Patent Publication Number: US-2021185972-A1

Title: Milking system with detection system

Description:
The present invention relates to a milking system, comprising a milking means for milking milk from a dairy animal, a milk line in fluid connection with the milking device, a sampling and analysis device arranged to take a sample of the milk from the milk line and to analyse milk from the sample, wherein the sampling and analysis device comprises a control unit for controlling the sampling and analysis device, a tape mover, arranged to move and unwind, under the control of the control device, a tape wound on a tape reel carrying the tape, said tape comprising a base material with provided thereon a series of reagent pads that are arranged to provide a detectable response in the presence of at least one substance in the sample, a dosing device arranged to provide, under the control of the control unit, a part of the sample onto one of the reagent pads, and an optical sensor device arranged to detect optical radiation from said reagent pad supplied with said part of the sample, and to analyse the detected optical radiation to provide an indication of a presence or concentration of said at least one substance. 
     Document WO02069697A1 discloses an apparatus for analysing milk samples, thus for use in a milking system, in which apparatus drops of milk are supplied to a tape carrying dry test sticks with reagent. A general desire for such apparatus is that they can be used in milking systems during a long time period. In particular milking robots have the advantage of being able to function without human intervention. It is then desirable that peripheral equipment can also perform unattended. Since it may be necessary, or at least desirable, to test each cow at each milking, the number of tests may be very high during any reasonable testing period. For example, a milking robot serving 60 cows, with on average three milkings per day, may require about 2.500 samples in a two week period. Obviously, in order to reduce the amount of reagent used in these samplings, the reagent pads should preferably be small. 
     A problem with the known apparatus is that it is difficult to allow for smaller reagent pads while still exerting a good control over the sample drop delivery. 
     It is therefore an object of the present invention to provide a milking system of the kind mentioned above, with an improved control over the supply of the sample to the reagent. Another object is to enable the use of small reagent pads. Yet another object is to minimise spill of sample liquid, as this may be the cause of undesired pollution of the sampling and analysis environment. 
     The present invention achieves at least one of these objects by means of a milking system according to claim  1 , in particular a milking system, comprising a milking means for milking milk from a dairy animal, a milk line in fluid connection with the milking device, a sampling and analysis device arranged to take a sample of the milk from the milk line and to analyse milk from the sample, wherein the sampling and analysis device comprises a control unit for controlling the sampling and analysis device, a tape mover, arranged to move and unwind, under the control of the control device, a tape wound on a tape reel carrying the tape, said tape comprising a base material with provided thereon a series of reagent pads, that are arranged to provide a detectable response in the presence of at least one substance in the sample, a dosing device arranged to provide, under the control of the control unit, a part of the sample onto one of the reagent pads, and an optical sensor device arranged to detect optical radiation from said reagent pad supplied with said part of the sample, and to analyse the detected optical radiation to provide an indication of a presence or concentration of said at least one substance, wherein during provision of the part of the sample the reagent pad is facing downward and an optical path to the optical sensor passes upwardly through the base material of the tape. 
     When the reagent pad, i.e. the active and fluid-receiving part, faces downward, gravity assists in the control of sample liquid supply, in that it does not exert an additional force on the liquid during supplying, but rather a counteracting force. This means that the chance of too much liquid being provided onto the reagent is much reduced. This in turn allows the use of a smaller reagent pad, as well as it reduces the chance of supplied liquid spilling over too a neighbouring reagent pad. Alternatively, just because that risk has been reduced, it is now possible to limit the measures that should prevent this spilling, such as a too great distance between the reagent pads or the like. In addition, in case there would still be provided too much liquid to the reagent pad, it is likely that this will be collected again by the sample supply system, since gravity would pull the liquid back into that direction. Moreover, and not in the last place, it is much easier to suck away excess fluid in the system according to the present invention than in the known systems in which droplets are provided from above. In the latter case it is likely that, when a sample droplet falls, or is sucked, onto a reagent pad, air is sucked into a nozzle or sample supplying line. This prevents any liquid from being sucked back, as the connection between the (contents of the) nozzle or sample supplying line has been broken. This will not, or at the most hardly ever, happen in the present case of supplying the sample from below. 
