Spectrometric measurement method and measurement device for

Abstract

The invention relates to a spectrometric measurement method and a measurement device for performing the spectrometric measurement method. The invention relates to a spectrometric measuring method and a measuring device for measuring a measured variable of a liquid medium, in which interferents may occur, including air bubbles, gas bubbles and / or particles, the size of which is larger than a wavelength in the measurement wavelength range. During this process, measurement spectra of the medium are determined and those measurement spectra that have undergone optical saturation are discarded. A media spectrum is determined for each of the remaining measurement spectra. In this case, a test is performed using a predetermined reference of spectral characteristics expected in the absence of an interferent in a spectral range in which the absorption coefficient of the medium varies less than a predetermined spectral variance and / or below a limit value to check whether the measurement spectrum contains an offset caused by the interferent. If there is an offset, the offset is subtracted from the corresponding measurement spectrum. Finally, a measured value for each measured variable is determined using the medium spectrum.

Description

Field of the Invention

[0001] The present invention relates to a spectroscopic measurement method for determining at least one measurement variable of a liquid medium, and a measurement device designed to carry out the measurement method. Background Art

[0002] Measurement devices for carrying out spectroscopic measurement methods are used in a variety of different types of applications, such as in wastewater treatment plants, in laundries, and in drinking water conveyance plants, to measure different measurement variables.

[0003] These measurement devices generally include a spectroscopic sensor having a spectroscopic unit that, during a measurement operation, receives measurement radiation generated by interaction with the medium, such as absorption, reflection, and / or scattering, and uses the measurement radiation to determine a measurement spectrum, where each spectral value in the measurement spectrum reproduces the spectral value of the measurement radiation in a predetermined measurement wavelength range. These measurement spectra are provided to an evaluation device that uses the measurement spectra to determine a measured value of at least one measurement variable, such as the concentration of an analyte in the medium—for example, the nitrite content and / or nitrate content of the medium, the chemical or biological oxygen demand of the medium, and / or the turbidity of the medium.

[0004] Many applications have the following problem: Interferents that may occur in the medium at the application location—such as air or gas bubbles and / or larger particles—temporarily impair the quality of the measurement spectrum. For example, air or gas bubbles may occur if compressed air cleaning is carried out at or near the spectroscopic sensor. In addition, they may also be caused by turbulence of the medium flowing past the spectroscopic sensor. The presence of air or gas bubbles generally has a direct impact on the measurement spectrum. This in turn leads to corresponding errors in the measured values determined based on the measurement spectrum. Therefore, due to the measurement spectrum being affected by interferents, certain measured values may sometimes have significant measurement errors. Similarly, impurities in the medium, such as particles visible to the naked eye, such as small stones and / or sand blocks, may also impair the quality of the measurement spectrum and lead to corresponding incorrect measured values. Incorrect measured values are particularly problematic if the measured values are used to monitor, control, and / or regulate the properties of the medium, the plant, and / or the process, such as a manufacturing process.

[0005] Particularly problematic in this regard is that interferents such as gases or gas bubbles and particles visible to the naked eye occur naturally at unpredictable times and only for a short time period in each case. Unlike interfering analytes that are permanently contained in the medium and whose influence on the measurement spectrum that interferes with the measurement can be at least partially compensated for by subtracting the reference spectrum of the interfering analyte, the disturbing influence that occurs occasionally for a short time period at unknown times cannot be easily compensated for correspondingly.

[0006] The adverse effects of interfering substances present in the medium on the quality of the measured values can be reduced, for example, by the method described in the German patent application with the document reference number DE 102022130510.4 filed on December 17, 2022. This method enables measurement spectra whose quality is impaired by interfering substances in the medium to be identified as outliers. This has the advantage that the measurement spectra identified as outliers can be discarded and thus incorrect measured values caused by the outliers can be avoided. However, the disadvantage is that reliable measured values cannot be determined during the period in which the measurement spectra identified as outliers are recorded.

[0007] Another method of solving this problem is to reduce the number of possible interfering substances by technical measures - such as bubble traps or particle filters - and / or by appropriately selecting the installation location of the spectrometric sensor. However, this does not completely eliminate the interfering substances in the medium and their adverse effects on the availability of reliable measured values.

[0008] JP 2012 093352A describes a device with an optical or electrical bubble detector that can be used to detect any bubbles that may occur in the liquid medium flowing through the supply line of an analyzer. When bubbles occur, the medium is supplied via a switch to a bubble removal channel, where the bubbles are removed by means of a bubble removal device. However, the use of the corresponding device is complex and associated with additional costs. Summary of the Invention

[0009] An object of the present invention is to provide a spectrometric measurement method that enables the measurement period during which reliable measured values can be determined to be extended despite the occasional occurrence of interfering substances in the medium for a limited period of time.

[0010] For this purpose, the present invention includes a spectrometric measurement method for measuring at least one measurement variable of a liquid medium, wherein interfering substances can occur in the liquid medium, and the interfering substances include air bubbles, gas bubbles, and / or particles whose size is larger than the wavelength in a predetermined measurement wavelength range, and wherein:

[0011] The spectrometric sensor is used to continuously determine the measurement spectrum of the medium in the measurement wavelength range,

[0012] Those measurement spectra in which optical saturation of the spectrometric sensor has occurred during their recording are identified and discarded,

[0013] For at least one or for each of the remaining measurement spectra, the medium spectrum is determined by the following operations:

[0014] The verification method is carried out, in which, in the absence of interfering substances within a predetermined spectral range, a predetermined reference of the spectral characteristics expected and a specific measured spectrum are used to verify whether the specific measured spectrum contains an offset caused by interfering substances that occurred in the medium during the recording of the specific measured spectrum. In the predetermined spectral range, the change in the absorption coefficient of the medium is less than a predetermined spectral variance depending on the wavelength and / or below a predetermined limit value. And, if there is an offset, the magnitude of the offset is determined, and

[0015] If the measured spectrum does not contain an offset, the medium spectrum is determined such that the medium spectrum is equal to the measured spectrum. And if the measured spectrum contains an offset, the medium spectrum is determined such that the medium spectrum is equal to the difference spectrum determined by subtracting the offset from the measured spectrum, and

[0016] The medium spectrum is used to determine and provide the measured value of the measured variable or each measured variable.

