Improvements in Electrical Measuring and Indicating Instruments.
Year: 1898

page_text: Date of Application, 7th Apr., 1898
Complete Specification Left, 7th Jan., 1899-Accepted, 18th Feb., 1899
PROVISIONAL SPECIFICATION.
Improvements in Electrical Measuring and Indicating Instruments.
I, ARTHUR CECIL HEAP, of The Firs, Penn, in the County of Bucks, Electrical
Engineer, do hereby declare the nature of this invention to be as follows:-
<<
"
This invention relates to the construction and use of voltmeters in such a
manner that they indicate the potential at the distant end or feeding point'
of a pair of mains supplying electric current wihout the use of special wires
connecting that point and the place where the voltmeter is working.
I take any low reading voltmeter, but preferably one of the permanent magnet
moving coil type, and connect in the following manner:-
Across the mains at the near end, I connect a suitable high resistance, and
at the same point in the main, sad in series with it (the main) I put a suitable
low resistance which is capable of carrying the total current in the main; one
terminal of the indicating instrument is connected to a point on the high
resistance, the position of which for a given voltmeter, depends on the total
fall in volts on the mains from the near end to the feeding point, when the
maximum current is passing, the other terminal is connected to one end of the
standard resistance, and the high resistance and standard resistance are
arranged in relation to one another, and the direction of the currents passing
in them, that the fall of potential over the standard resistance is opposed to the
fall over the portion of the high resistance in use.
SO
In practice, I prefer that the high resistance mentioned above should be inside
the case of the voltmeter which has then three terminals.
In the case of a 3 wire system, where it is desirable that the fall of potential
in the 3rd. wire should be indicated, I employ two instruments, one on the
positive and one on the negative side and construct the voltmeter of two distinct
parts, in the case of an instrument of the permanent magnet type the moving
coil has two windings the ends of which are brought out separately to four ter-
minals on the instrument, in the case of a soft iron instrument the field coil is
made up of two distinct windings similarly brought out to terminals.
A separate standard resistance is then placed in each main and in the 3rd. wire,
the instruments are then connected; the direction of the currents in the standard
and high resistance being arranged as in the first case and the direction of
currents in the two windings of the voltmeter is such that they help each other
The above method of connecting and constructing voltmeters may be used
with either indicating or recording instruments.
Dated this 7th day of April 1808
COMPLETE SPECIFICATION.
Improvements in Electrical Measuring and Indicating Instruments.
I, ARTHUR CECIL HEAP, of The Firs, Penn, in the County of Bucks, Electrical
Engineer, do hereby declare the nature of this invention and in what manner
[Price 8d.]

page_text: the same is to be performed, to be particularly described and ascertained in and
by the following statement:-
This invention relates to the construction and use of voltmeters in such a
manner that they indicate the potential at the distant end or "feeding point"
of a system of mains supplying electric current without the use of special wires
connecting that point and the place where the voltmeter is working.
I take any low reading voltmeter, but preferably one of the permanent magnet
moving coil type and connect in the following manner:
Across the mains at the near end, I connect a suitable high resistance, and
at the same point in the main, and in series with it (the main) I put a suitable
low resistance which is capable of carrying the total current in the main: one
terminal of the indicating instrument is connected to a point on the high
resistance, the position of which for a given voltmeter, depends on the total
fall in volts on the mains from the near end to the feeding point, when the
maximum current is passing, the other terminal is connected to one end of the
standard resistance, and the high-resistance and the standard resistance are so
arranged in relation to one another, and the direction of the currents passing
in them, that the fall of potential over the standard resistance is opposed to the
fall over the portion of the high resistance in use.
In practice, I prefer that the high resistance mentioned above should be inside
the case of the voltmeter which has then three terminals.
In the case of a 3 wire system, where it is desirable that the fall of potential
in the third wire should be indicated, I employ two instruments, one on the
positive and one on the negative side and construct the voltmeter of two distinct
parts, in the case of an instrument of the permanent magnet type the moving
coil has two windings, the ends of which are brought out separately to four ter-
minals on the instrument in the case of a soft iron instrument the field coil is
made up of two distinct windings similarly brought out to terminals.
A separate standard resistance is then placed in each main and in the third wire;
the instruments are then connected: the direction of the currents in the standard
and high resistance being arranged as in the first case and the direction of
currents in the two windings of the voltmeter is such that they help each other.
The above method of connecting and constructing voltmeters may be used
with either indicating or recording instruments.
In the accompanying drawings:-
Fig. I shows clearly the method of connecting up, and Fig. II the construction
of the several parts of my instrument.
In the case of the two wire system, a a, is the feeding point of a system of
mains at which it is desired to know the potential in volts, this potential being
that of the generator g less the drop due to the resistance of the mains and the
current passing in it.
At the near end I connect a high resistance R, which may be made of some
metal having a low temperature resistance co-efficient, or part of wire having a
high temperature resistance co-efficient, and part of wire having a low tem-
perature resistance co-efficient, according to requirements well known in the con-
struction of similar instruments. At the same point d in the main I connect
electrically a standard resistance SR (which may be made of copper, or
other material, but preferably of copper capable of carrying the total current
in the mains, and in the case of the copper standard having the same cross
section as the mains) and the high resistance R, in such a manner that the fall
of potential over the standard resistance, which in practice is about 1 volt, is
opposed to the fall of potential in the portion of the high resistance R between d
& c I then connect my voltmeter across the points & c. The point eat
which the voltmeter is connected to the high resistance varies according to the
resistance of the mains and is so chosen that when the maximum current passes
in SR the reading of the voltmeter is reduced by an amount equal to the product
of the resistance of the mains M M, and the current passing.

