EP1561101A1 - Method and device for monitoring a reference half cell - Google Patents

Method and device for monitoring a reference half cell

Info

Publication number
EP1561101A1
EP1561101A1 EP03789035A EP03789035A EP1561101A1 EP 1561101 A1 EP1561101 A1 EP 1561101A1 EP 03789035 A EP03789035 A EP 03789035A EP 03789035 A EP03789035 A EP 03789035A EP 1561101 A1 EP1561101 A1 EP 1561101A1
Authority
EP
European Patent Office
Prior art keywords
cell
reference half
measuring
operating mode
impedance
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP03789035A
Other languages
German (de)
French (fr)
Inventor
Torsten Pechstein
Katrin Scholz
Sven HÄRTIG
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Endress and Hauser Conducta GmbH and Co KG
Original Assignee
Endress and Hauser Conducta Gesellschaft fuer Mess und Regeltechnik mbH and Co KG
Endress and Hauser Conducta GmbH and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Endress and Hauser Conducta Gesellschaft fuer Mess und Regeltechnik mbH and Co KG, Endress and Hauser Conducta GmbH and Co KG filed Critical Endress and Hauser Conducta Gesellschaft fuer Mess und Regeltechnik mbH and Co KG
Publication of EP1561101A1 publication Critical patent/EP1561101A1/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/416—Systems
    • G01N27/4163—Systems checking the operation of, or calibrating, the measuring apparatus
    • G01N27/4165—Systems checking the operation of, or calibrating, the measuring apparatus for pH meters

Definitions

  • the invention relates to a method and an apparatus for monitoring a reference half-cell, the reference half-cell with a measuring half-cell forming a potentiometric measuring point for determining and / or monitoring an ion concentration of a medium, and with the aid of a measured value determined in the measuring circuit between the measuring half-cell and the reference half-cell the ion concentration of the medium is determined.
  • the potentiometric measuring point for determining the ion concentration in a liquid medium is, for example, a pH sensor.
  • the pH sensor can be designed as a glass electrode or as an ISFET sensor.
  • the voltage that develops between the measuring half-cell and the reference half-cell serves as a measure for the pH value or for the ion concentration of the medium.
  • the basics of pH measurement technology and the construction of pH sensors are described, for example, in the book "Wastewater - Measurement and Control Technology", published by Endress + Hauser GmbH + Co., 2nd edition, p. 81 ff.
  • the pH measuring half-cells are preferably so-called glass electrodes or ISFET sensors. These are widely used in many areas of chemistry, environmental analysis, medicine, industry and water management. The applicant offers and sells both types of sensors for a wide variety of applications. As already mentioned, the glass electrodes and ISFET sensors used for potentiometric measurements usually have reference half cells which form constant potentials to a high degree.
  • Calomel electrodes used.
  • the contact from the reference half cell to the measuring medium is established via a bridge electrolyte.
  • the Bridge electrolyte can be liquid or solidified and generally has to meet certain requirements: On the one hand, it should have little influence on the potential of the reference half-cell; on the other hand, it should form the smallest possible diffusion potential with the measuring medium. If the prerequisites are met, the reference half-cell delivers a process-independent and stable reference signal.
  • Liquid-transferred reference half cells are used in many applications of pH, REDOX and ISE measurement technology.
  • Liquid-transferred reference half-cells have a liquid contact between the process - ie the medium - and the interior of the reference half-cell. This liquid contact is usually designed as a porous ceramic pin with a pore diameter in the ⁇ m range. Due to the process, this porous ceramic can now become blocked. If the ceramic becomes blocked or blocked, the transition is very high-resistance and it is not a low-resistance one
  • interference voltages can impress on the potential of the reference half-cell, which can sometimes significantly impair the measuring accuracy.
  • these interference voltages can correspond to changes in several pH values.
  • the measuring point consequently outputs pH values which no longer reflect the actual ion concentration in the medium.
  • approximately 90% of the incorrect measurements occurring in ion concentration measurements are caused by a malfunction of the reference half-cell.
  • a method has already become known of how a malfunction of a reference half-cell, which is caused by the blocking of the transition between the reference half-cell and the measuring medium, can be recognized.
  • a malfunction of the reference half-cell is recognized by monitoring the impedance of the liquid transfer between the reference half-cell and the measuring medium in the process. As soon as a specified limit value is exceeded, an alarm is set.
  • the measuring point 1 shows the essential components of a pH measuring point 1 as used in measuring technology.
  • the measuring point 1 consists of a measuring half cell 2, a reference half cell 2 and a measuring device 6, which usually measures the voltage between the two half cells 2, 3. This voltage is inversely proportional to the pH of the measuring medium 7.
  • the pH measuring half-cell 2 usually has an internal resistance of 50-1000 M ⁇ . There is a connection to the liquid-transferred reference half-cell 3 via the measuring medium 7. This connection usually has an impedance in the order of magnitude of 1-100 k ⁇ and is therefore several orders of magnitude below the impedance of the measuring half-cell 2.
  • the measuring device 6 determines the voltage between the two half-cells 2 , 3, the
  • Reference half-cell 3 in measuring device 6 is at ground potential. Due to the relatively low impedance of the liquid-transferred reference half-cell 3, the medium 7 up to the glass membrane 4 also lies at the ground potential of the measuring device 6. If blocking occurs on the liquid-transferred reference half-cell 3, electrical interference potentials arise between the measuring half-cell 2 and the reference half-cell 3 noticeable in the measurement. Since the measuring half cell 2 and the reference half cell 3 are electrically connected in series, the sum of the impedances is dominated by the impedance of the measuring half cell 2. Therefore, a simple resistance measurement between the points - and t - as shown in FIG. 1 - does not allow any conclusions to be drawn about the current impedance of the reference half cell 3.
  • a measuring point 1 in a symmetrical circuit.
  • a circuit is outlined in FIG. 2.
  • the measuring half-cell 2 is operated with low resistance against a metal pin 10; the reference half-cell 3 is also measured against the metal pin 10.
  • the metal pin 10 now has the advantage that it does not block.
  • the metal pin 10 does not provide a constant reference potential either, since redox potentials can form there.
  • this is also not important for the measurements by means of the measuring devices 8 and 9, since ultimately the difference between the measured values is formed from the two measurements, as a result of which the influence of changing redox potentials on the metal pin 10 is reduced. Consequently, the impedance measured between the two points - and t is essentially the impedance of the liquid-transferred reference half-cell 2 dependent. This method is therefore ideally suited to detecting a malfunction of the reference half-cell 3 due to blocking.
  • An alarm for the malfunction of the reference half-cell is only triggered when a previously defined limit value is exceeded.
  • the alarm is set completely irrespective of whether the increased value of the impedance of the reference half-cell disturbs the measurement at all or whether the disturbance was so serious before the limit value was reached that the measurement was considerably disturbed at this point.
  • the invention is based on the object of proposing a method and a device which make it possible to specifically monitor the reference half-cell of a measuring point for a malfunction.
  • the object is achieved in that the measuring point is operated intermittently in an operating mode and in a test mode, the ion concentration being measured in the operating mode and the functionality of the reference half-cell being checked in the test mode.
