IMPROVEMENTS IN INSTRUMENTS FOR MEASURING ELECTRIC CURRENTS, PARTLY APPLICABLE TO THERMOMETRIC REGULATORS
Year: 1881

page_text: LETTERS PATENT to John Toby Sprague, of Green Lane, Birmingham, in the
County of Warwick, Electrician for an Invention of "IMPROVEMENTS IN
INSTRUMENTS FOR MEASURING ELECTRIC CURRENTS, PARTLY APPLICABLE TO
THERMOMETRIC REGULATORS."
PROVISIONAL SPECIFICATION left by the said John Toby Sprague at the
Office of the Commissioners of Patents on the 12th October 1881.
JOHN TOBY SPRAGUE, of Green Lane, Birmingham, in the County of Warwick,
Electrician. " IMPROVEMENTS IN INSTRUMENTS FOR MEASURING ELECTRIO
CURRENTS, PARTLY APPLICABLE TO THERMOMETRIC REGULATORS."
My improvements consist chiefly in improved forms and modes of construction
of instruments, previously invented by myself, and described in my Patent No.
4762, A.D. 1878.
In instruments for indicating the currents passing at any moment and called
galvanometers, I use soft iron magnetic needles, in which the current itself induces
the magnetism. Instead of winding the wire or conductor in straight lines around
the frame as usual, I cause a part of the current to pass at right angles or other
suitable direction. I either bend the wire itself in portions of its course in the
required direction, or I make a special magnetizing circuit, either as a derivation
or as a continuation of the conductor. The wire of this circuit I wind in a
semicircular form so as to surround the space in which the needle plays, and so
that in any position of the needle the wire shall cross it at right angles.
In my Patent 4762 of 1878, I described an instrument of my Invention for
registering currents which have passed, consisting of a voltameter with a reversing
commutator and recording system actuated by the weight of metal transferred.
My present improvements consist in the use of a floating electrode instead of
suspended plates, and in special forms of construction adapted to practical uses.
construct my electrode in the form or on the principle of a hydrometer, so that
the weight thereof before it receives the deposit to be measured shall bring only
I

page_text: the lower part of its stem under the liquid. The stem I form of such size and
length that the weight of the deposit shall cause it to sink the desired depth. On
the stem I fix a projection connected to the metal, and abreast of its highest and
lowest positions I provide connections by which any convenient reversing arrange-
ment may be set in action, so as to alternately reverse the polar state of the
floating electrode, according as it reaches its higher or lower limit; each change of
reversal is recorded by a train of wheels as in my former apparatus.
In some cases instead of a reversing system I use an electrode, always moving
in one direction, and receiving the current in one direction. Such an electrode I
form as a cylinder with closed ends, and so adjusted as to just float in the liquid.
I fit this with an axis, and suspend it in a vessel containing the solution and
provided with divisions or screens coming as close as possible to the cylinder.
At the opposite sides of this cylinder I place the electrodes as close as possible
to the cylinder, which thus becomes an induced pair of electrodes, and will receive
deposits on one side and dissolve on the other.
This disturbance of equilibrium causes the cylinder to rotate and move an
indicating system. At proper intervals the two plates will require to be exchanged
in position, but the motion of the cylinder will be continuous. The same apparatus
may be caused to actuate a reverser at suitable intervals, and the cylinder to
alternately rotate in opposite directions, but by suitable gearing the indicating 1
train to be always moved in one direction.
As liquids vary in their electric resistance in a manner different from metals,
the ratio of shunt or derived circuits varies when composed of substances differently
affected by change of temperature.
Instead of using the decomposition cell as a derived circuit to the work to be
measured, I provide the cell itself with a set of shunts or derived circuits, so that
the combined system may form a circuit of low resistance, and be placed anywhero
as part of a conductor, through which the whole circuit shall pass. I make these
derived circuits partly of plates or rods of carbon, using also tubes of mercury,
and adjusting wires of metals, so combining the whole that the resistance of the
measuring cell and that of its shunts shall vary as nearly as possible in the same
ratio when the temperature varies.
