22
the earth's ?e1d,~the instrument 2‘! will not, by
will be represented by curve e, Fig, 4, and carry
itself, indicate whether the ship is headed east
an increased current 1:, while the resonance curve 20 or west, so that I provide a small, cheap compass
oi the circuit containing winding 23 will be rep
34 which will point toward the designations E or
- resented as at f. Fig. 5, and carry a decreased
W depending upon the heading. The accuracy of
current 2. Note that despite saturation of core I9,
compass 34 needs to be su?lcient only to distin
the current in its alternating current winding
25 guish between east and west. Now let us assume
circuit decreases because of a further departure
the ship is headed to true magnetic north, so
from a resonance condition. The voltages across
that the pickup strips I 8 and I! will pick up
‘windings 22 and 23 will be proportional to the
maximum earth's ?ux in a driven direction. The
difference in the currents y—-z ?owing there
direction of current in coil 23 oi strip l9 is'such
through, and this voltage is impressed across the 30 as to add its flux to the earth's ?ux in strip [9
recti?er instrument 2!! and produces a corre
at this time and to increase the saturation of
sponding ilow of direct current therethrough. It
such strip, decreasing the inductance of the cor
is seen then that the indication of the rectifier
responding alternating current circuit and caus
instrument ‘will be proportional to the direct
ing it to have a resonance curve 8b and a current
current ?owing in circuit H), but the amplifying
3;], Fig. 8. The current in coil 28, however, is in
ability or sensitivity of the measuring arrange
such direction as to oppose the earth's ?ux picked '
ment will be increased many times over non
up by strip i8, 50 that the saturation of this strip
is decreased and its corresponding alternating
resonant saturable core measuring schemes of the
prior art. .
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current circuit now operates at‘ point 11/, curve
In Fig. 6, I have shown a modi?cation of my
‘lb, Fig. 7. The ratio instrument 2‘! thus measures
invention as adapted for a remote indicating mag
the ratio of currents
netic direction indicator where the variable
£11
saturation e?'ect is controlled by the earth's ?eld.
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In Fig. 6 the core parts l8 and I9 are to be
located so as to pick up the earth's ?eld. For 45 and the instrument indication is marked with the
instance, they may be located on the wing of an
designation N, which is the indication repre
airplane sufficiently remote from vother magnetic
sented in Fig. 6.
material and disturbing in?uences to respond ac
Now when the shiptis headed south, coil 28
curately to the direction and strength of the
will add its ?ux to the earth's ?ux of strip l8.
earth's ?eld, and with their alternating current 50 while coil .29 will oppose the earth’s ?ux oi strip
windings connected with a remote indicator 2‘!
Hi. The corresponding alternating current, cir
arranged to indicate the direction in which the
cuits will operate on resonant curves 1c and 8c _
airplane is headed. The core parts [8 and [9 are
with currents ‘Ia and 82:, respectively, Figs. 7
of such dimensions and material as to become
and 8. Under this condition coil 32 will pre
partially saturated by the earth’s ?eld when
dominate and the instrument will indicate 8.
turned in line therewith, with the turning of the
For intermediate headings the instrument will
airplane or other structure to which they are
have intermediate indications, and the scale may
?xed. The earth’s ?eld takes the place of the
be calibrated in direction angles accordingly. If
direct current windings 20 and 2| of Fig. 3, and
the apparatus is used in widely di?erent localities
there are in addition, biasing direct current wind 60 such that the strength of the earth's ?eld varies .
lugs 23 and 29 wound oppositely on the two cores
appreciably, recalibration for the diiierent con
and connected in series to a direct current source
ditions will be called for.
30 through an adjustable rheostat 3| . The alter
The push-pull feature of Fig. 6 represents an
nating current windings 22 and 23 and the con
improvement even without utilizing the resonant
densers 24 and 25 in series therewith correspond 65 features. However, including the resonant prin
to like elements in Fig. 3. The instrument 2'! is
- ciples described very materially increases the
shown as a ratio instrument having coils 32 and
sensitivity. It is to be understood that the nature
33 connected to measure the ratio of currents in
of the instrument or other device of 21, Fig. 6,
the parallel alternating current tuned circuits.
may be any instrumentality which will respond
This instrument can be either alternating current 70 to the current ?ow in the parallel alternating
or recti?er direct current so long as it responds
‘ current circuits to give a signal ‘or response in
to the ratio oi the al-temating currents. -
accordance with the ratio of the currents in such
In the illustration it is assumed that the upper
ends of the core parts l3 and H are toward the
parallel circuits.
magnetic north, and therefore, picking up a maxi
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The sensitivity or ampli?cation response of
75 the resonant push-pull saturable core arrange
2,412,046 '
ment of Fig. 3 or 6 may be further increased by (
a di?ferential inductive coupling between-the par-.
current and alternating current windings on one
core being similarly wound and those on the other
allel alternating current circuits and the saturable ‘
core being reverseiy wound, a common source
cores employed as represented in Fig. 9. Except
of alternating current supply for said parallel cir
for the additional alternating current windings 5 cults, said circuits being so tuned that corre
.- 36 and 31 in Fig. 9, the arrangement is equiv
sponding changes in the unidirectional ?ux inthe
alent to that shown in Fig. 3, and equivalent
pair of core parts cause the current in one circuit
parts are designated by like reference characters
to increase and the current in the other circuit
in the two ?gures. It is seen trim in Fig. 9 the
to decrease, and means associated with both of
circuit of alternating current winding 23-on 10 saidrtuned circuits responsive to the differential
core is has a low turn winding 36 on core I8
current?ow in said parallel circuits.
