METHOD FOR DOSING AN AMOUNT OF LIQUID WITH A PERISTALTIC PUMP

Abstract

The present disclosure conveys a method for dosing an amount of liquid with a peristaltic pump in an analyzer, wherein the analyzer is configured to determine a concentration of a measurand of a sample, wherein the peristaltic pump includes at least one rotor having at least two rollers, the method comprising the steps: determining the position of at least one roller of the peristaltic pump; moving the rotor of the peristaltic pump to an initial position if it is not already in an initial position; and dosing the amount of liquid to be conveyed by moving the rotor by counting roller passes through a reference position. The present disclosure further discloses an analyzer for implementing the method.

Claims

1. A method for dosing an amount of liquid with a peristaltic pump in an analyzer configured to determine a concentration of a measurand of a sample, the method comprising: providing a peristaltic pump that includes a tube and at least one rotor including at least two rollers, which are configured to contact and deform the tube, the tube having an inlet side and an outlet side; determining a position of at least one of the at least two rollers of the peristaltic pump; moving the at least one roller into an initial position when the at least one roller is not yet in an initial position; and dosing a desired amount of liquid by moving the at least one roller by counting roller passes through a reference position.

2. The method of claim 1, further comprising discarding contents of the tube of the peristaltic pump disposed in a region of the tube that is on the outlet side before the initial position is reached.

3. An analyzer for determining a concentration of a measurand of a liquid sample, the analyzer comprising: a peristaltic pump that includes a tube and at least one rotor including at least two rollers, which are configured to contact and deform the tube, the tube having an inlet side and an outlet side; and a data processing unit configured to perform the method according to claim 1.

4. The analyzer of claim 3, further comprising a counting unit configured and arranged to count roller passes through the reference position.

5. The analyzer of claim 4, wherein the counting unit comprises a switch that is activated when the at least one roller passes through the reference position.

6. The analyzer of claim 4, wherein the at least one roller comprises a magnet, and the counting unit comprises a magnetic sensor.

7. The analyzer of claim 6, wherein the magnetic sensor is a reed contact sensor or a Hall effect sensor.

8. The analyzer of claim 4, wherein the counting unit comprises a light barrier.

9. A computer program comprising instructions which cause the analyzer to perform the method of claim 1.

10. A computer program product comprising a non-transitory machine-readable storage medium encoding instructions that, when executed by one or more programmable processors, cause the one or more programmable processors to perform the method of claim 1, wherein the data processing unit includes the one or more programmable processors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] This is explained in more detail with reference to the following figures:

[0027] FIG. 1 shows a claimed automatic analyzer in a symbolic overview;

[0028] FIG. 2 shows the system design of the claimed analyzer;

[0029] FIGS. 3a and 3b show two positions of rollers of a peristaltic pump;

[0030] FIGS. 4a and 4b show an embodiment of the peristaltic pump in a first and a second position; and

[0031] FIGS. 5a and 5b show an embodiment of the peristaltic pump in a first and a second position.

[0032] In the figures, the same features are identified by the same reference signs.

DETAILED DESCRIPTION

[0033] The entirety of the claimed automatic analyzer is denoted by reference sign 1 and is shown in FIG. 1.

[0034] To be measured is, for example, the direct absorption of a substance or the intensity of a color, which is generated by converting the substance to be determined into a color complex by means of reagents. Further possible measurands that function according to a similar principle are turbidity, fluorescence, etc. An application example is the measurement of the chemical oxygen demand (COD), wherein COD is a sum parameter, which means that the measured value results from the sum total of the substances and cannot be attributed to a single substance. In this measurement method, a change of color is generated in a reactor; see below. Other possible parameters are, for example, total carbon, total nitrogen, or an ion concentration, such as the concentration of the ions of ammonium, phosphate, nitrate, etc.

[0035] A sample 13 is taken from the medium 15 to be analyzed, for example, a liquid or a gas. Usually, taking the sample 13 happens fully automatically by means of the analyzer itself, by subsystems 14, such as pumps, tubes, valves, etc., for example. For determining the substance content of a certain species, one or more reagents 16 that were developed specifically for the respective substance content and that are available in the housing of the analyzer are mixed with the sample 13 to be measured. This is shown in a symbolic manner in FIG. 1. In practice, various vessels are provided with different reagents, which are extracted by means of the aforementioned pumps, tubes, and valves, etc. and mixed as necessary. This is illustrated in FIG. 2. Separate pumps, tubes, and valves can also be used for each process (taking the sample, mixing of reagents, etc.).

