Improvements in Apparatus in which Electrical Measures are Obtained by the Aid of a Wire or Filament Heated by the Passage of a Current.
Year: 1890

page_text: Date of Application, 11th Apr., 1890
Complete Specification Left, 12th Jan., 1891-Accepted, 28th Mar., 1891
PROVISIONAL SPECIFICATION.
Improvements in Apparatus in which Electrical Measures are
Obtained by the Aid of a Wire or Filament Heated by the
Passage of a Current.
I, FREDERICK HERBERT WILLIAM HIGGINS, of 17 and 18, Cornhill, in the
City of London, Electrician, do hereby declare the nature of this invention to be as
follows:-
This invention has for its object improvements in apparatus in which electrical
measures are obtained by the aid of a wire or filament heated by the passage of a
current.
In such instruments in order to retard the cooling of the electrically heated wire
or filament and thereby to increase the sensitiveness of the instrument I enclose it
in a chamber in which a vacuum is maintained.
Thus in a well known form of volt meter in which difference of potential is
measured by the expansion of an electrically heated wire I enclose this wire in a
vacuous chamber and thereby greatly increase the sensitiveness of the meter.
Or the sensitiveness may be adjusted as may be desired by enclosing the wire
in a chamber in which the air pressure can be readily regulated.
In another form of instrument the wire heated by the current is enclosed in the
bulb of an air thermometer; in this case I cause the bulb to be contained in a
vacuous chamber or in a chamber in which the air pressure may be regulated as
required.
Dated this 11th day of Anvil 1800
F. H. W. HIGGINS.
COMPLETE SPECIFICATION.
Improvements in Apparatus in which Electrical Measures are
Obtained by the Aid of a Wire or Filament Heated by the
Passage of a Current.
1, FREDERICK HERBERT WILLIAM HIGGINS, of 17 and 18, Cornhill, in the
City of London, Electrician, 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 has for its object improvements in apparatus in which electrical
measures are obtained by the aid of a wire or filament heated by the passage of a
current.
In such instruments in order to retard the cooling of the electrically heated wire
or filament and thereby to increase the sensitiveness of the instrument I enclose it
in a chamber in which a vacuum is maintained.
Thus in a well known form of volt meter in which difference of potential is
measured by the expansion of an electrically heated wire I enclose this wire in a
vacuous chamber and thereby greatly increase the sensitiveness of the meter.
Or the sensitiveness may be adjusted as may be desired by enclosing the wire in
a chamber in which the air pressure can be readily regulated.
In another form of instrument the wire heated by the current is enclosed in the
bulb of an air thermometer; in this case I cause the bulb to be contained in a
vacuous chamber or in a chamber in which the air pressure may be regulated as
required.

page_text: The drawing annexed shews various views of a
invention applied to it.
"Cardew" volt meter having my
Figure 1 is a face view partly in section and Figure 2 a longitudinal section.
Figure 3 is a section taken through one of the terminals.
A is the wire to be heated by the current, its two ends are secured to two 5
screws B, B which are insulated from one another.
The wire passes down from one screw B through the tube which extends
outwards from the cylindrical portion of the casing, then around a roller at the end
of the tube, then back and around a roller C and again around another roller at the
end of the tube, then around a roller D, around another roller at the bottom of the 1
casing, around another roller C, another roller at the end of the tube and back to
the other screw B. The axis of the rollers C has a hook attached to it, a cord is
led from this hook around a small wheel on the axis of a toothed wheel E and is
then attached to a spring F. The toothed wheel E gears with a pinion on the axis
of the index hand or pointer G so that any contraction or expansion of the wire is
shewn by the position of this pointer.
Current is conveyed to one end of the wire from the terminal H and to the
other end from the terminal 1 through a safety fuse J.
So far the meter is of ordinary construction.
By my invention I secure the glass K over the front of the casing in such a
manner as to secure an air tight joint between them and also form air tight
joints at the points where insulated conductors are led into the casing from the
terminals H, I, and I also provide means for obtaining a vacuum in the casing and
thien closing it air tight.
The glass K and the seating of the casing which it is to rest against may be
ground flat and the two be cemented together with Canada balsam and it may be
further held to the casing by a ring L made to bear against its exterior a soft
packing ring being placed between them as shewn..
An air tight joint may be secured where an insulated conductor fróin each
terminal is led through the casing in the manner shewn at Figure 3. The terminal
is formed of a pin M screw threaded at each end and having on it a collar M*.
The longer portion of the pin M is passed through an ebonite collar M', through
an india rubber washer M³ through an ebonite washer M³ which fills the hole
formed through the casing, then through a block of ebonite N which is cemented
to the interior of the casing and then has a nut N' screwed on to its end to bind all
tightly together. The second nut N is for holding the conducting wire which
is led from the pin to one of the screws B.
To allow of a vacuum being formed and maintained in the casing there is
provided at the extremity of the tubular portion of the casing a screw nozzle
containing within it a self closing valve formed like the inlet valve of an air pump.
By this nozzle the meter can be coupled up with an air pump and a vacuum then
formed in the casing. When the required vacuum has been obtained the meter can
be disconnected froin the air pump and a cap screwed on to the nozzle and made to
bear tightly against a washer interposed between its end and the end of the tube of
the casing, or the joint between the cap and the casing might be made air tight by
Canada balsam.
The sensitiveness of the meter can be adjusted to the extent required by forming
a more or less complete vacuum in the casing-or even in some cases by raising the
pressure of air in the casing to above atmospheric pressure-in this case an inlet
valve by which air under pressure could be supplied to the casing would have to be
provided.
As above stated other instruments in which indications are given by the heating
of a wire by the passage of an electric current through it may similarly be
contained in a vacuous chamber or in a chamber in which the air pressure may be
regulated as required.

page_text: 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 :-
1. The construction of volt meters and other apparatus in which measures are
obtained by the aid of a wire or filament heated by the passage of a current in
such a manner that a vacuum or partial vacuum may be maintained around the wire
or filament.
2. The construction of volt meters and other apparatus in which measures are
obtained by the aid of a wire or filament heated by the passage of a current in such
a manner that the sensitiveness of the instrument may be readily regulated by
adjusting the air pressure in the chamber surrounding the wire or filament.
Dated this 19th day of January 1891
CARPMAEL & Co.,
Agents.