  • the noise component of the measurement signal is determined in the test mode and in the operating mode. It is further proposed that an impedance, in particular a resistor, be activated in the measuring circuit in the test mode to determine the noise component of the measurement signal, and that in
  • the resistor is preferably short-circuited in the operating mode.
  • an impedance changing element is actuated for the purpose of changing or for switching the impedance on, in particular the resistance becomes.
  • the impedance changing element is a switch which is arranged, for example, in parallel with the resistor.
  • the noise components of the measurement signal are measured in the operating mode and in the test mode and that a malfunction of the reference half-cell is recognized on the basis of the ratio of the changes in the noise components in the operating mode and in the test mode and a corresponding message is output.
  • a further development of the method according to the invention makes it possible to make a statement regarding the expected service life of the reference half-cell: for this purpose, the noise components of the measurement signals or the ratios of the changes in the noise components of the measurement signals are continuously stored in the operating mode and in the test mode; a message is issued after which time period the reference half-cell is likely to have a malfunction.
  • control / evaluation unit operates the measuring point intermittently in an operating mode and in a test mode, and in that the control / evaluation unit determines the ion concentration of the medium in the operating mode and the functionality of the in the test mode Reference half cell checked.
  • An impedance in particular a resistor, is preferably provided in the measuring circuit.
  • An advantageous embodiment of the device according to the invention provides that the resistor is short-circuited in the operating mode and the resistor is switched into the measuring circuit in the test mode. It goes without saying that any other type of impedance change in the measuring circuit can be used in connection with the invention.
  • An impedance changing element e.g. B. a switch is provided which is connected in parallel with the resistor. This switch is operated by the evaluation / control unit.
  • An advantageous embodiment of the device according to the invention provides that the control / evaluation unit interprets a change in the ratio of the noise components in the operating mode and in the test mode as soon as it is above a predetermined threshold value in such a way that the reference half-cell works correctly.
  • control evaluation unit outputs a malfunction of the reference half-cell when the ratio of the noise components of the measurement signal in the operating mode and in the test mode is approximately unchanged.
  • control / evaluation unit uses statistical evaluation methods to detect a malfunction or the correct functioning of the reference half-cell.
  • Fig. 4 a diagram in which the ratios of the noise components of the
  • Measuring signals in operating mode and in test mode are shown in different circumstances.
  • Fig. 1 is a known from the prior art measuring point 1 for
  • FIG. 2 shows a circuit known from the prior art for the measuring point shown in FIG. 1, which is used to monitor the reference half-cell 3 of the measuring point 1 for blocking. Both solutions are already sufficiently described in the introduction to the description.
  • measuring point 3 shows a preferred embodiment of the device according to the invention for monitoring the reference half-cell 3 of a measuring point 1, which is used to determine and / or monitor the ion concentration of a medium 7.
  • measuring point 1 is a pH measuring point.
  • the solution according to the invention differs from the known solution shown in FIG. 1 in that a resistor 12 is provided in the measuring circuit, to which a switch 13 is connected in parallel.
  • the switch 13 is closed by the control / evaluation unit 11 in the operating mode or in the measurement mode and opened in the test mode. Consequently, the resistor 12 is short-circuited in the operating mode or the reference half-cell 3 is connected to the ground potential with low resistance, while a voltage drop occurs across the resistor 12 in the test mode.
  • control / evaluation unit 11 The main component of the control / evaluation unit 11 is a microprocessor, which is not shown separately in FIG. 3. Together with an analog / digital converter, which is also not shown separately, this serves to convert, calculate and display the measurement signal or the measurement value.
  • Such rule evaluation units 11 are e.g. already implemented in the pH transmitters offered and sold by the applicant and thus state of the art.
  • the measurement signals usually voltage values, which, for example, reflect the pH of the medium 7, are now by no means constant. Rather, an averaged measured voltage value is always superimposed by noise. If the switch 13 is opened, the reference half-cell 3 is connected to the ground potential via the resistor 12 and the coupling to the ground potential becomes worse. Consequently, depending on the size of the resistor 12, the noise superimposed on the mean value of the measurement signal also increases. However, if the liquid-transferred reference half-cell 3 is blocked and the impedance of the reference half-cell 3 is in the vicinity of the connected resistor 12 or if it is larger than the connected resistor 12, the noise due to the connected resistor 12 changes only insignificantly.
  • the effect is exploited that statements regarding blocking of the reference half cell 3 can be made on the basis of the noise components of the measurement signals in the operating mode and in the test mode.
  • the measurement in test mode only takes a few milliseconds.
  • the previously determined measured value must be held in the hold state during this period. This prevents a faulty measured value from being output for further processing.
  • FIG. 4 shows a diagram in which the ratios of the noise components of the measurement signals in the operating mode and in the test mode are shown under different installation and operating conditions.
  • the four differently marked bars simulate four different working conditions under which a potentiometric measuring point must provide reliable measurement results at its installation location in industrial applications.
  • external electromagnetic interference fields can have a negative effect on the measurements.
  • turbulent, e.g. flowing media also have local interference fields.
  • the bars which are hatched from the top left to the bottom right, are a resting medium 7; in addition, the container in which the medium 7 is located was grounded.
  • the bars hatched from top right to bottom left are turbulent, e.g. around a flowing medium 7.
  • the container is also grounded here. With the empty bars, the container is ungrounded and the medium is at rest. In the case of the dotted bars, the container is ungrounded and the medium is turbulent.
  • Numbers 1 - 5 indicate working conditions in which measuring point 1 is used in different media at different temperatures.
  • Number 1 indicates a medium with a low conductivity a relatively low temperature
  • number 2 refers to a medium with low conductivity at a higher temperature.
  • the measurements take place in an acid at different temperatures.
  • Number 5 indicates the case that the medium is an acid and that the medium is also in a metal vessel.
  • the percentage changes in the noise in the operating mode and in the test mode are shown for all the above-mentioned operating conditions, specifically in the event that the reference half-cell 3 is not blocked. Even in the worst case, the noise component in the operating mode is 5 times larger than the noise component in the test mode.
  • the right-hand part of the bar graph shows the percentage changes in noise in the operating mode and in the test mode for a blocked reference half-cell 3. It can be clearly seen that the noise is almost constant in both modes. According to the invention, an approximately unchanged noise component in the operating mode and in the test mode is a clear indication of a malfunction of the reference half-cell.

Abstract

The invention relates to a method for monitoring a reference half cell (3). Together with a measuring half cell (2), said reference half cell (3) forms a potentiometric measuring point (1) for determining and/or monitoring an ion concentration of a medium (7). The ionic concentration of the medium (7) is determined on the basis of at least one measuring signal detected in a measuring circuit between the measuring half cell (2) and the reference half cell (3). According to the invention, the measuring point (1) is operated intermittently in an operating mode and in a test mode, the ionic concentration being measured in the operating mode, and the functional efficiency of the reference half cell (3) being checked in the test mode.

