Method and device for monitoring a magnetic stirrer

Abstract

The invention relates to a monitoring method for monitoring a magnetic stirrer (200) of an electromagnetic stirring device (100) comprising a sensor device (110) having at least one magnetic field sensor (112) with a detection direction (ER) for detecting magnetic field lines (M) and a blind direction (BR) different from the detection direction (ER) without detecting magnetic field lines (M), which blind direction is oriented along magnetic field lines (M) of a drive magnetic field (AM) of the stirring device (100), said method comprising the following steps: - monitoring the magnetic field lines (M) along the detection direction (ER) of the magnetic field sensor (112), - comparing at least one magnetic field parameter (MP) of the monitored magnetic field lines (M) with a comparison value (VW), and - generating a monitoring result on the basis of the comparison.

Description

[0001] Method and apparatus for monitoring a magnetic stirrer

[0002] Description

[0003] The present invention relates to a monitoring method for monitoring a magnetic stirrer and a monitoring device for monitoring a magnetic stirrer.

[0004] It is known that magnetic stirrers are used to ensure continuous stirring of a liquid in biological or pharmaceutical experiments. A magnetic stirrer typically consists of a magnetized or magnetizable stirring rod placed inside a stirring vessel, such as a glass flask. To rotate this magnetic stirrer within the liquid in the vessel, a stirring device is positioned below the vessel. This stirring device usually has a platform on which the vessel can be placed. Below this platform are multiple electromagnetic coils capable of generating a rotating magnetic field, thus causing the magnetic stirrer to rotate with the magnetic field.

[0005] A disadvantage of existing solutions is the complexity of monitoring the magnetic stirrer. Especially during time-consuming experiments lasting several hours, days, or even weeks, it is crucial to ensure the magnetic stirrer is actually performing its stirring function. Potential sources of error arise if, for example, the stirrer becomes stuck due to a blockage. Similarly, if the magnetic stirrer is deflected from the drive magnetic field, it ceases to function. Known solutions employ monitoring devices that use camera systems to optically monitor the magnetic stirrer's position and / or rotation. However, this approach is structurally complex, as a separate camera system is required for each individual magnetic stirrer.Furthermore, such optical monitoring methods are prone to errors because they require a very complex and costly image analysis process. Last but not least, the compactness of the overall system is significantly reduced in this way, since the arrangement of the camera devices above the stirring vessels makes access to them difficult or even completely impossible. The object of the present invention is to provide a monitoring method for a magnetic stirrer in an electromagnetic stirring device that at least partially overcomes the disadvantages described above. In particular, the object of the present invention is to ensure cost-effective and simple monitoring of a magnetic stirrer in an electromagnetic stirring device.

[0006] The foregoing problem is solved by a monitoring method with the features of claim 1 and a monitoring device with the features of claim 13. Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings. Features and details described in connection with the monitoring method according to the invention naturally also apply in connection with the monitoring device according to the invention, and vice versa, so that the disclosure of the individual aspects of the invention always makes, or can make, reciprocal references.

[0007] According to the invention, a monitoring method serves to monitor a magnetic stirrer on an electromagnetic stirring device. For carrying out the monitoring method, the electromagnetic stirring device is equipped with a sensor device comprising at least one magnetic field sensor. Such a magnetic field sensor has a detection direction for detecting magnetic field lines and a blind direction, different from the detection direction, without detection of magnetic field lines. The blind direction is aligned along the magnetic field lines of a drive magnetic field of the stirring device. A monitoring method according to the invention now comprises the following steps:

[0008] - Monitoring of the magnetic field lines along the detection direction of the magnetic field sensor,

[0009] - Compare at least one magnetic field parameter of the monitored magnetic field lines with a reference value,

[0010] - Generating a monitoring result based on the comparison.

[0011] In the context of the present invention, the detection of magnetic field lines is understood to mean the fundamental detection of a magnetic field in the direction of detection. A magnetic field cannot be detected in the blind direction. Therefore, the detection of magnetic field lines, as defined in the present invention, is achieved primarily through the fundamental detection of a magnetic field.

