DE102019134903A1 - Method for controlling an analyzer - Google Patents

Abstract

The invention relates to a method for controlling an analyzer (1) comprising at least the following steps: determining a limit heating power with at least the following sub-steps: repeated measurement of a temperature of the reactor chamber (10) by the temperature sensor (12), Temperature in the memory (14), - repeated heating of the reactor chamber (10) with a predetermined heating output by the heater (11), - storing the respective heating output in the memory (14), - determining the limit heating output based on the highest stored heating output; - measuring the current temperature of the reactor chamber (10); - comparing the current temperature with the last stored temperature; - storing the current temperature in the memory (14); - heating with a current heating power of the reactor chamber (10) by the heater (11 ); - Compare the current heating output with the limit heating output; - Saving the current heating output g into the memory (14); - Output of an error message if the current heating output is greater than the limit heating output and the current temperature is the same as the last stored temperature.

Description

The invention relates to a method for controlling an analyzer.

In analytical measurement technology, especially in the field of water management, environmental analysis, in the industrial sector, e.g. in food technology, biotechnology and pharmacy, as well as for a wide variety of laboratory applications, measured variables such as the pH value, the conductivity, or the concentration of analytes, such as ions or dissolved gases in a gaseous or liquid measuring medium are of great importance. These measured variables can be recorded and / or monitored, for example, by means of electrochemical sensors, such as potentiometric, amperometric, voltammetric or coulometric sensors, or else conductivity sensors. These sensors are often integrated in analyzers.

With the help of analyzers, total parameters such as chemical oxygen demand (COD), total phosphorus (TP) or total nitrogen (TN) can be determined. For this purpose, the sample to be analyzed must be digested in a reactor with the aid of digestion reagent and high temperature before the measurement. In order to set a certain temperature in the reactor, this must be measured in the reactor. This is usually done via a sensor, which is brought as close as possible to the liquid to be heated. The reactor is often made of glass because it is not electrically conductive, has good thermal conductivity, has good chemical resistance and, above all, is permeable to light of certain wavelengths.

A certain overpressure arises during the digestion. This is particularly high when measuring the COD, since the sample is digested at a comparatively high temperature. Due to the complicated design of the reactors and the fact that glass reactors are mainly made by hand, it can happen that the cyclic loading causes the finest cracks to form in the glass, which at high temperatures lead to leaks in the pocket for the temperature sensor. The aggressive reagent mixture, which is often sulfuric acid, can then diffuse through the crack and slowly damage the temperature sensor. In addition, the pure thermal cyclical load can also damage the temperature sensor.

Both cases are then expressed in arbitrary, unreliable temperature values. Since, as described above, the temperature represents the control variable of the reactor heating control, incorrect temperature values lead to uncontrolled heating of the reactor. In the best case, i.e. in the event of a wire break in the sensor, it indicates a very high temperature and the heating goes out, which is done via a temperature limit switch, for example. If, on the other hand, a partial short circuit occurs, a temperature that is too low can be displayed. Then the reactor is heated in an uncontrolled manner and the pressure in the reactor continues to rise until the overpressure device of the reactor responds or the weakest point in the system gives way.

Fuses or bimetal switches are known in the prior art in order to prevent uncontrolled heating of the reactor. These can respond at a predetermined temperature in the reactor and irreversibly or reversibly set the heating current to 0. However, the components have a certain thermal inertia, which is usually too great to intercept the fault or requires a high level of design effort. In addition, fuses, for example, are only manufactured for one-time use and therefore the assembly is no longer functional after being triggered.

In previous reactors, an overpressure device is intended to prevent the glass reactor or the weakest point of the system from bursting and thus preventing the operator from being endangered. However, overpressure devices are often disposable devices, for example in the form of so-called bursting disks, so that a component fails due to the faults described above. This puts the analyzer out of operation for a certain period of time, which some users cannot tolerate.

It is therefore an object of the invention to provide a method for operating an analyzer which avoids putting the analyzer out of operation.

This object is achieved according to the invention by a method according to claim 1.