Description

Verfahren und Vorrichtung zur Überwachung einer Referenzhalbzelle Method and device for monitoring a reference half cell
Die Erfindung bezieht sich auf ein Verfahren und eine Vorrichtung zur Überwachung einer Referenzhalbzelle, wobei die Referenzhalbzelle mit einer Meßhalbzelle eine potentiometrische Meßstelle zur Bestimmung und/oder Überwachung einer lonenkonzentration eines Mediums bildet und wobei anhand eines in dem Meßkreis zwischen der Meßhalbzelle und der Referenzhalbzelle ermittelten Meßwerts die lonenkonzenration des Mediums ermittelt wird.The invention relates to a method and an apparatus for monitoring a reference half-cell, the reference half-cell with a measuring half-cell forming a potentiometric measuring point for determining and / or monitoring an ion concentration of a medium, and with the aid of a measured value determined in the measuring circuit between the measuring half-cell and the reference half-cell the ion concentration of the medium is determined.
Bei der potentiometrischen Meßstelle zur Bestimmung der lonenkonzentration in einem flüssigen Medium handelt es sich beispielsweise um einen pH- Sensor. Der pH-Sensor kann als Glaselektrode oder als ISFET-Sensor ausgebildet sein. Die Spannung, die sich zwischen der Meßhalbzelle und der Referenzhalbzelle ausbildet, dient als Maß für den pH-Wert bzw. für die lonenkonzentration des Mediums. Die Grundlagen der pH-Meßtechnik und der Aufbau von pH-Sensoren sind beispielsweise in dem Buch "Abwasser - Meß- und Regeltechnik", Hrsg: Endress+Hauser GmbH + Co., 2. Auflage, S. 81 ff. beschrieben.The potentiometric measuring point for determining the ion concentration in a liquid medium is, for example, a pH sensor. The pH sensor can be designed as a glass electrode or as an ISFET sensor. The voltage that develops between the measuring half-cell and the reference half-cell serves as a measure for the pH value or for the ion concentration of the medium. The basics of pH measurement technology and the construction of pH sensors are described, for example, in the book "Wastewater - Measurement and Control Technology", published by Endress + Hauser GmbH + Co., 2nd edition, p. 81 ff.
Bevorzugt handelt es sich bei den pH-Meßhalbzellen um sog. Glaselektroden oder um ISFET-Sensoren. Diese finden in vielen Bereichen der Chemie, Umweltanalytik, Medizin, Industrie und Wasserwirtschaft eine breite Anwendung. Für die unterschiedlichsten Anwendungen werden beide Typen von Sensoren von der Anmelderin angeboten und vertrieben. Wie bereits gesagt, weisen die für potentiometrische Messungen benutzten Glaselektroden und ISFET-Sensoren üblicherweise Referenzhalbzellen auf, die in hohem Maße konstante Potentiale ausbilden.The pH measuring half-cells are preferably so-called glass electrodes or ISFET sensors. These are widely used in many areas of chemistry, environmental analysis, medicine, industry and water management. The applicant offers and sells both types of sensors for a wide variety of applications. As already mentioned, the glass electrodes and ISFET sensors used for potentiometric measurements usually have reference half cells which form constant potentials to a high degree.
Bei Glaselektroden werden in der Regel Silber/ Silberchlorid- oderIn the case of glass electrodes, silver / silver chloride or
Kalomelelektroden verwendet. Der Kontakt von der Referenzhalbzelle zum Meßmedium wird über einen Brückenelektrolyten hergestellt. Der Brückenelektrolyt kann flüssig oder verfestigt sein und muß in der Regel bestimmte Voraussetzungen erfüllen: Einerseits soll er das Potential der Referenzhalbzelle wenig beeinflussen; andererseits soll er mit dem Meßmedium ein möglichst kleines Diffusionspotential bilden. Sind die Voraussetzungen erfüllt, so liefert die Referenzhalbzelle ein prozeßunabhängiges und stabiles Referenzsignal.Calomel electrodes used. The contact from the reference half cell to the measuring medium is established via a bridge electrolyte. The Bridge electrolyte can be liquid or solidified and generally has to meet certain requirements: On the one hand, it should have little influence on the potential of the reference half-cell; on the other hand, it should form the smallest possible diffusion potential with the measuring medium. If the prerequisites are met, the reference half-cell delivers a process-independent and stable reference signal.
In vielen Anwendungsfällen der pH-, REDOX- und ISE-Meßtechnik kommen flüssigüberführte Referenzhalbzellen zum Einsatz. Flüssigüberführte Referenzhalbzellen weisen einen Flüssigkontakt zwischen dem Prozeß - sprich dem Medium - und dem Inneren der Referenzhalbzelle auf. Dieser Flüssigkontakt ist üblicherweise als poröser Keramikstift mit einem Porendurchmesser im μm-Bereich ausgebildet. Prozeßbedingt kann nun diese poröse Keramik verstopfen. Tritt eine Verstopfung bzw. Verblockung der Keramik auf, ist der Übergang sehr hochohmig und es ist keine niederohmigeLiquid-transferred reference half cells are used in many applications of pH, REDOX and ISE measurement technology. Liquid-transferred reference half-cells have a liquid contact between the process - ie the medium - and the interior of the reference half-cell. This liquid contact is usually designed as a porous ceramic pin with a pore diameter in the μm range. Due to the process, this porous ceramic can now become blocked. If the ceramic becomes blocked or blocked, the transition is very high-resistance and it is not a low-resistance one
Ankopplung der Referenzhalbzelle an das Medium mehr gegeben. Daher können sich Störspannungen dem Potential der Referenzhalbzelle aufprägen, die die Meßgenauigkeit mitunter erheblich beeinträchtigen können. Im Falle einer pH-Wertmessung können diese Störspannungen durchaus Änderungen von mehreren pH-Werten entsprechen. Als Folge der Störspannungen werden folglich von der Meßstelle pH-Werte ausgegeben, die die tatsächliche lonenkonzentration in dem Medium nicht mehr widerspiegeln. In der Praxis werden übrigens ca. 90% der bei lonenkonzentrationsmessungen auftretenden Fehlmessungen durch eine Fehlfunktion die Referenzhalbzelle hervorgerufen.Coupling of the reference half cell to the medium more given. Therefore, interference voltages can impress on the potential of the reference half-cell, which can sometimes significantly impair the measuring accuracy. In the case of a pH value measurement, these interference voltages can correspond to changes in several pH values. As a result of the interference voltages, the measuring point consequently outputs pH values which no longer reflect the actual ion concentration in the medium. In practice, approximately 90% of the incorrect measurements occurring in ion concentration measurements are caused by a malfunction of the reference half-cell.
Es ist bereits eine Methode bekannt geworden, wie sich eine Fehlfunktion einer Referenzhalbzelle, die durch die Verblockung des Übergangs zwischen der Referenzhalbzelle und dem Meßmedium hervorgerufen wird, erkennen läßt. Nach dieser bekannten Methode wird eine Fehlfunktion der Referenz- halbzelle dadurch erkannt, daß im Prozeß die Impedanz der Flüssigüberführung zwischen der Referenzhalbzelle und dem Meßmedium überwacht wird. Sobald ein vorgegebener Grenzwert überschritten wird, wird ein Alarm gesetzt.A method has already become known of how a malfunction of a reference half-cell, which is caused by the blocking of the transition between the reference half-cell and the measuring medium, can be recognized. According to this known method, a malfunction of the reference half-cell is recognized by monitoring the impedance of the liquid transfer between the reference half-cell and the measuring medium in the process. As soon as a specified limit value is exceeded, an alarm is set.