[0012] According to the invention, optical monitoring methods can now be dispensed with, since a magnetic monitoring method is provided. This is based on the use of an arrangement of a magnetic field sensor according to the invention. This magnetic field sensor is equipped with two different essential directions. The first is the detection direction, in which the detection of magnetic field lines is possible. The detection of magnetic field lines refers in particular to the detection and / or evaluation of at least one magnetic field parameter of these magnetic field lines. In the blind direction, which differs from the detection direction and is in particular oriented perpendicular or substantially perpendicular to the detection direction, such detection of the magnetic field lines cannot be carried out.In other words, the magnetic field sensor is blind to magnetic field lines along the blind direction and cannot detect or evaluate any magnetic field parameters of these magnetic field lines in this blind direction.

[0013] When a drive magnetic field is applied to an electromagnetic stirrer, this field extends along magnetic field lines that are aligned in the blind direction and therefore not detectable by the magnetic field sensor. In a monitoring method according to the invention, this results in the respective magnetic field parameter being below or outside the corresponding reference value, so that in the simplest case the monitoring result indicates that no magnetic stirrer is present.

[0014] When a magnetic stirrer is placed on the stirring device, its magnetization will bend the drive magnetic field. This creates a combination of the permanent magnetic field of the magnetic stirrer and the drive magnetic field. This combination can also be referred to as a combined magnetic field. In other words, placing the magnetic stirrer causes a realignment of the now-bent magnetic field lines, which are no longer exclusively aligned along the blind direction of the magnetic field sensor. Rather, the magnetic field lines of this combined magnetic field are now at least partially aligned along the detection direction as well. Therefore, when carrying out a monitoring method according to the invention, a magnetic field parameter can not only be detected, but also, when compared with a corresponding reference value, provide feedback as a monitoring result that a magnetic stirrer is present.In particular, the detected magnetic field lines are evaluated in the form of magnetic field parameters, such as the shape and / or frequency of the changes in the magnetic field lines. The stirrer is then preferably driven only when a changing detection signal is present.

[0015] As is evident from the preceding explanation of a simple functional possibility of a monitoring method according to the invention, the presence of the magnetic stirrer can now be monitored qualitatively, for example. However, the monitoring method is unable to distinguish whether the drive magnetic field is present or absent, since the absence of any magnetic field lines and the presence of magnetic field lines exclusively along the blind direction cannot be distinguished from one another according to the invention's definition.

[0016] Using a monitoring method according to the invention, it is now possible to detect the presence of the magnetic stirrer by identifying and, in particular, evaluating the diffracted drive magnetic field, and especially to monitor it qualitatively. Besides such a qualitative evaluation of mere presence, other qualitative or even quantitative evaluations within the meaning of the present invention are of course conceivable. For example, the qualitative or quantitative magnetic field strength, the direction of the magnetic field lines, or a frequency of change of the direction or the magnetic field lines can be used as magnetic field parameters. The monitoring result can be used in a variety of ways. For example, simply displaying or documenting the monitoring result is conceivable.Of course, the monitoring result can also be incorporated into a control procedure, for example, to control the drive magnetic field accordingly, particularly in a controlling and / or regulating manner. The monitoring method according to the invention aims not only to detect a fault, but also, and especially, to monitor or even additionally document the proper functioning of the stirring mechanism. Optimization based on this monitoring result, for example of the stirring performance, is also possible within the scope of the present invention. It can be advantageous if, in a monitoring method according to the invention, the comparative value has at least one limit value for a qualitative distinction between falling below and exceeding a limit value. Using such a limit value is a particularly simple way to perform qualitative monitoring.In the simplest case, the limit value is, for example, a minimum value for the magnetic field strength. If only the drive magnetic field is present, the corresponding magnetic field parameter, representing a stronger magnetic field, is correspondingly low due to the orientation of the magnetic field sensor's reactive direction. As soon as the magnetic stirrer is placed within the drive magnetic field, the magnetic field parameter exceeds the reference value, thus indicating that diffraction of the drive magnetic field is occurring and present. The specific limit value used is unique to each magnetic field parameter. Therefore, specific reference values ​​can be used within the scope of the present invention for frequencies, amplitudes, gradients, phase shifts, or fundamental quantitative values ​​of the magnetic field parameters.

