DE10260046B4 - Method for checking the reactivity of an electronic sensor and device for carrying out the method - Google Patents

Abstract

Method for checking the reactivity of an electronic sensor for gaseous and / or liquid media, in particular a measuring electrode for determining chemical or physical quantities, after soaking or covering of the sensor surface by the surrounding medium or components contained therein, as a result of which the response behavior of the sensor with respect to the material to be measured Medium is impaired, the sensor being subjected to a comparison medium during the check as part of a test routine and a comparison sensor value being detected, the sensor being operated in a measurement mode and being switched from the measurement mode to the test routine and, in the process, the comparison medium being fed to the sensor is characterized by
- Acquisition and storage of sensor value series related to the comparison medium and
- Comparison of these sensor value series, recorded and stored one after the other with a time interval, based on the comparison medium and deriving information about the state of the sensor from the change and temporal development of sensor value series recorded at different times with respect to the comparison medium.

Description

The The invention relates to a method for checking the reactivity an electronic sensor for gaseous and / or liquid Media. About that Furthermore, the invention relates to a device for carrying out a such procedure.

sensors for gaseous and / or liquid media are used in particular in the form of measuring electrodes for the determination chemical or physical quantities in many areas of application used. Particularly noteworthy in the context of the invention are waste water treatment, neutralization of media, detoxification (electroplating), Media preparation and media monitoring. There are different measuring electrodes known that can capture different values of media, in particular is in the context of the invention, for example, measuring electrodes as they z. B. be used to detect a pH of a liquid can. Such measuring electrodes are indeed capable of delivering highly precise measured values, provided they be connected to a corresponding analysis measuring unit, but basically the disadvantage that they interact with the medium to be measured, d. H. of mottled or coated the medium or its components be so that they no longer or no longer react sufficiently precisely or quickly can.

Around this basically existing uncertainty of sensors that may change in the longer term in media, especially aggressive media, to counteract it has already become known that the sensors are part of test routines to be loaded with a comparison medium and a comparison sensor value to determine who made a statement about the condition of the sensor. there is usually carried out so that a discrete value is determined is checked and subsequently checked, whether this value is in an allowable Tolerance range or not. If this is the case, a Control unit switched the entire device back into measuring mode, a review in A test routine takes place after a specifiable period of time again.

On corresponding procedure is from the technical information TI 194 C / 07 / DE on the device “Liquisys MCPM 223/253 "the The company Endres and Hauser can be derived.

Out DE 102 09 466 A1 A device and a method for monitoring and regulating process solutions are known, wherein, based on a surface tension measurement according to the bubble pressure method, devices for detecting the surface tension and the concentration of process additive in process solutions for processing and control for a processable internal program flow of the device and coordinates for a generally continuous monitoring of the quality of process solutions and for controlling a device for influencing the process by means of an intelligent computer system, which independently obtains, processes and exchanges process data with a process control system and / or influences the process.

Out DE 44 17 929 A1 is a measuring device for the analysis of measuring gas components or measuring gas aerosols with a detector device, at least one valve, a pump and a test gas preparation for calibration as well as with gas-carrying lines, via which, depending on the position of the valve (s), the sample gas or the test gas can be fed to the detector (s), known. In order to be able to largely utilize the life of the sensor elements and the analysis operation of the measuring device is not interrupted when a sensor element is replaced or during a calibration mode, it is additionally provided that the detector device contains at least two sensors which are connected in parallel in terms of gas flow and that the sensors are jointly connected to one Test gas preparation are connected to a sample gas supply and to a pump.

Out DE 43 18 891 A1 a gas trace measuring system is known which consists of an electrochemical sensor with at least one working electrode, a counter electrode and optionally a reference electrode. The measurement signal generated by the sensor and correlated with a gas concentration is amplified and displayed with the aid of analog evaluation electronics. The evaluation electronics is connected to a diagnostic circuit which temporarily changes the potential set between the working electrode and the counterelectrode during a test cycle for a two-electrode sensor and the potential set between the working electrode and the reference electrode for a three-electrode sensor after a predetermined time function, which causes a change in the current signal at a working electrode.

