DE202018104165U1 - Dosing unit for an automatic analyzer - Google Patents

Abstract

A dosing unit for an automatic analyzer (1) for determining a parameter of a fluid sample, comprising: a housing (42), a dosing vessel (38) disposed in the housing (42) having a first opening communicating with at least a first dosing conduit (4 ) is fluidically connectable, a first level meter (24) disposed above the first opening and configured to generate a signal when a level of a liquid in the metering vessel (38) reaches a first value, and at least one above the first level meter ( 24) arranged second level meter (23) which is adapted to generate a signal when a level of a liquid in the metering vessel (38) reaches a second value which is greater than the first value, characterized in that the housing ( 42) has a through a wall of the housing (42) passing through the cleaning opening (44) with a second opening of the metering vessel (38) f is liuidisch connected, wherein a cross section of the cleaning opening (44) and a cross section of the second opening of the metering vessel (38) at least partially overlap with each other.

Description

The invention relates to a dosing unit for an automatic analyzer and to an automatic analyzer for determining values of a parameter of a liquid sample of a measuring liquid.

In the field of process measuring technology, especially in the field of water and wastewater treatment, it is necessary to regularly monitor the analysis parameters of liquids. For example, cumulative parameters such as COD (chemical oxygen demand), total phosphorus content, total nitrogen content, TOC (total organic carbon content), etc., as well as individual parameters such as nitrate, ammonium or orthophosphate content are to be determined in connection with water treatment in sewage treatment plants or in drinking water treatment. The individual parameters depend on the concentration of a single substance, which is also referred to as analyte. The sum parameters are determined by the proportion of several analytes in the measuring medium. Automated determination of analysis parameters often uses automated analyzers designed to automatically perform wet-chemical analysis procedures involving the treatment of a sample of the measurement fluid, possibly including chemical digestion of the sample. By detecting a measured value correlating with the parameter to be determined on or in the treated fluid sample, such automatic analyzers can determine a value of the parameter.

Frequently, in analyzers, the sample of the measurement liquid to be analyzed is treated by adding one or more reagents, so that a chemical reaction occurs in the reaction mixture thus formed, in which the analyte or, in the case of the determination of sum parameters, all analytes participate are. The treatment may also include digestion of the sample, e.g. for the determination of COD or total nitrogen. Preferably, the reagents are chosen so that the chemical reaction by means of physical methods, for example by an optical measurement, by means of potentiometric or amperometric sensors or by a conductivity measurement is detectable. For example, the chemical reaction may cause a coloration or a color change that is detectable by optical means. The color intensity in this case is a measure of the measured variable to be determined. The measured variable can be determined photometrically, for example, by irradiating electromagnetic radiation, for example visible light, from a radiation source into the reaction mixture and, after transmission through the reaction mixture, being received by a suitable receiver. The receiver generates a measurement signal which is dependent on the intensity of the received radiation and from which the measured quantity can be derived.

Automatic analyzers are already known from the prior art. For example, in DE 102 22 822 A1 . DE 102 27 032 A1 and DE 10 2009 029305 A1 Online analyzers for analyzing samples. Each of these on-line analyzers is designed as a cabinet unit that includes control electronics, reagent storage tanks, standard solutions and cleaning fluids, pumps for pumping and metering the liquid sample and reagent (s) into a measuring cell and an optical measurement pick-up at the measuring cell location. Having reacted with the reagent or the liquid sample. The reagents, standard solutions or cleaning liquids are conveyed from the storage containers and transported into the measuring cell. Accordingly, used liquid is transferred from the measuring cell into a waste container. If the waste container or one or more of the reagent storage containers needs to be replaced, make sure that the hose connections are then reconnected correctly. The hoses and the feed pumps are susceptible to material fatigue and must also be serviced or replaced from time to time.

Out DE 10 2013 114 138 A1 an analyzer is known, which has a metering unit for measuring a defined amount of a measuring liquid as a sample and defined amounts of one or more reagents. This metering unit comprises a transparent metering vessel, on the peripheral wall of which light barriers are arranged at different heights, which serve to detect the reaching of certain water levels in the metering vessel and thus to gauge corresponding volumes to the water levels. For transporting liquid into the metering vessel and out of the metering vessel into the measuring cell of the analyzer, the analyzer comprises two pumps, fluidically connected liquid lines to the metering vessel for supplying various liquids and valves which selectively allow or block transport of liquid through the liquid lines, depending thereon which liquid should be transported to the dosing vessel.