[0017] Further advantages can be achieved if, in a monitoring method according to the invention, the reference value contains quantitative information for at least one magnetic field parameter. This makes it possible, for example, to provide a large number of parameter data in the form of a list or a characteristic map, which then provide corresponding quantitative information by comparison with the determined magnetic field parameter. For example, a difference from a limit value, as well as a correlation between determined magnetic field parameters and corresponding reference values, is conceivable. Such a quantitative information list can also include additional information that already contains a partial step of the evaluation of the comparison step.In particular, for example, monitoring frequencies, gradients or amplitudes can provide feedback on the monitoring of the following, which will be explained later, such as the following: monitoring of the following: the following: the following: the following: the following: the following: the following: monitoring of frequencies, gradients or amplitudes, the following: the following: the following: monitoring of the following: ...

[0018] It can also be advantageous if at least one of the following magnetic field parameters is used in a monitoring method according to the invention:

[0019] - Magnetic field strength

[0020] - Magnetic field direction - Gradient of magnetic field strength

[0021] - Gradient of the magnetic field direction

[0022] - Frequency of the magnetic field strength

[0023] - Frequency of the magnetic field direction

[0024] - Phase in relation to the drive magnetic field

[0025] The preceding list is not exhaustive. Naturally, two or more such magnetic field parameters can be combined when carrying out a monitoring method according to the invention. In the simplest case, the magnetic field strength and / or the magnetic field direction is monitored. However, with continuous or at least partially continuous monitoring, gradients of the magnetic field strength and / or the magnetic field direction can also be monitored. Finally, since this is a rotating drive magnetic field, the frequency of the magnetic field strength and / or the frequency of the magnetic field direction, as well as corresponding superimposed frequencies, can also provide information about the rotation status of the magnetic stirrer.In particular, the rotational speed of the drive magnetic field can be compared with the rotational speed of the magnetic stirrer in this way, and this can be carried out in the comparison step of a monitoring method according to the invention.

[0026] A further advantage can be achieved if the monitoring result is output and / or saved in a monitoring method according to the invention. Such output can be, for example, audible and / or visual, such as an alarm. However, not only the error state is of interest, but also, for example, a green "OK" indicator is advantageous in the context of the present invention. When an alarm is output as an audible or visual error signal, the operating personnel can intervene quickly, so that, particularly in long-term experiments, they do not have to be interrupted or the experimental results jeopardized. The output can also be saved and used for documentation purposes, in order to easily provide automated qualitative and / or quantitative evaluation, especially when documenting experimental procedures.

[0027] Furthermore, it is advantageous if, in a monitoring method according to the invention, a drag angle for the magnetic stirrer relative to the drive magnetic field is determined from the comparison. Such monitoring of the drag angle allows, for example, conclusions to be drawn about the information concerning the stirred liquid. Conversely, information, for example regarding the viscosity of the stirred liquid, can also be used to provide a corresponding comparative value. Thus, with highly viscous liquids, the magnetic stirrer will exhibit a larger drag angle relative to the drive magnetic field than with very low-viscosity liquids. If the drag angle increases too much, there is a risk of the drive magnetic field slipping, i.e., spinning freely.Thus, as will be explained later, if the drag angle becomes too large, intervention can be made in the drive magnetic field to prevent such a drive failure or to re-engage a stalled magnetic stirrer. Monitoring the drag angle can also, directly or indirectly, ensure the safe start-up of a magnetic stirrer or electromagnetic stirring device.

[0028] A further advantage can be achieved if, in a monitoring method according to the invention, a linearity and / or dependency of at least one magnetic field parameter is determined by comparison. For example, if a liquid is stirred with a magnetic stirrer, there is a point in time from which a so-called tornado forms. Such formation of a tornado, i.e., a downward pull of the liquid's surface down to the magnetic stirrer, leads to nonlinearity in the rotation or in other magnetic field parameters. This is due in particular to the fact that the opposing forces of the liquid on the stir bar change abruptly both when the tornado forms and when it dissipates. Monitoring a linearity and / or dependency by means of comparison thus makes it possible to detect the formation, but also the dissipation, of such a tornado and to consider the arrangement or...to extend or carry out the monitoring procedure in response to the presence of the tornado.

