Procedure for evaluating a measuring point

Abstract

The invention relates to a method for evaluating a measuring point, comprising the following steps: - Providing a measuring point (100) with a sensor unit (1), a process medium (2) and a source of interference (3), wherein the sensor unit (1) is suitable for generating a measurement signal, wherein the sensor unit (1) is in contact with the process medium (2) and the process medium (2) is exposed to the source of interference (3), such that the measurement signal has a disturbance signal, - Generating a measurement signal (M) by the sensor unit (1), - Filtering the measurement signal (M) so that a noise signal (S) is obtained, - Evaluating the interference signal (S), - Evaluating the measuring point (100) based on the evaluation.

Description

[0001] The invention relates to a method for evaluating a measuring point and to a measuring point.

[0002] In analytical measurement technology, particularly in water management, environmental analysis, industrial applications such as food technology, biotechnology, and pharmaceuticals, as well as for a wide variety of laboratory applications, measured variables such as pH, conductivity, or the concentration of analytes, such as ions or dissolved gases in a gaseous or liquid medium, are of great importance. These measured variables can be recorded and / or monitored using electrochemical sensors, such as optical, potentiometric, amperometric, voltammetric, or coulometric sensors, or even conductivity sensors.

[0003] These sensors often exhibit cross-sensitivity to disturbances such as pressure (changes), flow (changes), temperature (changes), chemical composition of a process medium, or phase composition of the process medium (e.g., gas bubbles). However, disturbances can, for example, distort the sensor's measured value, disrupt the process, or reduce the sensor's service life.

[0004] To ensure the most accurate measured values ​​possible, hardware or software is used in the sensor to minimize interference with the measured values.

[0005] To evaluate the disturbances, the measuring point, and the process medium, additional sensors can be used to measure the disturbances (e.g., absorption sensors for detecting gas bubbles / foreign substances in liquids). However, these additional sensors make the measuring point more complex, more error-prone, and more costly.

[0006] It is therefore an object of the invention to provide a method which makes it possible to evaluate a measuring point reliably, simply and cost-effectively.

[0007] This object is achieved according to the invention by a method for evaluating a measuring point according to claim 1.

[0008] The method according to the invention comprises: - Providing a measuring point with a sensor unit, a process medium and a source of interference, wherein the sensor unit is suitable for generating a measuring signal, wherein the sensor unit is in contact with the process medium and the process medium is exposed to the source of interference, so that the measuring signal has an interference signal, - Generation of a measuring signal by the sensor unit, - Filtering the measurement signal so that a noise signal is obtained, - Evaluation of the interference signal, - Evaluate the measuring point based on the evaluation.

[0009] The method according to the invention enables a measuring point to be evaluated reliably, easily, and cost-effectively without additional sensors. In particular, for example, in the case of dissolved oxygen measurement using an oxygen sensor, it is possible to determine whether the gassing of the process medium is functioning properly. In particular, it is possible to detect, for example, an interruption in the gassing or foam formation in the process medium. Thanks to the method according to the invention, it is thus possible to generate warning messages in order to intervene in the process control system in a timely manner. This leads to an improvement in the process reliability of the measuring point as well as the quality of the process medium.

[0010] According to one embodiment of the invention, predetermined problem interference signal profiles are stored in the sensor unit and / or the measuring point, wherein the evaluation of the interference signal comprises a comparison of the interference signal with a problem interference signal profile, wherein if the interference signal correlates with the problem interference signal profile, a problem message is generated.

[0011] According to a further embodiment of the invention, before generating the measurement signal, a problem interference signal curve is recorded by the user and stored in the sensor unit and / or the measuring point.

[0012] According to one embodiment of the invention, the interference signal is obtained when filtering the measurement signal by applying mathematical operations to the measurement signal, in particular from a first derivative of the measurement signal, from a subtraction of the measurement signal and a mean value of the measurement signal, or from a subtraction of the measurement signal and the median of the measurement signal.

[0013] According to one embodiment of the invention, when evaluating the interference signal, an interference indicator is formed based on the interference signal, in particular from a sum of the interference signal, a weighted sum of the interference signal, a mean value of the interference signal, a median of the interference signal, a standard deviation of the interference signal, a distribution statistic of the interference signal, a normal distribution of the interference signal, or a range of the interference signal.

[0014] According to one embodiment of the invention, the disturbance indicator is compared with a reference indicator when evaluating the measuring point, wherein if the disturbance indicator deviates from the reference indicator by a predetermined deviation, user information is generated.

[0015] According to one embodiment of the invention, the sensor unit is a gas sensor and the disturbance source is a gas supply with a predetermined gas flow, and the user information comprises a recommended action for regulating the gas flow.