page_text: I also provide another adjustment on the standard resistance SR in order
that these instruments may be easily adjusted if the resistance of the mains
varies; this is done by having a sliding contact H Fig. 2 on the standard
resistance SR, by moving this, a part, or the whole of the drop of potential in
the standard resistance S R may be made to react on the voltmeter V; this
slider may be made to work over a scale J which may be one of even divisions
or a scale of resistances of feeders having a known current carrying capacity,
by this means if I know the resistance of the mains M M¹ I can set my slider
against the division of the scale, marked with this value and should then have
adjusted my voltmeter without any further reference to the feeding point voltage
at a a. In practice it will be found best to adjust these instruments by taking
simultaneous readings of the voltage at a a, and d d and setting the slide H
until the voltmeter V reads the same as the voltmeter at the feeding point a a
Fig. 3 is a diagram of the connections of instruments for a three wire system,
and
Fig. 4 shows the construction of the several parts of such instruments of the
moving coil permanent magnet type.
Voltmeter V, indicates the volts between a, a, and voltmeter V₂ the volts
between 4
1
Referring to Fig. 4, voltmeter V₁ has two distinct windings w, w, one end
of the winding, being connected as shown to the standard resistance S, R, and
the other end to a point in the resistance R, and as in the case of the two
wire instrument the falls of potential over these two resistances S, R, and R,
oppose one another: the other winding w, is connected to another standard
resistance S, R, placed in the third wire of the system and to another point
the resistance R, the direction of the currents in the two windings w₁ w, is so
arranged that they both tend to deflect the pointer of the voltmeter in the same
direction.
in
The action of the several parts of these instruments is as follows:-When
there is no current in the mains M, M, the effect of the current passing in the
two windings w, w, of instrument V, is such as to produce the deflection of the
pointer corresponding to the normal voltage of the generator g₁, the resistances
of S, R, & S, R, being negligable as compared with the resistance of that portion
of resistance R, between d₂ and d when current passes in main M, the fall
of potential over S, R, opposes that over part of the resistance R₁, the
current in the winding e, decreases and therefore the reading of the voltmeter
falls. The amount of this fall being arranged according to the resistance of the
main by choosing the point e, in the resistance R, and also by adjusting the
position of the slider H₁ so that the drop in the readings of the instrument in
volts is equal to the product of the amperes in the main M, and its resistance.
In the same way the point is so chosen and the slider I, on the standard
resistance is so adjusted that the effect of the current in winding w, when
current passes in main M, is such that the needle of the voltmeter falls by an
amount equal to the drop of volts in the main M, and as the action of the
currents in the two windings i, on the needle is in the same direction, the
effects are added together, and the voltmeter indicates the volts at
The voltmeter V, is constructed in an exactly similar manner and indicates
the volts between a
In order that the indications of the instrument may take into account the
increase in resistance due to rise of temperature of the main either through the
current passing or changes of air temperature, I make the standard resistances
S, R, S, R, S, R of the same metal as the mains. Figs. 5 and 6 show an
instrument of the soft iron type as constructed for my purpose, in this case the
field bobbin B has two separate windings, each acting in the same way on
the soft iron needle carrying the pointer P, the other details are the same as
those of the permanent magnetic swinging coil type of instrument.
3

page_text: In all the above cases the indicating voltnieter may be replaced by a recording
voltmeter constructed in exactly the same manner.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is-
(1.) An instrument substantially as described consisting of voltmeter either
indicating or recording, reading the difference of potential between a point in a
high resistance placed across the mains of a supply system and a point on a
standard resistance in series with the mains at the same point as the high resis-
tance and carrying the total current in the mains. The falls of potential over
the high resistance, which varies with the station pressure and that over the
standard resistance which varies with the current passing being electrically
opposed to one another.
(2.) The combination as described consisting of voltmeter either indicating or
recording, reading the difference of potential between a point in a high resistance
placed across the mains of a supply system and a point on a standard resistance
in series with the mains at the same point as the high resistance and carrying
the total current in the mains. The falls of potential over the high resistance,
which varies with the station pressure and that over the standard resistance which
varies with the current passing being electrically opposed to one another. The
point of contact on the high resistance being chosen so that when the two falls
of potential over the high resistance and the standard resistance are opposed to
one another the pointer of the voltmeter falls by an amount equal to the drop in
the mains and therefore indicates the voltage at the far end, this point varying
with the resistance of the mains.
(3.) The combination as described of a voltmeter either indicating or recording,
reading the difference of potential between a point in a high resistance placed
across the mains of a supply system and a point on a standard resistance in
series with the mains at the same point as the high resistance and carrying the
total current in the mains.
The falls of potential over the high resistance which varies with the station
pressure and that over the standard resistance, which varies with the current
passing being electrically opposed to one another; the standard resistance being
made with a sliding contact to which one of the voltmeter leads is connected
in such a manner that the amount of the fall of potential produced by the current
passing in it acting on the voltmeter may be adjusted according to the resistance
of the main, so that the voltmeter indicates the voltage at the far end of the
main.
with a
(4.) The combination as described of voltmeter either indicating or recording
high resistance and standard resistance, the standard resistance being
made with a sliding contact carrying an index travelling over a scale either of
even divisions or of divisions representing ohmic resistances of the main.
(5.) The combination as described of two voltmeters either indicating or record-
ing having two distinct windings, working in conjunction with two high resis-
tances and three standard resistances the whole being connected up substantially
as described to indicate the voltage at distant feeding points on a three wire
system.
Dated this fith Tan
1000