In order to prevent the liquids freezing when exposed to low temperatures, I
construct a heating circuit of high resistance, so placed as to warm the solution,
and fitted with a commutator to close its circuit when the requisite temperature is
reached. I effect this by means of any suitable thermometer. The plan I prefer
consists of a bulb containing air, and with a stem plunged in a reservoir of
mercury. In this stem are a pair of wires insulated except towards their ends;
when the air contracts by cold the mercury rises and closes the circuit. This
apparatus may also be applied to other uses.
For some purposes, where registration is not required, I graduate the stem of
the floating electrode to show the quantity of electricity passed, or cause it by its
motion to indicate upon a scale; or for similar purposes I use a plate suspended to
a spring in such manner that its motion shall indicate any required work, and if
desired actuate a bell or a contact breaker to call attention or to shut off the
current from any desired apparatus; or I add suitable gearing to cause rapid motion
and cause a pointer to move over a scale by centrifugal action, and indicate the
current passing, as in a galvanometer.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Toby Sprague in the Great Seal Patent Office on the 12th
April 1882.
JOHN TOBY SPRAGUE, of Green Lane, Birmingham, in the County of Warwick.
Electrician. "IMPROVEMENTS IN INSTRUMENTS FOR MEASURING ELECTRIC
CURRENTS, PARTLY APPLICABLE TO THERMOMETRIC REGULATORS."
In my Patent No. 4762 of 1878, I described a galvanometer in which the
needles were of soft iron magnetized by the current itself.
My present improvement consists in so arranging the circuits as to obtain a more
perfect magnetism in these iron needles.
I effect this by employing a part of the current for magnetizing purposes, and
the rest as usual for deflection, which division of purposes may be effected in
several manners.
In order that my Invention may be fully understood, I will describe same by
reference to the Drawings hereto annexed.
Fig. 1 shows the circuit divided into two parts. d is the ordinary arrangement
of the conductor by which the needle is deflected; m is a frame with wire wound
upon it, and inserted in the frame and coils d. The wires upon m surround the
needle at the zero position, and magnetize it in a degree which is reduced as the
needle is deflected, while the magnetizing action of d increases. As the deflective
actions of these two sets of coils counteract each other, it is necessary to so propor-
tion their influence as to obtain the desired result. A similar effect may be less
perfectly attained by bending the wires of d twice at right angles, so that in part
of their course they cross the needle.
Fig. 2 shows another mode. m is a semicircular frame upon which the wire is
wound, so that in whatever position the needle may be, the wire crosses it at right
angles and tends to magnetize it, while the whole coil tends to draw the needle
towards its middle, as shown in dotted line. This circuit may be employed
alone to do the whole work, or inserted within an ordinary deflecting coil, as in
Fig. 1.
In both forms similar coils are employed at the other end of the needle, and two
such complete systems are connected with reverse actions, so as to obtain a
magnetic system in which external actions are neutralized. Such systems may be
mounted in any ordinary way, so as to use either vertical or horizontal dials.
In the Patent already mentioned I described an instrument for registering the
quantity of currents which have passed, consisting of an electro depositing cell
with a reversing commutator and a recording apparatus actuated by the weight of
metal transferred by the current. In that instrument the electrodes were suspended
by spiral springs or a balance arm, so as to rise and fall with the varying weight
of metal. My present. improvement consists in the use of a moving electrode,
the weight of which is supported by flotation, so that it may rise and
sink in the liquid by the change of. specific gravity due to the deposit or
removal of metal; that is to say, I make the electrode hollow or provide it with
floats, and fit it with a stem on the principle of the hydrometer, so that the
normal weight of the electrode shall just immerse the lower part of the stem,
while the immersion of the stem shall equipoise the metal as added; or I may so
adjust the electrode that it shall have a slight tendency to sink, and then attach
it to a spring or any convenient counterpoise, but so that these shall have to carry
only the varying quantity of metal deposited, and which it is the object of the
instrument to measure. Or it is evident I may reverse this plan, giving the
electrode a slight buoyancy, and resist its tendency to rise by similar means.