[0017] The advantage provided by this measurement method is that all measured spectra that did not undergo optical saturation during their recording are provided for determining the measured values of the measured variables. The advantage provided by this verification method is that any interfering substances that may have occurred in the medium during the recording of the measured spectrum are thereby detected, and their influence on the measured spectrum is compensated accordingly by subtracting the offset. The advantage provided by the latter is that high measurement accuracy is achieved not only in the absence of interfering substances but also in the presence of interfering substances.

[0018] This results in an extended measurement period during which reliable measured values can be determined even though interfering substances occasionally occur in the medium for a limited period. These measurement periods are only interrupted during those periods when the influence of the interfering substances occurring in the medium is significant enough to cause optical saturation.

[0019] Another development includes

[0020] The measurement wavelength range includes wavelengths in the ultraviolet range, visible range, and / or near-infrared range, and / or wavelengths in the wavelength range from 190 nm to 2500 nm or a part of this wavelength range, and

[0021] The spectral range includes at least one wavelength in the visible range, at least one wavelength in the range from 380 nm to 800 nm, at least one wavelength in the near-infrared range, and / or at least one wavelength in the range from 800 nm to 2500 nm.

[0022] The first variant provides

[0023] The predetermined spectral range includes reference wavelengths located within a sub-range of the measurement wavelength range,

[0024] The reference includes a reference value of the spectral value expected at the reference wavelength in the absence of an interferent, and

[0025] The verification method includes a first verification method, in which:

[0026] Determine the difference between the spectral value of a specific measured spectrum at the reference wavelength and the reference value, and

[0027] If the difference is greater than a predetermined tolerance, establish the presence of an offset having a magnitude corresponding to the value of the difference.

[0028] The development of the first variant includes the fact that

[0029] a) The measurement wavelength range includes wavelengths in the ultraviolet and visible ranges or includes wavelengths in the visible range, and the reference wavelength located within the measurement wavelength range is within the long-wavelength edge wavelength range of the measurement wavelength range and / or is greater than or equal to 380 nm or greater than or equal to 500 nm, or

[0030] b) The measurement wavelength range includes wavelengths in the visible and / or near-infrared ranges, and the reference wavelength located within the measurement wavelength range is within the long-wavelength edge wavelength range, short-wavelength edge wavelength range or middle wavelength range of the measurement wavelength range, and / or is greater than or equal to 380 nm, greater than or equal to 500 nm, greater than or equal to 800 nm, or greater than 830 nm.

[0031] According to a further development of the first variant, the reference value expected at the reference wavelength is pre-determined based on the spectral values of the reference spectrum recorded at the reference wavelength by means of a spectroscopic sensor in the absence of an interferent.

[0032] The second variant includes the fact that

[0033] The predetermined spectral range includes a reference wavelength outside the measurement wavelength range,

[0034] The reference includes a reference value of the spectral value expected at the reference wavelength outside the measurement wavelength range in the absence of an interferent, and

[0035] The verification method includes a second verification method, in which:

[0036] Determine the spectral value missing from the measurement spectrum at a reference wavelength outside the measurement wavelength range by extrapolation using two or more spectral values at different wavelengths included in the measurement spectrum, wherein the different wavelengths are in the edge range of the measurement wavelength range, and the edge range faces the reference wavelength outside the measurement wavelength range,

[0037] Determine the difference between the spectrally determined value extrapolated for the reference wavelength and the reference value, and

[0038] if the difference is greater than a predetermined tolerance, establish the presence of an offset having a magnitude corresponding to the value of the difference.

[0039] The development of the second variant includes the fact that

[0040] a) the measurement wavelength range includes wavelengths in the ultraviolet and / or visible range, and the reference wavelength outside this measurement wavelength range is much larger than the wavelengths in the measurement wavelength range,

[0041] b) the measurement wavelength range includes wavelengths in the ultraviolet range, and the reference wavelength outside this measurement wavelength range is in the visible range and / or greater than or equal to 380 nm or greater than or equal to 500 nm,

[0042] c) the measurement wavelength range includes wavelengths in the visible range, and the reference wavelength outside this measurement wavelength range is in the near-infrared range and / or greater than or equal to 800 nm or even greater than or equal to 830 nm, or

[0043] d) the measurement wavelength range includes wavelengths in the near-infrared range, and the reference wavelength outside this measurement wavelength range is much smaller than the wavelengths in the measurement wavelength range, is in the visible range and / or greater than or equal to 380 nm or greater than or equal to 500 nm.

[0044] According to a further development of the first variant, the reference value expected in the reference wavelength in the absence of interfering substances is pre-determined using the spectrally determined value ascertained by extrapolation for the reference spectrum recorded by means of a spectral sensor in the absence of interfering substances in the reference wavelength.

[0045] The third variant provides

[0046] a predetermined spectral range includes a sub-range of the measurement wavelength range,

[0047] a reference includes a reference series of spectral values expected in the sub-range in the absence of interfering substances, and

[0048] the verification method includes a third verification method, in which:

[0049] a wavelength-dependent auxiliary function defined in the sub-range is set, the wavelength-dependent auxiliary function corresponding to the sum of the product of an offset variable and a scaling factor and the reference series,

[0050] the values of the offset variable and the scaling factor are determined for which the difference between the auxiliary function and a specific measured spectrum in the sub-range is minimal, and

[0051] If the value of the offset variable that minimizes the difference is greater than a predetermined tolerance, the existence of an offset having a magnitude corresponding to the value of the offset variable that minimizes the difference is established.

[0052] The development of the third variant includes the fact that

[0053] Measurement wavelength range:

[0054] a) includes wavelengths in the ultraviolet and visible ranges or wavelengths in the visible range, and the sub-range is the long-wavelength edge wavelength range of the measurement wavelength range and / or includes wavelengths greater than or equal to 380 nm or greater than or equal to 500 nm, or

[0055] b) includes wavelengths in the visible and / or infrared ranges, and the sub-range ( ) is the long-wavelength edge wavelength range, short-wavelength edge wavelength range or intermediate wavelength sub-range of the measurement wavelength range ( ), and / or includes wavelengths greater than or equal to 380 nm, greater than or equal to 500 nm, greater than or equal to 800 nm, or greater than or equal to 830 nm, and / or

[0056] Based on the spectral order of the reference spectrum recorded in the sub-range by the spectroscopic sensor in the absence of interferents, the reference order expected in the sub-range of the measurement wavelength range in the absence of interferents is pre-determined.

[0057] According to one embodiment, based on the spectral values of the medium spectrum, the concentration of the analyte contained in the medium, the nitrite content of the medium, the nitrate content of the medium, the chemical oxygen demand of the medium, the biological oxygen demand of the medium, the color of the medium, the organic carbon content of the medium, the dissolved organic carbon content of the medium, and / or the turbidity of the medium are measured.

