HK1119236B - System and method for coding information on a biosensor test strip - Google Patents

Description

System and method for encoding information on a biosensor test strip

Reference to related applications

This application is related to U.S. patent application No.10/871,937 (attorney docket No. WP-19085-US 3/7404-. This application is also related to U.S. provisional patent application No.60/480,397 (attorney docket No. WP-22038-US/7404-534), filed on 20/6/2003, and 60/581,002 (attorney docket No. WP-22634-US/7404-456), filed on 18/6/2004, the contents of both of which are hereby incorporated by reference in their entirety.

Technical Field

The present invention relates to a device for measuring the concentration of an analyte in a biological fluid. The present invention more particularly relates to systems and methods for encoding information on a biosensor test strip.

Background

Measuring the concentration of substances in biological fluids is an important tool for diagnosing and treating many medical conditions. For example, the measurement of glucose in body fluids such as blood is extremely important for the effective treatment of diabetes.

Therapy for diabetes generally involves two types of insulin treatment: basal, and meal time. Basal insulin refers to continuous, e.g., time-released insulin, often taken before sleep. Prandial insulin therapy provides additional doses of faster acting insulin to regulate fluctuations in blood glucose caused by various factors including the metabolism of sugars and carbohydrates. Proper regulation of blood glucose excursions requires accurate measurement of the concentration of glucose in the blood. The inability to accurately measure the concentration of glucose in the blood can produce serious complications, including blindness and loss of terminal circulation, which can ultimately result in the diabetic losing the ability to use his or her fingers, hands, feet, etc.

Various methods are known for determining the concentration of an analyte, such as e.g. glucose, in a blood sample. Such methods generally fall into one of two categories: optical methods and electrochemical methods. Optical methods typically involve spectroscopy to observe the spectral shift within the fluid caused by the concentration of the analyte, usually in conjunction with a reactant that produces a known color when combined with the analyte. Electrochemical methods typically rely on a correlation between current (amperometry), potential (potentiometry), or accumulated charge (coulometry) and analyte concentration, usually in conjunction with a reactant that generates charge carriers when combined with the analyte. See, for example, U.S. Pat. No.4,233,029 to Columbus, 4,225,410 to Pace, 4,323,536 to Columbus, 4,008,448 to Muggli, 4,654,197 to Lilja et al, 5,108,564 to Szuminsky et al, 5,120,420 to Nankai et al, 5,128,015 to Szuminsky et al, 5,243,516 to White, 5,437,999 to Diebold et al, 5,288,636 to Pollmann et al, 5,628,890 to Carter et al, 5,682,884 to Hill et al, 5,727,548 to Hill et al, 5,997,817 to Crismore et al, 6,004,441 to Fujiwara et al, 4,919,770 to Priedel et al, and 6,054,039 to Shieh, the disclosures of which are hereby incorporated by reference in their entirety. Biosensors used to perform assays are typically disposable test strips having a reagent thereon that chemically reacts with an analyte of interest in a biological fluid. The test strip is mated to a non-disposable test meter such that the test meter can measure the reaction between the analyte and the reagent to determine and display the concentration of the analyte to the user.

In such test meter/test strip systems, it is common practice to ensure proper identification of the test strip in order to ensure proper test results. For example, a single test meter may be capable of analyzing several different types of test strips, wherein each type of test strip is designed to test for the presence of a different analyte within the biological fluid. In order for the test to be performed properly, the test meter must know which type of test is to be performed on the test strip currently in use.

Moreover, batch-to-batch variations within test strips typically require calibration information to be loaded into the test meter in order to ensure accurate test results. A common practice for downloading such calibration information into the test meter is to use an electronic read-only memory key (ROM key) that is inserted into the socket of the test meter. Because this calibration data may only be accurate for a particular production lot of test strips, the user typically needs to confirm that the lot number of the test strip currently in use matches the lot number for which the ROM key was programmed.

Many other situations are known to those of ordinary skill in the art in which it is desirable to have information associated with a test strip. Prior art attempts to encode information on a test strip for reading by a test meter have encountered a number of problems, including the amount of information that can be encoded being severely limited and the use of a relatively large amount of test strip area for the information encoding function.

Thus, there is a need for systems and methods that allow information to be encoded onto a biosensor for reading by a test meter. The present invention aims to meet this need.

Disclosure of Invention

The present invention provides a test strip for measuring the concentration of an analyte of interest in a biological fluid, wherein the test strip may be encoded with information that can be read by a test meter into which the test strip is inserted.

In one form of the present invention, a system for measuring a concentration of an analyte of interest within a biological fluid is disclosed. The system includes an inspection meter and a first inspection strip having a first mask configuration, a first resistive element, and a second resistive element. The first mask configuration includes: a first measuring electrode connectable to a test meter; a first trace loop having a first associated resistance and a first gap, wherein the first trace loop is connectable to a test meter; and a second trace loop having a second associated resistance and a second gap, wherein the second trace loop is connectable to the test meter. A first resistive element is conductively connected to the first trace loop and bridges the first gap, and a second resistive element is conductively connected to the second trace loop and bridges the second gap. The system also includes a second test strip having a second mask configuration, a third resistive element, and a fourth resistive element, wherein the second mask configuration is substantially similar to the first mask configuration. The second mask configuration includes: a second measuring electrode connectable to the test meter; a third trace loop having a third associated resistance and a third gap, wherein the trace loop is connectable to a test meter; and a fourth trace loop having a fourth associated resistance and a fourth gap, wherein the fourth trace loop is connectable to the test meter. A third resistive element is conductively connected to the third trace loop and bridges the third gap, and a fourth resistive element is conductively connected to the fourth trace loop and bridges the fourth gap. The test meter is adapted to receive first and second test strips, connect to the first and second measurement electrodes, and connect to the first and second trace loops. The test meter is further adapted to obtain a first resistance ratio by comparing the first and second associated resistances, to connect to the third and fourth trace loops, and to obtain a second resistance ratio by comparing the third and fourth associated resistances. The test meter may be further adapted such that each of the first and second resistance ratios is associated with one or more predetermined values corresponding to information about the first and/or second strip.

In another form of the invention, a system for measuring a concentration of an analyte of interest in a biological fluid is disclosed. The system includes a test meter and a first test strip. The first test strip includes: a first measuring electrode connectable to a test meter; a first trace loop having a first associated resistance, wherein the first trace loop is connectable to a test meter; and a second trace loop having a second associated resistance, wherein the second trace loop is connectable to the test meter. The test meter is adapted to: receiving a first test strip; a first trace loop connected to the first measurement electrode, the first trace loop, and the second trace loop; and obtaining a first resistance ratio by comparing the first and second associated resistances.

In another form of the invention, a method for measuring the concentration of an analyte of interest in a biological fluid is disclosed. The method includes providing a test meter and providing a first test strip. The first test strip includes: a first measuring electrode connectable to a test meter; a first trace loop having a first associated resistance, wherein the first trace loop is connectable to a test meter; and a second trace loop having a second associated resistance, wherein the second trace loop is connectable to the test meter. The method further comprises the following steps: receiving a first test strip in a test meter; communicatively connecting the first measurement electrode, the first trace loop, and the second trace loop with the measurement meter; and obtaining a first resistance ratio by comparing the first and second associated resistances.

In another form of the present invention, a method for encoding information readable by a test meter onto a test strip is disclosed, wherein the test strip is adapted for use in measuring the concentration of an analyte of interest in a biological fluid. The method includes selecting a first resistance ratio associated with a first word desired to be encoded onto the test strip and forming a measurement electrode on a surface of the test strip substrate, wherein the measurement electrode is connectable to a test meter. The method also includes forming a first electrical trace and a second electrical trace on the surface of the test strip substrate, wherein the resistance of each of the first and second electrical traces is obtainable by the test meter, and wherein the resistance ratio of the first electrical trace and the second electrical trace effectively matches the first resistance ratio.

Drawings

The invention will be further described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is an exploded perspective view of a first exemplary test strip for measuring the concentration of an analyte of interest in a biological fluid.

FIG. 2 is a perspective view of a second exemplary test strip for measuring the concentration of an analyte of interest in a biological fluid.

Figure 3 shows a view of an ablation apparatus suitable for use with the present invention.

Fig. 4 is a view of the laser ablation apparatus shown in fig. 3 showing a second mask.

Fig. 5 is a view of an ablation apparatus suitable for use with the present invention.

FIG. 6 is a schematic process flow diagram of a prior art process for verifying the applicability of calibration data within a test meter to a test strip currently inserted into the test meter.

FIG. 7 is a schematic process flow diagram of the process of the first embodiment of the present invention for verifying the applicability of the calibration data within the test meter to the test strip currently inserted into the test meter.

FIG. 8 is a schematic plan view of a second embodiment test strip electrode and contact pad arrangement according to the present invention.

FIG. 9 is a schematic plan view of the test strip electrode and contact pad arrangement shown in FIG. 8 showing modified traces.

FIG. 10 is a schematic plan view of the test strip electrode and contact pad arrangement shown in FIG. 8 showing another modified trace.

FIG. 11 is a schematic plan view of the test strip electrode and contact pad arrangement shown in FIG. 8 showing yet another modified trace.

FIG. 12 is a schematic plan view of a third embodiment test strip electrode and contact pad arrangement according to the present invention.

FIG. 13 is a schematic plan view of a fourth embodiment test strip electrode and contact pad arrangement according to the present invention.

FIG. 14 is a schematic plan view of a fifth embodiment test strip electrode and contact pad arrangement in accordance with the present invention.