[0016] According to one embodiment of the invention, a Fourier analysis of the interference signal is carried out when evaluating the interference signal.

[0017] According to one embodiment of the invention, the sensor unit is a gas sensor and the interference source is a gas supply with a predetermined gas flow, wherein when evaluating the measuring point at least one property of the gas flow, in particular a frequency of gas bubbles, a residence time of gas bubbles at the sensor unit, is determined.

[0018] The above-mentioned object is also achieved by a measuring point according to claim 10.

[0019] The measuring point according to the invention comprises a sensor unit, a process medium and a source of interference, wherein the sensor unit is suitable for carrying out the method according to the invention for evaluating a measuring point.

[0020] The invention is explained in more detail with reference to the following description of the figures. They show: - Fig. 1: a schematic representation of a measuring point with a sensor unit according to the invention, - Fig. 2: a schematic representation of the measuring point from Fig. 1 with foam formation, - Fig. 3: an exemplary representation of a measurement signal M, - Fig. 4: an example representation of an interference signal S.

[0021] Fig. 1 shows an exemplary measuring point 100 with a sensor unit 1, a process medium 2, a source of interference 3, a process container 10 and an agitator 11.

[0022] The sensor unit 1 is arranged in the process container 10 and is in contact with the process medium 2. The sensor unit 1 is suitable for generating a measurement signal M. This means that the sensor unit 1 is sensitive to a specific analyte, for example oxygen, in the process medium 2 and generates a measurement signal M that depends on the concentration of the analyte in the process medium 2. For example, the sensor unit 1 is a gas sensor, in particular an oxygen sensor, preferably an optical oxygen sensor. The sensor unit 1 is suitable for processing the measurement signal M. The sensor unit 1 comprises, for example, a memory (not shown) and a so-called transmitter (not shown), which is suitable for converting measured raw signal values ​​into display values ​​and communicating them to a user.Communication to a user occurs, for example, via a display (not shown) at the measuring point 100 or by means of a wired or wireless transmission to a control center.

[0023] The process medium 2 is, for example, a pharmaceutical liquid which is prepared using the agitator 11.

[0024] The interference source 3 is arranged, for example, in the process vessel 10 and is, for example, a gas supply with a predetermined gas flow 4. The gas bubbles of the gas flow 4 migrate at least partially past the sensor unit 1, whereby the measurement signal M is superimposed by an interference signal S. The gas supply has, for example, a controllable valve 5 to regulate the gas flow 4. In particular, the gas supply is an air or oxygen supply. For example, a dissolved oxygen content of the process medium 2 is increased by means of the oxygen supply.

[0025] The method according to the invention for evaluating the measuring point 100 is described below.

[0026] First, the measuring point 100 described above is prepared in a ready-to-measure state. For this purpose, the sensor unit 1 is in contact with the process medium 2.

[0027] Then the sensor unit 1 generates a measurement signal M. An exemplary measurement signal M is shown in Fig. 3. Due to the effect of the interference source 3 on the process medium 2, the measurement signal M has an interference signal S. As indicated above, the interference signal S is generated, for example, by gas bubbles in the gas flow 4, which is introduced into the process medium 2 and which pass by the sensor unit 1 or briefly adhere to the sensor unit 1.

[0028] The measurement signal M is then filtered to obtain the interference signal S. An example measurement signal M is shown in Fig. 3. A pure signal R, i.e. the measurement signal M without interference signal S, was Fig. 3 is shown dashed. During filtering, the pure signal R is preferably also obtained. The pure signal R is used, for example, to evaluate the current analyte concentration, for example the oxygen content, in the process medium 2. When filtering the measurement signal M, the interference signal S is obtained by applying mathematical operations to the measurement signal M, in particular from a first derivative of the measurement signal M, from a subtraction of the measurement signal M and a mean value of the measurement signal M, or from a subtraction of the measurement signal M and the median of the measurement signal M. The interference signal S isolated from the measurement signal M is in Fig. 4 shown.

[0029] Generally speaking, the measurement signal M is digitally filtered, resulting in a pure signal R that has been cleaned of the noise signal S. This cleaned pure signal R is subtracted from the raw measurement signal, i.e., the measurement signal M. This results in the noise signal S.

[0030] The noise signal S can, for example, be easily obtained from a differentiation of measured values ​​of the measurement signal M, i.e., a time series of measured data. The noise signal S at time i can then be defined using the measurement signal M as: S(i) = M(i) - M(i-1).

[0031] The disturbance signal S is evaluated next. For example, the time series of the disturbance signal S(i) can also be mapped over a time window [im; i] across a number m of time points with measured values ​​into a disturbance indicator SI (or coefficient of determination). This disturbance indicator SI thus serves as a measure of the current disturbance of the process medium 2 or the measured signal M.