[0058] Furthermore, the present invention includes a measuring device for performing the measuring method according to the present invention, the measuring device

[0059] is designed as a spectroscopic sensor or includes a spectroscopic sensor, wherein the spectroscopic sensor is designed to continuously determine and provide the measurement spectrum of the medium in a predetermined measurement wavelength range, and

[0060] includes an evaluation device, wherein the evaluation device:

[0061] includes a signal processing device, the signal processing device being designed to determine the medium spectrum based on the measurement spectrum determined by the spectroscopic sensor, and

[0062] includes a measurement value determination device, the measurement value determination device being designed to determine and provide the measurement value of the measurement variable or each measurement variable based on the medium spectrum.

[0063] According to a further development, the measuring device comprises an output device connected to the evaluation device, wherein the output device:

[0064] comprising an interface via which measured values ​​can be read out, output and / or transmitted in the form of data and / or signals wirelessly and / or via a line,

[0065] including a display device for displaying the measured values, and / or

[0066] A display element is included that indicates when the presence of an offset has been determined using a validation method and / or indicates whether a measurement spectrum upon which a particular measurement value was determined contains an offset.

[0067] Furthermore, the present invention also comprises a computer program comprising computer-readable program code elements which, when executed on a computer, cause the computer to use a measurement spectrum determined by a spectrometric sensor to perform method steps of a measurement method performed in a measurement method according to the present invention based on the measurement spectrum, or at least to determine a medium spectrum and to provide a measured value of the medium spectrum and / or the measurement variable or each measurement variable.

[0068] Furthermore, the present invention also includes a computer program product, comprising the above-mentioned computer program and at least one computer-readable medium, on which at least the computer program is stored. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] The invention and its advantages will now be described in detail using the figures in the accompanying drawings, which show several examples of embodiments. In the figures like elements are indicated by like reference numerals.

[0070] Figure 1 Shown are: a flow chart of a measurement method;

[0071] Figure 2 Shown: for execution Figure 1 Measuring equipment for the measurement method shown in;

[0072] Figure 3 Shown are: sub-spectra contained in the measured spectrum;

[0073] Figure 4 Shown are: a method for offset determination using reference values ​​within the measurement wavelength range; and

[0074] Figure 5 Shown are: a method for offset determination using a reference value that lies outside the measurement wavelength range; and

[0075] Figure 6shows: a method for determining an offset using a reference series. Detailed Description

[0076] The present invention includes a spectrometric measurement method for determining at least one measurement variable of a medium, and a measurement device for performing the method. In Figure 1 a flowchart of the measurement method is shown. In Figure 2 an exemplary embodiment of a measurement device 100 for performing Figure 1 the measurement method shown in

[0077] As Figure 2 shown, the measurement device 100 includes: a spectrometric sensor 1, which is designed to repeatedly determine and provide a measurement spectrum of the medium 3 in a predetermined measurement wavelength range ; and an evaluation device 5, which is designed to determine and provide a measured value mv of the measurement variable based on the measurement spectrum using the method shown in Figure 1 for the medium 3.

[0078] In Figure 2 the exemplary embodiment shown, the spectrometric sensor 1 is designed as a sensor operating in transmission. The shown spectrometric sensor 1 includes: a radiation source 7, which radiates radiation through the medium 3 during the measurement operation; and a spectrometric unit 9, which receives the measurement radiation S emitted from the medium 3. The radiation interacts with the medium 3 along an optical path 11 passing through the medium 3 in this case, during which a component of the radiation emitted from the radiation source 7 is absorbed, and this component depends on the wavelength-dependent absorption characteristics of the medium 3. In a turbid medium 3, further interactions usually also occur, where a component of the radiation emitted from the radiation source 7 into the medium 3 (which component depends on the turbidity of the medium 3) is scattered in directions other than the optical path 11. This component generally has a significantly lower wavelength dependence than the component absorbed by the medium 3 along the optical path 11. Each component causes a reduction in the radiation intensity received by the spectrometric unit 9.

[0079] The spectrometric unit 9 shown here by way of example includes a detector 13 that receives the measurement radiation S and a measurement electronics unit 15 connected to the detector 13. The measurement electronics unit 15 determines the measurement spectrum using the radiation intensities of the measurement radiation S measured by the detector 13 at different wavelengths . The measurement spectrum can be determined, for example, as an intensity spectrum provided by the measurement electronics unit 15, for example in the form of an original digital or analog spectrometric signal, which includes the intensities measured for specific wavelengths and the associated wavelengths Pairs of spectral values. Alternatively, the measuring electronic unit 15 is designed to convert the measured spectrum into an absorption spectrum. In this case, the spectral values of the measured spectrum - these spectral values each occur for a specific wavelength and are formed as absorption values - for example, each according to is determined as the intensity of the radiation entering the medium 3 at this wavelength and the intensity of the measured radiation S impinging on the detector 13 measured by the detector 13 at this wavelength at this wavelength and the ratio of the intensity of the measured radiation S impinging on the detector 13 measured by the detector 13 at this wavelength is determined as the logarithm of the ratio.

[0080] The invention is not limited to Figure 2 the spectral determination sensor 1 shown in and can also be used in a similar manner in combination with other spectral determination sensors known from the prior art. Similarly, it can also be used in combination with spectral determination sensors that do not have their own radiation sources, which receive the measured radiation S along the received signal path and determine and provide the associated measured spectrum

[0081] In Figure 2 the example shown in Figure 2 the evaluation device 5 is arranged, for example, in a device 17 - such as a transmitter or a measuring transducer - connected to the spectral determination sensor 1. Alternatively, however, the entire measuring device 100 can also be designed as a spectral determination sensor 1' (shown as an alternative in

[0082] by a dashed line), which includes the evaluation device 5. Figure 1 The measuring method described in detail below, and of course the measuring device 100 that performs the measuring method in a similar manner, can be used in many different applications in which interference substances such as air bubbles, gas bubbles or particles visible to the naked eye may occasionally occur in the medium 3. Examples include breweries, water monitoring facilities, wastewater treatment plants (such as municipal wastewater treatment plants or industrial wastewater treatment plants used in certain industries), laundries or drinking water supply plants. In these applications, the measuring method shown in is used to detect interference substances in the medium 3 - the size of which is greater than the wavelengths

[0083] contained within the measuring wavelength range of the spectral determination sensors 1, 1' Included are, for example, wavelengths in the ultraviolet range, in the visible range and / or in the near infrared range, such as wavelengths in the wavelength range from 190 nm to 2500 nm or wavelengths in a portion of this wavelength range.

