A Compound Electrical Testing Switch.
Year: 1895

page_text: Date of Application, 27th Aug., 1895
Complete Specification Left, 27th May, 1896-Accepted, 25th July, 1896
A Compound Electrical Testing Switch.
I HOWARD DUDLEY NORMAN of 69 Brunswick Place Brighton in the County
of Sussex, England Electrical Engineer do hereby declare the nature of this
invention to be as follows:-
It consists as herein described of a compound electrical testing switch the object
of the said switch being to facilitate the making of tests known as inductive or
electrostatic capacity, insulation resistance, & earth readings the connections
necessary for which are made automatically by the lever C Figs. 1, 2, 3, 4 & 5 in
passing from left to right or vice-versa or in any direction dependant on the position
of the switch itself which may be placed vertically horizontally, inverted, or in
any position most convenient. Six figures are shewn with the following objects
Fig. 1 is a diagrammatical view of the connections of the switch.
Fig. 2 shews the relative positions of the contact pieces on both sides of the
switch also a general view of one proposed form of switch.
Fig. 3 shews diagrammatically another form of switch with a different method
of shunting which form however is only applicable to one particular value of
galvanometer resistance.
Fig. 4 shews contact lever in detail suitable for use with the form of switch
shewn in Fig. 1.
Fig. 5 shews contact lever in detail suitable for use with the form of switch
shewn by Fig. 3.
Fig. 6 shews a suggested form of switch with all contacts on one plate & the
plate put horizontally.
-To
Referring to Figs. 1, 2, 3, 4, 5 & 6 the action of the switch is as follows:-
take the constant of the galvanometer G Fig. 1 for insulation resistance proceed
as follows. A standard megohm is joined up between terminal A Fig. 1 & earth
& the lever C shewn in detail in Fig. 4 is moved into position 6, 7 or 8 etc.
according to the sensitiveness of the galvanometer & battery power employed.
Suppose for example that 7 is the contact selected as most suitable the path of the
current is as follows:-Starting from one pole of the battery B Fig. 1 it reaches
the strap D thence by the lever C to contact 7 on the galvanometer side of the
switch & to the point E on the resistance A. F now E A is ro00 part of the total
resistance A F so that in accordance with the laws governing the flow of currents
in divided circuits only 1000 part of the total current flowing goes down E F
& through the galvanometer G the remainder passing to point A by the
resistance R 2.
The resistance R 1 may be 10000 part of the total resistance A F.
The resistance R 2 may be robo part of the total resistance A F.
The resistance R 3 may be Tou part of the total resistance A F.
The resistance R 4 may be part of the total resistance A F or they may of
course be of any known value their shunting effect on the galvanometer being in
accordance with that value.
Returning now to the following of the current from point A it passes through
the standard megohm & then to earth & the other pole of the battery B, that is to
say supposing with the lever C in position 7 a deflection of 200 was obtained on
the galvanometer scale the constant of the galvanometer would be 200 x 1000
=200000 with that particular battery power through 1 megohm. To take the

page_text: constant of the galvanometer for capacity measurements a standard capacity is
joined up in place of the megohm between A Fig. 1 and earth the lever C being at
position 1 lever C is then moved into a position intermediate between 2 & 3 which
corresponds with the "insulate" position in an ordinary discharge key, lever C
moved into position 3 discharges condenser through galvanometer G shunted by any
or none (as is necessary) of the shunts R1 R2 R3 R4 which shunts are inserted by
means of two plugs connected by a flexible cord the said plugs fitting into holes
made for that purpose in the outside of all connection blocks 1 to 14 on the
galvanometer side of the switch.
In the event of a standard megohm not being at hand for taking the constant
for insulation resistance testing, the deflection through 10,000 ohms or other
convenient resistance from the cell B1 is noted the necessary shunt being inserted
as herein before stated. The E.M.F. or apparent number of cells in battery B (in
terms of the one cell B 1) is found by means of a condenser placed as in taking
capacity constants. The formula worked out from these data necessary for finding
the constant is so well known that it is not given here.
The constauts for insulation resistance & capacity having been taken lever C is
moved into position 1 & the cable or wire to be tested is connected to terminal A
the lever C is then manipulated as follows first to position 2 charging cable or
wire if plug H Fig. 1 is inserted (if capacity of cable or wire is not required the
plug H may be withdrawn if preferred but this is not necessary as at the end of
the insulation test if the capacity of the next cable or wire is not required lever C
is moved back to position 4 Fig. 1 only) lever C is then put to position 3
discharging the cable or wire through the galvanometer G shunted if necessary as
herein before described lever C is now put to position 5 which charges the cable
or wire from the cells B the galvanometer being cut out of circuit & automatically
short circuited by the connection I Figs. 1 & 2 & the contact piece J Fig. 4 the
lever is then moved in a right handed direction its travel being stopped when a
sufficiently large deflection is obtained on the galvanometer scale, the necessary
electrification readings are then taken & if no earth readings are required, the
lever C is put back to position 4 Fig. 1 which movement discounects the cable or
wire under test from the battery & puts it to earth, the cable is then rung off
& when the next cable or wire is ready connected to terminal A the lever C is
returned to position if capacity data are required & the same operation gone over
again; if however earth readings are required at the end of the electrification
period the lever C is put to either position 4 or 12 (whichever is most convenient)
in both of which the cable is disconnected from the battery & put to earth the
galvanometer being automatically cut out & short circuited as herein before
described, after the first rush of current due to cable discharge has taken place the
galvanometer is inserted shunted or not as is necessary by putting the lever C to
either position 3, 13 or 14-14 being ready connected to the "no shunt."
Fig. 1 represents diagrammatically the connections for a switch on a constant
damping shunt principle.
Fig. 2 represents diagrammatically the connections for a switch on an ordinary
shunting principle, in this form of the instrument the lever C Fig. 3 is somewhat
differently constructed to that shewn in Fig. 1 the details of its construction are
shewn in Fig. 5 in which the barrel A. of the lever is made of some insulating
substance such as ebonite or vulcanized fibre the two lever arms B & B1 being
pinned & screwed thereto the screw_heads C & C 1 forming trunuions in electrical
connection with the terminals D & D1 respectively these terminals are also shewn
in Fig. 3 by the letters D1 & D & to them are connected respectively the cable
megohm or condenser under test & one pole of the galvanometer G, the other pole
of the galvanometer G being connected to D.
In Figs. 2, 4, & 5 E is a small brass arm beat at right angles & moving over the
face of the ebonite arc A Fig. 2 on which may be engraved as shewn the values of
the various positions, the pap F Figs. 4 & 5 fitting into the semi circular holes G
Fig. 2 & facilitating the stopping of the lever at any exact point.