• - Bereitstellen eines Analysators mit einer Reaktorkammer, einer Heizung, welche dazu geeignet ist, die Reaktorkammer zu heizen, einem Temperatursensor, welcher dazu geeignet ist, eine Temperatur der Reaktorkammer zu messen, einer Steuereinheit, welche mit dem Temperatursensor und der Heizung verbunden ist und einen Speicher aufweist;
• - Ermitteln einer Grenzheizleistung mit zumindest den folgenden Teilschritten:
  • - wiederholtes Messen einer Temperatur der Reaktorkammer durch den Temperatursensor,
  • - Speichern der jeweils gemessenen Temperatur in den Speicher,
  • - wiederholtes Heizen der Reaktorkammer mit einer vorbestimmten Heizleistung durch die Heizung,
  • - Speichern der jeweiligen Heizleistung in den Speicher,
  • - Ermitteln der Grenzheizleistung basierend auf der höchsten abgespeicherten Heizleistung;
• - Messen der aktuellen Temperatur der Reaktorkammer;
• - Vergleichen der aktuellen Temperatur mit der zuletzt gespeicherten Temperatur;
• - Speichern der aktuellen Temperatur in den Speicher;
• - Heizen mit einer aktuellen Heizleistung der Reaktorkammer durch die Heizung;
• - Vergleichen der aktuellen Heizleistung mit der Grenzheizleistung;
• - Abspeichern der aktuellen Heizleistung in den Speicher;
• - Ausgeben einer Fehlermeldung, falls die aktuelle Heizleistung größer als die Grenzheizleistung ist und die aktuelle Temperatur gleich der zuletzt gespeicherten Temperatur ist.

The method according to the invention comprises at least the following steps:

• - Providing an analyzer with a reactor chamber, a heater which is suitable for heating the reactor chamber, a temperature sensor which is suitable for measuring a temperature of the reactor chamber, a control unit which is connected to the temperature sensor and the heater and a Has memory;
• - Determination of a limit heating power with at least the following sub-steps:
  • - repeated measurement of a temperature of the reactor chamber by the temperature sensor,
  • - Storage of the respective measured temperature in the memory,
  • - repeated heating of the reactor chamber with a predetermined heating power by the heater,
  • - Storage of the respective heating output in the memory,
  • - Determination of the limit heating power based on the highest stored heating power;
• - measuring the current temperature of the reactor chamber;
• - Compare the current temperature with the last stored temperature;
• - Save the current temperature in the memory;
• - Heating with a current heating power of the reactor chamber by the heater;
• - Comparing the current heating output with the limit heating output;
• - Storage of the current heating output in the memory;
• - Output of an error message if the current heating output is greater than the limit heating output and the current temperature is the same as the temperature last saved.

The method according to the invention enables the reactor of the analyzer not to be overheated and to switch off the heating before overheating. This prevents the reactor from exploding or having to open a safety valve. Uncontrolled heating when the reactor is full is prevented, which can lead to the escape of a highly corrosive or toxic reaction mixture. This guarantees more security for the user. The reliability and the service life of the analyzer and the reactor are also significantly increased.

According to one embodiment of the invention, the predetermined heating power and / or the current heating power is a heating power averaged over a predetermined time interval.

According to one embodiment of the invention, the predetermined heating power and / or the current heating power is greater than zero when the measured current temperature is below a target temperature.

According to one embodiment of the invention, the step of determining the limit heating power comprises a substep of adding a safety offset.

According to one embodiment of the invention, the step of determining a limit heating power is repeated regularly, so that the limit heating power is regularly adjusted.

According to one embodiment of the invention, the step of determining a limit heating output is repeated until at least 10 heating outputs have been stored. The step of determining a limit heating output is preferably repeated until at least 100 heating outputs have been stored. The step of determining a limit heating output is preferably repeated until at least enough heating outputs have been stored that all heating outputs to be expected in a predetermined period of use have been stored.

According to one embodiment of the invention, the limit heating output corresponds to a maximum heating output of the heater.

According to one embodiment of the invention, in the step of determining a limit heating power, the repeated measurement of a temperature of the reactor chamber and the repeated heating of the reactor chamber are repeated within 10 seconds. In the step of determining a limit heating power, the repeated measurement of a temperature of the reactor chamber and the repeated heating of the reactor chamber are preferably repeated within 5 seconds. Particularly preferably, in the step of determining a limit heating power, the repeated measurement of a temperature of the reactor chamber and the repeated heating of the reactor chamber are repeated within 1 second.

According to one embodiment of the invention, the limit heating power is based on filtering the stored maximum heating power.