[0084] Interfering substances present in the medium 3, such as air or gas bubbles and / or macroscopic particles, usually have sizes in the millimeter range or at least in the micrometer range, which are significantly larger than the measuring wavelength range. The wavelength in In this context, macroscopic particles are understood to be solids, such as small stones or pieces of sand, whose size is greater than that of solids suspended in the medium 3 which may be responsible for the turbidity of the medium 3 and which are generally microscopically small.

[0085] Figure 1 The measuring method shown in FIG. 1 comprises a first method step V1 in which a spectrometric sensor, such as Figure 2 The spectrometric sensors 1, 1' of the measuring device 100 shown in FIG. 1 continuously determine the wavelength of the medium 3 in the predetermined measuring wavelength range. The measured spectrum in .

[0086] In a second method step V2, the continuously determined measurement spectrum is used to identify and discard those measurement spectra during whose recording optical saturation OS of the spectrometric sensor 1, 1' has occurred .

[0087] Combined with measured spectra in the form of absorption spectra Optical saturation occurs if the absorption occurring along the optical path 11 exceeds an upper limit of measurable absorption values, above which further additional absorption no longer results in measured spectral values ​​that can be resolved using the measurement. Combined with the measured spectrum in the form of an intensity spectrum , optical saturation occurs if the intensity of the measuring radiation S becomes so low that the measured spectral values, which are formed as intensity values ​​in this case, fall below a lower limit value of measurable intensity values, below which a further additional reduction in the intensity no longer leads to a reduction in the measured intensity values ​​which can be resolved using the measurement. In both cases, the specific limit value is a constant or even wavelength-dependent property of the spectrometric sensor 1, 1', which can in each case be experimentally measured or numerically determined for the respective spectrometric sensor.

[0088] Thus, for example, combining a measured spectrum designed as an intensity spectrum , the second method step V2 is continued such that if a particular measured spectrum If at least one or the minimum value of the spectral values drops below the associated lower limit value, the occurrence of optical saturation OS is established. Similarly, for example, in combination with the measured spectrum in the form of an absorption spectrum , the second method step V2 continues such that if a specific measured spectrum of the spectral values at least one or the maximum value of which exceeds the associated upper limit value, the occurrence of optical saturation OS is established.

[0089] In order to be able to determine a reliable measured value mv of the measured variable or each measured variable in both the presence and absence of interfering substances, in the third method step V3, for at least one or each measured spectrum remaining after the second method step V2 has been carried out , a medium spectrum representing the spectral characteristics of the medium 3 is determined .

[0090] The third method step V3 is based on the following consideration: In each measured spectrum , multiple effects are superimposed, and each measured spectrum can be at least approximately described as the sum or weighted sum of sub-spectra assigned to individual effects. These sub-spectra include a first sub-spectrum T1 corresponding to wavelength-dependent absorption in the medium 3 ( ), and may also include a second sub-spectrum T2 corresponding to scattering caused by the turbidity of the medium 3 ( ). In the presence of interfering substances in the medium 3, such as at least one air bubble entering the optical path 11 in the medium 3, at least one gas bubble entering the optical path 11 in the medium 3, and / or at least one visually observable particle entering the optical path 11 in the medium 3, the sub-spectrum additionally includes a third sub-spectrum T3 caused by the perturbation ( ). In Figure 3 an example of the absorption spectra of all three sub-spectra T1 ( ), T2 ( ), T3 ( ) is shown. The measured wavelength range shown by the example in Figure 3 includes wavelengths in the ultraviolet range and in the visible range .

[0091] As can be seen from Figure 3 , the first sub-spectrum T1 corresponding to wavelength-dependent absorption in the medium 3 and shown by way of example in Figure 3 within the measured wavelength range ( ) has a wavelength dependence corresponding to the wavelength-dependent absorption coefficient of the medium 3, and generally over most of the measured wavelength range ​is not linear and its orientation towards Figure 3 the measurement wavelength range shown in has a sharp decrease at the long - wave edge. In contrast, the second sub - spectrum T2 ( ) caused by the turbidity or scattering of usually microscopically small suspended solids generally has a substantially continuous series, and its wavelength dependence also has a sharp decrease towards Figure 3 the measurement wavelength range shown in at the long - wave edge.

[0092] The spectral series of the third sub - spectrum T3 ( ) caused by interfering substances depends on the interaction between the radiation and specific interfering substances. These interactions basically include some of the radiation being absorbed in the interfering substances and / or some of the radiation being reflected and / or scattered by the interfering substances.

[0093] Gaseous interfering substances have a much lower optical density than the liquid medium 3. Therefore, the partial length of the optical path 11 passing through gaseous interfering substances - such as air bubbles and / or gas bubbles - is usually too short for the radiation component absorbed in these interfering substances to cause the third sub - spectrum T3 ( ) to depend substantially on the wavelength. On the premise that the gaseous interfering substances have dimensions significantly larger than the wavelengths in the measurement wavelength range , the radiation component reflected or scattered at these interfering substances will not cause the third sub - spectrum T3 ( ) to depend substantially on the wavelength.

[0094] Interfering substances in solid form - such as visible particles - have a much higher optical density than the liquid medium 3. This results in some of the radiation hitting these interfering substances along the optical path 11 within the entire measurement wavelength range being almost completely absorbed, while some is reflected and / or scattered. The almost complete absorption within the entire measurement wavelength range provides at least an approximately constant contribution to the third sub - spectrum T3 ( ) within the entire measurement wavelength range . On the premise that the visible particles have dimensions significantly larger than the wavelengths in the measurement wavelength range , the radiation component scattered and / or reflected by these interfering substances will not cause the third sub - spectrum T3 ( ) to depend substantially on the wavelength.

[0095] Therefore, the third sub - spectrum T3 ( ) for air bubbles, gas bubbles, and / or visible particles - whose sizes are larger than the wavelengths in the measurement wavelength range and which include the beam path 11 entering the medium 3 —— the interfering substance has at least approximately a constant offset with a spectral order.

[0096] The medium spectrum representing the spectral characteristics of medium 3 can be at least approximately described as the sum of a first sub-spectrum T1 ( ) and a second sub-spectrum T2 ( ). A third sub-spectrum T3 ( ) is additionally superimposed on this sum spectrum caused by medium 3 in the presence of an interfering substance in the measured spectrum , provided that the interfering substance has a size significantly larger than the wavelengths in the measured wavelength range , and this third sub-spectrum at least approximately corresponds to a constant offset .

