Improvements in and connected with Electrical Indicating and Measuring Instruments.
Year: 1899

page_text: Date of Application, 10th Oct., 1899-Accepted, 24th Feb., 1900
COMPLETE SPECIFICATION,
Improvements in and connected with Electrical Indicating and
Measuring Instruments.
I, MONTGOMERY WADDELL, of 72, Trinity Place, in the City, County and State
of New York, United States of America, Electrical Engineer, do hereby declare
the nature of this invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement:-
This invention relates to electrical indicators or instruments whose function
is to 'show at any time the condition of the current flowing in an electric circuit
or circuits.
The object of the invention is to provide an instrument of this character in
which there shall be, practically speaking, no movement of solid masses created
directly by the current, thus eliminating at once many problems and difficulties
which have hitherto proved to be obstacles to the production of accurately opera-
ting instruments. In those instruments containing moving parts the weights
of those parts, their inertia, the friction accompanying their motion, and so
forth, must be allowed for, and with the changes wrought in such parts by
differences in temperature, it is quite difficult to construct such instruments to
more than approximate accuracy. In the instrument I have invented there is,
in theory, a moving part, but the motion is so slight in fact that it can scarcely
be detected by the naked eye and is negligible as a factor in the production of an
accurate instrument. The indicating element of the instrument herein described
is a column of liquid which is caused to rise and fall by differences of gas or air
pressure, which differences are created in accordance with variations in the
current whose condition is being indicated. My improved indicator comprehends
important details of construction as well as certain novel and important principles,
all of which will be fully described hereinafter and pointed out in the claims.
In the accompanying drawings,
Figure 1 is a central vertical section of the improved instrument, parts being
shown in elevation:
Figure 2 is an enlarged detail of the valve:
Figure 3 is a plan of the spool and its balancing support:
Figure 4 is a rear view of the magnet and counter-balancing devices;
Figure 5 is a section on line . r of Figure 3.
Referring to the drawing by letters, let A represent a slab of slate or other
material constituting the face of a station switch-board or other adopted support
for the instrument. In front of this and extending vertically is a glass tube b
similar to a gauge glass supported between upper and lower couplings 61 and 69
respectively, and having a suitable scale. A passage from the upper counling
extends through the support A into the base-plate C₁ of a dome C, while the lower
coupling similarly connects through the plate A with the lower end of a stand
pipe B whose upper end, for the purpose of stability only, is attached to the
under side of the base plate C¹: The stand pipe and gauge glass contain water.
oil or other liquid, preferably coloured, to be easily observed in the glass and
freely communicating through the lower coupling." The capacity of the stand

page_text: pipe compared with that of the gauge is large, so that a displacement of the
liquid in the gauge will be accompanied by only a slight displacement of the
liquid in the stand pipe.
The atmosphere is freely admitted above the liquid in the standpipe through
suitable openings in the upper end of the latter.
It will be observed that the plate C¹ is of considerable thickness and contains
a central internal passage extending from front to rear. At the front, this
passage connects with the passage through the tubular coupling 61; from this
coupling it extends rearwardly to about the middle point of the plate where it
enlarges into a threaded cylindrical chamber of short length which extends to
the rear of the plate where it is sealed by a plug c¹. At the rear, and passing
upward from the underside of the base plate are two conical passages ca, leading
into the enlarged chamber. These are adapted to receive pipe couplings, one of
which will connect by suitable tubing with a source of constant air or gas pres-
sure, while the other may be plugged up or connected with another tube leading
to another indicating instrument of similar character, thereby providing for con-
necting a series of the instruments with the same. source of air pressure and
ensuring that the pressure in all the instruments will be practically the same,
since the air chambers of each are connected together. The threaded portion of
the air chamber receives a hollow threaded plug e, having a conical end e¹, fitting
into a similarly shaped portion of the passage c. This plug cuts off communi-
cation between the front and rear portions of the passage c, but it has an axial
passage extending through its conical portion and in alignment, at its forward
end, with the air passage extending to the coupling b. Into the rearward end
of this axial passage, the end of a capillary tube e³ projects. This capillary tube
is some eight or ten inches long in the ordinary instrument, and in order to
confine it in a small space it is coiled inside the chamber of the plug, its free or
rear end being open to allow the air in the rear part of the chamber e to flow
into the forward portion of the said chamber c. At f is shown a vertical passage
extending from the chamber c upward through the face of the base-plate. Into
this is fitted a plug d with a passage leading from the chamber to the atmo-
sphere, this plug is shown in detail in Figure 2, wherein it will be seen that its
passage is covered at the top by a very small and light disc valve which is
held in place. by a sleeve having lateral openings through which the air
or gas, which is allowed to escape from the passage, has an exit. The under
surface of the valve makes a smooth even fit with the top of the plug which, at
that point, is merely a flange surrounding the escape passage.
