Biosensor coding system

A biosensor system determines an analyte concentration using one or more calibrated correlation equations for an optical and/or electrochemical analysis of a biological fluid. The biosensor system may be implemented using a measurement device and a sensor strip. The measurement device applies test signals to a sequential conductive pattern on a sensor strip. The measurement device selectively and sequentially connects test contacts with conductive and non-conductive areas on the sequential conductive pattern, which generates code signals in response to the test signals. The measurement device uses the code signals to calibrate one or more of the correlation equations. The measurement device uses the calibrated correlation equations to determine the analyte concentration.

BACKGROUND

Biosensors provide an analysis of a biological fluid, such as whole blood, urine, or saliva. Typically, biosensors have a measurement device that analyzes a sample of the biological fluid placed in a sensor strip. The analysis determines the 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 directly collected or may be a derivative of a biological fluid, such as an extract, a dilution, a filtrate, or a reconstituted precipitate. The analysis is useful in the diagnosis and treatment of physiological abnormalities. For example, a diabetic individual may use a biosensor to determine the glucose level in whole blood for adjustments to diet and/or medication.

Many biosensor systems provide calibration information to the measurement device prior to the 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(s), and the manufacturing variations of the sensor strip. The accuracy and/or precision of the analysis may be improved with the calibration information. Accuracy may be expressed in terms of bias of the sensor system's analyte reading in comparison to a reference analyte reading, with larger bias values representing less accuracy, while precision may be expressed in terms of the spread or variance among multiple measurements. If the calibration information is not read properly, the measurement device may not complete the analysis or may make a wrong analysis of the biological fluid.

Biosensors may be designed to analyze one or more analytes and may use different volumes of biological fluids. Some biosensors may analyze a single drop of whole blood, such as from 0.25-15 microliters (μL) in volume. Biosensors may be implemented using bench-top, portable, and like measurement devices. Portable measurement devices may be hand-held and allow for the identification and/or quantification of one or more analytes in a sample. Examples of portable measurement systems include the Ascensia Breeze® and Elite® meters of Bayer HealthCare in Tarrytown, N.Y., while examples of bench-top measurement systems include the Electrochemical Workstation available from CH Instruments in Austin, Tex.

Biosensors may use optical and/or electrochemical methods to analyze the sample of the biological fluid. In some optical systems, the analyte concentration is determined by measuring light that has interacted with a light-identifiable species, such as the analyte or a reaction or product formed from a chemical indicator reacting with the analyte redox reaction. In other optical systems, a chemical indicator fluoresces or emits light in response to the analyte redox reaction when illuminated by an excitation beam. In either optical system, the biosensor measures and correlates the light with the analyte concentration of the biological sample.

In electrochemical biosensors, 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 the sample. An enzyme or similar species 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, potential, or combination thereof. The output signal may be a current (as generated by amperometry or voltammetry), a potential (as generated by potentiometry/galvanometry), or an accumulated charge (as generated by coulometry). In electrochemical methods, the biosensor measures and correlates the electrical signal with the concentration of the analyte in the biological fluid.

Electrochemical biosensors usually include a measurement device that applies an input signal through electrical contacts to electrical conductors of the sensor strip. The conductors may be made from conductive materials, such as solid metals, metal pastes, conductive carbon, conductive carbon pastes, conductive polymers, and the like. The electrical conductors typically connect to working, counter, reference, and/or other electrodes that extend into a sample reservoir. One or more electrical conductors also may extend into the sample reservoir to provide functionality not provided by the electrodes. The measurement device may have the processing capability 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 may be adapted for use outside, inside, or partially inside a living organism. When used outside a living organism, a sample of the biological fluid is introduced into a sample reservoir in the sensor strip. The sensor strip may be placed in the measurement device before, after, or during the introduction of the sample for analysis. When inside or partially inside a living organism, the sensor strip may be continually immersed in the sample or the sample may be intermittently introduced to the strip. The sensor strip may include a reservoir that partially isolates a volume of the sample or be open to the sample. Similarly, the sample may continuously flow through the strip or be interrupted for analysis.

Sensor strips may include reagents that react with the analyte in the sample of biological fluid. The reagents may include an ionizing agent to facilitate the redox reaction of the analyte, as well as mediators or other substances that assist in transferring electrons between the analyte and the conductor. The ionizing agent may be an oxidoreductase, such as an analyte specific enzyme, which catalyzes the oxidation of glucose in a whole blood sample. The reagents may include a binder that holds the enzyme and mediator together.

Sensor strips may have an encoding pattern that provides coding information to the measurement device. The encoding pattern may be a separate component or may be partially or fully integrated with other components on the sensor strip. The coding information may be identification information indicating the type of sensor strip, the analyte(s) or biological fluid associated with the sensor strip, the manufacturing lot of the sensor strip, or the like. The coding information may indicate the correlation equation to use, changes to the correlation equation, or the like.

Correlation equations are mathematical representations of the relationship between the electrical signal and the analyte in an electrochemical biosensor or between light and the analyte in an optical biosensor. Correlation equations may be implemented to manipulate the electrical signal or light for determination of the analyte concentration. Correlation equations also may be implemented as a program number assignment (PNA) table of slopes and intercepts for the correlation equations, another look-up table, or the like. The measurement device uses the coding information to adjust the analysis of the biological fluid.

Many measurement devices obtain the coding 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.

Electrical encoding patterns usually have one or more electrical circuits with multiple contacts or pads. The measurement device may have one or more conductors that connect with each contact on the encoding pattern of the sensor strip. Typically, the measurement device applies an electrical signal through one or more of the conductors to one or more of the contacts on the encoding pattern. The measurement device measures the output signal from one or more of the other contacts. The measurement device may determine the coding information from the absence or presence of output signals from the contacts on the encoding pattern. The measurement device may determine the coding information from the electrical resistance of the output signals from the contacts on the encoding pattern.

In some electrical encoding patterns, the measurement device determines the coding information from the absence or presence of different contacts. The contacts may be removed, never formed, or disconnected from other parts of the electrical circuit. If the measurement device measures an output signal from the location of a contact, then the measurement device presumes a contact is present. If the measurement device does not measure an output signal, then the measurement device presumes a contact is absent.

In other electrical encoding patterns, the measurement device determines the coding information from the resistance of the electrical output signal from the contact. Typically, the amount of conductive material associated with each contact varies, thus changing the electrical resistance. Contacts may have additional or fewer layers of conductive material. The length and thickness of the connection between the contacts and the electrical circuit also may vary. The contacts may be removed, never formed, or disconnected from the electrical circuit.

Some optical encoding patterns have a sequence of lines and/or array of pads. The measurement device obtains the coding information by scanning the encoding pattern to determine the absence or presence of the lines or pads. Other optical encoding patterns have a sequence of bright and dark zones. The measurement device obtains the coding information by detecting the brightness values of the bright and dark zones.

Errors may occur with these conventional electrical and optical encoding patterns. During manufacturing, shipping, handling, and the like, the sensor strips may acquire or loose material. The additional or missing material may cause the measurement device to obtain the wrong coding information from the encoding pattern, which may prevent completion or cause a wrong analysis of the biological fluid.

In electrical encoding patterns, the additional or missing material may change or interfere with the coding information. The additional material may cover the contacts, the contact locations, or the connections between the contacts. If the additional material is conductive, the measurement device may determine that a contact is present when a contact is absent or may measure an incorrect resistance from a contact. If the additional material is non-conductive, the measurement device may determine that a contact is absent when a contact is present or may measure an incorrect resistance from a contact. Additionally, the missing material may have been part of the contacts or the connections between the contacts. Thus, the missing material may cause the measurement device to determine that a contact is absent when a contact is present or may cause the measurement device to measure an incorrect resistance.

In optical encoding patterns, the additional or missing material may change or interfere with the coding information. The additional material may cover or obstruct the encoding pattern or the gaps or spaces in the encoding pattern. The missing material may be misread as part of the encoding pattern. The additional or missing material may cause the measurement device to scan altered lines or pads.

Accordingly, there is an ongoing need for improved biosensors, especially those that may provide increasingly accurate and/or precise analyte concentration measurements. The systems, devices, and methods of the present invention overcome at least one of the disadvantages associated with encoding patterns on sensor strips used in biosensors.

SUMMARY

A biosensor system calibrates an analyte analysis to determine an analyte concentration in a biological fluid. The biosensor system applies test signals to a sequential conductive pattern of a sensor strip. The biosensor system selectively and sequentially connects test contacts with the conductive and non-conductive areas on the sequential conductive pattern, which generates two or more code signals in response to the test signals. The biosensor system uses the code signals to calibrate one or more correlation equations used to determine the analyte concentration.