[0097] Based on this knowledge, in a first sub-step V3.1 of the determination of the associated medium spectrum for this or each remaining measured spectrum in the third method step V3, a verification method is performed, in which a specific measured spectrum and a reference of the spectral characteristics expected in the absence of an interfering substance in a predetermined spectral range including at least one reference wavelength are used to verify whether the specific measured spectrum contains an offset caused by an interfering substance that occurred in medium 3 when recording the corresponding measured spectrum . If there is an offset , it is preferably also determined simultaneously in the first sub-step V3.1 the magnitude of the offset, for example in the form of an offset value.

[0098] In this verification method, a range in which the absorption coefficient change of medium 3 is less than a predetermined spectral variance depending on the wavelength and / or below a predetermined limit value is used as the predetermined spectral range.

[0099] For example, the sum of the squares of the differences between the values of the absorption coefficients of the wavelengths in the spectral range and the average of these values in the spectral range is used to calculate the spectral variance.

[0100] As can be seen from the first sub-spectrum T1 ( Figure 3 ) shown in and the second sub-spectrum T2 ( Figure 3 ) shown in , the wavelength dependence of the absorption coefficient of medium 3 and its measurement wavelength range Figure 3 including wavelengths in the ultraviolet and visible light ranges in Values in the long-wavelength range both decrease continuously as the wavelength increases. In the case of these wavelengths, the influence of any turbidity of the medium 3 is also small at the same time, and there is no or only very little wavelength dependence.

[0101] Therefore, a spectral range including at least one wavelength in the visible light range - such as, at least one wavelength in the range from 380 nm to 800 nm - and / or at least one wavelength in the near-infrared range - such as, at least one wavelength in the range from 800 nm to 2500 nm - is particularly suitable as the predetermined spectral range. The predetermined spectral range relative to the measurement wavelength range The position where it is located depends on the measurement wavelength range The size of.

[0102] A suitable spectral range is, for example, a range including at least one reference wavelength located within the sub-range Of the measurement wavelength range Inside, A range corresponding to the sub-range Of the measurement wavelength range And / or a range including at least one reference wavelength located outside the measurement wavelength range Outside. Depending on the measurement wavelength range The size of, each sub-range of the measurement wavelength range Is, for example, the long-wavelength edge wavelength range, the short-wavelength edge wavelength range or the intermediate wavelength sub-range of the measurement wavelength range For example, the long-wavelength edge wavelength range, the short-wavelength edge wavelength range or the intermediate wavelength sub-range of the measurement wavelength range Of the long-wavelength edge wavelength range, the short-wavelength edge wavelength range or the intermediate wavelength sub-range.

[0103] Combined with a predetermined spectral range including at least one single reference wavelength , The reference of the spectral characteristics expected in the absence of interferents includes, for example, for the corresponding reference wavelength , The spectral values expected in the absence of interferents , Of the reference value , .

[0104] As an exemplary embodiment of it, Figure 4 Shows the measurement spectrum recorded in the measurement wavelength range shown in Figure 3 In the presence of interferents Of, the measurement spectrum , The measurement spectrum For the reference wavelength located within the sub-range of the measurement wavelength range in this case Of the measurement wavelength range Inside Spectral values of , and the associated reference value expected in the absence of interfering substances at the reference wavelength . Example.

[0105] Combined with Figure 3 and Figure 4 shown as an example and including wavelengths in the ultraviolet and visible light ranges of the measurement wavelength range , the sub-range is preferably the long-wavelength edge wavelength range of the measurement wavelength range . Similarly, for the measurement wavelength range including wavelengths in the visible light range , the sub-range is also preferably the long-wavelength edge wavelength range of the measurement wavelength range . In both cases, for example, wavelengths greater than or equal to 380 nm or even greater than or equal to 500 nm are suitable as the reference wavelength within the measurement wavelength range .

[0106] Combined with the measurement wavelength range including wavelengths in the visible light and / or near-infrared ranges , depending on the size of the measurement wavelength range , the sub-range is, for example, the long-wavelength edge wavelength range, short-wavelength edge wavelength range, or intermediate wavelength range of the measurement wavelength range . In these cases, depending on the size of the measurement wavelength range , wavelengths greater than or equal to 380 nm, greater than or equal to 500 nm, greater than or equal to 800 nm, or greater than or equal to 830 nm are suitable as the reference wavelength within the measurement wavelength range .

[0107] Since the reference wavelength is within the measurement wavelength range , for example, the spectral value of the reference spectrum recorded by the spectroscopic sensors 1, 1' in the absence of interfering substances at the reference wavelength is used to pre-determine the reference value expected in the absence of interfering substances at the reference wavelength . .

[0108] In this exemplary embodiment, the method step V3.1 continues such that a specific measurement spectrum is determined at the reference wavelength and the spectral value is compared with the reference value the difference between them, and if the difference is greater than a predetermined tolerance, the difference and the offset are established to exist. This tolerance is, for example, based on the measured spectrum of the spectral values and is a tolerance predetermined based on the sensor-specific measurement accuracy. In this embodiment, the offset is given by the value of the difference and is determined according to, for example .

[0109] Figure 4 The embodiment shown in where the measured spectrum is recorded in the absence of interfering substances of the spectral values in a subrange of the measurement wavelength range is particularly advantageous in applications where it is at least approximately constant

[0110] As another exemplary embodiment Figure 5 shows a portion of the measured spectrum recorded in the presence of interfering substances and, in this case, a reference wavelength outside the measurement wavelength range and a reference value expected in the absence of interfering substances in this case Combined with a measurement wavelength range including wavelengths in the ultraviolet and / or visible light range the reference wavelength outside the measurement wavelength range is much larger than the wavelengths included in the measurement wavelength range For a measurement wavelength range including wavelengths in the ultraviolet range the reference wavelength outside the measurement wavelength range is, for example, a wavelength in the visible light range, such as a wavelength greater than or equal to 380 nm or even greater than or equal to 500 nm. For a measurement wavelength range including wavelengths in the visible light range the reference wavelength outside the measurement wavelength range is, for example, a wavelength in the near-infrared range, such as a wavelength greater than or equal to 800 nm or even greater than or equal to 830 nm . For a measurement wavelength range including wavelengths in the visible light range the reference wavelength outside the measurement wavelength range is, for example, a wavelength in the near-infrared range, such as a wavelength greater than or equal to 800 nm or even greater than or equal to 830 nm .