According to one embodiment of the invention, the filtering comprises a sliding mean value or median filtering and is based at least on the 3 most recently stored heating outputs. The filtering is preferably based on the 5 most recently stored heating outputs. The filtering is particularly preferably based on the last 10 heating outputs stored.

According to one embodiment of the invention, the memory has a ring memory and the predetermined heating power and the current heating power are written into the ring memory.

• - 1: eine schematische Darstellung eines Analysators für das erfindungsgemäße Verfahren.

The invention is explained in more detail on the basis of the following description of the figures. Show it:

• - 1 : a schematic representation of an analyzer for the method according to the invention.

1 shows an analyzer 1 with a reactor chamber 10 , a heater 11 , a temperature sensor 12th and a control unit 13th , which with the temperature sensor 12th and the heater 11 connected is.

The heating system 11 is suitable for the reactor chamber 10 to heat. The heating system 11 is for example a heating coil. The heating system 11 is for example around the reactor chamber 10 arranged around. In an alternative embodiment, the heater is 11 in a wall of the reactor chamber 10 integrated. In a further embodiment there is the heater 11 for example a heating resistor, which is on the reactor 10 is appropriate. In a further alternative embodiment, the heater is 11 in the reactor chamber 10 arranged.

The temperature sensor 12th is suitable for a temperature of the reactor chamber 10 to eat. The temperature sensor 12th is for example in the reactor chamber 10 arranged. In an alternative embodiment, the temperature sensor 12th in the wall of the reactor chamber 10 arranged. In a further alternative embodiment, the temperature sensor 12th on an outer wall of the reactor chamber 10 arranged.

With the temperature sensor 12th is a temperature sensor that measures the temperature either according to the resistance principle, for example a PT100, PT1000, PTC or NTC, or the temperature using a thermoelectric effect, for example thermocouples of type K, J, N or others .

The control unit 13th assigns a memory 14th on. The memory 14th is for example a ring buffer. Ring buffer is understood to mean that the memory 14th has a limited storage capacity and stores data in such a way that the data stored first are deleted first when the memory is full. In other words, the ring buffer works according to the first-in, time-out principle, also known as the FIFO principle.

The method according to the invention for controlling an analyzer is described below 1 described.

First the analyzer described above 1 provided. This includes that the analyzer 1 is ready for measuring operation. For example, the reactor contains 10 already a process medium. Ideally, the process medium is through, for example, the heater 11 already heated to a desired target temperature. Thus it is a task of the control unit 13th the analyzer 1 intelligent control so that the temperature of the process medium is kept constant at the target temperature for a predetermined time, or if the target temperature is intentionally changed by the user, is kept at this changed target temperature.

• Als erster Teilschritt wird die Temperatur der Reaktorkammer 10, bzw. der Reaktorwand, bzw. des Prozessmediums, je nachdem, wie und wo der Temperatursensor 12 angebracht ist, durch den Temperatursensor 12 wiederholt gemessen. Beispielsweise wird das Messen der Temperatur der Reaktorkammer 10 in vorbestimmten Intervallen wiederholt.
• Beispielsweise wird die Temperaturmessung innerhalb von 10 Sekunden wiederholt.
• Vorzugsweise wird die Temperaturmessung innerhalb von 5 Sekunden wiederholt.
• Besonders bevorzugt wird die Temperaturmessung innerhalb von 1 Sekunde wiederholt. In einer alternativen Ausführungsform wird die Temperaturmessung in einer anderen Zeitspanne wiederholt.

Next, a limit heating power is determined. For this purpose, at least the following sub-steps are carried out:

• The first step is the temperature of the reactor chamber 10 , or the reactor wall, or the process medium, depending on how and where the temperature sensor 12th attached by the temperature sensor 12th measured repeatedly. For example, measuring the temperature of the reactor chamber 10 repeated at predetermined intervals.
• For example, the temperature measurement is repeated within 10 seconds.
• The temperature measurement is preferably repeated within 5 seconds.
• The temperature measurement is particularly preferably repeated within 1 second. In an alternative embodiment, the temperature measurement is repeated in a different period of time.

Then a sub-step of storing the respectively measured temperature in the memory is carried out 14th carried out. In this way, a temperature profile can be created, which will later be used for error detection. Error detection will be discussed in detail later. Saving the temperature is, of course, understood to mean saving the temperature value corresponding to the measured temperature.

