Improvements in Apparatus for Measuring Electrical Currents.
Year: 1895

page_text: Date of Application, 24th May, 1895
Complete Specification Left, 8th Feb., 1896-Accepted, 14th Mar., 1896
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Measuring Electrical Currents.
We, SIEMENS BROTHERS & Co. LIMITED, and EDWARD FRIEDRICH
HERMANN HEINRICH LAUCKERT, of 12 Queen Anne's Gate, Westminster, in
the County of Middlesex, Electrical Engineers, do hereby declare the nature of
this invention to be as follows:-
This invention relates to apparatus for measuring electrical currents, or ammeters,
of the kind in which the one pole of a steel magnet, bent into a circular arc and
mounted on an axis, enters the loop of a bent bar or wire coil through which the
current to be measured passes, so that the magnet in being drawn more or less into
the loop in proportion to the strength of the current, partially rotates the axis
and causes a pointer mounted thereon to indicate the deflections on a scale.
One of the present improvements consists in the application of simple means for
rendering this construction astatic, so that it may not be affected by extraneous
currents passing in the neighbourhood of the apparatus, or by a stray magnetic
field.
For this purpose we employ a second steel magnet of the same curved form as
the first but having its poles reversed, which we fix on the same axis and parallel
to the first one, but in a position outside the loop of the bent conducting bar or
coil. Thus as the current passing through the latter will act in one direction
round, say, the north pole of the magnet situated within it, and in the opposite
direction relatively to the south pole of the magnet situated outside the loop, the
attraction exercised by the loop upon both magnets will be in one and the same
direction, while the opposite polarity of the magnets will render the instrument
astatic.
Another improvement upon the above described instrument has for its object to
enable it to afford readings in both directions for currents passing either in one
direction or the other through the looped conductor.
For this purpose we employ two curved magnets fixed in one and the same plane
on the pointer axis, with their poles of like sign opposite each other, the one pole,
say, the north of each maguet being made to enter the loop of the conductor
respectively on opposite sides thereof. Thus a current passing through the
conductor in one direction will attract the one magnet and repel the other, causing
the pointer to move in a corresponding direction over one half of the scale, while a
current passing in the opposite direction will attract the last named magnet and
repel the first one, thereby moving the pointer in the opposite direction over the
other half of the scale. This construction may also be rendered astatic by the
first described arrangement namely by providing on the spindle in addition to
the above named magnets, two precisely similar curved magnets, but with opposite
polarity, outside the loops of the conductor.
السيم
1005
ABEL & IMRAY,
Agents for the Applicants.

page_text: We, SIEMENS BROTHERS & Co. LIMITED, and EDWARD FRIEDRICH
HERMANN HEINRICH LAUCKERT, of 12 Queen Anne's Gate, Westminster, in
the County of Middlesex, Electrical Engineers, 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 relates to apparatus for measuring electrical currents or ammeters,
of the kind in which the one pole of a steel magnet, bent into a circular arc and
mounted on an axis, enters the loop of a bent bar or wire coil through which the
current to be measured passés, so that the magnet in being drawn more or less into
the loop in proportion to the strength of the current, partially rotates the axis and
causes a pointer mounted thereon to indicate the deflections on a scale.
One of the present improvements consists in the application of simple means for
rendering this construction astatic, so that it may not be affected by extraneous
currents passing in the neighbourhood of the apparatus, or by a stray magnetic
field.
For this purpose as shewn in side view Fig. 1 and end view Fig. 2 we employ a
second steel magnet B of the same curved form as the first C but having its poles
reversed, which we fix on the same axis A parallel to the first C, but in a position
outside the loop L of the bent conducting bar or coil. Thus as the current passing
through L acts in one direction round, say, the north pole of the magnet C situated
within it, and in the opposite direction relatively to the south pole of the magnet B
situated outside the loop, the attraction exercised by the loop L upon both
magnets B and C is in one and the same direction, while the opposite polarity of
the magnets renders the instrument astatic.
In order to adapt an instrument of the kind above described to give readings in
both directions for currents passing either in one direction or the other through
the looped conductor L we employ as shewn by Fig. 3 two curved magnets DE
fixed in one and the same plane on the pointer axis A with their poles of like sign
facing each other, the one pole, say the north of each magnet being made to enter
the loop L of the conductor respectively on opposite sides. Thus a current passing
through the conductor in the one direction will attract the one magnet, say D, and
repel the other E causing the pointer I to move in a corresponding direction over
the scale on the one side of the middle while a current passing in the opposite
direction will attract the magnet E and repel D thereby moving the pointer in the
opposite direction over the scale on the other side of the middle. This construction
may also be rendered astatic by the first described arrangement namely by pro-
viding on the spindle A in addition to the magnets D and E two precisely
similar curved magnets, but with opposite polarities outside the loops L of the
conductor.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, we declare that what we claim
in respect of apparatus for measuring electrical currents of the kind in which the
pole of a bent magnet enters the loop of a bent conductor traversed by the current
measured, is
1. In addition to the one magnet, a second magnet of opposite polarity fixed on
the same axis but outside the bend of the conducting loop, substantially as and for
the purpose set forth.

page_text: 2. In addition to the one magnet, a second magnet of like polarity fixed on the
same axis facing the former, substantially as and for the purpose set forth.
Dated this 8th day of February 1896.
ABEL & IMRAY,
Agents for the Applicants.