HK1142679B - Biosensor calibration system - Google Patents

Description

Biosensor calibration system

Cross-reference to phase-contrast applications

This application is a continuing patent of U.S. non-provisional application No. 11/781,425 entitled "biosensor calibration system" filed on 23.7.2007, which is incorporated herein by reference in its entirety.

Technical Field

The present invention relates to a biosensor system, and more particularly, to a biosensor calibration system using one or more calibrated correlation equations.

Background

Biosensors provide for the analysis of biological fluids, such as whole blood, urine, or saliva. Typically, biosensors have a measuring device that analyzes a sample of the biological fluid placed on a sensor strip. The analysis determines a concentration of one or more analytes, such as alcohol, glucose, uric acid, lactate, cholesterol, or bilirubin, in a sample of the biological fluid. The sample of biological fluid may be collected directly, or a derivative of the biological fluid, such as an extract, dilution, filtrate or reconstituted sediment. The analysis can be used for diagnosis and treatment of physiological abnormalities. For example, a diabetic patient may use a biosensor to determine blood glucose levels in whole blood in order to adjust diet and/or medication.

Many biosensor systems provide calibration information to the measurement device prior to analysis. The measurement device may use the calibration information to adjust the analysis of the biological fluid in response to one or more parameters, such as the type of biological fluid, the particular analyte, and manufacturing variations of the sensor strip. The accuracy and/or precision of the analysis may be improved with the calibration information. Accuracy can be represented by the deviation of the analyte reading of the sensor system compared to a reference analyte reading, with a larger deviation value representing lower accuracy; and accuracy may be represented by the spread or variance between multiple measurements. If the calibration information is not properly read, the measurement device may not analyze at all or may make a false analysis of the biological fluid.

Biosensors may be designed for analyzing one or more analytes, and may use different volumes of biological fluid. Some biosensors can analyze a drop of whole blood, such as a volume of 0.25 to 15 microliters (μ L). Biosensors may be implemented using bench-top (bench-top), portable, and similar measurement devices. The portable measuring device may be hand-held and may perform qualitative and/or quantitative determination of one or more analytes in a sample. Examples of portable measurement systems include Ascensia Breeze, Inc. (Bayer HelthCare), of Bayer healthcare, Tarrytown, New YorkType and EliteA type meter; while an example of a bench-top measurement system includes an electrochemical workstation available from CH instruments of Austin, Texas.

Biosensors may analyze samples of biological fluids using optical and/or electrochemical methods. In some optical systems, analyte concentration is determined by measuring light that chemically reacts with a light-distinguishable substance, such as an analyte or a product formed by a redox reaction of a reactant or chemical indicator with the analyte. In other optical systems, the chemical indicator fluoresces or emits light in response to the redox reaction of the analyte when illuminated with the excitation beam. In either optical system, the biosensor measures light and correlates the light with the analyte concentration of the biological sample.

In an electrochemical biosensor, the analyte concentration is determined from an electrical signal generated by an oxidation/reduction or redox reaction of the analyte when an input signal is applied to a sample. An enzyme (enzyme) or the like may be added to the sample to enhance the redox reaction. The redox reaction generates an electrical output signal in response to the input signal. The input signal may be a current, a potential, or a combination of both. The output signal may be a current (e.g., generated by amperometry (amperometry) or voltammetry (voltmetry)), a potential (e.g., generated by potentiometry/amperometry (galvometry)), or an accumulated charge (e.g., generated by coulometry (coulometry)). In electrochemical methods, biosensors measure and correlate an electrical signal to the concentration of an analyte in a biological fluid.

Electrochemical biosensors usually comprise a measuring device which applies an input signal to an electrical conductor of a sensor strip via electrical contacts. The electrical conductor may be made of an electrically conductive material such as a solid metal, a metal paste, conductive carbon, a conductive carbon paste, a conductive polymer, or the like. The electrical conductors are typically connected to a working electrode, a counter electrode, a reference electrode, and/or other electrodes that extend to a sample cell (reservoir). One or more electrical conductors may also extend into the sample cell to provide functionality not provided by the electrodes. The measurement device may have processing capabilities to measure and correlate the output signal with the presence and/or concentration of one or more analytes in the biological fluid.

In many biosensors, the sensor strip can be used outside, inside or part of a living organism. When used outside a living organism, a sample of biological fluid is introduced into a sample cell in the sensor strip. The sensor strip may be placed in the measurement device for analysis before, after, or during introduction of the sample. When in a living organism or part of a living organism, the sensor strip may be continuously immersed in the sample, or the sample may be intermittently introduced to the sensor strip. The sensor strip may include a sample cell that may partially separate a volume of sample or house a sample. Similarly, the sample may flow continuously through the sensor strip or be interrupted for analysis.

The sensor strip may include reagents (agents) that can chemically react with analytes in a sample of biological fluid. The reagents may include ionic agents that promote redox reactions of the analyte and mediators or other substances that assist in the transfer of electrons between the analyte and the conductor. The ionic agent may be an oxidoreductase (oxidoreductase), such as an analyte-specific enzyme that catalyzes the oxidation of glucose in a whole blood sample. The reagent may comprise a binder that binds the enzyme and the mediator together.

The sensor strip may have one or more encoding patterns that provide calibration information to the measurement device. The calibration information may be identification information indicating the type of sensor strip, the analyte or biological fluid associated with the sensor strip, the manufacturing lot of the sensor strip, etc. The calibration information may indicate the correlation equation used, changes to the correlation equation, and the like. The correlation equation is a mathematical representation of the relationship between the electrical signal and the analyte in an electrochemical biosensor or a mathematical representation of the relationship between the light and the analyte in an optical biosensor. The correlation equation can be used to control the electrical signal or light used to determine the analyte concentration. The correlation equation may also be implemented as a Program Number Assignment (PNA) table, another lookup table, etc. for the slope and intercept of the correlation equation. The measurement device uses the calibration information to adjust the analysis of the biological fluid.

Many measurement devices take calibration information from the encoding pattern, either electrically or optically. Some encoding patterns may be read only electrically or only optically. Other encoding patterns may be read electrically and optically in combination.

Electrically encoded patterns typically have one or more circuits with multiple contact points or pads. The measuring device may have one or more conductors connected to each contact point on the coding pattern of the sensor strip. Typically, the measuring device applies an electrical signal to one or more contact points on the encoding pattern through one or more conductors. The measuring device measures output signals from one or more other contact points. The measurement device may determine the calibration information based on the presence or absence of a signal output from the contact point on the encoding pattern. Examples of sensor strips with electrically encoded patterns can be found in U.S. Pat. Nos. 4,714,874, 5,856,195, 6,599,406, and 6,814,844.

In some electrically encoded patterns, the measurement device determines calibration information based on whether different contact points exist. The contact points may be removed from other portions of the circuit, never formed or broken. If the measuring device measures an output signal from the location of the contact point, the measuring device assumes that the contact point is present. If the measuring device does not measure the output signal, the measuring device assumes that the contact point is not present.

In other electrical coding patterns, the measurement device determines calibration information from the resistance of the electrical output signal from the contact point. Typically, the amount of conductive material associated with each contact point is different, and thus the resistance is different. The contact points may have additional or a small amount of conductive material layers. The length or thickness of the connections between the contact points and the circuitry may also vary. The contact points may be removed from other portions of the circuit, never formed or broken.

The optically encoded pattern typically has a series of lines and/or an array of pads. The measuring device determines the presence of the lines or pads by scanning the code pattern to determine calibration information from the code pattern.

Errors may occur with the use of these conventional electrical and optical coding patterns. The sensor strip may acquire or release material during manufacturing, shipping, handling, etc. The added or missing material may cause the measurement device to obtain erroneous calibration information from the encoding pattern that may prevent the completion or cause of erroneous analysis of the biological fluid.

In electrically encoded patterns, added or lost material may alter or interfere with the calibration information. The added material may cover the contact points, the locations of the contact points, or the connections between the contact points. If the added material is conductive, the measurement device may determine that a contact point is present when it is not present, or may measure an incorrect resistance from the contact point. If the added material is non-conductive, the measurement device may determine that a contact point is not present when a contact point is present, or measure an incorrect resistance from the contact point. Further, the lost material may be a portion of the contact points or a portion of the connection between the contact points. Thus, the missing material may cause the measurement device to determine that a contact point is not present when the contact point is present, or may cause the measurement device to measure an incorrect resistance.

In an optically encoded pattern, added or lost material may alter or interfere with the calibration information. The added material may cover or block the lines or pads. The added material may cover or block gaps or spaces between the lines or pads. The lost material may be part of the line or pad. The added or missing material causes the measuring device to scan the changed lines or pads.