[0029] Further advantages can be achieved if, in a monitoring method according to the invention, a gradient of the temporal change of at least one magnetic field parameter is determined from the comparison. This allows the temporal change to also be included in the monitoring functionality. In particular, the gradient can be used with reference to the rotational speeds or differences in rotational speeds described above when monitoring slip and / or the following angle. Last but not least, the gradient also allows for good monitoring with regard to the linearity described in the preceding paragraph.

[0030] It is also advantageous if, in a monitoring method according to the invention, a stirring speed, particularly in the form of a rotational speed, of the magnetic stirrer is determined from the comparison. Such a stirring speed can form the basis for monitoring the slip and / or the drag angle, as already explained. The stirring speed can also provide feedback on the qualitative monitoring of the stirring functionality as well as the stirring result. Thus, there is an ideal stirring speed for every stirring task to ensure that the liquid is carried along and a good stirring result is achieved. Therefore, monitoring the stirring speed allows not only the magnetic stirrer itself, but also the result of the stirring task to be monitored.

[0031] It is also advantageous if, in a monitoring method according to the invention, the drive magnetic field is additionally monitored. This monitoring of the drive magnetic field can be provided by direct measurement, by measurement with the magnetic field sensor, or by information from the corresponding driving magnetic coils. In particular, this monitoring can be used to provide additional information for the comparison value in the comparison step of the present monitoring method. The drive magnetic field can be monitored, for example, with regard to the rotational speed, the drive force, or even with regard to the basic presence of the drive magnetic field.

[0032] It is also advantageous if, in a monitoring method according to the invention, the drive magnetic field is modified based on the monitoring results to stabilize the magnetic stirrer. Such a modification allows for temporal and / or quantitative intervention. For example, if it is detected that the drag angle of the magnetic stirrer is increasing, there is a risk of drive failure and thus of the magnetic stirrer stalling. Such destabilizing situations can be countered, for example, by slowing down the rotation of the drive magnetic field and thus reducing the drag angle. Destabilizing effects can therefore be detected and addressed, leading to an improvement in the stability of the magnetic stirrer.It is further advantageous if, in a monitoring method according to the invention, the drive magnetic field is modified based on the monitoring result to restabilize the magnetic stirrer. In contrast to the situation described in the preceding paragraph, it can happen that the magnetic stirrer enters a destabilized state, i.e., comes to a standstill. In such a case, the stationary magnetic stirrer can now be detected using the monitoring result, so that, to restabilize it, the drive magnetic field is decelerated and restarted in order to recapture the magnetic stirrer and set it into rotation again. Naturally, to avoid destabilizing effects, the stabilization effect can also be combined with the restabilization effect described in this paragraph.

[0033] Also related to the present invention is a monitoring device for monitoring a magnetic stirrer of an electromagnetic stirring device, comprising a sensor device with at least one magnetic field sensor having a detection direction for detecting magnetic field lines and a blind direction different from the detection direction, without detection of magnetic field lines. The blind direction is aligned along the magnetic field lines of a drive magnetic field of the stirring device. A monitoring device according to the invention includes a monitoring module for monitoring the magnetic field lines along the detection direction of the magnetic field sensor. Furthermore, a comparison module is provided for comparing at least one magnetic field parameter of the monitored magnetic field lines with a reference value. In addition, the monitoring device includes a generation module for generating a monitoring result based on the comparison.The monitoring device, and in particular the monitoring module, the comparison module, and / or the generation module, are preferably configured for carrying out a method according to the invention. Thus, a monitoring device according to the invention offers the same advantages as those explained in detail with reference to a monitoring method according to the invention.

[0034] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination. Figure 1 schematically shows an embodiment of a stirring device with a magnetic field sensor.

