Improvements in Electric Meters.
Year: 1890

page_text: Date of Application, 26th Feb., 1890
Complete Specification Left, 26th Nov., 1890-Accepted, 21st Feb., 1891
Improvements in Electric Meters.
I, SEBASTIAN ZIANI DE FERRANTI, of 120, Fellows Road, Hampstead, in the
County of Middlesex, Electrician, do hereby declare the nature of this invention
to be as follows:-
-
This invention has for its object improvements in electrical meters. Electrical
meters such as are described in the Specification of former Patents granted to me
Nos. 592683 and 701% in which a bath of mercury is set into a rotation by a passing
current and in which the rotation of the mercury is recorded by causing it to impart
a revolving motion to an axis whose revolutions are recorded by recording
mechanism. I now form with a main coil through which the current to be measured
passes and an additional coil through which a branch circuit from the mains is
allowed to pass as described in the Specification No. 70187 and these two coils I
place one above the other. Preferably I form the conductor of the main coil of a
strip of metal equal in width to the depth of the coil and a portion of the additional
coil I wind with non-inductive winding as I am thereby better able to adjust the
meter to at all times indicate correctly whether much or little current is passing.
Similarly in other meters in which a similar additional or shunt coil is used part of
it may be wound non-inductively.
Across the centre of the space surrounded by the coils I place a shallow mercury
bath. I form it of two horizontal discs of insulating material (preferably vulcanized
fibre) at a slight distance apart one above the other. Around their outer circum-
ference and between them is a ring with inclined sides which bear against
outwardly turned edges of the dises and make a tight joint all around them. This
ring is split across and its ends held together by a clamping screw or screws
with insulated material between them to prevent current from circulating in the
ring.
The coils are enclosed between two sets of annular troughs formed of thin
sheet iron - a number of troughs are used one inside the other with thin insulation
between. On the outer side and at the top and bottom of the annular casing so
formed some of the troughs are cut away so that the amount of iron may be the
same on the interior as on the exterior of the coils.
Where the edges of the thin iron troughs come above and below the mercury
bath they are cut away to fit to the bath-and serve to hold the two discs of
which it is formed lightly against the ring which surrounds their circumference.
the
At the centre of each disc is a hole through which a bevelled headed screw of
copper or conducting metal passes and is screwed into a gun metal or other cou-
ducting plate made to bear respectively against the top and bottom of
assemblage of iron troughs with insulating material interposed between them. These
plates are drawn together and made to clamp the troughs between them by screw
bolts passed through them and through holes formed through the troughs. By
thus drawing together the upper and lower assemblages of troughs the two discs of
the mercury bath are made to fit tightly to the ring which surrounds the outer
circumference and form tight joints and by screwing upwards and downwards the
two screws which pass through the centre of the dises tight joints are made at the
centre of the bath.
The top screw is hollow and the spindle of the disc which is immersed in the
mercury rises up through the hollow to the recording mechanism. The recording
mechanism is contained in a casing which is held down to the top clamp plate. The

page_text: cylindrical sides of the casing are continued downwards somewhat below its bottom
plate and this prolongation of the sides is flanged outwards and is held to the top
clamp plate by the heads of the screws which draw the two clamp plates together.
When the meter is to be carried from place to place the mercury may be poured
out from the bath through a small hole formed through the downward prolongation
above mentioned and when the meter has been fixed in place the bath may be again
filled through the same hole.
The screws which draw together the two clamp plates pass down between the
inner side of the conducting coils and the troughs-a space being left between this
side of the coils and the innermost trough to admit of this.
A vertical division is formed right across the annular casing formed by the thin
iron troughs at one side the division in the outer circumference of the casing is
utilized by placing in it the conductor which is to conduct current to the outer end
of the main coil. On the opposite side the conductor to the outer end of the shunt
or additional coil is made to lie in the division.
The bottom gun metal clip plate is embedded in sulphur in the centre of a tray
which may be of cast iron--and is formed so that it can be fixed down to any
support by screws lying in inclined holes in the circumference.
The bottom gun metal clip plate is formed with a socket in which the end of one
of the pair of conductors of the supply main may be attached.