Mounted above the base plate C¹ is a permanent magnet. M, of horseshoe
form, the legs being partially connected by an iron plate m having a circular
vertical opening m¹ in one end, through which a leg of the magnet passes: the
end of the leg is made cylindrical and of less diameter than the opening m¹ so as
to leave an annular space forming a field of force. The magnet is supported
above the plate by means of two brass blocks o upon which is placed a plate of
hard rubber or other insulating material o to which the cross piece of the magnet
is secured the rubber plate also being rigidly secured to the blocks 0, this
arrangement insulates the magnet from the blocks. The blocks carry metallic
studs which pass downward through the base-plate and are fitted with suitable
binding devices for the electrical conductors through which the current flows to
actuate the instrument. The blocks o and the studs o2 are insulated from the
base-plate in the manner shown in dotted lines in Figure 4. In the space imme-
diately beneath the magnet and between the blocks I arrange a balancing arm p,
screw threaded at its rear end to receive threaded weights p¹ in the form of nuts.
and at its forward end carrying a spool or frame 7 of hard rubber or other material,
the upper diameter of which receives a coil of wire gl. The arm prests on the
valve disc and determines by its pressure thereon the pressure in the forward
part of chamber c. The balancing arm carries a cross bar 7 of hard rubber or
other insulating material which is firmly secured thereto by nuts p³. At each

page_text: extremity of the cross bar is provided a clamp consisting of a metallic plate p
held against the side of the cross bar by screws p. In each of these clamps is
fixed a very thin strap or ribbon of metal projecting upward and passing into
clamps on the blocks o, similar in construction to those on the cross bar. The
straps of metal support the balancing arm and the devices which it carries, form-
ing a pivot on which the arm may turn through its very slight working angle,
without substantial resistance or friction. The terminals of the coil g' lead
respectively to the clamping plates 2 and the steel straps serve to connect said
clamps with the brass blocks o, thus establishing a complete circuit between the
binding posts of the instrument through the coil q. To prevent derangement of
the balancing arm thus delicately mounted, I embrace its forward portion in a
pair of blocks s in which it has sufficient play to perform its functions, but being
so confined as to prevent displacement. These blocks are secured to the under
side of the magnet.
The spool 9 projects into the annular field of force of the magnet sufficiently to
bring the entire coil under the magnetic influence.
The operation is as follows:-
Let it be understood that a pump or reservoir is furnishing gas or air under
approximately uniform pressure to the rear end of the chamber or passage c
through one of the openings c³. This gas or air slowly forces its way through
the capillary tube into the forward end of the passage e through the couplings
and acts upon the surface of the liquid in the glass column, forcing the liquid
down to a point depending upon the effective pressure of the air at the surface
of the liquid. This point is predetermined as the zero point of the scale, and
the liquid in the glass column will always be at this point so long as no current
flows through the coil g' at the zero point the upward pressure of the liquid
exactly balances the pressure of the air. It will be observed that if, for any
reason, the liquid level does not coincide with the zero mark on the scale, it may
readily be made to do so by adjusting the position of the counterweights pl and
thereby adding to or decreasing the pressure of the arm upon the valve.
When the zero point is properly adjusted, the current of proper polarity may
be allowed to flow through the coil whereupon a tendency will be developed
to lift the coil and spool depending on the strength of the current flowing. As
the pressure on the upper side of the valve is thus relieved, the air pressure on
the under side that is necessary to balance it becomes less and an increased flow
of air takes place. The level of the liquid column accordingly rises to a point
corresponding to the strength of current flowing. A decrease in the current
reverses these actions.
Since the weight of the spool and the coil is offset to any degree desired by
the counterweight, it is obvious that the instrument may be operated with very
small expenditure of current and it is also evident that the valve will be very
sensitive.