FIG. 15 is a schematic plan view of the test strip electrode and contact pad arrangement shown in FIG. 14 showing an alternative resistive element and modified traces.

Detailed Description

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and modifications in the illustrated device, and further applications of the principles of the invention as illustrated therein as would normally occur to one skilled in the art to which the invention relates are desired to be protected. In particular, while the present invention is discussed with respect to a blood glucose meter, it is envisioned that the present invention can be used with devices for measuring other analytes and other sample types. Such alternative embodiments require some modification to the embodiments discussed herein, as would be apparent to one of ordinary skill in the art.

While the system and method of the present invention may be used with test strips having a variety of designs and manufactured using a variety of construction techniques and processes, a typical electrochemical test strip is shown in FIG. 1 and is generally indicated at 10. Referring to fig. 1, test strip 10 includes a bottom substrate 12 formed of an opaque piece of 350 micron thick polyester, such as Melinex329, commercially available from DuPont, coated on the top surface with a 50 nanometer thick conductive (gold) layer (e.g., by sputtering or vapor deposition). The electrodes, connecting traces and contact pads are then patterned in the conductive layer by a laser ablation process. The laser ablation process is performed by means of an excimer laser through a mask of chrome on quartz. The mask pattern causes portions of the laser field to be reflected while allowing other portions of the field to pass through, creating a pattern on the gold ablated at the locations of the laser contacts. The laser ablation process is described in more detail below. For example, working electrode 20, counter electrode 22, dose sufficiency working electrode 24, and dose sufficiency counter electrode 26 may be formed as shown and coupled to measurement contact pad W, C, DW and DC, respectively. These contact pads provide conductive areas on the test strip 10 to contact the connector contacts of the test meter once the test strip 10 is inserted into the test meter. As used herein, the term "measurement contact pad" is defined as a contact pad on a test strip that is conductively coupled to a measurement electrode of the test strip and is the primary contact pad for measuring a characteristic of a bodily fluid sample, such as the sample size or concentration of an analyte within the sample. As used herein, the term "information contact pads" is defined as contact pads on test strips that are not measurement contact pads and are used to encode information onto the test strip.

The base substrate 12 is subsequently coated with the reactant layer 14 as a continuous, particularly thin film of reactant in the region extending over the electrodes. The reactant layer 14 is a strip of approximately 6 millimeters width across the substrate 12 in the region labeled "reactant layer" shown in fig. 1. For example, this zone may be coated with a wet coating weight of 50 grams per square meter of coated surface area. The reactant strips were conventionally dried using an in-line drying system, where the nominal air temperature was 110 degrees celsius. The rate of treatment is nominally 30-38 meters per minute and depends on the rheology of the reactants.

In the case of substrate 12, the material is processed in a continuous reel such that the electrode pattern is orthogonal to the length of the reel. Once the substrate 12 has been coated with the reactant, the spacers 16 are cut and the spacers 16 are placed onto the substrate 12 in a reel-to-reel process. Two spacers 16 formed of 100 micron polyester (e.g., Melinex329 available from DuPont) coated with 25 micron PSA (hydrophobic adhesive) on all dorsal and ventral surfaces were applied to the base substrate 12 such that the spacers 16 were 1.5 mm apart and the working, counter and dose sufficiency electrodes were centered within this gap. A top foil layer 18 (using the process described in U.S. patent No.5,997,817) formed of 100 micron polyester coated with a hydrophilic membrane on the surface of the abdomen is placed over the separator 16. The hydrophilic membrane was coated with a mixture of Vitel and Rhodapex surfactant at a nominal thickness of 10 microns. Top foil layer 18 is laminated using a reel-to-reel process. The test strip can then be produced from the resulting spool of material by means of slitting and cutting.

While the basic test strip 10 shown in FIG. 1 is capable of providing an accurate measurement of blood glucose in a whole blood sample, the test strip 10 does not provide any means for identifying any information about the test strip for the test meter into which the test strip 10 is inserted. The present invention proposes a system that is capable of encoding information relating to a test strip directly onto the test strip itself, so that this information can be conveyed to the test meter into which the test strip is inserted.

One method of preparing test strips encoded with information as described herein is by using laser ablation techniques. Examples of the use of these techniques to prepare Electrodes for biosensors are described in U.S. patent application publication No. 2002/0192115 entitled "biosensors" filed 5/25/2001 and U.S. patent No.6,662,439 entitled "Laser definefed dyes for Patterned dyes and Electrodes" filed 12/16/2003, both disclosures of which are hereby incorporated by reference in their entirety. As used herein, the term "encoding" is defined as the case where switching from one communication system to another and including controlling or manipulating particular aspects of the test strip in a manner that will provide information to the test meter. The systems and methods disclosed herein include methods of simulating comparison and situations where information is read by a test meter, transferred to a test meter, and collected from a test strip.

In the present invention, it is desirable to provide accurate placement of electrical components relative to each other and relative to the entire biosensor. In another embodiment, the relative placement of the components is achieved at least in part by using broad field laser ablation performed through a mask or other device having a precise pattern for the electrical components. This allows accurate positioning of the adjacent edges, which is also enhanced by the close tolerance of the smoothness of the edges.

Fig. 2 shows a simple biosensor 401 for illustrating the laser ablation process of the present invention, comprising a substrate 402, the substrate 402 having a conductive material 403 formed thereon, the conductive material 403 defining an electrode system comprising a first set of electrodes 404 and a second set of electrodes 405, and corresponding traces 406, 407 and contact pads 408, 409, respectively. The conductive material 403 may comprise a pure metal or alloy or other material that is a metallized conductor. The conductive material is typically absorptive at the wavelength of the laser used to form the electrodes and of a thickness suitable for rapid and accurate processing. Non-limiting examples include aluminum, carbon, copper, chromium, gold, Indium Tin Oxide (ITO), palladium, platinum, silver, tin oxide/gold, titanium, mixtures thereof, and alloys or metal compounds of these elements. In some embodiments, the conductive material comprises a noble metal or alloy or an oxide thereof. In other embodiments, the conductive material includes gold, palladium, aluminum, titanium, platinum, ITO, and chromium. In other embodiments, the thickness of the conductive material ranges from about 10 nanometers to 80 nanometers. In still further embodiments, the thickness of the conductive material ranges from about 30 nanometers to 70 nanometers. In a further embodiment, the thickness of the conductive material is equal to about 50 nanometers. It will be appreciated that the thickness of the conductive material depends on the transmissive properties of the material and other factors associated with the use of the biosensor.

Although not illustrated, it should be understood that the resulting patterned conductive material can be coated or plated with additional metal layers. For example, the conductive material may be copper, which is subsequently ablated with a laser to form the electrode pattern; the copper may then be plated with a titanium/tungsten layer, and subsequently with a gold layer, to form the desired electrodes. In some embodiments, a single layer of conductive material on the base 402 is used. Although not generally necessary, the attachment of the conductive material to the substrate may be enhanced by the use of a seed or auxiliary layer, such as chromium nickel or titanium, as is well known in the art. In other embodiments, biosensor 401 has a single layer of gold, palladium, platinum, or ITO.

As shown in fig. 3-5, biosensor 401 is illustratively manufactured using two devices 410, 410', respectively. It should be understood that the devices 410, 410' operate in a similar manner unless otherwise described. Referring first to fig. 3, biosensor 401 is fabricated by feeding a spool of approximately 40 mm wide ribbon 420 with 80 nm gold laminations into a custom fit wide field laser ablation apparatus 410. The apparatus 410 comprises a laser source 411 producing a beam of laser light 412, a chrome-plated quartz mask 414, and optics 416. It should be appreciated that although the illustrated optical device 416 is a single lens, in some embodiments, the optical device 416 is a plurality of lenses that cooperate to form the predetermined shape of the light 412.

A non-limiting example of a suitable ablation apparatus 410 (FIGS. 3-4) is a custom made MicrolineLaser 200-4 laser system, commercially available from LPKFLaser Electronic GmbH, of Garbsen, Germany, which incorporates an LPX-400, LPX-300 or LPX-200 laser system, commercially available from Lambda Physik AG, Gottingen, Germany, and a chrome plated quartz mask, commercially available from International Phototool Company, Colorado Springs, Co.

For the MicrolineLaser 200-4 laser system (FIGS. 3-4), the laser source 411 is LPX-200 KrF-UV-laser. However, it should be understood that higher wavelength UV lasers can be used in accordance with the present disclosure. The laser source 411 was operated at 248 nm with a pulse energy of 600mJ and a pulse repetition rate of 50 Hz. The intensity of the laser beam 412 can be infinitely adjusted between 3% and 92% by a dielectric beam attenuator (not shown). The beam profile was 27 x 15 square millimeters (0.62 square inches) and the pulse duration was 25 nanoseconds. The layout on the mask 414 is uniformly projected by an optical element beam expander, homogenizer, and objective lens (not shown). The performance of the homogenizer has been determined by measuring the energy profile. Imaging optics 416 transfer the structure of the mask 414 onto the ribbon 420. The imaging ratio was 2: 1 to allow removal of large areas on the one hand and to keep the energy density below the ablation spot of the applied chromium mask on the other hand. While 2: 1 imaging is illustrated, it should be understood that any number of alternative ratios are possible in accordance with the present disclosure, depending on the desired design requirements. The ribbon 420 moves as indicated by arrow 425 to allow for ablation of multiple layout segments in succession.