The end of the other of the pair of conductors of the supply main is similarly
clamped in a socket formed in a conducting bar which is also embedded in the
sulphur. At the opposite end of the bar is another socket in which the end of one
of the conductors of the main to be supplied is held. This bar is attached to the
outer end of the main coil-the inner end of this coil is attached to the ring which
surrounds the mercury bath. In this way when current passes to the bottom clamp
plate from the supply inain it passes by the clamp screws to the top clamp plate
and from both clamp plates through the screws which pass to the centre of the
mercury bath and through the mercury to the outer ring of the mercury bath and
from there to the inner end of the main coil and through the coil to the conductor
bar which is attached to it and so to the main to be supplied.
The outer end of the additional or shunt coil is connected to the conductor bar
which has one of the conductors of the supply main and of the main to be supplied
attached to it.
The inner end of the shunt coil is connected to the outer ring of the mercury
bath.
When a meter so constructed has been fixed in place I enclose it by a casing
which at the bottom overlaps the cast iron pan or bed plate and I secure it to this
bed plate by a screw passed horizontally through it and seal over the head of
the screw. The outer case is provided with a glazed aperture at the top through
which the dial of the recording mechanism can be seen.
In the commercial use of a meter or meters which are designed for measuring
the current supplied to customers by a supplying company it will be necessary
that these meters should be sent to a standardising authority in order that they
may check the accuracy of the meter, or place a constant thereon by which the
meter can be read correctly. After this has been done it is evident that their seal
or mark must be so affixed to the meter that the meter shall be in every way
protected against baving its motor power or constant varied by design or accident,
even in transit, and in the installing of the meter, viz., connecting it with the wires
through which the current is supplied, it is absolutely necessary that after the seal
has been placed that the above conditions do not in any way alter the accuracy of
its recording power.
After the meter has been installed, i.e., put into the customer's house and con-
nected to the supply and delivery wires, it is necessary that the company
supplying the current should then be protected against the consumers or any
other person wilfully or negligently altering the working of the meter. This

page_text: alteration of the customer might be made by short circuiting the meter by
baring the wires close to the meter or by putting a 'wire into the meter along-
side the supply wire, and so diverting a portion of the current. It is further
necessary that the screws by which the wires are fixed in the terminals of the
neter should not be able to be got at. Now my object principally is to so
construct all forms of electricity meter or instruments which are to be standardised
by authority and then installed for commercial use, in such a manner that it
entirely fulfils the whole of the above conditions. I also construct them in such
manner that nothing can be done which can make a meter register more than
it has been standardised to do, but that any errors make it register less.
The meter described in the first part of this Specification may be taken as good
example of one way in which I can accomplish this object when these means are
applied to my own form of mercury meter. When however such a meter is em-
ployed as the well known type of Frager meter which consists of a dynomometer
varying the position of an engaging arm which is driven by a clock and records
more or less current as more or less current passes, the conditions have to be some-
what modified. In this case it is desirable that the meter should be constructed in
every way with all its parts balanced, and that all the parts which effect the
accuracy of its constant should be so arranged and encased that a seal or lock or
stamp may be fixed by the standardising authority which will prevent these parts
of the meter being in any way interfered with. The second matter of importance
is in this case notwithstanding the balancing of the parts that the meter should be
levelled in order to run with the least, possible friction and wear and for this
purpose level the base of the meter by means of levelling screws, the heads of
These screws are so
which come within the second case which protects the meters.
arranged that they may be used for levelling the meter from the inside, then an
ordinary wood screw may be put through their centre, which holds them down and
with them the meter to the table or shelf on which it is fixed, and the outer
case then added which prevents either the first case being got at or the terminals
or the levelling screws or any other parts by which the ineter could be affected.
Similar arrangements of levelling and retaining screws may be used with other forms
of meter which require to be retained in one fixed position.
The indicator dials of the meters may or may not be protected by a glass which
is. held down by the sealing of the standardising authority-it is not however
absolutely necessary to protect the hands, but the train itself it must be absolutely
necessary to protect, i.e., one must not be able to alter the train which is put
on the meter or any of the parts of it, but it is not absolutely necessary to seal the
hands as when a meter is put into work and has a second case sealed on it,
the position of the hands can be read through a glazed aperture in this
second case.