     Preferably, the reagent pad faces vertically downward during provision of the part of the sample. Herein, “vertically downward” comprises positions in which a plane through (thus parallel with) the pad makes an angle between zero and 20 degrees with the horizontal, more preferably between zero and 10 degrees. Although somewhat larger angles are not excluded by the invention, gravity assists optimally when the reagent pad is as horizontal as possible. 
     The optical sensor device may be any sensor device able to detect optical radiation coming from the reagent pad. This may be radiation reflected from the reagent pad, transmitted by the reagent pad (and tape), or even emitted by the reagent pad such as fluorescence radiation. The wavelength of the detected radiation may be in the visual range, but also in the ultraviolet range or in the near-infrared range. The detector may be of any type, such as an optical camera. Since the details of the optical sensor are not relevant for the present invention, and the skilled person has easy access to numerous implementations of these sensors, no further details are deemed necessary to give here. 
     Particular embodiments of the present invention are described in the dependent claims, as well as, together with their features, advantages and effects, in the now following part of the description. 
     In particular, the milking system according to the invention is provided with said tape reel with said tape, preferably the tape reel being replaceable. 
     In embodiments, an optical path to the optical sensor passes upwardly through the base material of the tape during said detecting, and in particular during said supplying said part of the sample. Herein, the optical path to the sensor is the path that is followed by radiation from the reagent pad to the optical sensor. This may be a direct straight line in the simplest case, or a different path if use is made or mirrors, lenses or other optical elements, which, incidentally, may make the set-up more compact. In the present embodiments, the optical path will start upwardly at the reagent pad, and first go through the base material of the tape. This ensures that if a drop of the sample liquid would fall off the reagent pad, it will not fall in the direction of the sensor, but rather away from it, which will reduce the likelihood of such drops affecting measuring reliability and accuracy. 
     In principle, it is sufficient if the dosing device comprises a nozzle to supply the part of the sample. This may be done in the form of supplying one or more droplets of the sample liquid. If the nozzle is sufficiently close to the reagent pad, the latter will be contacted by the droplet, and will suck it into the reagent pad. This requires the nozzle to be (always) rather close to the reagent pads. In order to be more flexible in the design of the analysis device, in embodiments, the dosing device comprises a displaceable nozzle with a supply line for supplying a portion of the milk sample to the nozzle, the nozzle being arranged for supplying the part of the sample to the reagent pad, wherein the dosing device further comprises a nozzle mover that is arranged to move the displaceable nozzle towards and away from the tape under the control of the control unit. This allows to bring the nozzle as close to the reagent pad as desired, which helps in better controlling liquid supply. Not only is it now possible to use tapes and reagent pads of various thickness, but also liquids of varying viscosity and/or surface tension, or more generally of various droplet forming properties. In addition, allowing control of the nozzle position, by means of the control unit, also allows for correcting differences in tape position, such as caused by sagging and so on. Furthermore, it allows to perform other tasks without a need to move the tape, such as cleaning the nozzle. Moreover, it enables to supply a droplet in a position inbetween the reagent pad and the sensor, which in turn makes it possible to analyse the reagent pad without further having to move it. The latter further reduces the chance of surplus liquid falling off the reagent pad, by shocks or vibrations from moving the tape to a different position. 
     It may suffice in some embodiments if the sample causes a chemical reaction in the reagent pad that emits optical radiation. In such case, an optical radiation source is not required. In most cases, and in corresponding embodiments, it is advantageous to have an optical radiation source that is controlled by the control unit. This allows a good control over the optical radiation emitted onto the reagent pads, and thus also ensures a good accuracy when determining the presence or concentration of a substance based on optical properties of the reagent pad supplied with the sample. Such optical radiation sources may be one or more LEDs, (halogen) incandescent light bulbs, lasers and so on. These may be readily selected by the skilled person. 