The positioning of the mask 414, the movement of the ribbon 420, and the laser energy are computer controlled. As shown in FIG. 3, the laser beam 412 is projected onto the ribbon 420 to be ablated. Light 412 passing through transparent regions or windows 418 of the mask 414 ablates metal from the ribbon 420. Chromium coated areas 424 of mask 414 block laser light 412 and prevent ablation in those areas, resulting in a metallized structure on the surface of ribbon 420. Referring now to FIG. 4, a complete structure of electrical components may require an additional ablation step through a second mask 414'. It should be understood that depending on the optics and the size of the electrical components to be ablated, only a single ablation step or more than two ablation steps may be necessary in accordance with the present disclosure. Further, it should be understood that multiple fields may be formed on the same mask instead of multiple masks in accordance with the present disclosure.

In particular, a second non-limiting example of a suitable ablation apparatus 410' (FIG. 5) is a custom Laser system commercially available from LPKF Laser Electronic GmbH, of Garbsen, Germany, which combines a Lambda STEEL (Stable energy excimer Laser) Laser system commercially available from Lambda Physik AG, Gottingen, Germany and a chrome plated quartz mask commercially available from International photo Company, Colorado Springs, Co. The laser system is characterized by pulse energies up to 1000mJ at a wavelength of 308 nanometers. In addition, the frequency of the laser system was 100 Hz. The device 410' may be formed as shown in fig. 3 and 4 to produce a biosensor in two passes. In certain embodiments, the optics of apparatus 410' allow for a single pass to form a 10 x 40 mm pattern at 25 nanoseconds.

While not wishing to be bound by a particular theory, it is believed that the laser pulse or beam 412 passing through the mask 414, 414', 414 "is absorbed within less than 1 micron of the surface 402 on the ribbon 420. The energy of the photons of beam 412 is sufficient to cause photolysis and the rapid destruction of chemical bonds at the metal/polymer interface. This rapid chemical bond disruption is believed to result in a sudden pressure increase within the absorbing region and drive material (metal film 403) to be expelled from the polymer substrate surface. Because the typical pulse duration is around 20-25 nanoseconds, interaction with the material occurs very rapidly and thermal damage to the edges of the conductive material 403 and surrounding structures is minimized. The resulting edges of the electrical components have high edge quality and accurate placement as contemplated by the present invention.

The fluence energy used to remove or ablate the metal from the ribbon 420 depends on the material from which the ribbon 420 is formed, the adhesion of the metal film to the base material, the thickness of the metal film, and possibly the process used to place the film on the base material, i.e., support and vapor deposition. For gold in KALADEXThe fluence levels above range from about 50 to about 90 mJ/cm, about 100 to about 120 mJ/cm on polyimide, and MELINEXAnd from about 60 to about 120 mJ/cm. It should be understood that fluence levels less than or greater than those mentioned above may be suitable for other base materials in accordance with the present disclosure.

Patterning of the regions of ribbon 420 is achieved by using masks 414, 414', and 414 ". Each mask 414, 414' and 414 "illustratively includes a mask field 422 containing a precise two-dimensional map of a predetermined portion of the electrode component pattern to be formed. Fig. 3 shows a mask field 422 that includes contact pads and a portion of a trace. As shown in fig. 4, the second mask 414' contains a second corresponding portion of the trace and an electrode pattern containing fingers. As previously mentioned, it should be understood that the mask 414 can contain a complete map of the electrode pattern (fig. 5), or portions of patterns different from those shown in fig. 3 and 4 in accordance with the present disclosure, depending on the size of the area to be ablated. It is envisioned that in one aspect of the present invention, the entire pattern of electrical components on the test strip, i.e., the wide field encompassing the entire size of the test strip, is laser ablated at one time, as shown by mask 414 "shown in FIG. 5. In the alternative, and as shown in fig. 3 and 4, multiple portions of the entire biosensor are fabricated in succession.

While mask 414 will be discussed below, it should be understood that the discussion will apply equally to masks 414', 414 "unless otherwise noted. Referring to FIG. 3, areas 424 of the mask field 422 protected by the chrome will block the projection of the laser beam 412 to the ribbon 420. A transparent region or window 418 within the mask field 422 allows the laser beam 412 to pass through the mask 414 and impinge a predetermined area of the ribbon 420. As shown in fig. 3, the transparent regions 418 of the mask field 422 correspond to the regions of the ribbon 420 from which the conductive material 403 is to be removed.

Further, the length of the mask field 422 is shown by line 430 and the width is shown by line 432. Given an imaging ratio of 2: 1 for LPX-200, it will be appreciated that the length 430 of the mask is twice the length of the length 434 of the resulting pattern, and the width 432 of the mask is twice the width of the width 436 of the resulting pattern on the ribbon 420. The optics 416 reduce the size of the laser beam 412 that impacts the ribbon 420. It should be understood that the relative sizes of the mask field 422 and the resulting pattern may vary in accordance with the present disclosure. Mask 414' (FIG. 4) is used to complete a two-dimensional view of the electrical components.

With continued reference to FIG. 3, in laser ablation apparatus 410, excimer laser source 411 emits beam 412, and beam 412 passes through a chrome-on-quartz mask 414. The mask field 422 causes part of the laser beam 412 to reflect while allowing other parts of the beam to pass through, forming a pattern on the gold film where impacted by the laser beam 412. It should be understood that ribbon 420 may be stationary relative to apparatus 410 or continuously moved on a spool by apparatus 410. Thus, a non-limiting rate of movement of the ribbon 420 can be from greater than 0m/min to about 100 m/min. In some embodiments, other non-limiting rates of movement of the ribbon 420 may be from about 30m/min to about 60 m/min. It should be understood that the rate of movement of the ribbon 420 is limited only by the apparatus 410 selected and may exceed 100m/min depending on the pulse duration of the laser source 411 in accordance with the present disclosure.

Once the pattern of the mask 414 is formed on the ribbon 420, the ribbon is rewound and fed through the apparatus 410 again, with the mask 414' (fig. 4). It should be understood that laser devices 410 may alternatively be positioned in series in accordance with the present disclosure. Thus, by using masks 414, 414', a large area of ribbon 420 can be patterned using a repeated step process, including multiple mask fields 422 within the same mask area, to enable complex electrode patterns and other electrical components to be economically formed on a substrate of a base, precise edges of the electrode components to be formed, and a greater amount of metal film to be removed from the base material.

The ability to encode information directly onto the test strip can significantly increase the performance of the test strip as well as enhance the interaction of the test strip with the test meter. For example, it is well known in the art to supply a test meter with calibration data for test strips appropriate for any given production lot. Typically, this is accomplished by supplying a read-only memory key (ROM key) with each vial of test strips, where the ROM key has encoded thereon calibration data suitable for the test strips within the vial. Prior to using the test strip from the vial, the user inserts the ROM key into a port within the test meter so that the test meter can access this data while performing a test using the test strip. The quality of the measurement results can be verified by allowing the meter to electronically assess the applicability of the ROM key data to the test strip currently inserted into the meter, without the need for an optical reader to read the barcode information on the test strip as taught in the prior art.

Currently commercially available products require the user to be concerned with verifying that the correct ROM key for the currently used test strip has been inserted into the test meter. For example, FIG. 6 illustrates a typical prior art process for verifying a match between ROM key data and a test strip lot Identifier (ID) number. Before this process is performed, the ROM key has been inserted into the test meter, the ROM data has been loaded into the test meter, and the test meter is shut down. The process begins by inserting a test strip into the test meter (step 100), which causes the test meter to automatically turn on (step 102). The test meter displays the lot ID of the currently loaded calibration data (step 104) to give the user the opportunity to verify that this lot ID matches the lot ID printed on, for example, bottles/packages containing multiple test strips from the same production lot as the test strip currently inserted into the test meter.

Because the process relies on the user to perform this check, there is no guarantee that the check will be performed or, if performed, that it will be performed accurately. Thus, the process shown in FIG. 6 indicates optional steps for the user to compare the lot ID on the test meter display to the lot ID on the test strip vial (step 106) and to determine (step 108) if there is a match. If the two lot IDs do not match, the user should remove the test strip (step 110) and insert the ROM key of the matching test strip vial into the test meter (step 112) so that the correct calibration code can be loaded into the test meter. The process will then begin at step 100 when a test strip is inserted. Once it has been determined that the calibration code lot ID of the test meter matches the lot ID of the test strip (step 108), the measurement sequence can continue by supplying blood to the test strip (step 24) and beginning a blood glucose measurement cycle (step 116).

It will be appreciated that in the prior art process shown in figure 6, the responsibility for verifying the accuracy of the measured calibration data is fully assumed by the user. Situations are sometimes encountered where the user ignores the prescribed instructions for use provided with the test strip. One such example is the removal of test strips manufactured in lot X from a first vial and the incorporation of these test strips within a second vial containing test strips manufactured in lot Y. It is therefore desirable to provide batch-specific calibration information to the individual test strip level rather than to the vial level as in the prior art.

To remove the possibility of human error or inattention from the process, and thereby improve the quality of the measurement, the information contact pads of the present invention allow the test meter itself to perform a check on the suitability of the currently loaded calibration data for the currently inserted test strip. FIG. 7 illustrates the process of the first embodiment of the present invention that allows the test meter to actively participate in such a verification. Steps of the process shown in fig. 7 that are identical to corresponding steps in fig. 6 are numbered with the same reference indicators.

