Improvements in Electric Meters.
Year: 1892

page_text: Date of Application, 17th Feb., 1892
Complete Specification Left, 19th Dec., 1892-Accepted, 17th Feb., 1893
PROVISIONAL 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 inven-
tion to be as follows:-
In electricity meters and especially motor meters and in which mercury is used
as a conductor or a contact maker and also sometimes as a means of retardation of
the motion, great difficulty is experienced owing to the mercury eating into the
metals with which it is in contact. In order to prevent this the metals have been
plated with some other metal such as nickel in order to prevent them being attacked
and eaten away. Now I have found this method ineffective as the mercury gets
through the plating and amalgamates the parts causing in some cases failure of the
apparatus. I therefore make all the parts in contact with the mercury of a metal
or metals which are not attacked and for this purpose I employ for instance nickel,
aluminium, platinum, iron, steel, iridium, nickel steel, manganese steel or iron, and
iron or steel containing spiegel. The above are the best materials but iron and
steel are the only entirely satisfactory materials, as all the others fail under
extreme conditions.
In some cases good results may be obtained by thickly plating parts with iron or
by mechanically covering them with thin sheet iron or steel.
Some of the contacts in meters have hitherto been made of a non magnetic metal
as it was thought that otherwise they would short circuit the magnetic field or
affect the working of the apparatus detrimentally. Now I find that if these parts
are made of only partially magnetic iron or of steel which has a low permeability
or of sufficiently small mass or thickness that they do not detrimentally affect
the working and for this reason I prefer to use them as they are unattacked by the
mercury.
With the moving parts it is essential to have them very slightly magnetic and to
effect this I prefer to make them of non magnetic steel but any of the above named
metals can be used. In some cases I make the spindle carrying the fan or
armature of non-magnetic steel or metal either wholly or in part.
In order that the apparatus may work well for a considerable time it is necessary
to specially treat all parts which touch the mercury to remove all grease and also
to specially purify and remove grease from the mercury.
In a Patent already granted to me No. 701 in the year 1887 I have described a
method of compensating electric meters by means of winding them with double
coils, one carrying the main current and the other a shunt current.
In some cases now effect this compensation by using permanent magnet and a
current to make the magnetic field. The current which is ordinarily that to be
measured may increase or decrease the field of the permanent magnet as is wanted
for the purpose of compensation.
In meters I find it best to make the magnetic circuit for the above purpose for
part of its length only of steel as otherwise the compensation is overdone.
In some case I add an additional armature and field worked by a shunt current
and assisting the principal parts for the purpose of compensating their readings..
I vary the readings of meters by varying the distance of the magnets from the
armature or the position of the coils on the magnets, or by an adjustable pole in
series with the magnetic circuit making a greater or lesser air gap in the field.
Dated this 17th day of February 1892.

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 inven-
tion and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement :-
In electricity meters and especially motor meters and in which mercury is used
as a conductor or a contact maker and also sometimes as a means of retardation of
the motion, great difficulty is experienced owing to the mercury eating into the
metals with which it is in contact. In order to prevent this the metals have been
plated with some other metal such as nickel in order to prevent them being
attacked and eaten away. Now I have found this method ineffective as the
mercury gets through the plating and amalgamates the parts causing in some cases
failure of the apparatus. I therefore make all the parts in contact with the
mercury of a metal or metals which are not attacked and for this purpose I employ
for instance nickel, aluminium, platinum, iron, steel, iridium, nickel-steel, manganese-
steel or iron, and iron or steel containing spiegel. The above are the best materials
but iron and steel are the only entirely satisfactory materials, as all the others fail
under extreme conditions.
In some cases good results may be obtained by thickly plating parts with iron or
by mechanically covering them with thin sheet iron or steel.
Some of the contacts in meters have hitherto been made of a non magnetic metal
as it was thought that otherwise they would short circuit the magnetic field or
affect the working of the apparatus detrimentally. Now I find that if these parts
are made of only partially magnetic iron or of steel which has a low permeability
or of sufficiently small mass or thickness that they do not detrimentally affect the
working and for this reason I prefer to use them as they are unattacked by the
mercury.
With the moving parts it is essential to have them very slightly magnetic and
to effect this I prefer to make them of non magnetic steel but any of the above
named metals can be used. In some cases I make the spindle carrying the fan or
armature of nonmagnetic steel or metal either wholly or in part.
In order that the apparatus may work well for a considerable time it is necessary
to specially treat all parts which touch the mercury to remove all grease and also
to specially purify and remove grease from the mercury.
In a Patent already granted to me No. 701 in the year 1887 I have described a
method of compensating electric meters by means of winding them with double
coils, one carrying the main current and the other a shunt current.
In some cases I now effect this compensation by using permanent magnet and a
current to make the magnetic field. The current which is ordinarily that to be
measured may increase or decrease the field of the permanent magnet as is wanted
for the purpose of compensation.
In meters I find it best to make the magnetic circuit for the above purpose for
part of its length only of steel as otherwise the compensation is overdone.
I vary the readings of meters by varying the distance of the magnets from the
armatures or the position of the coils on the magnets or by an adjustable pole in
series with the magnetic circuit making a greater or lesser air gap in the field.
Figure 1 shows a vertical section of a meter constructed in this way.
a is a cast iron casing enclosing the meter and the counting apparatus 6 the latter
being supported on a brass stand c. d is a cylinder of wrought iron insulated from
the casing at top and bottom by vulcanized fibre e. The bottom of the cylinder d
has screwed to it the pole piece f of wrought iron. g is a copper tube supporting
the steel pole piece haud the mercury chamber which consists of a mild steel ring j
and two annular discs of vulcanized fibre k k the mercury passing through the