The in the dosing of the in DE 10 2013 114 138 A1 The analyzer described to conductive substances are conveyed with the pump under pressure into the dosing. In this case, some of the liquids can pass through overdosage or by spraying into areas of the metering vessel above the light barriers used for metering, ie in areas that are not regularly washed over by new liquid. In In these areas, constituents of the reagents can precipitate out or crystallize out or dirt particles entrained in the measuring liquid can settle. This leads to a gradual contamination of the wall of the metering vessel. The decrease in volume associated with the settling of contaminants on the vessel wall may affect the precision of the dosage. If the contamination forms in the area of the light barriers, it can also cause a "permanent triggering" of the light barriers due to the permanent blockage of the radiation path of the light barriers that runs through the dosing vessel.

It is the object of the invention to provide a metering unit for an automatic analyzer, which is easy to clean, in order to avoid the above-mentioned problems. This object is achieved by a dosing unit according to claim 1 and an analysis apparatus according to claim 8. Advantageous embodiments are specified in the dependent claims.

• ein Gehäuse, ein in dem Gehäuse angeordnetes Dosiergefäß, das eine erste Öffnung aufweist, die mit mindestens einer ersten Dosierzuleitung fluidisch verbindbar ist, einen oberhalb der ersten Öffnung angeordneten ersten Pegelmesser, der dazu eingerichtet ist, ein Signal zu erzeugen, wenn ein Füllstand einer Flüssigkeit in dem Dosiergefäß einen ersten Wert erreicht, und mindestens einen oberhalb des ersten Pegelmessers angeordneten zweiten Pegelmesser, der dazu eingerichtet ist, ein Signal zu erzeugen, wenn ein Füllstand einer Flüssigkeit in dem Dosiergefäß einen zweiten Wert erreicht, der größer ist als der erste Wert, wobei die erste Öffnung des Dosiergefäßes mit mindestens einer ersten Dosierzuleitung fluidisch verbindbar ist. Das Gehäuse weist eine durch die Gehäusewandung durchgehende Reinigungsöffnung auf, die mit einer zweiten Öffnung des Dosiergefäßes fluidisch verbunden ist, wobei ein Querschnitt der Reinigungsöffnung und ein Querschnitt der zweiten Öffnung des Dosiergefäßes miteinander mindestens teilweise überlappen.

The dosing unit for an automatic analyzer for determining a parameter of a fluid sample according to the invention comprises:

• a housing, a metering vessel disposed within the housing, having a first opening fluidly connectable to at least one first metering conduit, a first level meter disposed above the first opening and configured to generate a signal when a level of a fluid reaches a first value in the metering vessel, and at least one second level meter disposed above the first level meter and configured to generate a signal when a level of a liquid in the metering vessel reaches a second value greater than the first value, wherein the first opening of the metering vessel is fluidically connectable to at least one first metering supply line. The housing has a through the housing wall continuous cleaning opening, which is fluidly connected to a second opening of the metering vessel, wherein a cross section of the cleaning opening and a cross section of the second opening of the metering vessel overlap at least partially.

By the cleaning opening passes through the housing wall and its cross section overlaps at least partially with the cross section of the second opening of the metering vessel, the interior of the metering vessel is accessible from the outside via the cleaning opening. This allows the interior of the dosing vessel with a cleaning tool, e.g. a brush or a pipe cleaner to clean. It is particularly advantageous that the metering vessel for this purpose does not need to be removed and that fluid lines that are connected in operation with the metering, do not have to be separated from the metering to perform a cleaning.

The cleaning opening and the second opening of the metering can be arranged cylindrically symmetrical and coaxial one behind the other. In this case, the cleaning opening and the dosing can each have a (imaginary) Zylindersymmetrieachse and be arranged so that the cylindrical axes of symmetry of the cleaning opening and the second opening of the dosing together. If the second opening of the metering vessel has a circular cross-section, the cylindrical axis of symmetry of the cleaning opening runs orthogonally to the circular cross-section and cuts it in its center of the circle.

The cleaning opening may have a diameter of approximately 5 to 10 mm extending perpendicular to a longitudinal axis, in particular a cylinder axis of symmetry, of the cleaning opening.

The metering unit may further comprise a third level meter disposed above the second level meter and configured to generate a signal when a level of a liquid in the metering vessel reaches a third value greater than the first and second values. This third level meter can serve as a safety level meter to generate a warning signal in case of unintended overdosage before overflowing the dosing.

