An Improved Electrical Measuring Instrument.
Year: 1898

page_text: Date of Application, 10th Dec., 1898-Accepted, 25th Feb., 1899
COMPLETE SPECIFICATION.
An Improved Electrical Measuring Instrument.
I, KARL LEANER, of 17, Seehofstrasse, Frankfort-on-the-Main, in the Empire of
Germany, Technologist, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement:--
This invention relates to an electrical measuring instrument by means of which
the work effected by a current in a unit of time may be measured. This improved
measuring instrument is based on Joule's law according to which as is well known
the quantity of heat produced by the current is taken as the measure for the work'
delivered. In such instruments as is well known by the heating of a portion of
the conductor an indicating mechanism is turned in such a way that the respec-
tive portion of the wire is maintained constantly stretched by means of a spring
or a weight at its extension and the movement of the spring or weight is trans-
mitted in a suitable and ordinary manner to the spindle of the pointer.
In the improved measuring instrument which forins the object of this invention
the spring or weight system is replaced by a second series of wires acting in an
opposite direction, which wires however are not traversed by the electric current.
Both sets of wires are always under the action of such a quantity of heat as corre-
sponds to the actual conditions of moisture and temperature existing.
This improved measuring instrument is shown in the accompanying drawings,
Figure 1. being a front view of one form of construction; and
Figure 2, a view in perspective of a second form of construction.
The measuring wire a to be heated by the current is formed of platinum or
silver and connected at one end firmly with a small pillar e, whilst the other end
is attached to the shorter arm of a lever a¹. The lever a¹ at its point of rotation
is connected with a stretching and setting angle piece h¹ by means of a silk thread.
The end of the angle piece is also connected by a wire with
a
manner
second lever 1 and the point of rotation of the latter lever is
connected with the pillar e by means of a silk thread. In a similar
cd is connected with levers d¹d sup-
a second set of wires
ported by silk threads. The longer ends of the levers a¹ and also of the
levers ed are connected by means of silk threads f¹ f2. The oppositely directed
centre points of the threads f¹ f2 are connected to a roller on the spindle of the
pointer by means of a further silk thread f connecting the centres of the two
said threads ff. The pointer z moves over an empirical scale formed on the
measuring instrument and indicates directly the energy delivered by the current
in watts. The current supply to the measuring wires a and b as well as the
carrying off of the current from the said wires takes place by means of easily
flexible or yielding thin silver or platinum spirals.
2
When the apparatus is free from current the pairs of wires a b and c d under
the influence of an outer temperature which is even for the whole apparatus,
maintains an equipoise under the mutual tension caused by the adjustment of the
silk threads f f f by means of the pairs of levers a¹ b¹ c¹ d' at the zero point of

page_text: the indicating scale. As soon however as the wires a and b are traversed by a
current they receive a moderate extension so that their tension diminishes. The
tension remains unaltered in the wires c d which are not traversed by current,
that is to say the tension in the wires c and d is then greater than in the wires a
and b. This excess of tension by means of the levers a¹ b c d¹ and the silk
threads f f f effects a rotary movement of the indicator or pointer z.
A substitute for any springs or weights is furnished by the second pair of
wires c, d. This second pair c d is not only influenced by the elasticity of the
wires in a longitudinal direction but also by the tendency to bend in a transverse
direction. In addition to this the elasticity of the entire system must also be
taken into consideration; so that the two pairs of wires a, b and c, d are in such
a condition of mutual elastic tension that the degree of motion of the threads f
will lie with absolute certainty within the limits of the elasticity. This arrange-
ment possesses great advantage over the arrangements having springs and similar
contrivances, because the springs and the wires under tension are influenced con-
siderably by changes of temperature, whereas the pairs of levers a¹, b' and c¹, di
from the principle of symmetry undergo equal alterations upon change of tempera-
ture, so that no alteration of the equilibrium can take place.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed, I declare that what I
claim is:-
A measuring instrument for indicating the energy of an electric current on
Joules principle, characterised by the arrangement of a system of compensating
wires for stretching and compensating the actual measuring wires and trans-
mitting devices, said system of compensating wires coinciding with the actual
measuring wires as regards their arrangement and material but not being traversed
by current, with the object of avoiding the use of any separate loading by means
of a spring or weight, substantially as hereinbefore set forth.
Dated this 9th day of December 1898
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.