In Fig. 1 sind die wesentlichen Komponenten einer pH-Meßstelle 1 dargestellt, wie sie in der Meßtechnik zum Einsatz kommt. Die Meßstelle 1 besteht aus einer Meßhalbzelle 2, einer Referenzhalbzelle 2 und einem Meßgerät 6, das üblicherweise die Spannung zwischen den beiden Halbzellen 2, 3 mißt. Diese Spannung ist umgekehrt proportional zum pH-Wert des Meßmediums 7.1 shows the essential components of a pH measuring point 1 as used in measuring technology. The measuring point 1 consists of a measuring half cell 2, a reference half cell 2 and a measuring device 6, which usually measures the voltage between the two half cells 2, 3. This voltage is inversely proportional to the pH of the measuring medium 7.
Die pH-Meßhalbzelle 2 weist üblicherweise einen Innenwiderstand von 50 - 1000 MΩ auf. Über das Meßmedium 7 besteht eine Verbindung zur flüssigüberführten Referenzhalbzelle 3. Diese Verbindung hat üblicherweise eine Impedanz in der Größenordnung von 1-100 kΩ und liegt damit um einige Größenordnungen unter der Impedanz der Meßhalbzelle 2. Das Meßgerät 6 ermittelt die Spannung zwischen den beiden Halbzellen 2, 3, wobei dieThe pH measuring half-cell 2 usually has an internal resistance of 50-1000 MΩ. There is a connection to the liquid-transferred reference half-cell 3 via the measuring medium 7. This connection usually has an impedance in the order of magnitude of 1-100 kΩ and is therefore several orders of magnitude below the impedance of the measuring half-cell 2. The measuring device 6 determines the voltage between the two half-cells 2 , 3, the
Referenzhalbzelle 3 im Meßgerät 6 auf Massepotential liegt. Durch die relativ geringe Impedanz der flüssigüberführten Referenzhalbzelle 3 liegt somit auch das Medium 7 bis an die Glasmembran 4 heran auf dem Massepotential des Meßgeräts 6. Tritt an der flüssigüberführten Referenzhalbzelle 3 eine Verblockung auf, so machen sich elektrische Störpotentiale zwischen der Meßhalbzelle 2 und der Referenzhalbzelle 3 in der Messung bemerkbar. Da die Meßhalbzelle 2 und die Referenzhalbzelle 3 elektrisch gesehen in Reihe geschaltet sind, wird jedoch die Summe der Impedanzen durch die Impedanz der Meßhalbzelle 2 dominiert. Daher läßt eine - wie in Fig. 1 dargestellte - einfache Widerstandsmessung zwischen den Punkten - und t keinen Schluß auf die aktuelle Impedanz der Referenzhalbzelle 3 zu.Reference half-cell 3 in measuring device 6 is at ground potential. Due to the relatively low impedance of the liquid-transferred reference half-cell 3, the medium 7 up to the glass membrane 4 also lies at the ground potential of the measuring device 6. If blocking occurs on the liquid-transferred reference half-cell 3, electrical interference potentials arise between the measuring half-cell 2 and the reference half-cell 3 noticeable in the measurement. Since the measuring half cell 2 and the reference half cell 3 are electrically connected in series, the sum of the impedances is dominated by the impedance of the measuring half cell 2. Therefore, a simple resistance measurement between the points - and t - as shown in FIG. 1 - does not allow any conclusions to be drawn about the current impedance of the reference half cell 3.
Um die Impedanz der Referenzhalbzelle 3 gezielt überwachen zu können, ist es bekannt geworden, eine Meßstelle 1 in symmetrischer Beschaltung zu verwenden. Eine derartige Beschaltung ist in Fig. 2 skizziert. Die Meßhalbzelle 2 wird niederohmig gegen einen Metallstift 10 betrieben; gegen den Metallstift 10 wird auch die Referenzhalbzelle 3 vermessen. Der Metallstift 10 hat nun - im Gegensatz zu der Referenzhalbzelle 3 - den Vorteil, daß er nicht verblockt. Zwar liefert auch der Metallstift 10 kein konstantes Bezugspotential, da sich an ihm Redoxpotentiale ausbilden können. Dies ist für die Messungen mittels der Meßgeräte 8 und 9 jedoch auch nicht von Belang, da letztlich die Differenz der Meßwerte aus beiden Messungen gebildet wird, wodurch sich der Einfluß sich ändernder Redoxpotentiale an dem Metallstift 10 herauskürzt. Folglich ist die zwischen den beiden Punkten - und t gemessene Impedanz im wesentlichen von der Impedanz der flüssigüberführten Referenzhalbzelle 2 abhängig. Damit ist diese Methode bestens dazu geeignet, eine Fehlfunktion der Referenzhalbzelle 3 aufgrund einer Verblockung zu erkennen.In order to be able to monitor the impedance of the reference half-cell 3 in a targeted manner, it has become known to use a measuring point 1 in a symmetrical circuit. Such a circuit is outlined in FIG. 2. The measuring half-cell 2 is operated with low resistance against a metal pin 10; the reference half-cell 3 is also measured against the metal pin 10. In contrast to the reference half-cell 3, the metal pin 10 now has the advantage that it does not block. The metal pin 10 does not provide a constant reference potential either, since redox potentials can form there. However, this is also not important for the measurements by means of the measuring devices 8 and 9, since ultimately the difference between the measured values is formed from the two measurements, as a result of which the influence of changing redox potentials on the metal pin 10 is reduced. Consequently, the impedance measured between the two points - and t is essentially the impedance of the liquid-transferred reference half-cell 2 dependent. This method is therefore ideally suited to detecting a malfunction of the reference half-cell 3 due to blocking.
Die Nachteile der bekannen Lösung sind jedoch nicht zu übersehen:However, the disadvantages of the known solution cannot be overlooked:
- Es muß ein nicht unerheblicher Mehraufwand betrieben werden. Neben dem zusätzlichen Metallstift ist eine aufwendigere Armatur, eine zusätzliche Verkabelung und eine erweiterte Elektronik erforderlich.- There must be a not inconsiderable additional effort. In addition to the additional metal pin, a more complex fitting, additional wiring and expanded electronics are required.
- Ein Alarm für die Fehlfunktion der Referenzhalbzelle wird erst ausgelöst, wenn ein zuvor festgelegter Grenzwert überschritten wird. Der Alarm wird völlig unabhängig davon gesetzt, ob der erhöhte Wert der Impedanz der Referenzhalbzelle die Messung überhaupt stört oder ob die Störung eventuell schon vor Erreichen des Grenzwertes so gravierend war, daß die Messung bereits zu diesem Zeitpunkt erheblich gestört wurde.- An alarm for the malfunction of the reference half-cell is only triggered when a previously defined limit value is exceeded. The alarm is set completely irrespective of whether the increased value of the impedance of the reference half-cell disturbs the measurement at all or whether the disturbance was so serious before the limit value was reached that the measurement was considerably disturbed at this point.
Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren und eine Vorrichtung vorzuschlagen, die es erlauben, die Referenzhalbzelle einer Meßstelle gezielt auf eine Fehlfunktion hin zu überwachen.The invention is based on the object of proposing a method and a device which make it possible to specifically monitor the reference half-cell of a measuring point for a malfunction.