A biosensor for determining an analyte concentration in a biological fluid may have a measurement device and a sensor strip. The measurement device has a processor connected to a pattern read device. The sensor strip has a sequential conductive pattern. The measurement device and sensor strip implement an analyte analysis. The analyte analysis has one or more correlation equations. The pattern read device applies test signals to the sequential conductive pattern. The sequential conductive pattern generates two or more code signals in response to the test signals. The processor calibrates one or more correlation equations in response to the code signals. The processor determines an analyte concentration responsive to one or more calibrated correlation equations.

Another biosensor for determining an analyte concentration in a biological fluid may have a measurement device and a sensor strip. The measurement device has a processor connected to a pattern read device. The pattern read device has three or more test contacts. The sensor strip has a sequential conductive pattern. The sequential conductive pattern has one or more conductive areas and one or more non-conductive areas. The pattern read device applies test signals to one or more test contacts and drives one or more test contacts to ground. The pattern read device selectively and sequentially connects the test contacts with the conductive and non-conductive areas on the sequential conductive pattern. The sequential conductive pattern generates two or more code signals in response to the test signals. The measurement device and sensor strip implement an analyte analysis. The analyte analysis has one or more correlation equations. The processor calibrates one or more correlation equations in response to the code signals. The processor determines an analyte concentration in response to one or more calibrated correlation equations.

In a method for calibrating an analysis of an analyte in a biological fluid, test signals are applied to a sequential conductive pattern. At least two code signals are generated in response to the test signals. At least one correlation equation is calibrated in response to the code signals. An analyte concentration is determined in response to at least one calibrated correlation equation.

DETAILED DESCRIPTION

A biosensor system uses coding information to analyze an analyte and to determine the analyte concentration in a sample of a biological fluid. The biosensor system has a measurement device that applies test signals to a sequential conductive pattern on a sensor strip. The sequential conductive pattern generates code signals in response to the test signals when the sensor strip is inserted into the measurement device. The code signals provide coding information, which the biosensor system may use in an optical and/or electrochemical analysis of the analyte in the biological fluid. The measurement device may use the coding information to calibrate one or more correlation equations used in the analysis of the analyte, identify the sensor strip, make a determination regarding the analyte analysis, or the like. The measurement device may determine the analyte concentration using one or more of the calibrated correlation equations.

FIG. 1depicts a schematic representation of a biosensor system100that determines an analyte concentration in a sample of a biological fluid. The biosensor system100includes a measurement device102and a sensor strip104. The measurement device102may be implemented as a bench-top device, a portable or hand-held device, or the like. The measurement device102and the sensor strip104implement an analyte analysis, which may be an electrochemical analysis, an optical analysis, a combination thereof, or the like. The biosensor system100determines analyte concentrations, including those of alcohol, glucose, uric acid, lactate, cholesterol, bilirubin, and the like in biological samples such as whole blood and urine. While a particular configuration is shown, the biosensor system100may have other configurations, including those with additional components.

The sensor strip104has a base106that forms a sample reservoir108and a channel110with an opening112. The reservoir108and the channel110may be covered by a lid with a vent. The reservoir108defines a partially-enclosed volume. The reservoir108may contain a composition that assists in retaining a liquid sample, such as water-swellable polymers or porous polymer matrices. Reagents may be deposited in the reservoir108and/or channel110. The reagent composition may include one or more enzymes, binders, mediators, and the like. The reagents may include a chemical indicator for an optical system. The sensor strip104may have other configurations.

The sensor strip104may have a sample interface114. In an electrochemical system, the sample interface114may have conductors connected to at least two electrodes, such as a working electrode and a counter electrode. The electrodes may be disposed on a surface of the base106that forms the reservoir108. The sample interface114may have other electrodes and/or conductors.

The sensor strip104may have a sequential conductive pattern130on the base106. The sequential conductive pattern130has intermittent conductive and non-conductive areas. “Intermittent” includes breaks in the continuity or an interrupted sequence of the conductive and non-conductive areas or the like. “Conductive” includes the capability to transmit an electrical signal and the like.

The conductive areas of the sequential conductive pattern130are formed by a conductive material located on the sensor strip104. The conductive material may be the same material used to form the conductors and/or electrodes in the sample interface114or another component on the sensor strip104. Conductive materials include carbon, silver, aluminum, palladium, copper, or the like. The conductive areas may be any dimension, such as a thin rectangle or trace, a wide square or rectangle, a linear or curvilinear configuration, combinations thereof, or the like. Conductive areas on the same sequential conductive pattern may have different dimensions, configurations, and/or thicknesses. The dimensions, configurations, and thickness may be selected to control or alter one or more of the code signals.

The conductive areas of the sequential conductive pattern130may be formed by applying conductive material onto a non-conductive material by printing or like technique. The conductive material may be disposed at selected locations on the non-conductive material with essentially the desired dimensions and thicknesses of the conductive areas. The conductive material also may be disposed as a layer on the non-conduction material with unwanted portions of the conductive material subsequently removed by laser ablation, scribing, photo etching, or like technique to form the desired dimensions of the conductive areas. The unwanted portions of the conductive layer may be removed to form one or more conductive areas of the desired dimensions and thickness at selected locations surrounded by the non-conductive areas. The unwanted portions of the conductive layer also may be removed to expose one or more non-conductive areas surrounded by the conductive areas. The conductive areas also may be formed by applying a layer of non-conductive material on a layer of electrically conductive material. Portions of the non-conductive material are subsequently removed by laser ablation, scribing, photo etching, or like technique to expose the desired dimensions of the conductive areas at selected locations. The non-conductive material forms the non-conductive areas of the sequential conductive pattern130. The conductive and non-conductive areas may be formed using other techniques.

The sequential conductive pattern130may be located where the conductive and non-conductive areas are essentially aligned with one or more of the working, counter, or other electrodes on the sensor strip104. The sequential conductive pattern130may be located on the top, bottom, sides, or any other location on the sensor strip104. The sequential conductive pattern130may be on a separate strip. For example, the sequential conductive pattern130may be on a coding strip for use with a set of measuring strips. The coding strip may be another strip or may be part of or attached to a package containing the set of measuring strips. In addition, the coding strip and the measuring strips each may have a sequential conductive pattern. For example, the coding strip may have a first sequential conductive pattern that provides more general coding information. Each measuring strip may have a second sequential conductive pattern that provides more specific coding information.

The measurement device102includes electrical circuitry116connected to a sensor interface118, a display120, and a pattern read device132. The sensor interface118and the pattern read device132may be the same component. The electrical circuitry116may include a processor122connected to a signal generator124, an optional temperature sensor126, and a storage medium128. Electrical circuitry116may have other configurations including those with additional components.

The sensor strip104may be configured for insertion into the measurement device102in only one orientation. The sensor strip104may be configured for insertion into the measurement device with an orientation that places the sequential conductive pattern130in electrical communication with the pattern read device132. The sensor strip104may be configured for insertion into the measurement device with an orientation that places the sample interface in electrical and/or optical communication with the sensor interface118. “Electrical communication” includes the capability to transfer electrical or other signals wirelessly or through physical contact. “Optical communication” includes the capability to transfer light. The sensor strip104may have other configurations, including those with different orientations.

The processor122provides a control signal to the pattern read device132. The control signal may be an electrical signal such as potential, current, or the like. The control signal operates test contacts in the pattern read device132that connect with the conductive and non-conductive areas in the sequential conductive pattern130when the sensor strip is inserted into the measurement device. The pattern read device132drives one test contact to ground and applies test signals to the other test contacts in response to the control signal. “Ground” includes zero or near zero potential, current, or the like.

The signal generator124provides an excitation signal to the sensor interface118in response to the processor122. In optical systems, the excitation signal operates a light source and a detector in the sensor interface118. In electrochemical systems, the excitation signal is transmitted by the sensor interface118through analysis contacts to the conductors and electrodes in the sample interface114to apply the excitation signal to the reservoir108and thus, to the sample of the biological fluid.

The excitation signal may be a potential or current and may be constant, variable, or a combination thereof, such as when an AC signal is applied with a DC signal offset. The excitation signal may be applied as a single pulse or in multiple pulses, sequences, or cycles. The signal generator124also may record an output signal from the sensor interface118as a generator-recorder.

The storage medium128may be a magnetic, optical, or semiconductor memory, another computer readable storage device, or the like. The storage medium128may be a fixed memory device or a removable memory device such as a memory card.

The processor122may implement analyte analysis and data treatment using computer readable software code and data stored in the storage medium128. The processor122may use coding information from the sequential conductive pattern130to calibrate the analyte analysis and data treatment.

The processor122may provide the control signal to the pattern read device132in response to the presence of the sensor strip104at the sensor interface118, user input, or the like. The processor122may start the analyte analysis after obtaining the coding information from the sequential conductive pattern130. To start the analysis, the processor122may direct the signal generator124to provide the excitation signal to the sensor interface118. The processor122may receive a sample temperature from the temperature sensor126, if so equipped.