In an advantageous embodiment, the metering vessel has a transparent wall, in particular made of glass or a transparent plastic, wherein the first level meter comprises a first light barrier arranged in the housing, which is set up to radiate a first light beam through the metering vessel, and the second level meter comprises a second light barrier arranged in the housing, which is set up to radiate a second light beam through the metering vessel.

If the dosing unit comprises a third level meter arranged above the second level meter and configured to generate a signal when a level of a liquid in the dosing vessel reaches a third value that is greater than the first and the second value, the third level meter may in this embodiment comprise a third arranged in the housing light barrier, which is adapted to emit a third light beam through the metering vessel. The first, second or third light beam may comprise light of at least one wavelength of the visible and / or infrared spectral range.

In the cleaning opening, a manually removable closure can be arranged which is designed to close the cleaning opening gas-tight. The closure may be a plug or plug, for example made of an elastic material or with a cut adapted to the cleaning opening.

• eine Dosiereinheit nach einer der voranstehend beschriebenen Ausgestaltungen;
• mindestens eine mit der ersten Öffnung der Dosiereinheit fluidisch verbundene erste Dosierzuleitung und eine Pumpe, die dazu eingerichtet ist, die Messflüssigkeit durch die erste Dosierzuleitung zur Dosiereinheit zu transportieren;
• mindestens einen mit der Dosiereinheit fluidisch verbundenen Vorratsbehälter, in dem ein Reagenz enthalten ist;
• mindestens eine den mindestens einen Vorratsbehälter mit der ersten Öffnung des Dosiergefäßes fluidisch verbindende zweite Dosierzuleitung;
• mindestens eine mit dem Dosiergefäß über dessen zweiten Öffnung kommunizierende zweite Pumpe; eine mit der Dosiereinheit fluidisch verbundene Messzelle;
• mindestens eine die erste Öffnung des Dosiergefäßes mit der Messzelle verbindende Fluidleitung; einen, insbesondere fotometrischen, Messaufnehmer, der dazu eingerichtet ist, einen mit dem Parameter der Flüssigkeitsprobe korrelierenden Messwert eines in der Messzelle aufgenommenen Reaktionsgemischs zu erfassen; und
• eine Steuerelektronik, die dazu ausgestaltet ist, Signale der Pegelmesser zu empfangen und zu verarbeiten und die erste Pumpe und die zweite Pumpe zu steuern, um eine Probe der Messflüssigkeit und eine vorgebbare Menge des Reagenz mittels der Dosiereinheit zu dosieren und aus der Probe und der vorgebbaren Menge des Reagenz das Reaktionsgemisch zu erzeugen,
• wobei die Steuerelektronik weiter dazu ausgestaltet ist, Signale des Messaufnehmers zu empfangen und zu verarbeiten, um aus den Signalen des Messaufnehmers die Werte des Parameters der Probe zu ermitteln.

The invention also includes an automatic analyzer for determining values of a parameter of a sample of a measuring liquid. This analyzer includes:

• a dosing unit according to one of the embodiments described above;
• at least one first metering feed line fluidically connected to the first opening of the metering unit, and a pump, which is set up to transport the measuring liquid through the first metering feed line to the metering unit;
• at least one supply container fluidically connected to the dosing unit, in which a reagent is contained;
• at least one second metering supply line fluidically connecting the at least one storage container to the first opening of the metering vessel;
• at least one second pump communicating with the dosing vessel via its second opening; a measuring cell fluidically connected to the metering unit;
• at least one fluid line connecting the first opening of the metering vessel with the measuring cell; a, in particular photometric, sensor which is adapted to detect a measured value correlated with the parameter of the liquid sample of a reaction mixture received in the measuring cell; and
• an electronic control unit which is designed to receive and process signals of the level meter and to control the first pump and the second pump in order to meter a sample of the measuring fluid and a predeterminable amount of the reagent by means of the metering unit and from the sample and the predeterminable one Amount of reagent to produce the reaction mixture
• wherein the control electronics are further configured to receive and process signals from the sensor to determine from the signals of the sensor the values of the parameter of the sample.

The control electronics can be set up to detect, based on a chronological progression of signals from the second and / or the third level meter, whether contamination of the metering vessel is present and to output an alarm signal upon detection of contamination of the metering vessel. Receives the control electronics, for example, at an unexpected time during the implementation of the dosage and / or analysis, a signal of the level meter, they can interpret this as a sign of contamination of the metering and issue a corresponding alarm signal.