In the form of meter known as the Aron meter two pendulums are allowed to
vibrate, both of them actuated by the spring of a clock or by separate springs. In
this case two courses might be adopted, the maximum of the meter and the electrical
coil might be so encased that no alteration would be made to these parts, the
pendulum, terminals and fixings of the meter might be left for the second case for
On the other
sealing by the company supplying the current through the meter.
hand it might be desirable that the meter should be arranged with the mechanism,
the pendulum, the electrical coils and everything except the arrangements for fixing
the meters against the wall, and fixing the wires into the terminals should be
protected by the first case and these other things protected by the second case and
stamp and lock supplied by the company supplying the current.
L 1800

page_text: COMPLETE SPECIFICATION.
Improvements in Electric Meters.
I, SEBASTIAN ZIANI DE FERRANTI, of 120, Fellows Road, Hampstead, in the
County of Middlesex, Electrician, 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 has for its object improvements in electrical meters. The im-
provements relate first to electrical meters such as are described in the Specification
of former Patents granted to me Nos. 592683 and 701% in which a bath of mercury
is set into rotation by a passing current and in which the rotation of the mercury is
recorded by causing it to impart a revolving motion to an axis whose revolutions
are recorded by recording mechanism.
My improvements in this kind of meter are shewn in the drawings hereunto
annexed.
Figure 1 is a vertical section, Figure 2 a side elevation and Figure 3 a plan of
the meter. Figure 4 is another side elevation with the outer case in section.
Figure 5 is a horizontal section through the line A B Figure 1. Figure 6 a
horizontal section through the line C D, Figure 1.
Figure 7 is a plan, Figure 8 a side elevation and Figure 9 a cross section of a
clip ring forming part of the mercury bath.
Figure 10 is a section of one of the iron troughs or casings by which the conductor
coils are surrounded.
Figure 10 an underside view of the upper portion of the annular casing-and
Figure 10b a plan of the lower portion of the annular casing.
Figure 11 is a plan view, Figures 12 and 13 are end views and Figure 14 a cross
section of the lower clip plate between which and an upper clip plate the iron
troughs or casings are held.
Figure 15 is a plan and Figure 16 a cross section of the upper clip plate.
Figure 17 is a plan and Figure 18 an edge view of a conducting bar to which
one of the pair of supply wires and one of the pair of wires to be supplied are
connected.
Figure 19 is a plan and Figure 20 an edge view of a conductor bar to which the
other wire to be supplied is coupled.
Figure 21 is a plan and Figure 22 a vertical section of the base of the meter.
Figure 23 is a vertical section shewing a levelling and holding down screw
attachment.
The meter is formed with a main coil A through which the current to be
measured passes and an additional coil B through which a branch circuit from the
mains is allowed. to pass as described in the Specification No. 70187 and these two
coils I place one above the other. Preferably I form the conductor of the main
coil of a strip of metal equal in width to the depth of the coil and a portion of the
additional coil I wind with non-inductive winding as I am thereby better able to
.adjust the meter to at all times indicate correctly whether much or little current is
passing. Similarly in other meters in which a similar additional or shunt coil is used
part of it may be wound non-inductively. The portion wound with non-inductive
winding serves only for giving the required resistance in the shunt circuit, thus after
I have wound round the correct number of fine copper wire turns I then wind on
outside it the proper length of higher resistance wire one half in one direction and
the other in the opposite direction so that this latter winding produces no effect in
the starting of the meter but only acts to throttle the amount of current that can
pass through the winding.
Across the centre of the space surrounded by the coils I place a shallow mercury
bath. I form it of two horizontal discs C of insulating material (preferably
vulcanised fibre) at a slight distance apart one above the other. Around their
outer circumference and between them is a ring C¹ with inclined sides which

page_text: bear against outwardly turned edges of the discs and make a tight joint all
around them. This ring is split across as seen in Figures 7, 8 and 9 and its ends
held together by clamping screws C2 with insulated material between them to
prevent current from circulating in the ring.