page_text: The switch may of course be made in many modified forms-for example the
switch lever handle might be placed as a continuation of the trunnions C & C 1
Figs. 4 & 5. The pap holes G Fig. 2 might be put on the inner surface of the
ebonite arc A Fig. 2 & the whole switch thus be made damp & dust proof by a
strap of ebonite screwed over the top & at the two sides of the said ebonite arcs,
or again the contacts might be put out straight on a flat ebonite base (somewhat
as indicated in the diagrammatical Figs. 1 & 3) the lever C Fig. 2 being replaced
by a contact piece sliding in guides between the said contacts.
Signed this 20th day of August 1895.
A Compound Electrical Testing Switen.
I HOWARD DUDLEY NORMAN Electrical Engineer of 69 Brunswick Place
Brighton in the County of Sussex England 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:—
It consists as herein described of a compound electrical testing switch the object
of the said switch being to facilitate the making of tests known as inductive or
electrostatic capacity, insulation resistance, and earth readings the connections
necessary for which are made automatically by the lever C. Figs. 1, 2, 3, 4 and 5
in passing from left to right or vice versa or in any direction dependent on the
position of the switch itself which may be placed vertically, horizontally, inverted
or in any position most convenient. Referring to the drawings left with the
Provisional Specification six figures are shewn with the following objects
Fig. 1. is a diagrammatical view of the connections of the switch,
Fig. 2. shews the relative position of the contact pieces on both sides of the
switch also a general view of one proposed form of switch.
Fig. 3. shews diagrammatically another form of switch with a different method
of shunting which form however is only applicable to one particular value of
galvanometer resistance.
Fig. 4. shews contact lever in detail suitable for use with the form of switch
shewn in Fig. 1.
Fig. 5. shews contact lever in detail suitable for use with the form of switch
shewn by Fig. 3.
Fig. 6. shews a suggested form of switch with all contacts on one plate and the
plate put horizontally.
Referring to Figs. 1, 2, 3, 4, 5 and 6 the action of the switch is as follows-to
take the constant of the galvanometer G. Fig. 1. for insulation resistance proceed
as follows: A standard megohm is joined up between terminal A. Fig. 1. and
earth and the lever C. shewn in detail in Fig. 4. is moved into position 6, 7,
or 8, etc., according to the sensitiveness of the galvanometer and battery power
employed. Suppose for example that 7 is the contact selected as most suitable
the path of the current is as follows: Starting from one pole of the battery B.
Fig. 1. it reaches the strap D. thence by the lever C. and contact 7 on the
galvanometer side of the switch and to the point E. on the resistance A F.
now E A. is Too part of the total resistance A F. so that in accordance with the
laws governing the flow of currents in divided circuits only Too part of the total
current flowing goes down E F. and through the galvanometer G. the remainder
passing to point A. by the resistance R 2. The resistance R 1. may be 10000 part
of the total resistance A F. The resistance R2. may be To part of the total
resistance A F. The resistance K 3. may be the part of the total resistance A F.
The resistance R 4. may be part of the total resistance A F., or they may of

