METHOD FOR DEGRADATION-COMPENSATED EVALUATION OF LUMINESCENCE SENSOR DETECTION SIGNALS AND EVALUATION DEVICE THEREFOR

Description

[0001] The present invention relates to a method for degradation-compensated evaluation of detection signals from a sensor arrangement operating according to the principle of luminescence quenching. The present invention also relates to an evaluation device designed to carry out such a method. A sensor arrangement operating according to the principle of luminescence quenching comprises a luminophore, an excitation radiation source, and at least one optical sensor. In response to irradiation with a predetermined modulated excitation radiation, the luminophore emits response radiation in accordance with a response characteristic typical of the sensor arrangement, which is detected by the at least one optical sensor. The response radiation depends not only on the excitation radiation from the excitation radiation source, but also on the extent of interaction between the luminophore and a quencher substance.The quencher substance, such as oxygen, has the property of quenching the luminescence of the luminophore. The luminescence of the luminophore evoked by the excitation radiation therefore decays more rapidly in the presence of the quencher substance interacting with the luminophore than it would in the absence of the quencher substance. The response characteristic is the material-inherent relationship between the excitation radiation and the response radiation of the given luminophore, which depends on the extent of the interaction with the quencher substance.

[0002] Typically, such sensor arrays are used for measurement purposes to not only detect but also quantify the presence of a specific quencher substance. For example, if oxygen is a quencher substance for a given luminophore, the sensor array can be used to determine the oxygen content or oxygen concentration in a test fluid under test. To do this, the test fluid must be brought into luminescence-quenching interaction with the luminophore; in the case of collision quenching, for example, this requires physical contact with the luminophore.

[0003] Due to the luminescence quenching caused by the quencher substance, a phase angle of a phase shift between the modulated excitation radiation and a thus necessarily modulated response radiation changes depending on the concentration of the quencher substance in the test fluid. Using a form of the known Stern-Volmer equation that takes the phase angle between the excitation and response radiation into account, a concentration of the quencher substance can be determined from a phase angle of the response radiation determined for a known excitation radiation, for example, in the form of a partial pressure of the quencher substance in the test fluid.

[0004] Due to the luminescence quenching caused by the quencher substance, the intensity of the response radiation changes for a given excitation radiation depending on the concentration of the quencher substance in the test fluid. Using a form of the Stern-Volmer equation that takes the intensity of the response radiation into account, the concentration of the quencher substance can also be determined from the intensity of the response radiation determined for a known excitation radiation.

[0005] Detection signals from the sensor array therefore usually represent either a phase angle or an intensity of the response radiation.

[0006] Based on a calibration of the sensor array performed prior to a specific detection process, a detection signal based on the response radiation detected by the optical sensor can generally be assigned a result value that represents the desired result, for example, a concentration of a predetermined quencher substance in a test fluid, such as the oxygen partial pressure in a test fluid. Thus, during the calibration of the sensor array, a calibration value relationship is generally determined, which links values ​​of the detection signal based on the response radiation to result values.

[0007] The aim of evaluating detection signals from a sensor arrangement operating according to the principle of luminescence quenching is to determine the result value aimed at by the detection process.

[0008] The problem is that a luminophore degrades over time, for example, through bleaching. As the luminophore used in a sensor array degrades, the response radiation emitted by the luminophore in response to the excitation radiation changes, assuming constant excitation radiation and a constant concentration of the quencher substance in the test fluid. In the terminology used above, this means that the material-inherent response characteristics of the luminophore change due to degradation.

[0009] In the present application, the mention of a degradation of the luminophore is synonymous with the mention of a degradation of the sensor arrangement.

[0010] As the luminophore degrades, the difference between the current response characteristic at the respective acquisition time and the reference response characteristic prevailing during calibration, which forms the basis of the still valid calibration value relationship, increases. As a result, the result values ​​determined using current acquisition signals and a previous calibration increasingly deviate from the true value. In the case of bleaching, a very common form of degradation, for example, this results in detection values ​​that are too low. Because the luminophore's luminescence quenching property means that decreasing detection values ​​are associated with increasing quencher substance concentrations as result values, the degradation of the luminophore generally leads to the determination of result values ​​that are too high in magnitude.

[0011] When used as intended to determine result values, the calibrated sensor array always delivers some detection value based on the applicable response characteristic and subsequently some result values ​​from the detection values ​​based on the applicable calibration-value relationship. The state of the art does not allow the user of the sensor array to determine whether a high result value is the result of luminophore degradation or an actually high concentration of the quencher substance.

[0012] One approach to avoid degradation-related errors in the determination of result values ​​is to calibrate the sensor array as frequently as possible, thus adjusting the reference response characteristic underlying the calibration to the current response characteristic, which changes due to luminophore degradation. However, due to the time required for calibration, this significantly reduces the productivity of the sensor array.

[0013] Another approach involves correcting the incorrect results caused by degradation. A proposal for this is known from EP 2 887 054 A1.

[0014] This publication teaches how to correct for luminophore degradation in the Stern-Volmer equation used to evaluate the sensor array detection signal. The Stern-Volmer equation is used in a form that uses the detected phase angle as an argument.

[0015] EP 2 887 054 A1 proposes modifying both the phase base value of the Stern-Volmer equation, i.e., the phase angle determined in the absence of the quencher substance with a new, non-degraded luminophore, and the Stern-Volmer constant used in the equation by respective aging factors. The aging factors, in turn, depend on the frequency of the excitation radiation modulation. Due to their dependence on the sensor structure, they are very complex to determine empirically for each sensor type and, due to their frequency dependence, for multiple frequencies of the excitation radiation modulation.

[0016] The Stern-Volmer equations used in EP 2 887 054 A1 are degradation-corrected using exponential functions. Different exponential functions are multiplied as correction factors by the phase base value and by the Stern-Volmer constant. The respective aging factors are part of the exponent of the exponential functions. Due to the resulting equation structure, for degradation correction according to EP 2 887 054 A1, a system of equations must be solved numerically for each acquisition process. This either requires the provision of an evaluation device with unusually high computing power or, with conventional computing power, delays the acquisition process until the desired result value is obtained. Furthermore, the degradation correction proposed in EP 2 887 054 A1 depends on the operating time of the sensor, which is not necessarily the case in reality.

[0017] Document GB 2 496 657 A discloses the subject matter of the preamble of claim 1 and an apparatus for carrying out this method; this document cites as prior art documents GB 2 479 183 A, GB 2 380 790 A, WO 2007 / 066126 A1, WO 2004 / 077035 A1, DE 197 09 377 A1, JP 2010-133725 A, US 7,926,322 B1, US 5,030,420 A and US 2011 / 0184259 A1.

[0018] US 7,926,322 B1 discloses the subject matter of the preamble of claim 1 and an apparatus for carrying out this method; this document cites US 5,060,505 A, US 5,887,048 A, US 6,205,272 B1, US 2006 / 0018045 A1, and US 5,030,420 A as prior art.

[0019] US 2008 / 0085217 A1 discloses a luminescence sensor arrangement for a ventilation device for the luminescence-based detection of components of a measurement gas. The known luminophore is irradiated with amplitude-modulated excitation radiation and consequently emits amplitude-modulated response radiation. Based on the excitation radiation and response radiation, a phase difference between these radiations is determined, based solely on this phase difference, which is used to determine the proportion of the luminescence-quenching component in the measurement gas.

[0020] The phase difference is compensated for by a degradation of the luminophore determined exclusively on the basis of time.

[0021] The object of the present invention is therefore to provide a technical teaching which makes it possible to eliminate as far as possible the influence of luminophore degradation on the evaluation of detection signals of a sensor arrangement operating according to the principle of luminescence quenching with less effort than before and, if possible, with greater accuracy.

[0022] This object is achieved according to the invention by a method according to claim 1, an evaluation device according to claim 6 and a measuring arrangement according to claim 11. Preferred embodiments of the invention are described in the subclaims.

