A Leakage Detector or Insulation Tester to be employed in the Testing of Electric Lighting Conductors and other Leads.
Year: 1891

page_text: Date of Application, 29th Apr., 1891
Complete Specification Left, 28th Jan., 1892-Accepted, 5th Mar., 1892
PROVISIONAL SPECIFICATION.
A Leakage Detector or Insulation Tester to be employed in the
Testing of Electric Lighting Conductors and other Leads.
I, Sir DAVID LIONEL SALOMONS, Bart., of 49 Grosvenor Street, London, do
hereby declare the nature of this invention to be as follows :-
This invention has for its object a leakage detector to be employed in the testing
of electric lighting conductors and other leads.
The instrument is arranged to indicate the leakage by means of graduations upon
a dial so that no skill on the part of the observer is needed.
The instrument consists of coils of insulated wire of suitable resistance. Within
the coils a magnetic needle is mounted upon an axis. There is a pointer upon the
axis which when the needle is deflected moves over the face of a dial. The scale is
graduated to give the resistance of a leak in Ohms; the divisions are numbered
from 1 to 100 and each unit signifies 10,000 Ohms. A key is provided it rocks
on an axis, and beneath the key are two contact studs, one connected with the
positive lead and the other with the negative lead, the key is placed in communi-
cation with one or the other of the leads according as one or other of its ends is
pressed down. The key is also connected with one end of the wire forming the
coils and the other end is connected to earth through a safety fuse wire.
When the key is put down in either direction it earths one of the leads through
the coils and the current passing, (which is dependent on the insulation of the other
lead) deflects the needle and the resistance of the leak or value of insulation
resistance is read off.
The key then has only to be reversed and the leakage of the other lead is similarly
indicated and may be read off from the instrument.
When the needle has to be protected against magnetic and other outside influences,
then a wrought iron case or covering should be used.
In both instruments the pointer is brought to the zero either by gravity or some
other directing force so arranged as to operate more and more powerfully as the
pointer recedes from the zero.
Dated this 29th day of April 1891.
CARPMAEL & CO.,
A cents.
COMPLETE SPECIFICATION.
A Leakage Detector or Insulation Tester to be employed in the
Testing of Electric Lighting Conductors and other Leads.
I, Sir DAVID LIONEL SALOMONS, Bart., of Broomhill Tunbridge Wells in
the County of Kent, 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 :-
This invention has for its object a leakage detector or insulation tester to be
employed in the testing of electric lighting conductors and other leads.
The instrument is so arranged that by the depression of a double acting key one
or other of the leads can be connected through galvanometer coils to earth.
Any leakage to earth which then occurs from the other main is represented by a
current passing in the galvanometer coils.
This current deflects the galvanometer needle and it then indicates upon a scale.
The dial is so graduated that the resistance of the insulation can be directly read
from it and is so ascertained without need for skill on the part of the operator.

