Sensor calibration

• US 20090093985A1
• Filed: 05/16/2006
• Published: 04/09/2009
• Est. Priority Date: 05/17/2005
• Status: Active Grant

• Current Assignee: Toumaz Technology Ltd.
• Original Assignee: Toumaz Technology Ltd.
• Inventors: Burdett, Alison, Padden, Paul
• Granted Patent: US 7,711,506 B2
• Time in Patent Office: Days
• US Class Current: 702/104
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2560/0412 Low-profile patch shaped housings
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes

Abstract

A method of calibrating a sensor system comprising a disposable sensor and a computer device, both the sensor and the computer device having circuitry for facilitating the transmission of data between them via a wireless communication link. The method comprises storing a final value of a monitored parameter obtained using a first disposable sensor, or some other value derivable from said final value, in a memory of the computer device, and calibrating the system for a new disposable sensor using said final value or said other value.

Claims

1. A method of calibrating a sensor system comprising a disposable sensor and a computer device, both the sensor and the computer device having circuitry for facilitating the transmission of data between them via a wireless communication link, the method comprising:

storing a final value of a monitored parameter obtained using a first disposable sensor, or some other value derivable from said final value, in a memory of the computer device; and

calibrating the system for a new disposable sensor using said final value or said other value.

2. A method according to claim 1 and comprising using said final value or other value to compute a calibration factor for the new sensor.

3. A method according to claim 2, where said factor is a constant used to evaluate the parameter being monitored from a measured value.

4. A method according to claim 1, wherein the final value or said other value, or said calibration factor, is sent from the computer device to the disposable sensor where evaluation of the monitored parameter, or a part of the evaluation, is carried out at the sensor.

5. A method according to claim 1, wherein the final value or said other value, or said calibration factor, is stored at the computer device where evaluation of the monitored parameter, or a part of the evaluation, is carried out.

6. A method according to claim 1, wherein said sensor is wearable.

7. A method according to claim 1, wherein said sensor is a pH sensor.

8. A method according to claim 1, wherein said sensor is an ISFET based biosensor, and the measured value is the gatesource voltage of the ISFET or the voltage or current through the drain/source.

9. A method according to claim 1, wherein the system is arranged in use to determine a blood glucose level.

10. A method according to claim 9, wherein said final value is a blood glucose level.

11. A method according to claim 9, wherein blood glucose level is a function of pH, the pH being derivable from the equation:

VT=Vos+2.3′

a−

Vth′

pH

where Vth=thermal voltage=kT/q, and Vos is a process and chemical dependent offset voltage which differs from device to device, and a is a temperature and device dependent constant,

the step of calibrating the system comprising determining Vos based upon measurements made with the new sensor and the final pH value obtained for the previous sensor.

12. A method according to claim 1, said step of calibrating the system for a new disposable sensor being carried out upon power-up of the disposable patch.

13. A sensor system comprising:

a disposable sensor, at least a portion of which is arranged in use to come into contact with a substance; and

a computer device,

both the sensor and the computer device having circuitry for facilitating the transmission of data between them via a wireless communication link, the computer device further comprising a memory for storing a final value of a parameter being monitored, or some other value driveable from said final value, for a first disposable sensor, and processing means for using said final or other value to calibrate a new disposable sensor.

14. A system according to claim 13, the system being arranged in use to determine the blood glucose level of a user.

15. A system according to claim 13, the disposable sensor comprising means for signalling to the computer device that calibration is required, said step of calibrating the system being carried out upon receipt by the computer device of the signalled information.

16. A system according to claim 13, the disposable sensor comprising means for receiving said final value of the parameter being monitored from the computer device over the wireless link.