Note: Descriptions are shown in the official language in which they were submitted.
CA 02476443 2004-09-O1
TEST PLUG AND CABLE FOR A GLUCOSE MONITOR
$ACKGROUND QF THE INVENTION
1. Field of the Inygntion
This invention relates to methods and devices used for electrically connecting
medical glucose monitors to glucose sensor electrodes as well as for testing
the
operation of the glucose monitors, monitor cables and glucose sensors.
2. Dc~riDtion of the Related Art
Over the years, a variety of implantable electrochemical sensors have been
developed for detecting or quantifying specific agents or compositions in a
patient's
blood. For instance, glucose sensors are being developed for use in obtaining
an
indication of blood glucose levels in a diabetic patient. Such readings are
useful in
monitoring or adjusting a treatment regimen which typically includes the
regular
administration of insulin to the patient. Thus, blood glucose readings can
improve
medical therapies with semi-automated medication infusion pumps of the
external type,
as generally described in U.S. Patent Nos. 4,562,751; 4,678,408; and
4,685,903; or
automated implantable medication infi~sion pumps, as generally described in
U.S.
Patent No. 4,573,994.
Generally, small and flexible electrochemical sensors can be used to obtain
periodic readings over an extended period of time. In one forn~, flexible
subcutaneous
sensors are constructed in accordance with thin film mask techniques in which
an
elongatal sensor includes thin film conductive elements encased between
flexible
insulative layers of polyimide sheets or similar material. Such thin film
sensors
typically include a plurality of exposed electrodes at one end for
subcutaneous
CA 02476443 2004-09-O1
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placement with a user's interstitial fluid, blood, or the Idce, end a
corresponding
exposed plurality of conductive contacts at another end for convenient
external
electrical connection with a suitable monitoring device through a wire or
cable.
Typical thin film sensors are described in commonly assigned U.S. Patent Nos.
5,390,671; x,391,250; 5,482,473; and 5,586,553.
Thin film sensors generate very small electrical signals which can be read by
extcmal glucose monitors. These monitors can 1x portable, and can be attached
to the
patient, such as for example, on a belt clip. Applicant's clinical studies
have shown
that an electrical cable may be provided for the transmission of these small
signals from
the sensors to the glucose monitor. But given the environment in which these
cables
are used, special characteristics can be useful.
Thus a glucose monitoring system includes connectors between the cables,
leads, electrodes and monitors..
Although
a well designed system will have minimal operational problems, it is possible
that a
problem might arise with the integrity of the cables, sensor electrodes or
monitor
during their use. The system connectors or the cables may become loose or
bent,
resulting in a poor or open circuit. The sensor electrodes could degrade. The
glucose
monitor could become inoperative due to any number of causes. Thus, it is
desirable
to provide a system that is simple to use so that a patient can easily
identify any
operational problems with the system.
TAT , RYQF THE P~i.EFERRED EMBODIES
A glucose monitoring system test plug as well as an electric cable for
electrically connecting a glucose monitor to a glucose sensor set are
provided. In one
embodiment, the electric cable comprises a cable member, a first connector and
a
second connector. The cable member in turn comprises at least one insulated
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conductor, a conductive shielding layer disposed around the at least one
insulated
conductor; and an insulating layer disposed around the conductive shielding
layer.
In one aspect, the first connector comprises a housing having a first bore
which
is adapted to receive a sensor set cable fitting and a first conductive
contact disposed
within the first bore. The first conductive contact is electrically coupled to
the
insulated conductor and is adapted to be removably electrically coupled to a
sensor set
conductive contact. In one embodiment of the present invention, a key fitting
is
formed within the first bore and is adapted to mate with the glucose sensor
set in one
orientation. There is further provided a releasable coupler disposed on the
housing
which is adapted to releasably couple the housing with the glucose sensor set.
In another aspect, the second connector comprises a housing having a second
bore. The second connector is adapted to releasably couple the second
connector with
the glucose monitor. There is a second conductive contact disposed v~ithin the
second
bore which is electrically coupled to the insulated conductor. The second
conductive
contact also is adapted to be removably electrically coupled to a glucose
monitor
conductive contact.