Now, while I have referred to the movements of the coil and its spool as a
lifting and falling operation, the fact is, that these movements are so slight that
they not only can scarcely be detected by the naked eye, but require an extremely
delicate instrument to measure them. Perhaps the best description of the
operation of the air valve is to say that the spool is caused to rest lighter or
heavier upon the valve according as the current flowing its coil is stronger or
weaker.
The function of the capillary tube e is to act as a retarding device for the air
between the source of air pressure and the air chamber whose pressure is con-
trolled by the air valve. The capillary tube being of very small diameter, offers
a high resistance to the flow of the air from the rear to the forward portions of
the chamber e and if an extraordinary large amount of air be released from the
forward part of said chamber by the valve, nearly its entire effect will be felt by
the liquid column instead of a material portion of the effect being wasted in
drawing air from the rear part of the passage c connected directly with the

page_text: source of air. This capillary tube also acts as a damper between the surface of
the liquid column and the source of air pressure, the sudden effect of impulses of
air being thereby reduced. The function of the capillary tube being under-
stood, it becomes obvious at once that other devices may be substituted for it,
Hence my invention comprehends any construction of air flow resistance. The
principal of this indicator is adapted for use in various ways; for instance, the
current may be sent through the coil in the opposite direction, whereat increase
of current through the coil would have the tendency to lower the spool or make
it rest more heavily upon the valve, which would give an increased air pressure
and a lowering of the liquid column. When operated in this way the zero point
would have to be at the top of the liquid column, and the air pressure at zero
would be equal to the atmosphere. Again, the zero point of the scale may be
at an intermediate point of the column so that when the instrument is used on a
circuit in which the direction of the current reverses, such as a storage battery
circuit, the discharging current would be indicated on the scale above the zero
mark, due to the decrease of air pressure, while the charging current, which would
be in the opposite direction, would be indicated on the scale below the zero point,
due to increase of air pressure.
There are other ways of utilizing gas or air under pressure in this instrument
without modifying its general construction. The drawing indicates a dome C
covering the magnet and valve mechanism. When the air flows out of the
chamber c through the valve to the atmosphere, this dome merely serves to protect
the apparatus from dust and injury and will be provided at some point with a
small hole to permit the escaping air to flow out and avoid back pressure. This
dome, however may be hermetically sealed and a suction pump applied to it, to
exhaust the air therefrom and maintain a vacuum. Then by admitting atmo-
spheric or any other pressure at the point the operation of the instrument will
be substantially the same as before, except that the air will be drawn through
the valve instead of being forced through it. In either case there is a difference
of pressure on the opposite side of the valve, and this difference, which is con-
trolled by the valve, determines the level of the liquid column. It may be also
mentioned that the atmosphere may be excluded from the space above the liquid
in the stand pipe at the rear, in which event the gas pressure on the indicating
column would be resisted only by the difference in weight of the two columns.
That portion of the invention which relates to the altering of air or gas pressure
in accordance with variations in the current may be supplied in an instrument
whose indicating element is other than a liquid column, as, for instance, an
ordinary gas or air pressure gauge with an index.
I am
The object in using the cross-piece of the magnet is to concentrate all the lines
of force of the magnet in the small armature space occupied by the coil.
thereby able to use less power in the coil and a small, light spool.
Having now particularly described and ascertained the nature of my said
invention and in what manner same is to be performed, I declare that what
I claim is
1. The method of operating electrical indicators, which consists in determining
the level of a liquid column by the flow of air or gas and varying said flow in
accordance with the variations of current.
2. In an electrical indicator, the combination of means for maintaining a
difference of fluid pressure, an indicating element subjected to said difference of
fluid pressure and whose position is determined by the fluid pressure to which it
is subjected, and means whereby said difference of fluid pressure is varied in
accordance with variations in the condition of the current being indicated.
3. In an electrical indicator, the combination of a column of liquid whose level
indicates the condition of the current flowing, an air supply acting upon the
liquid to change its level, and means whereby the electric current varies the
pressure of the supply of air, substantially as described.

page_text: 4. In an electrical indicator, the combination of a column of liquid whose
level indicates the condition of the current flowing, an air supply acting upon
the liquid to change its level and a valve controlling the pressure of the supply
of air, said valve being operated by variations in the current flowing, substan-
tially as described.
5. In an electrical indicator, the combination of a column of liquid whose level
indicates the condition of the current flowing, and air supply acting upon the liquid
to change its level, a valve controlling the pressure of the supply, a coil of wire
through which the indicated current flows, a magnetic field of force in which
said coil is located, said valve being controlled by the movements of said coil,
substantially as described.