Accordingly, there is a continuing need for improved biosensors, particularly biosensors that provide increasingly accurate and/or precise analyte concentration measurements. The systems, devices, and methods of the present invention overcome at least one disadvantage associated with coding patterns used on sensor strips in biosensors.

Disclosure of Invention

The present invention provides a biosensor system that calibrates an analyte analysis to determine an analyte concentration in a biological fluid. The biosensor system senses a circuit pattern on the sensor strip. The circuit pattern provides calibration information that the biosensor system can use to calibrate one or more correlation equations for analyte analysis. The analyte concentration is determined using one or more calibrated correlation equations.

A biosensor system may have a measurement device and a sensor strip. The measurement device may have a processor connected to the pattern read device. The sensor strip comprises a counter electrode and a working electrode, the sensor strip may be provided with a coding pattern having more than two circuits, wherein each circuit forms a circuit pattern and each circuit pattern comprises a unique set of contact areas, each circuit pattern being electrically isolated from the counter electrode or the working electrode. The measurement device and sensor strip may perform analyte analysis. The analyte analysis may have one or more correlation equations. The pattern reading device may sense at least two circuit patterns on the encoding pattern of the sensor strip, wherein the pattern reading device determines a unique pattern of electrical contact points corresponding to the unique set of contact areas of each circuit pattern, and wherein the unique pattern of electrical contact points identifies the circuit pattern of each circuit. The processor may determine calibration information in response to the circuit pattern. The processor may calibrate at least one correlation equation in response to the calibration information. The processor may determine the analyte concentration in response to one or more calibrated correlation equations.

Another biosensor may have a measuring device and a sensor strip. The measurement device may have a processor connected to the pattern read device. The pattern read device may have an array of electrical contacts. The sensor strip may have a coding pattern. The encoding pattern may have at least two circuits, and each circuit may have at least one contact area. The contact area may be in electrical communication with an electrical contact. The measurement device and sensor strip may perform analyte analysis. The analyte analysis may have one or more correlation equations. The electrical contacts may selectively apply a test signal to the contact areas on the encoding pattern. The pattern read device may sense at least two circuit patterns on the encoding pattern. The processor may determine calibration information in response to the circuit pattern. The processor may calibrate one or more correlation equations in response to the calibration information. The processor may determine the analyte concentration in response to one or more calibrated correlation equations.

In a method for calibrating analysis of an analyte in a biological fluid, a sensor strip is provided that includes a counter electrode and a working electrode, the sensor strip further having an encoding pattern with at least two circuits, wherein each circuit forms a circuit pattern and each circuit pattern includes a unique set of contact areas, each circuit pattern being electrically isolated from the counter electrode or the working electrode. At least two circuit patterns on the encoding pattern are sensed. Determining calibration information in response to the circuit patterns, wherein a unique pattern of electrical contact points corresponding to the unique set of contact areas of each circuit pattern is determined, and wherein the unique pattern of electrical contact points identifies the circuit pattern of each circuit. One or more correlation equations are calibrated in response to the calibration information. The analyte concentration is determined in response to one or more calibrated correlation equations.

Drawings

The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

FIG. 1 shows a schematic view of a biosensor.

FIG. 2A shows an array of electrical contacts in electrical communication with the encoding pattern.

FIG. 2B shows the encoding pattern of FIG. 2A prior to the encoding pattern being divided into separate circuits.

FIG. 2C shows the encoding pattern of FIG. 2A after the encoding pattern has been divided into separate circuits.

FIG. 3A shows an undivided encoding pattern having contact areas X in electrical communication with an array of electrical contacts.

FIG. 3B shows a unique circuit pattern that forms part of the encoding pattern of FIG. 3A.

Fig. 4A shows the numbering sequence of the contact areas on the coding pattern in fig. 3A to 3B.

Fig. 4B shows the circuit patterns and respective digital representations of the circuit of fig. 3B.

Fig. 5 shows a pattern reading apparatus.

FIG. 6A shows another undivided encoding pattern having contact areas X in electrical communication with an array of electrical contacts.

FIG. 6B shows a unique circuit pattern that can form the encoding pattern in FIG. 6A.

Fig. 7A shows the numbering sequence of the contact areas on the coding pattern in fig. 6A to 6B.

Fig. 7B shows the circuit pattern and respective digital representations of the circuit in fig. 6B.

FIG. 8A shows another undivided encoding pattern.

FIG. 8B represents a unique circuit pattern that may be arranged on the encoding pattern in FIG. 8A.

Fig. 9A shows the numbering sequence of the contact areas of the coding pattern in fig. 8A to 8B.

Fig. 9B shows the circuit pattern and respective digital representations of the circuit in fig. 8B.

Fig. 10A shows a numbering sequence of the contact areas on another coding pattern.

Fig. 10B shows the circuit patterns of the circuit and the respective digital representations.

FIG. 11A shows another undivided encoding pattern.

FIG. 11B shows unique circuit patterns for the first circuit, the second circuit, and the isolation circuit of the encoding pattern of FIG. 11A.

Fig. 12A shows the numbering sequence of the contact areas on the coding pattern of fig. 11A to 11B.

Fig. 12B shows another view of the circuit pattern described with reference to fig. 11B.

Fig. 13 shows an encoding pattern divided into a first circuit, a second circuit, and an isolation circuit.

FIG. 14A shows another undivided encoding pattern having contact areas X in electrical communication with an array of electrical contacts.

FIG. 14B shows a unique circuit pattern that may be present on the encoding pattern of FIG. 14A for both multi-contact circuits and single-contact circuits.

Fig. 15A shows various triangular coding patterns.

FIG. 15B shows various rhomboid-shaped coding patterns.

Fig. 15C shows various pentagonal encoding patterns.

Fig. 15D shows various circular coding patterns.

Fig. 16A shows an undivided encoding pattern having an irregular shape.

FIG. 16B shows unique circuit patterns for the first circuit, the second circuit, and the third circuit of the encoding pattern of FIG. 16A.

FIG. 17 illustrates one method for calibrating a biosensor.

FIG. 18 shows another method for calibrating a biosensor.

Detailed Description

The biosensor system calibrates an analyte analysis to determine an analyte concentration in a sample of the biological fluid. The biosensor system has a measuring device which applies a test signal to the coding pattern on the sensor strip. The measuring device senses a circuit pattern on the encoding pattern in response to the test signal. The circuit pattern provides calibration information that the biosensor system uses to calibrate optical and/or electrochemical analysis of an analyte in a biological fluid. The measurement device uses the calibration information to calibrate one or more correlation equations used in the analysis of the analyte. The measurement device determines the analyte concentration using one or more calibrated correlation equations.

Fig. 1 shows a schematic diagram of a biosensor 100, the biosensor 100 determining an analyte concentration in a sample of a biological fluid. Biosensor 100 includes a measurement device 102 and a sensor strip 104. The measurement device 102 may be implemented as a desktop device, a portable or handheld device, or the like. The measurement device 102 and the sensor strip 104 may perform an analyte analysis, which may be an electrochemical analysis, an optical analysis, a combination thereof, or the like. The biosensor 100 may determine analyte concentrations including alcohol, glucose, uric acid, lactate, cholesterol, bilirubin, and the like in biological samples such as whole blood and urine. Although one particular configuration is illustrated, the biosensor 100 may have other configurations, including configurations with additional components.

Sensor strip 104 has a base 106 that forms a sample cell 108 and a conduit 110 with an opening 112. The sample cell 108 and the conduit 110 are covered by a lid having a vent hole. The sample cell 108 defines a partially enclosed volume (cap-gap). The sample cell 108 may contain a composition that helps retain the fluid sample, such as a water-swellable polymer or a porous polymer matrix. Reagents may be deposited in sample cell 108 and/or conduit 110. The reagent composition may comprise one or more enzymes, binders, mediators, etc. The reagent may comprise a chemical indicator for the optical system. The sensor bars 104 may have other configurations.

The sensor strip 104 may have a sample interface 114. In an electrochemical system, the sample interface 114 has conductors that connect to at least two electrodes, such as a working electrode and a counter electrode. The electrodes may be arranged on the surface of the base 106 forming the sample cell 108. The sample interface 114 may have other electrodes and/or conductors.

The sensor strip 104 preferably includes a coding pattern 130 on the base 106. The encoding pattern 130 has at least two circuits, each forming a circuit pattern. The coding pattern 130 may be a separate label affixed to the sensor strip 104 or elsewhere on the biosensor 100, or the coding pattern 130 may be integrally formed with the sensor strip 104. The encoding pattern 130 may be formed from the same material used to form the conductors, electrodes, etc. on the sensor strip 104. Other encoding patterns may be used. Each circuit pattern includes a unique or selected combination of electrical or physical interconnect locations on the encoding pattern. The circuit pattern may include all or part of the locations available on the coding pattern.