The coils are enclosed between two sets of annular troughs D formed of thin
sheet iron-a number of troughs are used one inside the other and it may be with
thin insulation between. One of the assemblages of troughs is shewn separately
in section at Figure 10-I make these troughs by pressing them to shape from
sheets of tin plate and when the several troughs which are to go one inside the
other have been pressed to the required form I heat them sufficiently to cause the
tin coverings of the plates to unite together so that when the assemblage of troughs
is allowed to cool the whole becomes solidified into one solid block. In place of
using tin as the soldering or uniting material shellac or such like adhesive material
might be used. On the outer side and at the top and bottom of the annular casing
so formed some of the troughs are afterwards cut away as shewn at Figures 1
and 10 so that the amount of iron may be the same on the interior as on the
exterior of the coils or not as may be found necessary.
Where the edges of the thin iron troughs come above and below the mercury
bath they are also cut away to fit to the bath-and serve to hold the two
discs C of which it is formed lightly against the ring C¹ which surrounds their
circumference.
At the centre of each disc C is a hole through which a bevelled headed screw E
of copper or conducting metal passes and is screwed into a gun metal or other
conducting plate made to bear respectively against the top and bottom of the
assemblage of iron troughs with insulating material interposed between them-
the upper plate is marked G. and the lower one H. These plates are drawn
together and made to clamp the troughs between them by screw bolts I passed
through them and through holes formed through the troughs. By thus drawing
together the upper and lower assemblages of troughs the two discs of the mercury
bath are made to fit tightly to the ring C¹ which surrounds the baths outer
circumference and form tight joints and by screwing upwards and downwards the
two screws E which pass through the centre of the discs tight joints are made at
the centre of the bath.
The top screw is hollow and the spindle J of the disc J¹ which is immersed in
the mercury rises up through the hollow to the recording mechanism. The
recording mechanism is contained in a casing K which is held down to the top
clamp plate G. The cylindrical sides of the casing are continued downwards
somewhat below its bottom plate and this prolongation of the sides is flanged
outwards and is held to the top clamp plate as shewn in Figure 1 by the heads
of the screws I which draw the two clamp plates together. When the meter is
to be carried from place to place the mercury may be poured out from the bath
through a small hole L, see Figure 1, formed through the downward prolongation
above mentioned and when the ineter has been fixed in place the bath may be
again filled through the same hole.
The screws I which draw together the two clamp plates G and H pass down
between the inner side of the conducting coils A and B and the troughs—a
space being left between this side of the coils and the innermost trough to
admit of this.
A vertical division is formed across one side of the annular casing formed by
the thin iron troughs. The vertical divisions serve to prevent circular currents
being set up in the casing. A vertical division is also formed partially through the
opposite side of the trough. At one side the vertical division is utilised by placing
in it as shewn in Figures 2 and 5 the conductor M which is to conduct current to
the outer end of the main coil. The conductor M is led down and secured to a
bar N shewn separately at Figures 19 and 20 and which is embedded in sulphur
in the cast iron. base O of the meter as shewn in Figures 2 and 6. The bar N is
as shewn formed with a socket N¹ to receive one of the conducting wires leading

page_text: to or from the meter. On the opposite side of the casing the conductor to the
outer end of the shunt or additional coil B is made to lie in the division.
The bottom gun metal clip plate H is also embedded in sulphur in the centre of
the cast iron base O. It is formed with a socket H₁ in which the end of one of the
pair of conductors of the supply main may be attached.
The end of the other of the pair of conductors of the supply main is similarly
clamped in a socket P¹ formed in a conducting bar P which is also embedded in
the sulphur. This bar is shewn separately at Figures 17 and 18. At the opposite
end of the bar is another socket P2 in which the end of one of the conductors of the
main to be supplied is held. In this way when current passes to the bottom clamp
plate H from the supply main it passes by the clamp screws I to the top clamp
plate G and from both clamp plates through the screws E which pass to the centre
of the mercury bath and through the mercury to the outer ring C¹ of the mercury
bath and from there to the inner end of the main coil A and through the coil to the
conductor bar M which is attached to it and so to the bar N and the main to be
supplied.