[0023] This object is achieved according to the present invention, in particular, by a method for degradation-compensated evaluation of detection signals from a sensor arrangement operating according to the principle of luminescence quenching, which sensor arrangement comprises a luminophore that degrades over time, an excitation radiation source, and at least one optical sensor. In response to irradiation with a predetermined modulated excitation radiation, the luminophore emits response radiation detected by the at least one optical sensor depending on the extent of interaction of the luminophore with a quencher substance that quenches the luminescence of the luminophore, according to a response characteristic typical of the sensor arrangement.The sensor arrangement outputs, as detection signals, a detected intensity value representing an intensity of the response radiation and a detected phase value representing a phase difference of the response radiation with respect to the modulation of the excitation radiation. For a successful detection of response radiation, a deviation in the magnitude of one of the detected values ​​from the detected intensity value and the detected phase value, wherein the deviation is based on a degradation-based change in the response characteristic at the time of the successful detection with respect to a reference response characteristic that forms the basis for a calibration of the sensor arrangement, is reduced in magnitude according to both the detected intensity value and the detected phase value. Thus, a degradation-compensated detected value is determined.A result value of the detection related to the quencher substance is then determined according to a predetermined calibration value relationship determined taking into account the reference response characteristic on the basis of the degradation-compensated detected value.

[0024] Unlike EP 2 887 054 A1, the evaluation method of the present invention, to compensate for luminophore degradation, extremely advantageously uses not only the detected phase value or the detected intensity value, but also both values ​​obtainable during detection: phase value and intensity value. Quite surprisingly, it was discovered that for one and the same sensor arrangement operating according to the principle of luminescence quenching, the intensity value and the phase value are clearly related in each degradation state. The intensity value, represented as a function of the phase value, has a continuous, sufficient, and unambiguous graph as an image. Of course, the same applies to the phase value as a function of the intensity value.Thus, for one and the same sensor arrangement, a sufficient and unambiguous relationship between the phase value and the intensity value of a response radiation is assigned for a given excitation radiation and for different concentrations of quencher substance in a test fluid.

[0025] Surprisingly, this also applies regardless of whether the concentration of the quencher substance in a test fluid to be monitored by the sensor arrangement or, for example, the temperature of the test fluid and / or the sensor arrangement changes. For a sensor arrangement calibrated on the basis of a reference response characteristic prevailing at the time of calibration, preferably a brand-new sensor arrangement, an intensity value is always uniquely assigned to a phase value for each concentration of the quencher substance in the test fluid and for each temperature of the test fluid, and vice versa. By changing the concentration of the quencher substance and / or by changing the temperature of the test fluid, the recorded values ​​obtained during a recording process only shift along the relationship, but do not depart from it.In the following, this relationship between phase value and intensity value for different concentrations of quencher substance in the test fluid and, if applicable, for different test fluid temperatures is referred to briefly as relationship or phase value-intensity value relationship.

[0026] This unambiguous relationship between phase value and intensity value for a given response radiation and for a test fluid with different concentrations of quencher substance is an example of a response characteristic of the sensor arrangement or of a sensor arrangement of the same type in terms of design and luminophore. Due to the unambiguous nature of the relationship, it is irrelevant whether the intensity value is viewed as a function of the phase value or whether the phase value is viewed as a function of the intensity value. As will be seen below from the exemplary embodiment, it may be more practical to use the detection value that is the input variable for applying the calibration value relationship to calculate the result value as the base detection value, and to view or use the other detection value as a function of the base detection value.

[0027] As explained above, by only considering a single acquired detection signal or value—that is, by considering either only the phase value or only the intensity value—it is impossible to determine whether this value is correct or corrupted because the current response characteristic of the sensor arrangement differs from the reference response characteristic on which the sensor arrangement's calibration value relationship is still based due to degradation of the luminophore. However, according to the present invention, by simultaneously considering both the phase value and the intensity value, it is very possible to determine whether, for example, the detection is based on a degraded luminophore or on a luminophore corresponding to the calibration used.

[0028] To determine the result value, one of the two recorded values, namely the phase value and the intensity value, is still sufficient. However, both values ​​are required to determine whether the response characteristic of the luminophore of the sensor arrangement sufficiently corresponds to the reference response characteristic underlying the calibration used or whether it has since changed due to degradation of the luminophore. If the value pair consisting of the phase value and the intensity value lies outside a generally freely but reasonably selectable predefined tolerance range around the known relationship between the phase value and the intensity value of the sensor arrangement in its last calibration state (calibration state), the luminophore has degraded beyond the tolerance threshold underlying the predefined tolerance range.Graphically represented, the acquisition value pair consisting of phase value and intensity value lies in a two-dimensional Cartesian coordinate system, whose axes represent the phase value and the intensity value, away from the continuous curve representing the relationship between phase value and intensity value in the calibration state of the sensor array for different concentrations of quencher substance in the test fluid. The calibration state is the state of the sensor array at the time of the last calibration, i.e., the calibration currently in use.

[0029] Furthermore, it was discovered, quite surprisingly, that the relationship between the phase value and the intensity value of a sensor arrangement is clear and sufficient even in a degradation state that deviates from the calibration state, but is different from the phase value-intensity value relationship of the calibration state. Viewed graphically, the pairs of recorded values ​​of the phase value and the intensity value of a sensor arrangement for different concentrations of the quencher substance in the test fluid and / or for different temperatures of the test fluid lie in a Cartesian coordinate system with the axes mentioned for the calibration state and for each degradation state on a clear, continuous curve and / or can be described by a clear equation, whereby the individual curves of the different degradation states have a similar shape orhave a similar course to each other, but are shifted and / or inclined relative to each other.

[0030] If the respective relationships between phase values ​​and intensity values ​​for different degradation states are known for a given sensor arrangement or a given type of sensor arrangement, the degradation state can be determined from a pair of phase values ​​and intensity values ​​obtained during a detection – if necessary using extrapolation or interpolation – and from this, the corresponding theoretical pair of phase values ​​and intensity values ​​can be determined, which would have been output as detection signals (detection value pair) under otherwise identical detection conditions in the calibration state. Instead of a pair of values, only one value consisting of the phase value and intensity value of this theoretical pair can be output.This value: phase value or intensity value, of the theoretical value pair is therefore a degradation-compensated value, on the basis of which the actually desired result value can be determined with the already existing calibration value relationship.

[0031] The relationships between intensity values ​​and phase values ​​for different concentrations of the quencher substance in the test fluid and / or for different temperatures of the test fluid in different degradation states, from brand-new / undegraded to fully degraded, can be empirically determined on one or more sensor arrays of the same type and then stored in a data storage device for this type of sensor array. In principle, a single calibration of the sensor array, for example, at the beginning of its commissioning, may then be sufficient because subsequent detection results in degradation states can be traced back to the calibration state using the known empirically determined relationships, if necessary with the aid of extrapolation or interpolation.After such a determination of the degradation-compensated recorded value, a sufficiently correct result value can be determined based on the currently used calibration value relationship.

[0032] Starting from the empirically determined value pair relationships, a function or equation system can be developed from the value pair relationships to facilitate the determination of the degradation-compensated recorded value. This system facilitates the computational determination of the degradation-compensated recorded value. For example, iso-concentration relationships or functions or traces or curves can be determined across several intensity value-phase value relationships of the calibration state and the individual degradation states. These iso-concentration relationships or functions or traces or curves can be determined, which, for a given temperature of the test fluid, connect those value pairs of intensity value and phase value that are each assigned to the same concentration of the quencher substance at different degradation states of the sensor arrangement type. These can be used for concentrations of the quencher substance in steps of predetermined step widths, for example, when specifying the concentration in vol.% or wt.-% every 10 percentage points, can be determined experimentally. These functions can also be stored in the data memory of an evaluation device. Intermediate concentration values ​​for which no functions have been determined are calculated by extrapolation or interpolation.

[0033] Such a family of functions or equations can, in turn, be determined for several relevant test fluid temperatures, so that a degradation-compensated recorded value can also be correctly calculated from acquisition signals for acquisition processes with different test fluid temperatures. Acquisition signals from acquisition processes obtained at test fluid temperatures deviating from these test fluid temperatures can be processed by extrapolation or interpolation.

[0034] Such systems of functions or equations, or families of systems of functions or equations, generally form a compensation-value relationship that links recorded intensity and phase values ​​with a degradation-compensated recorded value. This compensation-value relationship can be represented graphically as curves or sets of curves, analytically as a system of equations or sets of equation systems, or in tabular form and stored in a data storage device. Analytical representations of the compensation-value relationship can be obtained by fitting equations to sets of points obtained through experimental measurements and / or theoretical considerations, for example, using a least-squares method.