In yet another aspect, the glucose monitoring system test plug is for use with
a
glucose monitor cable which is adapted to electrically couple to a glucose
monitor.
The test plug comprises a housing and a fitting affixed to the housing. The
fitting is
adapted to electrically couple the test plug to the glucose monitor cable. The
test plug
further comprises an electrical circuit which is adapted to provide a known
test signal
to the cable and the glucose monitor in order to test the operational
performance of the
glucose monitor and the glucose monitor cable when the test plug is coupled to
the
glucose monitor cable and when the glucose monitor cable is coupled to the
glucose
monitor.
In an alternative embodiment, the test plug is provided for use with a glucose
monitor. The test plug comprises a housing and a fitting affixed to the
housing. The
fitting is adapted to electrically couple the test plug to the glucose
monitor. The test
plug further comprises an electrical circuit which is adapted to provide a
test signal to
the glucose monitor to test the operational performance of the glucose monitor
when
the test plug is coupled to the glucose monitor.
CA 02476443 2004-09-O1
In yet another embodiment, the test plug can alternarively provide a
releasable
electrical connection with either the electrical cable or the glucose monitor.
BRIEF DESCRIPTIQN OF THE DRAWINGS
FIG. I is a perspective view of an electrical cable for a glucose monitor in
accordance with one embodiment of the inventions.
FIG. 2 is a perspective view of a glucose monitoring system using the cable of
FIG. 1.
FIG. 3 is an end plan view of a glucose monitor connector portion of the
glucose monitor cable of FIG. 1.
FIG. 4 is a perspective view illustrating the assembly of the glucose monitor
cable of FIG. 1 with an insertion set.
FIG. 5 is a front-end perspective view of a sensor set connector portion of
the
glucose monitor cable of FIG. 1.
FIG. 6 is a cross-sectional view of a cable member portion of the glucose
monitor cable of FIG. 1 as viewed along the lines 6-6 of FIG. 1.
FIG. 7 is a top perspective view of a glucose monitoring system test plug in
accordance with another embodiment of the present inventions.
FIG. 8 is a bottom perspective view of the glucose monitoring system test plug
of FIG. 7.
FIG. 9 is a bottom plan view of the glucose monitoring system test plug of
FIG. 7.
FIG. 10 is a schematic diagram of an electrical circuit used in the glucose
monitoring system test plug of FIG. 7.
DETAILED DESC~PTION OF THE PREFERRED EMBODIME1NTS
In the following description, reference is made to the accompanying drawings
which form a part hereof and which illustrate several embodiments of the
present
invention. It is understood that other embodiments may be utilized and
structural and
operational changes may be made without departing from the scope of the
present
invention.
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-S-
Refernng to FIG. 1 there is disclosed a shielded cable 10 constructed in
accordance with aspects of the present invention. The cable 10 includes a
flexible
cable member 13 with a monitor connector 11 at one end and a sensor connector
12 at
the opposite end. FIG. 2 illustrates the use of the cable 10 in an exemplary
glucose
monitoring system. The system includes a subcutaneous glucose sensor set 20
which is
coupled to a glucose monitor 21 by the cable 10. The subcutaneous glucose
sensor set
20 uses an electrode-type sensor, as described in more detail below. However,
in
other applications, the glucose sensor may use other types of sensors, such as
chemical
based, optical based or the like. The sensor shown in FIG. 2 is a surface
mounted
sensor that uses interstitial fluid harvested from the skin. Other sensors may
be of a
type that is used on the external surface of the skin or placed below the skin
layer of
the user.
The glucose monitor 21 of the illustrated embodiment generally includes the
capability to record and store data as it is received from the sensor set 20,
and includes
either a data port or a wireless transmitter for downloading the data to a
data
processor, computer, communication station, or the like for later analysis and
review.
The data processor or computer uses the recorded data from the glucose monitor
to
determine the blood glucose history. Thus, one purpose of the glucose monitor
system
is to provide for improved data recording and testing for various patient
conditions
using continuous or near continuous data recording.
The sensor set 20 of the illustrated embodiment is provided for subcutaneous
placement of a flexible sensor, or the like, at a selected site in the body of
the user.