The The invention has for its object a method with the features to improve the preamble of claim 1 and in particular so train that more detailed Statements about the sensor status and in particular predictions about a possible future service life and accuracy or quality of the sensor become. If necessary, it should also be possible to take automatic measures to recondition the sensor and / or the supervisor the system provided with the sensor to indicate that an exchange of the sensor must be done at short notice.

According to the teaching of the An Proverb 1 solved in that sensor value series related to the comparison medium are recorded and saved and a comparison of these sensor value series successively recorded and stored with a time interval is carried out based on the comparison medium and a statement about the state of the sensor from the change and temporal development of too different Time series of recorded sensor values based on the comparison medium is carried out with each other.

• 1. über das zeitliche Elektrodenansprechverhalten,
• 2. die absolute Genauigkeit hinsichtlich des zu ermittelnden pH-Wertes,
• 3. hinsichtlich einer Reaktionszeit zum erneuten Erreichen des tatsächlichen Meßwertes bezogen auf das Meßmedium nach Abschluß einer Vergleichsmessung,
• 4. hinsichtlich des Reaktionsverhaltens bei Verwendung eines eventuellen Spülmediums,
• 5. hinsichtlich des Verschmutzungsgrades der Elektroden,
• 6. hinsichtlich einer zukünftigen Elektrodenalterung,
• 7. vorausschauende Bestimmung des Zeitpunktes eines automatischen Elektrodenwechsels.

In particular, the test routine is first carried out at the same time intervals, for example daily. B. 50 or 100 measured values, which then result in a daily sensor value series. The daily sensor value series, for example of successive days, are then compared with one another and a statement is derived from the deviation of the daily value series in which state the sensor is. All of this is not related to the medium being measured, but to the reference medium. The invention is based on the knowledge that a sensor that is already relatively heavily soaked or covered with residues of the measuring medium and therefore cannot or only very poorly react to the measuring medium, still responds well to a comparison medium and still relates to the comparison medium shows relatively clear deviations with regard to any changes in the sensor surface. This knowledge is exploited, the sensor is run in the comparison medium within the test routine and the measurement series recorded are compared with one another in order to find out a trend as to whether and, if necessary, how long the sensor can still be used to meet the required quality and accuracy requirements. For this purpose, pre-stored "empirical values" with regard to the sensor behavior and the correspondingly recorded sensor value series are used. In a positive way, this test method results in an evaluation of the measuring electrodes, if the evaluation is positive, the measuring electrode can be used further, expensive buffer solutions which are used in an analysis-calibration method are not necessary for the method or can be used sparingly, and only if the analysis comparison method or test method shows that the probe no longer displays the correct values, the more complex analysis comparison method must be initiated and The expensive buffer solutions with which the probe is applied and a standard calibration procedure is used .. Tests in field tests have shown that, for example, a medium whose pH value should be kept within 10 tolerances due to the production process , the value 10.3 pH starts up again relatively precisely, although the probe has already been falsified by the measuring medium, but increasingly leaves the value of a comparison medium of, for example, 8 pH at intervals. It is therefore possible to draw conclusions about electrode contamination, reaction and the like by comparing the series of sensor values recorded at different times in a test method with a comparison medium. In particular, the following statements can be made regarding the electrodes:

• 1. about the temporal electrode response,
• 2. the absolute accuracy with regard to the pH value to be determined,
• 3. with regard to a reaction time for reaching the actual measured value again based on the measuring medium after completion of a comparison measurement,
• 4. with regard to the reaction behavior when using a possible rinsing medium,
• 5. regarding the degree of contamination of the electrodes,
• 6. regarding future electrode aging,
• 7. Predictive determination of the time of an automatic electrode change.

in the Within the scope of the invention it is possible to make statements about the State of the sensor from the time history of individual sensor values based on the comparison medium. If in this context spoken of the time course of individual sensor value series this affects individual sensor value series, for example can be recorded in a day within a few minutes.

