Improvements in Electric Measuring Instruments.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Electric Measuring Instruments.
I, WILLIAM THOMSON, Baron Kelvin of Largs, Professor of Natural Philosophy
in the University of Glasgow, North Britain, do hereby declare the nature of
this invention to be as follows:-
This invention relates to improvements in electric measuring instruments
and the object is to annul the error due to variation in temperature of the coils
wound with copper wire.
In carrying out my invention I employ incandescent lamps, the filaments of
which are in circuit with the coils conveying electric current less than that
required for brilliant incandescence. The lamps are fixed in the same case and
close to the coils. The resistance of the copper windings increases with rise of
temperature, while the resistance of the filament diminishes with rise of tem-
perature. By regulating the proportion of copper resistance to filament resis-
tance the error due to alteration in temperature of the coils is compensated.
Dated this 14th day of October 1898.
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Patent Agents.
Improvements in Electric Measuring Instruments.
I, WILLIAM THOMSON, Baron Kelvin of Largs, Professor of Natural Philosophy
in the University of Glasgow, North Britain, 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 improvements in electric measuring instruments
and the object is to annul the error due to variation in temperature of the coils
wound with copper wire.
In carrying out my invention I employ incandescent lamps, the filaments of
which are in circuit with the coils conveying electric current less than that
required for brilliant incandescence. The lamps are fixed in the same case and
close to the coils. The resistance of the copper windings increases with rise of
temperature, while the resistance of the filament diminishes with rise of tem-
perature. By regulating the proportion of copper resistance to filament resis-
tance the error due to alteration in temperature of the coils is compensated.
In order that my invention may be properly understood and readily carried
into effect I have hereunto appended one sheet of drawings.

page_text: The drawing is a diagrammatic representation of an electric measuring instru-
ment having fixed coils A, B, and movable coils C, D. T₁, T₂ are the terminals
and L₁ L, are two lamps in circuit with the coils of the instrument. The current
passes from one terminal T, through the lamps L₁, L, and then through the
fixed coils A and B and movable coils C, D, back to the other terminal.
..
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
In electric measuring instruments the use of incandescent lamps in circuit
with the coils of the instrument substantially as and for the purpose described.
Dated this 13th day of Julv 1899.
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Patent Agents.
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