[0036] A color reaction of the mixture caused in this way is subsequently measured by means of an appropriate measuring device, such as a photometer 17. For this purpose, the sample 13 and the reagents 16 are, for example, mixed in a measuring chamber 8 and optically measured with light of at least one wavelength using the transmitted light method. In the method, light is transmitted through the sample 13 by a sender 17.1. A receiver 17.2 for receiving the transmitted light is assigned to the sender 17.1, wherein an optical measuring path 17.3 (indicated by a dotted line in FIG. 1) runs from the sender 17.1 to the receiver 17.2. The sender 17.1 comprises, for example, one or more LEDs, i.e., one LED per wavelength, or an appropriate light source with broadband excitation. Alternatively, a broadband light source with a corresponding filter placed in front of it is used, which filter can also, depending on the application, be mounted directly in front of the receiver. The receiver 17.2 can, for example, comprise one or more photodiodes.

[0037] The measured value is generated by the receiver based on the light absorption and a stored calibration function. The analyzer 9 comprises a transmitter 10 with a microcontroller 11 along with a memory 12. The analyzer 9 can be connected to a field bus via the transmitter 10. Furthermore, the analyzer 9 is controlled via the transmitter 10. Thus, the taking of a sample 13 from the medium 15, for example, is initiated by the microcontroller 11 by means of appropriate control commands to the subsystems 14. The measurement by the photometer 17 is also controlled and regulated by the microcontroller. The dosing of the sample 13 can also be controlled by the transmitter 10. A computer program for controlling the analyzer, for example for dosing, then runs on the transmitter 10. A computer-readable medium is also located on or can be plugged into the transmitter 10.

[0038] The taking of the sample 13 is now described in principle. For taking the sample 13 from the medium 15, a sample taking apparatus is used that can, for example, comprise a pump 4, here a peristaltic pump. The sample 13 passes into a dosing apparatus 1 via a medium line. As mentioned, the analyzer 9 comprises liquid containers that contain reagents 16 to be added to the sample 13 for determining the measurand of the analyzer 9 and standard solutions for calibrating and/or adjusting the analyzer 9. The peristaltic pump 4 pumps the sample 13 into the dosing apparatus 1.

[0039] The dosing apparatus 1 comprises a dosing chamber 2, which is, for example, designed as a cuvette, and at least one dosing light barrier 3. FIG. 2 shows three light barriers 3, wherein two of them serve as measuring light barriers for measuring a certain amount of liquid, and the top one serves as safety light barrier. If the liquid to be measured in the dosing chamber 2 reaches the top light barrier, an alarm is triggered, and the dosing is stopped. The light barriers 3 can also be designed as infrared light barriers with daylight filters. A valve 21 for ventilation is also connected to the dosing apparatus 1. A pump 5, more precisely a displacement pump, more precisely a piston pump, is also connected to the dosing apparatus 1. The piston pump 5 pumps the liquid from the dosing chamber 2 into the reactor 8. This happens because air is drawn in during the drawing up of the piston pump 5, and this air column pushes before it the liquid from the dosing chamber 2 toward the reactor 8.

[0040] The dosing apparatus 1 is connected by means of a line 6 to the measuring chamber 8, also called reactor 8. The line 6 is designed as a tube or pipe.

[0041] The reactor 8 comprises a valve 19 on the side of the line 6 and a valve 20 for venting on the opposite side.

[0042] The reagents 16, or the containers containing the reagents 16, are connected to the dosing apparatus 1 via liquid lines. There are appropriate valves 22 for switching the line. There is furthermore an outlet 18, which comprises a valve where applicable and serves as drain.

[0043] FIGS. 3a and 3b show a peristaltic pump 4 of the analyzer 9. Said pump comprises, in the example, three rollers 23, 24, 25 on a rotor 26. To solve the disadvantages of a peristaltic pump described above, detection of at least one of the rollers 23, 24, 25 in the interior of the peristaltic pump 4 is disclosed.