The processor122receives coding information from the pattern read device132. The coding information is responsive to the conductive and non-conductive areas of the sequential conductive pattern130. The processor122also receives the output signal from the sensor interface118. The output signal is generated in response to the redox reaction of the analyte in the sample. The output signal may be generated using an optical system, an electrochemical system, or the like. The processor122may use a correlation equation to determine the concentration of the analyte in the sample from one or more output signals. The correlation equation may be calibrated by the processor122in response to the coding information from the sequential conductive pattern130. The results of the analyte analysis are output to the display120and may be stored in the storage medium128.

Correlation equations relate the analyte concentrations with the output signals and may be represented graphically, mathematically, a combination thereof, or the like. The correlation equations may be represented by a program number assignment (PNA) table, another look-up table, or the like that is stored in the storage medium128. Instructions regarding implementation of the analysis and use of the coding information may be provided by the computer readable software code stored in the storage medium128. The code may be object code or any other code describing or controlling the functionality described herein. The data from the analyte analysis may be subjected to one or more data treatments, including the determination of decay rates, K constants, slopes, intercepts, and/or sample temperature in the processor122.

The sensor interface118is in electrical and/or optical communication with the sample interface114. “Electrical communication” includes the transfer of excitation and output signals between the analysis contacts in the sensor interface118and the conductors and electrodes in the sample interface114. “Electrical communication” may be implemented wirelessly or through physical contact. The sensor interface118transmits the excitation signal from signal generator124to the sample interface114. The sensor interface118also transmits the output signal from the sample to the processor122and/or the signal generator124. “Optical communication” includes the transfer of light between an optical portal in the sample interface102and a light source or detector in the sensor interface108.

The pattern read device132is in electrical communication with the sequential conductive pattern130. Electrical communication includes the transfer of electrical or other signals between the test contacts in the pattern read device132and the conductive and non-conductive areas of the sequential conductive pattern130. Electrical communication may be implemented wirelessly or through physical contact.

The display120may be analog or digital. The display120may be a LCD, LED, or vacuum fluorescent display adapted to displaying a numerical reading.

In use, the processor122detects the insertion of the sensor strip into the measurement device. When the strip is inserted, the sequential conductive pattern130passes across the test contacts in the pattern read device132. The processor122provides a control signal to the pattern read device132, which drives one test contact to ground and applies test signals to other test contacts. As the pattern read device132passes across the sequential conductive pattern130, the test contacts selectively and sequentially connect with the intermittent conductive and non-conductive areas. The conductive areas connect the non-ground test contacts with the test contact driven to ground. The non-conductive areas essentially prevent electrical communication between the test contacts. The switching between ground test signals and non-ground test signals generates the code signals. The pattern read device132receives code signals from the sequential conductive pattern130in response to the test signals. The pattern read device132provides the code signals to the processor122.

After the sensor strip is inserted into the measurement device, a liquid sample for analysis is transferred into the reservoir108by introducing the liquid to the opening112. The liquid sample flows through the channel110and into the reservoir108, while expelling the previously contained air. The liquid sample chemically reacts with the reagents deposited in the channel110and/or the reservoir108.

The processor122directs the signal generator124to provide the excitation signal to the sensor interface118. In optical systems, the sensor interface118operates the detector and light source in response to the excitation signal. In electrochemical systems, the sensor interface118provides the excitation signal to the sample through the sample interface114. The processor122receives an output signal generated in response to the redox reaction of the analyte in the sample. The processor122determines the analyte concentration of the sample using one or more correlation equations. The processor122may calibrate the correlation equations in response to the coding information from the sequential conductive pattern130. The determined analyte concentration may be displayed and/or stored for future reference.

The measurement device102and the sensor strip104may implement an electrochemical analysis, an optical analysis, a combination thereof, or the like to determine one or more analyte concentrations in a sample of biological fluid. Optical analyses use the reaction of a chemical indicator with an analyte to determine the analyte concentration in the biological fluid. Electrochemical analyses use an oxidation/reduction or redox reaction of an analyte to determine the analyte concentration in the biological fluid.

An optical analysis generally measures the amount of light absorbed or generated by the reaction of a chemical indicator with the analyte. An enzyme may be included with the chemical indicator to enhance the reaction kinetics. The light from an optical system may be converted into an electrical signal, such as current or potential.

In light-absorption optical analyses, the chemical indicator produces a reaction product that absorbs light. An incident excitation beam from a light source is directed toward the sample. The incident beam may be reflected back from 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 an indication of the analyte concentration in the sample.

In light-generated optical analyses, the chemical detector fluoresces or emits light in response to the analyte during the redox reaction. A detector collects and measures the generated light. The amount of light produced by the chemical indicator is an indication of the analyte concentration in the sample.

During electrochemical analyses, an excitation signal is applied to the sample of the biological fluid. The excitation signal may be a potential or current and may be constant, variable, or a combination thereof. The excitation signal may be applied as a single pulse or in multiple pulses, sequences, or cycles. The analyte undergoes a redox reaction when the excitation signal is applied to the sample. An enzyme or similar species may be used to enhance the redox reaction of the analyte. A mediator may be used to maintain the oxidation state of the enzyme. The redox reaction generates an output signal that may be measured constantly or periodically during transient and/or steady-state output. Steady-state is when the change of a signal with respect to its independent input variable (time, etc.) is substantially constant, such as within ±10 or ±5%. Various electrochemical processes may be used such as amperometry, coulometry, voltammetry, gated amperometry, gated voltammetry, and the like.

The optical and electrochemical analyses use correlation equations to determine the analyte concentration of the biological fluid in the sample. Correlation equations are mathematical representations of the relationship between analyte concentrations and output signals such as light, current, or potential. The correlation equations may be linear, near linear, or curvilinear and may be described by a second order polynomial. From a correlation equation, an analyte concentration may be calculated for a particular output signal.

A biosensor may have one or more correlation equations stored in a memory for use during the optical or electrochemical analysis. Different correlation equations may be needed, especially when different sensor strips are used or operating parameters such as the sample temperature change. Correlation equations may be implemented to manipulate the output signal for determination of the analyte concentration. Correlation equations also may be implemented as a program number assignment (PNA) table of the slope and intercept for the correlation equations, another look-up table, or the like for comparison with the output signals to determine the analyte concentration.

InFIG. 1, the measurement device124may calibrate the correlation equations in response to the coding information from the sensor strip104. The measurement device124may use the coding information to identify the type or other feature of the sensor strip, to determine whether to analyze the sample in the sensor strip, or the like.

The pattern read device132provides the code signals from the sequential conductive pattern130to the processor122. The pattern read device132and/or processor122may combine the code signals to form a check signal. “Combine” includes summing, comparing, and the like operations on the code signals. The check signal may be used to identify errors, adjust the code signals for variability in the insertion rate of the sensor strip into the measurement device, or the like. The code and check signals may be digital signals or the like. “Digital signals” includes electrical signals that discretely switch between the presence and absence of current, switch between high and low potentials, or the like. “Discretely switch” includes substantially instantaneous transitions from one current, potential, or signal level to another. Digital signals may be transmitted as binary or other code. The processor122converts the code signals into the coding information for use with the sensor strip104. In response to the code and check signals, the processor122may calibrate one or more of the correlation equations, identify the sensor strip, make a determination regarding the analyte analysis, a combination thereof, or the like.

The coding information may be any information used to calibrate one or more correlation equations, identify the sensor strip or features of the sensor strip such as the reagent or the like, make a determination regarding the analysis, a combination thereof, or the like. “Calibrate” may include adjusting or modifying the concentration value or other result of a correlation equation. “Calibrate” may include selecting one or more correlation equations. The coding information may be identification information indicating the type of sensor strip, analyte(s) or biological fluid associated with the sensor strip, the manufacturing lot of the sensor strip, the expiration date of the sensor strip, or the like. The processor122may select one or more correlation equations to use in response to the identification information. “Calibrate” may include modifying one or more correlation equations. The coding information may provide or direct the use of an addition or subtraction to the slope and/or intercept of a correlation equation. “Calibrate” may include providing one or more of the correlation equations. The coding information may include or direct the use of a slope and intercept for a correlation equation. Other coding information may be used.

To obtain coding information, the pattern read device132receives the code signals generated by the intermittent conductive and non-conductive areas on the sequential conductive pattern130. When the sensor strip104is inserted into the measurement device102, the pattern read device132drives one test contact to ground and applies test signals to the other test contacts. The test contacts in the pattern read device132pass across the sequential conductive pattern130to generate the code signals. The number of code signals is responsive to the arrangement of conductive and non-conductive areas in the sequential conductive pattern130and the number of test contacts in the pattern read device132.