It can be beneficial before feeding of the comparison medium is a rinsing medium supply, around the sensor of remaining stocks of the measuring medium. It is also possible to use water as a comparison medium, for example rinsing medium at the same time can be.

prove the changes of sensor values recorded at different times as serious, in other words, these can be settled on one interpret looming or existing occupancy of the sensor surface, then can In a further development of the invention, additional detergent cycles are automatically initiated. It is also possible dependent on the degree of change also the rinsing time to extend or shorten it if this is from the starch of changes can be derived.

If the degree of changes in sensor values recorded at different times allows the conclusion that the sensor has been decalibrated, then a calibration of the sensor is automatically initiated within the scope of the invention, for which purpose buffer solutions are supplied to the sensor and recalibrated based on the sensor value based on the buffer solutions).

Then will the sensor is again charged with the comparison medium and thereby checks whether the Sensor value in the range of a permissible Hysteresis.

The Sensor values are updated as part of the process, i. H. in cyclical intervals with previously stored sensor values in a control unit compared and evaluated, this ensures consistently that the sensor sufficiently precise works and a malfunction of the equipped with the sensor Facility is excluded. By using "fuzzy logic" methods, the method can be self-learning be trained, d. H. z. B. adjusted cycle times, shortened or one renewal of the test routine time interval are initiated automatically.

In Further development of the invention is also possible, also from the comparison of sensor values recorded in succession at different times evaluate the temporal sensor response, d. H. statement about that how quickly the sensor reacts to certain changes. Furthermore the degree of contamination of the sensor can be determined and statements about aging-related Deviations of the sensor values are made.

The The result of the series of values among one another also permits a decision the existence Electrode change is required, this electrode change can be displayed or carried out automatically. It is also possible automatically display a necessary recalibration of the sensor, which then immediately or to a later Be initiated by the user of the system can. It is also within the scope of the invention to shorten the time intervals between the comparative measurements automatically to make or display. The same applies to an increase in rinsing cycles or sensor cleaning cycles. At long last is it also possible to indicate whether the sensor can still be calibrated overall or not. The decision that the sensor can no longer be calibrated will then logically lead to an indication that the sensor needs to be replaced is.

The Invention is based on exemplary embodiments closer in the drawing figures explained. This demonstrate:

1 a comparison diagram relating to pH values of different liquids, the different series of values being recorded on different successive days,

2 1 shows a schematic flow diagram of the method,

3 is a schematic representation of the device for performing the method.

First, reference is made to drawing figure 1. The 8-day comparison chart test run was performed on two different liquids, namely a first liquid with a pH of 9.25 and a second liquid with a pH of 7. The first 30 measured values (plotted on the x-axis of the diagram) relate to the measuring medium, ie the measuring electrode is exposed to a pH 9.25 liquid. From measured value 30 is switched to a comparison medium, with measured value 115 is switched back to the measuring medium. This means that the measured values 31 - 114 refer to a test routine. Of course, it is also possible to make the test routine longer or shorter, or to select a different number of measured values in the routine interval.

in the Within the scope of the invention, time-spaced measured values are now arranged recorded, which are represented as curves in the comparison diagram. The curves are with a – h characterized. First it is significant that in Meßwertebereich based on the medium to be measured due to an already advanced Assignment of the sensor surfaces no significant differences between the series of measurements were found can. The differences are sometimes even in the noise of the measuring electronics.

With regard to the area relating to the test routine, the changes between the series of measurements recorded on successive days are significant. The measurement series a is the lowest, followed by the measurement series b – g. The change by a value of approximately +0.5 pH indicates the increasing occupancy and thus also an increasing inaccuracy of the probe, the comparison medium being chosen such that it does not result in occupancy of the probe. The differences between the series of values that are determined in the value interval of the test routine therefore relate to an occupancy of the sensor surfaces by the medium that is actually to be measured. There is a significant increase in the values for the value series a – g, the degree of contamination of the probe can be derived from the changes. Before the test routine was carried out on November 18, 2002, which resulted in the value series h, the sensor was subjected to a rinsing mode, which leads to a lowering of the values by approximately pH 0.2 to pH 0.3, which is taken as evidence that the sensor surfaces can still be regenerated by flushing. Would - like not - a lowering of the value series in the area of the test routine by an additional rinsing mode is no longer possible, then the conclusion is drawn that the sensor surfaces can no longer be regenerated by exposure to rinsing or cleaning liquid, an exchange of the sensor is then the result.

