April 19. 1960
,
B. c. ADAMS
2,933,680
DYNAMIC SHORT LOCATOR
Filed “a315, 1958
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United States Patent O?ice
1
2,933,680
Fn'tented Apr. 19, 1960
2
tion of circuits as set forth in the paragraph immediately
above with a double pole single throw switch interposed
in series with said second indicator, with a third current
conduction indicator, with a current limiting resistor,
said third indicator and current limiting resistor being con
nected in series from the center terminal of said switch
2,933,680
DYNAMIC SHORT LOCATOR
Bertram C. Adams, Harwich Port, Mass.
Application May 15, 1958, Serial No. 735,578
5 Claims. (Cl. 324—51)
across the second indicator, with one of said test termi
nals connected to the center terminal of said switch, and
with the other test terminal connected to that terminal of
10 said second indicator not connected to said switch, such
that, when the test terminals are connected across a line
to be tested while said switch is open, the third indicator
will indicate whether the line is conducting a current,
and such that, when said switch is closed, the device will
This invention relates to the location of short circuits 15 function substantially as set forth in the paragraph imme
in electrical circuits.
diately above.
’
Objects of the invention are to provide a device use
For the purpose of illustration typical embodiments of
ful in determining the precise location of shorts in a
the invention are illustrated in the accompanying draw
low resistance electrical circuit which will function with
ing in which Figs. 1-5 are schematic diagrams of di?erent
speed, accuracy and a minimum of physical dislocation 20 embodiments of the apparatus. Fig. 6 graphically illus
of circuit wiring, which is una?ected by high resistances
trates current flow in the current conduction-indicators
which may be interposed in the line to be tested, and
of the various embodiments during testing.
'
which will not cease indication as the short is approached.
Fig. l is a schematic diagram of one embodimentv of
According to the present invention the device comprises
the invention in which E1 and E2 are batteries of sub
two sources of substantially equal voltage having one 25 stantially equal voltage having their negative poles inter
like pole of each source interconnected, a current-con
connected. An incandescent lamp L1 and a dropping re
duction indicator connected across the other poles‘ of said
sistor R1 are connected in series across the positive poles
sources, and two test terminals connected one to each
of the batteries. One test terminal T1 is connected to
pole of one source, so that, when the test terminals are
the resistor side of the lamp, and ‘another test terminal
connected across a line having a relatively high resistance, 30 T2 is connected to a negative pole of one source battery."
said sources oppose current ?ow through the indicator,
and such that, when resistance in the line across said test
When the test terminals are connected across a line to
terminals is successively lowered, reduced opposition to
lamp unless a short is present in the line; then,‘if a short
be tested, the sources oppose current ?ow through the
current ?ow causes the indicator to give an increasingly
is present, the opposition to current ?ow in the lamp will
dynamic indication. In more speci?c aspect, said indi 35 reduce proportionately to the resistance in the shorted
cator is connected in series with a dropping resistor across
line. Thus as the test points are brought nearer the lo
said poles of the sources and said test terminals are con
nected one to one source at a pole opposite said resistor
and one to the resistor side of said indicator so that, when
resistance in the line to be tested is varied over a rela 40
tively low resistance range, opposition'to current flow
through the indicator will continue to reduce giving a
satisfactorily dynamic reading in the indicator.
cation of the short the lamp glows more brightly. In
this embodiment, a lamp is used as the current-conduc
tion indicator but a buzzer or a meter would serve, the
lamp being preferred because of its low cost.
Fig. 2 is a schematic ‘diagram of. another embodiment
of the invention in which a battery E2, a switch S1 and
a lamp L2 are connected in a closed series circuit; ' Test ‘
In another aspect the invention comprises a current?
terminals T1 and T2 are connected to either side of the
conduction indicator, two test'terminals connected one to 45 lamp. When the test terminals are connected across a
each terminal of said indicator, a source of voltage con
line to be tested while the switch is closed, all battery
nected across the terminals of said indicator, such that,
current ?ows through the lamp unless a short is present
in the line; then, if a short is present current will be
ing relatively high resistance, high current will pass
shunted across the lamp proportionately to the resistance
through said indicator, and such that, when resistance in 50 in the shorted line. Thus as the test points are brought
the line across said test terminals is successively lowered,
nearer the location of'the short the lamp glows less
increased shunting of the indicator causes the indicator
brightly.
'
to give a decreasingly dynamic indication.
