MEASURING SYSTEM FOR FOODSTUFFS

Abstract

A measuring system automatically determines and/or monitors quality of a dairy product. The measuring system includes a housing for a container containing the dairy product, a viscosity measuring device, and a control unit. The viscosity measuring device includes a magnetic first body, an electromagnetic drive, and a detection system that detects displacement of the magnetic first body. The electromagnetic drive includes a plurality of individually controllable coils in a stack. The control unit is configured to individually energize the coils in a predetermined pattern in such a way that the magnetic first body is displaced. The magnetic first body is able to be readily pulled up, even in viscous liquids, but can also be pulled down in a controlled manner so that the viscosity can be measured more accurately.

Claims

1. A measuring system for automatically determining and/or monitoring a quality of a liquid or a viscous foodstuff, and comprising: a housing with a space for accommodating at least one container for the liquid or viscous foodstuff, at least one container for or with the foodstuff, with a probe which projects into the container and comprises a thermometer, a viscosity measuring device for determining a viscosity value of the foodstuff in the space, and a control unit which is configured for controlling the measuring system, and which is operatively connected to the viscosity measuring device for repeatedly performing a viscosity measurement and storing and/or exporting and/or processing a determined viscosity value, wherein the viscosity measuring device comprises: a magnetic first body, a controllable electromagnetic drive for the magnetic first body, and a detection system for detecting displacement of the magnetic first body, comprising a plurality of proximity sensors, wherein the magnetic first body, in use, surrounds the probe and is displaceable around the probe on account of the electromagnetic drive, wherein, in use, the magnetic first body is situated in the container, wherein the electromagnetic drive comprises a plurality of individually energizable coils which are wound around the container which are stacked in a stack, and wherein the control unit is configured to individually energize the coils in a predetermined pattern, in such a way that the magnetic first body is displaced in the container.

2. The measuring system according to claim 1, wherein the predetermined pattern is adjustable.

3. The measuring system according to claim 1, wherein the predetermined pattern comprises repeatedly energizing successive coils in a reciprocating cycle.

4. The measuring system according to claim 1, wherein the predetermined pattern comprises successively temporarily energizing one of the coils and temporarily energizing an adjacent coil after a delay time, in such a way that the magnetic first body is displaced in the container at a velocity, and wherein the control unit is configured to adjust at least one of the delay time and the velocity.

5. The measuring system according to claim 1, wherein the plurality of proximity sensors are provided on an elongate carrier in the container.

6. The measuring system according to claim 1, wherein the plurality of proximity sensors are provided between the container and the plurality of coils.

7. The measuring system according to claim 1, wherein the plurality of proximity sensors are placed at a mutual distance apart which, in use, increases in a downward direction.

8. The measuring system according to claim 1, furthermore provided with further comprising a cleaning device, comprising a magnetic second body which, in use, is provided in the container under the magnetic first body and is displaceable on account of the coils, and is provided with a cleaning part on an outer periphery which bears against an inner wall of the container, wherein a stop is provided on the elongate carrier and/or on the inner wall of the container for cooperation with the magnetic second body, wherein the stop determines a maximum elevation for the magnetic second body which is lower than a maximum elevation for the magnetic first body.

9. The measuring system according to claim 1, furthermore comprising a conditioning unit for conditioning the space of the housing, comprising a heating and cooling device, and is operatively connected to the thermometer.

10. The measuring system according to claim 9, wherein the control unit is configured to control the conditioning unit, comprising causing the space of the housing to undergo a predetermined time-temperature program.

11. The measuring system according to claim 1, wherein the detection system for detecting displacement of the magnetic first body comprises a plurality of Hall sensors.

Description

[0038] FIG. 1 diagrammatically shows a perspective view of a measuring system 1 according to the invention,

[0039] FIG. 2 shows a diagrammatic and partly cut-away perspective view of a portion of a module 2 of the measuring system 1 according to the invention,

[0040] FIG. 3 diagrammatically shows a perspective sectional view of a portion of a measuring probe 7,

[0041] FIG. 4 shows a detail view of optical components of the measuring probe 7 from FIG. 3,

[0042] FIG. 5 diagrammatically shows a cross section through a measuring probe 7′ according to the invention,

[0043] FIG. 6 diagrammatically shows a perspective view in partial cross section of the measuring probe 7′ from FIG. 5, and

[0044] FIG. 7 diagrammatically shows a perspective view of the first body 61.