page_text: When I desire to send large currents through the apparatus I construct the
electrode of a float, to the lower surface of which are attached a number of parallel
plates all connected together, so as to act as an electrode of larger surface, and I
arrange these to move in the spaces of a similar system acting as a fixed electrode,
keeping the opposite surfaces as close together as possible with provision against
contact. To the movable electrode, however supported or constructed, I attach a
wire bent downwards so as to move freely in a tube containing mercury, by which
connection is made to the electrode; or I attach the tube of mercury to the
electrode, and provide a fixed wire over which it will move; or the wire connection
may move between rollers or brushes, or in other ways which will carry the current
to the electrode without passing through its supports. It is also evident that con-
nection may be made to a floating electrode by means of an open tube containing
mercury, and forming its stem through a fixed vertical wire passing down the
tube.
On the moving wire or on the stem I fix a metallic plate connected to the
electrode, which will play between two stops adjusted to the desired unit of
quantity, by means of which the reverser and recording apparatus will be actuated
each time the electrode rises or sinks to its limit of motion.
It is evident that an index upon the moving parts will traverse a scale and
indicate the intermediate degrees of deposit effected while the register shows the
total quantity. The various modes of construction are shown in Figure 3 to 7.
Fig. 3 shows a floating electrode of the simple hydrometer type, with connection
made to it by a wire playing in the stem. Such an apparatus with its stem
graduated may be used for experimental purposes without being provided with
reverser and recorder.
Fig. 4 shews a plate fitted with floats.
Fig. 5 shews section of a multiple surface electrode with its plates working
between those of the opposing electrode shewn in dotted lines.
Fig. 6 shews the systems of connection as applied to an electrode attached to
spiral springs c, c. The connecting wire k is shewn as playing between rollers on
one side, and carrying a mercury tube m on the other, to which is fixed wire +
carries the currents; 1 and 2 are the connections to the reverser in all the Figures.
Fig. 7 shews a construction adapted to cases, in which it is desired to examine
the actual working of currents, and to limit and control their action.
It consists of an electrode E (floating or otherwise), suspended from an angle g
carrying a pointer h which traverses a dial d, and besides indicating on a scale
will also actuate other appliances. The electrode E is connected in any of the
modes previously described, and the axle g is supported upon bearings or friction
rollers ff, which are connected to the positive terminal, so that the axle and
pointer may convey current where desired. The dial d is metallic, but insulated
from the apparatus, and provided with suitable connections to other apparatus,
and n is a clip spring which being placed at any desired part of the dial will convey
current to the connected apparatus upon the pointer making contact with it.
Other equivalent modes of effecting this result may be employed so as to ring an
alarm or cut off the current when the desired amount of work is done corresponding
to the part of the dial and scale upon which n is placed. The reverser may be
actuated by the pointer in a similar manner through stops attached to (but insulated
from) the dial at the beginning and end of the scale, and connected to the reverser.
Or a plate on the other end of the axle may play between two properly adjusted
stops as shewn.
The resistance to motion may be a helical spring or a counterpoise, as at c,
dipping into the liquid, or into a separate tube. Or the electrode may be supported
by spiral springs or a counterpoise balance, and a lever arm moved by it may be
used for the same purposes as the pointer h shewn. In order to increase the utility
of the meters, I use graduations adapted to any desired work; thus I form a scale
which, by reading of, say, one minute, will give the rate of current passing, or I
graduate the scale to shew. the work done in. ounces of silver, pennyweights of gold,

page_text: -
-
and
etc. Any convenient reversing commutator actuated by the current may be employed,
but it is important that the form used should offer as little resistance as may be to
the current, especially when large currents are to be passed. For this reason
I prefer one in which the connection is made by stout wires plunging in mercury.