page_text: The instrument is also preferably so arranged as to indicate if the proper or
standard voltage is maintained and if not what is the amount of the deficiency or
excess. This is done by providing a switch and resistance coils. The arrangement
is such that by turning the switch and afterwards pressing the key, the two mains
connected through the resistance coils and the galvanometer coils and the
needle is deflected more or less and in accordance with the voltage. The index
needle then points out the voltage marked upon the graduated dial.
In order that my said invention may be fully understood and readily carried into
effect I will proceed to describe the drawings hereunto annexed.
needle is deflected more or less and in accordance with the voltage. The index
needle then points out the voltage marked upon the graduated dial.
In order that my said invention may be fully understood and readily carried into
effect I will proceed to describe the drawings hereunto annexed.
DESCRIPTION OF THE DRAWINGS.
Figure 1 is an elevation of an instrument in accordance with my invention.
Figure 2 shows the same with the case or cover and also the dial removed.
Figure 3 is an elevation of the case or cover.
Figure 4 is a section on the line 4, 4, in Figure 2.
Figure 5 is an elevation partly in section of a portion of the switch.
Figure 6 shows separately the barrel of the switch.
Figure 7 shows separately one of the contact springs of the switch.
Figure 8 is a diagram showing the electrical connections of the parts.
a is the reel of the galvanometer on which the coils are wound, it is of oval form
and within it is a magnetised needle or bar mounted upon an horizontal axis which
also carries the index b and a weight b. This weight 6' when no current passes in
the coils wound upon the reel a makes the needle and index to stand vertically, and
when the needle is deflected the weight resists the deflecting force more and more
as the inclination of the needle increases.
This
c is the dial of the galvanometer, it has two arcs of graduations upon it. The
are marked T is used in testing the insulation resistance and it is so graduated that
the current which the standard electro motive force (say 100 volts.) produces
through a resistance of 10,000 Ohms deflecting the index 6 to the graduation mark 1,
whilst such a current as the standard electro motive force produces through
20,000 Ohms deflects the index needle to the graduation mark 2 and so on.
is the meaning of the indication upon the dial "1=10,000 Ohms." The arc of
graduations marked V is used in testing voltage; the mark 100 is placed where the
index stands when the two electric leads to which the instrument is applied are
connected through the galvanometer coils and the resistance coils with which the
instrument is provided. Similarly the mark 75 is placed where under like circum-
stances the index stands when the voltage is 75, and so on. d is the double acting
key; it is a metal bar, capable of rocking on a central pivot or axis d' carried by
the fulcrum e. Two springs el el support the bar d in the position shown in
Figure 4. The bar d is provided with finger buttons d d and with platinum
contact pins d³ d³. By pressing on one or other of the finger buttons d' the corre-
sponding pin d³ is brought against a platinum contact upon a metal support fixed
upon the base of the instrument; these supports are marked f' and f g g are
reels upon which the resistance coils are wound. is the barrel of the switch; it
is of vulcanite and a screw ' which is pinned into it serves to connect it with the
base of the instrument as is shown in Figure 5. 2 is a pin inserted into the barrel h
and serving to limit the angle through which it can be turned by coming against
one or other of the stops ii. The drawings show the barrel h in an intermediate
A³ is a
position to which it may be placed when the instrument is out of use.
metal contact plate fixed upon the barrel h. k¹ k³ ³ k are four springs tipped
with platinum which bear upon the contact plate h³ in certain positions of the
barrel h.
In Figure 8 and 18 are the electric leads, the one positive, the other negative.
is connected with f1 and 12 with f'; clamping screws upon ff as the drawings
show, serve to hold the connecting wires. The fulcrum e of the key bar d is con-
nected with one end of the galvanometer coils and the other end of these coils is

page_text: connected with the coupling plate m¹. The plate m¹ is connected with the corre-
sponding plate m² by a safety fuse n consisting of a short length of fine wire such
as would be immediately fused and destroyed by a current such as otherwise might
injure the instrument. Under the ordinary conditions of working the fuse wire
simply serves to continue the circuit from m' to m². m² is connected with the
contact spring k². When the instrument is employed in testing the switch is placed
with the arrow head upon it pointing to the letter T marked on the casing of the
instrument and then the plate ³ on the barrel of the switch serves to connect 2
with k¹. kis permanently connected to earth. Thus when the key is pressed,
whether one way or the other, the current flows from the one electric lead, through
the key bar, the galvanometer coils, the fuse, the plate ³ and so to earth and from
earth to the other electric lead by the leakage through its insulation, whatever this
may amount to; the amount then is indicated in Ohms by the index of the galvano-
meter pointing to the graduation on the dial. The connections of additional parts
of the instrument required for proving the voltage are as follows: -f1 is also
connected with k* and k² and k³ are connected by the resistance coils, 9. To prove
voltage the barrel of the switch is turned so that the arrow head marked upon it
points to the letter V upon the case of the instrument. The contact plate ³ then
connects 3 and k. When the key is pressed so as to make contact with the
support a current passes from the lead through the key, the galvanometer coils,
the fuse, the resistance coils, the plate and thence to the support f' and to the
lead. The strength of this current will depend on the voltage and the index
being more or less deflected by the current will be brought to point to the graduation
upon the dial against which the voltage which gives rise to the current is marked
in figures. It will then at once be seen if this voltage be the standard amount or in
what degree it deviates from it.
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. A leakage detector or insulation tester having galvanometer coils and needle
directed by gravity or other equivalent directing force, and also a key by which
communication may be established between earth and one or other of a pair of
electric leads whereby a current corresponding to the leakage is caused to traverse
the galvanometer coils and the needle of the galvanometer to be deflected until an
index in connection with it points out upon a dial the amount of the leakage.
2. A leakage detector or insulation tester in accordance with the preceding claim
and also provided with a switch and resistance coils so arranged that the instrument
serves also to prove the voltage.
3. In a leakage detector or insulation tester, such as described a rocking lever
key making contacts by its opposite extremities to connect with the electric leads
whereby it is rendered impossible to short circuit the leads which might cause
accident or damage.
4. A leakage detector or insulation tester substantially as described and
represented by the annexed drawings and with or without appliances for proving
the voltage.
Dated this 22nd day of January 1892
CARPMAEL & Co.,
Agents for the Applicant.