     In embodiments, the dosing device comprises a pump that is controlled by the control unit and is arranged for pumping liquid through the supply line towards the nozzle. The pump helps in controlling the supply of the liquid, mostly milk, in the form of one or more droplets. Herein, it is advantageous that the pump has to work against the action of gravity, in that control over the drop is better. There is no, or at least a very much reduced, chance that liquid suddenly falls off the nozzle or otherwise onto the reagent pad, in an uncontrolled amount. The pump, which is preferably a metering pump such as a peristaltic pump, can then supply a volume of liquid in an even better controlled fashion. The pump is preferably further arranged for sucking back liquid from the nozzle. This allows liquid to be supplied in a very controlled way, in that for example a liquid drop is supplied such that it makes contact with the reagent pad, and is subsequently sucked back in order to break the contact between the droplet and the reagent pad. This enables further control over the liquid supply, and this may prove advantageous in particular in the case of reagent pad/liquid combinations that show a relatively slow transfer speed and/or capillary action, so that there is a relatively long time for controlling this liquid transfer. 
     In embodiments, the dosing device comprises an overflow device comprising a wall at least partly surrounding the nozzle, an overflow space being provided between the wall and the nozzle, further comprising a discharge connected or connectable to the overflow space. This allows surplus liquid to be collected in the overflow device. This is not only advantageous for collecting inadvertent surplus liquid. in order to prevent droplets from soiling the apparatus. It further allows deliberate flushing of the nozzle with liquid, even in place, without such risk of soiling the apparatus. The sampling and analysis device may e.g. be arranged to supply a cleaning portion of the sample before supplying the part of the sample proper. To do this, the nozzle is first brought in a position relatively remote from the reagent pad. This prevents accidental transfer of liquid to the reagent pad. Subsequently, the control unit arranges the sampling and analysis device, such as a pump thereof, to supply a first part of the sample, here called a cleaning portion, to the nozzle. This cleaning portion exerts a cleaning action on the nozzle, removing older sample liquid and/or dirt that may have remained or collected there, respectively. This cleaning portion is collected in the overflow device, and carried of via the discharged. After this cleaning action, the now clean nozzle may supply a part (droplet) of the sample for transfer to the reagent pad. If desired, The sampling and analysis device may alternatively or further be arranged to supply a separate cleaning fluid, such as water, optionally with a cleaning agent, to the nozzle. Again, this cleaning fluid may be collected in the overflow device, and drained via the discharge. In all these cases, it is advantageous that the supply of liquid, be it milk or other sample fluid, and/or cleaning fluid is against the direction of gravity, so that an optimum control over the flow of liquid may be exerted, and that cleaning may be performed without any further complications. 
     In embodiments, the milking system further comprises a dosing control device comprising a flat wall part, and a mover arranged to bring the flat wall part and the nozzle into sealing contact. This allows to fill the nozzle just to its rim, thereby repeatably defining a meniscus as the starting point for “growing a droplet” in a controlled fashion. the flat wall part serves as a lid for the nozzle, against which lid the liquid may be pushed to fill the nozzle completely. Herein, “sealing contact” is meant as “touching contact, without actually preventing fluid from escaping, as that might also include trapping air, which is disadvantageous. Surplus liquid may (thus) escape to the sides. What remains of the liquid forms a well-defined meniscus, which is the reference or starting point for the supply of a droplet of a well-controlled, predefined volume. Herein, a metering pump may serve to add an exactly known amount of liquid to that droplet, or better: to the meniscus, in order to form a droplet. 