[0045] FIG. 1 diagrammatically shows a perspective view of a measuring system 1 according to the invention, with ten modules 2 and an external control device 3.

[0046] Each module 2 has a space 4 for accommodating containers 5 and a lid 6. Reference numeral 7 denotes a measuring probe and reference numerals 22a and 22b denote electrical contacts and countercontacts, respectively.

[0047] The measuring system 1 illustrated here has ten modules 2, but may have any desired other number of modules, such as 1, 2, etc. This number can advantageously be changed during use. Furthermore, each module 2 here comprises a space 4 in which five containers 5 are arranged. The number of containers can also be chosen freely from 1, 2, etc., in which case the amount of space available in the space 4 has to be taken into account, for example by matching the dimensions of the containers 5 thereto.

[0048] Each container 5 can accommodate a foodstuff, for example a dairy product such as milk, yoghurt, quark, etc., but also any other low-viscosity or high-viscosity foodstuff, such as a fruit juice or fruit nectar, etc. After the container 5 has been filled, a measuring probe 7 can be introduced which is provided with one or more measuring instruments and the like. These may be operated and read out via electrical contacts. During closing of the lid 6, the countercontacts 22b are pressed against the contacts, following which the measuring probe(s) are in communication with, for example, the control device 3, and can then perform measurements. These measurements may be of many different kinds, as will be explained below later. The measurement data can then be exported to the external control device 3, where they may, for example, be stored, displayed and/or processed. Incidentally, the control device 3 may also be provided as an integral part of the measuring system, for example distributed over the modules 2. Furthermore, the control device may serve to control the measurements, for example to determine the moment of measuring. This will also be explained below in more detail.

[0049] FIG. 2 shows a diagrammatic and partly cut-away perspective view of a portion of a module 2 of the measuring system 1 according to the invention. The module 2 has a housing 10 containing the space 4 for the containers 5. A number of coils 11 are arranged around each container 5 between partitions 12. Reference numeral 13 denotes a Peltier cooling system, which cools a buffer vessel 14, while reference numeral 15 denotes a ventilator. A cooling circuit 16 is fed by means of pump 17, whereas reference numeral 18 denotes a connection for a heating system.

[0050] The coils 11 are individually electrically energisable and serve to displace a magnetisable body (not shown here) in the container 5 while measuring the viscosity of the product in the container 5. All this will be explained in more detail further below.

[0051] The product in the container 5 or the products in the various containers 5, respectively, may be conditioned by means of the conditioning unit, which comprises a heating system and a cooling system. Heating is provided (for example) via the connection 18 in the form of electrical heat. It is obviously possible to provide heat in a different way, but electrical heat has the advantage that it is readily and quickly controllable by means of a thermometer (not shown here). It should be stressed here that the various containers in one module may either be heated to the same temperature or, and advantageously, to different temperatures, by controlling the heating connection 18 differently, such as different heating coil density or a circuit with a different and adjustable PWM, etc.

[0052] In order to cool the product in the container(s) to a desired end temperature, two cooling systems are provided here. One cooling system comprises a cooling circuit 16 in which a coolant, such as glycol or water, is pumped around by means of the pump 17. Furthermore, a heat exchanger (not shown) is provided, such as cooling fins, in order to dissipate the heat taken up to the open air or the like. Optionally, however, a second cooling system is provided and in particular in the form of a selectable path of the cooling circuit via a buffer vessel 14. This contains a buffer for refrigeration to a desired (end) temperature in the form of a phase change material which has been cooled by means of the Peltier cooling system 13, at least latent heat has been withdrawn. To this end, for example, paraffin, water or the like has been converted from the liquid phase to the solid phase. Other phase transitions are not excluded. By subsequently switching a valve or the like in the cooling circuit 16, the coolant in the cooling circuit can be passed along or through the buffer vessel 14 in order to dissipate more heat there and to assume the (melting or at least phase transition) temperature of the buffer vessel more rapidly and for a prolonged period of time. In this way, forced cooling is possible without requiring a great deal of power, in this case using a Peltier cooling system 13 without moving parts but having the other associated advantages.