[0111] Combined with a measurement wavelength range including wavelengths in the near-infrared range the reference wavelength outside the measurement wavelength range is outside the measurement wavelength range​​​ For example, much smaller than the measurement wavelength range the wavelengths in In this regard, for these measurement wavelength ranges a suitable reference wavelength located outside the measurement wavelength range is, for example, a wavelength in the visible light range, such as a wavelength greater than or equal to 380 nm or even greater than or equal to 500 nm.

[0112] Figure 5 In the embodiment shown in for different wavelengths 、 two or more spectral values 、 in the measurement spectrum are used to perform extrapolation to determine the spectral value of the reference wavelength located outside the measurement wavelength range missing from the measurement spectrum . As shown in for this purpose, it is preferably to use the spectral values that appear at wavelengths Figure 5 、 、 、 where the wavelengths 、 、 are located in the edge range of the measurement wavelength range facing the reference wavelength located outside the measurement wavelength range

[0113]

[0114] Using the spectral values and the associated wavelengths included in the measurement spectrum, extrapolation is performed by means of a polynomial, for example, a linear or quadratic polynomial. Alternatively, an exponential function can be used to perform extrapolation.

[0113] In this exemplary embodiment, the reference value expected in the reference wavelength in the absence of interfering substances is, for example, the spectral value established by extrapolating the reference spectrum recorded by the spectroscopic sensors 1, 1' in the absence of interfering substances at the reference wavelength predetermined.

[0114] Similar to the previously described embodiment, in this embodiment, the reference wavelength is also determined ——Hereby established by extrapolation using the measured spectrum ——The spectral value and the reference value The difference between them, and if the difference is greater than a predetermined tolerance, an offset is established The existence of. Offset The magnitude of is given by the value of the difference and is calculated according to, for example To calculate.

[0115] This embodiment is particularly advantageous in applications where the spectral values of the measured spectrum recorded in the edge range Facing the reference wavelength Outside the measurement wavelength range Can be at least approximately described by a straight line in the absence of interfering substances Of the measured spectrum The spectral value Of the.

[0116] As another exemplary embodiment, Figure 6 Shows a portion of the measured spectrum recorded in the presence of interfering substances in a sub-range Of the measurement wavelength range In. In this exemplary embodiment, the spectral range for checking for interfering substances includes a sub-range Of the measurement wavelength range And the reference R includes a reference curve Of the spectral values expected in the sub-range In the absence of interfering substances Of.

[0117] Depending on the size of the measurement wavelength range In this case, a sub-range is also formed For example, in the manner described in the exemplary embodiment previously incorporated Figure 4 In. Thus, in combination with a measurement wavelength range including wavelengths in the ultraviolet and visible ranges or including wavelengths in the visible range The sub-range Is preferably the long-wave edge wavelength range corresponding to the measurement wavelength range And / or a range including wavelengths greater than or equal to 380 nm or greater than or equal to 500 nm.

[0118] In combination with a measurement wavelength range including wavelengths in the visible and / or infrared ranges Depending on the size of the measurement wavelength range The sub-range For example, is the measurement wavelength range The long-wavelength edge wavelength range, the short-wavelength edge wavelength range, or the intermediate wavelength sub-range and / or a range including wavelengths greater than or equal to 380 nm, greater than or equal to 500 nm, greater than or equal to 800 nm, or greater than or equal to 830 nm.

[0119] Due to the sub-range being located within the measurement wavelength range the reference order expected in this wavelength range in the absence of interfering substances is pre-determined, for example, based on the spectral order of the spectral values of the reference spectrum recorded by means of the spectrometric sensors 1, 1' in the absence of interfering substances in the sub-range .

[0120] In Figure 6 the embodiment shown, in method step 3.1, a wavelength-dependent auxiliary function defined in the sub-range is set, such as , which corresponds to the sum of the products of the offset variable U and the scaling factor G and the spectral reference order . Then the value pair [U min ; G min of the offset variable U and the scaling factor G is determined, where the difference between the auxiliary function and a specific measurement spectrum within the sub-range is minimized. In order to determine the value pair [U min ; G min of the offset variable U and the scaling factor G that minimizes the difference, the least squares method is used, for example. Alternatively, other minimization methods and / or curve fitting methods known in the prior art can also be used.

[0121] Similar to the exemplary embodiment described previously, this embodiment also proceeds such that when the value U min of the offset variable U that minimizes the difference is greater than a predetermined tolerance, the presence of an offset is established. Here, the magnitude of the offset is given by the value U min of the offset variable U that minimizes the difference and is determined, for example, according to .

[0122] This embodiment is particularly advantageous in applications where the spectral values of the measurement spectrum recorded in the sub-range of the measurement wavelength range in the absence of interfering substances have a certain degree of non-linear wavelength dependence.

[0123] After the verification method performed in the first sub-step V3.1, for each verified measurement spectrum Determine the medium spectrum . As Figure 1 shown, then a discrimination is made as to whether a particular measurement spectrum has an offset . For a measurement spectrum that does not have an offset , the associated medium spectrum is determined in the second sub-step V3.2 such that it is equal to the measurement spectrum . For a measurement spectrum that has an offset , in the third sub-step V3.3, a difference spectrum is determined by subtracting the previously determined offset from the measurement spectrum according to its magnitude, and the associated medium spectrum is determined such that it is equal to the difference spectrum determined in this way. Finally, in method step V4, the spectral values of the medium spectrum

[0124] determined in this way are used to determine the measured value mv of the measurement variable to be measured, such as the concentration of the analyte in medium 3, the nitrite content of medium 3, the nitrate content of medium 3, the chemical oxygen demand of medium 3, the biological oxygen demand of medium 3, the color of medium 3, the organic carbon content of medium 3, the organic carbon content of medium 3 dissolved in medium 3, and / or the turbidity of medium 3. To determine the measured value mv, depending on the measurement variable, for example, methods known in the prior art are used, by means of which the measured value of a specific measurement variable is determined using the measurement spectra in the prior art. For example, a specific integral total value determined based on the spectral values in the entire measurement wavelength range

[0125] is used, or the spectral values of the medium spectrum that occur in the presence of one or more specific wavelengths are used to determine the measured value mv of the turbidity of medium 3. Other methods known in the prior art include, in particular, the MOD calculation rule, also known among experts as the chemometric model, using which the measured value mv of the measurement variable can be calculated using the spectral values of the measurement spectra, such as the concentration of the analyte in medium 3, the nitrite content, the nitrate content, the organic carbon content, the organic carbon content dissolved in medium 3, and the chemical and / or biological oxygen demand of medium 3. Since the medium spectrum is equal to the measurement spectrum in the absence of interfering substances and corresponds to the measurement spectrum compensated for interfering substances in the presence of interfering substances ​, these methods can be easily adopted from the prior art and applied in the fourth method step V4.

