In-vitro sensor using a tetrapolar impedance measurement
Inventors
Paul, Patrick J. • Modzelewski, Brent E.
Assignees
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Publication Number
US-10718728-B2
Publication Date
2020-07-21
Expiration Date
Abstract
Systems, methods, and devices are provided for determining an impedance measurement of a sample of fluid on a test strip having a base layer, at least two drive electrodes disposed on the base layer and in electrical communication with a current-source (Iac) for flowing an AC current provided by the current-source (Iac) through a fluid sample between the at least two drive electrodes, and at least two sense electrodes disposed on the base layer and positioned between the at least two drive electrodes, each of the at least two sense electrodes configured for measuring a difference in an AC potential therebetween to determine an impedance measurement of the fluid sample between the at least two sense electrodes.
Core Innovation
The invention provides an in-vitro test strip having a base layer and a capillary chamber configured to receive a fluid sample. The test strip includes at least two drive electrodes disposed on the base layer to be placed in electrical communication with a current-source (Iac) for flowing an AC current through the fluid sample in the capillary chamber and between the drive electrodes. The strip further includes at least two sense electrodes disposed on the base layer and positioned between the drive electrodes, with each sense electrode configured for measuring a difference in an AC potential therebetween to determine an impedance measurement of the fluid sample between the sense electrodes.
A conductive trace extends from each drive electrode and runs parallel and adjacent to at least one sense electrode to eliminate or reduce stray capacitances by creating a capacitance bridge between the drive electrodes. When the sense electrodes are in direct electrical communication with a high input-impedance voltage measurement circuit to measure the difference in AC potential between the sense electrodes, the impedance measurement is indicative of a hematocrit level in the fluid sample. In related forms, the voltage measurement circuit includes a voltmeter configured to reduce AC current flowing between the sense electrodes so the sense electrodes are not subject to an electrode polarization impedance resulting from charge transfer between the sense electrodes.
The invention also provides a diagnostic meter that receives the test strip in a channel having a proximal end and a distal end. The diagnostic meter includes drive electrode contacts for contacting the drive electrodes and a current-source (Iac) for providing AC current to the drive electrodes, as well as sense electrode contacts for contacting the sense electrodes. A high input-impedance voltage measurement circuit measures the difference in AC potential between the sense electrodes and an instrumentation amplifier amplifies the measured difference in AC potential, with an output of the high input-impedance voltage measurement circuit and an output of the current-source coupled to a phase angle detection circuit.
Claims Coverage
The independent claims cover three related inventive features: an impedance-indicative-of-hematocrit test strip, a corresponding diagnostic meter architecture, and a system for measuring glucose concentration using the same impedance measurement approach.
Capillary chamber with drive and sense electrodes for AC impedance measurement indicative of hematocrit
A test strip includes a base layer and a capillary chamber configured to receive a fluid sample, at least two drive electrodes placed to be placed in electrical communication with a current-source (Iac) for flowing AC current through the fluid sample between the drive electrodes, and at least two sense electrodes disposed on the base layer between the drive electrodes, where the sense electrodes are configured for measuring a difference in an AC potential therebetween to determine an impedance measurement indicative of a hematocrit level when connected to a high input-impedance voltage measurement circuit.
Conductive traces parallel and adjacent to sense electrodes forming a capacitance bridge
A conductive trace extending from each drive electrode and running parallel and adjacent to at least one sense electrode eliminates or reduces stray capacitances by creating a capacitance bridge between the drive electrodes.
High input-impedance voltage measurement circuit reducing sense-electrode AC current to avoid electrode polarization impedance
A high input-impedance voltage measurement circuit with a voltmeter is configured to reduce AC current flowing between the sense electrodes when the sense electrodes are in direct electrical communication with the high input-impedance voltage measurement circuit, such that the sense electrodes are not subject to an electrode polarization impedance resulting from charge transfer between the sense electrodes.
Diagnostic meter coupling current-source and voltage-measurement outputs to phase angle detection
A diagnostic meter has a channel for receiving a test strip with drive electrode contacts contacting drive electrodes and sense electrode contacts contacting sense electrodes, a high input-impedance voltage measurement circuit measuring a difference in AC potential between the sense electrodes, and an instrumentation amplifier amplifying the measured difference in AC potential, wherein an output of the high input-impedance voltage measurement circuit and an output of the current-source (Iac) are each coupled to a phase angle detection circuit.
Glucose concentration system using hematocrit-indicative impedance measurement with phase angle detection
A system for measuring glucose concentration comprises a test strip with drive electrodes and sense electrodes arranged to measure an impedance measurement indicative of a hematocrit level from a difference in AC potential between the sense electrodes, and a diagnostic meter with a channel, drive electrode contacts, sense electrode contacts, a high input-impedance voltage measurement circuit directly connecting to the sense electrodes, and an instrumentation amplifier, wherein an output of the high input-impedance voltage measurement circuit and an output of the current-source (Iac) are coupled to a phase angle detection circuit.
Method of making a test strip with capacitance-bridge conductive traces
A method for making a test strip includes providing a base layer, forming a capillary chamber on the base layer, forming at least two drive electrodes for placing in electrical communication with a current-source (Iac) to flow AC current through a fluid sample between the drive electrodes, forming at least two sense electrodes positioned between the drive electrodes for measuring a difference in an AC potential therebetween to determine an impedance measurement indicative of a hematocrit level, and forming a conductive trace extending from each drive electrode running parallel and adjacent to at least one sense electrode to eliminate or reduce stray capacitances by creating a capacitance bridge between the drive electrodes.
Across the independent claims, the coverage centers on an AC impedance measurement scheme using drive electrodes and sense electrodes positioned between the drive electrodes to obtain a differential AC potential measurement indicative of hematocrit, combined with conductive trace layout to reduce stray capacitances via a capacitance bridge and measurement-circuit configurations using a high input-impedance voltage measurement circuit, and in some forms a voltmeter that reduces sense-electrode AC current to avoid electrode polarization impedance. The diagnostic meter and system claims further integrate instrumentation amplification and coupling of both the current-source and voltage-measurement outputs to a phase angle detection circuit, and include a glucose concentration system that relies on the hematocrit-indicative impedance measurement.
Stated Advantages
Reduces stray capacitances by creating a capacitance bridge between drive electrodes.
Impedance measurement is indicative of a hematocrit level in the fluid sample.
Reduces AC current flowing between sense electrodes so the sense electrodes are not subject to electrode polarization impedance resulting from charge transfer.
Enables impedance measurement processing using an instrumentation amplifier and phase angle detection circuit via coupled outputs.
Documented Applications
In-vitro/tetrapolar impedance sensing using a disposable test strip for hematocrit-indicative impedance measurement, used to support glucose accuracy through glucose/hematocrit correction context [procedural detail omitted for safety].
System for measuring glucose concentration using a diagnostic meter that performs impedance measurement indicative of hematocrit and couples outputs to phase angle detection.
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