An Improved Instrument for Testing the Resistance of Gun Fuse and other Electric Circuits.
Year: 1893

page_text: Date of Application, 16th Dec., 1893
Complete Specification Left, 13th Sept., 1894-Accepted, 20th Oct., 1894
PROVISIONAL SPECIFICATION.
An Improved Instrument for Testing the Resistance of Gun Fuse
and other Electric Circuits.
We, FRANCIS HENRY NALDER, HERBERT NALDER, CHARLES WILLIAM
SCOTT CRAWLEY, and ALFRED SOAMES, all of 16 Red Lion Street, Clerkenwell
in the County of Middlesex Electrical Engineers do hereby declare the nature of
this invention to be as follows:-
Our instrument is for testing the resistance of gun fuses or other circuits.
In series with the resistance to be measured, we place a source of electro-motive
force and a galvanometer of suitable resistance and of any well known form, and
generally reading over a scale which may be calibrated so that it reads direct in
terms of the resistance in series with it; or we mark the scale in any equivalent
way; such as "short circuit," "one fuse,"
," "two fuses" & "open circuit."
We often make the scale various colours corresponding to the various conditions
of the circuit, to minimise chance of error in reading.
When it is desirable to use but a very low electro-motive force, we insert in the
circuit a small resistance which may be easily varied, and also join the small
resistance in the circuit of a cell or cells of high resistance; or preferably of low
resistance, and having external resistance added; so that the electro-motive
force applied to the galvanometer circuit is only a small fraction of that of the
cell or cells.
By varying the above small resistance, or the resistance in the cell circuit or
both, the instrument can be adjusted to suit the electro-motive force of the cell or
cells, or any change in their electro-motive force or resistance, or in the resistance
of the circuit.
An Improved Instrument for Testing the Resistance of Gun Fuse
and other Electric Circuits.
We FRANCIS HENRY NALDER, CHARLES WILLIAM SCOTT CRAWLEY, and
ALFRED SOAMES, all of 16 Red Lion Street, Clerkenwell, in the County of
Middlesex, Electrical Engineers, and HERBERT NALDER, of "Coniston" Fox
Grove Road, Beckenham, in the County of Kent, 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:
Our instrument is for testing the resistance of gun fuses or other circuits.
In series with the resistance to be measured we place a source of electro-motive
force and a galvanometer of suitable resistance and of any well known form, and

page_text: in any convenient way, either instead of or in conjunction with the variation on
the stretched wire or its equivalent, thus increasing the range of the instrument.
We do not confine ourselves to this particular form of galvanometer, but
sometimes use any well known form of galvanometer.
Having now particularly ascertained and described the nature of our said
invention, we declare that what we claim is.
1. In an instrument for testing the resistance of gun fuse or other circuits, the
combination of a potentiometer apparatus for keeping the electro-motive-force
constant, and a galvanometer in series with the resistance to be measured.
2. In an instrument for testing the resistance of gun fuse or other circuits, the
combination of a potentiometer apparatus for keeping the electro-motive-force
constant, and a galvanometer with its scale marked directly in terms of the
measurements required in series with the resistance to be measured.
3. In an instrument for testing the resistance of gun-fuse or other circuits the
combination of a potentiometer apparatus for keeping the electro-motive-force
constant, and a galvanometer freely suspended in series with the resistance to be
measured.
4. In an instrument for testing the resistance of gun-fuse or other circuits, the
division of the scale into different coloured spaces.
5. The instrument substantially as described.
Dated this 13th day of September 1894.
C. W. S. CRAWLEY.
ALFRED SOAMES.
FRAS. H. NALDER.
HERBERT NALDER.