[0126] Figure 1 The measurement method shown in, for example, is designed as a computer-implemented method. In this regard, the present invention also includes a computer program, which includes computer-readable program code elements that, when executed on a computer, cause the computer to use the measurement spectra determined by the spectrometric sensors 1, 1'. to perform Figure 1 the method steps V2 to V4 shown in and based on the measurement spectra or at least perform the method steps V2 to V3 based on the measurement spectra to determine the medium spectrum and provide the medium spectrum and / or the measurement value mv of the measurement variable or each measurement variable. In addition, the present invention includes a computer program product that has at least one computer-readable medium on which at least the computer program is stored.

[0127] In a measuring device for performing Figure 1 the method shown in, such as Figure 2 the measuring device 100 shown in, the evaluation device 5 includes, for example: signal processing means 5a, which is designed to determine the associated medium spectrum based on the measurement spectra determined by the spectrometric sensors 1, 1' in the above manner ; and measurement value determination means 5b, which is designed to determine and provide the measurement value mv of the measurement variable or each measurement variable using the medium spectrum ). The signal processing means 5a includes, for example, a data processing device, such as a computer or a microprocessor, and a computer program stored in a memory and executable by the data processing device. By means of this computer program, the medium spectrum can be determined using the measurement spectra

[0128] . Similarly, the measurement value determination means 5b includes, for example, a data processing device, such as a computer or a microprocessor, and a computer program stored in a memory and executable by the data processing device. Using this computer program, the measurement value mv can be determined using the medium spectrum to determine the medium spectrum . to determine the measurement value mv.

[0129] The measured values mv can each be read out, output, and / or transmitted, for example in the form of data or signals, wirelessly and / or via a line, via an interface 19 of an output device 21 of a measuring device 100 connected to an evaluation device 5, to a higher-level unit than the measuring device 100, such as a control room, a process control system, a distributed control system, or a programmable logic controller. Alternatively or additionally, the output device 21 includes, for example: a display device 23 for displaying the measured values mv, such as a monitor; and / or a display element 25, such as a light-emitting diode, which indicates when an offset has been established using a verification method and / or indicates the measurement spectrum on which a specific measured value mv is based and whether it contains an offset .

[0130] List of reference numerals

[0131] 100 Measuring device 13 Detector

[0132] 1 Spectrometric sensor 15 Measuring electronics unit

[0133] 3 Medium 17 Device (transmitter)

[0134] 5 Evaluation device 19 Interface

[0135] 7 Radiation source 21 Output device

[0136] 9 Spectrometric unit 23 Display device

[0137] 11 Optical path 25 Display element

Claims

1. A spectrometric measurement method for measuring at least one measured variable in a liquid medium (3), in which interfering substances can be present, said interfering substances comprising interfering substances having a size greater than a predetermined measurement wavelength range ( ) within the wavelength ( ) in the spectrometric measurement method: The spectrometric sensor (1, 1') is used to continuously determine the medium (3) in the measuring wavelength range ( ) within the measured spectrum ( ), Identify and discard those measured spectra during which optical saturation of the spectrometric sensor (1, 1') has occurred ), For the remaining measured spectra ( ) or at least one of the remaining measured spectra ( ), the medium spectrum is determined by the following operations ( ): A validation method is performed in which a predetermined reference and a specific measured spectrum of spectral characteristics expected in the absence of interferents within a predetermined spectral range are compared. ) was used to verify the specific measured spectrum ( ) contains the specific measurement spectrum recorded in the ( ) caused by the presence of an interfering substance in the medium (3) ( ), and, if the offset exists ( ), the magnitude of the shift is determined, wherein the variation of the absorption coefficient of the medium (3) in the predetermined spectral range is smaller than a predetermined spectral variance depending on the wavelength and / or is below a predetermined limit value, and If the measured spectrum ( ) does not include the offset ( ), then the medium spectrum ( ) is determined so that the medium spectrum is equal to the measured spectrum ( ), and if the measured spectrum ( ) contains the offset ( ), then the medium spectrum ( ) is determined so that the medium spectrum is equal to that obtained by dividing the measured spectrum by ( ) minus the offset ( ) and The medium spectrum ( ) is used to determine the measured values ​​(mv) of the or each measured variable and to make these values ​​available.

2. The measuring method according to claim 1, wherein: The measurement wavelength range ( ) includes wavelengths in the ultraviolet range, the visible range and / or the near infrared range, and / or wavelengths in the wavelength range from 190 nm to 2500 nm or a portion of this wavelength range, and The spectral range includes at least one wavelength in the visible range, at least one wavelength in the range from 380 nm to 800 nm, at least one wavelength in the near infrared range and / or at least one wavelength in the range from 800 nm to 2500 nm.

3. The measuring method according to claims 1 to 2, wherein: The predetermined spectral range includes a wavelength range within the measurement wavelength range ( ) of the sub-range ( ) within the reference wavelength ( ), The reference includes at this reference wavelength ( ) is the reference value of the spectral value expected in the absence of interfering substances ( ),and The verification method comprises a first verification method, in which: Determine the specific measurement spectrum ( ) for the reference wavelength ( ) of the spectral values ​​( ) and the reference value ( ), and If the difference is greater than a predetermined tolerance, an offset having a magnitude corresponding to the value of the difference is established ( )’s existence.

4. The measuring method according to claim 3, wherein: a) The measurement wavelength range ( ) includes wavelengths in the ultraviolet and visible light ranges or includes wavelengths in the visible light range and is within the measurement wavelength range ( ) within the reference wavelength ( ) is within the measurement wavelength range ( ) and / or greater than or equal to 380 nm or greater than or equal to 500 nm, or b) The measurement wavelength range ( ) includes wavelengths in the visible and / or near-infrared range and is located within this measurement wavelength range ( ) within the reference wavelength ( ) is within the measurement wavelength range ( ) in the longwave edge wavelength range, the shortwave edge wavelength range or the intermediate wavelength range, and / or is greater than or equal to 380nm, greater than or equal to 500nm, greater than or equal to 800nm, or greater than 830nm.