[0035] A compensation value relationship can also be provided by only a single function or curve or table, as will be shown below.

[0036] Therefore, according to a further development of the present invention, the method according to the invention comprises the step of determining the degradation-compensated detected value based on a predetermined compensation value relationship with input variables based on the detected intensity value and the detected phase value. Since one detected value is sufficient to determine the result value, for a detection process, preferably only exactly one detected value from the detected intensity value and the detected phase value is degradation-compensated based on a predetermined compensation value relationship based on both the detected intensity value and the detected phase value.

[0037] However, the above method can be simplified in an extremely advantageous way by considering the above-described relationships between phase value and intensity value for different concentrations of quencher substance in a test fluid at a given excitation radiation, and thus the response characteristic, not in a dimensioned space, but in a dimensionless space and using this for at least part of the evaluation. It has been shown that the functions of the relationships between phase value and intensity value for one and the same sensor arrangement type in the calibration state always form the same dimensionless phase value-intensity value relationship. In dimensioned space, it is possible to ensure through calibration that the response characteristic of a sensor arrangement for a detection process corresponds to the reference response characteristic for sensor arrangements of one and the same sensor arrangement type.Depending on the degradation state of the sensor array, the individual reference response characteristics associated with the different degradation states differ from one another.

[0038] Quite surprisingly, it has been shown that regardless of the physical degradation state of a sensor array, its reference response characteristics are always the same in dimensionless notation. Due to degradation of the luminophore since the last calibration, the current response characteristics increasingly differ from the reference response characteristics that formed the basis for the creation of the calibration value relationship, even in dimensionless notation. However, a recalibration of the sensor array in dimensionless notation does not lead to a new dimensionless reference response characteristic—as would be the case in dimensioned notation—but rather leads back to the already known dimensionless reference response characteristic. This enormously simplifies the computing power and infrastructure required for degradation compensation.

[0039] This circumstance makes it particularly advantageous that a single equation or function is sufficient as a compensation value relationship to determine the degradation-compensated detection value.

[0040] This effect is based on the physical and computational theory of the fact that, although the degradation of the luminophore changes its performance, the technical processes and effects underlying this performance remain unchanged. The differences dependent on the degradation state can be "cancelled out" if both the recorded intensity value and the recorded phase value are transformed into a dimensionless recorded intensity value or a dimensionless recorded phase value using at least one system parameter characterizing the sensor arrangement and / or at least one process parameter originating from the recording process. While such a transformation is not absolutely necessary to achieve the advantages of the present invention, the advantages can be achieved more quickly, with less computing infrastructure, and with greater accuracy using dimensionless notation of the recording processes.

[0041] In terms of similarity theory, the transition in the observation and data processing of a technical process from a dimensioned to a dimensionless notation means the transition from a standard normal system foreign to the notated process, such as the SI unit system, to a process-specific coordinate or normal system. This is well known from fluid mechanics. For example, flows with the same absolute value of the dimensionless Reynolds number behave completely identically with regard to certain fluid mechanics effects, regardless of the flowing medium, the specific flow velocity, and the dimensions of the flow. In dimensioned notation, such as the SI unit system, these flows would be described by the same basic equations but with completely different parameter values. In the system-specific dimensionless notation, they are all described by the same value of the same absolute value.

[0042] The same applies in this case to sensor arrangements of the same type, although the formation of far less complex dimensionless quantities is sufficient here. For example, each recorded phase value can be converted into a dimensionless phase value by division by a reference phase value predetermined and quantified experimentally. The predetermined and quantified reference phase value can, for example, be the phase value that the sensor arrangement delivers at a predetermined quencher concentration in the test fluid, for example at a quencher content of 50 vol% or wt% or at a predetermined quencher partial pressure. The same applies mutatis mutandis to the transformation of the recorded intensity value, whereby the reference phase value and the reference intensity value are preferably determined at the same quencher concentration.

[0043] For better comparability and thus easier data processing of the recorded values: phase value and intensity value, these are preferably transformed into a dimensionless, standardized recorded intensity value and a dimensionless, standardized recorded phase value. This can be achieved by first subtracting a predetermined extreme value from the respective recorded value, such as the recorded value at the maximum concentration of the quencher substance, i.e., when using the pure quencher substance as the test fluid. For sensor arrangements operating according to the principle of luminescence quenching, this is usually a minimum recorded value in terms of absolute value. The resulting difference is then divided by the absolute value of the maximum possible achievable recorded value range of the sensor arrangement or sensor arrangement type.This range, in turn, is a differential value and is determined by calculating the difference between the detection value, usually the maximum value, at the minimum concentration of the quencher substance (i.e., using a test fluid completely free of the quencher substance), and the detection value at the maximum concentration of the quencher substance. These latter differential values, which describe the respective maximum possible value range of the respective detection value, are then the above-mentioned reference phase value for the phase value as the detection value, and the reference intensity value for the intensity value as the detection value.

[0044] The determination of the reference phase value and the reference intensity value is preferably carried out immediately after the calibration in order to ensure that the current response characteristic of the sensor arrangement corresponds to the reference response characteristic on which the calibration is based.

[0045] In the case of dimensionless normalization of the acquisition signals, these always have values ​​between 0 and 1.

[0046] Then, the predetermined compensation value relationship is preferably a predetermined dimensionless compensation value relationship, so that the dimensionless, standardized detection value can be compensated for any degradation of the luminophore directly and without prior conversion back into a dimensioned value. According to the dimensionless compensation value relationship, the degradation-compensated detected value can be determined using input variables based on the dimensionless, preferably standardized, detected intensity value and the dimensionless, preferably standardized, detected phase value. The degradation-compensated detection value is then preferably also a dimensionless, particularly preferably a dimensionless, standardized degradation-compensated detected value or detection value.

[0047] If the degradation-compensated detected value is a dimensionless, preferably a dimensionless standardized, degradation-compensated detected value, it can either be converted into a dimensioned degradation-compensated detected value, and the result value can then be determined using an input variable based on the degradation-compensated value and the predetermined calibration-value relationship. Or the predetermined calibration-value relationship is designed to determine the result value directly using an input variable based on the dimensionless, preferably dimensionless standardized, degradation-compensated detected value. For this purpose, the predetermined calibration-value relationship can, but does not have to, be a dimensionless, preferably a dimensionless standardized, predetermined calibration-value relationship.

[0048] The term "input based on a value" includes both the value itself and a function value of a function whose argument is the value.

[0049] Not only are the dimensionless reference response characteristics of one and the same sensor array or one and the same sensor array type identical regardless of the degradation state of the sensor array. The dimensionless response characteristics of one and the same sensor array or one and the same sensor array type are also identical for the same degradation state with respect to the calibration state of the currently used calibration value range over a wide range of the useful operating lifetime of a sensor array. Therefore, using a dimensionless compensation value relationship, degradation compensation of the detection value can be performed without first having to determine whether the sensor array is degraded or not. The dimensionless compensation value relationship is simply applied to the currently obtained dimensionless detection value pair.It is sufficient that the dimensionless compensation value relationship maps one acquisition value of the acquisition value pair back to the known degradation-invariant dimensionless reference response characteristic. The dimensionless compensation value relationship can therefore be a mapping rule that maps only one of the two acquired values, both of which lie outside the degradation-invariant relationship between dimensionless intensity value and dimensionless phase value representing the reference response characteristic due to aging or degradation of the luminophore, to the known degradation-invariant phase value-intensity value relationship based on both acquired values.

[0050] In principle, the degradation-compensated recorded value can be either a degradation-compensated recorded phase value or a degradation-compensated recorded intensity value. Since previous experience has shown that the phase value provoked by modulating the excitation radiation provides the result value with greater accuracy when evaluated, the degradation-compensated recorded value is preferably the degradation-compensated recorded phase value. This applies regardless of the notation of the recorded value in a dimensioned, dimensionless, or standardized value space.