[0053] Furthermore, the control device of the measuring system, such as the external control device 3 from FIG. 1, is advantageously configured to provide a desired temperature profile in the or each module 2. This temperature profile may comprise different temperatures for the various containers 5 (and thus for the products contained therein) in the module 2, but also a temperature-time profile, in which the temperature is specified as a function of time. For example, it is thus possible to examine the behaviour of and the changes in a product under specific thermal conditions. Thus, a product may be left unrefrigerated in the sun during transportation for some time or, for example, it may be removed from a refrigerator repeatedly for use on a table, etc. In this case, the prevailing temperatures are different every time. In order to keep the measurements “clean”, a forced cooling system offers advantages, due to the fact that it excludes lagging effects of cooling down at different speeds as much as possible. However, this forced cooling by means of the cold buffer vessel 114 is optional.

[0054] FIG. 3 diagrammatically shows a portion of a measuring probe 7 in a perspective sectional view. The measuring probe 7 comprises a cover 21 which, in the closed position, adjoins the container 5 and which is provided with electrical connections 22. On the inside, a reflecting layer 23 has been provided, as well as LEDs 24.

[0055] Reference numerals 25, 26 and 27 denote a first, a second and a third light conductor, respectively, reference numeral 28 denotes two light detectors and reference numeral 30 denotes a mounting plate, on which there are three EIS (electr(ochem)ical impedance spectroscopy) electrodes 31.

[0056] A camera 32 looks through a window 33 and communicates with camera control unit 34.

[0057] In this case, the measuring probe 7 comprises some measuring devices for measuring different properties, each of which are optional per se. For example, optical properties, such as transmission and diffusion, are measured. To this end, light is injected in the product in the container. This is performed by means of LEDs 24 which inject light in the first light conductor 25 via the reflective layer 23, following which transmitted light is injected in the second light conductor 26, and diffused light into the third light conductor 27. All this is explained in more detail in FIG. 4.

[0058] Furthermore, EIS electrodes 31 are optionally provided on a plate 30. By means of the EIS electrodes, dielectric permittivity spectra or electrochemical impedance spectra of the product in the container 5 are determined in a manner known per se. Therefore, reference should be made to the prior art for details relating to the EIS measurements. An advantage is that these spectra can be determined for many products, but in particular also for many conditions, such as temperatures and temperature-time profiles.

[0059] The optional camera 32 offers the possibility of obtaining a visual or other optical image of the product. This may be particularly advantageous in order to monitor if changes occur, such as for example as a function of the time, the temperature, and/or the temperature-time profile. The changes may consist of a change in colour, changing transparency/turbidity, formation of depositions, etc. The camera control unit 34 advantageously comprises image-processing software. However, it is also possible to collect simple images with the camera 32 and to send these to an external processor via the camera control unit 34.

[0060] The communication from the measuring probe 7 to the “outside world” takes place, in particular, via the electrical connections 22, for example for the sake of energising the LEDs 24, reading out/actuating the detectors 28, the EIS electrodes 31 and the camera 32/the camera control unit 34, and any other components which have been provided.

[0061] FIG. 4 provides a detail view of optical components of the measuring probe 7 from FIG. 3. In this figure, and in the entire drawing, identical or similar components are denoted by the same reference numerals.

[0062] The measuring probe 7 comprises four LEDs, here a red LED 24-1, a green LED 24-2, a blue LED 24-3, and an infrared LED 24-4. During use, they emit light, which is denoted by reference numeral 50, and which is reflected by layer 23 on the inside of the cover 21. A portion 51 of the light 50 is injected in the first light conductor 25 via the first injection surface 40, is reflected by surface 46 and ejected via the first ejection surface 41. The ejected light is partly transmitted by the product as transmission portion 52, and captured and injected in the second light conductor via the second injection surface 42 to form portion 54, which is detected by first detector 28-1. The ejected light diffuses for another portion 53 in the product and is captured and ejected in the third light conductor 27 via the third injection surface 44 to form 55, which is detected by the second detector 28-2.

[0063] At least on the inside, the cover 21 is virtually semispherical and provided with a (diffuse or otherwise) reflective layer, such as magnesium oxide or barium sulfate, or gold, in particular if infrared measurements have to be performed. Thus, the (inside of the) cover is an integrating sphere which will evenly distribute the emitted light 50 for the sake of an even injection in the first light conductor 25. Incidentally, other injection methods, and the associated construction of the measuring probe 7, are not excluded. In this example, said light is emitted by the LEDs 28-1 to-4, being red, green, blue and infrared, respectively. However, any other light source or colour distribution/number of colours is also possible, such as specific colours, which may also be produced by lasers, or wide-band sources, such as halogen lights, etc. However, LEDs have advantages, such as compactness, long service life, high efficiency and availability in many colours with a relatively small bandwidth. LEDs 28-1 to-4 may be actuated separately from one another, so that no undesired influencing of the detectors 28-1 and-2 can occur.