• 1 eine schematische Darstellung eines automatischen Analysegeräts zur Bestimmung eines Summenparameters mit einer Dosiereinheit;
• 2 eine schematische Längsschnitt-Darstellung einer Dosiereinheit.

The invention will be explained in more detail below with reference to the exemplary embodiments illustrated in the figures. Show it:

• 1 a schematic representation of an automatic analyzer for determining a sum parameter with a metering unit;
• 2 a schematic longitudinal sectional view of a metering unit.

This in 1 schematically illustrated analyzer 1 is used to determine the chemical oxygen demand (COD or COD as an abbreviation of the English term "chemical oxygen demand") of a liquid sample one in a sampling point 2 present measuring liquid. Although the embodiment described below relates to an analyzer for determining the chemical oxygen demand, the invention is quite analogous to analyzers for determining other sum or individual parameters transferable.

The analyzer 1 has a container device 41 with a sample template 2 and liquid containers 5 . 6 . 7 . 8th . 9 . 21 , a measuring device 40 , and a conveying and metering device 39 for the measuring liquid and in the liquid containers 5 . 6 . 7 . 8th . 9 contained liquids. The measuring device 40 includes an optical sensor 31 and a measuring cell 20 , which serves in the present example at the same time as a digestion reactor for digestion of the liquid sample. The conveying and metering device 39 comprises a dosing unit with a housing 42 in which a dosing vessel 38 and photocells 23 . 24 are arranged. It also includes a variety of fluid lines and valves, as well as the pumps 3 and 16 for transporting liquids through the fluid lines.

To remove a fluid sample from the sampling point 2 serves a pump 3 , which can be configured for example as a hose, diaphragm or piston pump. The sampling point 2 is via a first dosing feed line 4 with the dosing vessel 38 connected.

The liquid container 5 . 6 . 7 . 8th and 9 contain reagents intended to be added to the fluid sample to form a reaction mixture. In the reaction mixture, a measured variable can be determined (eg a Absorption or absorbance of radiation of a particular wavelength), which is a measure of the chemical oxygen demand of the liquid sample. One or more of the liquid containers 5 . 6 . 7 . 8th and 9 can provide standard solutions for calibration and / or adjustment of the analyzer 1 contain. In the example shown here contains the first liquid container 5 as a decomposition agent for the contained in the measuring liquid, some present as solids, in the chemical oxygen demand incoming carbonaceous compounds a strong oxidizing agent, such as a potassium dichromate. The second liquid container 6 contains an aqueous solution of mercury sulfate for masking optionally contained in the measuring liquid chloride ions. The third liquid container 7 Contains sulfuric acid to acidify the reaction mixture. The fourth and fifth liquid container 8th . 9 each contain a standard solution with different, preset COD values, which are used to calibrate and / or adjust the analyzer 1 serve.

The liquid container 5 . 6 . 7 . 8th . 9 are over fluid lines 10 . 11 . 12 . 13 and 14 with one into the dosing vessel 38 opening second Dosierzuleitung 19 connected. The fluid lines 10 . 11 . 12 . 13 and 14 can each be blocked by a valve, with a central valve mechanism indicated only schematically here 15 used to actuate the valves.

The dosing vessel 38 is configured in the present example as a hollow cylinder made of a transparent material, such as glass, whose (imaginary) cylinder axis extends in the vertical direction. At its upper end, the hollow cylinder is through the upper housing part 17 , at its lower end by the lower housing part 22 Missed. The interior of the dosing vessel 38 communicates with a piston pump 16 , which by means of a not explicitly in the 1 shown linear motor is actuated. In the upper housing part 17 the metering unit is arranged a connecting line which the piston pump 16 with the dosing vessel 38 connects, so that by means of the piston pump 16 in the dosing vessel 38 optionally a negative or positive pressure for transporting liquid into the metering vessel 38 or from the metering vessel 38 can be generated out. In the case 42 are also several photocells 23 . 24 arranged to monitor the liquid level in the dosing 38 serve. In 1 are two light barriers 23 . 24 shown at different heights above that with the second metering line 19 connected lower opening of the metering vessel 38 are arranged. It is characterized by the distance of the light barriers 23 and 24 in the axial direction and the cross section of the metering vessel 38 defines a specific fluid volume. This volume can be used as a volume unit for dosing liquids by means of the dosing unit. In a modification of the in 1 illustrated embodiment, more than two light barriers can be used, for example, one above the light barrier 23 arranged further light barrier can be used to detect overflow or the risk of overflowing the dosing early. In addition, further light barriers can be provided to allow a more flexible volume metering.