The encoding pattern 130 may be positioned on the top, bottom, sides, or anywhere else of the sensor strip 104. The coding pattern 130 may be located on separate strips. For example, the encoding pattern 130 may be located on a calibration strip for use with a set of measurement strips. The calibration strip may be another strip or may be part of or attached to a package containing the set of measurement strips. Furthermore, the calibration strip as well as the measurement strip may each have a coding pattern. For example, the calibration strip may have a first encoding pattern that provides more general calibration information. Each measurement bar may also have a second encoding pattern that provides more specific calibration information. The encoding pattern 130 may be applied directly to the surface of the sensor strip 104. The encoding pattern 130 may be formed using the same materials and similar techniques as used to create the conductive measurement lines of the sample cell 108, the conductors or electrodes on the sample interface 114, other components of the sensor strip 104, and the like. Other encoding patterns may be used.

Measurement device 102 includes circuitry 116, and circuitry 116 is coupled to sensor interface 118, display 120, and pattern read device 132. The sensor interface 118 and the pattern read device 132 may be the same component. Circuitry 116 may include a processor 122, processor 122 coupled to a signal generator 124, an optional temperature sensor 126, and a storage medium 128. The circuitry 116 may have other configurations including configurations with additional components. Sensor strip 104 may be configured for insertion into measuring device 102 from only one direction. Sensor strip 104 may be configured for insertion into measurement device 102 in an orientation such that encoding pattern 130 is disposed in electrical or optical communication with pattern read device 132, and sample interface 114 is disposed in electrical and/or optical communication with sensor interface 118.

The processor 122 provides control signals to the pattern read device 132. The control signal may be an electrical signal such as a current, a potential, or the like. In the optical system, the control signal operates the first light source and the first detector in the pattern read device 132. Additional light sources may be used as well as light detectors or imaging devices with pattern recognition. The optical system senses light reflected from the surface of the encoding pattern 130 or senses light passing through the encoding pattern 130. In an electrical system, the control signals may operate electrical contacts in the pattern read device 132 that are in electrical communication with contact areas on the encoding pattern 130. Electrical communication includes signal transfer between electrical contacts in the pattern read device 132 and contact areas in the encoding pattern 130. The electrical communication may be performed wirelessly, for example by capacitive coupling, or by physical contact.

The signal generator 124 provides an electrical input signal to the sensor interface 118 in response to the processor 122. In the optical system, the electrical input signal operates a second light source and a second detector in the sensor interface 118. In the electrical system, an electrical input signal is communicated to the sample interface 114 through the sensor interface 118 to apply the electrical input signal to the sample cell 108, and thus to the sample of biological fluid.

The electrical input signal may be a potential or a current and may be constant, variable, or a combination thereof, such as applying an alternating signal with a direct signal offset. The electrical input signal may be applied in a single pulse, or in multiple pulses, sequences, or cycles. The signal generator 124 may also record the output signal from the sensor interface 118 as a generator-recorder.

The storage medium 128 may be a magnetic, optical, or semiconductor memory, other computer readable storage device, or the like. The storage medium 128 may be a fixed storage device or a removable storage device such as a memory card.

The processor 122 may perform analyte analysis and data processing using computer readable software code and data stored in the storage medium 128. The processor 122 may use the calibration information from the encoding pattern 130 to calibrate the analyte analysis and data processing.

Processor 122 may provide control signals to pattern read device 132 in response to the presence of sensor strip 104 at sensor interface 118, the presence of sensor interface 118 at pattern read device 132, the application of a sample to sensor strip 104, user input, and the like. The processor 122 may begin analyzing the analyte after acquiring the calibration information from the encoding pattern 130. To begin analysis, the processor 122 may direct the signal generator 124 to provide an electrical input signal to the sensor interface 118. The processor 122 may receive the sample temperature from the temperature sensor 126 (if installed).

The processor 122 receives calibration information from the pattern read device 132. The calibration information is responsive to the circuit pattern of the encoding pattern 130. Processor 122 also receives output signals from sensor interface 118. An output signal is generated in response to a redox reaction of an analyte in the sample. The output signal may be generated using an optical system, an electrochemical system, or the like. Processor 122 may determine the concentration of the analyte in the sample from the one or more signals using a correlation equation. The correlation equation may be calibrated by the processor 122 in response to calibration information from the encoding pattern 130. The results of the analyte analysis are output to the display 120 and may be stored in the storage medium 128.

The correlation equation relates the analyte concentration to the output signal and may be expressed graphically, mathematically, a combination thereof, and the like. The correlation equation may be represented by a Program Number Assignment (PNA) table, another look-up table, or the like, stored in the storage medium 128. Instructions related to implementation of the analysis and use of the calibration information may be provided by computer readable software code stored in the storage medium 128. The code may be object code or any other code that describes or controls the functionality described herein. The data from the analyte analysis may be affected by one or more data processes including the determination of decay rate, K constant, slope, intercept, and/or sample temperature in the processor 122.

The sensor interface 118 is in electrical and/or optical communication with the sample interface 114. Electrical communication includes the transfer of input and/or output signals between contacts in sensor interface 118 and conductors in sample interface 114. The electrical communication may be wireless or by physical contact. The sensor interface 118 transmits the electrical input signal from the signal generator 124 to the connections in the sample interface 114 through the contact points. The sensor interface 118 also transmits output signals from the sample to the processor 122 and/or the signal generator 124 via the contact points. Optical communication includes the transfer of light between an optical inlet in the sample interface 114 and a detector in the sensor interface 118. Optical communication also includes the transfer of light between an optical inlet in the sample interface 114 and a light source in the sensor interface 118.

Similarly, the pattern read device 132 is in electrical and/or optical communication with the encoding pattern 130. Electrical communication includes the transfer of signals between the pattern read device 132 and the encoding pattern 130. The electrical communication may be wireless or by physical contact. Optical communication includes the transfer of light from a light source in the pattern read device 132 to the encoding pattern 130. The optical communication also includes the transfer of light from the pattern read device 130 to the detector in the encoding pattern 132.

The display 120 may be analog or digital. The display 120 may be a liquid crystal display, a light emitting diode, or a vacuum fluorescent display suitable for displaying numerical readings.

In use, a liquid sample for analysis is transferred to the sample cell 108 by introducing liquid into the opening 112. The liquid sample flows through the conduit 110 and into the sample cell 108 while venting the previously contained air. The liquid sample chemically reacts with reagents deposited in the tubing 110 and/or the sample cell 108.

The processor 122 provides control signals to the pattern read device 132. In the optical system, the pattern read device 132 operates the light source and the detector in response to the control signal. In an electrical system, the pattern read device 132 operates an array of electrical contacts connected to the encoding pattern 130 in response to a control signal. The pattern read device 132 senses the circuit pattern on the encoding pattern 130 and provides calibration information in response to the circuit pattern. The processor 122 receives calibration information from the encoding pattern 130.

The processor 122 also directs the signal generator 124 to provide an input signal to the sensor interface 118. In an optical system, the sensor interface 118 operates the detector as well as the light source in response to input signals. In an electrochemical system, sensor interface 118 provides an input signal to a sample through sample interface 114. Processor 122 receives an output signal generated in response to a redox reaction of an analyte in the sample. Processor 122 determines the analyte concentration of the sample using one or more correlation equations. The processor 122 may calibrate the correlation equations in response to the calibration information from the encoding pattern 130. The determined analyte concentration may be displayed and/or stored for future reference.

The measurement device 102 and sensor strip 104 may perform electrochemical analysis, optical analysis, combinations thereof, and the like, to determine the concentration of one or more analytes in a sample of biological fluid. Optical analysis uses the reaction of a chemical indicator with an analyte to determine the analyte concentration in a biological fluid. Electrochemical analysis uses the oxidation/reduction or redox reaction of an analyte to determine the analyte concentration in a biological fluid.

Optical analysis typically measures the amount of light absorbed or produced by the reaction of a chemical indicator with an analyte. Enzymes may be included with the chemical indicators to enhance reaction mechanics. Light from the optical system may be converted into an electrical signal such as a current or potential.

In light absorption optical analysis, chemical indicators produce reaction products that absorb light. An incident excitation beam from a light source is directed towards the sample. The incident beam is reflected off the sample or transmitted through the sample to a detector. The detector collects and measures the attenuated incident beam. The amount of light attenuated by the reaction product is indicative of the analyte concentration in the sample.

In light-generating optical assays, chemical indicators fluoresce or emit light in response to an analyte during a redox reaction. The detector collects and measures the light generated. The amount of light generated by the chemical indicator is indicative of the analyte concentration in the sample.