The test contacts selectively and sequentially connect with the conductive and nonconductive areas at different positions; which generates one or more code signals. “Selectively connects” may include having conductive areas at selected positions on a sequential read pattern, where one or more conductive areas connect only one selected non-ground test contact with the test contact driven to ground. “Selectively connects” may include having conductive areas at selected positions on a sequential read pattern, where one or more conductive areas connect all but one of selected non-ground test contacts with the test contact driven to ground. “Selectively connects” may include having conductive areas at selected positions on the sequential read pattern, where one or more selected conductive areas connect all non-ground test contacts with the test contact driven to ground. “Selectively connects” may include having one or more non-conductive areas aligned with the conductive areas at selected positions on a sequential read pattern, where one or more non-conductive areas connect with one or more selected non-ground test contacts when a conductive area connects the other non-ground test contacts with the test contact driven to ground. “Sequentially connects” may include moving a sequential conductive pattern in a selected direction across a pattern read device, where the conductive area and any aligned non-conductive areas connect with the test contacts in a selected order. The selected conductive areas, connections, positions, contacts, direction, order, and the like may be chosen during manufacture of the sensor strip and/or measurement device.

At a particular position, the conductive area connects the ground test contact with one or more non-ground test contacts. The ground test contact drives the non-ground test contacts to ground. Thus, the test signals of the test contacts connected with the conductive area are driven to ground at this position. In contrast, the non-conductive area connects with one or more non-ground test contacts. The non-conductive area essentially prevents electrical communication with these non-ground test contacts. Thus, the test signals of the test contacts connected with the non-conductive area remain substantially the same.

At different positions on the sequential read pattern130, the conductive and non-conductive areas may connect with the same or different non-ground test contacts as the other position. When the connections with the conductive and non-conductive areas are the same, the ground and non-ground test contacts at this position are essentially the same as the ground and non-ground test contacts at the other position. The same ground and non-ground test contacts produce the same ground and non-ground test signals. When the connections with the conductive and non-conductive areas are different, the ground and non-ground test contacts at this position are different than the ground and non-ground test contacts at the other position. The different ground and non-ground test contacts produce different ground and non-ground test signals at each position.

As the sequential conductive pattern130moves across the pattern read device132, test contacts selectively connect with conductive and nonconductive areas at each position in sequence. When connections are the same, the ground and non-ground test signals are essentially the same. When connections are different, the ground and non-ground test signals are different. This selective and sequential switching or non-switching between ground and non-ground test signals generates the code signals.

While an implementation is described using ground and non-ground test signals, the code signals may be generated using a test contact driven to a different potential, current, or signal level than the test signals applied to the other test contacts. The switching between the different potentials, currents, or signal levels would generate the code signals.

The code signals are essentially digital signals that represent the switching between ground and non-ground test signals as the test contacts in the pattern read device132selectively and sequentially connect with the intermittent conductive and non-conductive areas in the sequential conductive pattern130. While the switching between ground and non-ground test signals is substantially discrete, there may be a contact bounce when the test contacts engage and disengage the conductive and/or non-conductive areas. When the contact bounce occurs, the signal may have a very rapid switching burst where the signal oscillates quickly between ground and non-ground for a short duration.

FIG. 2depicts a sensor strip204adjacent to a sensor interface218and a pattern read device232along with code and check signals generated by the sensor strip204. While a particular configuration is shown, the sensor strip204, the sensor interface218, and the pattern read device232may have other configurations including those with additional components. Other code signals may be generated.

The sensor strip204includes a sample interface214and a sequential conductive pattern230. The reservoir, channel, and opening of the sensor strip have been omitted for clarity. The sample interface214includes a working electrode234and a counter electrode236. The sequential conductive pattern230has conductive areas238,240,242,244,246, and248disposed on a non-conductive layer, which forms non-conductive areas250. The conductive areas238,240,242,244,246, and248may be traces or thin rectangles of conductive material disposed sequentially in positions essentially equidistant from each other in the sequential conductive pattern. The conductive areas238,240,242,244,246, and248are disposed substantially perpendicular to the direction the sensor strip204moves when inserted into a measurement device. The conductive areas238,240,242,244,246, and248may have other configurations and may be disposed in different positions and/or orientations.

The sensor interface218includes a first analysis contact252and a second analysis contact254. When the sensor strip204is inserted properly into a measurement device, the first analysis contact252and the second analysis contact254connect with the working electrode234and the counter electrode236, respectively, in the sample interface214. A processor in the measurement device applies an excitation signal to the working and counter electrodes234and236through the first and second analysis contacts252and254. The processor does not attempt to apply the excitation signal until the working and counter electrodes234and236pass the sequential conductive pattern230.

The pattern read device232includes a first test contact256, a second test contact258, and a third test contact260. When the sensor strip is inserted into the measurement device, the processor in the measurement device drives test contact258to ground and applies test signals to test contacts256and258. As the sensor strip204passes across the pattern read device232, the test contacts256,258, and260selectively and sequentially connect with conductive areas238,240,242,244,246, and248and non-conductive area250in the sequential conductive pattern230. When the test contacts256and258connect with the conductive areas242,246, and248, the test contact260connects with the non-conductive areas250in the sequential conductive pattern230. When the test contacts258and260connect with the conductive areas238,240, and244, the test contact256connects with the non-conductive areas250in the sequential conductive pattern230. The conductive areas238,240,242,244,246, and248have a length selected to connect the second test contact258with either the first test contact256or the third test contact260, but not the other test contact. One or more of the conductive areas238,240,242,244,246, and248may have a length selected to connect the second test contact258with both the first test contact256and the third test contact260.

FIG. 3depicts electrical detection circuitry262in the pattern read device232ofFIG. 2. The electrical detection circuitry262includes a first buffer circuit264connected to the first test contact256, a ground266connected to the second test contact258, and a second buffer circuit268connected to the third test contact260ofFIG. 2. The first buffer circuit264includes input potential Vccconnected through resister R1to the first test contact256and the input of a buffer U1. The second buffer circuit268includes input potential Vccconnected through resister R2to the third test contact260and the input of a buffer U2. Other electrical detection circuitry may be used.

Referring toFIG. 2, when the first test contact256connects with the second test contact258through a conductive area on the sequential conductive pattern230, the input of buffer U1becomes ground and the corresponding output of buffer U1is at logic zero (“0”). When the first test contact256connects with a non-conductive area on the sequential conductive pattern230, the input of buffer U1is pulled high by the input resistor R1and the corresponding output of buffer U1is at logic one (“1”). The sequential output of the buffer U1generates a first code signal.

When the third test contact260connects with the second test contact258through a conductive area on the sequential conductive pattern230, the input of buffer U2becomes ground and the corresponding output of buffer U2is at logic zero (“0”). When the third test contact260connects with a non-conductive area on the sequential conductive pattern230, the input of buffer U2is pulled high by the input resistor R1and the corresponding output of buffer U2is at logic one (“1”). The sequential output of the buffer U2generates a second code signal.

The outputs of buffers U1and U2may be designated by “0” and “1” patterns depending upon whether the buffer inputs are ground or not, respectively. The “0” and “1” patterns shown inFIG. 2were selected arbitrarily to identify the buffer output associated with a particular input. The patterns may be interchanged. Other patterns may be used and may result in different digital representations.

FIG. 2also depicts the first and second code signals270and274generated by the sensor strip204. The first code signal270illustrates the sequential connections of the first test contact256with the non-conductive areas250and the conductive areas242,246, and,248in the sequential conductive pattern230. When the first test contact256connects with the conductive areas242,246, and,248, the first test contact256connects with the second test contact258and thus is grounded. The second code signal274illustrates the sequential connections of the third test contact260with the non-conductive areas250and the conductive areas238,240, and,244in the sequential conductive pattern230. When the third test contact260connects with the conductive areas238,240, and,244, the third test contact260connects with the second test contact258and thus is grounded. The first code signal270and second code signal274may be represented by a logic sequence272, in which a logic value (0 or 1) indicates the relative output of the code signals at positions on the sensor strip204. For example, the logic value “0” indicates the first code signal270is not grounded and the second code signal274is grounded. The logic value “1” indicates the first code signal270is grounded and the second code signal274is not grounded. Other code signals, logic values, and logic sequences may be used.

The first and second code signals270and274and/or the logic sequence272may be used to provide coding information to a measurement device in a biosensor system. The measurement device may use the code signals and/or logic sequence to calibrate one or more correlation equations for the analyte analysis, identify the sensor strip or features of the sensor strip, make a determination regarding the analysis, a combination thereof, or the like. The measurement device may adjust or modify the concentration value or other result of a correlation equation, select one or more correlation equations, or the like in response to the code signals and/or logic sequence. The measurement device may use the code signals and/or logic sequence to identify the type of sensor strip, analyte(s) or biological fluid associated with the sensor strip, the manufacturing lot of the sensor strip, the expiration date of the sensor strip, or the like. The measurement device may select one or more correlation equations to use or may modify one or more correlation equations in response to the identification information. The code signals and/or logic sequence may provide or direct the use of an addition or subtraction to the slope and/or intercept of a correlation equation. The code signals and/or logic sequence may provide one or more of the correlation equations and may include or direct the use of a slope and intercept for a correlation equation. The code signals and/or logic sequence may provide other coding information.