[0051] The above-mentioned object is also achieved by an evaluation device which is designed to carry out the method described above. The evaluation device is thus designed for the degradation-compensated evaluation of detection signals from a sensor arrangement operating according to the principle of luminescence quenching, comprising a luminophore which degrades over time, an excitation radiation source and at least one optical sensor. The luminophore, in response to irradiation with a predetermined modulated excitation radiation, emits a response radiation detected by the at least one optical sensor depending on the extent of interaction of the luminophore with a quencher substance which quenches a luminescence of the luminophore in accordance with a response characteristic typical of the sensor arrangement. The evaluation device has a data input channel which is designed toto transmit from the sensor arrangement as detection signals the detected intensity value representing an intensity of the response radiation and the detected phase value representing a phase difference of the response radiation with respect to the modulation of the excitation radiation to a data processing unit of the evaluation device, wherein the data processing unit has a data memory for storing data and a computing unit for processing data, wherein at least the predetermined calibration value relationship determined taking into account the reference response characteristic is stored in the data memory, wherein the evaluation device is designed toto determine the degradation-compensated recorded value from the recorded intensity value and the recorded phase value in accordance with both the recorded intensity value and the recorded phase value, and to determine and output the result value of the recorded measurement related to the quencher substance in accordance with the calibration value relationship based on the degradation-compensated recorded value.

[0052] The computing unit can be implemented by a microcomputer, an integrated circuit, and the like. The evaluation device can be a computer with a data processing program that can be executed thereon and is stored in a data memory that is connected to the computing unit for data transmission. The above advantageous developments of the method are also developments of the evaluation device for implementing the method.

[0053] According to the embodiments of the method according to the invention, the evaluation device can additionally or alternatively be configured to determine, by comparing a pair of detection signals assigned to a detection process with the reference response characteristic stored in the data memory, on which the currently used calibration value relationship is based, whether the luminophore of the sensor arrangement has degraded beyond a predefined tolerance threshold. This is always the case when the pair of detection signals in the coordinate plane defined by the phase value and intensity value is located outside a predetermined tolerance band around the phase value-intensity value relationship, which represents the reference response characteristic.The tolerance threshold can be 0, but is preferably different from 0 in terms of absolute value, since the phase value-intensity value relationship is a relationship interpolated between individual support values ​​and only provides an approximate relationship within the interpolation range itself. The evaluation device preferably issues a warning if it detects degradation of the luminophore that exceeds the predetermined tolerance threshold. The detection of degradation that is no longer tolerated can be based on the processing of dimensioned and / or dimensionless and / or standardized values ​​as data.

[0054] According to a preferred development of the evaluation device, the predetermined compensation value relationship is also stored in the data memory. The computing unit is preferably configured to determine the degradation-compensated detected value in accordance with the predetermined compensation value relationship with input variables based on the detected intensity value and the detected phase value.

[0055] According to an even more preferred development, the evaluation device can be designed to transform both the detected intensity value and the detected phase value using at least one system parameter characterizing the sensor arrangement and / or at least one process parameter originating from the detection process into a dimensionless detected intensity value, preferably into a dimensionless standardized detected intensity value, and into a dimensionless detected phase value, preferably into a dimensionless standardized detected phase value, wherein the predetermined compensation value relationship is a predetermined dimensionless compensation value relationship, according to which input variables based on the dimensionless detected intensity value and the dimensionless detected phase value, the, preferably dimensionless, particularly preferably dimensionless standardized,degradation-compensated recorded value is determined.

[0056] According to the above description of the method, the degradation-compensated detected value can be a dimensionless, preferably a dimensionless standardized, degradation-compensated detected value, and the predetermined calibration-value relationship can be a dimensionless, preferably a dimensionless standardized, predetermined calibration-value relationship. The evaluation device is then preferably designed to determine the result value in accordance with the, preferably dimensionless, calibration-value relationship with an input variable based on the dimensionless degradation-compensated value. Alternatively, the evaluation device can be designed to convert a dimensionless, preferably dimensionless standardized degradation-compensated value into a dimensioned degradation-compensated value and to calculate the result value based on this value using the calibration-value relationship.

[0057] The above-mentioned object is also achieved by a measuring arrangement comprising an evaluation device designed as described above and a sensor arrangement with a luminophore that degrades over time, with an excitation radiation source and with at least one optical sensor, wherein the luminophore emits a response radiation detected by the at least one optical sensor in response to irradiation with a predetermined modulated excitation radiation depending on the extent of contact of the luminophore with a quencher substance that quenches a luminescence of the luminophore according to a response characteristic typical of the sensor arrangement.

[0058] The present invention is explained in more detail below with reference to the accompanying drawings. It shows: Figure 1 is a partial exploded view of a housing of a sensor arrangement operating according to the principle of luminescence quenching, Figure 2 is a roughly schematic cross-sectional view through a sensor arrangement of the present invention, Figure 3 is a plot of an intensity of a response radiation of the sensor arrangement of Fig. 2 as a function of the phase shift or the phase angle, Figure 4 a plot of the intensity of a response radiation as a function of the phase angle for a freshly calibrated sensor arrangement and for a sensor arrangement that has degraded since its calibration, Figure 5 a plot of a normalized dimensionless intensity of a response radiation as a function of a normalized dimensionless phase angle for a freshly calibrated sensor arrangement with pairs of detection values ​​that were determined on differently degraded sensor arrangements, Figure 6 the plot of Fig. 5with the hypothetical phase values ​​associated with the acquisition value pairs that would have been obtained with a non-degraded sensor arrangement, Figure 7 the plot of Fig. 6 with compensated phase values ​​additionally assigned to the acquisition value pairs, which were obtained using a compensation function equation as a compensation value relationship, and Figure 8 normalized dimensionless plots of a freshly calibrated sensor arrangement in the factory-new state and of a freshly calibrated sensor arrangement with degraded luminophore.

[0059] In Fig. 1 a housing 12 of a sensor arrangement operating according to the principle of luminescence quenching is shown in a partially exploded view.

[0060] The housing 12 comprises a base housing 14 and a window component 16 with a Fig. 1 however, the luminophore-containing layered component arrangement 20 cannot be recognized (see Fig. 2). The window component 16 can be used to close an opening 18 in the base housing 14.

[0061] The housing 12 has connecting pieces 24 and 26 on both sides of the parallelepiped-shaped section 22 formed with the participation of the window component 16 for connecting fluid line sections thereto.

[0062] The housing 12 can be flowed through bidirectionally along the flow axis S.

[0063] In Fig. 2 The sensor arrangement, generally designated 10, is shown schematically in cross section.

[0064] The housing 12 is bidirectionally flowable with test fluid P between its two openings 28 and 30 along the flow axis S. The test fluid P flows past the laminated bodies 32 and 34, making contact with the fluid contact sides 32a and 34a of the laminated bodies. The flow axis S lies in the plane of the drawing of Fig. 2 .

[0065] In the example shown, the sensor arrangement 10 is designed for the temperature-compensated, luminophore-based detection of the oxygen partial pressure of a test fluid P flowing through the housing 12, in this case, for example, air. In this case, oxygen therefore forms an example of a quencher substance Q generally mentioned above. The test fluid can be or comprise a gas or a liquid. The test fluid can be a two-phase substance with both a liquid and a gas. The test fluid can be a suspension of liquid and solid particles, an emulsion, and a similar mixture. For example, the sensor arrangement 10 can be designed to determine the oxygen content in inspiratory and / or expiratory respiratory gas that is supplied to or removed from a patient by means of a ventilation device.

[0066] In the present example, the sensor arrangement 10 is configured for temperature compensation. This allows detection signals obtained from a test fluid P with a temperature that differs from the calibration temperature of a fluid used for calibration with a known concentration of the quencher substance Q to be converted into detection signals that would have been obtained if the test fluid P had been at the calibration temperature during the detection process. However, the present invention also functions with sensor arrangements that are not configured for temperature compensation.

[0067] Both the temperature compensation and the conversion of the directly obtained measured values ​​into an oxygen concentration or oxygen content of the test fluid P are performed by a control device 36 based on calibration information stored in a data memory 38 of the control device 36. In this case, the calibration information also includes, but is not limited to, the calibration value relationship mentioned above. The control or computing device 36 and the data memory 38 together form a data processing unit 39.