During electrochemical analysis, an excitation signal is applied to a sample of the biological fluid. The excitation signal may be a potential or a current, and may be constant, variable, or a combination thereof. The excitation signal may be applied in a single pulse, or in multiple pulses, sequences, or cycles. When an excitation signal is applied to the sample, the analyte undergoes a redox reaction. Enzymes or the like may be used to enhance the redox reaction of the analyte. The mediator may be used to maintain the oxidation state of the enzyme. The redox reaction produces an output signal that can be measured continuously or periodically during transient and/or steady state output. Various electrochemical methods can be used, such as amperometry, coulometry, voltammetry, gated amperometry (gated amperometry), gated voltammetry (gated voltimometry), and the like.

Optical analysis and electrochemical analysis use correlation equations to determine the analyte concentration of a biological fluid. The correlation equation is a mathematical representation of the relationship between analyte concentration and an output signal such as light, current, or potential. The correlation equation may be linear, nearly linear or curvilinear and may be expressed by a second order polynomial. From the correlation equation, the analyte concentration can be calculated for a particular output signal. The biosensor may store one or more correlation equations in memory for use during optical or electrochemical analysis. Different correlation equations may be required, particularly when different sensor bars are used or operating parameters such as sample temperature are changed. Correlation equations may be implemented to manipulate the output signals for determining the analyte concentration. The correlation equation may also be implemented as a Program Number Assignment (PNA) table, another look-up table, etc. for the slope and intercept of the correlation equation for comparison to the output signal to determine the analyte concentration.

In FIG. 1, measurement device 102 calibrates the correlation equation in response to calibration information from sensor strip 104. The pattern read device 132 senses the circuit pattern of the encoding pattern 130 and provides a pattern signal responsive to the circuit pattern to the processor 122. The pattern signal may be an analog or digital electrical signal, or the like. The processor 122 converts the pattern signals into calibration information for the sensor bars 104. Processor 122 calibrates one or more correlation equations in response to the calibration information.

The calibration information may be any information used to calibrate the correlation equation. Calibration includes adjusting or modifying concentration values or other results of the correlation equation. The calibration includes selecting one or more correlation equations. For example, the calibration information may be identification information indicating the type of sensor strip, the analyte or biological fluid associated with the sensor strip, the manufacturing lot of the sensor strip, the expiration date of the sensor strip, and the like. Processor 122 may select to use one or more correlation equations in response to the identification information. The calibration also includes modifying one or more correlation equations. For example, the calibration information may provide or direct the use of an addition or subtraction to the slope and/or pitch of the correlation equation. The calibration also includes providing one or more correlation equations. For example, the calibration information may include or direct the use of slopes and pitches for the correlation equations. Other calibration information may be used.

To obtain the calibration information, the pattern read device 132 senses the circuit patterns of at least two circuits formed by the encoding pattern 130. The pattern read device 132 may sense the circuit pattern optically or electrically. The encoding pattern 130 may be a conductive material applied to the sensor strip 104, the sensor strip 104 being located in a position accessible to the pattern read device 132. The conductive material may be carbon, silver, aluminum, palladium, or the like. The encoding pattern 130 may be a non-conductive material or other material that forms sufficient contrast with the optically-sensed background material.

The encoding pattern 130 formed of the conductive material may be divided into two or more separate circuits. The conductive material may be segmented using laser ablation, scribing, photolithography, and the like. By altering the dicing path that separates the conductive material into circuits, unique combinations of circuit patterns (interconnect contact areas) can be formed. Separate circuits may also be formed during the creation of the encoding pattern 130 on the sensor strip 104. The conductive material may be rectangular or square, and may be other shapes such as triangular, circular, elliptical, combinations of the shapes, and the like. The circuit may be formed by single or multiple orthogonal cuts, or may be formed by non-orthogonal cuts or a combination of orthogonal and non-orthogonal cuts. Orthogonal cuts are not necessary, but avoiding diagonal cuts may improve alignment of the circuitry with the pattern read device 132.

Each circuit on the encoding pattern 130 may have one or more contact areas in electrical communication with the pattern read device 132. When each circuit has at least two contact areas, detection of faulty contacts, open circuit conditions, and other errors from extraneous or missing material may be improved. The detection of these errors may also be improved when the coding pattern 130 has two circuits comprising all contact areas. The same number of circuits may be used on different strips to further improve the detection of these errors. When an error occurs, measurement device 102 may notify the user and may reject and/or eject sensor strip 104. The error check may include determining whether the total number of circuit patterns matches the number of circuits on the encoding pattern 130. If the measuring device 102 is unable to interpret all of the contact areas on the code pattern 130 and all of the circuit patterns, the measuring device 102 may also notify the user and may reject and/or eject the sensor strip 104.

Fig. 2A-2C show various views of the encoding pattern 230 on the sensor strip 204. FIG. 2A shows an array of electrical contacts 238 in electrical communication with the encoding pattern 230. Fig. 2B shows the encoding pattern 230 before being divided into separate circuits. The encoding pattern 230 has contact areas a-F that are in electrical communication with an array of electrical contacts 238. Fig. 2C shows the encoding pattern 230 after division into separate circuits. The encoding pattern 230 has been divided into a first circuit 234 and a second circuit 236. The first circuit 234 includes contact areas A, C, E and F in electrical communication with electrical contacts A, C, E and F of the array 238. The second circuit 236 includes contact areas B and D in electrical communication with electrical contacts B and D of the array 238. Although a particular configuration is shown, the sensor bars 204, encoding pattern 230, and array 238 may have other configurations, which may include configurations with additional components and encoding patterns that are split into more than two circuits.

The array of electrical contacts 238 may be part of a pattern reading device that uses the electrical contacts to sense the circuit pattern of the encoding pattern 230. The pattern read device may apply test signals to the first circuit 234 and the second circuit 236 through the array of electrical contacts 238 in response to the control signals. The test signal may be an electrical signal such as a current, a potential, or the like. For example, the test signal may be limited to a current of less than about 50 microamperes (μ A). The test signal may be a current limited to a range of about 1 microampere to about 48 microamperes. The test signal may be a current limited to a range of about 2 microamperes to about 15 microamperes. The test signal may be a current limited to a range of about 2 microamperes to about 10 microamperes. The test signal may be a current limited in a range of about 4 microamps up to about 8 microamps. The current may be selected to provide short circuit protection. The current may be selected to accommodate the resistance of the material from which the circuit pattern is generated. Other currents or potentials may be used.

Referring to fig. 1, the pattern read device selectively applies test signals to sense the circuit patterns of circuit 234 and circuit 236. The pattern read device drives selected electrical contacts in the array of electrical contacts 238 to ground while applying test signals to other electrical contacts in the array of electrical contacts 238. The test signal may be current limited and may have a different potential than other electrical contacts in the array of electrical contacts 238. Other test signals may be used. "ground" includes zero or near zero potential or current, etc. The pattern read device may individually drive one or more electrical contacts in the array of electrical contacts 238 to ground. The pattern read device applies the test signal in one or more steps or iterations, with the electrical contacts driven to ground being changed in each step. After one or more steps, the pattern read device can determine the unique set of contact points that are in contact with a particular circuit by determining which other contact points are forced to a low potential or to ground when a given contact point is driven to a low potential or to ground. Thus, the pattern read device can determine a unique pattern of electrical contacts of the array of electrical contacts 238 associated with each of the electrical circuits 234 and the electrical circuits 236. The unique pattern of electrical contacts identifies the circuit pattern of each circuit 234 and circuit 236. The circuit patterns of the circuit 234 and the circuit 236 may be used to provide calibration information for optical or electrochemical analysis of analytes in biological fluids.

Alternatively, the pattern read device may selectively apply a test signal that is opposite to the test signal described above. When opposing test signals are used, the pattern read device may individually drive one or more electrical contacts to a potential other than ground while driving the remaining electrical contacts to ground. The current limiting impedance may be used to drive the electrical contacts to ground. A current source may be used to drive the electrical contacts to another potential. When reading, only those electrical contacts connected to the driven electrical contact are at the driving potential, while the remaining electrical contacts are grounded. The pattern read device may selectively apply other test signals.

Fig. 3A to 3B show circuit patterns that can be formed by dividing the code pattern 230 on the sensor strip 204 into a circuit 234 and a circuit 236. FIG. 3A shows an undivided encoding pattern 230 having contact areas X that are in electrical communication with the array of electrical contacts 238 in FIG. 2A. Although the contact areas X are arranged in 2 rows and 3 columns, other arrangements of contact areas and electrical contact arrays 238 may be used, including arrangements with fewer or additional contact areas and electrical contacts. The encoding pattern 230 may be divided into other circuit patterns.