The outer end of the additional or shunt coil B is connected by the conductor Q
to the conductor P which has one end of the supply main and of the main to be
supplied attached to it.
The inner end of the shunt coil B is connected to the outer ring C¹ of the
mercury bath.
The cast iron base is as shewn formed so that it can be fixed down to any support
by screws R lying in inclined holes in the circumference. When a meter so
which at the bottom
constructed has been fixed in place I enclose it by a casing
overlaps the cast iron bed plate and I secure it to this bed plate by a screw T
The outer case
passed horizontally through it and seal over the head of the screw.
is provided with a glazed aperture S¹ at the top through which the dial of the
revolving mechanism can be seen.
In place of the conducting wires being held within sockets by locking screws as
shewn in the drawings other means for securely retaining the ends of the conductors
within the sockets might be employed for example they might be formed with an
enlarged head and be held into the socket by a screwed cap screwed on to the exterior
of the socket.
In the drawings also I have only shewn the meter as formed for receiving the
If however concentric conductors were used for the
ends of separate conductors.
supply main then the socket for receiving the end of the inner conductor would
have to be placed centrally within the socket for receiving the end of the outer
conductor.
In the commercial use of a meter or meters which are designed for measuring the
current supplied to customers by a supplying company it will be necessary that
these meters should be sent to a standardising authority in order that they may
check the accuracy of the meter, or place a constant thereon by which the meter
can be read correctly. After this has been done it is evident that their seal or
mark must be so affixed to the meter that the meter-shall be in every way protected
"against having its motor power or constant varied by design or accident, even in
transit, and in the installing of the meter, viz., connecting it with the wires through
which the current is supplied, it is absolutely necessary that after the seal has been
placed that the above conditions do not in any way alter the accuracy of its
recording power.
-
•
After the meter has been installed, i.e., put into the customer's house and con-
nected to the supply and delivery wires, it is necessary that the company supplying
the current should then be protected against the consumers, or any other person
This alteration of the
wilfully or negligently altering the working of the meter.
customer might be made by short circuiting the meter by baring the wires close to
the meter or by putting a wire into the meter alongside the supply wire, and so
It is further necessary that the screws by
diverting a portion of the current.

page_text: at.
which the wires are fixed in the terminals of the meter should not be able to be got
Now my object principally is to so construct all forms of electricity meter or
instruments which are to be standardised by authority and then installed for com-
mercial use in such a manner that it entirely fulfils the whole of the above
conditions. I also construct them in such manner that nothing can be done which
can make a meter register more than it has been standardised to do, but that any
errors make it register less.
The meter described in the first part of this Specification may be taken as a
good example of one way in which I can accomplish this object when these means
are applied to my own form of mercury meter. When however such a meter is
employed as the well known type of Frager meter which consists of a dynamometer
varying the position of an engaging arm which is driven by a clock and records
more or less current as more or less current passes, the conditions have to be some-
what modified. In this case it is desirable that the meter should be constructed in
every way with the moving arm and all its moving parts balanced so that no part
is capable of being moved by gravity and where gravity was previously used to
effect the required movement of the parts to effect the movement by springs, and
further that all the parts which effect the accuracy of its constant should be so
arranged and encased that a seal or lock or stamp may be fixed by the standardising
authority which will prevent these parts of the meter being in any way interfered
with. The second inatter of importance is in this case notwithstanding the
balancing of the parts that the meter should be levelled in order to run with
the least possible friction and wear and for this purpose I level the base of the
meter by means of levelling screws, the heads of which come within the second
case which protects the meters. These screws are so arranged that they may be
used for levelling the meter from the inside, and may then if desired be locked by
a pin or other suitable stop then an ordinary wood screw may be put through their
centre as shewn at Figure 23 which holds them down and with them the meter to
the table or shelf on which it is fixed, and the outer case then added which prevents
either the first case being got at or the terminals of the levelling screws or any
other parts by which the meter could be affected. Similar arrangements of levelling
and retaining screws may be used with other forms of meter or instruments which
require to be levelled and retained in one fixed position.