Further conclusions can based on empirical values from the time history of individual series of values be pulled, namely whether the range of values from the start of the test routine to the end of the test routine falls very quickly to the final value to be reached or whether this is slower, d. H. carrier happens. Finally can also the transition areas Test routine / measuring mode meaningful be about the condition of the sensor, d. H. its responsiveness.

In Drawing Figure 2 is shown a flow diagram, which is essentially for themselves itself speaks. Essentially, a pH measuring device from a measurement mode switched into a test routine, as part of the test routine first a rinse of the sensor surfaces then a comparison medium is fed to the sensor and the pH value measured as part of the test routine. The recorded Meßwertereihen, those for the value series a – h to lead, can with each other be compared or with previously stored further values be compared, the comparison determines whether the test routine pH end value is in the range of a hysteresis or not. Is that the case, the device is returned to the measuring mode, with another flushing can be interposed. If not, different decisions can be made for the Procedures are taken, namely on the one hand an extension the rinsing time be initiated or an automatic calibration, also a automatic cleaning with a cleaning liquid is possible or an electrode change, which is then displayed.

In the 3 The device shown for carrying out the method essentially consists of a first container 1 , in which the medium to be measured is located, a second container 2 to hold a flushing medium, a third container 3 to hold a reference medium, a drain tank 4 and a cleaning concentrate container 5 , A first line 6 is at a drain 8th of the first container 1 connected, lines 7a and 7b flow into an inflow 9 of the first container 1 , Via a third line 10 and intermediate valves 11 - 13 are the containers 5 . 2 and 3 to the lines 6 and 7 connected.

The sensor 14 is located in a flow armature 15 whose entrance to the line 10 is connected, through a valve 16 , which is designed as a changeover valve, the flow armature 15 either liquid can be supplied from the first container, for which purpose a pump 17 is provided or liquids from the containers 2 . 3 or 5 , If the system is operated in measuring mode, the pump 17 , The administration 6 and the switching valve 16 Liquid to be measured via the line 18 the flow armature 15 fed. When the test routine is initiated, the valve 16 closed the valve 12 opened, so that first flushing medium via the line 10 to the sensor 14 arrives. There is a valve 19 switched so that the liquids of the test routine in the drain tank 4 reach. After the rinse cycle, the valve 12 closed and the valve 13 opened so that the sensor 14 with comparison medium from the container 3 is applied. Then through the control unit 20 the sensor values are recorded. After the test routine is completed, the valve 13 closed again and the valve 12 briefly opened for intermediate rinsing and then the valve after completion of this intermediate rinsing process 16 brought back into the position shown, in the medium to be measured via the line 18 is passed over the sensor. The valve 19 is then again in a switching position, so that over the line 7b Liquid to be measured from the sensor into the container 1 is pumped back.

The control unit 20 comprises a timer device to define the length of the respective rinsing cycles, measuring cycles, comparison cycles or cleaning cycles and to initiate them accordingly. In addition, a memory unit and a comparator unit are provided, both of which can be achieved by a conventional processor. A multiple display 21 can be switched accordingly in order to display the values of interest to the user in a measuring mode or in a test routine mode.