[0068] A sensor assembly 40, which can preferably be detachably arranged on the housing 12 and for this purpose, for example, surrounds the parallelepiped-shaped section 22 on three sides in a U-shape, wherein the base of the "U" is opposite the window component 16, comprises in the illustrated embodiment two measuring chambers 42 and 44, which are structurally separated from one another.

[0069] In the measuring chamber 42, which serves to determine the oxygen concentration as a desired result value, an excitation radiation source 46, for example in the form of an LED, is provided, which emits electromagnetic excitation radiation E1 of a first wavelength. In order to keep the wavelength band of the electromagnetic excitation radiation E1 emanating from the excitation radiation source 46 as narrow as possible and to avoid interference radiation, the excitation radiation source 46 can be surrounded by a filter body 48, which transmits the electromagnetic excitation radiation E1 of the specified wavelength with the smallest possible wavelength tolerance.

[0070] The reaction layer 32-1 of the layered body 32 contains a luminophore 33 held in a matrix 35, which can be excited to luminescence by the excitation radiation E1.

[0071] Furthermore, a radiation detector 50 is arranged in the first measuring chamber 42, which detects an electromagnetic response radiation E2 emanating from the reaction layer 32-1 after its excitation by the electromagnetic excitation radiation E1. A radiation filter 52 can also be arranged upstream of the radiation detector 50 to allow only the electromagnetic response radiation E2 with its second wavelength, which differs from the wavelength of the excitation radiation E1, to pass through. The filter arrangements 48 and 52 ensure that no radiation passes directly from the excitation radiation source 46 to the radiation detector 50, thereby "confounding" the signal detected there.

[0072] The signal emitted by the radiation detector 50 due to its detection of the response radiation E2 is transmitted via the Fig. 1transmitted to the control device 36 via the data line 54 shown. It represents, in a manner known per se, the oxygen partial pressure and thus the result value for the test fluid P flowing through the housing 12.

[0073] In the second measuring chamber 44, which is optionally present and serves to temperature compensate the detection signal of the radiation detector 50, an infrared detector 56 is arranged, which detects infrared radiation I emitted by the detection layer 34-1. The signal output by the infrared detector 56 due to its detection of the infrared radiation I is transmitted to the control device 36 via the data line 58. This signal is indicative of a temperature of the detection layer 34-1 and, due to the high thermal conductivity of the layer body 34, also indicative of the temperature of the luminophore-containing reaction layer 32-1, which thermally interacts with the same test fluid flow.

[0074] Based on the calibration information stored in the data memory 38 of the control device 36, which was determined in a separate calibration process prior to the productive use of the sensor arrangement 10, the control device 36 can determine the temperature of the reaction layer 32-1 from the detection signal of the infrared detector 56 for each detection time of a signal from the radiation detector 50 and thus compensate the detection signal of the radiation detector 50 with respect to the temperature of the radiating reaction layer body 32 or the reaction layer 32-1 thereof. The result is a highly accurate determination of the oxygen partial pressure in the test fluid P flowing through the housing 12.

[0075] The highly precise temperature compensation is achieved using extremely simple means, such as a metal foil as the carrier layer 34-2 and the detection layer 34-1 applied thereto. The detection layer 34-1 comprises, or is preferably, a carbon-containing lacquer with carbon as the black color pigment. The carbon-containing lacquer therefore has a very high emissivity of more than 0.9. The use of the metal foil as the carrier layer 34-1, for example formed from an aluminum foil for reasons of the best possible thermal conduction, preferably no more than 12 µm thick, allows the formation of a hole 60 in the window component 16 or generally in the housing 12, which hole 60 penetrates the window component 16 or the housing 12 and is completely covered by the layer body 34. As a result, the temperature information emitted by the detection layer 34-1 as infrared radiation I reaches the infrared detector 56 with the least possible distortion.

[0076] In a sensor arrangement 10 not designed for temperature compensation, the measuring chamber 44 with the infrared detector 56, the detection layer body 34 and the hole 60 are omitted.

[0077] So much for the indirect determination of the temperature of the reaction layer 32-1 and its consideration in determining the result value from the detection signals received from the radiation detector 50. Now back to the evaluation of the detection signals from the radiation detector 50.

[0078] The optical, luminophore-based detection of an oxygen concentration, for example in the form of the oxygen partial pressure, in a test fluid P is known per se. In the present embodiment, it is carried out with the participation of the reaction layer body 32. In this case, the reaction layer body 32 is two-layered. In fact, the reaction layer body 32 can have only one or more than two layers. In the example shown - visible in the cross-sectional view of Fig. 2 - the reaction layer body 32 has a carrier layer 32-2 and the luminophore-containing reaction layer 32-1 applied thereto.

[0079] The ratios of the length and width of the reaction layer body 32 to its thickness are not to scale in the figures. The reaction layer body 32 shown can have an edge length of approximately 7 to 10 mm, and its thickness measured across both layers 32-1 and 32-2 can be approximately 300 µm.

[0080] The carrier layer 32-2 can be formed from a material sufficiently porous for oxygen molecules, such as polyvinylidene fluoride. The carrier layer 32-2 can be cut from a suitable film and have a thickness of between 100 and 150 µm. Under certain circumstances, the thickness of the carrier layer 32-2 can also be less.

[0081] The luminophore-containing reaction layer 32-1 may also contain polyvinylidene fluoride as a matrix material in which luminophores are embedded.

[0082] The luminophore-containing reaction layer 32-1 may be somewhat smaller than the carrier layer 32-2 carrying it in order to facilitate the adhesive attachment of the reaction layer body 32 with the detection side to the window component 16 or generally to the housing 12, without having to cover the detection side 32b of the luminophore-containing reaction layer 32-1 with adhesive.

[0083] The representation of the temperature sensing layer body 34 is also not to scale with regard to its dimensions. In the example shown, it has an edge length in the same range as the reaction layer body 32, but is generally thinner than the reaction layer body 32 due to its different structure.

[0084] The detection sides of the two layered bodies 32 and 34 facing the detectors 50 and 56 (see detection side 32b) are advantageously directed outwards, i.e. away from the test fluid P, while the fluid contact side 32a or 34a of the two layered bodies comes into contact with the fluid over as large an area as possible.

[0085] To ensure that the reaction layer 32-1 is only reached by oxygen dissolved in the test fluid P, the reaction layer body is covered on its detection side 32b by the window component 16. The window component 16 can be made of a transparent polyamide or another plastic permeable to the excitation and response radiation. For example, the window component 16 can be made of amorphous polyamide, such as that offered under the name "Grilamid TR ®<" by EMS-Chemie AG in Domat (CH).

[0086] In Figure 3A graph of a functional relationship between a phase value in degrees plotted along the abscissa and an intensity value plotted along the ordinate is shown. The graph is designated by reference numeral 62.

[0087] During operation of the sensor arrangement 10, the excitation source 46 emits the excitation radiation E1 with a predetermined intensity modulation.

[0088] The response radiation E2 emitted by the luminophore-containing reaction layer 32-1 in response to the modulated excitation radiation E1 therefore also has a modulated intensity. Thus, two detection values ​​of the sensor arrangement 10 are obtainable from the response radiation E2: an intensity value representing the intensity of the response radiation E2 and a phase value indicating the phase offset between the two modulated radiations. The intensity value can be output, for example, as the ratio of the intensity of the response radiation E2 to the intensity of the excitation radiation E1.

[0089] Since, as described above, an interaction with a quencher substance Q, in this case oxygen, for example, in the test fluid P quenches the luminescence of the luminophore in the reaction layer 32-1 depending on the amount of quencher substance Q present in the test fluid P and thus influences both the intensity value and the phase value of the response radiation E2, the concentration of the quencher substance Q in the test fluid P can be deduced from each of the two recorded values: intensity value and phase value, by means of a calibration value relationship.

[0090] For example, for a phase value F a calibration value relationship can be given by the calibrated Stern-Volmer equation given below: tan ϕ tan ϕ 0 T = m 2 1 + K sv T p O 2 + 1 − m 2 1 + m 1 K sv T p O 2 with the recorded phase value F as an exemplary recording value, Φ 0 (T)than the previously known or experimentally determined temperature-dependent phase value in the complete absence of the quencher substance Q, K sv (T) as a previously known or experimentally determined temperature-dependent Stern-Volmer coefficient, with p O 2 as the oxygen partial pressure as an exemplary result value, with m 1 and m 2 than the calibration constants determined during the calibration process.