The indicator dials of the meters may or may not be protected by a glass which
is held down by the sealing of the standardising authority it is not however
absolutely necessary to protect the hands, but the train itself it must be absolutely
necessary to protect, i.e., one must not be able to alter the train which is put on the
meter or any of the parts of it, but it is not absolutely necessary to seal the hands
as when a meter is put into work and has a second case sealed on it, the position of
the hands can be read through a glazed aperture in this second case.
In the form of meter known as the Aron meter two pendulums are allowed to
vibrate, both of them actuated by the spring of a clock or by separate springs.
In this case two courses might be adopted, the mechanism of the meter and the
electrical coil might be so encased that no alteration could be made to these parts,
the pendulum, terminals and fixings of the meter might be left for the second case
On the other
for sealing by the company supplying the current through the meter.
hand it might be desirable that the meter should be arranged so that the mechanism,
the pendulum, the electrical coils and everything except the arrangements for fixing
the ineters against the wall, and fixing the wires into the terminals is protected
by the first case and these other things protected by the second case and stamp and
lock supplied by the company supplying the current, or they might be constructed
with a case with two divisions one containing one part and the other the other part.
Similarly with other meters the whole of the mechanism may be contained
within a casing capable of being sealed after standardising and with a separate
casing or casings that can be locked or sealed by the company supplying the
current for protecting the junctions of the supply and delivery wires with the
conductors which pass through the meter,

page_text: Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In electric meters in which there is a shunt circuit passing through an
additional coil for the purpose of assisting in the starting of the meter into
movement the winding of part of such additional coil with non-inductive winding.
2. The construction of the mercury bath of meters of that class in which a bath
of mercury is set into rotation by a passing current, of two discs of insulating
material one above the other and at a slight distance apart with a clip ring
enclosing the space between them and with the discs held at their circumference
against the ring by iron clamping blocks within which are enclosed the magnetising
coils through which the current to be measured passes and held at their centre
against the clamping blocks by screws passed upwards and downwards through the
discs one screwed into a plate above and the other into a plate below the iron
clamping blocks.
3. The construction of the iron casing which encloses the magnetising coils in
two or more parts each formed from a series of annular troughs or dished plates
pressed to the required form from sheets of tin plate and which are placed one
within the other and then heated to solder them all together.
4. The construction of the iron clamping blocks each from a series of annular
troughs or dished plates of thin sheet iron pressed to the required form and placed
one within the other and held together with adhesive material such for example as
shellac.
5. The construction of the iron clamping blocks casing which encloses the
magnetising coils in two or more parts each formed from a series of thin iron
plates pressed to the form of an annular trough and placed one within the other.
6. The construction of the iron casing which encloses the magnetising coils each
from a series of thin iron plates pressed to the form of an annular trough and
placed one within the other and with some of the outer troughs cut away on their
outer side so that the amount of iron may be the same on the interior as on the
exterior of the coils.
7. The construction of the casing for enclosing the magnetising coils of an upper
and a lower annular laminated iron trough each divided or partly divided by a
transverse division.
8. The construction of electric meters substantially as herein before described
and illustrated in the drawings annexed.
9. The construction of electric meters in which there is a periodical gauging and
recording of the amount of current passing substantially in the manner herein before
described.
10. The construction of electric meters with an outer casing to cover the ends of
the screws or fastenings by which the meter is secured in place and to cover the
sockets in which the ends of the conducting wires passing to and from the meter are
held and securing such cover with a sealed or locked fastening.
11. An electric meter capable of being sealed in a box or casing of its own after
standardising and with projecting wires or terminals on to which the house and
supply wires may be fixed and the junctions enclosed by a casing or casings which
can be sealed or locked.
12. Electric meters in which the enclosing case or cases have a double function
to fulfill first to enclose the meter in such a way that the constant or value of its
record cannot be altered after closing or sealing and secondly so that the connections
of the meter and its fixing in position cannot be tampered with by the consumer.
Dated this 26th day of November 1890.
CARPMAEL & Co.,
Agents.