[0044] In general, a peristaltic pump is a displacement pump in which the amount of liquid to be conveyed is forced through a tube 27 by external mechanical deformation of said tube. An amount of liquid to be dosed flows in through the inlet 32 and out through the outlet 33. In each case, the tube 27 is supported on the outside of the housing of the pump head and is clamped from the inside by rollers or shoes which rotate on a rotor 26. Here, the movement causes the clamping point to move along the tube 27 and to thereby push forward the liquid amount to be conveyed.

[0045] FIG. 3a shows a first position of the rotor 26, FIG. 3b a second position. First, the position of at least one roller 23, 24, 25 is determined in FIG. 3a. In principle, the position could also be detected directly at the rotor. Here, however, a counting unit 29 (see details below; the counting unit is symbolically represented as a rectangle in FIGS. 3a and 3b) is used to detect where whether a roller 23, 24, 25 is located at the counting unit.

[0046] If it is recognized that the rotor 26 is already in the initial position, dosing can begin immediately (see below). If the rotor 26 is not in the initial position (as is the case in FIG. 3a), it is first moved into the initial position. FIG. 3b, for example, shows this initial position, in which a roller, here the roller 24, is oriented vertically downward.

[0047] If the position at the beginning of a dosing step is known, that is to say, because of which the initial position, a software algorithm stored in the transmitter 10 can be used to configure the required revolutions such that the same number of pulses, i.e., roller passes through the counting unit 29, always occurs for a certain amount of liquid. This ensures that the dosed volume is always approximately constant. For this method of compensating to be applicable to every tube type and every degree of tube wear, the transported volume is measured at regular intervals during a dosing step and the peristaltic pump is thus calibrated.

[0048] If it is determined that the rotor 26 is not in the initial position, the amount of liquid located in the section closer to the output 33 is discarded. In FIG. 3a, this is the part of the tube 27 after the roller 25 in the direction 33. In one embodiment, there lastly follows a flush with air or nitrogen, more generally with a flushing medium, so that it is ensured that the tube 27 is empty or free of undesired media.

[0049] The unit which determines the position of the rollers at the beginning does not necessarily have to be the unit which counts the roller passes. However, this is preferably configured as a single unit, the counting unit 29.

[0050] FIGS. 4a and 4b show an embodiment of the detection of the initial position and/or the counting of the roller passes. FIG. 4a shows a first position; FIG. 4b shows the initial position. In this and in the next example, the peristaltic pump 4 has four rollers 23, 24, 25, 28. In this embodiment, detection takes place by means of a switch 30. A roller 23, 24, 25, 28 of the peristaltic pump 4 closes a switching mechanism when it passes the switch 30. This produces an electrical connection which generates the signal for the transmitter 10. In this way, the position of the rollers can be processed.

[0051] In one embodiment, detection takes place by means of magnetic switches. Here, the reference position of the rollers is detected via a magnetic contact. A magnetic switch which is fixed in place outside the rotor 26 is actuated at each revolution by means of a magnet located on the rotor 26 of the peristaltic pump 4. The switch is configured as, for example, a magnetic sensor, e.g., a reed contact or as a Hall effect sensor. This produces an electrical signal which can be processed by the software and the corresponding algorithm.

[0052] In the embodiment in FIGS. 5a and 5b, detection takes place by means of a light barrier 31. FIG. 5a shows a first position; FIG. 5b shows the initial position. For detection by means of light barrier 31, a sender and a receiver are placed at the initial position to be determined. The light emitted by the sender is interrupted at the moment when a roller 23, 24, 25, 28 of the peristaltic pump 4 passes the light barrier 31 and can thus no longer be detected by the receiver sensor. The position of the roller 23, 24, 25, 28 is then considered to be detected.

[0053] This results in a methodology for increasing the dosing accuracy of a peristaltic pump 4 by detecting the initial position of the rollers 23, 24, 25, 28 in the interior of the peristaltic pump 4. If the position of the rollers before the beginning of a dosing step is known (initial position), the number of occurring pulses can be predicted and accordingly taken into account when calculating the volume for dosing. This detection can be done, for example, by means of a switch, magnetic switch, or light barrier.