Year: 1886

page_text: Date of Application, 17th Nov., 1886.
Complete Left, 17th Aug., 1887.
Complete Accepted 20th Sept. 1887.
RESERVE
I, JOHN SMITH RAWORTH, of 112, Belvedere Road, Lambeth in the County of
Surrey, Engineer, do hereby declare the nature of this invention to be as follows:-
--
My invention which is applicable to various forms of voltmeters at present in use
has for object to make the calibration of each instrument dependent on one reading
only, that is to say, an instrument constructed according to my invention having been
tested by any given number of volts, the readings for any other number of volts may
be ascertained by simple calculation.
In carrying out my invention any of the well known arrangements of polarized or
soft iron needles, cores or plates influenced by electro magnets, solenoids, or the like,
or of moveable coils influenced by other coils or electro magnets are used, and the
counteracting springs or weights are so arranged that with a given difference of
potential, of say 10 volts, the indicator needle will point to the centre of the scale.
If a resistance equal to the resistance of the coils of the instrument be now inserted
it is obvious that the same deflection will now be obtained with 20 volts. By adding
equal resistances in succession the same deflection will be obtained with 30, 40, 50,
60 volts and so on. The resistance coils should be fixed in such a position and so
wound that they will have no direct magnetic influence on the needle. The various
contact knobs, buttons, or plates in connection with the resistances are so arranged
that in turning or sliding an index finger or arm to any required number on a scale
for, say, 50 volts, the requisite resistance will thereby be inserted in the circuit of the
instrument.
It is obvious that intermediate numbers of volts, say 45 or 47 may be measured by
the use of a smaller resistance which may be inserted in the circuit with the larger
resistance corresponding to say 40 volts.

page_text: In ordinary instruments for use with dynamos or accumulators the scale traversed
by the needle may be marked not only with the centre point to show that the exact
number of volts for which the instrument is set are being measured, but also with
other marks to right and left of the centre to indicate certain percentages of variation
from the fixed potential.
Thus if the instrument were set for 100 volts each degree to right or left of the
centre would indicate 1 volt above or below 100. But when set for 50 volts each
degree would indicate a volt of variation.
The exact positions of the said marks on the scale can be easily found by inserting
suitable resistances in circuit with a fixed source of electro motive force.
Dated this 17th day of November 1886.
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C.,
Agent for the Applicant.

page_text: Improvements in Volt Meters.
I, JOHN SMITH RAWORTH, of 112, Belvedere Road, Lambeth, in the County of
Surrey, Engineer, 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 is applicable to almost every form of volt meter at present in use, and
has for its object to make the calibration of each instrument dependent on one
reading only, by which I mean that an instrument constructed according to my
invention is such that, assuming it to have been tested by any given number of volts,
the reading for any other number of volts may be ascertained by simple calculation.
In carrying out my invention I use any of the well known arrangements of
polarized or soft iron needles, cores or plates influenced by electro magnets, solenoids,
or the like, or of movable coils influenced by other coils or electro magnets, and I
arrange the counteracting springs or weights so that with a given difference of
potential, say for example 10 volts, the pointer or index hand wlll point to the centre
of the scale. If a resistance equal to the resistance of the coils of the instrument be
now inserted, it is obvious that the same deflection will be obtained with 20 volts, and
by adding equal resistances in succession the same deflection will be obtained with
30, 40, 50, or 60 volts, as the case may be, and so on, according to the number of
successive equal additions made to the resistance.
The resistance coils are fixed in such a position, and wound in such a manner,
that when they are in use they have no direct magnetic influence on the indications
of the instrument; the various contact knobs, buttons or plates are so arranged that
in turning or sliding the index or indices to exhibit any number on the scale for, say,
for example, 50, a corresponding resistance will be thereby inserted in the circuit so as
to cause the index of the instrument to come to zero or to some point previously
determined upon when the electro motive force on the terminals of the instrument is
equal to the numerical indication on the dial or dials.
Intermediate numbers of volts, as for example 45 or 47 may be measured by the
use in addition of smaller proportional resistances which may be inserted in the
circuit together with the larger resistances in such a manner that the required
number may be made up by their sum.
In ordinary instruments the scale traversed by the pointer or index hand can be
marked not only with the centre or zero point, but also with other marks to right and
left of the centre to indicate certain per centages of variation from the potential which
would be indicated if the pointer or index hand were at the centre or zero point.
Thus if the instrument be set, and the resistance or resistances so arranged that the
pointer or index hand when at the centre or zero point of the scale indicates an
electro motive force in the terminals of the instrument of 100 volts, each degree of
deflection to right or left of the centre or zero might indicate 1 volt above or
below 100, as the case might be; and in such a case assuming the resistance or

page_text: resistances to be so arranged that the pointer or index hand when at the centre
or zero point of the scale would indicate an electro motive force of say 50 volts each
degree of deflection to the right or left of the centre or zero point might indicate
half a volt of variation.
The exact positions of the said marks on the scale can be easily found by inserting
a suitable resistance or suitable resistances in circuit with a fixed source of electro
motive force.
Fig. 2 a section at right angles to Fig. 1; and
Fig. 3 a diagram of the connections of a volt meter made in accordance with my
invention. The same letters of reference indicate the like parts in all the Figs.
where used.
A is a finely pivotted spindle on which are fixed two soft iron needles B, B, which
are influenced by four solenoids C, C, C, C, which are arranged to give opposite
polarity to the needles so that in combination they may not be influenced by any
external magnetic field. The couple produced by the attraction of the solenoid for
the ends of the needles is balanced by a small weighted lever D.
In portable instruments this weighted lever may be replaced by a spring.
The resistance coils marked E, E, E, have each a resistance equal to the sum of
the resistances of the four solenoids C, C, C, C. The knob F by means of the contact
spring G brings the coils E, E, E, E, into circuit in succession at the same time the
dial K, indicates the number of times the resistance of the four solenoids C, C, C, C,
has been multiplied by the introduction of coils E, E, E, E. A set of resistance
coils M. each equal to one-tenth of the sum of the resistance of the four solenoids is
brought into circuit by the knob N and the contact spring O. The dial in connection
with the knob N indicates the units of volts for which the instrument is set.
The pointer or index hand P, is fixed on the spindle A, and indicates on the scale Q
the variation between the actual difference of potential and the volts shown on the
dials, each degree on each side of the central division representing a variation of, say,
one per cent.
Fig. 3 clearly shows the electrical connections.
The special arrangements of needles and solenoids shown in the drawings are
convenient but not essential, any of the well known combinations may be employed
in connection with the resistances and dials.
Having now particularly described and ascertained the nature of the said invention,
and in what manner it is to be performed, I declare that what I claim is :-
A volt meter constructed with resistance coils whereby the indications of the
instrument can be proportionally varied, and with a dial or dials whereby the
indications can be read or interpreted, such dial or dials showing the proportionate
or relative variation between the reading of the instrument and the force acting upon
it, substantially as described with reference to the drawings annexed.
Dated 1018 1/10 day of August 1XX7
Wated 1018 1/10 day of Anonst. 1XX7
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Agent for the Applicant.