Before this process is performed, the ROM key has been inserted into the test meter, the ROM data has been loaded into the test meter, and the test meter is shut down. The process begins by inserting a test strip into the test meter (step 100), which causes the test meter to automatically turn on (step 102). The test meter then measures the conductivity between the different information on the test strip that has been designated for encoding information onto the test strip and the measurement contact pads in order to determine the lot or family ID of the test strip (step 200). Depending on the amount of information that may be encoded onto the test strip, it may or may not be possible to encode a unique production lot number onto the test strip. If there is not enough space to encode a unique production lot ID, it is still possible to encode calibration family information onto the test strip. For example, test strips that can be used in a test meter can be in two or more families where there are significant differences between the family test strip designs. For example, the two families may use different reagents on the test strip. In such a case, the test meter is still able to verify that the loaded calibration data matches the test strip family encoded onto the test strip, even if it is not possible to verify the exact production lot of test strips. Thus, as used herein, the term "lot ID" is intended to include any information that identifies the group to which the test strip or calibration data belongs, even if the group is not as small as a production lot of test strips.

Returning to the process illustrated in FIG. 7, the test meter compares (step 202) the batch ID of the calibration data stored in the ROM key currently inserted into the meter (or calibration data previously loaded into the test meter internal memory) to the batch ID read from the test strip. If they do not match, the test meter displays the lot ID of the currently loaded calibration data (step 204) and an alert to give the user the opportunity to insert the correct test strip or a different ROM key into the test meter. Alternatively, the test meter may simply display an error message to the user. The fact that the lot IDs do not match is flagged (step 206) in the test meter's results memory 208 so that the measurements obtained due to the lot ID differences are recorded in the memory 208 as suspect. Alternatively, the user may be prohibited from performing the verification and the process may be aborted.

Because in some embodiments it is desirable to not fully disable the test meter if the lot IDs do not match, the process shown in FIG. 7 instructs the user with the optional step of comparing the lot ID on the test meter display to the lot ID on the test strip vial (step 106) and determining (step 108) whether there is a match. If the two lot IDs do not match, the user should remove the test strip (step 110) and insert the ROM key of the matching test strip vial into the test meter (step 112) so that the correct calibration code can be loaded into the test meter. The process will then begin at step 100 when a test strip is inserted.

Still alternatively, if the test meter is capable of storing more than one calibration data set within the meter's internal memory, the meter may determine a plurality of lot IDs of calibration data that may be stored within the test meter and automatically select the calibration data set that matches the test strip currently inserted into the meter. The meter then returns to step 24.

Once it has been determined that the calibration code lot ID of the test meter matches the lot ID of the test strip (step 108), the measurement sequence can continue by supplying blood to the test strip (step 24) and beginning a blood glucose measurement cycle (step 116). It should be appreciated that the process shown in FIG. 7 improves upon the prior art process shown in FIG. 6 by automatically alerting the user when the lot ID of the test strip does not match the lot ID of the currently selected calibration data set. Furthermore, if the test is conducted with such a mismatched combination, the results memory within the test meter is flagged to indicate that the results may not be as accurate as if the correct calibration data set were used.

As a further example of the usefulness of encoding information directly onto a test strip, the present invention allows the test strip to activate or deactivate certain features programmed into the test meter. For example, a single test meter may be designed for several different regional markets, with different languages spoken in each market. By encoding the test strip with information indicating which market the test strip is sold in, the encoded information can cause the test meter to display user guidance and data in a language appropriate for that market. Further, the meter may be designed for marketing in a certain region, and it is desirable that the meter not be used with test strips that are commercially available in a different region (e.g., when governmental regulations require test strips marketed in one region to have different characteristics than those marketed in other regions). In this case, the test meter may use the information encoded onto the test strip to determine that the test strip is not from a specified geographic market and therefore may not provide the features required by regulations, in which case the test may be aborted or flagged.

Further, a business model (subscription business model) may be applied to the distribution of test strips, where the diffusion of test strips into other sales channels is undesirable. For example, users may engage in a subscription procedure in which they are provided with a test strip designed for use by a subscribing participant, and may be provided with a subscription test strip on a regular basis (e.g., by mail or any other convenient form of delivery) for the subscribing participant. Using the techniques of the present invention, "subscription test strips" may be encoded to indicate that they are supplied to a subscription participant. For various reasons, the manufacturer of the subscription test strips may not wish to sell the subscription test strips in other channels of commerce. One way to prevent this is to design a test meter that is provided to a user who is not a subscription participant to not work with the subscription test strip. Thus, the present invention may be used to provide a subscription participant with test meters in a subscription business model that are programmed to accept subscription test strips that are coded to indicate that they are delivered to subscription-based users, and other test meters that are programmed to not accept subscription test strips so coded.

As a further example, the test meter may have certain functionality (software and/or hardware implemented) designed into the meter that is not active when the test meter is first sold. The performance of the test meter can be upgraded at a later date by including information encoded on the test strip sold at that later time that will be recognized by the meter as an instruction to activate these potential features. As used herein, the term "activating a potential feature of the test meter" includes turning on a previously inactive test meter function so that the test meter function remains activated indefinitely thereafter (i.e., after the current test with the present test strip is completed).

Another example of information that can be encoded onto a test strip using the present invention is an indication of whether the test strip is sold to the hospital market or the consumer market. Having this information may allow the test meter to take action accordingly, such as displaying less detailed user guidance for hospital professionals. Those of ordinary skill in the art will appreciate that different types of communication between the test strip and the test meter may be facilitated by providing information encoding via the present invention.

8-15 illustrate systems and methods for encoding information onto a test strip. These encoding systems and methods can be used exclusively on test strips, and can also be used in conjunction with other encoding systems and methods. In general, the encoding systems and methods shown in FIGS. 8-15 provide for the resistance of at least one trace or trace loop connected to an associated pair of contact pads to vary between test strips according to the information to be encoded onto each individual test strip. The test meter, in turn, measures the resistance of the trace or trace loop between a particular pair of contact pads on the inserted test strip and decodes resistance related information encoded on the test strip. In general, a test meter can determine the presence or absence of a connection digitally and can measure the resistance between any connected contact pads in an analog manner. The ability of the test meter to obtain digital and analog information allows the system and method of the present invention to be integrated with other encoding systems. When combined with other encoding systems and methods, such as those disclosed in JP2000/000352034 a2 and EP1152239 a1, which are hereby incorporated by reference in their entirety, the number of words that can be encoded on a test strip can be significantly increased over what can be encoded using other systems alone.

Alternative encoding schemes may also be used in which the trace or trace loop resistance is compared or proportionally compared to at least one other trace or trace loop resistance. This alternative encoding scheme has benefits in compensating for inconsistencies resulting from variations in trace or trace loop resistance from test strip to test strip.

In contrast to the encoding system and method of the present invention, some prior systems would have examined test strip resistance as a failsafe against inadvertent opens, scratches, or multi-point defects. Other prior systems attempt to compensate for unwanted test strip trace resistance. Still other prior systems only determine whether a significant trace resistance is present and use the presence or absence of a significant resistance as a binary indicator of which of the two types of strips is present, the strip intended for measurement or calibration purposes. In systems using resistance as a binary indicator, the determination of whether a particular trace has an important resistance is accomplished by comparing the measured resistance to a threshold resistance value near zero. If the measured resistance is above the threshold, the trace resistance is considered important, thereby indicating a type of bar. If the measured resistance is below the threshold, the trace resistance is considered insignificant and substantially zero, and another type of bar is indicated. Thus, the system only distinguishes between substantially zero and non-zero resistance values. In contrast, the systems and methods of the present invention are generally capable of distinguishing between at least two substantially non-zero resistance values.

In general, the systems and methods disclosed in the present invention for encoding information onto a test strip are used to: identifying a particular type of test strip; determining whether the inserted test strip matches a separate encoding key inserted into the test meter; encoding the calibration information directly onto the test strip; identifying an important parameter associated with the test strip, such as country of origin, destination, or particular test strip chemistry; and determining which reactants are on the test strip. The system and method of the present invention also provides for encoding information onto a test strip that can be used to: selecting a language for displaying user operation instructions by the inspection instrument; determining whether the test meter and the test strip are sold in the same geographic market; preventing the test meter from using the test strip if the test strip is a predetermined test strip; activating a latent feature of the test meter; changing the user operation guide; or perform other functions as would be apparent to one of ordinary skill in the art.

A second embodiment test strip configuration that allows information to be encoded directly onto the test strip is shown in fig. 8 and indicated generally at 700. Test strip 700 may be formed generally as described above with respect to test strips 10 and 401, with working electrode 720, counter electrode 722, dose sufficiency working electrode 724, and dose sufficiency counter electrode 726 formed as shown and coupled to working electrode trace 721, counter electrode trace 723, dose sufficiency working electrode trace 725, and dose sufficiency counter electrode trace 727, respectively, which are further coupled to measurement contact pads W, C, DW and DC, respectively. Test strip 700 also includes working electrode sense trace 730 and counter electrode sense trace 732 coupled to measurement contact pads WS and CS, respectively. The contact pads provide conductive areas on the test strip 700 to contact the electrical connector contacts of the test meter once the test strip 700 is inserted into the test meter. The electrical connector allows electrical signals to be applied from the test meter to the test strip and vice versa. By way of example, the test strip may have a sample inlet formed in the distal end of the test strip (as shown in FIG. 8), or the sample inlet may be on the side of the test strip (as shown in FIG. 1). The type of sample inlet is not relevant to the functionality of the embodiments described herein.

