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Патент USA US2117670

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May 17, 1938.
M. FfKETAY ET AI.
2,117,670 _
SALINITY INDICATOR
Filed sem.` 1o, l195e
A-C-UNF.
m
l.
Patented May 17, 1938
N 2,117,670
` UNITED-STATES
. PATENT oFFlcE
j 2,117,670 ~
SALINITY INDICATOR
Morris Fred Ketay,~ Brooklyn, N. Y., and Joel
Darwin Peterson, Roselle, N. J., assignors to
Bendix Aviation Corporation, South Bend,
Ind., a. corporation of Delaware
Application September 10, 1936, Serial No. 100,216
‘5 Claims. (Cl. 175-183)
Fig. 5 is a vector diagram similar to Fig. 4
This invention'relates to devices for electrically
measuring and indicating the saline content of l but illustrating the conditions existing when the
iiuids, and more particularly to the electrical cir
cuits employed in salinity indicators of this type.
One of the objects of' the invention is to pro
Ui
vide an improved salinity indicating device in
which is embodied a novel electric circuit for ef
fecting movement of that element of the device
the position of which serves as an indication of
10
the degree of salinity of the ñuid being tested.
Another object is to provide a new and im
proved electrical circuit for use in salinity indi
cators in which a modified form of Wheatstone
bridge/is utilized.
15
A further object is to provide a salinity indi
cator of the character referred to in which is
included improved means for compensating for
variations in the temperature of the fluid being
tested.
20
`
.
'
Still another object is to provide an electrical
-
ciflc Acircuit arrangement has been disclosed and
illustrated in the accompanying drawing, it is
to be expressly understood that this drawing is
5
.
that required to balance the bridge circuit.
As shown somewhat schematically and -diagrammatically in Figs. 1, 2 and 3, the salinity
measuring and indicating device of the present
invention comprises an electrical meter so com
bined with a modiñed form of bridge circuit and
a salinity cell,as to give an accurate indication
of the degree of salinity of the ñuid being tested
in the cell. Since the resistance to current iiow
through the salinity cell varies inversely with the
temperature of the ñuid as well as with its salin
ity, the vindicator circuit also includes means for
compensating for variations in the ñuid tem
The meter or indicating portion of the device
consists of movable and fixed elements mounted
20
in a suitable casing 9 in such a manner that the
position of the movable element at any instant
constitutes a clear indication of the salinity of
the fluid being tested. ' As illustrated, the mov
able element of the meter -comprises a pair of
circular coils of wire C1 and C2 mounted with
be construed as a definition oi’- the limits of the
their planes at right angles to one another and having a common diameter, indicated at I0,
which serves as their axis of rotation. Coplanar
invention, reference being had for this latter
with coil C1, yand ñxed with respect thereto so
purpose to the appended claims.
.
as to rotate therewith about axis IIJ, is a suit- v
In the drawing, wherein like `reference charac
ters indicate like elements throughout the sev
`eral views:
`
Fig. 1 is a view of the face of the meter or
indicator of a salinity measuring and indicating
device embodying the present invention with the
fixed and movable coils of the electrical circuit
indicated schematically, the positions of the mov
able coils and indicating pointer corresponding
to a fluid of zero salinity;
45
_
tion and of greater accuracy than similar instru
for purposes of illustration only and is not to>
40
_
' Fig. 6 is another vector diagram corresponding
to a fluid the salinity of which is greater than
perature.
These and other objects of the invention will
appear more fully upon consideration of the de
25 tailed
description of the embodiment of the in
vention which follows. Although only one spe--
35
the bridge circuit; and
salinity indicating device of improved construc
ments hitherto known to the art.