wound in opposition to the main alternating
2. ‘Unidirectional ?ux’ responsive apparatus
current winding 22 thereon, and likewise, the I comprising apair of magnetic core‘parts so dis
y» circuit of alternating current winding 22 on
posed as to intercept unidirectional ?ux under
core I8 hasa low turn winding 31 on core l9 15 investigation and to be subject to varying degrees
wound in opposition to main alternating current
' of magnetic saturation by variations in‘ the mag
nitude of the ?ux‘intercepted, awinding on each
the effective alternating current excitingampere " of. said‘ core parts, means for connecting said
turns to change faster than the change in alter
windings in parallel circuits to an‘ alternating '
nating current exciting current. Let it be as 2 current supply. means including said windings
sumed that coils 22 and 23 each have 100 turns
for tuning said circuits such that corresponding
and coils '36 and 31 have 20 turns and that when
changes in the magnitude of unidirectional ?ux
intercepted by said core parts will cause the cur
the currents in the two alternating current cir
winding 23 thereon.
‘This arrangement causes \
cuits are equal; one ampere ?ows in each circuit.
rents in the parallel circuits to'vary inversely, _
and means vresponsive to the differential current
Then the effective alternating current ampere
turns in each alternating current circuit are
1oo-2o=ao.. Now assume that because of a
?ow in said circuits.
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3. Unidirectional ?ux responsive apparatus
subject to magnetic ?elds comprising a pair of
di?'erent condition of saturation, the alternating
elongated magnetic core parts mounted parallel
current exciting current of winding 22 increases
by 10 per cent and that of winding 23 decreases
to each other, direct current winding means on
by 10 per cent. Then the e?ective ampere turns ~, said core parts for producing reverse unidirec
~tional ?ux biases in said core parts such that
in branch 2: become 110—18=92, and the ei‘i'ece
tive ampere turns in branch :3 become 90—-22_—.88. ' ' when in line with a unidirectional magnetic ?eld
Thus the 10 per cent change in- exciting current
such ?eld, with the biasing ?ux, will substan
causes a 15 per cent change in effective ampere ” tlallyv saturate one core part and substantially‘
turns in the differentially coupled alternating
demagnetize the other core part, alternating cur
current circuits. The reactance in each alter
rent windings onsaid core parts, means for .con
nating current circuit branch .is proportional to
the eil'ective alternating current ampere turns.
necting said windings in parallel circuits to an‘
_ alternating current source ‘of supply, means in
Hence, a change in saturation in?uencing the re .10‘ cludlng ‘said windings -ior tuning said parallel
actance or effective ampere turns-is ampli?ed - circuits such that said circuits operate on sim
by such din‘erential or cross-coupling or the al
ilar slopes of their resonant curves and have“
ternating current circuits. This is- in addition
substantially equal currentswhen the core parts
to the ampli?cation obtained by the dl?erential
are in neutral positions relative to’ the ?eld, and
resonance principle employed. By the proper 45 mea'nskresponsive t9 the current flow in said
use of the diil'erential resonance principle and
parallel circuits to give a signal in accordance
the diil'erential coupling oi’ the alternating cur- rent circuits, an ampli?cation oi the order of -
six times the
with the ratio of the currents in said parallel
circuits.
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sponse'oi' the ordinary saturable
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4. Unidirectional ?ux responsive apparatus
core arrangement may be realized. '
50 comprising a pair of magnetic core parts adapted
' - In accordance with the provisions of the patent
to intercept unidirectional ?ux under investiga
statutes, I have described the principle of opera
tion and to be subject 'to various degrees of satu
' tion oi'.my invention together with the‘apparatus
ration-by variations in the‘ ?ux intercepted, a ..
~whichI now’ consider to represent the best em
main exciting winding and an auxiliary bucking
bodiment thereof, but‘! desire to have it under “winding on each core part,'a tuned circuit in
stood that the apparatus shown is only illustra
eluding the main winding-on one core part and
tive and that the invention may be carried out
by other means.
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the auxiliary bucking winding‘ on the other core
part, a‘second tuned, circuit including the re
maining windings on the core parts, connections
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What I claim as new and desire to secure by
. Letters ‘Patent of the United States is:
90 for energizing both of said circuits in parallel
- L-Unidirectional ilux responsive apparatus
from a common source of alternating current
comprising a pair of magnetic core parts adapted . supply. the tuning of said circuits being such
.to be threaded by the flux under investigation
and to be subject to varying degrees of saturation
- as to cause their currents to vary inversely with
respect to each'other by similar changes in the
by changes in the unidirectional ?ux threading as ?uxes intercepted by the core parts, and means
‘ said- core parts, a pair oi’ windings energised
currentv on said cores. 0. pair of parallel
timed circuits'including alternating current ex
citinrwindings on said core parts, the direct
.
' associated .with both of said tuned circuits re-‘
sponsive, to'the relative magnitude of current
?ow in said parallel circuits.
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C.
BOAR‘.
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