[0091] Equation 1 as an example calibration value relationship is for recorded phase value F numerically or analytically for the oxygen partial pressure p O 2 as the result value. Thus, the oxygen partial pressure can be determined directly from the recorded phase value.

[0092] To determine the oxygen partial pressure as an exemplary result value, which represents a concentration of the quencher substance Q in the test fluid P, one of the two possible recording values ​​is sufficient.

[0093] The in the reaction layer 32-1 of the sensor arrangement 10 of Figure 2 The luminophore contained in the material always emits a response radiation E2 in response to an excitation radiation E1. However, due to aging of the luminophore, for example, due to bleaching, the material-inherent response characteristic, which determines the luminescence behavior of the luminophore in response to the excitation radiation E1, changes.

[0094] For one and the same excitation radiation E1 and for one and the same concentration of the quencher substance Q, with one and the same sensor arrangement 10, depending on the degradation state of the sensor arrangement 10, a different response radiation E2 is obtained and thus different detection values: intensity value and phase value are obtained.

[0095] The degradation of the luminophore causes the possible detection values: intensity value and phase value, to change from a calibration state based on a reference response characteristic of the luminophore prevailing at the time of calibration to lower values ​​of both the intensity and the phase angle (phase value).

[0096] A laboratory technician working with the sensor arrangement 10, who, for example, receives only one phase value as a detection value due to a detection process for a test fluid, can only be sure that he can deduce the correct result value from the received detection value using the calibration value relationship if the time is sufficiently close to the last calibration process in which the calibration value relationship still in use was determined.

[0097] However, if there is a risk that the luminophore has degraded due to aging since the last calibration, it is impossible to determine without further measures whether a lower detection value obtained is due to an actually higher concentration of the quencher substance Q in the test fluid P or whether age-related degradation of the luminophore is responsible for the low value. Based on a detection value that is too low due to degradation, a result value that is too high will be determined for a given calibration value relationship.

[0098] However, as the inventors of the present application have discovered, the detection values ​​obtained for a predetermined concentration of the quencher substance Q in the test fluid P: intensity value and phase value, have a clear functional relationship. Graph 62 graphically displays this functional relationship. Surprisingly, this functional relationship remains even when the temperature of the test fluid P changes. For graph 62, detection processes were carried out with different partial pressures of the quencher substance Q in the test fluid P at temperatures from 5 to 45 °C in increments of 10 K. In each case, a test fluid P with a known concentration of the quencher substance Q was used, namely with a partial pressure, measured in millibar (hPa), with the amounts 0, 113, 189, 378, 567, 756 and 945. The pairs of recording values ​​obtained by the exemplary measurements, which all represent the same response characteristic of the luminophore orthe luminophore-containing reaction layer 32-1 can be analytically represented, for example, by the least squares method in an equation of suitable structure.

[0099] Figure 4 shows with reference numeral 64 a qualitative relationship between intensity value and phase value for a brand new sensor arrangement 10. The representation corresponds qualitatively to the graph 62 of Figure 3 . In comparison, graph 66 shows Figure 4 a phase value-intensity value relationship of the same sensor arrangement, but with aged luminophore. A comparison of the Figure 4The respective right ends of graphs 64 and 66, which show the detection values: intensity value and phase value, for a test fluid with the complete absence of the quencher substance Q, illustrate how, with the age-related degradation of the luminophore in the sensor arrangement 10, both the intensity value and the phase value of the response radiation E2 provoked by the excitation radiation E1 decrease at the same excitation radiation E1.

[0100] However, due to the clear relationship between intensity and phase values, it is immediately possible to determine whether a detection value was obtained with a degraded luminophore or with a non-degraded luminophore. The degradation refers to the last calibration state, for which the freshly calibrated sensor arrangement 10 functions perfectly. Graphs 64 and 66 in Figure 4are therefore representative of the respective response characteristics of the luminophore in the sensor arrangement 10, once in the calibration state (see 64) and once in a deviating degradation state (see 66).

[0101] For example, if the brand-new sensor array 10 is calibrated, the phase value-intensity value relationship 64 represents the reference response characteristic. The sensor array 10 can be used to measure concentrations of quencher substance Q in the test fluid P as long as the response characteristic of the luminophore does not change from the reference response characteristic 64.

[0102] However, if the response characteristic has developed, for example, towards graph 66 with progressive degradation, the sensor arrangement 10 delivers detection values ​​that are too low for the respective concentration of quencher substance Q in the test fluid P and thus ultimately incorrect result values. However, if the sensor arrangement 10 is recalibrated in this degradation state, the phase value-intensity value relationship represented by graph 66 becomes the reference response characteristic, and the sensor arrangement 10 again delivers correct result values. However, the sensor arrangement 10 will continue to degrade, so that incorrect detection values ​​will be obtained again some time after the last calibration.

[0103] By considering not just one detection value, but both detection values: intensity value and phase value, it can be immediately determined whether the operating state of the sensor array sufficiently corresponds to the calibration state, or whether it has deviated beyond a tolerance threshold to such an extent that recalibration is necessary. Calibration processes are unproductive and therefore expensive. The goal is therefore to reduce the frequency of calibration of the sensor array 10 as much as possible.

[0104] A dashed line in Figure 4Trace 68 qualitatively indicates how, for a test fluid P with a predetermined constant concentration of the quencher substance Q, the phase value and the intensity value change with the progressive degradation of the luminophore in the sensor arrangement 10. Through repeated calibration, the respective detection value obtained on trace 68 can be linked to the correct result value, namely the previously known constant concentration of the quencher substance Q, in any degradation state.

[0105] Figure 8 shows an astonishing correlation. If the two graphs 64 and 66 of different degradation states are standardized in such a way that they can only show detection values ​​between the extreme values ​​0 and 1, one obtains the standardized dimensionless curves 70 and 72 for the graphs 64 and 66 of Figure 4 . The two curves are identical in the normalized dimensionless notation.

[0106] The normalization can be used, for example, for the recorded phase value F and the recorded intensity value I according to equations 2 and 3 shown below: ϕ N = ϕ − ϕ min ϕ max − ϕ min I N = I − I min I max − I min where F N is the normalized dimensionless phase value and where IN is the standardized dimensionless intensity value. With the index max is the largest possible detection value in terms of amount, for example in the complete absence of the quencher substance Q, and with the index minutes the smallest possible detection value in terms of amount, for example when using pure quencher substance Q as test fluid P.

[0107] The extreme values ​​required for normalization Φ max , Φ min , I max and I min can be determined either experimentally or analytically by approximate calculations shown below: For example, the normalized phase value-intensity value relationship of Figure 8for a new sensor arrangement 10 of this sensor arrangement type can be described by the following polynomial: I N <none / > <mprescripts / > a <none / > ϕ N = α ϕ N + β ϕ N 2 + 1 − α − β ϕ N 3 with the boundary conditions a IN (0) = 0 and a IN (1) = 1.

[0108] Using standard fitting methods, the coefficients α and β the values α = 1.17954 and β = 0.26311. Equation 4 thus describes a response characteristic of the sensor arrangement 10 or of the sensor arrangement type of the sensor arrangement 10. It is preferably stored in the data memory 38.

[0109] The extreme values Φ max and F min can be calculated immediately during or after calibration from equation 1 with p o 2 = 0 (for Φ max ) and with p o 2 = p o 2, max (for F min ) can be calculated directly.