" 30
ñuid is (a) of relatively slight salinity and (b)
of sufficient salinity to just effect a balancing of
Fig. 2 is a diagram of the electrical circuit of
a salinity indicator constructed in accordance
with the invention;
y
,
Fig. 3 is a schematic rearrangement of the cir
cuit diagram of Fig. 2 more clearly illustrating
50 the modified bridge circuit utilized by the present
invention;
Fig. 4 isa vector diagram of the electromag
netic ñelds produced by the fixed and movable
coils oi’ the indicator when the salinity of the
fluid being tested is zero;
able indicating element such as a pointer II
adapted to travel` over a scale I2 calibrated in
terms of salinity. The fixed or iìeld element of
the meter consists of a, pair of field coils I3 and
Il, of somewhat larger diameter than movable
coils C1 and C2, which are ñxedly mounted ad
jacent themovable coils on opposite sides of axis
IIJ with their planes vertical and parallel to one
another. 'I'he magnetic fields produced by coils
I3 and I4 arefcoaxial and extend at right angles
to axis I0. As indicated in Fig. 2, ñeld coils I3 ..
and III are connected in series across the termi
nals-of the indicator, said terminals in turn be
ing adapted for connection to any suitable source -
of alternating current. Movable coils C1 and C2
are electrically connected to the electric circuit
of the indicator next to be described _by three
hair springs (not shown) of negligible- torque,
two of the springs being connected to the ends
of the coils while the third spring is connected
to the junction therebetween. The relative po
2,117,670
sitions of these three springs are shown in the
circuit diagram of Fig. 2 at the points marked
I5, I6 and Il.
»
'I'he elements of the indicator thus far de
scribed are combined and electrically connected
with a salinity cell and a novel testing -circuit in
the manner illustrated in Fig.- 2. As shown there
in, the cell comprises a suitable container I 8 for
the ñuid to be tested and a pair of electrodes I9
10 and 20 which are mechanically held in ñxed and
parallel spaced relation and completely immersed
in the ñuid in container I8. If desired, the salin
ity cell may be mounted in or secured to the in
dicator ‘casing 9 and suitable connections pro
15 vided for enabling the fluid to be tested to flow to
and from the container I8. One of the electrodes
ì of the cell, electrode I9 in the example illustrated,
is connected .to the same terminal of the indicator
as :field coil I 3 while the other electrode 20 is con
20 nected to the opposite terminal through two par
hence vary the current ñowing through both coils
Ci and C2, the relative amounts of current ñow
ing in coils C1 and C2 remain the same With the
result that the resultant iield R of said coils, al
though altered in magnitude, will not be changed El
in direction and the pointer vII will remain in the
position shown in Fig. 1. This ñxes the zero posi
tion of the pointer.
-
If it now be assumed that the iluid being tested
is slightly saline, the resistance to the passage of
current between electrodes I9 and 20 is reduced
to a finite value. Under these conditions, the cur
rent flowing in the circuit passes part through
the leg of the bridge containing the resistance T
and part through the leg represented by the re
sistance B, thus tending to balance the bridge and
reduce the current through the coil C2. Due to
the consequent reduction in the current passing
through the resistance T, the current flow
through the coil C1 will be slightly increased. The
fields of the coils Ci and Cz will then b'e of the
allel paths, one path including the fixed resistance
R1 and the other comprising movable coils Cz magnitude and direction represented by the vec- ‘
and C1 (in series) and a fixed resistance R3 which
serves to limit the current through the coils in tors F1 and F2 of Fig. 5, with a resultant field rep
25 the event of a short circuit of the electrodes. resented by the Vector R. Since the resultant
Connected in parallel with the cell and coil C2 is . field will again tend to align itself with the main '.25
field of the ñxed coils I3 and I4, the coils Ci and
a calibrated variable resistance 'l' which is adapt
C2 will be rotated through the angle a, this rota
ed to be manually adjusted to correspond to the tion
turn moving the pointer II through an
temperature of the ñuid being tested in the cell. equalinangle
in a clockwise direction.
Another fixed resistance R2 may be shunted across
If, at this time, the temperature of the ñuid in
coil C1 and resistance R3 in order to ensure a
proper division of current ilow between the coils the container I8 should increase, there would
C1 and C2. >As is best illustrated by Fig. 3, the result a ldecrease in the cell resistance B and an
increase in the amount of current flowing through
electrical circuit just described is in fact a modl
35 fied form of Wheatstone bridge with the resist- the corresponding leg of the bridge circuit. How
ance B of the iluid in the cell and temperature ever, this temperature change may be manually 3,5
compensated for by decreasing the variable re
compensating resistance T constituting the par
allel variable legs of the bridge and the coil C2 sistance T suil'iciently to result in the same un
balance of the bridge as before, and therefore the
functioning as the bridge wire.
same ratio of field strengths of the coils Ci and C2.
