IMPROVEMENTS IN APPARATUS FOR MEASURING ELECTRICAL CURRENTS
Year: 1884

page_text: COMPLETE
SPECIFICATION.
I, FELIX PAUL ERNEST DE LALANDE, Civil Engineer and Electrician, of 36 Rue
de la Montagne Sainte-Genevievè, Paris, in the Republic of France do hereby
declare the nature of my invention for IMPROVEMENTS IN APPARATUS FOR
MEASURING ELECTRICAL CURRENTS and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:
This apparatus is intended for the measurement of electric currents and is com-
posed (Fig 1) of an areometer a b having the same general shape and appearance
of ordinary areometers, but in the cylindrical floating portion of which a thin tube
of soft iron cd is encased.
•
This areometer floats in a glass-vessel ef filled with liquid up to a determined
level gh-The lower part of this vessel is surrounded by a coil k l m n wound
with an insulated wire and the extremities of which are connected with the
terminals p&q-The level of the liquid is determined so that the lower part of
the soft iron tube enters the coil a certain distance, always the same when the
current does not pass through the apparatus.
If a current passes through the coil, the soft iron tube being vertically attracted
the areometer sinks a certain distance which is invariable for a given current.
A mark a being made in the higher part of the areometer's rod the downward
motion of the areometer can be estimated by the position taken by the said mark a,
on a fixed scale rs with which the glass vessel is provided.
The gradation of the scale having been experimentally determined a simple
reading is afterwards sufficient for ascertaining what current passes through the
coil-If the coil is wound with a thick short wire of a very small resistance, the
gradation will give the intensity of the current in amperes and if it is wound with
a thin, long wire of a very great resistance the gradation will show the electro-
motive force of the current in volts.
In the arrangement illustrated in Fig 2, the coil k l m n is disposed so as to
produce an upward attraction of the soft iron tube-The actions of the current
causes the areometer to emerge from the liquid-If the rod of the areometer is
provided at its top end with a small tray t the current may be weighed by placing
in the said tray a sufficient quantity of weights to bring the areometer down
to the position which it previously occupied before the passage of the current.
In

page_text: this case the areometer's rod is provided with a mark a made to correspond either
to the level of the liquid or to fixed mark on the glass vessel.
The intensity or the electromotive force of the current corresponding to given
weights shall have been experimentally determined.
The same result may be obtained without the use of weights by means of the 5
following arrangement-The areometer's rod is graduated into equal divisions and
the glass vessel is movable vertically inside the coil.
In order to effect readings the glass vessel will be moved so that whatever may
be the current passing through the coil the soft iron tube will always enter the
said coil of the same quantity. The vertical displacement of the glass vessel, 1
shown on the scale of the areometer's rod will be proportional to the attractions
caused by the current.
Fig 3 represents an arrangement in which the glass vessel contains mercury up
to NV and water up to gh. The areometer itself is composed of a cylindrical
party which contains the soft iron tube cd and a cylindrical rod ab made of
glass, iron, or platinum-It is ballasted so that it is entirely immersed and the
rod ab slightly dips into the mercury.
The coil m n is placed so as to produce a downwards attraction. The passage
of the current in the coil, attracting the areometer causes the rod ab to sink more
or less in the mercury and the displacements of the areometer are indicated by the
various positions of the mark z which it carries with it, along a scale vs fixed on
the glass vessel.
These arrangements can be varied in many different ways; the scale may be
movable on the glass vessel, or it can be fixed on the arcometer's rod and the
readings taken from the liquid's level or from a fixed mark on the glass vessel; the
soft iron tube may be replaced by a piece of soft iron of varying shapes. With
a view to increase the sensitiveness of the apparatus, pieces of soft iron of various
shapes may be placed inside the coil, whatever may be the description of the
apparatus. For example in the apparatus shown in Fig 1 a soft iron cylinder of
small height could be placed underneath the glass vessel inside the coil, or the base
of the glass vessel could be incased, up to a certain beight, in a thin soft iron tube,
the dimensions of the coil allowing of the admittance of the glass vessel and its
additional appertenances. The areometer instead of being made of glass, may be
made of any other material such as iron, tinned or not, such as the one represented
in Fig 4; where b6 is a metallic vessel closed at the top by a cover or cap a soldered
to it, the whole being traversed by an iron wire also soldered to the vessel and its
cap and ballasted at the bottom c. In this case it would be better to choose as
a liquid a solution containing some soda or caustic potash in which iron does not
oxydise.
The glass vessel may be stopped or even closed with the spirit lamp. The liquid
used may be water or a saliferous solution, either colored or not.
The interior of the glass vessel or the areometer itself or both may be coated
with paraffin or with a varnish which prevents the contact with water either
absolutely or partially, so as to reduce the capillary action between the walls of
the vessel and of the areometer.
This result can also be obtained by adapting to the glass vessel a cover BC
(Fig 5) to which is attached a piece A, made of ebonite, glass or metal and placed
inside the liquid, acting as a guide. The said cover BC is provided with an
aperture sufficiently large for preventing the areometer's rod touching it. The
guiding in the liquid keeps the areometer at a certain distance from the wall of
the glass vessel and does not introduce any appreciable resistance in its action. In
this arrangement, the scale is fixed inside the areometer's rod and the readings are
taken at the level of the top of cover BC.
Whatever may be the description of the apparatus used it may be enclosed into
a soft iron armature so as to render its working independent of external magnetic
actions

page_text: Having now described my invention and the manner in which the same is to be
performed, I claim as my invention
"
"
1° The construction of apparatuses for the measurement of electric currents,
which are characterized by the use of a float, analogous to what is known in
science and commerce as areometers or "hydrometers," the said float carrying
a piece of soft iron (in the shape of a thin tube or in any other shape or form)
which is subject to the action of the current.
2° The various descriptions of the said apparatus as described before and
particularly
a The arrangement of a weighing electric areometer as described and illustrated
Fig. 2 The arrangement of a double liquid arcometer as described and illustrated
Fig 3.
c The use of water proof substances for the reduction of the capillary action
between the internal wall of the glass vessel and the external one of the areometer.
d The guiding of the areometer's rod inside the liquid, as described and illustrated
in Fig 5.
e The introduction, inside the coil, of pieces of soft iron intended for the
increasing of the sensitiveness of the apparatus.
3º The application of these electric current areometers to the measurement of
the intensity and electromotive force of either continuous or alternating currents.
London. ninth December 1884.