[0110] For the dimensioned value pairs used for calibration ( F i , I) can then be used with known Φ max , Φ min , from equation 2 the normalized dimensionless phase values Φ N,i Since equations 3 and 4 must be I N , i <none / > <mprescripts / > a <none / > = I N <none / > <mprescripts / > a <none / > Φ N , i − I min I max − I min From equation 5 the extreme values I max and I min be determined by numerically solving the following system of equations: I max = I 2 1 + β ϕ N , 1 − 1 ϕ N , 1 2 − ϕ N , 1 3 + α ϕ N , 1 ϕ N , 1 2 − 1 + I 1 ϕ N , 2 3 + α ϕ N , 2 1 − ϕ N , 2 2 − 1 − β ϕ N , 2 − 1 ϕ N , 2 2 − ϕ N , 1 3 + ϕ N , 2 3 + α − ϕ N , 1 + ϕ N , 1 3 + ϕ N , 2 − ϕ N , 2 3 + β − ϕ N , 1 2 + ϕ N , 1 3 + ϕ N , 2 2 − ϕ N , 2 3 I min = I 2 ϕ N , 1 β ϕ N , 1 − 1 − ϕ N , 1 ϕ N , 1 + α ϕ N , 1 2 − 1 + I 1 ϕ N , 2 α 1 − ϕ N , 2 2 + ϕ N , 2 β + 1 − β ϕ N , 2 − ϕ N , 1 3 + ϕ N , 2 3 + α − ϕ N , 1 + ϕ N , 1 3 + ϕ N , 2 − ϕ N , 2 3 + β − ϕ N , 1 2 + ϕ N , 1 3 + ϕ N , 2 2 − ϕ N , 2 3 ,

[0111] However, the determination of the extreme values ​​only needs to be carried out during calibration. The use of only two pairs of values ​​with j = 1, 2 is sufficient.

[0112] The extreme values ​​determined in this way Φ max , Φ min , I max and I min can be calculated for each detection process of the sensor arrangement 10 or a sensor arrangement of the same sensor arrangement type from equations 2 and 3 directly and immediately from the obtained dimensioned detection values Φ j , I j the corresponding dimensionless standardized recording values Φ N,j , IN,jcan be determined without much effort.

[0113] By comparing the standardized detection values ​​thus determined Φ N,j , IN,j with the values ​​obtained from equation 4 a I N , j ( ϕ N , j ) it can be determined immediately whether the luminophore of the sensor arrangement 10 is degraded or not. If such a determination shows that the luminophore is degraded, the control device 36 outputs an optical and / or acoustic warning signal via the data line 59 to an output device 61, where it can be perceived by the operating personnel of the sensor arrangement 10.

[0114] The response characteristic of equation 4 is in Fig. 5as a reference response characteristic shown as graph 74. As long as the response characteristic of the sensor arrangement 10 (or a sensor arrangement of the same type) matches the reference response characteristic at the time of calibration, the sensor arrangement 10 provides value pairs Φ N,j , IN,j , which lie on the graph 74. A calibration value relationship based on the graph 74, which links detection values ​​of the sensor arrangement 10 with associated result values ​​for the concentration or the partial pressure of the quencher substance Q in the test fluid P, provides correct result values.

[0115] With increasing degradation, the acquisition value pairs obtained for a test fluid differ Φ N,j , IN,j However, it deviates from graph 74. The deviation occurs with increasing degradation along the Fig. 5shown tracks, of which, for the sake of clarity, only the four rightmost tracks are designated by the reference numerals 76 to 82. If the obtained detection value pairs lie outside the tolerance band T, the control device 36 concludes that the degradation of the luminophore is no longer tolerable and issues the warning message.

[0116] Each of these traces shows the course of pairs of acquisition values ​​obtained with increasing degradation for a test fluid P with a constant concentration of quencher substance Q. The Fig. 5 The traces shown are iso-concentration lines that indicate the detection value pairs output by the sensor arrangement 10 for identical test fluids P with a constant concentration of the quencher substance Q in different degradation states. Thus, trace 80 in Fig. 5For example, the curve of those acquisition value pairs obtained from the reference response characteristic 74 for the test fluid that delivers a standardized dimensionless phase value of 0.7 based on the reference response characteristic. With progressive degradation, the standardized dimensionless phase values ​​also become increasingly smaller in the standardized dimensionless value space than when using a sensor arrangement that has not yet degraded since the last calibration.

[0117] Iso-concentration lines could also be used in the dimensioned representation of the Fig. 4 as shown by track 68 there, which is also an iso-concentration line. The term "iso-concentration line" is synonymous with the term "iso-partial pressure line."

[0118] When creating the plot of Fig. 5with one or more additional, freshly calibrated sensor arrangements for each detection point the actual concentration (partial pressure) of the quencher substance Q in the test fluid P, then using the above equation 1 with known oxygen partial pressure p o 2 that hypothetical phase value HYP which would have been determined instead of the phase value actually determined with the sensor arrangement 10 in different degradation states, the sensor arrangement 10 would be in the calibration state during the respective detection process.

[0119] The representation of the plot of Fig. 5 with a hypothetical detection value in the form of the hypothetical phase value assigned to each actual detection value pair HYP is in Fig. 6 Actually recorded acquisition value pairs (also called "actual acquisition value pairs") are shown in the Fig. 5 to 7represented as a solid diamond. The hypothetical phase value associated with an actual acquisition value pair HYP is in the Fig. 5 to 7 shown as an unfilled square.

[0120] For five actual acquisition value pairs, Fig. 6 with thin arrows the deviation of their actually recorded phase value from the hypothetical phase value determined from the known concentration using equation 1 HYP A hypothetical trace 84 shows the course of the hypothetical phase values HYP for the actual detection values ​​assigned to track 78.

[0121] A mapping rule which maps actually acquired detection value pairs to the associated hypothetical detection value at least with regard to one detection value, in the example shown: the phase value, thus provides a degradation compensation which transfers the detection value required for determining the result value from an actual detection value to a hypothetical detection value of a non-degraded sensor arrangement.

[0122] A possible mapping rule of this kind is the following equation 8: ψ N ϕ N I N = a ϕ N + b ϕ N 2 + c I N + d I N ϕ N + e I N 2

[0123] This equation 8 forms normalized dimensionless acquisition value pairs ( Φ N , IN ) as standardized dimensionless degradation-compensated acquisition values, here degradation-compensated phase values ψ N,. Equation 8 therefore uses both the detected intensity and the detected phase value of a detection process to compensate the phase value for any degradation of the luminophore that may have occurred and thus output a model phase value that would have been obtained by the sensor arrangement 10 if it had been in the calibration state during the detection process. Experimentally, for the sensor arrangement type of the sensor arrangement 10, the parameter values a = 1.20, b = 0.2, c = -0.14, d = -0.5 and e = 0.25 can be determined.

[0124] For the application of the mapping rule of equation 8, it is particularly advantageously irrelevant whether the luminophore of the sensor arrangement 10 is actually degraded or not. It maps value pairs that satisfy equation 4 onto themselves with sufficient accuracy.

[0125] Equation 8 is therefore an example of a compensation-value relationship, as mentioned in the introduction to the description. This is stored in data memory 38.

[0126] Figure 7 For actually recorded acquisition value pairs, additionally shows the associated degradation-compensated standardized dimensionless phase values ​​with a window symbol.

[0127] By replacing the normalized dimensionless phase value F N in equation 2 by the degradation compensated phase value ψ N and by transforming equation 2 accordingly, the normalized dimensionless degradation-compensated phase value ψ N into a dimensionally degradation-compensated phase value ψ be converted.

[0128] If the degradation-compensated phase value ψ instead of the phase value FWhen inserted into the calibration value relationship of equation 1, the desired quencher substance partial pressure can be correctly determined even with a degraded sensor arrangement 10 and output to the output device 61 via the data line 59.

[0129] The above value relationships and equations are stored in the data memory 38 of the control device 36. The control device 36 is designed to perform the above calculation operations and thus calculate a correct result value from a detection value of the sensor arrangement 10, even if, due to age-related degradation of the luminophore, the response characteristic underlying a detection process differs, even significantly, from the reference response characteristic underlying the generation of the calibration value relationship.

[0130] To better understand this complex topic, the handling of the determination of result values ​​from degradation-compensated detection values ​​is summarized again: First, equations 4 and 8, which apply to sensor arrangements of the same design, i.e. to a sensor arrangement type as a whole, are parameterized for the sensor arrangement type by experiments with sensor arrangements of the respective type in different degradation states and with different test fluids, especially with different concentrations of quencher substance.

[0131] The specific sensor arrangement 10 is calibrated, ie the parameter values ​​of equation 1 applicable to the sensor arrangement 10 are determined on the basis of at least two calibration measurements with test fluids with known quencher substance contents that are as different as possible.

[0132] With the calibration, the extreme values ​​are determined based on the acquisition values ​​of the calibration measurements and on the basis of equation 4 already parameterized for the sensor arrangement type with equation 5, transformed to equations 6 and 7. I max and I min certainly.