The sensor set 20 includes a hollow, slotted insertion needle 22 and a cannula
(not
shown) inside the needle 22. The needle 22 is used to facilitate quick and
easy
subcutaneous placement of the cannula at the insertion site. The cannula
includes one
or more sensor electrodes (not shown) which are exposed to the user's bodily
fluids.
After insertion, the insertion needle 22 is typically withdrawn to leave the
cannula with
the sensor electrodes in place at the selected insertion site.
The sensor set 20 includes a mounting base 23 adapted for placement onto the
skin of a user. As shown, the mounting base 23 of the illustrated embodiment
is a
generally rectangular pad having an underside surface coated with a suitable
pressure
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sensitive adhesive layer, with a peel-offpaper strip 24 provided to cover and
protect
the adhesive layer, until the sensor set 20 is ready for use. Further
description of
suitable needles and sensor sets are found in U.S. Patent No. 5,586,553,
entitled
"Transeutaneous Sensor Insertion Set':
As shown in FTGs. 2 and 3, the glucose monitor 21 is coupled to the sensor set
20 by the cable 10 which electrically couples the monitor connector 11 to the
connector block 25 of the sensor set 20. The monitor connector 11 of the cable
10 is
connected to the glucose monitor 21 through a plug receptacle 26 of the
monitor 21.
The monitor connector 11 includes a plurality of pins 31 arranged in a pin
snap-in
configuration to connect to the receptacle 26 of the glucose monitor 21. In
this
embodiment, there arc four (4) pins 31, three (3) of which are used for
connection to 3
insulated conductors within the cable 10 and one of which is for a drain (or
ground)
conductor within the cable 14.
The glucose monitor 21 includes a housing 2? that supports at least one
printed
circuit board, batteries, memory storage, a display screen 28, the plug
receptacle 26,
and the cable 10 and the monitor connector 11 when connected to the plug
receptacle
26 of the monitor 21. The lower portion of the glucose monitor 21 may have an
underside surface that includes a belt clip, or the like, to attach to a
user's clothing.
Altenzatively, the underside surface may be coated with a suitable pressure
sensitive
adhesive layer, with a peehff paper strip normally provided to cover and
protect the
adhesive layer until the glucose monitor 21 is ready for use. Alternatively,
the glucose
monitor 21 may be secured to the body by other methods, such as an adhesive
overdressing, straps, belts, clips, or the like.
In other embodiments, the cable 10 may also have a flexible strain relief
portion, as indicated at reference numeral 14 of FIG. 1, to minimize strain on
the
sensor set 20 and minimize movement of the sensor set 20 relative to the body,
which
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can lead to discomfort or dislodging of the sensor set 20. The flexible strain
relief
portion is intended to also minimize sensor artifacts generated by user
movements that
causes the sensor set 20 to move laterally relative to the glucose monitor 21
by
reducing lateral movement of the sensor connector 12..
The glucose monitor 21 provides power or other signals, through the plug
receptacle 26 to the monitor connector 11 of the cable 10 and then through the
cable
to the sensor connector 12 of the sensor set 20. These signals are used to
drive the
sensor electrodes and to speed the initialization of the sensor set 20, when
first placed
on the skin.
10 FIGs. 4 and 5 illustrate a connection arrangement between the sensor
connector 12 portion of the cable 10 of the illustrated embodiment and the
sensor set
20. As shown, the sensor connector 12 has a low profile housing 40 for
comfortable
fitting against the body. The housing 40 is compact in size and can be
constructed
from lightweight molded plastic. The housing 40 defines a socket fitting 51
for mating
slide-fit engagement with a rear cable fitting 41 of a sensor set mounting
base 23. 'The
socket fitting 51 of the illustrated embodiment has a bore or cylindrical
entry portion
52 which leads to a generally D-shaped or half circle step portion 53
positioned within
the entry portion 52. The socket fitting 51 therefore fonns a "keyhole" type
fitting
which is sized to receive the D-shaped "key" portion of the sensor set fitting
41.
The socket fitting 51 includes a plurality of conductive contacts 54 (FIG. 5)
positioned on the step portion 53 for electrically coupled engagement with
correspondingly positioned contact pads of the cable fitting 4l , when the
sensor set 20
and the sensor connector 12 are coupled together. The conductive contacts 54
of the
illustrated embodiment have a leaf spring design to facilitate good electrical
and
mechanical contact to the sensor set fitting contact pads. When assembled,
seal rings
42 of the sensor set fitting 41 sealingly engage the entry portion 52 of the
socket fitting
S 1 to provide a water resistant connection between the components.