Fig. 3 is a schematic diagram ‘of the invention in which
In another aspect the invention combines the above
the elements of Fig.1 and Fig. 2 are combined. ‘When
mentioned circuits so that the device comprises two 55 the test terminals T1 and T2 are connected across a
sources of substantially equal voltage having one like
line to be tested, the sources oppose current flow through‘
pole of each source interconnected, a current-conduction
lamp L1 and force current to ?ow through lamp L2. If
indicator connected across the other poles of said sources,
a short is present in‘ the line, opposition to current ?ow
a second current-conduction indicator connected across
through lamp L1 and shunting of current flow across
60
the poles of one source, and two test terminals connected
lamp L2 will vary proportionately to the resistance in‘
one to each terminal of said second indicator, such that,
said line. Thus as the test points are brought nearer
when the test terminals are connected across a line hav
the location of the short, lamp Ll glows more brightly
ing relatively high resistance, said sources oppose cur
and lamp L2 glows'less brightly.
rent ?ow through the ?rst indicator and allow current to
Fig. 4 is a schematic diagram of one embodiment of
flow freely through the second indicator, and such that, 65 the invention similar to that shown in Fig. 3 but withv
when resistance in the line across said test terminals is suc
switch S1 replaced by a double pole single throw switch:
cessively lowered, reduced opposition to current ?ow
S2. A third lamp L3 and a current limiting resistor R2
causes the ?rst indicator to give an increasingly dynamic
are connected in series from the center terminal of S2
indication and increased shunting of the second indicator
across lamp L2. One test terminal T2 is connected to"
causes the second indicator to give a decreasingly dynamic. 70 the center terminal of the switch. When the test termi
when the test terminals are connected across a line hav
indication.
.
In another aspect the invention comprises a combina
nals are connectcd'across a line to'be tested while the‘
switch is open, lamp L3 will warn the operator whether a
____—i
2,933,680
3
current is'being conducted in the line. When said cur
rent in the line is interrupted, the switch may be closed
‘to test for and locate a short substantially as in the em->
bodiment set forth in Fig. 3.
Fig. 5 is a schematic diagram of one embodiment
similar to that shown in Fig. 2 but with switch S1 replaced
by a double pole single throw switch S2. A second lamp
L3 and a current limiting resistor R2 are connected in
series from the center terminal of switch S2 across lamp
L2. One test terminal is'connected to the center termi
4
successively lowered, reduced opposition to current flow
causes the indicator to give an increasingly dynamic in
dication.
2. A short circuit locating device comprising two
sources of substantially equalv voitage having one like
pole of each source interconnected, a current-conduction
indicator, a dropping resistor, said indicator and resistor
being connected in series across the other poles of said
sources, a test terminal connected to the resistor side of
said indicator, and a test terminal connected to one source
nal of the switch. When the switch is open, the operator
at a pole opposite said resistor, such that, when the test
minals, which is to be tested for current ?ow. Thus, in
the embodiment of Fig. 1, there is a minimum of resist
sources ofsubstantially equal voltage having one like pole
terminals are connected across a line having relatively
may test for a current being conducted in the line to be
high resistance, said sources oppose current ?ow through
tested, or, when the switch is closed, may test for and
said indicator, and such that, when resistance in the line
locate a short as in the embodiment set forth in Fig.2.
This short locator is characterized by the small amount 15 across said test terminals'is successively lowered, reduced
opposition to current ?ow causes the indicator to give an
of'resistance contributed by the instrument to that por
increasingly dynamic indication.
tion of the shorted circuit, connected across the test ter
3. A short circuit locating device comprising two
of each source interconnected, a current-conduction indi
ance contributed by the instrument to that portion of the
cator connected across the other poles of said sources, a
shorted circuit between points B and C. Likewise, in the
second current-conduction indicator connected across the
Fig. 2 embodiment, there is minimal resistance contributed
poles of one source, and two test terminals connected one
by the instrument to that portion of the shorted circuit
to
each terminal of said second indicator, such that, when
between points B’ and C’. Thus, when the operator draws
near the precise location of the short, where change in 25 the test terminals are connected across a line having
relatively high resistance, said sources oppose current
position of the test terminals will only slightly reduce
flow through the ?rst indicator and allow current to ?ow
line resistance, the change in line resistance as the test
freely through the second indicator, and such that, when
terminals are moved will be signi?cant relative to the
resistance in the line across said test terminals is succes
instrument resistance, thereby causing a change in 'cur-'
sively lowered, reduced opposition to current ?ow causes
rent-conduction indication suf?ciently dynamic to’ be read
the ?rst indicator to give an increasingly dynamic indica
with ease and clarity. This means that the operator can
tion and increased shunting-of the second indicator causes
more precisely locate a short before he must resort to
the second indicator to give a decreasingly dynamic
visual inspection of the shorted wires. This results in a
indication.