The code signals represent the sequential connections between the test contacts and conductive and non-conductive areas in the sequential conductive pattern. The first code signal270represents the sequential connections between the first test contact256and the conductive and non-conductive areas in the sequential conductive pattern230. Similarly, the second code signal274represents the sequential connections between the third test contact260and the conductive and non-conductive areas in the sequential conductive pattern230. The sequential connections between the test contacts and the conductive and non-conductive areas generate unique code signals that provide coding information to the measurement device.

Different coding information may be generated by changing the location of the conductive areas in the sequential conductive pattern230. For example, when one or more of the conductive areas238,240, and244are moved to connect the second test contact258with the first test contact256; then third test contact260becomes connected with the non-conductive areas250. The first and second code signals270and274would change. In the first code signal270, one or more of the previously non-ground outputs would change to a ground output in response to the moved conductive areas238,240, and244. In the second code signal274, one or more of the previously ground outputs would change to a non-ground output in response to the moved conductive areas238,240, and244.

Similarly, when one or more of the conductive areas242,246, and248are moved to connect the second test contact258with the third test contact260; then first test contact256would be connected to the non-conductive areas250. Thus, the first and second code signals270and274would change. In the first code signal270, one or more of the previously ground outputs would change to a non-ground output in response to the moved conductive areas242,246, and248. In the second code signal274, one or more of the previously non-ground outputs would change to a ground output in response to the moved conductive areas242,246, and248. Other changes to the connections between the tests contacts and the conductive and non-conductive areas may be made.

The number of different code sequences depends upon the number of conductive areas in the sequential conductive pattern used to generate the two code signals. For example, the sequential conductive pattern230uses six conductive areas to generate the first and second code signals270and274. The arrangement of the conductive areas may be changed to generate up to 64 different code sequences for providing coding information to the measurement device.

Table 1 lists the number of different code sequences that binary coding (base 2) in relation to the number of conductive areas in a sequential read pattern. Other numbers of conductive areas may be used.

Two or more code signals may be used to detect fault conditions that affect or change the coding information. Errors with the coding information may occur when a fault condition happens. A fault condition exists when two test contacts are connected when the two test contacts should not be connected. A fault condition also exists when two test contacts are not connected when the two test contacts should be connected. Other fault conditions may occur. A fault condition may be due to unexpected connections and open circuit conditions from debris on the test contact, additional material or debris on the sensor strip, missing material or a scratch in the sequential conductive pattern on the sensor strip, a combination thereof, and the like.

When two code signals are generated by the sequential read pattern, a measurement device may use encoding rules to detect fault conditions. The encoding rules include: (1) when a position of the first control signal is ground, the corresponding position of the second control signal is non-ground; (2) when a position of the first control signal is non-ground, the corresponding position of the second control signal is ground; (3) when a position of the second control signal is ground, the corresponding position of the first control signal is non-ground; and (4) when a position of the second control signal is non-ground, the corresponding position of the first control signal is ground. The encoding rules may be adapted similarly for use with three or more code signals. Other encoding rules may be used.

To detect fault conditions, the measurement device compares buffer outputs at one or more corresponding positions of the first and second control signals. The measurement device detects a fault condition when the first and second code signals have essentially the same buffer output at one or more corresponding positions. For example, the measurement device may detect a fault condition when the buffer output is a logic zero at the same position in both the first and second code signals. A logic zero buffer output indicates the buffer input is ground for both the first and second code signals at that position. The ground buffer input indicates the ground test contact is connected to both non-ground test contacts. Similarly, the measurement device may detect a fault condition when the buffer output is a logic one at the same position in both the first and second code signals. A logic one buffer output indicates the buffer input is non-ground for both the first and second code signals at that position. The non-ground buffer input indicates the ground test contact is not connected to either non-ground test contact. The measurement device may detect other fault conditions. When a fault condition is detected, the measurement device may reject the sensor strip and/or may generate an error signal.

The multiple signals produced by inserting a sensor strip into a measuring device allows for inherent error checking of the coding information. The error checking may be obtained by enforcing rules regarding the signals that are simultaneously electrically generated as the sensor strip is inserted into the measuring device. For example, if the rule is only N of the M signals can be simultaneously electrically connected, and then faulty patterns or readings may not be erroneously interpreted as a valid calibration code. The measuring device thus may detect faulty patterns or readings and reject a sensor strip before an erroneous test result is reported or after the error is detected.

These encoding rules are in response to each conductive area on the sequential read pattern connecting the ground test contact with only one of the non-ground test contacts. However, the ground test contact may connect with both of the non-ground test contacts at one or more positions on the sequential read pattern. The connection of the ground test contact with both non-ground test contacts, preferably at the first position to reach the pattern read device may enable the measurement device to identify the sensor strip, calibrate the analyte analysis, or the like more quickly.

FIG. 2further depicts a check signal278generated by the sensor strip204. The check signal278may be represented by a logic sequence. The measurement device combines the first and second code signals270and274to produce the check signal278. Other check signals may be used.

The measurement device may use the check signal278to detect fault conditions in the first and second code signals. When a fault condition occurs, both buffer outputs may be a logic zero or a logic one at the same position in the first and second code signals. When these first and second code signals with a fault condition are compared, the output at the position of the fault condition may be indicated in the logic sequence.

The check signal278makes the code signals less sensitive or insensitive to the speed or changes in the speed in which the sensor strip is inserted into the measurement device. The check signal278provides the measurement device with a “self-clocking” capability. The check signal278enables the measurement device to determine when transitions of the buffer outputs occur in the first and second code signals. Buffer transitions occur when the buffer input changes from non-ground to ground or from ground to non-ground (from “1” to “0” or from “0” to “1”). Thus, the measurement device can determine when the next bit of the code signal, or transition from the buffer output, is available in each of the first and second code signals.

FIG. 4depicts another sensor strip404adjacent to a sensor interface418and a pattern read device432along with code and check signals generated by the sensor strip404. Sensor strip404is similar in configuration and operation to the sensor strip204described in relation toFIG. 2. Except in sensor strip404, a conductive area438is used to connect the ground test contact with all the non-ground test contacts in pattern read device438. While a particular configuration is shown, the sensor strip404, the sensor interface418, and the pattern read device432may have other configurations including those with additional components. Other code signals may be generated.

The sensor strip404includes a sample interface414and a sequential conductive pattern430. The reservoir, channel, and opening of the sensor strip have been omitted for clarity. The sample interface414includes a working electrode434and a counter electrode436. The sequential conductive pattern430has conductive areas438,440,442,444,446, and448disposed on a non-conductive layer, which forms non-conductive areas450. The conductive areas438,440,442,444,446, and448may have other configurations and may be disposed in different positions and orientations.

The sensor interface418includes a first analysis contact452and a second analysis contact454. When the sensor strip404is inserted properly into a measurement device, the first analysis contact452and second analysis contact454connect with the working electrode434and the counter electrode, respectively, in the sample interface414.

The pattern read device432includes a first test contact456, a second test contact458, and a third test contact460. When the sensor strip is inserted into the measurement device, the processor in the measurement device drives test contact458to ground and applies test signals to test contacts456and458. As the sensor strip404passes across the pattern read device432, the test contacts456,458, and460selectively and sequentially connect with conductive areas438,440,442,444,446, and448and the non-conductive areas450in the sequential conductive pattern430. When test contacts456,458, and460connect with conductive area438, there are no test contacts connected to the non-conductive areas450. When test contacts456and458connect with the conductive areas442,446, and448, the test contact460connects with the non-conductive areas450. When the test contacts458and460connect with the conductive areas440, and444, the test contact456connects with the non-conductive areas450.

The conductive areas440,442,444,446, and448have a length selected to connect the second test contact458with either the first test contact456or the third test contact460, but not the other test contact. The conductive area438has a length selected to connect the second test contact458with both the first test contact456and the third test contact460. Alternatively or additionally, one or more of the other conductive areas440,442,444,446, and448may have a length selected to connect the second test contact with both the first test contact456and the third test contact460. The connection of the second test contact458with the first test contact456and the second test contact460may enable the measurement device to identify the sensor strip, calibrate the analyte analysis, or the like more quickly.