1

first container

2

second container

3

third container

4

drain container

5

Cleaning concentrate container

6

first management

7

management

8th

Outflow 1

9

Inflow of 1

10

third management

11

Valve

12

Valve

13

Valve

14

sensor

15

Flow fitting

16

Valve

17

pump

18

management

19

Valve

20

control unit

21

Multiple Display

Claims (13)

Reactivity verification procedure an electronic sensor for gaseous and / or liquid Media, especially a measuring electrode to determine chemical or physical quantities after sooting or assignment of the sensor surface through the surrounding medium or components contained therein, whereby the response behavior of the sensor with regard to the medium to be measured impaired is, the sensor when checking in A test medium is loaded with a comparison medium and a comparison sensor value detected is, the sensor operated in a measuring mode and from the Measuring mode is switched to the test routine and, the comparison medium fed to the sensor is characterized by - Collection and storage of sensor value series related to the comparison medium and - Comparison This series of sensor values recorded and stored one after the other in time based on the comparison medium and derivation of a statement about the State of the sensor from the change and temporal development of at different times recorded sensor value series related to the comparison medium among themselves. A method according to claim 1, characterized by feeding a flushing medium to the sensor before feeding of the comparison medium. A method according to claim 2, characterized in that depending on Degree of change from series of sensor values recorded in succession at different times automatically additional detergent cycles be initiated. Method according to one of the preceding claims, characterized characterized in that depending on Degree of change of sensor values recorded at different points in time automatic extension or shortening the purge is initiated. Method according to one of the preceding claims, characterized characterized in that depending on Degree of change of sensor values recorded at different points in time automatic calibration of the sensor is initiated, for which purpose Sensor a buffer solution supplied and based on the known sensor value based on the buffer solution Recalibration is done. A method according to claim 5, characterized by subsequent application the sensor with the comparison medium and check whether the sensor value in Range of a permissible Hysteresis. Method according to one of the preceding claims, characterized characterized that the Sensor values from successively recorded at different times Sensor value rows continuously with previously saved sensor value rows are compared and evaluated in a control unit. Method according to one of the preceding claims, characterized characterized that a necessary sensor change is displayed and / or carried out automatically. Method according to one of the preceding claims, characterized characterized that automatically a necessary recalibration of the sensor is displayed. Method according to one of the preceding claims, characterized characterized that a shortening the time intervals between comparative measurements based on the comparison medium is made and / or displayed automatically. Method according to one of the preceding claims, characterized characterized that automatically a fuzzy logic process is required increase the rinse cycles and / or Sensor cleaning cycles initiated and / or displayed. Method according to one of the preceding claims, characterized characterized that automatically it is indicated that the Sensor values an inadmissible have a large fluctuation range. Device for carrying out the method for checking the reactivity of an electronic sensor for gaseous and / or liquid media, according to one of claims 1-12 with - a first container ( 1 ) for recording the by the sensor ( 14 ) medium to be checked, a second container ( 2 ) to hold a flushing medium, a third container ( 3 ) to hold a reference medium, a drain tank ( 4 ) and - a first line ( 6 ) at a drain ( 8th ) of the first container ( 1 ) is connected, a second line ( 7 ) at an inflow ( 9 ) of the container ( 1 ) is connected, - a plurality of valves ( 11 . 12 . 13 . 16 . 19 ), so like - a flow armature ( 15 ) in which the sensor ( 14 ) is arranged and which has an inlet to which via the valve ( 16 ) either the exit of the first container ( 1 ) can be connected to the medium to be checked with the sensor ( 14 ) or via the other valves ( 11 - 13 ) the sensor ( 14 ) with flushing medium or reference medium, with an outlet of the flow fitting ( 15 ) via a valve ( 19 ) with the entrance of the first container ( 1 ) can be connected and - an analysis measuring and control unit ( 20 ) with a first group of outputs for controlling the valves ( 11 - 13 . 16 . 19 ), a group of inputs for connecting the sensor outputs, a storage device for storing rows of sensor values, a timer device for automatically repeating the detection of rows of sensor values, with the second container ( 2 ) valve connecting the flushing medium ( 12 ) can be acted upon in the open position to transfer rinsing medium to the sensor ( 14 ) as well as - an electronic comparator, to which pre-stored sensor value series and currently determined sensor value series can be fed based on the comparison medium, and an evaluation unit that, depending on the comparison result, automatically supplies flushing medium or comparison medium to the sensor ( 14 ) with automatic opening and closing of the associated valves ( 11-13 . 16 . 19 ) concerned.