Calibration of sensors or measuring systems

• US 8,880,371 B2
• Filed: 07/26/2006
• Issued: 11/04/2014
• Est. Priority Date: 01/27/2004
• Status: Active Grant

• Current Assignee: Roche Diabetes Care Inc. (Roche Holding AG)
• Original Assignee: Roche Diagnostics International AG (Roche Holding AG)
• Inventors: Beyer, Uwe, Krieftewirth, Michael, Haueter, Ulrich
• Primary Examiner(s): CANELLA, KAREN A
• Application Number:
  US11/460,160
• Publication Number:
  US 20070168145A1
• Time in Patent Office: 3,023 Days
• Field of Search: None
• US Class Current: 702/87
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• CPC Class Codes: C12Q 1/006 for glucose
• CPC Class Codes: G01N 33/5438 Electrodes

Abstract

A method for adjusting a sensor, continuous sensor or automatic measuring system in an interstitium including the steps of adjusting the steepness of a measuring curve and a standard offset (standard axis intercept) prior to the use of the sensor, continuous sensor or measuring system, and adapting the offset by a point calibration by using a reference measure or value during the use. The present invention encompasses sensors, continuous sensors or automatic measuring systems calibrated or adjusted in accordance with the method, and in some embodiments, the offset adjusted prior to use is rectified according to the difference between a value determined by the sensor, continuous sensor or measuring system taking into account the standard steepness and the reference value.

Claims

1. A measuring system for determining a value of a glucose concentration, the measuring system comprising:

a. a measuring sensor (2, R_m, R_ref), having a known gradient and a known offset, for recording a measured value in vivo in a temporally sequential or continuous fashion, and outputting measuring sensor values (P1, P2), the measured values of the measured variable or formed from the measured values, and

b. a data acquisition device that receives the measuring sensor values and at least one reference value and forms characteristic values of the glucose concentration from the measuring sensor values, wherein the measuring sensor is a glycose sensor and the at least one reference value is a long-term glycose value, and wherein the data acquisition device creates a long-term glucose value from the at least one reference value and calculates a daily mean or a multiple daily mean of the glucose concentration from the measuring sensor values, and the offset is corrected in accordance with the result of the comparison of the daily mean or multiple daily mean with the long-term glucose value to minimize the difference between the daily mean or multiple daily mean and the long-term glucose value; and

wherein

c. for the purpose of an automatic self-calibration of the measuring system, the data acquisition device compares the at least one reference value or a value calculated therefrom with the characteristic value from the corresponding time interval, and the offset of the measuring sensor is adjusted in accordance with the result of the comparison by a one-point calibration.

2. The measuring system as claimed in claim 1, wherein the measuring sensor comprises a dialysis probe.

3. The measuring system as claimed in claim 1, wherein the measuring sensor comprises a probe that can be placed in a body and a conveyor device by which a liquid can be conveyed through, only into or only out of the probe.

4. The measuring system as claimed in claim 1, wherein the measuring sensor comprises a flow resistance zone (R_ref) and the measured variable recorded by the measuring sensor is a pressure of a fluid flowing through the flow resistance zone.

5. The measuring system according to claim 4, wherein the flow resistance zone comprises a flow resistance capillary.

6. The measuring system as claimed in claim 4, wherein a pressure is measured at an upstream inlet and a downstream outlet of the flow resistance zone (R_ref), and the pressure values are transmitted to the data acquisition device.

7. The measuring system as claimed in claim 1, wherein the measuring sensor comprises a dialysis chamber through which a sensitive liquid can flow, a flow resistance zone arranged upstream of the dialysis chamber, a flow resistance zone arranged downstream of the dialysis chamber, a pressure transmitter upstream of one of the flow resistance zones, and a pressure transmitter downstream of that one of the flow resistance zones, one of the pressure transmitters being arranged between the flow resistance zones, wherein pressure values recorded by the pressure transmitters are transmitted to the data acquisition device.

8. The measuring system as claimed in claim 7, wherein the data acquisition device calculates from the pressure values a relative fluidity F_r using

F_r=(P1−

P2)/(P2+α

(P1−

P2)),

P1 being the pressure value of the upstream pressure transmitter, P2 being the pressure value of the downstream pressure transmitter and a being a linearization coefficient.

9. The measuring system as claimed in claim 8, the data acquisition device calculates a concentration of a substance in a fluid from the relative fluidity F_r by using the formula

[KONZ]=gain*F_r+offset.

10. The measuring system as claimed in claim 9, wherein the data acquisition device calculates a trend using measuring sensor values, and determines an instant for the calibration from the calculated trend.

11. The measuring system as claimed in claim 1, wherein the data acquisition unit comprises a data memory for a number of the measuring sensor values, and a clock to assign the measuring sensor values the respective instant of their recording.

12. The measuring system as claimed in claim 1 further comprising a reference unit for recording the measured variable or another measured variable, and for outputting the at least one reference value determined from the measured variable or the other measured variable.

13. The measuring system as claimed in claim 12, wherein the reference unit automatically transmits the at least one reference value to the data acquisition device in a wireless fashion or by wire per data transmission.

14. A measuring system for determining a value of a glucose concentration, the measuring system comprising:

a. a measuring sensor (2, R_m, R_ref), having a known gradient and a known offset, for recording a measured value in vivo in a temporally sequential or continuous fashion, and outputting measuring sensor values (P1, P2), the measured values of the measured variable or formed from the measured values, wherein the measuring sensor is a viscosimetric affinity sensor, and

b. a data acquisition device that receives the measuring sensor values and at least one reference value and forms characteristic values of the glucose concentration from the measuring sensor values, wherein the measuring sensor is a glycose sensor and the at least one reference value is a long-term glycose value, and wherein the data acquisition device creates a long-term glucose value from the at least one reference value and calculates a daily mean or a multiple daily mean of the glucose concentration from the measuring sensor values, and the offset is corrected in accordance with the result of the comparison of the daily mean or multiple daily mean with the long-term glucose value to minimize the difference between the daily mean or multiple daily mean and the long-term glucose value; and

wherein

c. for the purpose of an automatic self-calibration of the measuring system, the data acquisition device compares one of the characteristic values with the at least one reference value or a value calculated therefrom with the characteristic value from the corresponding time interval, and the offset of the measuring sensor is adjusted in accordance with the result of the comparison by a one-point calibration.