Improvements in the Construction of Standards of Electrical Resistance.
Year: 1896

page_text: Date of Application, 27th Feb., 1896
Complete Specification Left, 21st Nov., 1896-Accepted, 24th Dec., 1895
PROVISIONAL SPECIFICATION.
Improvements in the Construction of Standards of Electrical
Resistance.
ANDREW DUNCAN HUGHSON, 51 Wightman Road, Harringay London, N.
do hereby declare the nature of this invention to be as follows:-
In the
The invention applies to that part of the mount or casing of a standard resistance
coil which carries the standard wire, and which is usually immersed in a bath of
water or other liquid. The object of the invention is to determine the tempera-
ture of the standard wire at the time of test with greater precision than has
hitherto been possible, by enabling such standard wire to rapidly and certainly
acquire the temperature of the surrounding water or other liquid, and thereby
greatly increase the accuracy and facility with which tests and comparisons can be
made. This the inventor proposes to carry out in the following manner.
case of a standard coil of ohm resistance, a suitable length of insulated
platinum silver or other wire is approximately adjusted for resistance and doubled
upon itself in the usual manner. The wire being then carefully varnished and
dried, is then inserted in the bore of a small metallic tube, preferably of seamless-
drawn copper, the diameter of such bore being just large enough to admit of the
easy insertion of the doubled wire. The outer end of this small tube has been
previously closed by a soldered plug and the inner end inserted into the side, and
close to the lower end, of another and larger metal tube, and attached thereto by a
suitable soldered joint. The doubled wire having been inserted in the small tube,
such tube is then coiled or wound into a volute, or spiral, or other suitable form,
and is held in position by coupling blocks attached to the radial arms of a metal
wheel or spider screwed to the lower end of the larger tube; or by brackets or
other suitable mechanical device. To the upper end of the larger tube is attached
an insulating cap or caps carrying the copper terminal rods in the usual manner.
The inner ends of these copper rods pass down the larger tube and terminate close
to the ends of the standard wire, which project from the inner end of the small
tube. The joints can then be made and the final adjustment of the resistance
carried out, on the completion of which the lower end of the larger tube is closed
with a metal disc and soldered up. The outer ends of the copper terminal rods are
bent over to dip into mercury connecting cups in the usual manner.
By this device the insulated standard wire is wholly enclosed in a metal sheath
or covering of small mass and thermal capacity but of high thermal conductivity.
On placing the device in a bath of water or other liquid the wire will quickly
attain the temperature of the surrounding liquid, and such temperature can be
ascertained with great ease, precision, and certainty by immersing an ordinary
thermometer in the liquid immediately surrounding the coiled tube.
In the cases of standards of higher resistances than one ohm in which longer
lengths of wire are usually employed the inventor proposes to double such longer
lengths upon themselves two or more times before insertion in the small tube and
so avoid the inconvenience of too great a length of such tube.
Dated this 27th day of BishoSOC
ANDW. D. HUGHSON.

page_text: Improvements in the Construction of Standards of Electrical
Resistance.
I, ANDREW DUNCAN Hughsos Electrician, of 51 Wightman Road. Harringay
in the County of Middlesex 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:-
My invention relates to improvements in the construction of that part of the
mounting or easing of a standard resistance coil carrying the standard wire, which
part is usually immersed in a bath of water or other liquid.
The object of my invention is to enable the user of the standard coil to determine
the temperature of the standard wire at the time of test with greater certainty
and exactitude than has hitherto been possible. This attain by placing the
standard wire within the bore of a small metallic tube. The tube being of high
thermal conductivity and small thermal capacity will allow the enclosed wire to
acquire the temperature of any liquid in which such tube is immersed with great
rapidity and certainty, and this temperature can be ascertained with great ease and
precision by means of an ordinary thermometer, the bulb of which is immersed in
the liquid immediately surrounding the tube.
In applying my invention to the construction of a standard coil of one ohm
resistance proceed as follows. A length of silk covered platinum silver or other
suitable wire is approximately adjusted for re-istance and doubled upon itself in
the usual manner to avoid inductance. The wire is carefully varnished with a good
insulating varnish and thoroughly dried. It is then inserted in the bore of the
small metallic tube, which may be of seamless-drawn copper or other metal of good
thermal conductivity, the bore being just large enough to admit of the easy
insertion of the doubled wire. One end of this tube has been previously plugged
and soldered and the other end inserted into the side, and close to the lower end
of another and larger tube, to which it is attached by a soldered joint. The small
tube is then bent or coiled into a volute, or spiral or other suitable form and is
held in position by coupling blocks or clamps attached to the radial arms of a
metal wheel or spider berewed to the lower end of the larger tube. To the upper
end of this larger tube is attached an insulating cap through which pass the copper
terminal rods in the usual manner. The inner emils of these copper rods pass down
the larger tube and terminate close to the junction of the smaller tube, from which
project the two ends of the standard wire. The ends of the wire are then
attached to the ends of the copper rods by suitable soldered joints and the final
adjustment of the resistance carried out. The lower end of the larger tube is then
closed by a metal dise and the joint soldered. The outer ends of the copper
rods are bent over in the usual manner to dip into mercury cups for making
connections.
Referring now to the accompanying drawings in order to more clearly explain
the manner in which my invention may be carried into effect.
Fig. 1. is an elevation, partly, in section, of an instrument containing the
improvements previously detailed.
Fig. 2. is a plan, partly in section, of the lower part of such instrument with the
attached small metallic tube carrying the standard wire.
Fig. 3 is a plan of the upper part carrying the copper connecting rods.
A is a brass tube, to the lower end of which is attached the small metallic
tube B, by a soldered joint at the point p From this end of the tube B the two
ends of the standard wire e project into the larger tube A and are soldered to the

page_text: lower extremities of the copper rods C. The lower ends of the rods C pass
through and are steadied by an insulating disc D fitting the tubo A. The small
tube 13 is coiled into a volute as shewn, and is held in position by means of the
blocks or clamps a screwed to a three-armed wheel or spider b.
Three of the screws shewn at s fixing the clamps to the wheel or spider are
formed with long projecting heads and act as feet for the instrument to stand upon
when placed in the water bath. The plug closing the outer end of the small
tube B is shown at c. The lower end of the tube A is closed by a metal disc d'
and sealed by the soldered joint at e after the adjustment of the standard wire for
resistance has been completed. At f Figs. 1. 2. & 3 are brackets for carrying an
ordinary thermometer, the bulb of which rests on the coils of the small tube B..
E Figs. 1 & 3 is an insulating cap screwed to a flange F on the upper end of the
tube A and carrying the copper rods C which are bent over to dip into mercury
cups in the usual manner.
In constructing standards of higher resistances than one ohm, in which finer
wire of greater length is generally used such greater lengths of wire may be
doubled upon themselves four six or more times to enable them to be inserted in a
tube of suitable bore and convenient length.
Having now particularly described and ascertained the nature of my said inven--
tion and in what manner the same is to be performed, I declare that what I
claim is-
1. In standards of electrical resistance, the placing or sheathing of the standard
wire within the bore of a small metallic tube to enable such wire to rapidly acquire
the temperature of any liquid in which such tube may be immersed.
2. In standards of electrical resistance, the particular disposition of the small
metallic tube with the method of attaching, supporting, and fixing the same-
substantially as described.
Dated this 21st day of November 1896
ANDW. D. HUGHSON.