[0032] For example, the interference indicator SI is formed based on the interference signal S, in particular from a sum of the interference signal S, a weighted sum of the interference signal S, a mean value of the interference signal S, a median of the interference signal S, a standard deviation of the interference signal S, a distribution statistic of the interference signal S, a normal distribution of the interference signal S, or a range of the interference signal S. Alternatively, it is also possible to form the interference indicator SI by determining frequency components using Fourier analysis. According to one embodiment, the interference indicator SI is formed by the result of a distribution test for, e.g., normal distribution, etc.

[0033] When evaluating the interference signal S, for example, a Fourier analysis of the interference signal S is carried out. If, for example, a stirring frequency of the agitator 11 is known, it is possible to determine, for example by evaluating the frequency spectrum of the interference signal S, to what extent the agitator 11 contributes to the interference signal S. It is conceivable, for example, that the agitator 11 transports a particularly large number of gas bubbles to the sensor unit 1 with each rotation of a paddle wheel, so that the interference signal S is influenced by the stirring frequency of the agitator 11.

[0034] Next, the measuring point 100 is evaluated based on the evaluation of the interference signal S. For this purpose, the interference indicator SI is compared with a reference indicator RI, for example. When evaluating the measuring point 100, a problem situation identified by evaluating the interference signal S is communicated to the user, for example. Preferably, a recommended course of action is issued to the user at the same time to eliminate the problem situation.

[0035] It is also possible to compare the current interference signal S with an upper limit value G1 and a lower limit value G2 (see Fig. 4). If the interference signal S is below the lower limit value G2, it can be assumed, for example, that oxygenation of process medium 2 has not yet begun. If the interference signal S is between the upper limit value G1 and the lower limit value G2, the gassing of process medium 2 is proceeding as expected. If the interference signal S exceeds the upper limit value G1, there is, for example, too much oxygen in process medium 2, which is caused, for example, by foam formation.

[0036] An evaluation of the measuring point 100 in the manner described above and in Fig. The example shown in Figure 4 would then be as follows: If the lower limit value G2 is undershot: “No gassing is taking place”, if neither the lower nor the upper limit value is undershot or exceeded: “Normal gassing is taking place”, if the upper limit value G1 is exceeded: “Caution: Foam formation!”.

[0037] Preferably, when evaluating the measuring point 100, user information is also generated, which contains a specific recommended course of action. For example, if foam formation is detected, the user is instructed to reduce the stirring frequency of the agitator 11 or to reduce the gas flow.

[0038] According to one embodiment, the evaluation described above can, of course, be applied to the interference indicator SI using limit values. In this case, the interference indicator SI is compared, for example, with a reference indicator RI. If the interference indicator SI deviates too significantly, i.e., a maximum deviation is exceeded, foam formation is detected, for example, and user information is generated.

[0039] When evaluating the measuring point 100, for example, at least one property of the gas flow 4 is determined. For example, a frequency of gas bubbles, a size of gas bubbles, and a residence time of gas bubbles at the sensor unit 1 are determined.

[0040] According to one embodiment, the evaluation of the interference signal S comprises a comparison of the interference signal S with a problem interference signal curve. If the interference signal S correlates with the problem interference signal curve, a predetermined problem situation (e.g., foam formation) is detected. Preferably, a corresponding warning message is generated in this case. Upon detection of a problem situation, the evaluation of the measuring point 100 comprises generating a warning message, which is preferably communicated to a control center or output via a user interface, e.g., a display or loudspeaker, directly at the measuring point 100.

[0041] During evaluation, the interference signal S is preferably compared with many problem interference signal profiles stored in the sensor unit 1 and / or the measuring point 100. The problem interference signal profiles were preferably stored there by the manufacturer of the sensor unit 1 during production of the sensor unit 1. These manufacturer-supplied problem interference signal profiles were reproduced, recorded, and stored in the sensor unit 1, for example, for the most common process media of the manufacturer's customers in the manufacturer's test systems. For example, a problem interference signal profile for cell deposits such as bacterial cells or yeast cells, or foam formation on the sensor unit 1 is also recorded and stored in the sensor unit 1.

[0042] Alternatively or complementarily to problem fault signal profiles already stored in sensor unit 1, it is possible for the user to store their own problem fault signal profiles, which are specific in particular for the process medium 2 used by the customer or user, in sensor unit 1 and / or measuring point 100. To do this, the user specifically provokes and controls a predetermined problem situation, for example excessive gassing with oxygen. At the same time, the user records the problem fault signal generated in this way in sensor unit 1 and / or measuring point 100 as a problem fault signal profile. The user preferably stores a warning message associated with this specific problem fault signal. The warning message preferably includes explicit instructions for action to remedy the problem situation: e.g., "Caution, reduce oxygen supply immediately!"If problem interference signal curves are recorded in the measuring point 100, the measuring point 100 naturally comprises a corresponding memory (not shown) which is connected to the sensor unit 1.