Furthermore, the
D-shaped geometry of the interfitting components 41 and 53 facilitate proper
conductive coupling of the cable 10 to the sensor set 20 in the desired
orientation.
The sensor set.20 and the sensor connector 12 are held together by releasable
couplers, which in the embodiment of FIGs. 4 and 5, include interengaging snap
fit
CA 02476443 2004-09-O1
_g_
Patch arms 44 of the sensor set 20 and latch recesses 55 of the connector 12
of the
cable 10. As shown, the insertion set mounting base 23 is formed to include
the pair of
rearwardly projecting cantilevered latch arms 44 which terminate at the
rearward ends
thereof in respective undercut latch tips 43. The latch arms 44 are
sufficiently and
naturally resilient to provide a living hinge for movement relative to the
remainder of
the mounting base 23 to permit the latch arms 44 to be squeezed inwardly
toward each
other.
The permissible range of motion accommodates snap fit engagement of the
latch tips 43 into a corresponding pair of latch recesses 55 formed in the
housing 40 of
the sensor connector 12 on opposite sides of the socket fitting 51, wherein
the latch
recesses 55 are lined with indentations which act as latch keepers 56 for
engaging the
latch tips 43. The components can be disengaged for uncoupling when desired by
manually squeezing the latch arms 44 inwardly toward each other for release
from the
latch keepers 56, while axially separating the mounting base 23 from the
sensor
connector 12.
For use as a connector between a sensor set and a glucose monitor, the cable
10 includes one or more insulated conductors, and in order to increase user
comfort,
should be relatively long and have good flexibility. However, the electrical
signals
from the sensor set 20 electrodes can be very small (i.e., in the range of 1
to 200 nano
amps) thus making the cable susceptible to external electrical noise. To
reduce this
susceptibility the cable is preferably shielded and relatively short. These
characteristics
would tend in general to make a cable less comfortable for a user.
A further source of electrical noise in cables is the triboelectric effect
which is
caused by the use of certain electrical insulators. Certain types of
insulators, such as
for example, Teflon, can be so effective that when the cable is bent, the
electrical
charge on the cable will separate but will not reform quickly. When the charge
belatedly reforms, this can appear as a voltage spike or noise on the cable.
Thus, while
an effective insulator is useful for glucose monitor cables, the insulator
preferably
should not permit unacceptable levels of triboelectric noise. Certain
insulation
materials may provide a good solution to the triboelectric effect. However,
many of
them would not result in as flexible a cable as is desired.
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FIG.6 shows a cross sectional view of an exemplary embodiment of the
flexible cable member 13 of the glucose monitor cable 10. This design strikes
a
satisfactory balance between cable flexibility, high insulation, and low noise
characteristics. The cable member 13 includes three (3) center conductors 61
as well
as a drain line 62. The center conductors 61 are electrically coupled to the
conductive
contacts 54 (FIG. S) of the sensor connector 12 at one end and are coupled to
3 of the
4 pins 31 of the monitor connector 1 I at the opposite end. (FIG. 3) The drain
line 62
is electrically coupled to the remaining one of the pins 31 of the monitor
connector 11
which is electrically grounded. In this embodiment, the center conductors 61
each are
constructed of 30 AWG 40 x 46 BC bunched stranded copper with a nominal OD of
.013 inches. It is believed that alternative constructions for the conductors
61 may
achieve acceptable flexibility if gauges of a number greater than 30 and
strand counts
greater than 40 are employed. The drain line 62 is constructed of 30 AWG
7x.004 TC
concentric stranded copper with a nominal OD of .012 inches. Other gauges,
strand
counts and OD's for the conductors 61 and the drain line 62 may be used,
however
depending upon the application.
The three conductors 61 are each surrounded by a first insulating jacket 63,
which in the illustrated embodiment is 8 mils nominal PVC insulation with a
nominal
OD of .026 inches. An alternative insulation material to PVC is believed to be
a
polyester material, such as Mil-eneTM which is available from W.L. Gore &
Associates
of Newark, Delaware. The drain line 62 of the illustrated embodiment is not
surrounded by a first insulating jackct.