page_text: =
course be of any known value their shunting effect on the galvanometer being in
accordance with that value. Returning now to the following of the current from
point A. it passes through the standard megohm and then to earth and the other
pole of the battery B. that is to say, supposing with the lever C. in position 7 a
deflection of 200 was obtained on the galvanometer scale the constant of the
galvanometer would be 200 x 1000 200000 with their particular battery power
through one megohm to take the constant of the galvanometer for capacity
measureinents a standard capacity is joined up in place of the megohm between A.
Fig. 1. and earth the lever C. being at position 1, lever C. moved to position 2.
charges standard capacity at A. from cell B. lever C. is then moved into a position
intermediate between 2 and 3 which corresponds with the "insulate" position in
an ordinary discharge key, lever C. moved into position 3 discharges condenser.
through galvanometer G. shunted by any or none (as is necessary) of the
shunts R1, R2, R3, R4 which shunts are inserted by means of a flexible cord
and two plugs, the said plugs fitting into holes made for that purpose in the outside
of each connection block 1 to 14 on the galvanometer side of the switch. In the
event of a standard megohm not being at hand for taking the constant for
insulation resistance testing the deflection through 10,000 ohms or other convenient
resistance from the cell B1 is noted the necessary shunt being inserted as herein-
before described. The E.M.F. or apparent number of cells in battery B. (in
terms of the one cell B 1) is found by means of a condenser placed as in taking
capacity constants; the formula worked out from these data, uecessary for
finding the constant is so well known that it is not given here. The constant for
insulation resistance and capacity having been taken lever C. is moved into
position and the cable or wire to be tested is connected to terininal A. the
lever C. is then manipulated as follows: First to position 2 charging cable or wire
if plug H Fig. 1. is inserted (if capacity of cable or wire is not required. the
plug H. may be withdrawn if preferred, but this is not necessary, as, at the end of
the insulation test if the capacity of the next cable or wire is not required lever C.
is moved back to position 4 Fig. 1. only). Lever C. is then put to position 3.
discharging the cable or wire through the galvanometer G. shunted if necessary
as hereinbefore described, lever C. is now put to position 5 which charges the
cable or wire from the cells B. the galvanometer being cut out of circuit and
automatically short circuited by the connection 1. Figs. 1 and 2 and the insulated
contact piece J. Fig. 4. the lever C. is then moved in a right handed direction its
travel being stopped when a sufficiently large deflection is obtained on the
galvanometer scale, the necessary electrification readings are then taken, and, if no
earth readings are required, the lever C. is put back to position 4. Fig. 1. which
movement disconnects the cable or wire under test from the battery and puts it to
earth. The cable is then rung off and when the next cable or wire is ready
connected to terminal A. the lever C. is returned to position 2. if capacity data are
required and the same operation gone over again. If however earth readings are
required at the end of the electrification period the lever C. is put to either
position 4 or 12 (whichever is most convenient) in both of which the cable is
disconnected from the battery and put to earth the galvanometer being auto-
matically cut out and short circuited as herein before described, after the first rush
of current due to cable discharge has taken place the galvanometer is inserted
shunted or not as is necessary by putting the lever C. to either position 3, 13,
or 14, 14 being ready connected to the "no shunt." Fig. 1. represents diagram-
matically the connections for a switch on a constant damping shunt principle.
Fig. 2. represents diagrammatically the connections for a switch on an ordinary
shunting principle, in this form of the instrument the lever C. Fig. 3. is somewhat
differently constructed to that shewn in Fig. 1. the details of its construction are
shewn in Fig. 5. in which the barrel A of the lever is made of some insulating
substance, such as ebonite or vulcanised fibre, the two lever arms B and B 1 being
pinned and screwed thereto, the screw heads C. and C 1. forming trunnions in
electrical connection with the terminals D and D 1 respectively, these terminals

page_text: are also shewn in Fig. 3. by the letters D1 and D. and to them are connected
respectively the cable megohm or condenser under test and one pole of the
galvanometer G. the other pole of the galvanometer G. being connected to D. In
Figs. 2, 4 and 5 E is a small brass arm bent at right angles and moving over the
face of the ebonite arc A. Fig. 2. on which may be engraved as shewn the values
of the various positions, the pap F. Figs. 4 and 5. fitting into the semi-circular
holes G. Fig. 2. and facilitating the stopping of this lever at any exact point.
The switch may of course be made in many modified forms, for example the switch
lever handle might be placed as a continuation of the trunnions C. and C1 Figs. 4.
and 5. The pap holes G. Fig. 2. might be put on the inner surface of the ebonite
arc A. Fig. 2. and the whole switch thus be made damp and dust proof by a strap
of ebonite screwed over the top and at the two sides of the said ebonite arc, or
again the contacts might be put out straight on a flat ebonite base (somewhat as
indicated in the diagrammatical Figs. 1 and 3.) the lever C. Fig. 2. being replaced
by a contact piece sliding in guides between the said contacts.
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
The method herein before described of taking by one movement of one lever or
contact piece the electrical tests known as insulation resistance, capacity tests, and.
earth readings.
Det 1000
H. D. NORMAN.