In the upper housing part 17 is also one through the valve 42 closable pressure equalization port or pressure equalization line, which the metering vessel 38 optionally with the atmosphere 18 combines.

The housing 42 the dosing unit points in the upper housing part 17 In addition, a cleaning opening 44, which in the present example with the metering vessel 38 coaxial with respect to the cylinder axis of the metering vessel 38 is arranged. The cross sections of the cleaning opening 44 and the upper opening of the metering vessel 38 overlap each other. The cleaning opening 44 is through a stopper 45 fluid-tight lockable, so that when on the cleaning opening 44 attached stopper 45 a liquid transport from the metering vessel 38 or in the dosing vessel 38 by means of the piston pump 16 is possible. Will the stopper 45 from the cleaning opening 44 removed, is the inside of the dosing 38 over the cleaning opening 44 accessible from outside, leaving a cleaning tool, such as a brush or a pipe cleaner in the dosing 38 can be introduced to the inner wall of the dosing 38 mechanically or with mechanical support to clean.

A lower housing part 22 of the housing 42 The dosing unit connects via holes or lines in the housing part 22 the first metering line 4 and the second metering line 19 with the interior of the metering vessel 38 , By means of the hose pump 3 can take measuring fluid from the sampling point 2 over the first dosing line 4 into the dosing vessel 38 be transported. Is the peristaltic pump 3 not in operation, it acts as the first dosing feeder 4 locking valve. Liquids from the containers 5 . 6 . 7 . 8th and 9 can by means of the piston pump 16 via the second metering line 19 into the dosing vessel 38 be transported. A transport via the Dosierzuleitung 19 can through the central valve scarf 15 be released or blocked.

At least partially through the lower housing part 22 of the housing 42 the metering unit extending fluid line 28 by means of a valve 27 is either closable or can be opened, is the dosing 38 with the measuring cell 20 connected. This includes one from one transparent material, eg glass, formed decomposition vessel 25 that by a heater 26 is heated. In the decomposition vessel 25 also opens one through a second valve 29 Lockable pressure compensation line 30 , by means of which the decomposition vessel 25 with the atmosphere 18 is connectable. The decomposition vessel 25 is designed as an upright hollow cylinder, in the lower region of the fluid line 28 empties. At least partially through the lower housing part 22 of the housing 42 the dosing unit running through a valve 37 lockable derivative 43 are the measuring cell 20 and the dosing vessel 38 with a waste container 21 connected, such that spent liquid from the digestion container 25 via the dosing vessel into the waste container 21 can be transported, and / or that in the dosing 38 from the sampling point 2 or one of the liquid containers 5 . 6 . 7 . 8th . 9 transported liquid directly into the waste container 21 can be directed.

The analyzer 1 comprises a photometric sensor for determining a measured value representing the chemical oxygen demand of the liquid sample 31 that is a light source 32 and a light receiver 33 having. The light source 32 For example, it can comprise one or more LEDs, in particular light emitting different wavelengths, or one or more multicolor LEDs. The light receiver 33 may have one or more photodiodes. From the light source 32 emitted measuring light radiates through the decomposition vessel 25 along a through the in the decomposition vessel 25 contained reaction mixture extending measuring path and meets the light receiver 33 ,

The photometric sensor 31 generates one of the intensity of the light receiver 33 incident light intensity dependent electrical measurement signal, which optionally amplifies a sensor circuit not shown in detail and / or digitized. The on the light receiver 33 incident light intensity depends on the absorbance or absorption of the decomposition vessel 25 contained reaction mixture. The light source 32 In the present example, it is designed in such a way that it emits light of at least one wavelength as measurement light whose absorption or extinction is a measure of the consumption of the oxidizing agent for the digestion of oxidisable constituents of the sample, in the present example potassium dichromate. So that's from the photometric sensor 31 generated electrical measurement signal is a measure of the chemical oxygen demand of the liquid sample.

The analyzer 1 has an electronic control unit for automated measurements and the determination of measured values 34 on. This comprises an electronic data processing device which has one or more processors and one or more data and program memories. The control electronics 34 stands with the photometric sensor 31 in connection and receives from this the, if necessary digitized and amplified, measuring signal. In a memory of the control electronics 34 stored is a computer program executable by the one or more processors, which is for determining the chemical oxygen demand based on the measurement signal of the photometric sensor 31 serves. In particular, this program can include a calculation rule (calibration function) which assigns values of the measured value, here the chemical oxygen demand of the sample, to the values of the measurement signal. The calibration function can be determined and / or adjusted by means of one or more calibration measurements with standard solutions which have a known COD value.