The three conductors 61, their insulating jackets 63 and the drain line 62 are
collectively surrounded by a shield 64. The shield 64 is constructed of 44 AWG
tinned
copper braid with a nominal thickness of .007 inches. Other thicknesses and
gauges
may be used however, depending upon the particular application. The shield 64
serves
to prevent or minimize external electromagnetic interference fields from
affecting the
low level signals being transmitted on the conductors 61. The drain line 62 is
adjacent
to and therefore in electrical contact with the shield 64 throughout the
length of the
cable member 13. Because the drain line 62 is electrically coupled to the one
of the
pins 31 which is grounded, this serves to ground the shield 64. By grounding
the
CA 02476443 2004-09-O1
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shield 64 in this manner, a separate electrical termination of the shield to
any sort of
alternative grounding on the monitor connector 11 of the cable 10 may be
eliminated.
The shield 64 is surrounded by a second insulating jacket 65. The second
insulating jacket 65 of the illustrated embodiment is constructed of PVC (USP
class
VI) which is a "food grade" PVC and has a nominal thickness of .O1 D inch.
Alternative acceptable materials to PVC are believed to include thermoplastic
elastomcrs such as SantoprencTM which is available from Advanced Elastomers (a
division of Monsanto) of Akron, Ohio, or a reinforced elastomer based
material, Sil-
KoreTA', which is available from W.L. Gore & Associates of Newark, Delaware.
The
OD of the insulating jacket 65, and therefore of the cable 10, is
approximately .090
inches. Although the illustrated embodiment of the outer jacked 65 has a
nominal
thickness of .010 inches and an OD of .090 inches, it is believed that nominal
thicknesses of .006 inches or greater and OD's of .110 inches or less may be
employed
and achieve acceptable results.
When constructed in accordance with the previously-described embodiment, it
is believed that the cable 10 will have triboelectric noise characteristics of
no more than
approximately 50 to 150 micro volts per AAMI ECG 5183 test. This construction
results in a cable member 13 which strikes a satisfactory balance between
maximum
insulation and minimal triboelectric noise. Moreover, the cable 10 is small in
diameter
2D and relatively long and flexible, thus providing a greater degree of user
comfort.
However, these embodiments may also be used for shorter cables used to connect
various components in telemetered systems.
Referring now to FIG. 7, a test plug 70 is disclosed that can simulate the
glucose sensor electrodes, or the combination of the glucose sensor electrodes
and the
cable 10 of a glucose monitoring system. If an operating problem occurs while
the
glucose monitoring system is being used, the test plug 70 provides diagnostic
information that can help indicate if a glucose sensor, the cable or the
glucose monitor
is operating normally.
The test plug 70 includes two connectors. Each connector facilitates the
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testing of a different component of a glucose monitoring system. A monitor
connector
72 allows the device to plug into the glucose monitor 21 in place of the cable
10 so the
monitor can be checked independently from the rest of the system. A cable
fitting 73
allows the device to plug into the cable 10 in place of the sensor set 20 so
that the
operation of the cable 10 can also be verified.
As will be described in more detail below, the test plug 70 is a sensor
simulator
that, in one embodiment, can return a constant current of the same magnitude
as is
produced by the sensor electrodes during normal in-vivo operation. This
current is
measured by the monitor 21 and is reported on the display screen 28 of the
monitor 21.
(FIG. 2) From the display screen 28, the user can view the test current and
verify that
the monitor is reporting the con ect signal current with the expected
accuracy. This
can be accomplished when the test plug 70 is plugged directly into the monitor
or
when it is plugged into the distal end of the cable 10.
The ability to perform such simple performance checks in the field is expected
to offer users the opportunity to troubleshoot system problems with greater
ease and
confidence.