A subsequent sub-step includes repeated heating of the reactor chamber 10 with a predetermined heating power through the heater 11 . Here too, for example, as in the temperature measurement sub-step, the predetermined heating power is provided by the heater 11 dispensed during predetermined intervals as well as in memory 14th saved. For example, the predetermined intervals are the same as the intervals in the aforementioned temperature measurement. By saving the heating output, a course of the heating output can be created later. Saving the heating output is of course understood to mean the saving of the heating output value corresponding to the output heating output.

Alternatively, the heater 11 also continuously deliver the predetermined heating power. The predetermined heating power is taken as one over a predetermined time interval, for example averaged heating power recorded. The recording of the heating output is based on filtering the heating output within a time window. The filtering is, for example, a mean value filtering or a median filtering. For example, the filtering is a sliding filtering. The mean value filtering comprises at least 3, preferably 5, particularly preferably 10 most recently stored heating outputs. The filtering takes place alternatively on the basis of an average value of all heating outputs delivered in a period of time. The time span for forming the mean value is, for example, less than 60 seconds, preferably less than 10 seconds, particularly preferably less than 1 second. In this way, in the event of strong fluctuations in the calorific value, so-called heating peaks are smoothed out by the averaging without triggering an error message.
Saving the heating output based on an average value of the heating output is particularly advantageous in a heating mode with continuously emitted heating output, since it enables precise control of the heating system 11 output is possible.

Optionally, a sub-step of comparing the measured temperature with the target temperature is carried out. If the measured temperature is below the target temperature, the predetermined heating power is selected to be greater than zero.

The next step is the heating 11 output predetermined heating power in the memory 14th saved. This is preferably done at the same times as in the temperature storage sub-step. In other words, the predetermined heating power output and the temperature are stored in such a way that the heating power can be assigned precisely to a corresponding measured temperature. A course of the heating output together with the simultaneous course of the temperature can thus be created, which is used later for error detection.

The next step is a sub-step of determining the limit heating output based on the highest stored heating output. This is done, for example, by comparing all stored heating outputs and defining the heating output with the highest value as the limit heating output.

Optionally, a safety offset can be added to the determined limit heating power in a partial step. Thus, the limit heating power is increased by the safety offset. The safety offset is based on empirical values.

Optionally, the step of determining a limit heating output is repeated until at least 10 heating outputs have been stored. This means that at least so many heating outputs have been stored that all heating outputs to be expected in a predetermined period of use have been stored. A predetermined period of use is understood to mean the period of time that is necessary for carrying out a process, for example the so-called unlocking of a process medium. Such a period of time can be, for example, only minutes or a few hours.

In a next step of the process to control the analyzer 1 becomes the current temperature of the reactor chamber 10 measured.

Then the current temperature, with the last one in the memory 14th stored temperature compared. The current temperature is for example at a point in time, for example after a predetermined period of time has elapsed after the last one in the memory 14th stored temperature measurement.

Next is the current temperature in memory 14th saved. When the memory 14th a ring memory is and is full, the oldest stored temperature value is discarded and the currently measured temperature is saved.

Then the reactor chamber 10 with a current heating output by the heater 11 heated. The heating with the current heating power can, as described above, be continuous or interrupted, ie only take place during limited time intervals.

In a following step, the current heating output is compared with the limit heating output. It is thus determined whether the current heating output is above or below the limit heating output.

The current heating output is then stored in the memory 14th saved. If the current heating output is output continuously, an averaged current heating output can be stored, as described above. If the current heating output is only emitted during limited time intervals, a current heating output averaged over the time interval can also be stored here.

In a further step, an error message is output if the current heating output is greater than the limit heating output and the current temperature is the same as the temperature last saved.

In one embodiment, the step of determining the limit heating power is repeated regularly. The determined limit heating powers for each predetermined period of use can be written into a memory and the maximum over the last X determined limit heat powers can be used as a limit value. Thus, the limit heating power is determined by the control unit 13th adjusted regularly. By regularly repeating the determination of the limit heating power, the method is to a certain extent self-learning, since, for example, structural changes caused by aging, for example an increase in resistance of the heating coil of the heater 11 , or environmental influences such as the temperature can be taken into account when determining the limit heating output.