The control electronics 34 is also with the pumps 3 . 16 , and the valves 15 . 22 . 37 . 27 . 29 . 42 as well as the central valve mechanism 15 connected to a transport of predetermined amounts of liquid from the sampling point 2 and the liquid containers 5 . 6 . 7 . 8th . 9 into the decomposition vessel 25 to control a determination of the chemical oxygen demand. The control electronics 34 is also with the photocells 23 . 24 connected to based on the signals of the photoelectric sensors 23 . 24 the transport of liquid into and out of the dosing vessel 38 to be controlled such that predeterminable volumes as multiples of the distance of the light barriers 23 . 24 measured from each other and into the measuring cell 20 be dosed. Similarly, the control electronics 34 control the performance of calibration measurements by using the pumps and valves instead of the sampling point 2 one or both standard liquid containers 8th . 9 takes a given amount of a standard solution as a liquid sample. The control electronics 34 may be configured to adjust the calibration device based on such a calibration measurement 1 make. In addition, the control electronics 34 with the heater 26 be connected to the heating of one in the decomposition vessel 25 control the reaction mixture contained.

The control electronics 34 comprises display means, eg a display, on which a menu structure and / or parameter values and / or measured values can be displayed and current messages can be output. The control electronics 34 may also include input means, such as a keyboard and / or one or more switches and / or a touch panel / touch screen, via which a user can enter control commands or parameters and optionally switch between different views in a menu structure.

The analyzer 1 can a housing (not in 1 shown), the control electronics 34, the Aufschlusseinheit 40 , the conveyor and dosing unit 39 and the liquid containers 41 contains. This housing may be designed as a cabinet having one or more doors, thus allowing access to the components of the analyzer, for example for maintenance purposes.

The procedure for the photometric determination of the chemical oxygen demand of a sample of the measuring liquid with the in 1 The device shown, for example, as described below. All the process steps described here are controlled by the control electronics 34 carried out.

First, by means of the peristaltic pump 3 Measuring fluid from the sampling point 2 over the first metering line 4 into the dosing vessel 38 transported. The corresponding to the liquid containers 5 . 6 . 7 . 8th . 9 . 21 and the measuring cell 20 leading fluid lines 10 . 11 . 12 . 13 . 14 through valves in the central valve mechanism 15 blocked. The valve 42 is set so that the dosing 38 via the pressure equalization opening with the atmosphere 18 connected is. Reaches the level in the dosing vessel 38 the upper photocell 23 , the transport of liquid is in the dosing 38 completed. By means of the piston pump 16 It is also possible to carry out a fine dosing of the measuring liquid, in which case the valve is 42 closed. Subsequently, by means of the piston pump 16 when the valve is closed 42 and open valve 28 in the dosing vessel 38 volume of the measuring liquid as liquid sample into the digestion vessel 2 transported. In further steps can be controlled via the central valve mechanism 15 from the liquid containers 5 . 6 and 7 over the wires 10 . 11 . 12 and the second dosing line 19 corresponding by the control electronics 34 predetermined volumes are metered by means of the metering unit and the same way previously described for the liquid sample in the digestion vessel 25 be transported.

The fluid sample and the reagents form in the digestion vessel 25 a reaction mixture. By closing the valves 29 and 27 in the pressure equalization line 30 and the supply line 28 for liquids from the dosing unit to the digestion vessel 25 , the decomposition vessel becomes 25 sealed fluid-tight. Subsequently, the heater 26 put into operation and that in the decomposition vessel 25 present liquid mixture heated to a temperature of about 175 ° C at a pressure of 5 to 10 bar. With the beginning of the heating process is by means of the photometric sensor 31 quasi-continuously determined the extinction and / or absorption of the reaction mixture. The detected measurement signals are by means of the control electronics 34 evaluated. Once a specified state of absorbance or absorption is achieved, the absorbance or absorbance measurement is terminated. The fixed state can be a value of minimum temporal change of absorbance or absorption (stability criterion). The measurement signal obtained when the specified state is reached is used to determine a measurement of the chemical oxygen demand of the sample. This is done by means of the assignment of a value of the chemical oxygen demand to the measuring signal on the basis of a control electronics 34 stored calibration function.

After the end of the measurement, the spent reaction mixture is removed from the digestion tank 25 over the fluid line 28 and the dosing unit by means of the piston pump 16 in the waste container 21 transported.

