Improvements in Electricity Meters.
Year: 1898

page_text: Improvements in Electricity Meters.
I, GEORGE HOOKHAM, of New Bartholomew Street, Birmingham, in the County
of Warwick, Manufacturer, do hereby declare the nature of this invention to be
as follows:-
My invention relates in part to electricity meters for measuring alternating or
intermittent or interrupted currents, and in part electricity meters for measuring
continuous currents in which the armature is immersed in mercury. Both types
are motor meters.
The first part of my invention is applicable to electricity meters for measuring
alternating or intermittent or interrupted currents in which the armature is caused
to rotate by the interaction of eddy currents induced in it by a shunt electro
magnet, and currents passing through coils exterior to the disc, the said coils
carrying the currents to be measured.
In meters of this type difficulty has hitherto been found in so calibrating the
meter as to give correct readings at high as well as lower loads. It has been
found difficult to modify the readings at high loads without also affecting the
readings at lower loads.
My invention consists in a method of straightening the curve of registration
so as to obtain accurate proportionality of registration to load. My method con-
sists in varying or distorting the field of the shunt electro magnet. This distor-
tion I may accomplish in several ways. According to one method, which I find
acts successfully, I provide the pole-piece with a sliding adjustable iron extension
either on one or both sides. These extensions I arrange with suitable connec-
tions, such as screws and slots, to enable me to raise or lower them without shifting
the central pole piece. When I desire to slow the matter at top load, I find that
I can do this by lowering the polar extension towards which the meter armature
is moving.
I produce the same effect or accentuate that effect by raising the polar exten-
sion from which the armature is moving. By the reverse movement I produce
the reverse effect that is, by raising one pole piece and depressing the other I
obtain an increase in speed. I have determined by experiment that this produces
the effect I have stated in one type of meter, but I do not limit myself to any
particular edge raised or lowered, because it may be that in another type lowering
the advanced edge might produce increase in speed. My invention consists in
distorting the field by any suitable means. I prefer, however, to cause this dis-
tortion by polar extensions, or by an oscillating or swivelling pole-pieces, in which
one edge may be approached nearer the armature than the other. This adjustment
may be made on either side of the disc or armature.
The second part of my invention relates to continuous current meters in which
a disc or armature rotates, immersed in mercury, and one improvement is intended
to enable one size of meter to be readily adapted to measure currents of greatly
varying maximum quantity. In constructing such a meter I use an immersed

page_text: disc through which I pass the current to be measured across the disc from side
to side instead of from periphery to centre and I so dispose the magnetic poles
that the field is twice cut by a radius of the disc in every revolution each time
in an opposite sense to the last as described in a Patent already granted to me
No. 2683 of 1896.
In my present invention however, I leave the edges of the pole pieces sharp so
as to produce Foucault currents in the disc, the disc thereby serves as both brake
and motor. To enable this meter to be adapted for measuring heavy as well as
light currents it is only necessary to vary the direction of the flow of the current
from side to side with regard to the position of the pole pieces. When the
maximum current to be measured is small I pass the current across the immersed
disc in line with the direction between the opposed pole pieces, and to suit greater
currents I alter the angle of flow across the disc bringing it nearer and nearer to a
direction at right angles to the line passing between the centres of the pole pieces.
At right angles of course a current however great, could have no effect in
rotating the disc. By this device I am enabled to use the same size of meter for
measuring heavy currents as well as light and all the alteration necessary consists
in shifting the angle of the line along which the current passes.
A further improvement is intended to secure the better protection of a portion
of the disc or armature from the action of the mercury. My invention is applicable
to armatures other than disc armatures but I will describe it as applied to a disc
armature. In discs as hitherto used the whole horizontal surface of the disc is
often coated with nickel deposited on it, and the edges, or the edges and centre,
suitably amalgamated. I have found that a large amount of nickel is a dis-
advantage, on account of its magnetic properties and in this improvement I dis-
pense with nickel coating except at the outer circumference, near the edge of the
disc on both sides. Here I place a thin coating of nickel, leaving the edge, how-
ever preferably in a grooved form, with a bare copper surface suitably amalga-
mated. I may also amalgamate the surface of copper at the centre of the disc.