[0064] For a more detailed explanation of the operation, only the red LED 28-1 is considered here, but a similar explanation applies to the other LEDs. The red LED 28-1 is actuated by the control unit (not shown here and, for example, external) in a desired pattern, such as once a minute. The emitted light reflects diffusely on the reflective layer 23 and will land relatively homogenously on the first injection surface 40 of the first light conductor 25. A portion 51 will be injected therein.

[0065] In this case, the first light conductor 25 is an optical fiber, such as a glass fiber or plastic fiber, as are the second and third, 26 and 27, respectively. These serve to transport the light by means of total internal reflection, so that losses are limited to the (small) absorption losses. However, in view of the mostly small distances, it is also possible to use a hollow, internally mirroring tube or a tube of transparent material which has been made reflective on the outside as a light conductor. An advantage of the latter is that more light can be injected, since the limitation of the critical entrance angle no longer applies.

[0066] The portion 51 which is injected reaches the surface 46 which is at virtually 45 degrees with the longitudinal direction of the first light conductor 25 here, and will then, in use, exit substantially horizontally from the first ejection surface 41, as light portion 52 and light portion 53, or light which is transmitted or diffused by the product in the container, respectively. The transmitted portion 52 reaches the second injection surface 42 of the second light conductor, and a portion of the injected light passes on, after mirroring on the surface 47, likewise placed at virtually 45 degrees, as portion 54 to the second ejection surface 43. There, the exiting light is detected by the light detector 28-1, as an indication for the transmission properties of the product.

[0067] Another portion of the light, portion 53 is diffused in the product, and can reach the third injection surface 44 of the third light conductor 27. It should be noted that it is precisely due to the use of the relatively limited critical injection and thus also ejection angle of optical fibers, that it is easy to prevent the third light conductor 27 from injecting direct and thus transmitted light, by placing the third injection surface 44 beyond the critical exit angle of the first light conductor 25. The light injected in the third light conductor 27 will reach the third ejection surface 45 as portion 55, and will be detected there by the light detector 28-2, as an indication for diffusion properties of the product.

[0068] By means of the illustrated embodiment, light can be injected in the product in an elegant way, with both the sources and the detectors and the control unit remaining outside the product. Obviously, other optical measuring methods also remain possible, such as when the LEDs 24, or other sources, are placed around the outside of the container, with the associated detectors also being situated around the container, so that the light passes through the entire container and the product. In particular with optically very dense products, such as dairy products, the latter barely makes sense, however.

[0069] FIG. 5 diagrammatically shows a cross section through a measuring probe 7′ according to the invention. In this case, it comprises a plate 30 next to which light conductors 25, 26, 27 are arranged. Furthermore, reference numerals 60-1, . . . , 60-10 denote ten coils around the container 5 and reference numerals 61 and 62 denote a first and second body, respectively, whereas reference numeral 63 denotes brushes and 64 denotes lugs.

[0070] The coils 60-1 to 60-10 are individually energisable via their respective connections, on the right in the figure, by means of an external power supply (not shown), under control of the control device, likewise external and not shown here. The magnetic field generated by the coil(s) attracts the first body 61 which is at least partly made of magnetic material, such as a permanent magnet or iron. When successively energising the bottom coil 60-1, then de-energising it and energising the penultimate coil 60-2, etc., the first body 61 can be pulled upwards. In this case, it should be noted that, in principle, any number of coils 60-xxx may operate satisfactorily, with more coils ensuring a smoother movement.

[0071] When it arrives at the top, the first body 61 can start a falling movement through the product in the container 5 by de-energising all coils. This falling movement may be detected by means of proximity sensors, in particular Hall sensors. In this context, see FIG. 6 and the description thereof.

[0072] An advantage of this stepped upward drive, compared to the “shooting” upwards by means of a single coil, which generates a sudden strong field, is the fact that the velocity in the product can be limited and controlled. Particularly dairy products can have a very high viscosity, so that such a “launching” cannot work well, at least is not readily controllable.

[0073] It should furthermore be noted that, in particular with very high viscosities, it is also possible to attract the body by means of the coils. With a very low fall velocity, the (proximity/Hall) measurement often becomes inaccurate. It may then be helpful to increase this velocity by pulling the first body 61 using one or more additional coils. The magnetic force then has to be added to the force of gravity for the calculations. In this way, the viscosity can be determined with greater accuracy and in particular for a greater dynamic range, that is to say the viscosity as a function of the (end) velocity.

