Improvements in Electrical Measuring Instruments.
Year: 1893

page_text: Date of Application, 6th Dec., 1893
Complete Specification Left, 6th Sept., 1894-Accepted, 24th Nov., 1894
PROVISIONAL SPECIFICATION.
Improvements in Electrical Measuring Instruments.
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 the purpose of obtaining a register of the maximum or
minimum current which has flowed in a circuit.
We sometimes use a piece of paramagnetic material working against any well
known controlling force in a magnetic field set up by the current: For example,-
An iron needle or plate may work between the poles of an electro-magnet
energised by the current, or when small currents are to be measured we sometimes
use a moving coil in a more or less permanent magnetic field.
0
We attach a pointer to the moving part in the usual way, and also have an inde-
pendent pointer or index, actuated by the first one in such a way that it will remain
in whatever position it is pushed to by the first pointer.
We usually prefer to damp the moving needle or coil to prevent its pushing the
independent pointer further than the point to which it should go.
We may use any well known form of damping but preferably immerse the
moving needle in a viscous fluid, or especially in the case of a moving coil we may
use magnetic damping.
Dated this Sixth day of December 1893.
Improvements in Electrical Measuring Instruments.
We, FRANCIS HENRY NALDER, HERBERT NALDER, of "Coniston " Beckenham,
Kent, CHARLES WILLIAM SCOTT CRAWLEY, and ALFRED SOAMES, all of
16 Red Lion Street, Clerkenwell, in the County of Middlesex do hereby declare
the nature of this invention and in what mauner the same is to be performed,
to be particularly described and ascertained in and by the following statement :-
Our instrument is for the purpose of obtaining a register of the maximum or
minimum current, which has flowed in a circuit.
We sometimes use a piece of paramagnetic material working against any well-
known controlling force in a magnetic field set up by the current: "For example-
An iron needle or plate may work between the poles of an electro-magnet energised
by the current, or when small currents are to be measured we sometimes use &
moving coil in a more or less permanent magnetic field.
We attach a pointer to the moving part in the usual way, and also have an inde-
pendent pointer or index, actuated by the first one in such a way that it will remain
in whatever position it is pushed to by the first pointer.

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We usually prefer to damp the moving needle or coil to prevent its pushing the
independent pointer further than the point to which it should go.
We may use any well known form of damping but preferably immerse the
moving needle in a viscous fluid, or especially in the case of a moving coil we may use
magnetic damping.
Figure 1. of the accompanying drawing shows a vertical section, Fig. 2. a plan
of a construction of an apparatus for carrying out the above invention. Like
letters apply to like parts in both figures. A. A. are the poles, and A 1. A 1. the
legs, and A 2 the yoke of an electro magnet energised by the current which
passes round the coils B. B, only part of the winding being shown, the said coils
being connected to terminals N. N. C is a soft iron or steel plate, rigidly attached
to a spindle D, working in bearings E. E., and carrying rigidly attached to it, a
pointer F. The whole moving system is controlled by a spring G. the plate itself
being immersed in a bath of oil, or other viscous fluid, H. a loose pointer J pivoted
at K. close to the spindle D. The pointer F has a projection on it, or is bent
down, so that when moving forwards it moves J with it over the scale M, which
may be divided in.amperes or volts, or any desired divisions. L. L. L. is the case
of the instrument. P is a small plate covering up a small hole through which. J
can be reset, when required, by inserting a rod, or other convenient means.
In Fig. 2, J is shown as having been already pushed over the scale and left
there.
.
From the above description it will be seen that when the current passes
through B. B. the plate C, which is initially in the position shown in Figure 2, will
tend to take up a position in the line joining A. A. against the control of the spring G,
the pointer F thus moving counter-clock-wise, will carry J forward with it, an amount
depending on the current flowing. The movement of C is very slow owing to the
viscosity of the liquid in which it is immersed, and thus the pointer F. never swings
beyond its final position of rest. When the current decreases F will return
towards its original position, leaving J stationary. The pointer J is thus a register
of the maximum movement of F, & therefore of the current. The pointer J can
be reset when required, through the hole covered by the plate-P.
We do not confine ourselves to the particular form shown, but may use any well-
known form of ammeter or voltmeter, with liquid or magnetic damping, as in the
well known D'Arsonval galvanometer, actuating an independent pointer which is
left in its maxinium or minimum position when the current is reduced or increased.
We may of course use the same means of obtaining a register of the minimum.
current that has flowed through the instrument by putting an independent pointer
on the other side of the working pointer.
Having now fully ascertained and described the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what
we claim is
-
1. In an electrical ineasuring instrument for the purpose of obtaining a 'register
of the maximum'or minimum current that has passed through the instrument, the
combination of a moving part actuated by the current whose maximum or minimum
is to be registered, a damping arrangement and an independent pointer or index.
2. An electrical measuring instrument substantially as described.'
6.
C. W. S. CRAWLEY.
"ALFRED SOAMES.
FRAS. H. NALDER.
HERBERT NALDER.