[0035] Figure 2 shows a detailed view of a magnetic field sensor.

[0036] Figure 3 shows another file representation of a magnetic field sensor,

[0037] Figure 4 shows a representation of a comparative value.

[0038] Figure 5 shows another representation of a comparative value,

[0039] Figure 6 shows another representation of a comparative value,

[0040] Figure 7 shows another representation of a comparative value,

[0041] Figure 8 shows another representation of a comparative value and

[0042] Figure 9 shows a representation of a following angle.

[0043] The following briefly illustrates the operation of a monitoring method according to the invention with reference to Figures 1 to 3. Such a monitoring method is used, for example, in a stirring device 100 as shown in Figure 1. Here, four electromagnetic coils and corresponding pole shoes are schematically depicted, which allow a rotating drive magnetic field (AM) to be generated. Additionally, a sensor device 110 with a magnetic field sensor 112 is arranged laterally between two pole shoes of the stirring device 100. The orientation of the magnetic field sensor 112 is of crucial importance and is explained in more detail with reference to Figures 2 and 3. In particular, the magnetic field sensor 112 is arranged between the pole plates and / or at the same height as the pole plates.

[0044] Figure 2 shows an orientation of a magnetic field sensor 112 with a blind direction BR and a detection direction ER. If a drive magnetic field AM is present, its magnetic field lines M are oriented such that they are essentially aligned exclusively along the blind direction BR of the magnetic field sensor 112. This means that in this situation, the magnetic field sensor 112 cannot detect any magnetic field lines M, and therefore no corresponding magnetic field parameters MP are detectable.

[0045] When a magnetic stirrer 200 is attached, the drive magnetic field AM is diffracted to form a combined magnetic field KM, as shown, for example, in Figure 3. The diffracted magnetic field lines M now also run, at least partially, along the detection direction ER, so that corresponding information can be detected by the magnetic field sensor 112. It should be noted that Figure 3 shows a static situation, which is merely a description of the actual dynamic situation. In other words, the combined magnetic field KM changes continuously due to the rotation of the magnetic stirrer 200, and in particular at a regular frequency.

[0046] In its simplest form, an evaluation according to Figure 4 of a magnetic field sensor MP can be performed, for example, along the magnetic field strength over time. As soon as a magnetic field parameter MP, in the form of magnetic field strength, exceeds the reference value VW as a threshold, the presence of the magnetic stirrer 200 can be distinguished from its absence. Figure 5 shows a further development, for example, where the magnetic field strength is monitored during rotation as the magnetic field parameter MP over time. Here, the amplitude can provide information about the strength of the magnetic field diffraction and thus the magnetization strength of the magnetic stirrer. This allows feedback as to whether the magnetic stirrer 200 is too large or too small, as indicated by the magnetic field parameter MP with respect to the reference value VW in the form of amplitude.

[0047] Figure 6 shows the monitoring of the frequency as a magnetic field parameter MP against the reference value VW, so that the rotational speed, particularly in relation to slip or following angle α, can be used here. Figure 7 schematically shows how monitoring a gradient as a reference value VW can also provide information about the linearity of the magnetic field parameter MP's behavior. This is, for example, a possible curve for the formation of a tornado, as already explained.

[0048] Figure 8 shows one way to use a list of comparison values ​​VW, i.e., when a kind of characteristic map or list function is required for a large number of different magnetic field parameters MP. A corresponding selection allows feedback on the monitoring result.

[0049] Figure 9 schematically illustrates how a drag angle α is defined. A rotating drive magnetic field AM is provided. This field is oriented north-south, in this case along the axis from top to bottom, and rotates at the corresponding drive speed. The magnetic stirrer 200 rotates downstream with a drag angle α, also oriented north-south, which here is set at an angle of approximately 45°. If the drag angle α changes over time, slippage can be assumed, resulting in different rotational speeds of the drive magnetic field AM and the magnetic stirrer 200.

[0050] The preceding explanation of the embodiments describes the present invention solely by way of examples. Naturally, individual features of the embodiments can be freely combined with one another, provided this is technically feasible, without departing from the scope of the present invention.