Fig. 3B shows circuit patterns that the circuit 234 and the circuit 236 may have. There are 6 contact areas arranged in 2 rows and 3 columns. Although not necessary, the cutting pattern is constrained to orthogonal cuts. In the case of orthogonal cutting, the two circuits created can be completed in one continuous cut. Thus, when at least two electrical contacts from the array of electrical contacts 238 are in electrical communication with each circuit, the circuit 234 and the circuit 236 may form 9 unique circuit patterns. The circuit patterns have various shapes, positions, and orientations on the encoding pattern 230. Each circuit pattern includes a unique set of contact areas and, thus, a unique set of electrical contacts in the array of electrical contacts 238. Calibration information may be determined from the electrical contacts associated with a particular circuit pattern.

Fig. 4A to 4B show circuit patterns and respective digital representations of the circuits described with reference to fig. 3A to 3B. FIG. 4A shows a numbering sequence of contact areas on the encoding pattern 230 that correspond to electrical contacts in the array of electrical contacts 238. The contact areas and corresponding electrical contacts are numbered 1 through 6. Fig. 4B shows circuit patterns and respective digital representations of the circuit described with reference to fig. 3B. In each circuit pattern, the contact area of the first circuit 234 and the corresponding electrical contact may be identified as "0". In each circuit pattern, the contact area of the second circuit 236 and the corresponding electrical contact may be identified as a "1". The labels "0" and "1" may be arbitrarily selected to identify the contact areas and corresponding electrical contacts belonging to a particular circuit. The labels are interchangeable. Other labels or number designations may be used and may result in different numerical representations.

The specific labels (0 or 1) for each contact area and corresponding electrical contact are listed sequentially according to the numbering sequence discussed with reference to FIG. 4A. Although the numbering system is numerically reduced from 6 to 1, the numbering sequence may also be numerically increased from 1 to 6. Other numbering sequences may be used. The sequence of labels "0" and "1" provides a unique digital representation of each circuit pattern. Other digital representations of the circuit pattern may be used.

The digital representation of the circuit pattern can be used to provide calibration information for analysis of an analyte in a biological fluid. By means of the pattern signal, the pattern read device may provide a digital representation of the circuit pattern to a processor in the measurement device. The processor converts the digital representation into calibration information.

FIG. 5 shows a pattern read device 532 for sensing the circuit pattern of the encoding pattern 530 on the sensor strip 504. The encoding pattern 530 has a first circuit 534 and a second circuit 536. The pattern read device 532 has a decoder 550 and a code reader 552, each of which is connected to a plurality of test circuits 554. Duplicate circuitry of pattern read device 532 is omitted for clarity. Decoder 550 may be a digital decoder or the like. The decoder 550 may be an "n" select 1 digital decoder, where n is 6. Other digital decoders may be used. The code reader 552 may be a digital input port or the like. Each test circuit 554 is connected to a separate electrical contact a-F in the array of electrical contacts 538. The electrical contacts A-F may be in electrical communication with contact areas on the first circuit 534 and the second circuit 536 of the encoding pattern 530. Although a particular circuit pattern is shown, the first circuit 534 and the second circuit 536 can have other circuit patterns including circuit patterns that use different contact areas and corresponding electrical contacts. Although a particular configuration for the pattern read device is shown, other configurations may be used, including configurations with additional components. Other pattern reading devices may be used.

In use, the processor in the measurement device sends a control signal to the decoder 550 in the pattern read device 532. The processor also activates a pull-up voltage in each test circuit 554. The pull-up voltage causes each test circuit 554 to apply a test signal or current to electrical contacts a-F in the array of electrical contacts 538. The test signal may be limited to a current of less than about 50 microamps. The test signal may be a current limited in a range of about 1 microampere up to about 48 microamperes. The test signal may be a current limited in a range of about 2 microamps up to about 15 microamps. The test signal may be a current limited in a range of about 2 microamps up to about 10 microamps. The test signal may be a current limited in a range of about 4 microamps up to about 8 microamps. Other currents may be used. The processor also activates the code reader 552 to sense the test signal applied to each electrical contact in the array 538.

The pattern read device 532 selectively applies test signals to determine the circuit pattern of the circuit 534 and the circuit 536 on the encoding pattern 530. Test circuit 554 applies a test signal to electrical contacts A-F in array 538. The code reader 552 senses the test signal. To sense the circuit pattern, the pattern read device 532 individually drives one or more electrical contacts in the array of electrical contacts 538 to ground while applying pull-up voltage test signals to other electrical contacts in the array of electrical contacts 538. The decoder 550 applies an operation signal to one or more test circuits 554 in response to the control signal. The operating signals drive the respective test circuit and the corresponding electrical contacts to ground.

When the electrical contacts A-F of the array 538 are in electrical communication with the circuits 534 and 536 on the encoding pattern 530, the circuits 534 and 536 establish electrical connections therebetween. When a particular electrical contact on a circuit is driven to ground, the test signals for other electrical contacts on the circuit are lowered or driven to ground. The code reader 552 uses the reduced or grounded test signal to identify the electrical contacts associated with the particular electrical contact driven to ground. The electrical contacts associated with the grounded electrical contacts may be used to identify the circuit pattern. The code reader 552 generates a pattern signal that can identify the circuit pattern on the encoding pattern 530. The pattern signal may be a digital representation of the circuit pattern. The processor receives the pattern signal from the code reader 552. The pattern signal may contain calibration information. The processor may convert the pattern signal into calibration information or use the pattern signal to locate the calibration information in the storage medium. The processor calibrates one or more correlation equations using the calibration information, the one or more correlation equations being used to determine an analyte concentration in the biological fluid.

The pattern read device applies the test signal in one or more steps or iterations. Different electrical contacts are driven to ground in each step. After one or more steps, the pattern read device may determine a unique set of electrical contacts corresponding to a particular circuit by determining which electrical contacts have reduced or grounded test signals in response to electrical contacts driven to ground. Thus, the pattern read device can determine a unique pattern of electrical contacts for the array of electrical contacts 538 associated with each circuit 534 and 536 on the encoding pattern 530. The unique combination of electrical contacts identifies the circuit pattern of each circuit 534 and 536. The circuit patterns of circuits 534 and 536 may be used to provide calibration information for optical or electrochemical analysis of analytes in a biological fluid. Although a particular combination of electrical contacts is shown for identifying the circuit pattern, other sets of electrical contacts may be used to represent other circuit patterns for circuits 534 and 536.

For example, electrical contacts A, C, E and F correspond to the circuit pattern of the first circuit 534. Electrical contacts B and D correspond to the circuit pattern of the second circuit 536. To sense which electrical contacts correspond to a particular circuit pattern, the pattern read device 532 applies test signals to the electrical contacts and individually drives one or more electrical contacts to ground in one or more steps or iterations. The pattern read device may determine the electrical contacts corresponding to a particular circuit by determining which electrical contacts have a reduced or grounded test signal in response to an electrical contact driven to ground. The circuit pattern may be identified after the first step. One or more additional steps may be performed to confirm the results. The examples are presented for clarity and illustration, not to limit the invention.

In a first step, a first test signal from a first test circuit to electrical contact A is driven to ground while test signals are applied to other electrical contacts. When electrical contact A is grounded, the test signal for electrical contacts C, E and F is lowered or grounded because these electrical contacts correspond to first circuit 534. However, because electrical contacts B and D correspond to second circuit 536 and are not electrically connected to first circuit 534, the test signals for these electrical contacts are not lowered or grounded and remain substantially unchanged.

In a second step, a second test signal from a second test circuit to electrical contact E is driven to ground while test signals are applied to the other electrical contacts. When electrical contact E is grounded, the test signal for electrical contacts A, C and F is lowered or grounded because these electrical contacts correspond to first circuit 534. However, because electrical contacts B and D correspond to second circuit 536, the test signals for these electrical contacts are not lowered or grounded and remain substantially unchanged.

In a third step, a third test signal from a third test circuit to electrical contact B is driven to ground while test signals are applied to the other electrical contacts. When electrical contact B is grounded, the test signal for that electrical contact is lowered or grounded because electrical contact D corresponds to the second circuit 536. However, because electrical contacts A, C, E and F correspond to first circuit 534, the test signals for these electrical contacts are not lowered or grounded and remain substantially unchanged. By reviewing the results of the previous read steps and grounding pins that have not been accounted for in the circuits identified in the previous read steps, the number of read steps can be reduced or minimized.