Referring to the traces connected to contact pads W and WS, the resistance along the three portions between contact pads W and WS can be evaluated by a test meter: the resistance of working electrode trace 721 between the points where contact pad W and working electrode sense trace 730 connect, the resistance of sense trace 730 between the points where contact pad WS and electrode sense trace 720 connect, and the trace loop resistance- "trace loop W-WS" between contact pads W and WS. In the first case, the test meter can measure the potential of working electrode trace 721 using working electrode sense trace 730 at the point where sense trace 730 connects to electrode trace 721 using a voltage follower circuit or other similar methods known in the art (see, e.g., the methods and circuits disclosed in co-pending application serial No. 10/961,352, incorporated by reference above). Because the potential and current at contact pad W can be measured directly by the test meter, the change in potential and thus the resistance of working electrode trace 721 between the point along contact pad W and working electrode sense trace 730 that intersects working electrode trace 721 can be calculated by the test meter. The resistance along working electrode sense trace 730 can similarly be calculated by the test meter.

Alternatively, the resistance of trace loop W-WS can be calculated by measuring the total change in potential between contact pads W and WS and the current flow therebetween. The calculated resistance along the trace loop includes the connector contact resistance between the test meter and the contact pads, the trace loop resistance, and the resistance of any analog switches within the measurement path of the test meter. In an exemplary embodiment, trace loop W-WS comprises a gold conductive material and has a nominal resistance of about 287 ohms. In another exemplary embodiment, the trace loop W-WS comprises a palladium conductive material and has a nominal resistance of about 713 ohms.

The resistance of the trace loop may be measured by either ac or dc excitation. In one exemplary embodiment, W-WS loop resistance is measured by DC excitation, while C-CS loop resistance is measured by AC excitation. Other exemplary embodiments measure trace and trace loop resistance on a test strip using different combinations of alternating current and/or direct current excitation, some embodiments exclusively using alternating current excitation, while other embodiments exclusively use direct current excitation.

Referring to the traces connected to contact pads C and CS, each of the resistance of counter electrode trace 723 between the points along contact pad C and the connection of counter electrode sense trace 732, the resistance of sense trace 732 between the points along contact pad CS and the connection of electrode trace 723, and the trace loop C-CS resistance between contact pads C and CS can be determined by a test meter in a similar manner as described above with respect to the traces connected to contact pads W and WS. In an exemplary embodiment, the trace loop C-CS comprises a gold conductive material and has a resistance of about 285 ohms. In another exemplary embodiment, the trace loop C-CS comprises a palladium conductive material and has a resistance of about 712 ohms.

Test strip 700 also includes information traces 734 and 736 that are connected to information contact pads B1 and B2, respectively. The information traces 734 and 736 are further connected to the dose sufficiency counter electrode trace 727 and the counter electrode trace 723, respectively. Not only can the information contact pads B1 and B2 and their associated trace loops be used with the encoding systems and methods shown in FIGS. 1-15 and described above, the different trace resistance values of the trace loops DC-B1 and C-B2 can be used to further encode information onto the test strip 700. For example, the resistance values of trace 734, trace 736, the portion of trace 727 between contact pad DC and the point where trace 734 connects, the portion of trace 723 between contact pad C and the point where trace 736 connects, trace loop DC-B1, and trace loop C-B2 can all be individually measured and used to encode information onto test strip 700 in a manner similar to that described above with respect to the traces connected to contact pads W and WS.

Information digitally encoded onto the test strip provides a limited number of options for encoding the information, e.g., the test strip may be limited to 2^NA possible state or word, where N is the number of information contact pads on the test strip. Conversely, the resistance measured by the test meter is generally not limited to discrete values, and any value along a continuum of possible trace resistance values may be measured. Thus, the number of words or states that can be encoded onto the test strip using a continuous region of trace resistance values can exceed the number of discrete digital states usedThe number of words or states that can be encoded onto the test strip, using discrete digital states, generally only determines whether there is a connection between two contact pads.

The number of possible words and the amount of information that can be encoded onto the test strip using the resistance of the test strip trace or trace loop is typically limited by the ability to accurately manufacture a particular trace resistance and the ability to accurately measure that trace resistance. Given the ability to accurately control resistance and accurately measure trace or trace loop resistance during manufacturing, a theoretically infinite amount of information can be encoded onto the test strip, with each measurable resistance along a continuous zone corresponding to a different word or state. However, due to practical manufacturing and measurement capabilities, the number of usable resistance values along a continuum is often limited. To account for measurement and manufacturing errors, the number of states available along a continuum may be subdivided into a number of discrete ranges, where each discrete range corresponds to a different word or state, and the range of resistance values associated with each range is approximately as large as the cumulative measurement and manufacturing errors. In one exemplary embodiment, information regarding the number of discrete ranges or the size of each discrete range may be programmed onto a ROM key inserted into the test meter.

The method used to measure the resistance and other factors such as the temperature of the test strip and the test meter can also affect the resistance measured by the test meter and the minimum size of each discrete range that can be used. For example, in one embodiment of the invention, the measured trace or trace loop resistance comprises the resistance of at least one analog switch internal to the test meter, wherein the analog switch resistance varies between 10 and 180 ohms depending on temperature and manufacturing tolerances. For exemplary purposes, if it is assumed that the resistance measurement accuracy of the test meter is +/-30 ohms, then the minimum size of each discrete range that can be used to encode information onto the test strip is at least 60 ohms.

As described above, one advantage of trace or trace loop resistance encoding systems and methods is that they can be used in conjunction with other systems. Even when limiting the usable states along a continuum of possible resistance values to a discrete range, combining trace loop resistance encoding with other encoding methods can significantly increase the total number of words that can be encoded onto a test strip compared to what can be encoded using other methods alone.

The encoding system and method as an example utilizes discrete ranges of resistance, assuming that the resistance along each of the W-WS and C-CS trace loops shown in FIG. 8 is limited to one of three measurable resistance ranges represented by range numbers 1, 2, and 3. Thus, by measuring the resistance of trace loops W-WS and C-CS, a total of nine different words can be encoded on test strip 700: WS1/CS1, WS1/CS2, WS1/CS3, WS2/CS1, WS2/CS2, WS2/CS3, WS3/CS1, WS3/CS2, and WS3/CS 3. In combination with this resistive encoding scheme and another encoding scheme, the total number of states that can be encoded can be increased by a factor of 9. For example, JP 2000/000352034A 2 potentially discloses a total of 8 states that can be encoded onto the side of the test strip with measurement electrodes. Combining the current example with JP2000/000352034 a2 results in a total of 72 states that can be encoded onto the test strip. In general, the system and method of resistive encoding specifically using traces or trace loops provides a total of R that can be encoded onto a test strip^LA unique word, and the use of a trace or trace loop resistance encoding system in combination with another encoding system increases the total word that can be encoded onto the test strip by a factor R in comparison to other encoding systems^LAnd (4) respectively.

In general, the resistance of a particular trace as measured by a test meter varies at least in part with trace width, trace length, trace thickness, trace conductive material, trace temperature, and test meter switch resistance. Factors such as the precise width, length, thickness, and conductive material of the traces can be controlled during manufacturing, but manufacturing inconsistencies can result in unintended variations in resistance, resulting in trace resistance values that differ from predetermined. In addition, these factors can also vary from test strip to test strip and from production lot to production lot, despite the same test strip mask configuration. However, despite these manufacturing inconsistencies, the ratio of the resistance values of the two traces or trace loops generally remains relatively consistent for a given test strip mask configuration. Thus, a technique that test meters can use to counteract manufacturing inconsistencies is to compare two trace or trace loop resistance measurements. Using this or similar techniques, the test meter is able to effectively compensate for changes in resistance by evaluating the ratio of resistance between traces or trace loops, particularly if necessary the test meter analog switches are paired in type, size, process and packaging.

As an example, manufacturing inconsistencies in the amount of conductive material deposited on the substrate can result in trace thickness varying from test strip to test strip for a given test strip mask configuration, while trace width and length remain relatively constant. However, these inconsistencies in the amount of conductive material deposited tend to vary slowly enough that trace thickness tends to be uniform across a single test strip, while varying from test strip to test strip. Thus, despite manufacturing inconsistencies, the ratio of trace resistances between two traces on the same test strip will remain substantially constant.

Variations in trace width, length, thickness, and material composition can be manipulated during manufacturing to control individual trace resistance values because, as described above, these characteristics affect the resistance of each trace. For example, the resistance of the C-CS trace loop can be reduced by increasing the width of counter electrode trace 723 or counter electrode sense trace 732 or by reducing the overall length of the loop. Similarly, the resistance of the C-CS loop can be increased by decreasing the width of trace 723 or 732 or by increasing the effective overall length of the loop.

Alternate embodiments utilize different test strip mask configurations. The number, location, or particular type of electrode traces to which the information traces can be connected can vary, with the only limitation that the functionality of the test strip cannot be compromised by, for example, connecting any electrodes or electrode traces to each other.

Referring now to FIG. 9, an alternative exemplary embodiment test strip 700' is shown that is similar to test strip 700 except as noted below. Working electrode sense trace 730' is wider than working electrode sense trace 730. In this exemplary alternative embodiment, the W-WS trace loop resistance within test strip 700' is less than the W-WS trace loop resistance within test strip 700. Similarly, as the width of sense trace 730 'increases, the ratio of W-WS loop resistance to C-CS loop resistance in test strip 700' is less than the ratio of W-WS loop resistance to C-CS loop resistance in test strip 700. Thus, information is encoded onto test strips 700 and 700' by varying trace widths. Thus, the test meter can distinguish test strip 700 from test strip 700' by, for example, measuring the absolute resistance in trace loop W-WS, measuring the absolute resistance in a segment of trace loop W-WS, or by determining the ratio of the W-WS trace loop resistance and the C-CS trace loop resistance.