Calibration measurements can be carried out between the individual measuring cycles, which are carried out quite analogously to a measuring cycle, but instead of a liquid sample taken from the sampling point, a predetermined quantity of one of the liquid containers 8th or 9 taken standard liquid into the measuring cell 20 or digestion vessel 25 and mixed with the reagents to form the reaction mixture. The readings taken during the calibration measurements can be used to adjust the analyzer 1 be used.

In 2 is the case 42 the dosing unit of in 1 presented analyzer 1 shown schematically in a longitudinal section. The housing 42 has a structure formed from one or more housing parts made of plastic. It encloses a cavity in which an upright, cylindrical dosing of a transparent material, eg glass, can be used. The metering vessel is in the example shown here through a glass tube 57 formed in 2 is shown in dashed lines. The upper opening of the glass tube 57 is through the upper housing part 17 and its lower opening through the housing part 22 locked. Through the housing extending lines (in the longitudinal section illustration of 2 not visible) connect the connections 51 . 52 , 53 and 54 with the inside of the dosing vessel. In the upper housing part 17 is the fluidically connectable with the dosing via one of these lines connection 51 arranged on the one opposite the metering vessel closable pressure equalization line can be connected. In the upper housing part 17 is also one with the dosing via a inside of the housing part 17 extending line connected connection 52 arranged, which provided is, fluidically with the piston pump 16 of the analyzer 1 to be connected.

In the lower housing part 22 is a connection 53 arranged, via one in the housing part 22 extending line is connected to the metering vessel, and which is further provided to the first metering line 4 connected to the dosing with the sampling point 2 combines. Another connection 53 is in the lower housing part 22 provided, via a through the housing part 22 extending line is fluidly connected to the metering vessel and for connecting one to the measuring cell 20 leading fluid line is determined. Through the lower housing part 22 also runs the second metering line 19 passing through the central valve mechanism 15 with the liquid containers 5 . 6 . 7 . 8th . 9 is connectable, and which opens into the dosing.

In the case 42 are three light barriers 23 . 24 and 55 arranged. The first two photocells 23 and 24 serve, as described above, the dimension of a through the arrangement of the light barriers 23 . 24 relative to each other or relative to the mouth of the first and second Dosierzuleitung in the metering certain fluid volume. The third, uppermost photocell 55 serves as a safety light barrier, by means of which an imminent overflow or overdose of the metering vessel can be detected at an early stage. If this photocell triggers, it sends a signal to the control electronics. In this case, the control electronics generates an error message and outputs it via the display device.

In the upper housing part 17 of the housing 42 is a passage opening, for example in the form of a bore, provided with a diameter of about 5 mm, which opens into the dosing. As already related to 1 described, this opening serves as a cleaning opening 44 which allows access for a cleaning tool for cleaning the dosing.

During operation of the analyzer, as described in the introduction, it may happen that impurities present in the measuring liquid remain adhered to the wall of the metering vessel. Components of reagents removed from the liquid containers may also precipitate or crystallize out in the dosing vessel and adhere to the vessel wall. If the measuring liquid or reagents are transported into the dosing vessel by means of a pressure gradient between the dosing vessel and the liquid containers or the sampling point, droplets of the respective liquids can be sprayed into the upper area of the dosing vessel, in particular the area of the second and the third light barrier 23 . 55 reach. If impurities accumulate in these areas, it can cause the second or third light barrier to trip or to trip continuously 23 . 55 come. In this case, a mechanically assisted cleaning of the dosing is desirable. About the cleaning opening 44 is this possible.

The control unit 34 of the analyzer 1 In addition, it can be designed to trigger a false trip or permanent triggering of the light barriers 23 . 55 register and issue a diagnostic or alarm message when registering such a malfunction. For this purpose, the control unit 34 Monitor the course and / or the frequency of the trigger signals over time and compare with an expected course. The expected course results from that of the control unit 34 executed control program for performing analysis cycles and / or calibration measurements of the analyzer 1 , If one of the light barriers triggers at a time when no dosing takes place in the dosing unit, this is detected as a deviation from the expected course and a corresponding error message is triggered. For a user, the error message is an indication that a cleaning of the dosing unit is required.