Referring to FIG. 10, the test plug simulates the presence of an actual sensor
electrode to produce a signal current that the monitor can measure. Monitor
connector pins 79 - 82 are disposed in the monitor connector ?2 portion of the
test
plug 70 (FIG.?) and are adapted for direct connection to the plug receptacle
26 of the
glucose monitor 21. (FIG. 2) In one embodiment, the simulator has an
electrical circuit
1003 that includes a first resistor 1001 connected between the monitor
connector pin
80 which simulates a reference electrode connection and the monitor connector
pin 79
which simulates a working electrode connection. The test current produced
depends
upon the voltage provided by the monitor 21 and the value of the resistor
between the
simulated reference and working electrode connections. In one embodiment, a
test
current of 27 nA is developed with a nominal monitor voltage of 535 mV where
the
first resistor 1001 is 20 million ohms.
A second resistor 1002 is placed between the monitor connector pin 81 which
simulates a counter electrode connection and the monitor connector pin 80. The
second resistor 1002 is chosen to be of equal value, or 20 million ohms, so
that the
CA 02476443 2004-09-O1
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voltage at the simulated counter electrode 81 will be twice that of the
monitor voltage
as measured between simulated electrodes 79 and 80. Choosing the second
resistor
value to produce a voltage twice that of the monitor voltage facilitates
verifying the
monitor voltage value. Monitor connector pin 82 simulates a connection to the
cable
drain line 62 (FIG. 6) and therefore is electrically isolated from the
resistors 1001 and
I 002.
Still referring to FIG. 10, a plurality of contact pads 75 are disposed in the
cable fitting 73 portion of the test plug 70 (FIG. 7) and are adapted for
electrical
connection to the sensor connector 12 of the cable 10. (FIG. 5) When connected
to the
cable 10, the test plug 70 continues to simulate the presence of an actual
sensor
electrode. However, it produces a signal current that travels through the
cable 10 to
the monitor for measurement.
The contact pads 75 are connected to the resistors 1001 and 1002 in the same
fashion as the monitor connector pins 79 - 81. Therefore, the manner in which
the test
IS current is generated through the contact pads 75 and through the cable 10
is the same
as was previously described.
It will be appreciated that although the electrical circuitry shown in FIG. 10
has
resistors arranged to produce a test current, many other circuitry
arrangements
comprised of other, known, electrical components, such as capacitors,
inductors,
semiconductor devices and voltage sources, can be incorporated in the test
plug 70 to
provide a suitable test current or other test signal.
Referring now to FIGs. 7-9, one embodiment of the test plug 70 of the present
invention is shown. The test plug 70 includes a housing 71 which encloses the
electrical circuitry, such as that shown in FIG. 10. At one end of the test
plug 70 is the
monitor connector fitting 72. At the opposite end is the cable fitting 73.
The cable fitting 73 is sized for mating slide-fit engagement with the socket
fitting 51 of the cable 10. (FIG. S) The cable fitting 73 connects to the
cable 10 in the
same manner as the glucose sensor set 20. Accordingly, the cable fitting 73 is
the
same as or similar to the sensor fitting 41 and likewise includes a D-shaped
fitting key
74 which is received by the cylindrical entry portion 52 of the socket fitting
51. (FIG.
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-13-
S) The generally D-shaped step portion S3 of the fitting S1 ieceives the D-
shaped
fitting key 74 of the cable fitting 73 portion of the test plug 70. (FIG. 7)
As shown,
the cable fitting 73 includes the plurality of conductive contact pads 7S
positioned on
the flat portion of the fitting key 74 (FIG. 8) for electrically coupled
engagement with
S the conductive contacts 54 (FIG. S) of the cable 10. The conductive pads 7S
are
further coupled to the resistors 1001 and 1002 shown in FIG. 10.
The cable fitting 73 includes positioning rings 76 situated around the tubular
portion of the cable fitting 73. Because the insertion set 20 includes seal
rings 42 for a
seal tight engagement with the socket fitting S 1 of the cable 10 (FIG. 4),
the
positioning rings 76 on the test plug 70 serve as a counterpart to the seal
rings 42 and
are used to properly center the cable fitting 73 in the socket fitting S 1.
