Biosensing meter with ambient temperature estimation method and system

• US 5,405,511 A
• Filed: 06/08/1993
• Issued: 04/11/1995
• 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., Brown, Michael L., Weinert, Stefan, Svetnik, Vladimir
• Primary Examiner(s): Niebling, John
• Assistant Examiner(s): Bell, Bruce F.
• Application Number:
  US08/073,179
• Time in Patent Office: 672 Days
• Field of Search: 204/408, 204/403, 204/406, 204/407, 204/153.1, 204/153.12
• US Class Current: 205/777.5
• CPC Class Codes: G01K 7/42 Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature
• CPC Class Codes: G01N 27/3274 Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration coding of calibration information G01N33/48771

Abstract

A biosensing meter is provided that determines a value of an analyte in a biological sample. The meter employs an algorithm for determining the analyte value, which value is dependent upon ambient temperature about the biological sample when it is present in a reaction zone. The biosensing meter includes a processor and a temperature sensor. The temperature sensor is positioned within the meter'"'"'s structure and thereby exhibits a delayed response to changes in the ambient temperature. The meter performs a temperature estimation method to overcome the delayed temperature response. The method commences by the meter repetitively and periodically acquiring temperature readings from the temperature sensor when the biosensing meter is both in an on state and in an off state. When the meter is in the on state, the algorithm estimates the ambient temperature by employing at least two most recent temperature readings and extrapolating therefrom to achieve an ambient temperature estimate. Temperature readings are acquired by the meter at first intervals when the meter is in the off state and at second, shorter intervals when the meter is in the on state, the temperature extrapolations only occurring when the meter is in the on state.

Claims

1. A temperature estimation method for use in a biosensing meter that determines a value of an analyte in a biological sample, a determined analyte value dependent upon an ambient temperature about said biological sample, said biosensing meter including a processor and a temperature sensor, said temperature sensor positioned within said meter and thereby exhibiting a delayed response to changes in said ambient temperature, said temperature estimation method controlled by said processor to overcome said delayed response, and comprising the steps of:

(a) periodically acquiring temperature readings from said temperature sensor when said biosensing meter is both in an ON state and in an OFF state;

(b) when said biosensing meter is in said ON state, estimating said ambient temperature by employing at least two most recent temperature readings; and

(c) employing said ambient temperature estimated in step (b) to compensate a determined analyte value.

2. The method as recited in claim 1 wherein step b estimates said ambient temperature by using said two most recent temperature readings and extrapolating therefrom to determine said estimate of said ambient temperature.

3. The method as recited in claim 2 wherein said temperature readings are acquired at first intervals when said meter is in said OFF state, and at second, shorter intervals when said meter is in said ON state, said biosensing meter employing a temperature reading acquired when said meter is in said OFF state and a temperature reading when said meter is in said ON state to determine at least one said temperature estimate.

4. The method as recited in claim 1 wherein said estimation step is only performed when a difference between said two most recent temperature readings exceeds a threshold value, a latest temperature reading being employed as said ambient temperature when said threshold value is not exceeded.

5. The method as recited in claim 1 wherein said estimation step extrapolates said two most recent temperature readings T_old and T_new to obtain T_ambient by employing the expression:

##EQU3## Where;

m=inverse of the meter'"'"'s thermal time constant (in seconds);

Δ

t=the time in seconds between acquisition of T_new and T_old.

6. The method as recited in claim 5 wherein T_old is acquired when said meter is in said OFF state, and said meter is switched to the ON state and a T_new reading is acquired, the method comprising the added steps of:

determining an elapsed time between when T_old and T_new values are acquired;

comparing said determined elapsed time against a time threshold; and

disregarding said T_new reading when said elapsed time is not at least equal to said elapsed time threshold.

7. The method as recited in claim 5, comprising the following added steps of:

finding a temperature difference value between T_new and T_old ;

comparing said temperature difference value with a temperature difference threshold value; and

employing T_new reading as a new T_ambient value when said temperature difference value is less than said temperature difference threshold value, based upon an assumption that said biosensing meter is at a stable temperature.

8. The method as recited in claim 7 wherein said biosensing meter includes a pluggable read only memory chip, and wherein said temperature difference threshold value is acquired from said pluggable read only memory chip.

9. The method as recited in claim 5, wherein said biosensing meter operates when said T_ambient falls within set operating temperature limits.