Figs. 8 and 9 shew such a reverser. Bearings shewn + and are connected to the
terminals, and provided with mercury cups (not shown), in which stout wires from
the bars A, C, dip. These metal bars A, C, are supported by an insulating axis B,
and terminate in wires which dip in mercury cup 3 and 4 when inclined as shown,
and in cup 5 and 6 when in the opposite position. The cups are connected in
pairs crosswise, 3 and 6 together, and 4 and 5, and one pair is connected to the
electrode E, and the other to electrode F, which are thus connected to the + or
terminals, according to the inclination of A, C. These bars A, C, carry the
magnets N, S, N, S, which are insulated from them, and beneath these are electro-
magnets which attract them when actuated by current passing. The wires of these
magnets are connected so that M³ and M act together, as do M³ and M*, but the
iron cores are arranged so that each active coil shall induce opposite polarities in
the cores of the other pair, so as to cause them to repel the other magnet
then in contact with them while the active magnet attracts the magnet N, S,
over itself. If iron armatures are used in place of permanent magnets N, S, the
cores of each pair would be connected together, instead of as shewn, as in
that case only attraction would be employed. The wires of M' and M² arranged
to develope south polarity under n, are connected one end to bearing
the other to a stud 8, and thence to contact stop 1, those of M 3 and M 4 being
similarly connected to + and stop 2. Over the studs 8, 8, a plate of metal is
attached to the bar A or C, so that when the frame is drawn over these touch, and
the effect is to place both ends of the wires of the electro magnets in contact. The
whole action may be thus traced. As shewn, the current asses from + by A
and 3 to E (which is the moving electrode now acting as anode and dissolving)
across the solution to F, the fixed electrode, and by 4 to C and As E dissolves
it rises and closes contact with stop 1, thus opening a second return path as a
derivation from the liquid, which passing through M 1 and 2 to -, energises the
magnet, and drawing the frame over reverses the relations of E and F, and at the
same time by short circuiting the coils of the magnet at 8 prevents their reversal,
and also prevents a spark being formed at 1 when contact is broken. Now E
begins to receive deposit, and sinking breaks the temporary derived circuit, and
ultimately in reaching stop 2 repeats the process. As this apparatus is shewn the
stops 8, 8, are not absolutely essential, because as soon as the reversal occurs the
ends of the wires of the electro-magnets are in short circuit at stop 1; but in other
arrangements of the circuits they are of more importance, and in any case they
afford protection to the contact at 1. This short circuiting demagnetises the electro-
magnets immediately after reversal, so that the completion of the movement is effected
by the acquired momentum and the attraction of the magnets N, S. As during
the existence of the derived circuit part of the current does not effect deposit, an
allowance must be made for this in the quantity of metal taken as unit. The
recording apparatus may be actuated in various ways, as by a separate electro-
magnet. One mode is shewn in principle in Fig. 10. The axis B of Fig. 8 and 9
carries a wheel or cam upon which rests a lever, with a friction wheel as shewn ;
each movement of the rocking frame raises this lever and thus moves the first wheel
of the recording train one tooth.
11
In order to prevent breaks in the main circuit and sparks in the cups these are
made as shown (Fig. 11), and so adjusted as to height that at the moment when the
frame is horizontal all four points are just in contact with the mercury. When
shunts are employed with the meter this is not necessary, and then a temporary
break may intervene so as to prolong the magnetisation of the electro magnets
during the extra current.
If it is desired to avoid the use of mercury, I replace the moving system described
by an armature or magnet mounted on a pivot so as to move freely in a horizontal

page_text: plane and arrange the magnets as this change requires. Fig. 12 shows the principle
of this modification. I is one end of the armature carrying an insulated frame f
with an axle on which runs a number of metal discs d. The mercury cups are
replaced by metal plates as shewn, over which the discs run and connect A to 3
or 5 and C to 4 or 6, according to the positions of I, by bridging over the spaces.