page_text: central holes in these discs and being in contact with the pole piece and cavity
in the top of the cylinder d as shown. The mercury vessel also contains the vane
mounted on the spindle m by which the counting apparatus is actuated. n is a coil
of insulated copper wire having its end connected to the gun metal terminal o and
its upper coil being in contact with the ring j.
The following precautions are taken to prevent the contamination of the mercury
by grease.
The steel ring j is repeatedly boiled in solutions of caustic soda and is then
washed in pure distilled water and polished with purified fibre. The discs k k are
successively boiled in about 12 baths of water being passed forward from one to the
other and when the first bath becomes too impure it is replaced by another which is
now used last the second becoming the first. When the meter is being put together
the cup in the pole piece g the cavity in the top of the cylinder d and the inside of
the ring j and discs kk are again washed with caustic soda and afterwards with
water.
The mercury itself is purified by being repeatedly dropped in the form of a very
fine spray onto the surface of a 10% solution of nitric acid about 18 inches deep
the process being carried on for about 24 hours. It is then similarly sprayed onto
distilled water and then onto a 10% solution of caustic soda this again being about
18 inches deep and the process being continued for about 24 hours. The mercury
is then again washed by spraying through water its surface is dried with pure filter
paper it is then raised to 212° F. to drive off any remaining water and is finally
filtered through pure sugar to remove hairs, dust &c.
In some cases I add an additional armature and field worked by a shunt current
and assisting the principal parts for the purpose of compensating their readings.
Figures 2 and 3 show this arrangement applied to a Ferranti and Wright meter.
A A are the additional coils through which a shunt circuit passes B B are the
magnet poles and C their armature.
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 an electric motor meter in which mercury is used wholly or in part to
conduct the current to be measured, partially closing the magnetic field by a ring
or block of magnetic metal, which also forms one contact with the mercury substan-
tially as described.
2. In an electric motor meter in which mercury is used wholly or in part to
conduct the current to be measured, partially closing the magnetic field by a ring
or block of iron or steel, which also forms one contact with the mercury substan-
tially as described.
3. In an electric motor meter in which mercury is used wholly or in part to
conduct the current to be measured, partially closing the magnetic field by a ring
or block of iron or steel rendered more or less non-magnetic, which also forms one
contact with the mercury substantially as described.
4. In an electric meter in which a ring is used encircling the mercury bath
making this ring of non-magnetic steel or iron substantially as described.
5. In an electric meter in which a fan or disc is wholly or partially immersed in
mercury, and in which the fan or disc or the mercury convey a portion or the
whole of the current, making the fan or disc of non-magnetic steel or iron substan-
tially as described.
6. In an electric meter in which a portion of the magnetic field is the residual
magnetism of the magnetic field increasing the stability of the magnetic field by
partially closing the active part of the field by a magnetic or partially magnetic
ring or piece of metal, the same being in contact with the mercury substantially as
described.
7. In an electric motor meter in which the magnetic field is made up for a portion
of its length of steel and for a portion of its length of iron, winding a compensating

page_text: coil on a portion of the magnetic field to vary the strength of the magnetic field
according to the amount of current passing through the meter substantially as
described.
8. In an electric motor meter in which an armature in contact with. mercury is
rotated by the field obtained from a permanent magnet, compensating the said field
by means of a series winding or windings substantially as described.
9. In an electric meter in which mercury is employed mechanically plating the
conducting disc with a. thin sheet of metal unaffected by mercury substantially as
described.
10. In an electric motor meter making the spindle carrying the moving parts of
non-magnetic metal substantially as described.
11. In an electric motor meter making the spindle carrying the moving parts of
steel or iron rendered very slightly magnetic and known as non-magnetic steel or
iron substantially as described.
12. In electric meters using mercury, treating the mercury and all parts in contact
with it in order to remove grease substantially as described.
13. In electric motor meters the use of a second armature and magnetic field or
of a second armature in the same field or of a second field acting upon the same
armature to give a constant rotative force to the meter to compensate for initial
friction or other cause tending to make the meter run slowly, such force being so
proportioned that the meter will hardly start or not start at all with it only
substantially as described.
14. Electric meters substantially as described.
Dated this 19th day of December 1892