[0043] Of course, the user can also store problem signal profiles that resulted from an unexpected problem situation that was recognized and remedied by the user. To do this, the user selects the recorded signal profile before and during the occurrence of the problem situation and stores it as a problem signal profile in sensor unit 1 and / or measuring point 100.

[0044] Thanks to the detection of specific problem signal profiles based on the evaluation of a disturbance signal S or its profile, a specific problem situation can be identified early on so that it can be remedied. Especially for the early detection of foam formation, this prevents a sterile filter (not shown) arranged in the ceiling area of ​​the process vessel 10 in front of an overpressure opening from becoming contaminated by foam.

[0045] Thanks to the possibility of a recording of a problem disturbance signal curve by the user, so that this problem disturbance signal curve is included in the evaluation of the disturbance signal S, it is achieved that individual problem situations which are specific to the process medium 2, the measuring point 100 or the process operated by the user are detected at an early stage.

[0046] This allows the user to avoid expensive additional sensors for detecting problem situations, which reduces the costs and space requirements of the measuring point 100. List of reference symbols 1 sensor unit 2 Process medium 3 Source of interference 4 Gas flow 5 Valve 6 foam 10 process containers 11 Agitator 100 measuring points G1 upper limit G2 lower limit M measurement signal R Pure signal RI Reference Indicator S interference signal SI disturbance indicator

Claims

[1] Method for evaluating a measuring point, comprising the following steps: - Providing a measuring point (100) with a sensor unit (1), a process medium (2) and an interference source (3), wherein the sensor unit (1) is suitable for generating a measuring signal, wherein the sensor unit (1) is in contact with the process medium (2) and the process medium (2) is exposed to the interference source (3), so that the measuring signal has an interference signal, - generating a measuring signal (M) by the sensor unit (1), - filtering the measurement signal (M) so that an interference signal (S) is obtained, - Evaluation of the interference signal (S), - Evaluate the measuring point (100) based on the evaluation. [2] Method according to claim 1, wherein predetermined problem interference signal profiles are stored in the sensor unit (1) and / or the measuring point (100), wherein the evaluation of the interference signal (S) comprises a comparison of the interference signal (S) with a problem interference signal profile, wherein if the interference signal (S) correlates with the problem interference signal profile, a problem message is generated. [3] Method according to claim 1 or 2, wherein before generating the measurement signal (M) a problem interference signal curve is recorded by the user and stored in the sensor unit (1) and / or the measuring point (100). [4] Method according to one of the preceding claims, wherein the interference signal (S) is obtained during filtering of the measurement signal (M) by applying mathematical operations to the measurement signal (M), in particular from a first derivative of the measurement signal (M), from a subtraction of the measurement signal (M) and a mean value of the measurement signal (M), or from a subtraction of the measurement signal (M) and the median of the measurement signal (M). [5] Method according to one of the preceding claims, wherein, when evaluating the interference signal (S), an interference indicator (SI) is formed based on the interference signal (S), in particular from a sum of the interference signal (S), a weighted sum of the interference signal (S), a mean value of the interference signal (S), a median of the interference signal (S), a standard deviation of the interference signal (S), a distribution statistic of the interference signal (S), a normal distribution of the interference signal (S), or a range of the interference signal (S). [6] Method according to claim 5, wherein the disturbance indicator (SI) is compared with a reference indicator (RI) when evaluating the measuring point (100), wherein if the disturbance indicator (SI) deviates from the reference indicator (RI) by a predetermined deviation (A), user information is generated. [7] Method according to claim 6, wherein the sensor unit (1) is a gas sensor and the interference source (3) is a gas supply with a predetermined gas flow (4), and the user information comprises a recommended action for regulating the gas flow (4). [8] Method according to one of the preceding claims, wherein a Fourier analysis of the interference signal (S) is carried out when evaluating the interference signal (S). [9] Method according to one of the preceding claims, wherein the sensor unit (1) is a gas sensor and the interference source (3) is a gas supply with a predetermined gas flow (4), wherein during the evaluation of the measuring point (100) at least one property of the gas flow (4), in particular a frequency of gas bubbles, a residence time of gas bubbles at the sensor unit (1), is determined. [10] Measuring point (100) with a sensor unit (1), a process medium (2) and a source of interference (3), wherein the sensor unit (1) is suitable for carrying out the method according to one of the preceding claims.

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