It is obvious that many variations of construction are possible. Thus permanent
magnets may replace the electro-magnets and electro magnets be used on the
rocking frame; or the frame may be placed vertically instead of horizontally, or a
single magnetic bar, or an electro-magnet with two distant circuits may be placed
parallel with the conducting bars instead of across them, and only two electro
magnetic coils be employed instead of four; or the electro magnets instead of
acting separately may be so wound with two distinct circuits that they may all be
used as desired and given reverse polarity at the proper periods. Also the magnet
wires may be inserted in the metercircuit, or may in some cases form part of the
shunt circuits to be hereafter described.
-
In some cases, instead of a pair of electrodes alternately acting as anode and
cathode with an automatic reverser, I use an electrode always moving in one
direction. If a piece of metal not connected to the circuit is suspended in an
electrolytic cell between a pair of electrodes, a part of the current is diverted from
the solution to the metal owing to its greater conductivity, and one end of the
metal dissolves while the other receives a deposit. Such a piece of metal in these
conditions I call an induced electrode. I construct an electrolytic cell with a pair
of electrodes, and mount between them upon suitable bearings an induced electrode
in the form of a cylinder, so that it can rotate freely when the deposit on one side
and solution of the other alters its centre of gravity. In order to reduce friction,
I make the cylinder hollow, and close its ends with wood or other non-conductor
prepared to resist adhesion of the liquid, so that the cylinder shall float at the
proper level, and have no weight of its own upon its axis. The bearings may also
be mounted on a sliding frame, and may be supported on a float so as to adjust
themselves to variation of the liquid level. A worm or cng wheel on the axis
transmits motion by a vertical rod to a set of wheels which record the rotation
produced. The value of this rotation must be ascertained experimentally, and will
depend upon the diameter of the cylinder and area of the liquid conducting path.
Figure 13 shows the apparatus; + and are the electrodes in the containing
vessel V; C is the induced electrode cylinder; S is a screw of non-metallic
material which limits the direct path through the liquid so as to force as much as
possible of the current into C, leaving space as necessary for circulation of the
liquid. As shown it is intended to serve also as a float, to carry the bearings and
the cylinder; but in this as in the other Figures, I do not show mechanical details,
which are well understood matters capable of great variation, and do not form part
my Invention. This apparatus involves the necessity for an occasional exchange
of the electrodes + and -. But these may be replaced by an external cylinder
composed of a number of insulated copper strips, with suitable contacts provided
for passing the currents into those plates which face opposite sides of the induced
electrode. This outer cylinder may be rotated by clockwork or an electromotor, so
as to regularly bring the strips into operation in succession. In most instruments for
measuring large currents it is customary to use shunts, so as to send only a definite
part of the current into the actual measuring apparatus, and the resistance of different
substances is affected in different ratios by external changes of temperature, and
their actual temperatures are also differently altered by the same current, so that
it is generally necessary to make the measuring and shunt circuits of the same
material. But in meters of which an electrolytic action forms part, this is not
convenient. An electrolyte may be used in the shunt circuit provided arrangements
are made by which the current may be frequently reversed so as to maintain the
electrodes intact. But as metals and liquids vary in their resistance in opposite
ratios, they can give correct results only at the temperature of adjustment
are used as shunts to each other, I therefore use as shunts such materials as
of
they

page_text: singly or combined will vary in the same manner as the circuit containing the
electrolyte graphite (by which I mean any conducting carbon), alters its resistance
in the same direction as liquids do, and as there are many different qualities, I
select such as vary with temperature as nearly as possible in the same degree as
the meter circuit. Mercury varies in the opposite direction to liquids but to an
extent much smaller than copper does, as do German silver and other alloys. The
resistance of the meter circuit is also compound, consisting of the electrolyte which
lowers in resistance as temperature rises, and of the metallic electrodes, conductors,
etc., which rise in resistance as temperature rises, so that the sum of these may be
brought (by adding to or reducing the quantity of one of these portions) to
agreement with any desired variation. As the relations of the two circuits
(meter and shunt) may vary indefinitely, it is impossible to fix upon any exact
relation.
But I form the shunt circuit of graphite, and if necessary add thereto a tube of
mercury or a wire of German silver, as needed, to obtain equal ratios of variation.