Die Aufgabe wird bezüglich des erfindungsgemäßen Verfahrens dadurch gelöst, daß die Meßstelle intermittierend in einem Betriebsmodus und in einem Testmodus betrieben wird, wobei in dem Betriebsmodus die lonenkonzentration gemessen wird und wobei in dem Testmodus die Funktionstüchtigkeit der Referenzhalbzelle überprüft wird.With regard to the method according to the invention, the object is achieved in that the measuring point is operated intermittently in an operating mode and in a test mode, the ion concentration being measured in the operating mode and the functionality of the reference half-cell being checked in the test mode.
Gemäß einer vorteilhaften Weiterbildung des erfindungsgemäßen Verfahrens ist vorgesehen, daß im Testmodus und im Betriebsmodus der Rauschanteil des Meßsignals ermittelt wird. Weiterhin wird vorgeschlagen, daß im Testmodus zur Ermittlung des Rauschanteils des Meßsignals eine Impedanz, insbesondere ein Widerstand im Meßkreis aktiviert wird und daß imAccording to an advantageous development of the method according to the invention, it is provided that the noise component of the measurement signal is determined in the test mode and in the operating mode. It is further proposed that an impedance, in particular a resistor, be activated in the measuring circuit in the test mode to determine the noise component of the measurement signal, and that in
Betriebsmodus die Impedanz verändert wird. Bevorzugt wird im Betriebsmodus der Widerstand kurzgeschlossen.Operating mode the impedance is changed. The resistor is preferably short-circuited in the operating mode.
Eine vorteilhafte Weiterbildung des erfindungsgemäßen Verfahrens sieht vor, daß zwecks Veränderung bzw. zwecks Zu- und Abschaltung der Impedanz, insbesondere des Widerstandes ein Impedanzveränderungselement betätigt wird. Insbesondere handelt es sich bei dem Impedanzveränderungselement um einen Schalter, der z.B. in Parallelschaltung zu dem Widerstand angeordnet ist.An advantageous development of the method according to the invention provides that an impedance changing element is actuated for the purpose of changing or for switching the impedance on, in particular the resistance becomes. In particular, the impedance changing element is a switch which is arranged, for example, in parallel with the resistor.
Darüber hinaus wird vorgeschlagen, daß die Rauschanteile des Meßsignals im Betriebsmodus und im Testmodus gemessen werden und daß anhand des Verhältnisses der Änderungen der Rauschanteile im Betriebsmodus und im Testmodus eine Fehlfunktion der Referenzhalbzelle erkannt und eine entsprechende Meldung ausgegeben wird.In addition, it is proposed that the noise components of the measurement signal are measured in the operating mode and in the test mode and that a malfunction of the reference half-cell is recognized on the basis of the ratio of the changes in the noise components in the operating mode and in the test mode and a corresponding message is output.
Eine Weiterbildung des erfindungsgemäßen Verfahrens ermöglicht es, eine Aussage hinsichtlich der voraussichtlichen Standzeit der Referenzhalbzelle zu treffen: Hierzu werden die Rauschanteile der Meßsignale bzw. die Verhältnisse der Änderungen der Rauschanteile der Meßsignale im Betriebsmodus und im Testmodus fortlaufend abgespeichert; es wird eine Meldung ausgegeben, nach welcher Zeitspanne die Referenzhalbzelle voraussichtlich eine Fehlfunktion aufweisen wird.A further development of the method according to the invention makes it possible to make a statement regarding the expected service life of the reference half-cell: for this purpose, the noise components of the measurement signals or the ratios of the changes in the noise components of the measurement signals are continuously stored in the operating mode and in the test mode; a message is issued after which time period the reference half-cell is likely to have a malfunction.
Die Aufgabe wird bezüglich der erfindungsmäßen Vorrichtung dadurch gelöst, daß die Regel-/Auswerteeinheit die Meßstelle intermittierend in einem Betriebsmodus und in einem Testmodus betreibt, und daß die Regel- /Auswerteeinheit in dem Betriebsmodus die lonenkonzentration des Mediums bestimmt und in dem Testmodus die Funktionstüchtigkeit der Referenzhalbzelle überprüft. Bevorzugt ist eine Impedanz, insbesondere ein Widerstand in dem Meßkreis vorgesehen. Eine vorteilhafte Ausgestaltung der erfindungsgemäßen Vorrichtung sieht vor, daß im Betriebsmodus der Widerstand kurzgeschlossen ist und der Widerstand im Testmodus in den Meßkreis zugeschaltet ist. Es versteht sich von selbst, daß jede andere Art von Impedanzänderung im Meßkreis im Zusammenhang mit der Erfindung einsetzbar ist.The object is achieved with respect to the device according to the invention in that the control / evaluation unit operates the measuring point intermittently in an operating mode and in a test mode, and in that the control / evaluation unit determines the ion concentration of the medium in the operating mode and the functionality of the in the test mode Reference half cell checked. An impedance, in particular a resistor, is preferably provided in the measuring circuit. An advantageous embodiment of the device according to the invention provides that the resistor is short-circuited in the operating mode and the resistor is switched into the measuring circuit in the test mode. It goes without saying that any other type of impedance change in the measuring circuit can be used in connection with the invention.
Bevorzugt ist ein Impedanzveränderungselement, z. B. ein Schalter vorgesehen, der parallel zu dem Widerstand geschaltet ist. Dieser Schalter wird von der Auswerte-/Regeleinheit betätigt. Eine vorteilhafte Ausgestaltung der erfindungsgemäßen Vorrichtung sieht vor, daß die Regel-/Auswerteeinheit eine Änderung des Verhältnisses der Rauschanteile im Betriebsmodus und im Testmodus, sobald sie über einen vorgegebenen Schwellenwert liegt, dahingehend interpretiert, daß die Referenzhalbzelle korrekt arbeitet.An impedance changing element, e.g. B. a switch is provided which is connected in parallel with the resistor. This switch is operated by the evaluation / control unit. An advantageous embodiment of the device according to the invention provides that the control / evaluation unit interprets a change in the ratio of the noise components in the operating mode and in the test mode as soon as it is above a predetermined threshold value in such a way that the reference half-cell works correctly.
Insbesondere gibt die RegelJAuswerteeinheit eine Fehlfunktion der Referenzhalbzelle aus, wenn das Verhältnis der Rauschanteile des Meßsignals im Betriebsmodus und im Testmodus näherungsweise unverändert ist.In particular, the control evaluation unit outputs a malfunction of the reference half-cell when the ratio of the noise components of the measurement signal in the operating mode and in the test mode is approximately unchanged.
Um 'Ausreißer bei den Meßsignalen' zu eliminieren, verwendet die Regel- /Auswerteeinheit zur Erkennung einer Fehlfunktion bzw. der korrekten Arbeitsweise der Referenzhalbzelle statistische Auswertemethoden.In order to eliminate 'outliers in the measurement signals', the control / evaluation unit uses statistical evaluation methods to detect a malfunction or the correct functioning of the reference half-cell.