[0051] Reference symbol list

[0052] 10 Monitoring device

[0053] 20 Monitoring module

[0054] 30 Comparison module

[0055] 40 generation module

[0056] 100 stirring device

[0057] 110 Sensor device

[0058] 112 Magnetic field sensor

[0059] 200 magnetic stirrers

[0060] M magnetic field line

[0061] ER detection direction

[0062] BR Blind direction

[0063] AM drive magnetic field

[0064] KM combination magnetic field

[0065] MP magnetic field parameters

[0066] VW comparative value a trailing angle

Claims

Patent claims 1. Monitoring method for monitoring a magnetic stirrer (200) of an electromagnetic stirring device (100) with a sensor device (110) having at least one magnetic field sensor (112) with a detection direction (ER) for detecting magnetic field lines (M) and a blind direction (BR) different from the detection direction (ER) without detecting magnetic field lines (M), which is aligned along magnetic field lines (M) of a drive magnetic field (AM) of the stirring device (100), comprising the following steps: - Monitoring the magnetic field lines (M) along the detection direction (ER) of the magnetic field sensor (112), - Comparing at least one magnetic field parameter (MP) of the monitored magnetic field lines (M) with a reference value (VW), - Generating a monitoring result based on the comparison.

2. Monitoring method according to claim 1, characterized in that the comparison value (VW) has at least one limit value for a qualitative distinction between falling below and exceeding the limit value.

3. Monitoring method according to one of the preceding claims, characterized in that the reference value (VW) contains quantitative information for the at least one magnetic field parameter (MP).

4. Monitoring method according to one of the preceding claims, characterized in that at least one of the following magnetic field parameters (MP) is used: - Magnetic field strength - Magnetic field direction - Gradient of magnetic field strength - Gradient of the magnetic field direction - Frequency of the magnetic field strength - Frequency of the magnetic field direction - Phase with respect to the drive magnetic field (AM) 5. Monitoring method according to one of the preceding claims, characterized in that the monitoring result is output and / or stored.

6. Monitoring method according to one of the preceding claims, characterized in that a trailing angle (a) for the The magnetic stirrer (200) is determined relative to the drive magnetic field (AM).

7. Monitoring method according to one of the preceding claims, characterized in that a linearity and / or dependence of the at least one magnetic field parameter (MP) is determined from the comparison.

8. Monitoring method according to one of the preceding claims, characterized in that a gradient of the temporal change of the at least one magnetic field parameter (MP) is determined from the comparison.

9. Monitoring method according to one of the preceding claims, characterized in that a stirring speed of the magnetic stirrer (200) is determined.

10. Monitoring method according to one of the preceding claims, characterized in that additional monitoring of the drive magnetic field is included. (AM) is carried out.

11. Monitoring method according to one of the preceding claims, characterized in that the drive magnetic field (AM) is changed on the basis of the monitoring result to stabilize the magnetic stirrer (200).

12. Monitoring method according to one of the preceding claims, characterized in that the drive magnetic field (AM) is changed on the basis of the monitoring result to restabilize the magnetic stirrer (200).

13. Monitoring device (10) for monitoring a magnetic stirrer (200) of an electromagnetic stirring device (100) with a sensor device (110) with at least one magnetic field sensor (112) with a detection direction (ER) for Detection of magnetic field lines (M) and a blind direction (BR) different from the detection direction (ER) without detection of magnetic field lines (M) which is aligned along magnetic field lines (M) of a drive magnetic field (AM) of the stirring device (100), the monitoring device (10) comprising a monitoring module (20) for monitoring the magnetic field lines (M) along the detection direction (ER) of the magnetic field sensor (110), a comparison module (30) for comparing at least one magnetic field parameter (MP) of the monitored magnetic field lines (M) with a comparison value (VW) and a generation module (40) for generating a monitoring result based on the comparison.

14. Monitoring device (10) according to claim 13, characterized in that the monitoring module (20), the comparison module (30) and / or the generation module (40) are configured for an embodiment of a method having the features of one of claims 1 to 12.

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