Improvements in the Construction of Ammeters and Voltmeters.
Year: 1896

page_text: Date of Application, 15th June, 1890
Complete Specification Left. 8th Mar.. 1897-Accepted, 17th Apr., 1897
Date of Application, 15th June, 1890
Complete Specification Left. 8th Mar.. 1897-Accepted, 17th Apr., 1897
PROVISIONAL SPECIFICATION.
Improvements in the Construction of Ammeters and Voltmeters.
I THOMAS JAMES BAKER of the Municipal Technical School Suffolk Street
Birmingham in the County of Warwick Science Teacher do hereby declare the
nature of this invention to be as follows:-
The drawing supplied herewith represents a vertical section through an ammeter
of the hydrometer type with my improvements included in it. V is a cylindrical
vessel closed at the top with a glass tube t. The latter carries a calibrated scale-
and is fastened to the top of the vessel V by means of a union joint not shown in
the drawing.
9. g. are two guide plates with a bevilled perforation in the centre of each and
with a few perforations near the edge for liquid ventilation or circulation. The
vessel V must be filled to a height a little above the upper guide plate g with any
suitable liquid (say petroleum).
The lower guide plate g is fixed in the position shown in drawing. The upper-
one g rests loosely upon a ring support fixed to the wall of the vessel V just below
its mouth, so that on lifting out the float by means of the index i the guide plate
comes away with it.
fis a float made of cork or of any other suitable substance carrying a soft iron
or magnetised steel wire and an aluminium or other suitable index i. The
dimensions of the float f must be so adjusted that when placed as shown, in the
liquid, it will float so as only just to touch the under surface of the upper guide
plate g when gravity is the only force acting upon it.
C is a section through a coil of insulated wire wound upon the lower half of the
vessel V.
The construction described above secures the following advantages :-
(1) The mass of the moving part of the instrument is very small and its
indications are very dead beat.
(2) The float can move with perfect freedom, but only in a vertical direction
in the axis of the vessel and between the two guide plates 9. g.
Hence there cannot be any friction between the float fand the inside wall of the
vessel V. Also the iron wire w moves only in a vertical direction and in the axis
of the solenoid C..
Under the conditions described, the indications of the instrument are perfectly
reliable.
The same current always produces the same displacement.
Dated this 13th day of June 1896.

page_text: COMPLETE SPECIFICATION.
Improvements in the Construction of Ammeters and Voltmeters.
I, THOMAS JAMES BAKER of the Municipal Technical School, Suffolk Street,
Birmingham in the County of Warwick, Science Teacher 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 :-
The drawing supplied with the Provisional Specification represents a vertical
section through an ammeter of the hydrometer type with my improvements included
in it.
V is a cylindrical vessel closed at the top with a glass tube t. The latter
carries a calibrated scale and is fastened to the top of the vessel V by means of a
union joint not shown in the drawing.
9. 9. are two guide plates with a bevilled perforation in the centre of each and
with a few perforations near the edge for liquid circulation.
The vessel V must be filled to a height a little above the upper guide plate g with
any suitable liquid.
The lower guide plate g is fixed in the position shown in the drawing. The
upper one g rests loosely upon a ring support fixed to the wall of the vessel V just
below its mouth, so that on lifting out the float f by means of the index i the guide
plate comes away with it.
is a float consisting of a thin walled hollow cylinder or sphere made of any
suitable material such as glass or xylonite or it may consist of a cork varnished to
prevent absorption of the liquid, but the varnish chosen must be of a kind unacted
upon by the liquid in which the float f has to be suspended.
The float carries a soft iron wire w and an aluminium or other suitable
index i.
The dimensions of the float f must be so adjusted that when placed as shown in
the liquid it will float so as only just to touch the under surface of the upper guide
plate g when gravity is the only force acting upon it.
C is a section through a coil of insulated wire wound upon the lower half of the
vessel V.
The construction described above secures the following advantages:-
(1) The mass of the moving part of the instrument is very small and its
indications are very dead beat.
(2) The float can move with perfect freedom, but only in a vertical direction
in the axis of the vessel V and between the two guide plates g. 9.
Hence there cannot be any friction between the float f and the inside wall of the
vessel V. Also the iron wire w moves only in a vertical direction and in the axis
of the solenoid C.
Under the conditions described the indications of the instrument are perfectly
reliable.
The same current value always produces the same displacement.
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) The invention and use of the guide plates g. g.
(2) The particular construction of the moving part of the instrument lettered i. f.w.
in the drawing.
Dated this 6th day of March 1897.
THOMAS JAMES BAKER.