A New or Improved Apparatus or “Inductometer" for Measuring the Intensity of a Magnetic Field.
Year: 1888

page_text: PROVISIONAL SPECIFICATION.
A New or Improved Apparatus or “Inductometer" for Measuring the
Intensity of a Magnetic Field.
I, GEORGE MIOT, of 72 Boulevard Hausemann, Paris, France, Electrical Engineer,
do hereby declare the nature of this invention to be as follows :-
The present invention relates to an apparatus which I call an "inductometer," and
which has for its object the measurement of the intensity of the current in a magnetic
field of any kind. It is based upon the principle that if a capillary tube be connected
to the horizontal or connecting branch of a U-shaped tube, and arranged parallel to
the other branches of such tube, the said branches being filled with mercury, and an
exciting current passed therethrough, and the horizontal portion of the tube be
placed in a magnetic field of any kind, at right angles to the plane of force, then the
mercury will rise up into the capillary tube to a height proportional to the intensity
of the magnetic field and to that of the exciting current.
In the annexed sheet of illustrative drawings,
Fig. 1 is an elevation, and
Figs. 2 and 3 are horizontal sections in the lines 1, 2, and 3, 4, respectively of
Fig. 1, of an inductometer according to this invention.
The improved apparatus comprises a tube A, B, C, whose lower portion is flattened
in such a manner as to allow of its being placed in a very short magnetic field such
as those occurring in dynamo-electric machines.
At the base B of this tube, is connected a capillary tube D surmounted by a vessel E
to which it is connected by means of an india rubber tube.
Above the vessel E rises a graduated tube F. G, G, are two other vessels
connected to the extremities of the U-shaped tube by means of two india-rubber
tubes; they are provided with necks through which mercury is poured into the
apparatus until each of the three vessels is about half filled therewith."
A small quantity of glycerine is poured upon the top of the mercury in the
vessels G, Gi; and a small quantity of tinted water or alcohol is introduced into
the tube F.

page_text: In order to protect the mercury and the other liquids from contact with air, the
U-shaped tube is preferably extended above the two vessels and joined to the centre
tube F at the top.
By this means the liquids are enclosed in an atmosphere which has no communica-
tion with the external atmosphere.
The apparatus is mounted on a board in order to facilitate its use and transportation.
In order to measure the intensity of a magnetic field by means of the apparatus
herein before described, two metallic stems or conductors H & H' are inserted through
the necks G and G¹, and caused to enter the mercury; these stems or conductors are
then placed in corumunication with the two poles of a generator producing an
exciting current of any kind.
The part B of the tube A B C is then placed in the magnetic field to be investigated
and at right angles to the plane of force.
The mercury will then at once rise into the vessel E and forced the colored liquid
upward into the tube F. As the diameter of this tube F is much smaller than that
of the vessel E, the heights are amplified in proportion to the relation between the
density of the mercury and that of the liquid used.
Inasmuch as the india rubber joints will allow the part B to assume various
positions, the instrument can be employed to investigate magnetic fields of different
kinds located horizontally, vertically or in any other position.
Dated this 20th day of February 1888.

page_text: A New or Improved Apparatus or Inductometer for Measuring the
Intensity of a Magnetic Field.
I, GEORGE MIOT, of 72, Boulevard Haussemann, Paris, France, Electrical Engineer,
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:
The present invention relates to an apparatus which I call an "inductometer," and
which has for its object the measurement of the intensity of magnetic fields of any
kind. It is based upon the principle that if a capillary tube be connected to the
horizontal or connecting branch of a U-shaped tube, and arranged parallel to the
other branches of such tube, the said branches being filled with mercury, and an
exciting current passed therethrough and the horizontal portion of the tube be placed
in a magnetic field of any kind, at right angles to the plane of force, then the mercury
will rise up into the capillary tube to a height proportional to the intensity of the
magnetic field and to that of the exciting current.
Referring to the sheet of illustrative drawings filed with
specification,
Fig. 1 is an elevation, and
my provisional
Figs. 2 and 3 are horizontal sections in the lines 1, 2, and 3, 4, respectively of
Fig. 1, of an inductometer according to this invention.
The improved apparatus comprises a tube A, B, C, whose lower portion is flattened
in such a manner as to allow of its being placed in a very short magnetic field such
as occurs in dynamo-electric machines.
At the base B of this tube is connected a capillary tube D surmounted by a vessel E
to which it is connected by means of an india-rubber tube.
Above the vessel E rises a graduated tube F. G, G₁, are two other vessels
connected to the extremities of the U-shaped tube by means of two indiarubber tubes ;
they are provided with necks through which mercury is poured into the apparatus
until each of the three vessels is about half filled therewith.
A small quantity of glycerine is poured upon the top of the mercury in the
vessels G, G; and a small quantity of tinted water or alcohol is introduced into the
tube F.
In order to protect the mercury and the other liquids from contact with air, the
U-shaped tube is preferably extended above the two vessels and joined to the centre
tube Fat the top. By this means, the liquids are enclosed in an atmosphere which
has no communication with the external atmosphere. The apparatus is mounted on
a board in order to facilitate its use and transportation.
In order to measure the intensity of a magnetic field by means of the apparatus
hereinbefore described, two metallic stems or conductors H and H' are inserted
through the necks G and G, and caused to enter the mercury; these stems or con-
ductors are then placed in communication with the two poles of an electric generator

page_text: producting a current. The part B of the tube A, B, C, is then placed in the magnetic
field to be investigated, and at right angles to the plane of force. The mercury will
then at once rise into the vessel E and force the coloured liquid upward into the
tube F. As the diameter of this tube F is much smaller than that of the vessel E,
the heights are amplified in proportion to the relation between the density of the
mercury and that of the liquid used. The level of the mercury in the vessels G, G',
will vary slightly as the liquid rises in the tube F, but so slightly that the difference
will not appreciably affect the truth of the readings.
Inasmuch as the indiarubber joints will allow the part B to assume various positions,
the instrument can be employed to investigate magnetic fields located horizontally,
vertically, or in any other position.
The variations in level of the coloured liquid will always be proportional to the
intensity of the field which is to be measured, and to that of the exciting current
which must be known, as well as the constant of the instrument.
But in order that equal lengths of the colored liquid may correspond always to
equal displacements of the mercury, it is necessary that the relation between the
section of the tube which carries the scale, and that of the cylindrical bulb in the
middle shall be constant. For this purpose it is sufficient if these tubes are correctly
calibrated.
Having now particularly described and ascertained the nature of the said
invention, and in what manner it is to be performed, I declare that what
I claim is :-
1. In an instrument for measuring the intensity of a magnetic field, a fluid con-
ductor, such as mercury traversed by an electric current, the said fluid being impelled
upwards by the reciprocal action of the electric current and the magnetic field, and
the amount of the said impulse being measured by the height to which the fluid
attains substantially as described.
2. In an instrument for measuring the intensity of a magnetic field, the combination
of a U-shaped tube filled with mercury and traversed by an electric current with a
capillary tube up which the mercury is forced by the reciprocal action of the current
and the magnetic field, substantially as described.
3. The improved instrument for measuring the intensity of a magnetic field con-
structed and operating substantially as described with reference to the drawings.
Dated this 25th day of June 1888.