Biosensing meter which detects proper electrode engagement and distinguishes sample and check strips

• US 5,438,271 A
• Filed: 11/22/1994
• Issued: 08/01/1995
• Est. Priority Date: 06/08/1993
• Status: Expired due to Term

• Current Assignee: Roche Diabetes Care Inc. (Roche Holding AG)
• Original Assignee: Boehringer Mannheim Corporation
• Inventors: Parks, Robert A., Ritchie, Paul G., White, Bradley E.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): TOBIN, C
• Application Number:
  US08/343,363
• Time in Patent Office: 252 Days
• Field of Search: 324/438, 324/439, 324/446, 324/450, 324/603, 324/692, 324/693, 324/525, 324/538, 204/401, 204/406, 422/82.02
• US Class Current: 324/444
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875

Abstract

A biosensing meter receives a biomedical sample strip or a check strip, a sample strip including electrically isolated excitation and sense electrodes. The biosensing meter includes first and second contacts that are positioned to be electrically connected by a sense electrode when a sample strip is inserted into the biosensing meter. An operational amplifier circuit has one input connected to the first contact and a second input connected to a reference potential, the one input manifesting the reference potential as a result of a feedback within the operational amplifier. A processor is coupled to the second contact and determines the presence of the reference potential at the second contact when an inserted sense electrode connects the first and second contacts. The processor also distinguishes between a sample strip and a check strip and, when a sample strip is inserted, that the sample strip exhibits a proper impedance between its sense and excitation electrodes--to enable operation of the biosensing meter upon dosing of the sample strip.

Claims

1. A biosensing meter for receiving a sample strip that includes electrically isolated excitation and sense electrodes that are bridged by an analyte reactant, said biosensing meter comprising:

a first contact and a second contact positioned to be electrically connected by said sense electrode when said sample strip is inserted into said biosensing meter;

operational amplifier means having one input connected to said first contact, a second input connected to a reference potential, an output, and a resistor directly connecting said output to said one input, whereby said one input is enabled to manifest said reference potential; and

processor means coupled to said second contact and responsive to a presence of said reference potential at said second contact as an indication that said sense electrode connects said first and second contacts.

2. The biosensing meter as recited in claim 1, said processor means further comprising:

means for applying a voltage to said second contact, said processor means sensing said voltage until said sense electrode connects said first and second contacts, at which time said operational amplifier means enables said second contact to manifest said reference potential.

3. The biosensing meter as recited in claim 2 further comprising:

third and fourth contacts positioned to be electrically connected by said excitation electrode when a said sample strip is inserted into said biosensing meter; and

means for determining, upon an insertion of said sample strip, that said third and fourth contacts are electrically connected.

4. The biosensing meter as recited in claim 3, further comprising:

means coupling said output of said operational amplifier means to said processor means; and

excitation supply means coupled to said third contact for applying an excitation voltage thereto, said processor means responding to an output from said operational amplifier that is at or below a first threshold level when said excitation voltage is applied to said third contact and to a connected excitation electrode, by determining that said sample strip exhibits a requisite level of electrical isolation between its excitation and sense electrodes.

5. The biosensing meter as recited in claim 4, wherein if said operational amplifier provides an output in excess of a second threshold level, said processor determines that said sample strip exhibits either too high a level of leakage current or an electrical short condition.

6. A biosensing meter for receiving said sample strip or a check strip, said sample strip including electrically isolated excitation and sense electrodes that are bridged by an analyte reactant, said biosensing meter including first and second contacts positioned to be electrically connected by said sense electrode when said sample strip is inserted into said biosensing meter, said check strip including an excitation electrode and a segmented sense electrode, a first sense electrode segment aligned with said first contact and a second sense electrode segment aligned with said second contact, both said sense electrode segments making respective electrical connections with said first and second contacts upon insertion of said check strip into said biosensing meter, said first sense electrode segment also connected via a first resistance to said check strip'"'"'s excitation electrode, said biosensing meter further comprising:

operational amplifier means having one input connected to said first contact, a second input connected to a reference potential, and an output directly connected by a second resistance to said one input to create a feedback path, whereby said one input manifests said reference potential; and

processor means coupled to said second contact and responsive to a presence of said reference potential at said second contact as an indication that a sample strip is present and has a sense electrode that electrically connects said first and second contacts.

7. The biosensing meter as recited in claim 6 further comprising:

means coupling said output of said operational amplifier means to said processor means; and

excitation means for applying an excitation voltage to an inserted excitation electrode of said check strip, and for causing, via said first resistance, a voltage to appear at said sense electrode which exceeds a first threshold, said processor means responsive to an output from said operational amplifier means that a voltage is present on said sense electrode that exceeds said first threshold to determine that said check strip is present in said biosensing meter.

8. The biosensing meter as recited in claim 7 wherein said first resistance connecting said first sense electrode segment to said excitation electrode is instrumental in assuring that said check strip causes said operational amplifier output to exceed said first threshold.

9. The biosensing meter as recited in claim 8, wherein upon determining a presence of an inserted check strip, said processor means causes excitation means to apply a plurality of excitation voltages to said excitation electrode for testing operations of said biosensing meter.

10. A biosensing meter for receiving a sample strip that includes electrically isolated excitation and sense electrodes that are bridged by an analyte reactant, said biosensing meter comprising:

first and second contact positioned to be electrically connected by an excitation electrode when said sample strip is inserted into said biosensing meter;

excitation voltage means for producing an excitation voltage;

amplifier means having one input connected to said excitation voltage means a second differential input connected to said second contact and an output connected to said first contact;

switch means connected between said first contact and said amplifier output and between said second contact and said second input, said switch means closed at all times except when a chemical incubation reaction is occuring with said analyte reactant, at which time said switch means is open;

processor means coupled to said second contact for determining a presence of an excitation voltage at said second contact as an indication that said sample strip has been inserted and for monitoring said excitation voltage at said second contact at least when said switch means are closed, as an assurance of a continued presence of said sample strip, until a test is completed, and of application of a proper level of excitation voltage during a test.