FIG. 4also depicts the first and second code signals470and474generated by the sensor strip404. The first code signal470illustrates the sequential connections of the first test contact456with the non-conductive areas450and the conductive areas438,442,446, and,448in the sequential conductive pattern430. When the first test contact456connects with the conductive areas438,442,446, and,448, the first test contact456connects with the second test contact458and thus is grounded. The second code signal474illustrates the sequential connections of the third test contact460with the non-conductive areas450and the conductive areas438,440, and,444in the sequential conductive pattern430. When the third test contact460connects with the conductive areas438,440, and,444, the first test contact460connects with the second test contact458and thus is grounded. The first code signal470and second code signal474may be represented by a logic sequence472, in which a logic value (0, 1, or 2) indicates the relative output of the code signals at positions on the sensor strip404. For example, the logic value “0” indicates the first code signal470is not grounded and the second code signal474is grounded. The logic value “1” indicates the first code signal470is grounded and the second code signal474is not grounded. The logic value “2” indicates both the first code signal470and the second code signal474are grounded. Other code signals, logic values, and logic sequences may be used.

The first and second code signals470and474and/or logic sequence472may be used to provide coding information to a measurement device in a biosensor system as previously discussed. The code signals represent the sequential connections between the test contacts and conductive and non-conductive areas in the sequential conductive pattern. The sequential connections between the test contacts and the conductive and non-conductive areas generate unique code signals that provide coding information to the measurement device. Different coding information may be generated by changing the location of the conductive areas in the sequential conductive pattern430. The first and second code signals470and474also may be used to detect fault conditions that affect or change the coding information as previously discussed.

FIG. 4further depicts a check signal478generated by the sensor strip404. The check signal478may be represented by a logic sequence. The check signal478indicates the position of the other outputs. The measurement device combines the first and second code signals470and474to produce the check signal478. Other check signals may be used. The measurement device may use the check signal478to detect fault conditions in the first and second code signals as previously discussed, except that the connection of test contacts456,458, and460with conductive area438at the first output or position would not indicate a fault condition. The check signal478also makes the code signals less sensitive or insensitive to the speed or changes in the speed in which the sensor strip is inserted into the measurement device as previously discussed.

FIG. 5depicts an additional sensor strip504adjacent to a sensor interface518and a pattern read device532along with code and check signals generated by the sensor strip504. Sensor strip504is similar in configuration and operation to the sensor strip204described in relation toFIG. 2. Except in sensor strip504, the non-conductive areas are formed by removing unwanted portions of a conductive layer on a non-conductive layer to expose non-conductive areas surrounded by conductive areas. While a particular configuration is shown, sensor strip504, sensor interface518, and pattern read device532may have other configurations including those with additional components. Other code signals may be generated.

The sensor strip504includes a sample interface514and a sequential conductive pattern530. The reservoir, channel, and opening of the sensor strip have been omitted for clarity. The sample interface514includes a working electrode534and a counter electrode536. The sequential conductive pattern530has non-conductive areas538-548surrounded by conductive areas550. The non-conductive areas538-548are rectangles of non-conductive material exposed by the removal of the conductive material that forms the conductive areas550. The non-conductive areas538-548may be formed by removing essentially all the conductive material to expose substantially all the non-conductive material within each rectangle. The non conductive areas538-548may be formed by removing the conductive material to expose non-conductive material along the perimeter of the rectangle, thus forming an inner conductive portion essentially surrounded by an outer non-conductive portion. The non-conductive areas538-548may have other configurations including those with different positions, shapes, and orientations.

The sensor interface518includes a first analysis contact552and a second analysis contact554. When the sensor strip504is inserted properly into a measurement device, the first analysis contact552and second analysis contact554connect with the working electrode534and the counter electrode, respectively, in the sample interface514. A processor in the measurement device applies an excitation signal to the working and counter electrodes534and536through the first and second analysis contacts552and554. The processor does not attempt to apply the excitation signal until the working and counter electrodes534and536pass the sequential conductive pattern530.

The pattern read device532includes a first test contact556, a second test contact558, and a third test contact560. When the sensor strip is inserted into the measurement device, the processor in the measurement device drives test contact558to ground and applies test signals to test contacts556and558. As the sensor strip504passes across the pattern read device532, the test contacts556,558, and560selectively and sequentially connect with non-conductive areas538-548and conductive areas550in the sequential conductive pattern530.

When the test contact556connects with the non-conductive areas538-540, the test contacts558and560connect with the conductive areas550in the sequential conductive pattern530. When the test contact558connects with the non-conductive areas541-545, the test contacts556and560are electrically isolated from the test contact558at essentially the same time. When the test contact560connects with the non-conductive areas546-548, the tests contacts556and558connect with the conductive areas550in the sequential conductive pattern530. The non-conductive areas538-548may have an area selected to reduce or eliminate the affect a misalignment of the test contacts and/or sensor strip may have. One or more of the non-conductive areas538-548may be omitted to connect the second test contact558with both the first test contact556and the third test contact560.

FIG. 5also depicts code signals generated by the sensor strip504. The first code signal570illustrates the sequential connections of the first test contact556with non-conductive areas538-545and the conductive areas550in the sequential conductive pattern530. The second code signal574illustrates the sequential connections of the third test contact560with non-conductive areas541-548and the conductive areas550in the sequential conductive pattern530. The first code signal570and second code signal574may be represented by the a logic sequence572, in which a logic value (0 or 1) indicates the relative output of the code signals at positions on the sensor strip504. For example, the logic value “0” indicates the first code signal570is not grounded and the second code signal574is grounded. The logic value “1” indicates the first code signal570is grounded and the second code signal574is not grounded. Other code signals, logic values, and logic sequences may be used. The first and second code signals570and574and/or logic sequence572may be used to provide coding information to a measurement device in a biosensor system and to detect fault conditions that affect or change the coding information as previously discussed.

Different coding information may be generated by changing the location of the non-conductive areas in the sequential conductive pattern530. For example, when one or more of the non-conductive areas538-540are moved to connect with the third test contact560; the first test contact558then would be connected with the second test contact558. Thus, the first and second code signals570and574would change. In the first code signal570, one or more of the previously non-ground outputs would change to a ground output in response to the move of non-conductive areas538-540. In the second code signal574, one or more of the previously ground outputs would change to a non-ground output in response to the move of non-conductive areas538-540.

Similarly, when one or more of the non-conductive areas546-548are moved to connect with the first test contact556; the third test contact560then would be connected with the second test contact558. Thus, the first and second code signals570and574would change. In the first code signal570, one or more of the previously ground outputs would change to a non-ground output in response to the move of non-conductive areas546-548. In the second code signal574, one or more of the previously non-ground outputs would change to a ground output in response to the move of non-conductive areas546-548. Other changes to the connections between the tests contacts and the conductive and non-conductive areas may be made.

FIG. 5further depicts a check signal578generated by the sensor strip504. The check signal578may be represented by a logic sequence. The measurement device combines the first and second code signals570and574to produce the check signal578. Other check signals may be used. The measurement device may use the check signal578to detect fault conditions in the first and second code signals as previously discussed. The check signal578also makes the code signals less sensitive or insensitive to the speed or changes in the speed in which the sensor strip is inserted into the measurement device as previously discussed.

FIG. 6depicts a further sensor strip604adjacent to a pattern read device632along with code signals generated by the sensor strip604. The sensor interface has been omitted for clarity. While a particular configuration is shown, the sensor strip604and the pattern read device632may have other configurations including those with additional components. Other code signals may be generated.

The sensor strip604includes a sequential conductive pattern630. The sample interface, reservoir, channel, and opening of the sensor strip have been omitted for clarity. The sequential conductive pattern630has conductive areas638,640,642,644,646, and648disposed on a non-conductive layer, which forms non-conductive areas650. The conductive areas638,640,642,644,646, and648are traces of conductive material disposed sequentially in positions substantially perpendicular to the direction the sensor strip604moves when inserted into a measurement device. The conductive areas638,640,642,644,646, and648may have other configurations including those where one or more of the conductive areas connects all the test contacts. The conductive areas638,640,642,644,646, and648may be disposed in different positions and orientations.

The electrical resistance of the conductive material in each conductive area638,640,642,644,646, and648may be selected to alter the amount of a test signal transmitted through the particular conductive area. The conductive areas640and646each have a higher resistance than conductive areas638,642,644and648. Thus, the conductive areas640and646each transmit less of a test signal than the conductive areas638,642,644and648. By transmitting less of a test signal, the conductive areas640and646may partially ground the non-ground test contacts. The conductive areas638,640,642,644,646, and648may have other resistances.

The amount of the test signal transmitted through each conductive area may be used to provide more coding information than determining only whether the conductive areas are transmitting or not transmitting the test signals. The amount of test signal transmitted through a conductive area is inversely proportional to the resistance in the conductive area and may be measured by a measurement device. By changing the resistance of the conductive areas, the different amounts of each test signal transmitted through the conductive areas may provide additional coding information.

The resistance of the conductive areas may be changed by increasing or decreasing the length of the connection between the test contacts. A higher resistance would result from a longer connection, while a lower resistance would result from a shorter connection. The resistance of the conductive areas also may be changed by varying the conductive material thickness or selecting conductive materials with different bulk resistivity.

