Method of operating an optochemical sensor

• US 9,103,795 B2
• Filed: 04/08/2013
• Issued: 08/11/2015
• Est. Priority Date: 10/08/2010
• Status: Active Grant

• Current Assignee: Mettler Toledo GmbH
• Original Assignee: Mettler-Toledo AG (Mettler-Toledo International Inc.)
• Inventors: Vanoni, Claudio, Kleinlogel, Christoph, Venturini, Francesca
• Primary Examiner(s): Xu, Robert
• Application Number:
  US13/858,437
• Publication Number:
  US 20130295682A1
• Time in Patent Office: 855 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/643 non-biological material
• CPC Class Codes: G01N 21/75 Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated systems in which material is burnt in a flame or plasma G01N21/72, G01N21/73
• CPC Class Codes: G01N 21/77 by observing the effect on a chemical indicator
• CPC Class Codes: G01N 21/8507 Probe photometers, i.e. with optical measuring part dipped into fluid sample

Abstract

An optochemical sensing device has source that emits radiation of a first and a second predetermined intensity, a detector, and a sensitive element that comprises a signal substance. To measure an analyte in a measurement medium, the sensitive element is contacted with the analyte. A first raw signal, which is dependent on the analyte content is obtained by exciting the signal substance with radiation of the first predetermined intensity. At a later time, a second raw signal is also obtained. A comparison of the raw signals yields a comparison value, which is compared against a predetermined limit value. If the comparison value exceeds the limit value, the radiation source is set at the first intensity. If the comparison value is smaller than the limit value, the radiation source is set at the lower second intensity. Using the lower radiation intensity prolongs the life of the sensitive element.

Claims

1. A method for operating a device that optochemically senses an analyte, the device comprising a radiation source that emits radiation of a first and a second predetermined intensity, a detector, and a sensitive element that comprises a signal substance based upon the analyte, the method comprising the steps of:

contacting the sensitive element with the analyte, effecting interaction of the signal substance therewith;

determining a first raw signal, representing a function of the analyte content at a first point in time, by exciting the signal substance with radiation of the first predetermined intensity, generating a signal that is collected by the detector; and

iteratively controlling the device for a predetermined number of iterations, comprising the steps of;

determining a subsequent raw signal, representing a function of the analyte content at a subsequent point in time, by exciting the signal substance with radiation from the radiation source, generating a signal that is collected by the detector;

calculating a comparison value, defined as a change over time of at least two of the raw signals, by the steps of;

applying at least one filter function to convert each of the raw signals into a corresponding processed signal, the filter function having a smoothing factor that enters into the conversion; and

calculating the comparison value as a change over time of at least two of the corresponding processed signals rather than the raw signals;

comparing the calculated comparison value to a predetermined first limit value and adjusting the radiation intensity by the steps of;

when the calculated comparison value is greater than or equal to the predetermined limit value;

setting the radiation source at the first predetermined intensity; and

evaluating and adjusting the smoothing factor; and

when the calculated comparison value is smaller than the predetermined limit value and the analyte content is essentially stable;

calculating a further comparison value defined as a change over time of at least two of the raw signals;

comparing the further comparison value to a predetermined second limit value by the steps of;

 

when the further comparison value is greater than or equal to the predetermined second limit value, increasing the smoothing factor by a given increment to lessen the effect of the filter function;

or

 

when the further comparison value is smaller than the predetermined limit value, decreasing the smoothing factor by a given increment to increase the effect of the filter function, comparing the smoothing factor to a predetermined reference smoothing factor; and

, if the smoothing factor is smaller than or equal to the predetermined reference smoothing factor and the analyte content is essentially stable, setting the radiation source to the second predetermined intensity.

2. The method of claim 1, wherein:

the smoothing factor is selected and adjusted based upon the radiation intensity that is being used.

3. The method of claim 1, wherein:

the comparison value is calculated as a mean value of the two most recent processed signal.

4. The method of claim 1, wherein:

the filter function comprises an exponential smoothing.

5. The method of claim 1, further comprising the step of:

calculating the remaining service life of the sensitive element.

6. The method of claim 1, wherein:

the smoothing factor is selected and adjusted as a function of the intensity of the radiation source that was used to generate the raw signal.

7. A method for operating a device that optochemically senses an analyte in a medium, the device comprising a radiation source that emits radiation of a first and a second predetermined intensity, the second predetermined intensity being lower than the first predetermined intensity, a detector, and a sensitive element that comprises a signal substance based upon the analyte, the method comprising the steps of:

contacting the sensitive element with the medium, effecting interaction of the signal substance therewith;

determining a first raw signal, representing a function of the analyte content of the medium at a first point in time, by exciting the signal substance with the radiation source set at the first predetermined intensity, generating a signal that is collected by the detector; and

iteratively controlling an instant level of the radiation intensity based upon the analyte content of the medium, starting with the instant level at the first predetermined intensity, by the steps of;

determining at least one subsequent raw signal, each subsequent raw representing a function of the analyte content at a subsequent point in time, by exciting the signal substance with radiation at the instant level of the predetermined intensity, generating a signal that is collected by the detector;

determining the stability of the signals being obtained by the steps of;

applying at least one filter function to convert each of the raw signals into a processed signal, wherein the filter function comprises a smoothing factor;

calculating a first comparison value as a change over time of the processed signals;

calculating a second comparison value as a change over time of the raw signals; and

based upon the calculated first comparison value;

setting the instant level to the first predetermined intensity if the comparison value is equal to or exceeds a first predetermined limit value, indicating the analyte content is not stable;

or

setting the instant level at the second predetermined intensity if the first comparison value is smaller than the first predetermined limit value, indicating the analyte content is stable; and

adjusting the smoothing factor based on a comparison of the calculated second comparison value to a second predetermined limit value.