Die Erfindung wird anhand der nachfolgenden Zeichnungen näher erläutert. Es zeigt:The invention is illustrated by the following drawings. It shows:
Fig. 1 : eine aus dem Stand der Technik bekannte Meßstelle zur Messung und/oder Überwachung der lonenkonzentration eines Mediums,1: a measuring point known from the prior art for measuring and / or monitoring the ion concentration of a medium,
Fig. 2: eine aus dem Stand der Technik bekannte Beschaltung zwecks Überwachung der Referenzhalbzelle der in Fig. 1 gezeigten Meßstelle,2: a circuit known from the prior art for monitoring the reference half-cell of the measuring point shown in FIG. 1,
Fig. 3: eine bevorzugte Ausführungsform der erfindungsgemäßen Vorrichtung zur Überwachung der Referenzhalbzelle einer potentiometrischen Meßstelle und3: a preferred embodiment of the device according to the invention for monitoring the reference half-cell of a potentiometric measuring point and
Fig. 4: ein Diagramm, in dem die Verhältnisse der Rauschanteile derFig. 4: a diagram in which the ratios of the noise components of the
Meßsignale im Betriebsmodus und im Testmodus bei unterschiedlichen Gegebenheiten dargestellt sind.Measuring signals in operating mode and in test mode are shown in different circumstances.
In Fig. 1 ist eine aus dem Stand der Technik bekannte Meßstelle 1 zurIn Fig. 1 is a known from the prior art measuring point 1 for
Messung und/oder Überwachung der lonenkonzentration eines Mediums 7 dargestellt. Fig. 2 zeigt eine aus dem Stand der Technik bekannte Beschaltung der in Fig. 1 gezeigten Meßstelle, die dazu dient, die Referenzhalbzelle 3 der Meßstelle 1 auf eine Verblockung hin zu überwachen. Beide Lösungen sind bereits in der Beschreibungseinleitung hinreichend beschrieben.Measuring and / or monitoring the ion concentration of a medium 7 shown. FIG. 2 shows a circuit known from the prior art for the measuring point shown in FIG. 1, which is used to monitor the reference half-cell 3 of the measuring point 1 for blocking. Both solutions are already sufficiently described in the introduction to the description.
Fig. 3 zeigt eine bevorzugte Ausführungsform der erfindungsgemäßen Vorrichtung zur Überwachung der Referenzhalbzelle 3 einer Meßstelle 1 , die zur Bestimmung und/oder Überwachung der lonenkonzentration eines Mediums 7 dient. Insbesondere handelt es sich bei der Meßstelle 1 um eine pH-Meßstelle.3 shows a preferred embodiment of the device according to the invention for monitoring the reference half-cell 3 of a measuring point 1, which is used to determine and / or monitor the ion concentration of a medium 7. In particular, measuring point 1 is a pH measuring point.
Die erfindungsgemäße Lösung unterscheidet sich von der in Fig. 1 gezeigten bekannten Lösung dadurch, daß in dem Meßkreis ein Widerstand 12 vorgesehen ist, dem ein Schalter 13 parallel geschaltet ist. Der Schalter 13 wird von der Regel-/Auswerteeinheit 11 im Betriebsmodus bzw. im Meßmouds geschlossen und im Testmodus geöffnet. Folglich ist im Betriebsmodus der Widerstand 12 kurzgeschlossen bzw. die Referenzhalbzelle 3 ist niederohmig mit dem Massepotential verbunden, während im Testmodus an dem Widerstand 12 ein Spannungsabfall auftritt.The solution according to the invention differs from the known solution shown in FIG. 1 in that a resistor 12 is provided in the measuring circuit, to which a switch 13 is connected in parallel. The switch 13 is closed by the control / evaluation unit 11 in the operating mode or in the measurement mode and opened in the test mode. Consequently, the resistor 12 is short-circuited in the operating mode or the reference half-cell 3 is connected to the ground potential with low resistance, while a voltage drop occurs across the resistor 12 in the test mode.
Hauptbestandteil der Regel-/Auswerteeinheit 11 ist ein Mikroprozessor, welcher in der Fig. 3 nicht gesondert dargestellt ist. Dieser dient zusammen mit einem gleichfalls nicht gesondert dargestellten Analog/Digital-Wandler zur Wandlung, Berechnung und Darstellung des Meßsignals bzw. des Meßwerts. Derartige RegelJAuswerteeinheiten 11 sind z.B. in den von der Anmelderin angebotenen und vertriebenen pH-Meßumformern bereits realisiert und damit Stand der Technik.The main component of the control / evaluation unit 11 is a microprocessor, which is not shown separately in FIG. 3. Together with an analog / digital converter, which is also not shown separately, this serves to convert, calculate and display the measurement signal or the measurement value. Such rule evaluation units 11 are e.g. already implemented in the pH transmitters offered and sold by the applicant and thus state of the art.
Die Meßsignale, üblicherweise Spannungswerte, die beispielsweise den pH- Wert des Mediums 7 widerspiegeln, sind nun keineswegs konstant. Vielmehr ist ein gemittelter gemessener Spannungswert immer von einem Rauschen überlagert. Wird der Schalter 13 geöffnet, so ist die Referenzhalbzelle 3 über den Widerstand 12 mit dem Massepotential verbunden und die Ankopplung an das Massepotential wird schlechter. Folglich nimmt in Abhängigkeit von der Größe des Widerstandes 12 auch das dem Mittelwert des Meßsignals überlagerte Rauschen zu. Ist die flüssigüberführte Referenzhalbzelle 3 jedoch verblockt und liegt die Impedanz der Referenzhalbzelle 3 in der Nähe des zugeschalteten Widerstands 12 oder ist sie größer als der zugeschaltete Widerstand 12, so verändert sich das Rauschen durch den zugeschalteten Widerstand 12 nur unwesentlich.The measurement signals, usually voltage values, which, for example, reflect the pH of the medium 7, are now by no means constant. Rather, an averaged measured voltage value is always superimposed by noise. If the switch 13 is opened, the reference half-cell 3 is connected to the ground potential via the resistor 12 and the coupling to the ground potential becomes worse. Consequently, depending on the size of the resistor 12, the noise superimposed on the mean value of the measurement signal also increases. However, if the liquid-transferred reference half-cell 3 is blocked and the impedance of the reference half-cell 3 is in the vicinity of the connected resistor 12 or if it is larger than the connected resistor 12, the noise due to the connected resistor 12 changes only insignificantly.
Erfindungsgemäß wird der Effekt ausgenutzt, daß anhand der Rauschanteile der Meßsignale im Betriebsmodus und im Testmodus Aussagen hinsichtlich einer Verblockung der Referenzhalbzelle 3 getroffen werden können. Die Messung im Testmodus dauert nur wenige Millisekunden. Während dieser Zeitdauer muß der zuvor ermittelte Meßwert im Hold-Zustand gehalten werden. Damit wird verhindert, daß ein gestörter Meßwert zwecks Weiterverarbeitung ausgegeben wird.According to the invention, the effect is exploited that statements regarding blocking of the reference half cell 3 can be made on the basis of the noise components of the measurement signals in the operating mode and in the test mode. The measurement in test mode only takes a few milliseconds. The previously determined measured value must be held in the hold state during this period. This prevents a faulty measured value from being output for further processing.