.
saving of time and reduces the possibility that the shorted
4. A short circuit locating device comprising two
wires will be parted and the location of the defect there 35
sources of substantially equal voltage having one like
by lost during visual inspection.
7
pole
of each source interconnected, a current-conduction
The embodiment illustrated in Fig. 1 will continue to
indicator, a dropping resistor, said’ indicator and resistor
give readable indication until the test terminals are con
nected directly’ across the short but this embodiment has 40 being connected in series across the other poles of said
sources, a second current-conduction indicator-connected
ashorter range than the embodiment illustrated in Fig. 2.
between the resistor side of the ?rst indicator and one
That .is, the Fig. 2 embodiment will indicate the presence
source at a pole opposite said resistor, and two test ter
ofa short in the line while the test terminals are still quite
minals connected one to each side of said second indicator,
remote from the short location. Howeverfthe Fig. 2
such that, when the test terminals are connected across
embodiment ceases indication at a greater, distance from I. '
a line having relatively high resistance, said sources
45
the precise short location. Therefore the combination
oppose current flow through the ?rst indicator and allow
of these embodiments as illustrated in Fig. 3 is practical
current to ?ow freely through the second indicator, and
'combiningthe best features of each”, This is illustrated
such that, when resistance in the line across said test
in the graph of Fig. 6 in which current intensity R in the
terminals
is successively lowered, reduced opposition to
current ?ow indicators L1 and L2 is laid along the graph
current flow causes the ?rst indicator to give an increasing
ordinate. The distance D along the line to be tested be
ly dynamic indication and increased shunting of the
tween the test point and the, point of short is laid along
second indicator causes the second indicator to give a
the graph abscissa. N, indicating the‘ current intensity in
decreasingly
dynamic indication.
L1, illustrates that L1 gives a very dynamic indication in
5. A short circuit locating device comprising two
the region'close to the short but that this indicator has a
short range. .M, indicating the current intensity in L2, 55 sources of substantially equal voltage having one like
pole of each source interconnected, a current-conduction
illustrates that L2 will not precisely locate the point of
indicator, a dropping resistor,.said indicator and resistor
short but that L2 will indicate the general location of the
being connected in series across the other poles of said
short from a test point relatively remote from the short.
sources, a second current-conduction indicator, a double
Figs. 4 and 5 incorporate awarning circuit to be used
alternatively to indicate whether the line to be tested is 60 pole single throw switch, said second indicator and switch
being connected in series between the dropping resistor
carrying a current which might injure the instrument.
side of the ?rst indicator and one source at a ‘pole oppo
It should be understood that the present disclosure is
site the dropping resistor, a third current-conduction indi
for the purpose of illustration only and that this inven
cator, a current limiting resistor, said third indicator and
tionincludes all modi?cations and equivalents which fall
current limiting resistor being connected in series from the
within the. scope of- the appended claims.
'
center terminal of said switch across said second indicator,
‘I claim:
~
a test terminal connected to the center terminal ‘of the'
I. A short circuit locating device comprisingv two
switch, and a test terminal connected to that terminal of
‘sources of‘ substantially equal voltage having one like
said second indicator not connected to said'switch, such
pole; ofeach source interconnected, a current-conduction
indicator connected across the other poles of said sources, 70 that, when the test terminals are connected across a‘line
to be tested while said switch is open, the thirdindicator
and twotest terminals connected one to each pole of one
will indicate whether the line is conducting a‘current,
source such that, when the test terminals are connected
such that, when the test terminals are connected across a
across'a line having relatively high resistance, said sources
line having relatively high resistance while said switch is
oppose current ?ow through the indicator; and such that,
whengresistance in ‘the line across said test terminals is 75 closed, said sources oppose current ?ow through the-?rst
2,988,680
indicator and allow current to flow freely through the
second indicator, and such that, when resistance in the
line across said test terminals is successively lowered,
References Cited in the ?le of this patent
UNITED STATES PATENTS
reduced opposition to current ?ow causes the ?rst indi
cater to give an increasingly dynamic indication and in
creased shunt'mg of the second indicator causes the sec
ond indicator to give a decreasingly dynamic indication.
5
1,560,278
2,383,557
2,469,703
Mahan ______________ __ Nov. 3, 1925‘
McClellan et a1 ________ _.. Aug. 28, 1945
Simkins _____________ .._ May 10, 1949