The part of the copper disc free from nickel and from amalgamation I cover with
a suitable varnish on both sides, which varnish comes to the edge where the disc is
nickelled. By this arrangement I am enabled to produce a disc with a minimum
of nickel, and at the same time without requiring the varnish to be secured to
the disc right up to the amalgamated edge.
MARKS & CLERK,
18, Southampton Buildings, London, W.C., and
13, Temple Street, .Birmingham, Agents.
Improvements in Electricity meters.
I, GEORGE HOOKнAM, of New Bartholomew Street, Birmingham, in the County
of Warwick, Manufacturer, 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:-
My invention relates in part to electricity meters for measuring alternating or
intermittent or interrupted currents, and in part to electricity meters for measuring
continuous currents in which the armature is immersed in mercury. Both types
are motor meters.
The first part of my invention is applicable to electricity meters for measuring
alternating or intermittent or interrupted currents in which the armature is caused

page_text: to rotate by the interaction of eddy currents induced in it by a shunt electro-
magnet, and currents passing through coils exterior to the disc, the said coils.
carrying the currents to be measured.
In meters of, this type difficulty has hitherto been found in so calibrating the
meter as to give correct readings at high as well as lower loads. It has been
found difficult to modify the readings at high loads without also affecting the
readings at lower loads.
My invention consists in a method of straightening the curve of registration
so as to obtain accurate proportionality of registration to load. My method con-
sists in varying or distorting the field of the shunt electro-magnet. This distor-
tion I may accomplish in several ways. According to one method, which I find
acts successfully, I provide the pole-piece with a sliding adjustable iron extension
on one or both sides. These extensions I arrange with suitable connections, such
as screws and slots, to enable me to raise or lower them without shifting the central
pole piece. When I desire to slow the meter at top load, I find that I can do this
by lowering the polar extension towards which the meter armature is moving.
I produce the same effect, or accentuate that effect, by raising the polar exten-
sion from which the armature is moving. By the reverse movement I produce
the reverse effect, that is, by raising one pole piece and depressing the other I
obtain an increase in speed. I have determined by experiment that this produces
the effect I have stated in one type of meter, but I do not limit myself to any par-
ticular edge raised or lowered, because it may be that in another type lowering
the advanced edge might produce increase in speed. My invention consists in
distorting the field by any suitable means. I prefer, however, to cause this dis-
tortion by polar extensions, or by an oscillating or swivelling pole-picce, in which
one edge may be approached nearer the armature than the other. This adjust-
ment may be made on either side of the disc or armature.
The second part of my invention relates to continuous current meters in which
a disc or armature rotates, immersed in mercury, and one improvement is intended
to enable one size of meter to be readily adapted to measure currents of greatly
varying maximum quantity. In constructing such a meter I use an immersed
disc through which I pass the current to be measured across the disc from side to
side, instead of from periphery to centre, and I so dispose the magnetic poles that
the field is twice cut by a radius of the disc in every revolution, each time in an
opposite sense to the last, as described in a l'atent already granted to me, No. 2683
of 1896.
In my present invention, however, I may leave the edges of the pole pieces
sharp, so as to produce Foucault currents in the disc. The disc thereby serves
as both brake and motor. To enable such a meter to be adapted for measuring
heavy as well as light currents, it is only necessary to vary the direction of the
flow of the current from side to side with regard to the position of the pole pieces.
When the maximum current to be measured is small, I pass the current across the
immersed disc in line with the direction between the opposed pole pieces, and to
suit greater currents I alter the angle of flow across the disc, bringing it nearer and
nearer to a direction at right angles to the line passing between the centres of
the pole pieces. At right angles of course a current, however great, could have
no effect in rotating the disc. By this device I am enabled to use the same size
of meter for measuring heavy currents as well as light, and all the alteration
necessary consists in shifting the angle of the line along which the current passes.