In Fig. 4 ist ein Diagramm zu sehen, in dem die Verhältnisse der Rauschanteile der Meßsignale im Betriebsmodus und im Testmodus unter unterschiedlichen Einbau- und Betriebsbedingungen dargestellt sind. Die jeweils vier unterschiedlich gekennzeichneten Balken simulieren vier verschiedene Arbeitsbedingungen, unter denen eine potentiometrische Meßstelle an ihrem Einbauort bei industriellen Anwendungen verläßliche Meßergebnisse liefern muß. Bei ungeerdeten Meßmedien können äußere elektromagnetische Störfelder die Messungen negativ beeinflussen. Bei turbulenten, z.B. strömenden Medien treten gleichfalls lokal Störfelder auf.4 shows a diagram in which the ratios of the noise components of the measurement signals in the operating mode and in the test mode are shown under different installation and operating conditions. The four differently marked bars simulate four different working conditions under which a potentiometric measuring point must provide reliable measurement results at its installation location in industrial applications. In the case of unearthed measuring media, external electromagnetic interference fields can have a negative effect on the measurements. In turbulent, e.g. flowing media also have local interference fields.
Bei den Balken, die von links oben nach rechts unten schraffiert sind, handelt es sich um ein ruhendes Medium 7; zusätzlich wurde der Behälter, in dem sich das Medium 7 befindet, geerdet. Bei den Balken, die von rechts oben nach links unten schraffiert sind, handelt es sich um ein turbulentes, z.B. um ein strömendes Medium 7. Auch hier ist der Behälter geerdet. Bei den leeren Balken ist der Behälter ungeerdet und das Medium ist in Ruhe. Im Falle der gepunkteten Balken ist der Behälter ungeerdet, und das Medium ist turbulent.The bars, which are hatched from the top left to the bottom right, are a resting medium 7; in addition, the container in which the medium 7 is located was grounded. The bars hatched from top right to bottom left are turbulent, e.g. around a flowing medium 7. The container is also grounded here. With the empty bars, the container is ungrounded and the medium is at rest. In the case of the dotted bars, the container is ungrounded and the medium is turbulent.
Die Zifferen 1 - 5 kennzeichnen Arbeitsbedingungen, bei denen die Meßstelle 1 in verschiedenen Medien bei unterschiedlichen Temperaturen zum Einsatz kommt. Ziffer 1 kennzeichnet ein Medium mit einer geringen Leitfähigkeit bei einer relativ geringen Temperatur, Ziffer 2 bezieht sich auf ein Medium mit geringer Leitfähigkeit bei einer höheren Temperatur. Im Falle der Ziffern 3 und 4 findet die Messungen in einer Säure bei unterschiedlichen Tempera-turen statt. Ziffer 5 kennzeichnet den Fall, daß es sich bei dem Medium um eine Säure handelt und daß sich das Medium zusätzlich in einem Metallgefäß befindet.Numbers 1 - 5 indicate working conditions in which measuring point 1 is used in different media at different temperatures. Number 1 indicates a medium with a low conductivity a relatively low temperature, number 2 refers to a medium with low conductivity at a higher temperature. In the case of numbers 3 and 4, the measurements take place in an acid at different temperatures. Number 5 indicates the case that the medium is an acid and that the medium is also in a metal vessel.
Im linken Teil des Balkendiagramms sind für alle zuvor genannten Einsatzbedingungen die prozentualen Änderungen des Rauschens im Betriebsmodus und im Testmodus dargestellt, und zwar für den Fall, daß die Referenzhalbzelle 3 unerblockt ist. Selbst im ungünstigsten Fall ist der Rauschanteil im Betriebsmodus um einen Faktor 5 größer als der Rauschanteil im Testmodus. Im rechten Teil des Balkendiagramms sind die prozentualen Änderungen des Rauschens im Betriebsmodus und im Testmodus bei einer verblockten Referenzhalbzelle 3 dargestellt. Es ist klar ersichtlich, daß das Rauschen in beiden Modi nahezu konstant ist. Erfindungsgemäß ist ein näherungsweise unveränderter Rauschanteil im Betriebsmodus und im Testmodus ein klarer Hinweis auf eine Fehlfunktion der Referenzhalbzelle. In the left part of the bar chart, the percentage changes in the noise in the operating mode and in the test mode are shown for all the above-mentioned operating conditions, specifically in the event that the reference half-cell 3 is not blocked. Even in the worst case, the noise component in the operating mode is 5 times larger than the noise component in the test mode. The right-hand part of the bar graph shows the percentage changes in noise in the operating mode and in the test mode for a blocked reference half-cell 3. It can be clearly seen that the noise is almost constant in both modes. According to the invention, an approximately unchanged noise component in the operating mode and in the test mode is a clear indication of a malfunction of the reference half-cell.
BezugszeichenlisteLIST OF REFERENCE NUMBERS
Meßstellemeasuring point
Meßhalbzellemeasuring half
ReferenzhalbzelleReference half-cell
Glasmembranglass membrane
Poröse KeramikPorous ceramics
Widerstandsmeßgerätresistance meter
Mediummedium
Widerstandsmessungresistivity
Widerstandsmessungresistivity
Metallstiftmetal pin
Regel-/AuswerteeinheitControl / evaluation unit
Widerstandresistance
Schalterswitch
Verbindungsleitungconnecting line
Verbindungsleitung connecting line

Claims

Patentansprüche claims
1. Verfahren zur Überwachung einer Referenzhalbzelle (3), wobei die Referenzhalbzelle (3) mit einer Meßhalbzelle (2) eine Meßstelle (1) zur Bestimmung und/oder Überwachung einer lonenkonzentration eines Mediums (7) bildet und wobei anhand zumindest eines in einem Meßkreis zwischen der Meßhalbzelle (2) und der Referenzhalbzelle (3) ermittelten Meßsignals die lonenkonzenration des Mediums (7) bestimmt wird, dadurch gekennzeichnet, daß die Meßstelle (1) intermittierend in einem Betriebsmodus und in einem1. A method for monitoring a reference half-cell (3), the reference half-cell (3) with a measuring half-cell (2) forming a measuring point (1) for determining and / or monitoring an ion concentration of a medium (7), and using at least one in a measuring circuit the ion concentration of the medium (7) is determined between the measuring half-cell (2) and the reference half-cell (3), characterized in that the measuring point (1) intermittently in one operating mode and in one
Testmodus betrieben wird, daß in dem Betriebsmodus die lonenkonzentration gemessen wird und daß in dem Testmodus die Funktionstüchtigkeit der Referenzhalbzelle (3) überprüft wird.Test mode is operated that the ion concentration is measured in the operating mode and that the functionality of the reference half-cell (3) is checked in the test mode.
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß im Testmodus und im Betriebsmodus der Rauschanteil des Meßsignals ermittelt wird.2. The method according to claim 1, characterized in that the noise component of the measurement signal is determined in the test mode and in the operating mode.
3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß im Testmodus zur Ermittlung des Rauschanteils des Meßsignals eine3. The method according to claim 2, characterized in that in the test mode for determining the noise component of the measurement signal
Impedanz im Meßkreis aktiviert wird und daß im Betriebsmodus die Impedanz (12) verändert wird.Impedance is activated in the measuring circuit and that the impedance (12) is changed in the operating mode.