As already stated, the dosing unit according to the invention is not limited to use in an analyzer for determining the chemical oxygen demand. Rather, it can also be used to advantage in other analyzers, e.g. in analyzers for the determination of total phosphorus, total nitrogen, ammonium concentration or ammonium nitrogen, nitrate concentration, orthophosphate, or total hardness. To determine these parameters, other reagents may be necessary, and may not require digestion of the reaction mixture under heating. However, the dosage of the liquid sample, reagents and standard liquids used can be carried out according to the same principle as described in the present embodiment. Occurring impurities in the dosing can be advantageously removed by access via a cleaning port.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10222822 A1 [0004]
• DE 10227032 A1 [0004]
• DE 102009029305 A1 [0004]
• DE 102013114138 A1 [0005, 0006]

Claims (9)

A dosing unit for an automatic analyzer (1) for determining a parameter of a fluid sample, comprising: a housing (42), a dosing vessel (38) disposed in the housing (42) having a first opening communicating with at least a first dosing conduit (4 ) is fluidically connectable, disposed above the first opening first level meter (24) which is adapted to generate a signal when a level of a liquid in the metering vessel (38) reaches a first value, and at least one above the first level meter (24) arranged second level meter (23) which is adapted to generate a signal when a level of a liquid in the metering vessel (38) reaches a second value which is greater than the first value, characterized in that the housing (42) has a through a wall of the housing (42) passing through the cleaning opening (44) having a second opening of the metering s (38) is fluidically connected, wherein a cross section of the cleaning opening (44) and a cross section of the second opening of the metering vessel (38) at least partially overlap with each other. Dosing unit after Claim 1 , wherein the cleaning opening (44) and the second opening of the metering vessel (38) are arranged cylindrically symmetrical and coaxially one behind the other. Dosing unit after Claim 1 or 2 , wherein the cleaning opening (44) has a perpendicular to a longitudinal axis, in particular cylinder axis of symmetry, the cleaning opening (44) extending diameter of at least 3 mm, in particular from 5 to 10 mm. Dosing unit according to one of Claims 1 to 3 further comprising a third level meter (55) disposed above the second level meter (23) and configured to generate a signal when a level of a liquid in the metering vessel (38) reaches a third value greater than the first one and the second value. Dosing unit according to one of Claims 1 to 4 wherein the metering vessel (38) has a transparent wall, in particular made of glass or a transparent plastic, and wherein the first level meter (24) comprises a first light barrier arranged in the housing (42), which is adapted to pass through a first light beam the metering vessel (38) to radiate, and wherein the second level meter (23) comprises a second in the housing (42) arranged light barrier, which is adapted to radiate a second light beam through the metering vessel (38). Dosing unit after Claim 5 further comprising a third level meter (55) disposed above the second level meter (23) and configured to generate a signal when a level of a liquid in the metering vessel (38) reaches a third value greater than the first one and the second value, and wherein the third level meter (55) includes a third light barrier disposed in the housing (42) configured to radiate a third light beam through the metering vessel. Dosing unit according to one of Claims 1 to 6 , further comprising a manually removable closure arranged in the cleaning opening (44) and configured to seal the cleaning opening (44) in a gas-tight manner. An automatic analyzer (1) for determining values of a parameter of a sample of a measuring fluid, comprising: - a dosing unit according to any one of Claims 1 to 7 at least one first metering feed line (4) fluidically connected to the first opening of the metering unit and a pump (3) arranged to transport the measuring liquid through the first metering feed line (4) to the metering unit; - At least one fluidically connected to the metering reservoir (5, 6, 7), in which a reagent is contained; - At least one at least one reservoir (5, 6, 7) with the first opening of the metering vessel (38) fluidly connecting the second metering supply line (19); - At least one communicating with the metering vessel (38) via the second opening of the second pump (16); - A measuring cell (20) fluidly connected to the dosing unit; - At least one of the first opening of the metering vessel (38) with the measuring cell (20) connecting the fluid line; a sensor, in particular a photometric sensor, which is set up to detect a measured value correlated with the parameter of the liquid sample of a reaction mixture recorded in the measuring cell (20), and control electronics (34) which are configured to generate signals of the level meter ( 23, 24, 55) and to control the first pump (3) and the second pump (16) in order to dose a sample of the measuring liquid and a predeterminable amount of the reagent by means of the dosing unit and from the sample and the predeterminable amount of the reagent to generate the reaction mixture, wherein the control electronics (34) is further configured to Receive and process signals from the sensor (31) to determine from the signals of the sensor (31) the values of the parameter of the sample. Analyzer (1) after Claim 8 , wherein the control electronics (34) is adapted to detect on the basis of a time course of signals of the second and / or the third level meter (23, 55), whether contamination of the metering vessel (38) is present, and upon detection of contamination of the metering vessel (38) to issue an alarm signal.

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