Improvements in Electrical Measuring Instruments.
Year: 1899

page_text: Improvements in Electrical Measuring Instruments.
I, ERNEST CECIL RIMINGTON, of 19-21, Queen Victoria Street, London, E.C.,
Consulting Electrical Engineer, do hereby declare the nature of this invention
to be as follows:-
-
This invention relates to improvements in instruments for measuring elec-
trical current or pressure, and has for its object the construction of an excep-
tionally cheap and simple instrument, which dispenses entirely with any pivoted
moving part, and has thus no rubbing frictional resistance when in operation
which may be used as a vertical or horizontal instrument by suitable calibra-
tion and is not sensibly effected by slight divergences from its normal position
and is especially suitable for closing hermetically in an oil bath, should such
arrangement be desired.
To carry my invention into effect, I mount upon a board, which may be as
thin as desired, a flat spring of steel, phosphor, bronze or any resilient material,
and fasten it rigidly at one end upon a boss or standard on the board, the other
end of the spring being free to move and deflect. The said boss or standard
may be adjustable to the board so as to bring to a desired zero point the free
end of the spring, which may be drawn out into or carry a fine pointer, giving
a zero indication upon a suitable scale when the instrument is at normal.
To the said spring I attach a light soft iron core, which may conveniently be
thin sheet or tinned iron, and this core projects approximately at right angles
from the said spring, and is thus adapted to enter into a coil of wire by attrac-
tion when a current flows through the said coil, the bending of the said spring
offering the necessary resistance to measure the said attraction.
I find it convenient to make the core of a thin sheet taper form so as to be
adapted to enter a flat coil, so that all mechanism occupies little depth upon
the base board, but it is obvious any other form may be employed.
Instead of a piece of iron for the core, a coil of fine wire with flexible con-
nection, carrying part or the whole of the current to be measured, may be
employed; or, in the case of a Watt meter, the electrical pressure may be
applied to this coil put in series with more or less resistance, the total current
passing through the fixed coil.
I prefer to form the fixed coil without any iron core, thus avoiding hysteresis,
but a fixed iron core may be employed if desired in a well known manner.
The pointer may not necessarily be a direct continuation of the length of
the spring, but may be bent to any desired angle therewith to modify the posi-
tion of the scale with regard to the fixed coil.
It is obvious that this instrument can be excellently adapted to record
measurements by combination with a moving recording surface in any of the
well known ways.
It will be seen in this instrument as the moving core is affixed to, and moves

page_text: by, the resilience of the fixed spring, there are no pivots, or rubbing bearings
in its construction and all frictional resistance from such cause is avoided.
Dated this 30th day of June 1899.
FELL & JAMES,
1, Queen Victoria Street, London, E.C.,
Agents for the Applicant.
I, ERNEST CECIL RIMINGTON, of 19-21, Queen Victoria Street, London, E.C.,
Consulting 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:―
This invention relates to an improvement in instruments for measuring elec-
trical current or pressure, and has for its object the construction of an excep-
tionally cheap and simple instrument, which dispenses entirely with any pivoted
moving part, and has thus no rubbing frictional resistance when in operation
and which may be used as a vertical or horizontal instrument in any position
by suitable calibration, and is not sensibly affected by slight divergences from
its normal position, and is especially suitable for being enclosed in an oil bath
should such arrangement be desired.
Figure 1 is a front elevation of my improved instrument.
Figure 2 is a plan of the same.
Figures 3 and 4 show modifications of the attracted core of the spring
pointer.
A is a clamp or bracket, on a base board or plate K to which is attached a
spring B of steel, phosphor bronze, or resilient material, the outer end 1) of
the spring B being extended, and drawn out, into, or carrying, a fine pointer,
giving a zero indication upon a suitably calibrated scale L, when the instru-
ment is at normal, and the spring B is just short of touching upon a check pin G
above it.
To the said spring B, I attach a light core C, which may conveniently be thin
sheet or tinned iron, as in Figure 1, or may be a coil M, as in Figures 3 and 4
having flexible connections through the fixed end of the spring at A.
This core C or the equivalent coils, may be varied in shape as found desirable
to give a best uniformity of increments of the movement of the spring B for
variable amounts of current to be measured.
The current to be measured passes through a fixed coil E by the ter-
minals TT, such coil being conveniently flattened when the core C is a thin
strip, so as to bring all the mechanism into little depth upon the base board or
plate K, but it is obvious any form may be employed, as in Figures 3 and 4.
The core or the equivalent coils M when the current passes through the
main coil E is attracted therein, the resilience of the spring B offering the
necessary increasing resistance to measure the said attraction and hence the
current passing.
I prefer to form the fixed coil E without any iron core, to diminish hysteresis,
but a fixed iron core of any suitable shape may be employed in a well known
manner if desired to regulate or control the attraction of the coil E upon the
core Cor coils M.
I find a closed copper lining within the coil E is conducive to damping the
oscillation of the spring B, with continuous currents, upon change of position,

page_text: and may thus form a convenient frame upon which to wind the coil E, or it
may be inserted after the coil has been wound.
In
In the cases shown in Figs. 3 and 4 the terminals of the fine wire coil M
can be connected to the terminals T T of the main coil E, thus putting the
coil M in parallel with the coil E, in the case of an ammeter measurement.
the case of a voltmeter measurement the coil M may be in series with the coil E,
and the spring B of the pointer may have a preliminary set at zero. Or the
coil M can be put in series with a resistance, and used as the pressure coil,
whilst the current passes through the coil E to effect readings as a Watt-meter,
all in well known ways.
It is obvious that this instrument can be readily adapted to record its mea-
surements by combination with a recording surface in any of the well known
ways.
Having now paricularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed, I declare that what
I claim is:-
1st. An electrical measuring instrument consisting of, in combination; a flat
spring fixed to a base board at one end and free to move parallel to the base
board at the other end, drawn into or carrying a light indicating point; a coil
carrying the electrical current to be measured fixed to the base board; a soft
iron core or an energized coil projecting from said spring, adapted to be
attracted by and to enter into, the said fixed coil in proportion to the current
passing through the said coil; and a calibrated scale on the base board, to indi-
cate the amount of the transverse deflection of the said spring under the mag-
netic attraction, substantially as described.
2nd. An electrical measuring instrument consisting of, in combination, a flat
spring fixed to base board at one end, and free to move parallel to the base board
at the other end, drawn into or carrying a light indicating point; a flat coil
carrying the electrical current to be measured fixed to the base board; a core,
consisting of a wedge shaped iron plate, having an edge or edges notched or
shaped to admit of uniformity of spring deflection for various increments of
current, projecting from said spring, and adapted to enter into and be attracted
by, the body of the said fixed flat coil, in proportion to the current to be mea-
sured; and a calibrated scale upon the said base board to indicate the amount
of the transverse deflection of the said spring under the said magnetic attrac-
tion substantially as described.
Dated this 20th day of March 1900.
FELL & JAMES,
1, Queen Victoria Street, London, E.C.,
Agents for the Applicant.