As described above, a sufficient number of heating outputs was preferably used to determine the limit heating output, so that temperature fluctuations in the environment of the analyzer 1 have been sufficiently taken into account. Temperature fluctuations between daytime and nighttime operation, or between summer and winter operation of the analyzer 1 are therefore preferably taken into account when determining the limit heating output.

So the temperature of the reactor chamber rises 10 does not turn on, although the heating power has been increased, there must be a temperature loss, for example due to a crack in the reactor chamber 10 or the temperature sensor 12th itself is faulty, so that, for example, a temperature that is too low is displayed.

The analyzer 1 can also have a temperature sensor for measuring the ambient temperature. In this case, the ambient temperature can be taken into account when detecting the error. If, for example, the ambient temperature drops abnormally quickly, it is to be expected that there is not necessarily a fault if the heating power increases and the temperature of the reactor chamber increases 10 remains constant for a short time. In this case the control unit can 13th give a warning signal instead of an error message.

If the operator changes the target temperature, the limit heating output must be reset and the memory must be reset 14th is refilled from the time the setpoint is changed and a new limit heating output is thus determined.

The invention makes it possible to provide an intelligent control method, which prevents uncontrolled heating when the reactor chamber is filled 10 prevented. Thus, a potential crack formation or a triggering of the overpressure protection in the reactor chamber 10 prevented and a leakage of process medium due to a defective reactor chamber 10 practically impossible.

List of reference symbols

1

Analyzer

10

Reactor chamber

11

heater

12th

Temperature sensor

13th

Control unit

14th

Storage

Claims (11)

A method for controlling an analyzer (1) comprising at least the following steps: - Provision of an analyzer (1) with a reactor chamber (10), a heater (11) which is suitable for heating the reactor chamber (10), a temperature sensor (12) which is suitable for measuring a temperature of the reactor chamber (10) ) to measure, a control unit (13) which is connected to the temperature sensor (12) and the heater (11) and has a memory (14); - Determination of a limit heating power with at least the following sub-steps: - repeated measurement of a temperature of the reactor chamber (10) by the temperature sensor (12), - Storage of the respective measured temperature in the memory (14), - repeated heating of the reactor chamber (10) with a predetermined heating power by the heater (11), - Storing the respective heating power in the memory (14), - Determination of the limit heating power based on the highest stored heating power; - Measuring the current temperature of the reactor chamber (10); - Compare the current temperature with the last stored temperature; - Saving the current temperature in the memory (14); - Heating with a current heating power of the reactor chamber (10) by the heater (11); - Comparing the current heating output with the limit heating output; - Storing the current heating power in the memory (14); - Output of an error message if the current heating output is greater than the limit heating output and the current temperature is the same as the temperature last saved. Procedure according to Claim 1 , wherein the predetermined heating power and / or the current heating power is a heating power averaged over a predetermined time interval. Procedure according to Claim 1 or 2 , the predetermined heating power and / or the current heating power is greater than zero if the measured current temperature is below a target temperature. Method according to one of the preceding claims, wherein the step of determining the limit heating power comprises a substep of adding a safety offset. Method according to one of the preceding claims, wherein the step of determining a limit heating power is repeated regularly, so that the limit heating power is regularly adjusted. Method according to one of the preceding claims, wherein the step of determining a limit heating output is repeated until at least 10 heating outputs have been saved, preferably at least 100 heating outputs have been saved, particularly preferably at least as many heating outputs have been saved that all can be expected in a predetermined usage period Heating capacities have been saved. Method according to one of the preceding claims, wherein the limit heating power corresponds to a maximum heating power of the heater (11). Method according to one of the preceding claims, wherein in the step of determining a limit heating power the repeated measurement of a temperature of the reactor chamber (10) and the repeated heating of the reactor chamber (10) within 10 seconds, preferably within 5 seconds, particularly preferably within 1 second is repeated. Method according to one of the preceding claims, wherein the limit heating power is based on a filtering of the stored maximum heating power. Procedure according to Claim 9 , wherein the filtering comprises a sliding mean value or median filtering and is based at least on the 3, preferably on the 5, particularly preferably on the 10 most recently stored heating powers. Method according to one of the preceding claims, wherein the memory (14) has a ring memory and the predetermined heating power and the current heating power are written into the ring memory.

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