The resistance, R, of a rectangular block of material may be calculated by the following equation:

R=ρ⁢⁢LA=ρ⁢⁢LtW.(Equation⁢⁢1)
Where ρ is the material bulk resistivity, L is the length, A is the cross sectional area, W is the width, and t is the material thickness.

The pattern read device632includes a first test contact656, a second test contact658, and a third test contact660. When the sensor strip is inserted into the measurement device, the processor in the measurement device drives test contact658to ground and applies test signals to test contacts656and658. As the sensor strip604passes across the pattern read device632, the test contacts656,658, and660selectively and sequentially connect with conductive areas638,640,642,644,646, and648and non-conductive areas650in the sequential conductive pattern630.

When the first and second test contacts656and658connect with the conductive areas642,646, and648, the third test contact660connects with the non-conductive areas in the sequential conductive pattern630. Since the conductive area646has a higher resistance than the conductive areas642and648, the conductive area646transmits less of the test signal between test contacts656and658than the conductive areas642and648. Thus, the first test contact656may be partially grounded by the connection with the second test contact658through the conductive area646. In contrast, the first test contact656may be grounded by the connection with the second test contact658through the conductive areas642and648. The differences between the amount of test signal transmitted through each conductive area642,646, and648may provide additional coding information.

When the second and third test contacts658and660connect with conductive areas638,640, and644, the first test contact656connects with the non-conductive areas in the sequential conductive pattern630. Since the conductive area640has a higher resistance than the conductive areas638and644, the conductive area640will transmit less of the test signal between test contacts658and660than the conductive areas638and644. Thus, third first test contact660may be partially grounded by the connection with the second test contact658through the conductive area640. In contrast, the third test contact660may be grounded by the connection with the second test contact658through the conductive areas632and644. The differences between the amount of test signal transmitted through each conductive area642,646, and648may provide additional coding information.

FIG. 6also depicts the first and second code signals670and674generated by the sensor strip604. The first code signal670illustrates the sequential connections of the first test contact656with non-conductive areas650and the conductive areas642,646, and,648in the sequential conductive pattern630. The second code signal674illustrates the sequential connections of the third test contact660with non-conductive areas650and the conductive areas638,640, and,644in the sequential conductive pattern630. Other code signals may be used.

FIG. 6also depicts a logic sequence672for the code signals. In the logic sequence672, a logic value (0, 1, 2, or 3) indicates the relative output of the code signals at positions on the sensor strip604. For example, the logic value “0” indicates the first code signal670is not grounded and the second code signal674is grounded through a lower resistance connection, such as when the third test contact660and the second test contact658connect with conductive areas638and644. The logic value “1” indicates the second code signal674is not grounded and the first code signal670is grounded through a lower resistance connection, such as when the first test contact656and the second contact658connect with conductive areas642and648. The logic value “2” indicates the first code signal670is not grounded and the second code signal674is partially grounded through a higher resistance connection, such as when the third test contact660and the second test contact658connect with conductive area640. The logic value “3” indicates the second code signal674is not grounded and the first code signal670is grounded through a higher resistance connection, such as when the first test contact656and the second contact658connect with conductive area646. Thus, the presence of the conductive areas represents four different logic values, or base 4 coding. Additional resistance values may be used to represent more logic values. Other logic values and logic sequences may be used.

The first and second code signals670and674and/or logic sequence672may be used, as previously discussed, to provide coding information to a measurement device in a biosensor system and to detect fault conditions that affect or change the coding information. Different coding information may be generated by changing the location of the conductive areas in the sequential conductive pattern630. The first and second code signals670and674may be combined to generate a check signal as previously discussed.

FIG. 7depicts another sensor strip704adjacent to a sensor interface718and a pattern read device732along with code signals generated by the sensor strip704. While a particular configuration is shown, the sensor strip704, the sensor interface718, and the pattern read device732may have other configurations including those with additional components. Other code signals may be generated.

The sensor strip704includes a sample interface714and a sequential conductive pattern730. The reservoir, channel, and opening of the sensor strip have been omitted for clarity. The sample interface714includes a working electrode734and a counter electrode736. The sequential conductive pattern730has conductive areas738-746disposed on a non-conductive layer, which forms non-conductive areas750. The conductive areas738-746are traces or thin rectangles of conductive material disposed sequentially in positions essentially equidistant from each other and substantially perpendicular to the direction the sensor strip704moves when inserted into a measurement device. The conductive areas738-746may have other configurations and may be disposed in different positions and orientations.

The sensor interface718includes a first analysis contact752and a second analysis contact754. When the sensor strip704is inserted properly into a measurement device, the first analysis contact752and second analysis contact754connect with the working electrode734and the counter electrode, respectively, in the sample interface718. A processor in the measurement device applies an excitation signal to the working and counter electrodes734and736through the first and second analysis contacts752and754. The processor does not attempt to apply the excitation signal until the working and counter electrodes734and736pass the sequential conductive pattern730.

The pattern read device732includes a first test contact756, a second test contact758, a third test contact760, and a fourth test contact761. When the sensor strip704is inserted into the measurement device, the sequential conductive pattern730passes across the pattern read device732. The test contacts756,758,760, and761selectively and sequentially connect with conductive areas738-746and non-conductive areas750in the sequential conductive pattern730.

The lengths and positions of the conductive areas738-746may be selected to connect with two pairs of adjacent test contacts at each position on the sequential conductive pattern730, while the third pair of adjacent test contacts is connected with non-conductive areas750. The pairs of adjacent test contacts are the first and second test contacts756and758, the second and third test contacts758and760, and the third and fourth test contacts760and761.

FIG. 7also depicts code signals generated by the sensor strip704. The first code signal770illustrates the sequential connections of the first and second test contacts756and758with non-conductive areas750and the conductive areas739,740,743, and745in the sequential conductive pattern730. The second code signal774illustrates the sequential connections of the second and third test contacts758and760with non-conductive areas750and the conductive areas738,739,742, and743in the sequential conductive pattern730. The third code signal775illustrates the sequential connections of the third and fourth test contacts760and761with non-conductive areas750and the conductive areas738,740,741, and746in the sequential conductive pattern730. Other code signals may be used.

The code signals770,774, and775may be represented by the logic sequence772, which is ternary (base 3) encoding. With ternary coding, each position on the sequential conductive pattern730encodes three levels. The sequential conductive pattern730illustrates six positions, which provides729distinct values that may be encoded on sensor strip704. In logic sequence772, a logic value (0, 1, or 2) indicates the relative output of the code signals at positions on the sensor strip704. For example, the logic value “0” indicates the first code signal770is not grounded and the second and third code signals774and775are grounded. The logic value “1” indicates the first and third code signals770and775are grounded and the second code signal774is not grounded. The logic value “2” indicates the first and second code signals770and774are grounded and the third code signal775is not grounded. Other logic values and logic sequences may be used.

Table 2 lists the number of different code sequences with ternary coding (base 3) in relation to the number of conductive areas in a sequential read pattern. Other numbers of conductive areas may be used.

Additional test contacts may be used to increase the available codes at each position. With five test contacts, each position multiplies the number of levels by four. With six test contacts, each position multiplies the number of levels by five. Other numbers of contacts may be used.

The code signals and/or logic sequence may be used to provide coding information to a measurement device in a biosensor system. The code signals may be combined to generate a check signal. Different coding information may be generated by changing the location of the conductive areas in the sequential conductive pattern.

The code signals may be used to detect fault conditions. At each position of conductive areas on a sequential conductive pattern, two pairs of adjacent test contacts are connected with one or more conductive areas, and the third pair of adjacent test contacts is connected with the non-conductive area. If there is a fault condition where a connection with the conductive areas is not made, then there will be too few positions detected by the measurement device. If there is a fault condition where a connection is made that should not be made, then there will be too many positions detected by the measurement device.

FIG. 8depicts another sensor strip804adjacent to a sensor interface818and a pattern read device838along with code signals generated by the sensor strip804. While a particular configuration is shown, the sensor strip804, the sensor interface818, and the pattern read device832may have other configurations including those with additional components. Other code signals may be generated.

The sensor strip804includes a sample interface814and a sequential conductive pattern830. The reservoir, channel, and opening of the sensor strip have been omitted for clarity. The sample interface814includes a working electrode834and a counter electrode836. The sequential conductive pattern830has conductive areas838-844disposed on a non-conductive layer, which forms non-conductive areas850. The conductive areas838-844are traces or thin rectangles of conductive material disposed sequentially in positions essentially equidistant from each other and substantially perpendicular to the direction the sensor strip804moves when inserted into a measurement device. The conductive areas838-844may have other configurations and may be disposed in different positions and orientations.

The sensor interface818includes a first analysis contact852and a second analysis contact854. When the sensor strip804is inserted properly into a measurement device, the first analysis contact852and second analysis contact854connect with the working electrode834and the counter electrode, respectively, in the sample interface814. A processor in the measurement device applies an excitation signal to the working and counter electrodes834and836through the first and second analysis contacts852and854. The processor does not attempt to apply the excitation signal until the working and counter electrodes834and836pass the sequential conductive pattern830.