Referring now to FIG. 10, there is shown yet another exemplary embodiment test strip 700 "that is similar to test strip 700 except as noted below. Test strip 700 "includes an alternate working electrode sense trace 730". Sense trace 730 "differs from sense trace 730 in that sense trace 730" is shorter than sense trace 730. In this exemplary alternative embodiment, the W-WS trace loop resistance within test strip 700' is less than the W-WS trace loop resistance within test strip 700. Similarly, as the length of sense trace 730 "is reduced, the ratio of W-WS loop resistance to C-CS loop resistance in test strip 700" is less than the ratio of W-WS loop resistance to C-CS loop resistance in test strip 700. Thus, information is encoded onto test strips 700 and 700' by varying trace lengths. Thus, the test meter can distinguish test strip 700 from test strip 700 "by, for example, measuring the absolute resistance in trace loop W-WS, measuring the absolute resistance in a segment of trace loop W-WS, or by determining the ratio of the W-WS trace loop resistance and the C-CS trace loop resistance.

FIG. 11 illustrates yet another exemplary embodiment of a test strip 700Test strip 700Is a variation of test strip 700 and differs from test strip 700 as noted below. Test strip 700Including counter electrode sense trace 732 ', counter electrode sense trace 732' has a longer and narrower electrical path length and thus higher resistance than sense trace 732. In this exemplary alternative embodiment, test strip 700The C-CS trace loop resistance in is greater than the C-CS trace loop resistance in test strip 700. Similarly, test strip 700 due to the increased length of sense trace 732', test stripThe ratio of the W-WS loop resistance to the C-CS loop resistance within is less than the ratio of the W-WS loop resistance to the C-CS loop resistance within test strip 700. Thus, information is encoded onto test strips 700 and 700' by varying trace lengths. Thus, the test meter can distinguish between test strip 700 and test strip 700 by, for example, measuring the absolute resistance within trace loop C-CS, measuring the absolute resistance within a segment of trace loop C-CS, or by determining the ratio of the W-WS trace loop resistance and the C-CS trace loop resistance。

The third embodiment test strip configuration is shown in FIG. 12 and is generally designated 800. Unless otherwise indicated, the test strip 800 is generally similar to the test strip 700 described above, with working electrode 820, counter electrode 822, dose sufficiency working electrode 824, dose sufficiency counter electrode 826, working electrode sense trace 830, and counter electrode sense trace 832 formed as shown and coupled to measurement contact pads W, C, DW, DC, WS and CS, respectively. In contrast to test strip 700, test strip 800 includes information trace 834 and information trace 836 connected to information contact pads B1 and B2, respectively, and further connected to each other. These contact pads provide conductive areas on the test strip 800 to contact the electrical connector contacts of the test meter once the test strip 800 is inserted into the test meter.

In the illustrated embodiment of the test strip 800, the information trace 834 and the information trace 836 combine to provide a trace loop B1-B2 between the information contact pads B1 and B2. The resistance of at least one of the information traces 834 and 836 can be varied to encode information other than that which can be encoded using the trace loops W-WS and C-CS. When the test meter is inserted, test strip 800 can be distinguished from test strip 700 because contact pads DC and B1 are not connected, because contact pads C and B2 are not connected, and because contact pads B1 and B2 are connected. Test strip 800 can also be distinguished from test strip 700 based on the measured values of the B1-B2 loop resistance. In general, a test meter can determine the presence or absence of a connection digitally and can measure the resistance between any connected contact pads in an analog manner. The resistance of the information traces 834 and 836 can be varied by varying the width, thickness, length of the information traces 834 and 836, or the material used to construct the information traces 834 and 836, during fabrication.

The fourth embodiment test strip configuration is shown in FIG. 13 and is generally designated 900. Test strip 900 may be formed with working electrode 920, dose sufficiency working electrode 924, information trace 934 and information trace 936 formed as shown and coupled to measurement contact pads W and DW and information contact pads B1 and B2, respectively. In addition, test strip 900 includes counter electrode 922 and dose sufficiency counter electrode 926 connected to counter electrode trace 923 and dose sufficiency counter electrode trace 927, respectively, which are in turn further connected to measurement contact pads C and DC, respectively. Similar to the test strips 700 and 800, the contact pads provide conductive areas on the test strip 900 to contact the electrical connector contacts of the test meter once the test strip 900 is inserted into the test meter.

In the test strip 900 of the exemplary embodiment, information trace 934 is electrically connected to dose sufficiency counter electrode trace 927, and information trace 936 is electrically connected to counter electrode trace 923. These electrical connections provide additional trace loops where the resistance between contact pads DC and B1, and C and B2 can be measured. When connected to the test meter, the lack of electrical connection between contact pads B1 and B2, the presence of electrical connection between contact pads B1 and DC, and the presence of electrical connection between contact pads B2 and C each separately encode information and distinguish the test strip 900 from the test strip 800. In addition, the resistances along dose sufficiency counter electrode trace 927, information trace 934, information trace 936, and counter electrode trace 923 can still further encode additional information about test strip 900.

In addition, information traces 934 and 936 are longer and have a greater resistance than information traces 734 and 736 when compared to test strip 700. Thus, the DC-B1 and C-B2 trace loop resistances within test strip 900 are greater than the DC-B1 and C-B2 trace loop resistances within test strip 700, respectively. Thus, the test meter can distinguish the test strip 900 from the test strip 700 by, for example, measuring the absolute resistance of the trace loop DC-B1 or C-B2, or by comparing the resistance ratios of the trace loop DC-B1 or C-B2 to each other or to other trace loops such as the trace loop W-WS or C-CS.

Turning now to fig. 14 and 15, a fifth embodiment test strip 1000 is shown that allows information to be encoded directly onto the test strip. Test strip 1000 may be formed with working electrode 1020, dose sufficiency working electrode 1024, working electrode sense trace 1030, counter electrode sense trace 1032, information trace 1034, and information trace 1036 formed as shown and coupled to measurement contact pads W, DW, WS and CS and information contact pads B1 and B2, respectively. In addition, counter electrode 1022 and dose sufficiency counter electrode 1026 are connected to counter electrode trace 1023 and dose sufficiency counter electrode trace 1027, respectively, which are in turn further connected to measurement contact pads C and DC, respectively. The information trace 1034 includes a resistive element 1038 and a trace 1027 connected to a dose sufficiency counter electrode. Information trace 1036 includes resistive element 1040 and is connected to counter electrode trace 1023. The contact pads provide conductive areas on the test strip 1000 to contact the electrical connector contacts of the test meter once the test strip 1000 is inserted into the test meter.

As shown in FIGS. 14 and 15, trace loops DC-B1 and C-B2 are formed between measurement pads DC and B1, and C and B2, respectively. As described above, the resistance of trace loops DC-B1 and C-B2 can be controlled during manufacturing by varying the width, thickness, length, or material of the trace loops. However, having a large number of different test strip mask configurations during manufacture in order to provide a large number of encoded words or states can be difficult and expensive. One way in which the total number of test strip mask configurations may be reduced is to use a single mask configuration having locations along the traces where resistive elements can be included and integrated into the traces. This approach can be extended to integrating multiple resistive elements into one or more traces. During manufacture, the resistance of a particular trace can be controlled by varying the resistance of one or more resistive elements included within the particular trace, thereby providing a simple and convenient way of controlling the trace or trace loop resistance.

As an illustrative example, test strip 1000 shown in FIG. 14 utilizes a film-type resistive element 1038 within information trace 1034. Thus, the total resistance in both information trace 1034 and trace loop B1-DC includes the resistance of resistive element 1038. Similarly, the total resistance within all of information trace 1036 and trace loop C-B2 includes the resistance of resistive element 1040. During manufacture, test strip 1000 may be initially formed using a test strip mask configuration having gaps in information traces 1034 and 1036. Later, resistive elements 1038 and 1034 are placed across the gaps in information traces 1034 and 1036, respectively.

Referring now to FIG. 15, a test strip 1000' illustrates an embodiment in which the DC-B1 trace loop resistance shown in FIG. 15 differs from the DC-B1 trace loop resistance shown in FIG. 14, while the C-B2 trace loop resistance shown in FIG. 15 is equal to the C-B2 trace loop resistance shown in FIG. 14. Test strip 1000 ' utilizes a basic overall mask configuration that is relatively similar to test strip 1000, with gaps initially formed in information traces 1034 and 1036 ' and with information trace 1036 ' being longer than information trace 1036. In contrast to test strip 1000, the conductive ink bridges the gaps within test strip 1000 ' to form resistive elements 1038 ' and 1040 '. For this example, it is assumed that the resistance of the conductive ink is smaller than that of the film-type resistive element shown in fig. 14 for a given length. The resistance of resistive element 1038' is less than the resistance of resistive element 1038, and thus, the resistance of trace 1034 shown in FIG. 15 is less than the resistance of trace 1034 shown in FIG. 14. However, the increased length of trace loop C-B2 and the increased length of resistive element 1040' result in the resistance of trace loop C-B2 shown in FIG. 15 being equal to the resistance of trace loop C-B2 shown in FIG. 14. Thus, the test meter is able to distinguish between test strip 1000 and test strip 1000' by measuring, for example, the resistance of trace 1034, the resistance of trace loop DC-B1, or the ratio of trace loop DC-B1 resistance and trace loop C-B2 resistance.

Resistive elements 1038, 1038 ', 1040 and 1040' may comprise different conductive materials as are well known in the art to modify trace resistance. These materials include conductive inks, screen printed thick film hybrid resistors, and standard fixed value thick or thin film resistors.

