Improvements in Electrical Measuring Instruments.
Year: 1894

page_text: Date of Application, 20th Mar., 1894-Accepted, 5th May, 1894
COMPLETE SPECIFICATION.
[Communicated from abroad by EDWARD WESTON, of Newark, New Jersey,
United States of America, Electrician.]
Improvements in Electrical Measuring Instruments.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent
Agents, 45 Southampton Buildings, 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:-
The invention is an instrument for simultaneous measurement of the current and
the potential difference on a circuit, and hence of the watts-and this whether the
current on said circuit be direct or alternating.
It embodies two coils-one of low resistance and placed in main circuit, and the
other movable in the field of the first coil and placed in a circuit of relatively high
resistance. The movement of the movable coil is counterbalanced by a coiled
spring, which also serves to lead the current to said coil. By reason of this con-
struction the movable coil turns on its pivots when traversed by the current, and
finds its own equilibration; so that, in this way, the watts are directly measured
and indicated on the scale of the instrument.
In the accompanying drawing,
Fig. 1 is a plan view of the working parts from the rear of the supporting
plate.
Fig. 2 is a section on the line X X of Fig. 1.
Fig. 3 is a detail view of the fixed coil.
Fig. 4 shows the conductor of which said coil is made extended.
Similar numbers of reference indicate like parts.
The working parts are supported on the rear of plate 1 of ebonite, which forms
the cover of box 2. In the rear of plate 1 is a recess, 3, having a curved slot
This slot is not shown in the
through which the instrument scale can be seen.
drawings, because covered by scale-plate 4, which is fastened to plate 1 by offset 5
and screws 6.
The index needle, 7, extends between the scale-plate and the slot.
In scale-plate 4 there is a curved slot behind which is the mirror 8 held by clips, 9.
This mirror reflects the index needle and prevents parallax in reading. On plate 1
are two posts, 10, connected by bar 11, which is insulated from them by rubber
disks, 12. Said posts are also connected by cross-bar 13 in an opening in plate 1.
which opening is closed by plate 14. In bars 11 and 13 are steps, 15, receiving
pivots, 16, of movable coil 17. Coil 17 is made of many turns of fine wire, and the
pivots 16 are secured to its exterior in any suitable way and directly opposite one
another, as shown. To each pivot is attached the end of a coiled spring, 18. The
free ends of springs 18 are attached to arms, 19, supported on collars turning on
steps 15 outside of bars 11 and 13. By turning these arms the tension of the
springs 18 can be adjusted so that they offer more or less resistance to the move-
ment of the movable coil on its pivots. Index needle 7 is carried by pivot pin 16,
and therefore moves with coil 17.
The fixed coils are represented at 20 and 21. Each consists of a copper rod.
preferably of quadrangular cross-section, shaped as shown in Fig. 4, so that all
parts of each turn, as a, b, c, will stand in the same plane. By this means I reduce
the length of the coil and concentrate the field of force in which the movable
coil 17 is situated.
23 and 26 are broad strips of copper secured beneath plate 1, and are provided

page_text: with clamping screws 27 and 28. Strip 23 bends down at 24, and has its end 25
parallel to the main portion. Fixed coil 20 is attached to end 25. The other end
of coil 20 is secured to a flange, 31, on a copper block, 22, placed between strips 23
and 26.
One end of the other fixed coil 21 is secured to strip 26 at 29. The other end
of coil 21 is fastened to flange 30 on copper block 22. The coils 20 and 21 are
therefore on opposite sides of post 10, and therefore disposed symmetrically with
reference to coil 17. Each fixed coil, 20 and 21, is supported entirely by its
terminals fastened respectively to one strip and block 22, and hence by removing
the screws by which it is attached, either coil is easily removed from the
instrument.
The circuit of the coils 20 and 21 proceeds from clamping screw 27 through
strip 23 to coil 20, to copper block 22, to coil 21, to strip 26 and to clamp screw 28.
This is the low resistance circuit. The high resistance circuit proceeds from
binding-post 32 by wire 33 to contact spring 34, to another contact spring 35, by
wire 36 to bar 11, to coiled spring 18, to coil pivot 16, through coil 17 to the other
coil pivot 16, to bar 19 and by wire 37 to binding-post 38. There are two distinct
circuits, which may be put in parallel relation or in series in the instrument as the
user may desire.
I will now refer to an attachment for retarding or dampening the motion of the
index or pointer so as to prevent undue vibration thereof. On one pivot of coil 17
is the disk 39, on which bears a leaf-spring, 40, carried on the end of piston rod 41.
This rod is attached to piston 42 in cylinder 43. Between piston 42 and the
cylinder head is a spiral spring, 44, which tends to raise the piston until a pin, 45,
on the rod 41 meets the cylinder head; hence spring 40 is normally held against
disk 39, and opposes, by friction, rotation of said disk. Piston 43 is guided by
projection 46 entering a slot in the side of the cylinder. Also in the side of the
cylinder is an opening which receives the ends of contact springs 34 and 35. Said
ends are normally separated, and the end of spring 34 is also separated from the
end of piston rod 41. 47 is a push button bearing against the end of spring 35.
The operation of this device is as follows: Normally the leaf-spring 40 bears on
disk 39, and prevents movement of the fixed coil. When push button 47 is pressed
down, the ends of springs 34 and 35 are brought together, establishing current
through coil 17. As button 47 is pressed further, spring 34 is brought into contact
with piston rod 41, and then that rod and the two contact springs are brought
downward, the piston 43 compressing the coiled spring 44; hence the pressure of
leaf-spring 40 on disk 39 is gradually relaxed, allowing coil 17 to move as slowly
as may be desired to its indication, after which further pressure of button 47 moves
spring 40 away from disk 39, leaving coil 17 free. Button 47 may then be held in
place by any suitable means. After the scale reading is taken push button 47 is
released, at once separating springs 34 and 35, breaking contact in the circuit, so
that the index needle goes back to zero, and afterwards the rise of piston 43 brings
leaf-spring 40 again in contact with disk 39.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondent I declare that what I claim is
1. An electrical measuring instrument having a fixed coil consisting of two or
more turns constructed so that each turn has all its parts in the same plane,
whereby the length of said coil is reduced and the field rendered more
concentrated.
2. An electrical measuring instrument having a fixed coil consisting of two or
more turns constructed so that each turn has all its parts in the same plane, as and
for the purpose specified, and a movable coil controlling the index and pivoted
within said fixed coil.
3. An electrical measuring instrument having a fixed coil constructed and
detachably supported as specified, in combination with a movable coil pivoted

page_text: therein and provided with counterbalancing spiral springs, the said movable coil
controlling the index.
4. The construction and arrangement of the two fixed coils as hereinbefore set
forth and the supports wherefrom said coils laterally project, and of the movable
coil symmetrically disposed and pivoted within said fixed coils.
5. In combination with the movable coil and its friction disk, the dampening
device herein set forth comprising the presser finger, piston rod, piston, spring
acting thereon, enclosing cylinder and push button.
Dated this 20th day of March 1894.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.