[0074] The illustrated first body 61 may furthermore serve as a stirrer, for example driving the magnetic material with a magnetic drive (not shown), which is known per se for magnetic stirrers.

[0075] Furthermore, a second body 62 is shown which is also at least partly made of magnetic material and can thus be moved up and down by energising the coils 60. The second body also comprises brushes 63, advantageously made of a flexible material, such as rubber or the like. The cross section of the second body 62 with the brushes 63 is such that the brushes 63 can clean the inside of the container 5 by friction when moving up and down. To this end, the coils 60 can move the second body 62 up first, such as more or less together with the first body 61. However, while the first body 61 can move upwards completely, that is to say as far as the top coil 60-10, the second body 62 is only able to rise as far as the lugs 64. As a result thereof, the first body 61 and the second body 62 can be separated mechanically. By now holding the first body 61 securely with the top coil 60-10, and de-energising the other, or energising even lower coils, the second body will move down. In this case, “pulling” using correspondingly energised coils will aid cleaning, in particular when the frictional force is great, which is fundamentally desired when cleaning. In this way, the second body 62 can be moved to and fro a few times by switching the coils 60 on and off in a corresponding way. Incidentally, the first body 61 and the second body 62 can also already be separated at the bottom by keeping the bottom coil 60-1 energised while energising the higher coils 60-2, 60-3, . . . With suitable dimensions, in particular the height, of the second body 62, the first body 61 will then be attracted more by the higher coil 60-2 than by the bottom coil 60-1, while the opposite applies to the first body 61.

[0076] FIG. 6 diagrammatically shows a perspective view in partial cross section of the measuring probe 7′ from FIG. 5, but without the light conductors 25, 26 and 27, and without the coils, but now with the plate 30, which carries the EIS electrodes 31, a thermometer 65 and the Hall sensors 66.

[0077] The function of the thermometer 65 will be clear and that of the EIS electrodes has already been mentioned briefly above. The Hall sensors 66 serve to detect the passing of first body 61 and to determine the fall velocity of the first body from the difference time between passing the successive Hall sensors, according to a technique which is known per se. In this case, the Hall sensors 66 are placed at a mutual distance which increases towards the bottom, so that the measuring resolution is maintained at increasing fall velocity.

[0078] FIG. 7 diagrammatically shows the first body 61 in perspective. It comprises a tube 70 with a hole 71, as well as single fins 72 with a tapered top side 73. The tube 70 and/or the fins 72 are made from or with a magnetic material. The hole has a cross section which is greater than the width of the plate 30 with the lugs 64. As a result thereof, the first body 61 can move freely from the top to the bottom. The fins 72 have a tapered top side in order to encounter a reduced friction, at least when moving up. It should be noted here that the illustrated sensor/measuring devices for optical, (di)electrical, viscosity and other properties can be combined as desired in a measuring probe/measuring system according to the invention. In particular in combination with the hot and cold conditioning, if desired with a predeterminable time-temperature variation, valuable information about the products can be collected in an automatic and standardised way, so that, for example, human errors of judgement can be avoided.

[0079] By regularly repeating the optical, (di)electrical, viscosity and/or other measurements for different temperatures, times and temperature profiles, it is possible to determine product properties and which products are suitable for certain applications. For example, it is thus possible to determine the product composition which, from a bacterial point of view or otherwise, is most resistant to temperature variations, etc.

[0080] In a practical setup, for example as shown in FIG. 1, ten modules 2 are each filled with five containers 5 containing one or more products, such as a dairy product. In an example, the simplest time-temperature profile is applied, namely a constant temperature, but with each container having a different temperature. The parameters being measured are the viscosity (at one fall velocity, i.e. without additional “pulling” by the coils), the transmission and diffusion for four wavelengths, and an EIS spectrum. Starting with one measurement per hour, this simplest case already delivers a wealth of information each day (1200 EIS spectra and more than 10,000 other measured values). As all this is done automatically and, based on the measured values, subsequent steps may optionally follow, it is possible to determine a series of product properties in a very efficient way and/or a selection can be made between various products at mutually identical conditions. Such subsequent steps are, for example, automatically indicating if a product no longer meets the product criteria with regard to viscosity, transparency (transmission), etc. The test for the respective product can then be terminated, thus making room for another product, etc.