A further improvement is intended to secure the better protection of a portion
of the disc or armature from the action of the mercury. My invention is
applicable to armatures other than disc armatures, but I will describe it as applied
to a disc armature. In discs as hitherto used, the whole horizontal surfaces of
the discs are often coated with nickel deposited on them, and the edges, or the
edges and centre suitably amalgamated. I have found that a large amount of
nickel is a disadvantage, on account of its magnetic properties, and in this im-
provement I dispense with nickel coating except at the outer circumference, near

page_text: the edge of the disc on both sides. Here I place a thin coating of nickel leaving the
edge, however, preferably in a grooved form, with a bare copper surface suitably
amalgamated. I may also amalgamate the surface of copper at the centre of the
disc, and in that case I surround the amalgamated centre with a narrow ring of
nickelling.
The part of the copper disc free from nickel and from amalgamation I cover
with a suitable varnish on both sides, which varnish comes to the edge where the
disc is nickelled. By this arangement I am enabled to produce a disc with a
minimum of nickel, and at the same time without requiring the varnish to be
secured to the disc right up to the amalgamated edge.
Referring to the accompanying sheets of drawings:-
Figure is a front elevation, and
-
Figure 2 a side elevation, partly in section, of a meter showing one method of
carrying out the first part of my invention.
Figure 3 is a front elevation;
Figure 4 a similar elevation, partly in section,
Figure 5 is a plan of the same, partly in section, and
Figure 6 a similar plan with the magnet removed, showing the means provided
for changing the angular direction of current flow in relation to the fixed magnetic
field.
Figure 7 and 8 show plans of armatures embodying the features of the last
part of my invention.
In constructing an alternating current meter (Figures 1 and 2) in which an
armature A is caused to rotate by the interaction of eddy currents induced in it
by a shunt electro-magnet B, excited by the shunt coil 13, and the currents to be
measured which pass through the coils C exterior to the disc, I vary or distort the
field of the shunt electro-magnet B in various ways to enable the readings of
the meter to be made correct at high as well as low loads.
According to one method I provide the pole piece B with sliding adjustable
iron extensions B₁ and 132. These extensions I secure to the magnet pole by
means of screws and slots, thus enabling them to be shifted without moving the
main pole-piece.
When I desire to slow the meter at top load I find that I can do this by
lowering the polar extension 132 when the arinature is moving from B1 to B2, be-
tween the magnet poles.
I produce the same effect, or accentuate that effect, by raising the polar exten-
sion B. By the reverse movement, that is, by lowering B₁ and raising B³, I
produce the reverse effect i.e. an increase of speed at high loads.
I have determined by experiment that this produces the effect I have stated in
one type of meter, but I do not limit myself to any particular edge raised or
lowered, because the exact means for varying or distorting the magnetic field will
vary with every different type of meter."
I may also make the magnet B with a pivoted or hinged pole piece so that the
necessary distortion can be produced by a swivelling or oscillating movement.
The adjustment may be made on either side of the disc or armature as is found
most convenient, and a locking arrangement may be provided to fix the hinged
pole-piece when the adjustment has been made.
I will describe my present improvements in continuous current meters as applied
to a meter such as is described in my Patent No. 2683 of 1896, although they are
applicable also to other forms of meter. In constructing such a meter (sce
Figures 3 to 6) I arrange my permanent magnet D to enclose a square or oblong
space, so as to provide a considerable length of magnet steel, and I arrange the
This gap
pole-pieces so as to complete the square, but leaving a suitable gap.
prefer to fill in with non-magnetic metal, so as to secure structural continuity.
Additional pole-pieces are shown at E and E (Figure 4).
In this meter I support the permanent magnet 1 on a suitably shaped insulating
block Fixed to a base G to which the usual feet are attached. On this base G I

page_text: carry a non-conducting vessel H containing the mercury in which the disc arma-
ture K is immersed. The conductors I and I' carrying the current to be measured
pass into this vessel at opposite sides and are connected to the meter terminals by
Hexible connections. The whole vessel H is pivoted on the base G, and has a
vertical line on its outer periphery which, when the vessel is turned, moves over
the scale J.
The current thus passes through the immersed disc armature K across the disc
from side to side, and I so dispose the magnetic poles that the field is twice cut by
a radius of the disc K in one revolution.