The D-shaped
geometry of the inte~tting components ?4 and 53 insure proper orientation for
correct
conductive coupling of the cable 10 to the test plug 70. Although a D-shaped
geometry is shown in FIG. 4, other geometries, such as triangles, notches and
the like,
1 S can be employed to provide proper orientation.
Referring again to FIGs. S and 7, the test plug 70 and the sensor connector 12
portion of the cable 10 are retained in releasable coupled relation by
interengaging snap
fit latch members. As shown, the test plug housing 71 is formed to include a
pair of
rearwardly projecting cantilevered latch arms 77 which terminate at the
rearward ends
thereof in respective undercut latch tips 78. The latch arms 77 are
sufficiently and
naturally resilient for movement relative to the remainder of the housing 71
to permit
the latch arms 77 to be squeezed inwardly toward each other.
The permissible range of motion accommodates snap fit engagement of the
latch tips 78 into a corresponding pair of latch recesses SS formed in the
sensor
connector housing 40 on opposite sides of the socket fitting 51, wherein the
latch
recesses SS are lined with latch keepers S6 for engaging the latch tips 78.
With this
arrangement, the user is able to hear a clicking noise and feel the test plug
snap into
place. The components can be disengaged for uncoupling when desired by
manually
squeezing the latch arms 77 inwardly toward each other for release from the
latch
keepers 56, while axially separating the test plug 70 from the sensor
connector 12
portion of the cable 10.
CA 02476443 2004-09-O1
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The monitor connector 72 portion of the test plug 70'can be electrically
coupled directly to the glucose monitor 21 through the plug receptacle 26 of
the
monitor 21. (FIG. 2) The monitor connector 72 connects to the glucose monitor
21 in
the same manner as the cable 10. The monitor connector 72 has a plurality of
pins 79 -
82 for a snap-in configuration to the glucose monitor 21. (FIG. 9) In this
embodiment,
the pins 79 - 81 are used for connection to the test plug resistors 1001 and
1002 as
shown in FIG. 10.
Having described the structure of the test plug 70, it can be seen how the
test
plug 70 can be used to provide diagnostic information that can help indicate
if a
glucose sensor, the cable or the glucose monitor is operating normally.
Referring
generally to FIGs. 2 and 7, if the display 28 of the monitor 21 indicates that
there is a
malfunction, the sensor set 20 can be disconnected from the cable 10. The
sensor
connector 12 portion of the cable can then be connected to the cable fitting
73 portion
of the test plug 70. By pressing the appropriate buttons on the monitor 21,
the
monitor 21 can apply a test voltage through the cable 10 and the resistors
1001 and
1002 of the test plug 70 and measure the resulting current. The value of the
current
can be displayed on the monitor screen 28. If the value of the current falls
within an
acceptable range, then it is known that the monitor 21 and the cable 10 are
operating
properly. The operational problem therefore likely lies in the sensor set 20
which can
be replaced by the user.
On the other hand, if the measured current is outside of the acceptable range
of
values, then the problem may lie in either the cable 10 or the monitor 21 or
both. The
user then disconnects the cable 10 from the monitor 21 and from the test plug
70. The
monitor connector 72 portion of the test plug 70 rriay then be connected
directly to the
plug receptacle 26 of the monitor 21. Once again the appropriate buttons on
the
monitor 21 are pressed by the user to cause a test voltage to be applied from
the
monitor 21 directly to the test plug 70 thereby measuring the resulting
current. If the
value of the current as displayed on the monitor screen 28 falls within an
acceptable
range, then it may be deduced that the monitor 21 is likely operating properly
and that
the problem likely lies in the cable 10. The cable 10 can be replaced and the
system
tested with a new cable to verify proper operation. On the other hand if the
value of
CA 02476443 2004-09-O1
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the current falls outside the acceptable range, then the monitor 21 is likely
to have a
problem. If the user is unable to locate and correct the monitor 21 problem,
the
monitor can be sent to a repair facility.
Although shown for use with the cable 10 and the monitor 21, further
S embodiments of the test plug may be used in telemetered systems to test the
various
components,
While the description above refers to particular embodiments of the present
invention, it will be understood that many modifications may be made without
departing from the spirit thereof. The accompanying claims are intended to
cover such
modifications as would fall within the true scope and spirit of the present
invention.
'I"he presently disclosed embodiments are therefore to be considered in all
respects as
illustrative and not restrictive, the scope of the invention being indicated
by the
appended claims rather than the foregoing description, and all changes which
come
within the meaning and range of equivalency of the claims are therefore
intended to be
embraced therein.