Fig. 6 to 10 show various circuit patterns in which the encoding pattern is divided into two circuits. The encoding pattern may be partitioned into more and/or other circuits. Although the contact areas and corresponding electrical contacts in the array have a particular configuration, other configurations of contact areas and electrical contacts may also be used, including configurations with fewer or additional components. The maximum number of contact areas may be limited by the size of the sensor bars and other design considerations. The circuit patterns have various shapes, positions and orientations on the coding pattern. Other circuit patterns may be used. Each circuit pattern includes a unique set of contact areas and, thus, a unique set of electrical contacts in the array. Calibration information may be determined from the electrical contacts associated with a particular circuit pattern. Each contact area may have "0" and "1" labels, which may be arbitrarily selected to identify the contact area and corresponding electrical contact that belong to a particular circuit. The labels are interchangeable. Other labels or number designations may be used and result in different numerical representations. The sequence of labels "0" and "1" may provide a unique digital representation for each circuit pattern. Other digital representations of the circuit pattern may be used. The digital representation of the circuit pattern can be used to provide calibration information for analysis of an analyte in a biological fluid.

Fig. 6A-6B illustrate various circuit patterns that divide the encoding pattern 630 disposed on the sensor strip 604 into circuits 634 and circuits 636. FIG. 6A shows an undivided encoding pattern 630 with contact areas X in electrical communication with an array of electrical contacts. The contact areas X are arranged in 2 rows and 4 columns. Fig. 6B shows circuit patterns that the circuit 634 and the circuit 636 may have. Because the array has 2 rows and 4 columns, circuit 634 and circuit 636 can form 20 unique circuit patterns when at least two electrical contacts from the array are in electrical communication with each circuit. Because only orthogonal cuts are used, the illustrated circuit pattern is constrained. Additional circuit pattern interconnects may be formed if non-orthogonal cuts or a combination of orthogonal and non-orthogonal cuts are used, and if more than two circuits are created.

Fig. 7A-7B show circuit patterns and respective digital representations of the circuits described with reference to fig. 6A-6B. FIG. 7A shows a numbering sequence of contact areas on the encoding pattern 630, which also corresponds to electrical contacts in the array. The contact areas and the corresponding electrical contacts are numbered 1 to 8. Fig. 7B shows circuit patterns and respective digital representations of the circuit described with reference to fig. 6B. The contact areas and corresponding electrical contacts of the first circuit 634 and the second circuit 636 may be identified as "0" or "1," respectively, in each circuit pattern. The specific labels (0 or 1) for each contact area and corresponding electrical contact are listed sequentially according to the numbering sequence discussed with reference to FIG. 7A. The numbering system may decrease numerically from 8 to 1, or may increase numerically from 1 to 8. Other numbering sequences may be used. The sequence of labels "0" and "1" may provide a unique digital representation of the circuit pattern. The digital representation may be specified assuming that the circuit including bit 8 always presents a "0". The inverse of this code can also be used and the code can be keyed in to additional bit positions.

Fig. 8A to 8B show various circuit patterns for dividing another encoding pattern 830 on the sensor strip 804 into circuits 834 and 836. FIG. 8A shows an undivided encoding pattern 830 having contact areas X that are in electrical communication with an array of electrical contacts. The contact areas X are arranged in 3 rows and 3 columns. Fig. 8B shows circuit patterns that the circuits 834 and 836 may have. Because the array has 3 rows and 3 columns, the circuit 834 and the circuit 836 can form 44 unique circuit patterns when at least two electrical contacts in the array are in electrical communication with each circuit. The circuit pattern is a circuit pattern constrained by orthogonal cuts. If this constraint is not imposed, additional circuit pattern interconnections may be formed.

Fig. 9A to 9B show circuit patterns and respective digital representations of the circuits described with reference to fig. 8A to 8B. FIG. 9A shows a numbering sequence of the contact areas on the encoding pattern 830, which also corresponds to the electrical contacts in the array. The contact areas and the corresponding electrical contacts are numbered 1 to 9. Fig. 9B shows circuit patterns and respective digital representations of the circuit described with reference to fig. 8B. The contact areas and corresponding electrical contacts of the first 834 and second 836 circuits may be identified as "0" or "1", respectively, in each circuit pattern. The specific labels (0 or 1) for each contact area and corresponding electrical contact are listed in order according to the numbering sequence discussed with reference to FIG. 9A. The numbering system may decrease numerically from 9 to 1, or may increase numerically from 1 to 9. Other numbering sequences may be used. The sequence of labels "0" and "1" may provide a unique digital representation of each circuit pattern. The digital representation may be specified assuming that the circuit including bit 9 always presents a "0". The inverse of this code can also be used and the code can be keyed in to additional bit positions.

Fig. 10A to 10B show various circuit patterns for dividing another encoding pattern 1030 on the sensor strip into a circuit 1034 and a circuit 1036. FIG. 10A shows a numbering sequence of contact areas on the encoding pattern 1030, which also corresponds to electrical contacts in the array. The contact areas and corresponding electrical contacts are numbered 1 to 4. The contact areas are arranged in 2 rows and 2 columns. The circuit pattern is a circuit pattern constrained by orthogonal cuts. If this constraint is not imposed, additional circuit pattern interconnects may be formed.

Fig. 10B shows a circuit 1034 and a circuit pattern that circuit 1036 may have. Because the array has 2 rows and 2 columns, the first circuit 1034 and the second circuit 1036 can form 2 unique circuit patterns when at least two electrical contacts from the array are in electrical communication with each circuit. The contact areas and corresponding electrical contacts of the first and second circuits 1034, 1036 may be identified as "0" or "1," respectively, in each circuit pattern. The specific labels (0 or 1) for each contact area and corresponding electrical contact are listed sequentially according to the numbering sequence discussed with reference to FIG. 10A. The numbering system may decrease numerically from 4 to 1, or may increase numerically from 1 to 4. Other numbering sequences may be used. The sequence of labels "0" and "1" may provide a unique digital representation of the circuit pattern. The digital representation may be specified assuming that the circuit including bit 4 always presents a "0". The inverse of this code can also be used and the code can be keyed in to additional bit positions.

The coding pattern may be partitioned into more than two circuits. Each encoding pattern on different sensor bars may be partitioned to have the same number of circuits, or may be partitioned to have a different number of circuits. When the encoding pattern has more than two circuits, one or more of the circuits may be isolated circuits. The isolation circuit may have only one contact area that is in electrical communication with only one electrical contact in the array. Other isolation circuits may be used. The isolated circuit may increase the number of unique circuit patterns that may be used to provide calibration information for analysis of an analyte in a biological fluid. When the number of isolation circuits is a fixed number, a contact fault may be detected by verifying whether the detected number of isolation circuits matches a specified fixed number of isolation circuit contact points. Unique circuit patterns may be formed when at least one circuit includes multiple contact locations.

11A-11B illustrate circuit patterns on the sensor bar 1104 that divide the encoding pattern 1130 into first circuits 1134, second circuits 1136, and isolation circuits 1140. FIG. 11A shows an undivided encoding pattern 1130 having contact areas X in electrical communication with an array of electrical contacts. Although the contact areas X are arranged in 2 rows and 3 columns, other arrangements of contact areas and arrays of electrical contacts may be used.

FIG. 11B shows unique circuit patterns that the first circuit 1134, the second circuit 1136, and the isolation circuit 1140 may have. When at least two electrical contacts are in electrical communication with each of the first circuit 1134 and the second circuit 1136, and when one electrical contact is in electrical communication with the isolated circuit 1140, the first circuit 1134, the second circuit 1136, and the isolated circuit 1140 may form 16 unique circuit patterns. The circuit pattern may have various shapes, positions, and orientations. The circuit pattern of each of the first circuit 1134 and the second circuit 1136 includes a unique set of contact areas, and thus contains a unique set of electrical contacts. The circuit pattern of the isolation circuit 1140 includes specific contact areas and, thus, contains specific electrical contacts. The calibration information may be determined from the electrical contacts associated with the circuit pattern.

The multiple circuits created by the pattern on the sensor strip allow for inherent error checking of the encoded information. Error checking may be obtained by enforcing rules regarding the total number of circuits and the total number of isolated circuits. By enforcing the rules, the measurement device can detect failure patterns or readings, and thus can reject sensor bars before reporting false test results or after detecting a fault. To allow for error detection (particularly erroneous contacts or shorts), the number of isolated contact points may be a predetermined fixed number. Thus, if more or less than a predetermined number of isolated contact points are detected, a contact fault or short circuit must have occurred and the decoded pattern should be treated as invalid. The total number of circuits (multiple contacts and single contact) may likewise be a predetermined fixed number. Similarly, if more or less than a predetermined number of circuits are detected, a failure must have occurred and the decoded pattern should be treated as invalid.