40
Referring now to Fig. 4, let it be assumed that
If the salinity of the ñuid were such that its 40
the salinity of the ñuid under test is zero-that resistance
acted to balance the bridge, the cur
is, the iiuid contains no salt; the resistance of the rent in coil C2 would be zero and the resultant
fluid tothe passage of alternating current then ñeld of the coils Ci and Cz would be the ñeld of
approaches an inñnite value. Under these cir
45 cumstances, if the terminals of the indicator be the coil Ci. In this case, the coils C1 and C2
would be rotated from their zero positions through
connected to a source of alternating current, the
entire current will pass through that leg of the the angle b indicated in Fig. 5 to bring the ñeld
Fi of coil C1 into alignment with the main field,
bridge circuit containing the temperature com
the pointer II turning through a like angle from
pensating resistance T and then divide between the
position shown in Fig. 1. Here again any
50 the coils C1 and C2. If at any instant the mag
reduction in fluid resistance due to an increase 50
netic ñelds of lfixed coils I3 and I4 are as rep
in temperature would be compensated for by re
resented by the vectors F1a and F14, the circuit is
`
ducing
the resistance T sufficiently to rebalance
such that the ñelds of coils C1 and C2 will be rep ‘ the bridge.
resented bythe vectors F1 and F2, as shown. The
’ If the salinity of the fluid should increase be
55 resultant of the latter two perpendicularly di
that suflicient to elfect a balancing of the
rected ñelds will be a field represented by the . yond
bridge, the bridge would again be unbalanced, 55
vector R which will attempt to align itself with
the main field F13, F14- of the fixed coils I3 and but in a direction opposite to that previously de
I4. Inasmuch as the coils'Ci and C2 are free to ' scribed, and the field of the coil C2 would be re
versed. Under these conditions, the positions of_
rotate about the axis I0, the tendency to align
ment of the resultant and main ñelds will place the 'vectors representing the iields of the several
the coils C1 and C2 in the positions indicated coils, after alignment of the resultant ñeld with
which, in turn, will carry the pointer II over the that of the fixed coils, would be as shown in Fig.
scale I2 to the position shown in Fig. 1. When 6. In this case, the pointer II will swing even
65 the direction of the current ñow is opposite to
further in a clockwise direction, as viewed in Fig.
that just considered, the directions of the vectors ' 1, onto the right-hand portion of the scale I2. 65
of Fig. 4 will be reversed; however, since all of _Anyvreduction in circuit resistance with an in
the ñelds of the circuit are reversed, the pointer crease of 'temperature will still be compensated
will remain in the same position. Furthermore, ' for by reducing the resistance T to produce the
so long as the salinity of the fluid remains zero, same degree of unbalance of the bridge as before
and thereby maintain the correct pointer posi
any change in temperature of the fluid or any tion.
variation in the resistance T will likewise have no
'I'here is thus provided by the present invention
eiîect upon thel position of the pointer. While a
change in the resistance T will vary the total an improved salinity measuring and indicating
amount of current passing therethrough and device embodying a novel electrical circuit for
producing an accurate indicatlonof the salinity
2,117,670
3
and an indicating member iixed with respect to
said movable coils for rotation therewith about
of the iiuid under test, the said circuit consti
tuting a modiñed form of Wheatstone bridge and
including as one of the variable legs thereof a
said axis, a variable resistance, and a ñxed re
manually adjustable resistance which serves to
compensate for variations in the fluid tempera
ture. Although only one particular form of in
the form of a Wheatstone bridge with the elec
dicator has been speciñcally disclosed, it will
be obvious that the invention is not limited there
to but is capable of a variety of mechanical em
10 bodiments. Various changes, which will now sug
gest themselves to those skilled in the art, may
be made in the forni, details of `construction and
arrangement of the elements Without departing
from the spirit of the invention. Reference is,
sistance, said electrodes, movable coils andre
sistances being electrically connected together in
trodes and variable resistance lying in parallel
legs of the bridge and one of said movable coils
constituting the bridge Wire, the other movable
coil and ?lxed resistance comprising the other 10
two legs of the bridge, said variable resistance
being calibrated in terms of the temperature of
the iluid being tested and manually adjustable
to compensate for variations in said temperature.