In general, the total number of possible states that can be encoded onto a test strip using the systems and methods shown in FIGS. 16-23 and described above is limited by the space available on the surface of the test strip or the materials that can be used to manipulate the trace or trace loop resistance; the ability to accurately control the resolution of conductive features on the test strip, such as trace or trace loop size, shape, and placement; and the ability to accurately measure the resistance value on the test strip. The enhanced ability to accurately control trace geometry reduces manufacturing-related variations in trace resistance and allows additional words or states to be encoded onto the test strip for a given test strip size and shape. Similarly, the enhanced ability to accurately control trace geometry allows for an increased number of traces and information contact pads to be placed on the test strip, thereby allowing additional words or states to be encoded onto the test strip for a given test strip size and shape.

It should be noted that the ability to precisely control trace geometry and increase trace and contact pad density achieved in the present invention by using a laser ablation process is a significant improvement over the prior art. The laser ablation process described hereinabove allows for resolution of test strip conductive features previously unattainable using prior techniques such as screen printing and photolithography. Thus, when a laser ablation process is used to form the conductive features, a relatively large amount of data can be encoded onto the test strip. For example, published european patent application EP 1024358 a1 discloses a system using up to 35 contact pads on a single test strip; however, the density of the features is so low as to force the inventor to contact only five of these contact pads at a time. Not only does this require much more test strip surface area than the present invention to form the same number of contact pads, but because the test meter cannot contact more than five contact pads at a time, the test meter cannot measure the resistance between each of the contact pads. The tight control over feature size enabled by the laser ablation process of the present invention allows the use of trace and contact pad densities never achieved in the prior art.

It should also be understood that the term trace loop is not intended to be limiting and does not imply a particular trace geometry, such as a circular path, and includes any portion along an electrical path that is capable of determining resistance.

It should also be understood that the test meter is capable of distinguishing the test strip characteristics of two or more test strips into characteristics that can be used to encode information onto the test strip.

All publications, prior applications, and other documents cited herein are hereby incorporated by reference in their entirety as if each had been individually incorporated by reference and fully set forth.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the description is to be considered as illustrative and not restrictive in character. Only the illustrated embodiment and certain other embodiments deemed helpful in explaining how to make or use the illustrated embodiment are shown. All changes and modifications that come within the spirit of the invention are desired to be protected.

Claims (1)

1. A system for measuring a concentration of an analyte of interest within a biological fluid, comprising:

a test meter;

a first test strip comprising:

a first measuring electrode connectable to the test meter,

a first trace loop having a first associated resistance, the first trace loop being connectable to the test meter, an

A second trace loop having a second associated resistance, the second trace loop being connectable to the test meter; and

wherein the test meter is adapted to:

at least two substantially non-zero resistance values are distinguished,

receiving the first test strip and providing the first test strip,

is connected to the first measurement electrode, the first trace loop, and the second trace loop, an

A first resistance ratio is obtained by comparing the first and second associated resistances.

2. The system of claim 1, wherein the test meter is adapted to measure the first and second correlated resistances.

3. The system of claim 1, wherein the first resistance ratio is configured to correlate to a predetermined value.

4. The system of claim 1, wherein the test meter is adapted to determine whether the first resistance ratio correlates to a predetermined value.

5. The system of claim 4, wherein the test meter is adapted to test the biological fluid for an analyte of interest when the first resistance ratio is related to the predetermined value.

6. The system of claim 4, wherein the test meter is adapted to inhibit testing of the biological fluid for the analyte of interest when the first resistance ratio correlates to the predetermined value.

7. The system of claim 4, wherein the test meter is adapted to record information associated with the first test strip when the first resistance ratio correlates to the predetermined value.

8. The system of claim 1, wherein the test meter is adapted to compare the first resistance ratio to at least two discrete, non-overlapping ranges, and wherein the first resistance ratio falls within a first one of the discrete ranges.

9. The system of claim 1, wherein the first trace loop comprises a first material and the second trace loop comprises a second material different from the first material.

10. The system of claim 1, wherein:

the first and second associated resistances are different;

the first trace loop comprises a first characteristic length, width, and thickness;

the second trace loop comprises a second characteristic length, width, and thickness; and

at least one of the first characteristic length, width, and thickness is different from a corresponding one of the second characteristic length, width, and thickness.

11. The system of claim 1, wherein the first and second associated resistances correlate to calibration information associated with the first test strip.

12. The system of claim 1, further comprising a first measurement electrode trace conductively connected to the first measurement electrode, wherein the first trace loop comprises at least a portion of the first measurement electrode trace.

13. The system of claim 1, wherein

A portion of the first trace loop comprises a material having a first resistive property; and

the remaining portion of the first trace loop comprises a different material having a second resistive property different from the first resistive property.

14. The system of claim 1, further comprising:

a second test strip comprising:

a second measuring electrode connectable to the test meter,

a third trace loop having a third associated resistance, said third trace loop being connectable to said test meter, an

A fourth trace loop having a fourth associated resistance, the fourth trace loop being connectable to the test meter; and

wherein the test meter is adapted to:

receiving the second test strip and providing the second test strip,

is connected to the second measurement electrode, the third trace loop, and the fourth trace loop, an

A second resistance ratio is obtained by comparing the resistances of the third and fourth correlations.

15. The system of claim 14, wherein the first and second resistance ratios are different.

16. The system of claim 14, wherein:

the test meter is adapted to determine whether the first resistance ratio is related to a predetermined value, an

The test meter is adapted to determine whether the second resistance ratio is related to a predetermined value.

17. The system of claim 16, wherein:

the test meter is adapted to test the biological fluid for an analyte of interest when the first resistance ratio is related to the predetermined value, an

The test meter is adapted to test the biological fluid for an analyte of interest when the second resistance ratio is related to the predetermined value.

18. The system of claim 16, wherein:

the test meter is adapted to inhibit testing of the biological fluid for the analyte of interest when the first resistance ratio is related to the predetermined value, and

the test meter is adapted to inhibit an analyte of interest of the test biological fluid when the second resistance ratio is related to the predetermined value.

19. The system of claim 16, wherein:

the test meter is adapted to record information associated with the first test strip when the first resistance ratio correlates to the predetermined value, an

The test meter is adapted to record information associated with the first test strip when the second resistance ratio correlates to the predetermined value.

20. The system of claim 14, wherein:

the test meter is adapted to compare the first resistance ratio with at least two discrete, non-overlapping ranges, and wherein the first resistance ratio belongs to a first one of the discrete ranges, and

the test meter is adapted to compare the second resistance ratio to at least two discrete, non-overlapping ranges, and wherein the second resistance ratio belongs to a second one of the discrete ranges.

21. The system of claim 14, wherein:

the first and second associated resistances correlate to calibration information associated with the first test strip, an

The third and fourth associated resistances correlate to calibration information associated with the second test strip.

22. The system of claim 14, wherein:

the resistances of the first and third associations are different;

the first trace loop comprises a first characteristic length, width, and thickness;

the third trace loop comprises a third characteristic length, width, and thickness; and

at least one of the first characteristic length, width, and thickness is different from a corresponding one of the third characteristic length, width, and thickness.

23. The system of claim 14, wherein:

the first test strip comprises:

a first mask configuration having a first gap within the first trace loop and a second gap within the second trace loop,

a first resistive element conductively connected to the first trace loop and bridging the first gap, an

A second resistive element conductively connected to the second trace loop and bridging the second gap;

the second test strip comprises:

a second mask configuration having a third gap within the third trace loop and a fourth gap within the fourth trace loop,

a third resistive element conductively connected to the third trace loop and bridging the third gap, an

A fourth resistive element conductively connected to the fourth trace loop and bridging the fourth gap; and

wherein the first mask configuration is substantially similar to the second mask configuration.

24. The system of claim 23, wherein the first resistive element has an associated resistance and the third resistive element has an associated resistance, and wherein the resistance associated with the first resistive element is different than the resistance associated with the third resistive element.

25. The system of claim 1, wherein the first and second sensors are disposed in a common housing,

wherein the first test strip includes a third trace loop having a third associated resistance, the third trace loop being connectable to the test meter, an

Wherein the test meter is adapted to be connected to the third trace loop and to obtain a second resistance ratio by comparing the first and third associated resistances.

26. The system of claim 25, wherein the test meter is adapted to determine whether the second resistance ratio correlates to a predetermined value.

27. The system of claim 1, comprising:

the first test strip has a first mask configuration, a first resistive element, and a second resistive element, the first mask configuration comprising:

the first trace loop has a first associated resistance and a first gap, and

the second trace loop has a second associated resistance and a second gap;

wherein the first resistive element is conductively connected to the first trace loop and bridges the first gap; and

wherein the second resistive element is conductively connected to the second trace loop and bridges the second gap;

a second test strip having a second mask configuration, a third resistive element, and a fourth resistive element, the second mask configuration being substantially similar to the first mask configuration, the second mask configuration comprising:

a second measuring electrode connectable to the test meter,

a third trace loop having a third associated resistance and a third gap, said third trace loop being connectable to said test meter, an

A fourth trace loop having a fourth associated resistance and a fourth gap, the fourth trace loop being connectable to the test meter;

wherein the third resistive element is conductively connected to the third trace loop and bridges the third gap; and

wherein the fourth resistive element is conductively connected to the fourth trace loop and bridges the fourth gap; and

wherein the test meter is adapted to:

is connected to the first and second measuring electrodes,

is connected to the first and second trace loops,

a first resistance ratio is obtained by comparing the first and second associated resistances,

is connected to the third and fourth trace loops, an

A second resistance ratio is obtained by comparing the resistances of the third and fourth correlations.