5. The measurement method according to claim 3 or 4, wherein the reference wavelength ( ) in the absence of interfering substances by means of the spectrometric sensor (1, 1') predetermines the spectral values ​​of the reference spectrum for the reference wavelength ( ) The expected reference value ( ).

6. The measuring method according to claims 1 to 5, wherein: The predetermined spectral range is included in the measurement wavelength range ( ) other than the reference wavelength ( ), The reference has a wavelength in the measurement range ( ) other than the reference wavelength ( ) and the reference value of the spectral value expected in the absence of interfering substances ( ),and The verification method includes a second verification method, in which: By using the measured spectrum ( ) contained in different wavelengths ( , ) at two or more spectral values ​​( , ) is extrapolated to determine the wavelength range within the measurement ( ) other than the reference wavelength ( ) in the measured spectrum from ( ) missing spectral values ​​( ),in, The different wavelengths ( , ) is within the measurement wavelength range ( ) and facing the measurement wavelength range ( ) other than the reference wavelength ( )'s edge range ( )middle, Determine the reference wavelength ( ) in the spectral value determined by extrapolation ( ) and the reference value ( ), and If the difference is greater than a predetermined tolerance, an offset having a magnitude corresponding to the value of the difference is established ( )’s existence.

7. The measuring method according to claim 6, wherein: a) The measurement wavelength range ( ) includes wavelengths in the ultraviolet and / or visible range and is located within this measurement wavelength range ( ) other than the reference wavelength ( ) than the measurement wavelength range ( ) in the wavelength ( ) is much larger, b) The measurement wavelength range ( ) includes wavelengths in the ultraviolet range and lies within this measurement wavelength range ( ) other than the reference wavelength ( ) is in the visible range and / or is greater than or equal to 380 nm or even greater than or equal to 500 nm, c) The measurement wavelength range ( ) includes wavelengths in the visible range and is located within this measurement wavelength range ( ) other than the reference wavelength ( ) is in the near infrared range and / or is greater than or equal to 800 nm or greater than or equal to 830 nm, or d) The measurement wavelength range ( ) includes wavelengths in the near infrared range and is located within this measurement wavelength range ( ) other than the reference wavelength ( ) than the measurement wavelength range ( ) in the wavelength ( ) is much smaller, lies in the visible light range and / or is greater than or equal to 380nm or greater than or equal to 500nm.

8. The measuring method according to claims 6 to 7, wherein: At the reference wavelength ( ) is the reference value expected in the absence of interferents ( ) is based on the reference wavelength ( ) in the absence of interfering substances by means of the reference spectrum recorded by means of the spectrometric sensor (1, 1'), the spectral values ​​established by extrapolation ( ) is predetermined.

9. The measuring method according to claims 1 to 8, wherein: The predetermined spectral range includes the measurement wavelength range ( ) of the sub-range ( ), The reference includes the case where no interferents are present within the sub-range ( ) is the reference level of the spectral values ​​expected in ),and The verification method includes a third verification method, in which: Set in the sub-range ( ) defined in the wavelength-dependent auxiliary function ( ), the wavelength-dependent auxiliary function corresponds to the offset variable (U) and the scaling factor (G) with the reference series ( ), Determine the value pair (U) of the offset variable (U) and the scaling factor (G) min , G min ), for the value pair, the auxiliary function ( ) and in the sub-range ( ) within the specific measured spectrum ( ) has the smallest difference, and If the value of the offset variable (U) that minimizes the difference (U min ) is greater than a predetermined tolerance, then establishing the value (U) of the offset variable (U) that minimizes the difference min ) corresponds to the size of the offset ( )’s existence.

10. The measuring method according to claim 9, wherein: The measurement wavelength range ( ): a) includes wavelengths in the ultraviolet and visible ranges or wavelengths in the visible range, and the sub-range ( ) is the measurement wavelength range ( ) and / or including a wavelength greater than or equal to 380 nm or greater than or equal to 500 nm, or b) includes wavelengths in the visible and / or infrared range, and the sub-range ( ) is the measurement wavelength range ( ), and / or includes a wavelength greater than or equal to 380 nm, greater than or equal to 500 nm, greater than or equal to 800 nm, or greater than or equal to 830 nm, and / or Based on the fact that in the absence of interfering substances, the spectrometric sensor (1, 1') ) to predetermine the spectral order of the reference spectrum recorded in the absence of interfering substances in the measuring wavelength range ( ) of the sub-range ( ) is expected in the reference series ( ).

11. The measuring method according to claims 1 to 10, wherein the spectral value of the medium spectrum ( ) is used to determine the concentration of an analyte contained in the medium (3), the nitrite content of the medium (3), the nitrate content of the medium (3), the chemical oxygen demand of the medium (3), the biological oxygen demand of the medium (3), the color of the medium (3), the organic carbon content of the medium (3), the organic carbon content of the medium (3) dissolved in the medium (3) and / or a measured value (mv) of the turbidity of the medium (3).

12. A measuring device (100) for carrying out the measuring method according to claims 1 to 11, the measuring device Designed as a spectrometric sensor (1') or comprising a spectrometric sensor (1), wherein the spectrometric sensor (1, 1') is designed to continuously determine and provide the medium (3) in the predetermined measuring wavelength range ( ) in the measured spectrum ( ),as well as An evaluation device (5), wherein the evaluation device (5): The invention comprises a signal processing device (5a) which is designed to detect, based on the measured spectrum ( ) to determine the medium spectrum ( ),as well as The measured value determination device (5b) is designed to determine the measured value based on the medium spectrum ( ) to determine and provide a measured value (mv) of the or each measured variable.

13. The measuring device according to claim 12, comprising an output device (21) connected to the evaluation device (5), wherein: The output device (21): comprising an interface (19) via which the measured value (mv) can be read out, output and / or transmitted in the form of data and / or signals wirelessly and / or via a line, comprising a display device (23) for displaying said measured value (mv), and / or A display element (25) is included, which indicates when a deviation has been determined using the verification method ( ) and / or indicates the presence of the measured spectrum ( ) contains an offset ( ).

14. A computer program comprising computer readable program code elements which, when executed on a computer, cause the computer to use the measurement spectrum ( ) based on the measured spectrum ( ) performs the method steps of the measuring method performed in the measuring method according to claims 1 to 11, or at least determines the medium spectrum ( ) and provide the medium spectrum ( ) and / or a measured value (mv) of the or each measured variable.

15. A computer program product comprising a computer program according to claim 14, and at least one computer readable medium on which at least the computer program is stored.

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