[0133] From equation 1 parameterized by calibration, the extreme values Φ max and F min certainly.

[0134] The sensor array 10 is now put into productive acquisition mode. The acquired values ​​are converted into standardized dimensionless acquisition values ​​using equations 2 and 3.

[0135] The standardized dimensionless acquisition value pairs ( F N , IN ) are used as arguments in Equation 8. With Equation 8, for each pair of acquisition values ​​( Φ N , IN) a standardized dimensionless degradation-compensated detection value is determined, which is converted into a dimensioned degradation-compensated detection value using the correspondingly transformed equation 2.

[0136] Using this dimensionally degradation-compensated detection value, the result value is determined by the parameterized equation 1 and output by the control device 36.

[0137] Additionally or alternatively, the control device 36 can determine and output the degradation state of the sensor arrangement based on a comparison of the degradation-compensated detection value with the actually detected detection value, whether dimensionless, dimensionlessly standardized or dimensionally dependent, and / or based on a comparison of result values ​​determined on the basis of these two detection values.

[0138] Based on this comparison, the control device can be based on the known degradation curves, as shown in the Figures 4 to 7 shown, determine and output an estimate of the remaining service life of the sensor arrangement 10.

[0139] Based on this comparison, the control device can additionally or alternatively output either a result value determined based on the actually recorded values, for example, when a difference between recorded values ​​and degradation-compensated recorded values ​​is less than or equal to a predetermined acceptance threshold, or output a result value determined based on the degradation-compensated recorded values, for example, when the difference between recorded values ​​and degradation-compensated recorded values ​​is greater than a predetermined acceptance threshold. In this case, a result value determined based on the degradation-compensated recorded values ​​preferably outputs an indication that this value was not determined directly from the actually recorded values.

[0140] The control device 36, the data memory 38 and the output device 61 form an evaluation device 63.

Claims

1. A method for degradation-compensated evaluation of detection signals of a sensor arrangement (10) operating on the principle of luminescence quenching, which sensor arrangement (10) comprises a luminophore (33) that degrades over time, an excitation radiation source (46), and at least one optical sensor (50), the luminophore (33) radiating, in accordance with a response characteristic (62, 64, 66, 70, 72, 74) typical of the sensor arrangement, in reaction to irradiation with a predefined modulated excitation radiation (E1) and as a function of the extent of an interaction of the luminophore (33) with a quencher substance (Q) that quenches the luminescence of the luminophore (33), a response radiation (E2) detected by the at least one optical sensor (50); the sensor arrangement (10) outputting, as detection signals, a detected intensity value representing an intensity of the response radiation (E2) and a detected phase value representing a phase difference of the response radiation (E2) with respect to the modulation of the excitation radiation (E1); characterized in that for an accomplished detection of a response radiation (E2), a quantitative deviation of one of the detected values, from among a detected intensity value and detected phase value, being quantitatively decreased in accordance both with the detected intensity value and with the detected phase value, the deviation being based on a degradation-based change in the response characteristic (62, 64, 66, 70, 72, 74) at the time of the accomplished detection, with respect to a reference response characteristic (64, 70, 72, 74) which is a basis of a calibration of the sensor arrangement (10), a degradation-compensated detected value thus being identified; a result value of the accomplished detection, referred to the quencher substance (Q), being determined on the basis of the degradation-compensated detected value in accordance with a predetermined calibration value correlation identified in consideration of the reference response characteristic (64, 70, 72, 74).

2. The method according to Claim 1, characterized in that it encompasses the step of identifying the degradation-compensated detected value on the basis of a predetermined compensation value correlation with input variables on the basis of the detected intensity value and the detected phase value.

3. The method according to Claim 1 or 2, characterized in that it encompasses the step of transforming both the detected intensity value and the detected phase value, using at least one system parameter characterizing the sensor arrangement (10) and / or at least one process parameter deriving from the detection process, into a dimensionless detected intensity value and into a dimensionless detected phase value, the predetermined compensation value correlation then being a predetermined dimensionless compensation value correlation in accordance with which, with input variables on the basis of the dimensionless detected intensity value and the dimensionless detected phase value, the degradation-compensated detected value is identified.

4. The method according to Claim 3, characterized in that the degradation-compensated detected value is a dimensionless degradation-compensated detected value; and the predetermined calibration value correlation is a dimensionless predetermined calibration value correlation, the result value being identified in accordance with the dimensionless calibration value correlation with an input variable on the basis of the dimensionless degradation-compensated value.

5. The method according to one of the preceding claims, characterized in that the degradation-compensated detected value is a degradation-compensated detected phase value.

6. An evaluation apparatus (63) that is embodied to execute the method according to one of the preceding claims and is thus embodied for degradation-compensated evaluation of detection signals of a sensor arrangement (10) that operates according to the principle of luminescence quenching and has a luminophore (33) that degrades over time, has an excitation radiation source (46), and has at least one optical sensor (50); the luminophore (33) radiating, in accordance with a response characteristic (62, 64, 66, 70, 72, 74) typical of the sensor arrangement, in reaction to irradiation with a predefined modulated excitation radiation (E1) and as a function of the extent of a contact of the luminophore (33) with a quencher substance (Q) that quenches the luminescence of the luminophore (33), a response radiation (E2) detected by the at least one optical sensor (50); the evaluation apparatus (63) comprising a data input channel (54) that is embodied to transfer from the sensor arrangement (10) to a data processing unit (39) of the evaluation apparatus (63), as detection signals, the detected intensity value representing the intensity of the response radiation (E2) and the detected phase value representing a phase difference of the response radiation (E2) with respect to the modulation of the excitation radiation (E1); the data processing unit (39) comprising a data memory (38) for storing data and a computation unit (36) for processing data; at least the predetermined calibration value correlation identified in consideration of the reference response characteristic (64, 70, 72, 74) being stored in the data memory (38); the evaluation apparatus (63) being embodied to ascertain the degradation-compensated detected value from the detected intensity value and detected phase value in accordance with both the detected intensity value and the detected phase value, and to determine and output the result value, referred to the quencher substance (Q), of the accomplished detection in accordance with the calibration value correlation on the basis of the degradation-compensated detected value.

7. The evaluation apparatus (63) according to Claim 6, characterized in that the predetermined compensation value correlation is also stored in the data memory (38), the computation unit (36) being embodied to identify the degradation-compensated detected value in accordance with the predetermined compensation value correlation with input values on the basis of the detected intensity value and of the detected phase value.

8. The evaluation apparatus (63) according to Claim 6 or 7, characterized in that the evaluation apparatus (63) is embodied to transform both the detected intensity value and the detected phase value, utilizing at least one system parameter characterizing the sensor arrangement (10) and / or at least one process parameter deriving from the detection process, into a dimensionless detected intensity value and into a dimensionless detected phase value, the predetermined compensation value correlation being a predetermined dimensionless compensation value correlation in accordance with which, with input variables on the basis of the dimensionless detected intensity value and the dimensionless detected phase value, the degradation-compensated detected value is identified.

9. The evaluation apparatus (63) according to Claim 8, characterized in that the degradation-compensated detected value is a dimensionless degradation-compensated detected value; and the predetermined calibration value correlation is a dimensionless predetermined calibration value correlation, the evaluation apparatus (63) being embodied to ascertain the result value in accordance with the dimensionless calibration value correlation with an input variable on the basis of the dimensionless degradation-compensated value.

10. The evaluation apparatus (63) according to one of Claims 6 to 9, characterized in that the degradation-compensated detected value is a degradation-compensated detected phase value.

11. A measurement arrangement encompassing an evaluation apparatus (63) according to Claims 6 to 10 and a sensor arrangement (10) having a luminophore (33) that degrades over time, having an excitation radiation source (46), and having at least one optical sensor (50); the luminophore (33) radiating, in accordance with a response characteristic (62, 64, 66, 70, 72, 74) typical of the sensor arrangement, in reaction to irradiation with a predefined modulated excitation radiation (E1) and as a function of the extent of a contact of the luminophore (33) with a quencher substance (Q) that quenches the luminescence of the luminophore (33), a response radiation (E2) detected by the at least one optical sensor (50).