4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, daß zwecks Veränderung der Impedanz (12) ein Impedanzveränderungselement (13) aktiviert wird. 4. The method according to claim 3, characterized in that for the purpose of changing the impedance (12) an impedance changing element (13) is activated.
5. Verfahren nach Anspruch 3 oder 4, dadurch gekennzeichnet, daß als Impedanzveränderungselement (13) ein Schalter betätigt wird, der zwecks Veränderung der Impedanz (12) in Parallelschaltung zu der Impedanz (12) angeordnet ist.5. The method according to claim 3 or 4, characterized in that a switch is actuated as an impedance changing element (13) which is arranged in parallel with the impedance (12) for the purpose of changing the impedance (12).
6. Verfahren nach Anspruch 1 , 2 oder 3, dadurch gekennzeichnet, daß die Rauschanteile des Meßsignals im Betriebsmodus und im Testmodus gemessen werden und daß anhand des Verhältnisses der Änderungen der Rauschanteile im Betriebsmodus und im Testmodus eine Fehlfunktion der Referenzhalbzelle (3) erkannt und eine entsprechende Meldung ausgegeben wird.6. The method according to claim 1, 2 or 3, characterized in that the noise components of the measurement signal are measured in the operating mode and in the test mode and that a malfunction of the reference half-cell (3) is detected and a based on the ratio of the changes in the noise components in the operating mode and in the test mode corresponding message is issued.
7. Verfahren nach Anspruch 6, dadurch gekennzeichnet, daß die Rauschanteile der Meßsignale bzw. die Verhältnisse der Änderungen der Rauschanteile der Meßsignale im Betriebsmodus und im Testmodus fortlaufend abgespeichert werden und daß eine Meldung ausgegeben wird, nach welcher Zeitspanne die Referenzhalbzelle (3) voraussichtlich eine Fehlfunktion aufweisen wird.7. The method according to claim 6, characterized in that the noise components of the measurement signals or the ratios of the changes in the noise components of the measurement signals are continuously stored in the operating mode and in the test mode and that a message is output after which time period the reference half-cell (3) is expected to be Will malfunction.
8. Vorrichtung zur Überwachung einer Referenzhalbzelle (3), wobei die Referenzhalbzelle (3) mit der Meßhalbzelle (2) eine Meßstelle (1) zur Bestimmung und/oder Überwachung einer lonenkonzentration eines Mediums (7) bildet, und wobei eine RegelJAuswerteeinheit (11) vorgesehen ist, die anhand eines in einem Meßkreis zwischen der Meßhalbzelle (2) und der Referenzhalbzelle (3) ermittelten Meßsignals die lonenkonzenration des Mediums (7) bestimmt, dadurch gekennzeichnet, daß die Regel-/Auswerteeinheit (11 ) die Meßstelle (1) intermittierend in einem Betriebsmodus und in einem Testmodus betreibt, und daß die Regel-/Auswerteeinheit (11) in dem Betriebsmodus die lonenkonzentration des Mediums (7) bestimmt und in dem Testmodus die Funktionstüchtigkeit der Referenzhalbzelle (3) überprüft. 8. Device for monitoring a reference half-cell (3), the reference half-cell (3) with the measuring half-cell (2) forming a measuring point (1) for determining and / or monitoring an ion concentration of a medium (7), and a control evaluation unit (11) The ion concentration of the medium (7) is determined on the basis of a measurement signal determined in a measuring circuit between the measuring half-cell (2) and the reference half-cell (3), characterized in that the control / evaluation unit (11) intermittently measures the measuring point (1) operates in an operating mode and in a test mode, and that the control / evaluation unit (11) determines the ion concentration of the medium (7) in the operating mode and checks the functionality of the reference half-cell (3) in the test mode.
9. Vorrichtung nach Anspruch 8, dadurch gekennzeichnet, daß in dem Meßkreis eine Impedanz (12) vorgesehen ist, die im Betriebsmodus verändert, bevorzugt kurzgeschlossen ist und die im Testmodus in den Meßkreis zugeschaltet ist.9. The device according to claim 8, characterized in that an impedance (12) is provided in the measuring circuit, which changes in the operating mode, is preferably short-circuited and which is connected in the test mode in the measuring circuit.
10. Vorrichtung nach Anspruch 9, dadurch gekennzeichnet, daß ein Impedanzveränderungslement (13) vorgesehen ist, das parallel zu der Impedanz (12) geschaltet ist, wobei das Impedanzveränderungselement (13) von der Auswerte-/Regeleinheit (11) betätigt wird.10. The device according to claim 9, characterized in that an impedance change element (13) is provided, which is connected in parallel to the impedance (12), the impedance change element (13) being actuated by the evaluation / control unit (11).
11. Vorrichtung nach Anspruch 8, 9 oder 10, dadurch gekennzeichnet, daß die Regel-/Auswerteeinheit (11) eine Änderung des Verhältnisses der Rauschanteile im Betriebsmodus und im Testmodus, sobald sie über einen vorgegebenen Schwellenwert liegt, dahingehend interpretiert, daß die Referenzhalbzelle (13) korrekt arbeitet.11. The device according to claim 8, 9 or 10, characterized in that the control / evaluation unit (11) interprets a change in the ratio of the noise components in the operating mode and in the test mode, as soon as it is above a predetermined threshold value, in that the reference half-cell ( 13) works correctly.
12. Vorrichtung nach Anspruch 11 , dadurch gekennzeichnet, daß die Regel-/Auswerteeinheit (11) eine Fehlfunktion der Referenzhalbzelle (13) ausgibt, wenn das Verhältnis der Rauschanteile des Meßsignals im Betriebsmodus und im Testmodus näherungsweise unverändert ist.12. The apparatus according to claim 11, characterized in that the control / evaluation unit (11) outputs a malfunction of the reference half-cell (13) when the ratio of the noise components of the measurement signal in the operating mode and in the test mode is approximately unchanged.
13. Vorrichtung nach Anspruch 11 oder 12, dadurch gekennzeichnet, daß die Regel-/Auswerteeinheit (11) zur Erkennung einer Fehlfunktion bzw. der korrekten Arbeitsweise der Referenzhalbzelle (3) statistische Auswertemethoden verwendet. 13. The apparatus of claim 11 or 12, characterized in that the control / evaluation unit (11) for detecting a malfunction or the correct functioning of the reference half-cell (3) uses statistical evaluation methods.
EP03789035A 2002-11-15 2003-11-13 Method and device for monitoring a reference half cell Withdrawn EP1561101A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10253595 2002-11-15
DE10253595A DE10253595A1 (en) 2002-11-15 2002-11-15 Process for monitoring a reference half-cell comprises intermittently operating a measuring point in an operating mode and in a test mode, measuring the ion concentration in the operating mode, and testing the functionality
PCT/EP2003/012668 WO2004046708A1 (en) 2002-11-15 2003-11-13 Method and device for monitoring a reference half cell

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RU2005118428A (en) 2006-01-20
DE10253595A1 (en) 2004-05-27
RU2301419C2 (en) 2007-06-20
US7511504B2 (en) 2009-03-31
WO2004046708A1 (en) 2004-06-03
AU2003293681A1 (en) 2004-06-15
CN1756953A (en) 2006-04-05
US20060125481A1 (en) 2006-06-15

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