Fig. 12A to 12B show other views of the circuit pattern described with reference to fig. 11A to 11B. FIG. 12A shows a numbering sequence of the contact areas on the encoding pattern 1130, which corresponds to electrical contacts. The contact areas and corresponding electrical contacts are numbered 1 to 6. Fig. 12B shows another view of the circuit pattern described with reference to fig. 11B. The contact areas of the first circuit 1134 and the corresponding electrical contacts may be identified as "0" in each circuit pattern. The contact areas of the second circuit 1136 and the corresponding electrical contacts may be identified as "1" in each circuit pattern. The contact areas of the isolation circuits 1140 and the corresponding electrical contacts may be identified as "X" in each circuit pattern. The tags (0, 1 and X) can be used to identify the contact areas and corresponding electrical contacts belonging to a particular circuit. The labels may be interchanged. Other labels may be used. The specific labels for each contact region and corresponding electrical contact are listed in order according to the numbering sequence discussed with reference to fig. 12A. Other numbering sequences may be used. The sequence of tags (0, 1, and X) may provide a unique digital representation of each circuit pattern. The digital representation of the circuit pattern can be used to provide calibration information for analysis of an analyte in a biological fluid. The digital representation may be specified assuming that the circuit containing bit 6 always presents a "0" unless bit 6 is an isolated contact. If bit 6 is an isolated contact, the circuit containing bit 5 always presents a "0". The inverse of this code can also be used and the code can be keyed to other bit positions.

FIG. 13B shows the encoding pattern 1330 divided into a first circuit 1334, a second circuit 1336, and an isolation circuit 1340. The contact areas of the first circuit 1334 and the second circuit 1336 are not contiguous and are connected using a plurality of conductive traces that provide electrical connections between non-contiguous locations on the encoding pattern 1330. The contact area of first circuit 1334 is identified as "0" and is connected by first conductive trace 1342. The contact area of second circuit 1336 is identified as "1" and is connected by a second conductive trace 1344 and a diagonal conductive trace 1346. In the circuit pattern, the contact area of the isolation circuit 1340 is identified as "X". The non-contiguous contact areas of first electrical circuit 1334 and second electrical circuit 1336 may increase the number of unique circuit patterns that may be used to provide calibration information for analysis of analytes in biological fluids.

14A-14B illustrate various circuit patterns on the sensor bars 1404 that divide the encoding pattern 1430 into isolated or single-contact circuits 1440 and multi-contact circuits 1442. FIG. 14A shows an undivided encoding pattern 1430 with contact areas X in electrical communication with an array of electrical contacts. Although the contact areas X are arranged in 2 rows and 2 columns, other arrangements of contact areas and arrays of electrical contacts may be used.

Fig. 14B shows unique circuit patterns that single-contact circuitry 1440 and multi-contact circuitry 1442 can have. When three electrical contacts are in electrical communication with multiple-contact circuitry 1442, and when one electrical contact is in electrical communication with single-contact circuitry 1440, the single-contact circuitry 1440 and the multiple-contact circuitry 1442 can form 4 unique circuit patterns. The circuit pattern may have various shapes, positions, and orientations. The circuit pattern of each single contact point circuit 1440 and the multiple contact point circuits 1442 includes a unique set of contact areas, and thus, a unique set of electrical contacts. The calibration information may be determined from the electrical contacts associated with the circuit pattern.

To provide error detection (particularly faulty contacts or shorts), if more or less than one single contact point circuit is detected, a contact fault or short must occur and the decoded pattern can be treated as invalid. Similarly, if more or less than two circuits are detected, a failure must have occurred and the decoded pattern should be treated as invalid.

Further, when at least one circuit involves multiple contacts, a unique circuit pattern can be formed even if the remaining circuits are isolated or single-contact circuits. The total number of contacts and the configuration of the electrical contacts may be selected to provide a better or optimized balance of multi-contact circuits and single-contact circuits. When only four electrical contacts are used, a three-contact circuit and a single-contact circuit can verify that there are two circuits and only one isolated contact, so error checking can be better maintained.

Fig. 15A to 15D show various encoding patterns having non-rectangular patterns and contact point arrays. Fig. 15A shows various triangular code patterns 1560 to 1568. FIG. 15B shows various rhomboid-shaped code patterns 1570-1578. Fig. 15C shows various hexagonal coding patterns 1580 to 1588. Fig. 15D shows various circular encoding patterns 1590 to 1598. The coding pattern is divided into two, three or four circuit patterns. Some circuit patterns have more than two contact points. Other circuit patterns are isolated or have a single contact point. Because the measurement device takes at least two contact points to measure continuity, the measurement device does not necessarily sense an isolated or single contact point circuit pattern directly. The encoding rules may be selected for a particular encoding pattern to specify the number of isolated circuit patterns allowed. Other non-rectangular patterns and contact point arrays may be used.

Fig. 16A to 16B show circuit patterns on the sensor strip 1604 that divide the coding pattern 1630 having an irregular shape into the first circuit 1634, the second circuit 1636, and the third circuit 1640. FIG. 16A shows an undivided encoding pattern 1630 with contact areas X in electrical communication with an array of electrical contacts. Fig. 16B shows unique circuit patterns that the first circuit 1634, the second circuit 1636, and the third circuit 1640 may have. Irregular shapes may be used if space for sensor contact must be avoided. When three circuit patterns are used, one circuit pattern may be an isolated or single-contact circuit. Other irregular shapes may be used. Other configurations of contact areas and arrays of electrical contacts may be used.

FIG. 17 shows a method for calibrating an analysis of an analyte in a biological fluid. At 1702, a sample of the biological fluid is detected when the sample is available for analysis. At 1704, a test signal is applied to the encoding pattern. At 1706, the circuit pattern on the encoding pattern is sensed. At 1708, calibration information is determined in response to the circuit pattern. In 1710, one or more correlation equations are calibrated in response to the calibration information. In 1712, the sample is analyzed for the analyte. At 1714, an analyte concentration of the biological fluid is determined using one or more calibrated correlation equations.

At 1702, the biosensor detects when a sample of the biological fluid is available for analysis. The biosensor can sense when the sensor strip is placed in the measurement device. The biosensor can sense when electrical contacts in the measuring device are connected to electrical conductors in the sensor strip. When the sample is connected to the electrodes, the biosensor may apply one or more signals to the working electrode, the counter electrode, and/or other electrodes for detection. When a sample is available for analysis, the biosensor may use other methods and devices to detect the sample.

At 1704, the biosensor applies a test signal from a measurement device to an encoding pattern on a sensor strip, sensor strip package, or the like. The test signal may be generated optically or electrically. As previously described, the biosensor selectively applies a test signal to the encoding pattern. The biosensor may apply the test signal in one or more steps or iteratively.

In 1706, the biosensor senses a circuit pattern of at least two circuits on the code strip. As previously described, the circuit pattern may be sensed optically or electrically. The pattern signal may be used to identify a circuit pattern on the encoding pattern.

At 1708, the biosensor determines calibration information in response to the circuit pattern. The calibration information may be any information used to adjust the correlation equations for electrochemical and/or optical analysis. The calibration information may be identification information that indicates the type of sensor strip, the analyte or biological fluid associated with the sensor strip, the manufacturing lot of the sensor strip, etc. The calibration information may be added or subtracted from the slope and/or pitch of the correlation equation. The calibration information may include or direct the use of the slope and/or pitch of the correlation equation. Other calibration information may be used. The calibration information may be a reference parameter and an adjustment value stored in a memory device of the biosensor. The processor may select the stored reference parameter and adjustment value in response to a pattern or other signal indicative of a circuit pattern on the encoding pattern.

In 1710, the biosensor calibrates one or more correlation equations in response to the calibration information. Correlation equations can be used to determine analyte concentrations in optical and/or electrochemical assays. The correlation equation is a mathematical representation of the relationship between analyte concentration and an output signal such as light, current or potential as previously described. Calibration includes adjusting or modifying concentration values or other results of the correlation equation. Calibration includes selecting one or more correlation equations in response to identifying information indicative of the type of sensor strip, the analyte or biological fluid associated with the sensor strip, the manufacturing lot of the sensor strip, the expiration date of the sensor strip, and the like. Calibration may include modifying one or more correlation equations by adding or subtracting the slope and/or pitch of the correlation equations. The calibration may include providing one or more correlation equations.

In 1712, the biosensor analyzes the analyte in the sample using electrochemical analysis, optical analysis, combinations thereof, and the like. In electrochemical assays, the analyte undergoes a redox reaction when an excitation signal is applied to the sample. The redox reaction produces an output signal that can be measured and correlated to the analyte concentration. Various electrochemical methods may be used, such as amperometry, coulometry, voltammetry, gated amperometry, gated voltammetry, and the like, as previously described. Optical analysis measures the amount of light absorbed or produced by the reaction of the chemical indicator with the analyte. The amount of light can be measured and correlated to the analyte concentration. The optical analysis may be light absorption or light generation as previously described.