6. In an electrical indicator, the combination of an indicating element an air
supply actuating the same and means whereby the electric current varies the
pressure of the air supplied substantially as described.
7. In an electrical indicator, the combination of an indicating element, an air
supply actuating the same and a valve controlling the pressure of the supply of
air, said valve being operated by variations in the current flowing, substantially
as described.
8. In an electrical indicator, the combination of an indicating element, an
air supply actuating the same, a valve controlling the pressure of the supplied
air, a coil of wire through which the indicated current flows, a magnetic field of
force in which said coil is located, said valve being controlled by the movements
of said coil, substantially as described.
9. In an electrical indicator, the combination of an indicating element, an air
supply actuating the same, and an air flow resistance through which the air
passes, substantially as described.
10. In an electrical indicator, the combination of an indicating element, an air
supply actuating the same, an air flow resistance through which the air passes
and a pressure controlling device actuated by the indicated current and acting
upon the air between the air flow resistance and the indicating element, substan-
tially as described.
11. In an electrical indicator, the combination of a column of liquid whose level
is the indicating element, a source of air pressure acting upon the liquid to change
its level, an air flow resistance between the air source and the liquid, and an air
escape valve controlled by the current and located between the controlling device
and the liquid. substantially as described.
12. In an electrical indicator, the combination of an indicating element, an
air supply actuating the same, a capillary tube through the air passes and a
pressure-controlling device actuated by the indicated current. and acting upon
the air between the capillary tube and the indicating element, substantially as
described.
13. In an electrical indicator, the combination of an indicating column of
liquid, a source of air pressure acting upon said liquid, a capillary tube through
which the air passes to reach the liquid column, and an electrically operated air
escape valve located between the capillary tube and the liquid, substantially as
described.
14. In an electrical indicator, the combination of a U-shaped tube containing
a liquid, means for admitting air under pressure against the surface of the liquid
in one leg of the tube, and an electrically controlled valve for adjusting the air
pressure.
15. In an electrical indicator, the combination of an indicating element con-
sisting of a U-shape tube, the legs of which are of different diameters or capaci-
ties and contain a liquid, and electrically operated means for changing the level
of the liquid in the smaller leg, substantially as described.
16. In an electrical indicator, the combination of a column of liquid whose
level indicates the condition of the current flowing, an air supply acting upon
the liquid to change its level, a a valve controlling the pressure of the supply, a

page_text: counterbalanced arm resting upon the valve, and means whereby the pressure of
the weight upon the valve is varied in accordance with variation in current
flowing, substantially as described.
17. In an electrical indicator, the combination of an indicating element, an air
supply actuating the same, and a counterbalance valve controlling the pressure
of the supply of air, said valve being operated by variations in the current
flowing.
.
T
18: In an electrical indicator, the combination of an indicating element, an
air supply actuating the same, a valve controlling the pressure of the supplied air,
a spool carrying a coil of wire through which the indicated current flows, a
magnetic field of force in which said coil is located, a counterbalance for the
weight of the spool and coil, the valve being controlled by said spool and coil,
substantially as described.
t'
A
19. In an electrical indicator, the combination of means for creating a field of
force, a coil of wire and its spool located therein, a tilting arm by which said
spool and coil are carried, a counterweight therefor, a valve upon which the arm
bears, said valve controlling pressure of air, and an indicating element operated
by the pressure, substantially as described.
20. In an electrical indicator, the combination of means for creating a field
of force, a spool and coil located therein, a tilting arm carrying at one end the
spool and coil and at the other end a counterweight therefor, a pair of metallic
straps suspending said arm and permitting it to tilt, the terminals of said coil
being electrically connected respectively with the straps whereby current is con-
veyed through them to the coil, a valve upon which one end of the arm rests,
said valve controlling the pressure of fluid, and an indicating element operated
by said fluid pressure.
21. In an electrical indicator operated by differences of fluid pressure, a body
containing a fluid flow resistance consisting of a hollow plug adapted to be inserted
in and to seal a fluid chamber, the fluid flow resistance being contained inside the
plug and communicating through both ends thereof with the fluid chamber, sub-
stantially as described.
22. An electrical indicator, operated by the indicated current, substantially as
and by the means herein before described with reference to the accompanying
drawings.
Dated this 9th day of Antahan T 1000