4. In a salinity measuring and indicating de
15 therefore, to be had to the appended claims for _ vice, a pair of spaced electrodes adapted to‘be
15
a deiinition of the limits of the invention.
What is claimed is:
1. In a. salinity measuring and indicating de
immersed in the fluid the salinity of which is to
be determined, a meter for indicating the cur
vice, a pair of spaced electrodes adapted to be rent flow between said electrodes including a pair 20
of parallel ñxed coils arranged on a common
20 immersed in the fluid the salinity of which is to
axis and adapted to produce a main energetic
be determined, a meter for indicating the cur
rent flow between said electrodes, comprising field, a pair of movable coils mounted in said
mutually interacting iixed and movable coils, a field with their planes at right angles to one an
variable resistance calibrated in terms of the other and having a common diameter about
vwhich they are free to rotate as an axis and an 25
25 temperature of the fluid being tested and man
ually adjustable to compensate for variations in
said temperature and a iixed resistance; said
lelectrodes, meter, variable resistance and fixed
resistance being electrically connected together
indicating pointer iixed with respect to said mov
able coils for rotation therewith about said axis,
a variable resistance, and a ñxed resistance, said
electrodes, movable coils and resistances b_eing
electrically connected together in the form of a 30
Wheatstone bridge with the electrodes and var
iable resistance lying in parallel legs of the bridge
tuting the bridge wire across one diagonal of the and one of said movable coils constituting the
bridge, a second coil connected across the other . bridge wire, the other movable coil and ñxed
resistance comprising the other two legs of the 35
` diagonal of the bridge, and a third coil compris
bridge.
ing a third leg of the bridge.
5. In a, salinity measuring and indicating de
2. In a salinity measuring and indicating de
vice, a pair of spaced electrodes adapted to be vice, a pair of spaced electrodes adapted to be
immersed in the iiuid the salinity of which is to be
immersed in the fluid the salinity of which is to .
determined, a meter for indicating the current 40
= be determined, a meter for indicating the current
flow between said electrodes including a pair of
flow between said electrodes including a plurality parallel fixed coils arranged on a common axis
of iixed coils adapted to produce a main mag
and adapted to produce a main magnetic field, a
netic field, a pair of movable coils mounted in f pair of movable. coils mounted ,inl said ñeld with
said iield and having a common diameter about
their planes at right angles to one another and 45
which they are free to rotate as an axis and an
indicating member ñxed with respect to said having a common diameter about >which they
in the form of a. Wheatstone bridge with the
electrodes and variable resistance lying in par
allel legs of the bridge, one of said coils consti
movable coils for rotation therewith about said
are free to rotate as an axis and an indicating
pointer ñxed with respect to said movable coils
for rotation therewith about said‘axis, a variable
ing electrically connected together in the form of resistance, and three fixed resistances, said elec
trodes, movable coils and resistances being elec
a Wheatstone bridge with the electrodes and var
iable resistance lying in parallel legs of the bridge trically connected together in the form of a
and one of said movable coils constituting the Wheatstone bridge with the electrodes and vari
bridge wire, the other movable coil and fixed re -able resistance forming two of the parallel legs 55
of the bridge and one of said movable coils con
sistance comprising the other two legs of the stituting
the bridge wire, the other movabley coil
being connected in series with one of the said
3. In a salinity measuring and indicating de
vice, a pair oi' spaced electrodes adapted to be fixed ‘resistances to form the thirdv leg of the
immersed in the fluid the salinity of which is to bridge and the second fixed resistance completing
the bridge, the third iixed resistance` being shunt
be determined, a meter for indicating the cur
rent `iiow between said electrodes including a ed across said third leg of the bridge to ensure
plurality of fixed coils adapted to produce a main a proper division of current betweenl said movable
magnetic field, a pair of movable coils mounted coils.
‘
MORRIS FRED KE'I'AY.
axis, a variable resistance, and a iixed resistance
said electrodes, movable coils and'resistances be
bridge.
`
I
„
in said ñeld and having `a common diameter
about which they are `fi.'i:ee¿tiyrgitate"as an`axis.
JOEL DABWIN‘PE‘I'ERSON.
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