To enable this meter to be adopted for measuring heavy instead of light currents
that is say, to make the range of the meter now from 2 to 20 ampéres instead of
from 1 to 10 ampéres, it is only necessary to vary to the required extent the angle
which the line of current flow makes with the line of the permanent magnet field.
The scale J can be graduated so that the mercury vessel can be set for any
particular absolute sensibility of the meter the range of sensibility remaining
practically the same as before. When the maximum current to be measured is
small, I pass the current across the disc K in line with the direction between the
opposed pole pieces, the mercury vessel being set in the position shown in
Figure 6. To suit greater currents I alter the angle of current flow across the
dise by setting the mercury vessel H carrying the conductors I, I' round,
bringing the line of current flow from I to I¹ nearer and nearer to the line L A
(Figure 6) thus making the meter more and more insensitive. When set to
coincide with the line L M no current, however great, could have any effect in
rotating the disc K.
I may also leave the edges of the pole-pieces E and E¹ sharp, so as to produce
Foucault currents in the disc K.
The disc in that case serves as both brake and motor, and my sensibility
changing device can be equally well applied to such a modified form of meter.
Figures 7 and 8 show disc armatures made according to my present invention,
but this invention is equally well adapted for the protection of other forms of
armature, intended to be immersed in mercury. In the disc shown in Figure 7
I only nickel plate a narrow band such as a on each side of the disc armature.
The edge of the disc is preferably grooved, and is left bare. The bare edge is
afterwards amalgamated, and the part 6 on each side is varnished with the usual
varnish, where the current is to be passed across the disc from side to side. In
the slit disc armature shown in Figure 8 I produce the same effect by nickelling
a complete ring a round each tooth 61 and I leave the ends a² forming the edge of
the disc free from nickelling or varnish. These ends are afterwards amalga-
mated. I then varnish the inner part of the disc with the usual protective varnish
where it is free from amalgamation or nickelling. I may also, when the current
is to be led off from the centre of the disc, amalgamate the surface of copper at
the centre of the disc, surrounding the centre by a narrow ring of nickel plating.
I am thus enabled to produce a disc with a minimum of nickel, and at the same
time without requiring the varnish to be secured to the disc right up to the
amalgamated edge.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:-
1. In an alternating current meter in which the motor part consists of a rotating
disc or other body rotated by the interaction of currents caused in the disc by a
shunt electro-magnet and series coils placed close to the disc; varying or dis-
torting the field of the shunt electro-magnet so as to obtain accurate propor-
tionality of registration to load, as herein before described.
2. In an alternating current meter as claimed in Claim 1, varying or distorting
the field of the shunt electro-magnet by means of one or more sliding or swivelling
pieces of iron substantially as hereinbefore described.

page_text: herein before
3. An alternating current meter constructed substantially as
described and illustrated at Figures 1 and 2 of the accompanying drawings.
4. In an electricity meter for continuous currents in which a disc or armature
rotates immersed in mercury, changing the sensibility of the meter by varying
the angular direction of current flow across the disc or armature with regard to
the line of the magnet-field as herein before described.
5. In an electricity meter for continuous currents, as claimed in Claim 4,
mounting the field electro-magnet and the main current conductors in such a
manner that they can be angularly displaced in relation to one another on the
axis of the armature so as to secure approximately equal range of sensibility
when used for low loads as when used for high loads, substantially as hereinbefore
described.
6. An electricity meter for continuous currents constructed substantially as
herein before described and illustrated in Figures 3 to 6 of the accompanying
drawings.
7. In an electricity meter for continuous currents in which a disc or armature
rotates immersed in mercury, the improved method of protecting the armature
substantially as described.
8. In an electricity meter for continuous currents, in which a disc or armature
rotates immersed in mercury, the improved armatures constructed substantially
as herein before, described and illustrated at Figures 7 and 8 of the accompanying
drawings.
Dated this 28th day of February 1899.
MARKS & CLERK,
18, Southampton Buildings, London, W.C.,
13, Temple Street, Birmingham, and
25, Cross Street, Manchester, Agents.