28. The system of claim 27, wherein the first and second resistance ratios are different.

29. The system of claim 27, wherein:

the test meter is adapted to determine whether the first resistance ratio correlates to a predetermined value when the test meter receives the first test strip, an

The test meter is adapted to determine whether the second resistance ratio correlates to a predetermined value when the test meter receives the second test strip.

30. The system of claim 29, wherein:

if the first resistance ratio correlates to the predetermined value, the test meter tests the biological fluid for an analyte of interest, and

the test meter tests the biological fluid for an analyte of interest if the second resistance ratio correlates to the predetermined value.

31. The system of claim 29, wherein:

if the first resistance ratio correlates to the predetermined value, the test meter inhibits testing of the biological fluid for the analyte of interest, and

the test meter inhibits testing the biological fluid for the analyte of interest if the second resistance ratio correlates to the predetermined value.

32. The system of claim 29, wherein:

if the first resistance ratio correlates to the predetermined value, the test meter records information associated with the first test strip, an

If the second resistance ratio correlates to the predetermined value, the test meter records information associated with the second test strip.

33. The system of claim 29, wherein:

when the test meter receives the first test strip, the test meter compares the first resistance ratio to at least two discrete, non-overlapping ranges, and

when the test meter receives the second test strip, the test meter compares the second resistance ratio to the at least two discrete, non-overlapping ranges.

34. The system of claim 29, wherein:

the first resistance ratio is related to calibration information associated with the first test strip, an

The second resistance ratio is related to calibration information associated with the second test strip.

35. The system of claim 29, wherein

The first mask construction further comprises a fifth trace loop having a fifth associated resistance and a fifth gap, the fifth trace loop being connectable to the test meter, wherein the fifth resistive element is conductively connected to the fifth trace loop and bridges the fifth gap;

wherein the test meter is adapted to be connected to the fifth trace loop and to obtain a third resistance ratio by comparing the first and fifth associated resistances.

36. The system of claim 35, wherein the test meter is adapted to determine whether the third resistance ratio correlates to a predetermined value when the test meter receives the first test strip.

37. A method for measuring the concentration of an analyte of interest in a biological fluid, for non-disease diagnostic purposes, comprising:

providing a test meter adapted to distinguish between two substantially non-zero resistance values;

providing a first test strip, the first test strip comprising:

a first measuring electrode connectable to the test meter,

a first trace loop having a first associated resistance, the first trace loop being connectable to a test meter, an

A second trace loop having a second associated resistance, the second trace loop being connectable to the test meter;

receiving a first test strip in a test meter;

communicatively connecting the first measurement electrode, the first trace loop, and the second trace loop with the test meter; and

a first resistance ratio is obtained by comparing the first and second associated resistances.

38. The method of claim 37, further comprising:

the resistances of the first and second correlations are measured.

39. The method of claim 37, further comprising:

selecting a predetermined resistance ratio; and

the ratio of the first associated resistance to the second associated resistance is configured to correlate to a predetermined resistance ratio value.

40. The method of claim 37, further comprising:

it is determined whether the first resistance ratio is related to a predetermined value.

41. The method of claim 40, further comprising:

the biological fluid is tested for an analyte of interest when the first resistance ratio is related to a predetermined value.

42. The method of claim 40, further comprising:

the analyte of interest of the test biological fluid is inhibited when the first resistance ratio correlates to a predetermined value.

43. The method of claim 40, further comprising:

information associated with the first test strip is recorded when the first resistance ratio correlates to a predetermined value.

44. The method of claim 37, further comprising:

comparing the first resistance ratio to at least two discrete, non-overlapping ranges, and wherein the first resistance ratio belongs to a first one of the discrete ranges.

45. The method of claim 37, wherein the first trace loop comprises a first material and the second trace loop comprises a second material different from the first material.

46. The method of claim 37, wherein:

the first and second associated resistances are different;

the first trace loop includes a first characteristic length, width, and thickness;

the second trace loop includes a second characteristic length, width, and thickness; and

at least one of the first characteristic length, width, and thickness is different from a corresponding one of the second characteristic length, width, and thickness.

47. The method of claim 37, wherein the first and second associated resistances correlate to calibration information associated with the first test strip.

48. The method of claim 37, wherein the first test strip further comprises a first measurement electrode trace conductively connected to the first measurement electrode, and wherein the first trace loop comprises at least a portion of the first measurement electrode trace.

49. The method of claim 37, wherein

A portion of the first trace loop comprises a material having a first resistive property; and

the remaining portion of the first trace loop includes a different material having a second resistive property different from the first resistive property.

50. The method of claim 37, further comprising:

providing a second test strip, the second test strip comprising:

a second measuring electrode connectable to the test meter,

a third trace loop having a third associated resistance, the third trace loop being connectable to the test meter, an

A fourth trace loop having a fourth associated resistance, the fourth trace loop being connectable to the test meter; and

receiving a second test strip in the test meter;

communicatively connecting the second measurement electrode, the third trace loop, and the fourth trace loop with the test meter; and

a second resistance ratio is obtained by comparing the resistances of the third and fourth correlations.

51. The method of claim 50, wherein the first and second resistance ratios are different.

52. The method of claim 50, further comprising:

determining whether the first resistance ratio is related to a predetermined value, an

Determining whether the second resistance ratio is related to a predetermined value.

53. The method of claim 52, wherein:

detecting an analyte of interest of the biological fluid when the first resistance ratio is related to a predetermined value, an

The biological fluid is tested for the analyte of interest when the second resistance ratio is related to a predetermined value.

54. The method of claim 52, wherein:

inhibiting the analyte of interest of the test biological fluid when the first resistance ratio correlates with a predetermined value, an

The analyte of interest of the test biological fluid is inhibited when the second resistance ratio correlates to a predetermined value.

55. The method of claim 52, wherein:

recording information associated with the first test strip when the first resistance ratio correlates to a predetermined value, an

Information associated with the first test strip is recorded when the second resistance ratio correlates to a predetermined value.

56. The method of claim 50, wherein:

comparing the first resistance ratio with at least two discrete, non-overlapping ranges, and wherein the first resistance ratio belongs to a first one of said discrete ranges, and

comparing the second resistance ratio to at least two discrete, non-overlapping ranges, and wherein the second resistance ratio belongs to a second one of the discrete ranges.

57. The method of claim 50, wherein:

the first associated resistance and the second associated resistance are related to calibration information associated with the first test strip, an

The third associated resistance and the fourth associated resistance are related to calibration information associated with the second test strip.

58. The method of claim 50, wherein:

the resistances of the first and third associations are different;

the first trace loop includes a first characteristic length, width, and thickness;

the third trace loop includes a third characteristic length, width, and thickness; and

at least one of the first characteristic length, width, and thickness is different from a corresponding one of the third characteristic length, width, and thickness.

59. The method of claim 50, wherein the first and second test strips further comprise a substantially similar mask configuration, wherein:

the first and second measure electrodes are substantially similar;

the first and third trace loops are substantially similar, each having a gap and a resistive element conductively bridging the gap; and

the second and fourth trace loops are substantially similar, each having a gap and a resistive element conductively bridging the gap.

60. The method of claim 59, wherein each resistive element has an associated resistance, and the resistance associated with the resistive element that conductively bridges the gap in the first trace loop is different than the resistance associated with the resistive element that conductively bridges the gap in the third trace loop.

61. The method of claim 37, wherein the first and second portions are selected from the group consisting of,

wherein said providing a first test strip comprises a test strip including a third trace loop having a third associated resistance, the third trace loop being connectable to a test meter; and

wherein the obtaining comprises obtaining a second resistance ratio by comparing the resistances of the first and third correlations.

62. The method of claim 61, further comprising:

determining whether the first resistance ratio is related to a predetermined value; and

it is determined whether the second resistance ratio is related to a predetermined value.

63. A method for encoding information readable by a test meter onto a test strip adapted for measuring the concentration of an analyte of interest in a biological fluid, the method for non-disease diagnostic purposes comprising:

selecting a first resistance ratio associated with a first word desired to be encoded onto the test strip;

forming a measurement electrode on a surface of the test strip substrate, wherein the measurement electrode is connectable to a test meter and the test meter is adapted to distinguish between at least two substantially non-zero resistance values; and

forming a first electrical trace and a second electrical trace on a surface of the test strip substrate, wherein the resistance of each of the first and second electrical traces is obtainable by the test meter, and wherein a ratio of the resistance of the first electrical trace and the resistance of the second electrical trace effectively matches the first resistance ratio.

64. The method of claim 63, further comprising:

selecting a second resistance ratio associated with a second word desired to be encoded onto the test strip, an

Forming a third electrical trace on the surface of the test strip substrate, wherein the resistance of the third electrical trace is available through the test meter, and wherein a ratio of the resistance of the first electrical trace and the resistance of the third electrical trace effectively matches the second resistance ratio.

65. The method of claim 64, wherein the first word is associated with a first discrete range of resistance values and the second word is associated with a second discrete range of resistance values, the second discrete range being different than the first discrete range.

66. The method of claim 63, wherein the forming the first and second electrical traces comprises controlling a width, a thickness, and a length of the first and second electrical traces to effectively match the first resistance ratio.

67. The method of claim 63, wherein the forming the first and second electrical traces comprises controlling a material composition of the first and second electrical traces to effectively match the first resistance value.

68. The method of claim 63, wherein the first resistance ratio is related to calibration information associated with the test strip.

69. The method of claim 63, wherein the first electrical trace comprises at least two different conductive materials.

70. The method of claim 63, wherein:

the first electrical trace includes a first gap and a first resistive element conductively bridging the first gap, an

The second electrical trace includes a second gap and a second resistive element conductively bridging the second gap.