In 1714, the biosensor determines an analyte concentration in the sample of the biological fluid. The biosensor may use one or more correlation equations to determine the analyte concentration of the sample. The biosensor may use the calibrated analyte value or other results to determine the analyte concentration of the sample.

FIG. 18 shows another method for calibrating the analysis of an analyte in a biological fluid. In 1802, a measurement device detects the presence of a sensor strip in a biosensor. At 1804, the measurement device may apply a test signal to the encoding pattern. At 1806, the measurement device senses the circuit pattern on the encoding pattern. At 1808, the measurement device determines calibration information in response to the circuit pattern. In 1810, the measurement device detects a sample of the biological fluid when the sample is available for analysis. In 1812, the measurement device calibrates one or more correlation equations in response to the calibration information. In 1814, the measurement device analyzes the analyte in the sample. In 1816, the measurement device determines the analyte concentration of the biological fluid using one or more calibrated correlation equations.

In 1802, the measuring device detects when a sensor strip is present. The measuring device can sense when the sensor strip is placed in the biosensor. The measuring device can sense when electrical contacts in the measuring device are connected with electrical conductors and/or coding patterns in the sensor strip. When a sensor strip is present, the measurement device may apply one or more signals to the working electrode, the counter electrode, and/or other electrodes for detection. When a sensor strip is present, the measuring device may apply one or more signals to the encoding pattern for detection. When a sensor strip is present in a biosensor, the measurement device may use other methods and devices to detect.

At 1804, the measurement device applies a test signal to an encoding pattern on a sensor strip, sensor strip package, or the like. The test signal may be generated optically or electrically. As previously described, the measurement device selectively applies test signals to the encoding pattern. The measuring device may apply the test signal in one or more steps or iteratively.

At 1806, the measuring device senses circuit patterns of at least two circuits on the code strip. As previously described, the circuit pattern may be sensed optically or electrically. The circuit pattern on the coding pattern can be identified with the pattern signal.

At 1808, the measurement device determines calibration information in response to the circuit pattern. As previously described, the calibration information may be any information used to adjust the correlation equations for electrochemical and/or optical analysis. In response to a pattern or other signal indicative of a circuit pattern on the encoding pattern, the measurement device may select the stored reference parameter and the adjustment value.

In 1810, the measurement device detects when a sample of the biological fluid is available for analysis. The measuring device may sense (mechanically, electrically, etc.) when the conductors in the sensor strip are in contact with the sample. When the sample is connected to the electrodes, the measurement device may apply one or more signals to the working electrode and/or other electrodes for detection. While samples are available for analysis, biosensors may use other methods and devices for detection.

In 1812, the measurement device calibrates one or more correlation equations in response to the calibration information. As previously mentioned, the correlation equation can be used to determine analyte concentration in optical and/or electrochemical assays.

In 1814, the measurement device analyzes the analyte in the sample using electrochemical analysis, optical analysis, combinations thereof, and the like. In electrochemical analysis, the measurement device may use one or more electrochemical processes as previously described. The measurement device measures an output signal from a redox reaction of the analyte and correlates the output signal with an analyte concentration. In optical analysis, the measuring device measures the amount of light absorbed or produced by the reaction of the chemical indicator with the analyte as previously described. The measuring device measures the amount of light and correlates the amount of light with the analyte concentration.

In 1816, the measurement device determines the analyte concentration in the sample of biological fluid. The measurement device may use one or more calibrated correlation equations to determine the analyte concentration of the sample. The measurement device may use the calibrated analyte value or other results to determine the analyte concentration of the sample.

The biosensor system may be operated with a sensor strip designed for a single analysis of the concentration of an analyte in a biological fluid. The biosensor system also allows more different calibration information to be used. Calibration may be implemented digitally, thereby rendering analyte analysis more tolerant of impedance differences and other impedance variations between sensor strip and encoding pattern fabrication. The biosensor may also have more robust error detection of faults because all electrical contacts in the pattern reading device must be in electrical or optical communication with corresponding contact areas of the circuitry on the encoding pattern for accurate and precise sensing of the circuit pattern. By enforcing rules regarding the total number of circuits and the total number of isolated circuits, the multiple circuits created by the pattern on the sensor strip allow for inherent error checking of the encoded information. When not all of the electrical contacts in the pattern read device are in electrical or optical communication with corresponding contact areas of the electrical circuits on the code pattern, the biosensor may notify the user and may reject and/or eject the sensor strip. False detection can reduce or eliminate misinterpretation of circuit patterns and selection of incorrect calibration information, thereby avoiding biased or incorrect analysis of analyte concentrations. The detection of the valid calibration pattern and the reading can be used to indicate that the sensor is properly inserted into the measurement device.

While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that other embodiments and implementations are possible within the scope of the invention.

Claims (21)

1. A biosensor system for determining an analyte concentration in a biological fluid, the biosensor system comprising:

a measurement device having a processor connected to the pattern read device;

a sensor strip comprising a counter electrode and a working electrode, the sensor strip further having an encoding pattern having at least two circuits, wherein each circuit forms a circuit pattern and each circuit pattern comprises a unique set of contact areas, each circuit pattern being electrically isolated from the counter electrode or the working electrode;

wherein the measurement device and the sensor strip perform an analyte analysis, wherein the analyte analysis has at least one correlation equation;

wherein the pattern read device senses at least two circuit patterns on the encoding pattern;

wherein the pattern read device determines a unique pattern of electrical contact points corresponding to the unique set of contact areas for each circuit pattern, and wherein the unique pattern of electrical contact points identifies the circuit pattern for each circuit;

wherein the processor determines calibration information in response to the circuit pattern;

wherein the processor calibrates at least one correlation equation in response to the calibration information; and

wherein the processor determines the analyte concentration in response to at least one calibrated correlation equation.

2. The biosensor system of claim 1, where the pattern read device selectively applies a test signal to the encoding pattern.

3. The biosensor system of claim 2, where the pattern read device applies at least one other test signal at a pull-up voltage.

4. The biosensor system of claim 2, wherein the pattern read device comprises a plurality of test circuits, wherein a first test circuit drives a first test signal to ground during a first step, and wherein a second test circuit drives a second test signal to ground during a second step.

5. The biosensor system of claim 1, where the pattern read device has an array of electrical contacts, where each circuit has at least two contact areas, the contact areas in electrical communication with the electrical contacts.

6. The biosensor system of claim 1, comprising at least one multi-contact circuit and at least one single-contact circuit.

7. The biosensor system of claim 2, where the test signal is less than about 50 microamps.

8. The biosensor system of claim 1, where the pattern read device generates a pattern signal in response to the circuit pattern.

9. The biosensor system of claim 1, where the contact areas on the encoding pattern are arranged in at least two rows and at least two columns.

10. The biosensor system of claim 1, comprising an encoding pattern having a first circuit, a second circuit, and at least one isolation circuit, wherein the first circuit and the second circuit each have at least two contact areas, and wherein the at least one isolation circuit has one contact area.

11. The biosensor system of claim 1, where the processor checks for errors in the calibration information.

12. The biosensor system of claim 1, where the pattern read device has an array of electrical contacts, where each of the at least two circuits has at least one contact area, and where the contact areas are in electrical communication with the electrical contacts.

13. A method for calibrating an analyte analysis in a biological fluid, the method comprising:

providing a sensor strip comprising a counter electrode and a working electrode, the sensor strip further having an encoding pattern having at least two circuits, wherein each circuit forms a circuit pattern and each circuit pattern comprises a unique set of contact areas, each circuit pattern being electrically isolated from the counter electrode or the working electrode;

sensing at least two circuit patterns on the encoding pattern;

determining calibration information in response to the circuit patterns, wherein a unique pattern of electrical contact points corresponding to the unique set of contact areas of each circuit pattern is determined, and wherein the unique pattern of electrical contact points identifies the circuit pattern of each circuit;

calibrating at least one correlation equation in response to the calibration information; and

the analyte concentration is determined in response to at least one calibrated correlation equation.

14. The method of claim 13, further comprising selectively applying a test signal to the encoding pattern.

15. The method of claim 14, wherein the test signal is less than about 50 microamps.

16. The method of claim 15, further comprising:

applying a test signal to the encoding pattern; and

at least one test signal is driven to ground.

17. The method of claim 15, further comprising:

driving a first test signal to ground during a first step; and

the second test signal is driven to ground during the second step.

18. The method of claim 13, further comprising generating a pattern signal responsive to the circuit pattern.

19. The method of claim 13, wherein each circuit pattern has at least two contact areas.

20. The method of claim 13, further comprising arranging the contact areas on the coding pattern in at least two rows and at least two columns.

21. The method of claim 13, further comprising checking for errors in the calibration information.