The pattern read device832includes a first test contact856, a second test contact858, a third test contact860, and a fourth test contact861. When the sensor strip804is inserted into the measurement device, the sequential conductive pattern830passes across the pattern read device832. The test contacts856,858,860, and861selectively and sequentially connect with conductive areas838-844and non-conductive areas850in the sequential conductive pattern830.

The lengths and positions of the conductive areas838-844may be selected to connect with one pair of adjacent test contacts at each position on the sequential conductive pattern830, while the other two pairs of adjacent test contacts are connected with non-conductive areas850. The pairs of adjacent test contacts are the first and second test contacts856and858, the second and third test contacts858and860, and the third and fourth test contacts860and861.

FIG. 8also depicts code signals generated by the sensor strip804. The first code signal870illustrates the sequential connections of the first and second test contacts856and858with non-conductive areas850and the conductive areas838,840, and843in the sequential conductive pattern830. The second code signal874illustrates the sequential connections of the second and third test contacts858and860with non-conductive areas850and the conductive areas839and842in the sequential conductive pattern830. The third code signal875illustrates the sequential connections of the third and fourth test contacts860and861with non-conductive areas850and the conductive areas841,842, and844in the sequential conductive pattern830. The code signals may be represented by a logic sequence. Other code signals may be used.

The code signals870,874, and875may be represented by the logic sequence872, which also is ternary (base 3) encoding as previously discussed. In logic sequence872, a logic value (0, 1, or 2) indicates the relative output of the code signals at positions on the sensor strip804. For example, the logic value “0” indicates the first code signal870is grounded and the second and third code signals874and875are not grounded. The logic value “1” indicates the first and third code signals870and875are not grounded and the second code signal874is grounded. The logic value “2” indicates the first and second code signals870and874are not grounded and the third code signal875is grounded. Other logic values and logic sequences may be used.

The code signals and/or logic sequence may be used to provide coding information to a measurement device in a biosensor system and to detect fault conditions. The code signals may be combined to generate a check signal. Different coding information may be generated by changing the location of the conductive areas in the sequential conductive pattern.

FIG. 9depicts another electrical detection circuitry962in a pattern read device. The electrical detection circuitry962includes a first buffer circuit964connected to the first test contact956, a ground966connected to the second test contact958, and a second buffer circuit968connected to the third test contact960. The electrical detection circuitry962enables the first and third test contacts956and960to be used as analysis contacts due to switches in the buffer circuits964and968that connect the test contacts with the processor and/or signal generator in the measurement device. Other electrical detection circuitry may be used.

The first buffer circuit964includes input potential Vccconnected through resister R1to switch SW1and the input of a buffer U1. Switch SW1is connected to the first test contact956and to a first input conductor980from a processor and/or signal generator in the measurement device. The output of buffer U1is connected to a processor in the measurement device via a first output conductor982.

In use, switch SW1initially connects the first test contact956with the input of buffer U1while the sequential conductive pattern on a sensor strip passes across the pattern read device. When the first test contact956connects with the second test contact958through a conductive area on the sequential conductive pattern930, the input of buffer U1becomes ground and the corresponding output of buffer U1is at logic zero (“0”). When the first test contact956connects with a non-conductive area on the sequential conductive pattern930, the input of buffer U1is pulled high by the input resistor R1and the corresponding output of buffer U1is at logic one (“1”). The sequential output of the buffer U1generates a code signal.

After the first test contact956moves past the pattern read device and connects with the working or other electrode on the sensor strip, the switch SW1connects the first test contact956with the first input conductor980. The switch SW1disconnects the first test contact956from the input of buffer U1. The processor and/or signal generator in the measurement device applies the excitation signal to the working or other electrode through the first input conductor980, switch SW1, and the first test contact956. The switch SW1may be controlled by the processor using software stored in the storage medium.

The second buffer circuit968includes input potential Vccconnected through resister R2to switch SW2and the input of a buffer U2. Switch SW2is connected to the third test contact960and to a second input conductor984from a processor and/or signal generator in the measurement device. The output of buffer U2is connected to a processor in the measurement device via a second output conductor986.

In use, switch SW2initially connects the third test contact960with the input of buffer U2while the sequential conductive pattern on a sensor strip passes across the pattern read device. When the third test contact960connects with the second test contact958through a conductive area on the sequential conductive pattern930, the input of buffer U2becomes ground and the corresponding output of buffer U2is at logic zero (“0”). When the third test contact960connects with a non-conductive area on the sequential conductive pattern930, the input of buffer U2is pulled high by the input resistor R1and the corresponding output of buffer U2is at logic one (“1”). The sequential output of the buffer U2generates a code signal.

After the third test contact960moves past the pattern read device and connects with the counter or other electrode on the sensor strip, the switch SW1connects the third test contact960with the second input conductor984. The switch SW2disconnects the third test contact960from the input of buffer U2. The processor and/or signal generator in the measurement device applies the excitation signal to the counter or other electrode through the second input conductor984, switch SW2, and the third test contact960. The switch SW2may be controlled by the processor using software stored in the storage medium.

FIG. 10represents a method for calibrating an analysis of an analyte in a biological fluid. In1002, a measurement device detects the presence of a sensor strip in a biosensor. In1004, the measurement device applies test signals to a sequential conductive pattern. In1006, the sequential conductive pattern generates at least two code signals. In1008, the measurement device determines coding information in response to code signals. In1010, the measurement device detects when a sample of a biological fluid is available for analysis. In1012, the measurement device calibrates one or more correlation equations in response to the coding information. In1014, the measurement device analyzes the analyte in the sample. In1016, the measurement device determines the analyte concentration of the biological fluid using one or more calibrated correlation equations.

In1002, the measurement device detects when a sensor strip is present. The measurement device may sense when a sensor strip is placed in the biosensor. The measurement device may sense (mechanically, electrically, or the like) when electrical contacts in the measurement device connect with electrical conductors and/or the sequential conductive pattern on the sensor strip. The measurement device may apply a one or more signals to the conductors and/or electrodes to detect when a sensor strip is present. The measurement device may apply a one or more signals to the sequential conductive pattern to detect when a sensor strip is present. The measurement device may use other methods and devices to detect when a sensor strip is present in a biosensor including user input.

In1004, the measurement device applies test signals to the sequential conductive pattern. The measurement device selectively and sequentially connects test contacts with intermittent conductive and non-conductive areas on the sequential conductive pattern as previously discussed. The measurement device drives one test contact to ground and applies the test signals to the other test contacts as previously discussed.

In1006, the sequential conductive pattern generates code signals in response to the test signals. The test contacts selectively and sequentially connect with the conductive and nonconductive areas at different positions. At each position, the conductive areas connect one or more non-ground test contacts with the test contact driven to ground. The non-conductive areas essentially prevent electrical communication between the test contacts. At different positions on the sequential read pattern, the conductive and non-conductive areas may connect with the same or different non-ground test contacts. When the connections with the conductive and non-conductive areas are the same, the test contacts have the same ground and non-ground test signals. When the connections with the conductive and non-conductive areas are different, the test contacts have different ground and non-ground test signals. This selective and sequential switching or non-switching between ground and non-ground test signals generates one or more code signals as previously discussed.

In1008, the measurement device determines the coding information in response to the code signals. The coding information may be any information used to adjust correlation equations for electrochemical and/or optical analyses, identify the sensor strip, and the like as previously discussed. The measurement device may select stored reference parameters and adjustments in response the coding information or code signals.

In1010, the measurement device detects when a sample of biological fluid is available for analysis. The measurement device may sense (mechanically, electrically, or the like) when electrical conductors in the sensor strip are in contact with a sample. The measurement device may apply one or more signals to the working, counter, and/or other electrodes to detect when a sample connects with the electrodes. The biosensor may use other methods and devices to detect when a sample is available for analysis.

In1012, the measurement device calibrates one or more correlation equations in response to the coding information. Correlation equations may be used to determine the analyte concentration in optical and/or electrochemical analyzes as previously discussed.

In1014, the measurement device analyzes the analyte in the sample using an electrochemical analysis, an optical analysis, a combination thereof, or the like. In an electrochemical analysis, the measurement device may use one or more electrochemical processes as previously discussed. The measurement device measures and correlates an output signal from a redox reaction of the analyte with the analyte concentration. In an optical analysis, the measurement device measures the amount of light absorbed or generated by the reaction of a chemical indicator with the analyte as previously discussed. The measurement device measures and correlates the amount of light with the analyte concentration.

In1016, the measurement device determines the analyte concentration in the sample of the biological fluid. The measurement device may use one or more of the calibrated correlation equations to determine the analyte concentration of the sample. The measurement device may use the calibrated analyte value or other result to determine the analyte concentration of the sample.

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.