Thus I may have
Liquid (large), copper (small +), shunt graphite > .
Liquid (small), copper (large +), shunt German silver.
Liquid and metal balance, shunt graphite, and German silver.
But whatever the materials thus selected and balanced to obtain circuits affected
alike by similar temperatures, I so proportion the quantity of material employed in
view of the respective specific heats that the currents actually passing in the several
circuits shall produce in each circuit and in each component of each circuit the
same change of temperature.
This is not the case in shunts as usually employed, where a larger circuit is
commonly passed through a smaller mass of material than that contained in the
circuit conveying the smaller current. In order to prevent evaporation and change
of conditions consequent thereon, I enclose the liquid in a case which is as nearly
as possible air tight, and in some cases I cover it with a layer of any oil (such as
some qualities of resin oil) which does not thicken by exposure to air, and which is
not so viscid as to interfere with the essential motions.
The meter ought to be so placed as to guard against freezing of the liquid, which
may also be resisted to some extent by addition of glycerine (but this is not
desirable). But where exposed to this danger I use a warming apparatus consisting
of a thin glass tube, as shewn (Fig. 14), upon which a fine platinum wire is wound,
and enclosed in another thin glass tube melted or cemented to the other so as to
enclose the wire in a narrow space, which may contain water or other non-
conducting liquid to distribute the heat developed by the passage of a current in
the wire, the ends of which project and are connected to insulated conductors, Bo
that convection currents are set up in the liquid. This apparatus may be usefully
employed at all times with a small part of the current passing through it to cause
circulation in the liquid and resist the tendency of the formation of strata of dense
solution at the lower part.
For temporary heating purposes current is passed into the heater whenever the
temperature lowers to a fixed degree by the thermo-regulator, shewn (Fig. 15). This
is an air thermometer consisting of a bulb and U tube with a neck for the insertion
of wires and one of which connects to mercury contained in the tube, while
the other is insulated except at its point. As the air contracts by cold the mercury
rises, till at the desired degree it reaches the point of -, and closes the circuit to
the heater.
This form of air thermometer may be applied to fire alarms, incubators, and other
purposes, and for some of these purposes a third wire a is employed, which will
close a circuit when the temperature rises and expands the air in the bulb to a
determined limit, as does when the temperature falls. For use in the meter I
connect of Fig. 15 to the entering terminal of the meter case, and to one end
of the heater coil, the other end of which may be connected to the exit terminal of
the meter, so as to secure passage of current at any time, even if the liquid were
-

page_text: frozen; or it may be connected to the electrolyte circuit, so as to pass through the
measuring cell.
Having now particularly described and ascertained the nature of the said
Invention, and in what manner the same is to be performed or put in practice, I
hereby declare that I claim,-
1. The arrangements of galvanometer circuits, substantially as described.
2. The use in electrolytic meters of an electrode supported or chiefly supported
by their own buoyancy, substantially as described.
3. The use in electrolytic meters of induced electrodes rotating in consequence of
the action, substantially as described.
4. The various modes of connection to electrodes and construction of electrolytic
meters, substantially as described.
5. The use with electrolytic meters of the reversing commutators, substantially
as described.
6. The combination with an electrical measuring apparatus of adjustable contacts
for actuating other appliances when a desired quantity of work is done, substantially
as described.
7. The use with electrolytic meters of shunts of graphite, German silver, or other
metallic alloy, and so forth, adjusted to vary in resistance as the meter circuit varies,
substantially as described.
8. The use with electrolytic meters of scales shewing work done in special
measures of quantity, such as the equivalent ounces of silver, and so forth,
substantially as described.
9. The combination of heater and thermo-regulator for controlling temperature,
substantially as described.
In witness whereof, I, the said John Toby Sprague, have hereunto set my
hand and seal, this Eleventh day of April, in the year of our Lord One
thousand eight hundred and eighty-two.
Witness,
T. MORGAN,
21, Cockspur Street,
Charing Cross.
JOHN T. SPRAGUE.
(L.S.)