     In embodiments, the wall part comprises a flexible material, in particular an elastic membrane. By means of the flexible material, tolerances in the nozzle surface may be accounted for, such that the “sealing contact” is achieved for substantially every nozzle surface. This also allows excess liquid to escape more easily between nozzle surface and the flat wall part. In addition, because the flat wall part is flexible, the counterforce exerted on the liquid is relatively small, and well-defined. All this further helps in the formation of a well-defined meniscus. Herein, “flexible” means that the flat wall part may undergo a detectable elastic deformation under the influence of the pressure of the liquid from the nozzle. The wall part is preferably an elastic membrane, such as in particular a rubber membrane. 
     In embodiments, the sampling and analysis device comprises a sealing rim arranged around the flat wall part, the sealing rim and the flat wall part together forming a second space for receiving the nozzle. This ensures that liquid that escapes between the flat wall part and the nozzle, and thus moves more or less to the side, is not ejected into the space of the sampling and analysis device, but may now (also) be collected in the second space, and e.g. drained. 
     In embodiments, the wall of the overflow device and the sealing rim are in sealing contact when the nozzle is received in the second space, the overflow space and the second space then being in direct fluid connection. This ensures that the draining of the ejected excess liquid may be via the drain of the overflow space. 
     In embodiments, the discharge has a cross-sectional discharge area that is at least twice as large as a cross-sectional supply area of the supply line. This ensures that the discharge of the collected liquid/excess liquid is substantially always possible with a low pressure/low vacuum, which helps in preventing draining problems, as well as prevents counterpressure on the liquid in the nozzle. Preferably, the discharge area is at least four times as large as said cross-sectional supply area of the supply line. Such a ratio ensures in almost all practical cases a sufficiently large counterpressure, and thus an even better control over the meniscus. 
     Importantly, many of the above described advantages are not limited to the use of the sampling and analysis device in a milking system. Rather, the ability to better control delivery or supply of a part of a sample to a reagent using gravity in the process may be used in substantially any liquid sampling and analysis system. Therefore, the present invention also provides a sampling and analysis device arranged to receive a sample of a liquid from a sample liquid line, and to analyse liquid from the sample, wherein the sampling and analysis device comprises a control unit for controlling the sampling and analysis device, a tape mover, arranged to move and unwind, under the control of the control device, a tape wound on a tape reel carrying the tape, said tape comprising a base material with provided thereon a series of reagent pads, that are arranged to provide a detectable response in the presence of at least one substance in the sample, a dosing device arranged to provide, under the control of the control unit, a part of the sample onto one of the reagent pads, an optical sensor device arranged to detect optical radiation from said reagent pad supplied with said part of the sample, and to analyse the detected optical radiation to provide an indication of a presence or concentration of said at least one substance, wherein during provision of the part of the sample the reagent pad is facing downward and away from the optical sensor. It is expressly noted that all the features of all dependent claims, as well as of all embodiments described for the milking system according to the invention are also applicable to the sampling and analysis device, with corresponding advantages. 
     It is furthermore expressly stated here that the advantages for the present invention, both for the milking system and for the sampling and analysis device, also apply to embodiments wherein the tape mover and the tape with the reagent pads have been replaced by a dry stick mover, arranged to move, under the control of the control device, a dry stick, said dry stick comprising a base material with provided thereon one or more reagent pads, that is/are arranged to provide a detectable response in the presence of at least one substance in the sample. Herein, the reagent pad(s) will be facing downward during sample supply. Thus, the invention also relates to a milking system, comprising a milking means for milking milk from a dairy animal, a milk line in fluid connection with the milking device, a sampling and analysis device arranged to take a sample of the milk from the milk line and to analyse milk from the sample, wherein the sampling and analysis device comprises a control unit for controlling the sampling and analysis device, a dry stick mover, arranged to move, under the control of the control device, a dry stick, said dry stick comprising a base material with provided thereon one or more reagent pads, that is/are arranged to provide a detectable response in the presence of at least one substance in the sample, a dosing device arranged to provide, under the control of the control unit, a part of the sample onto one of the reagent pads, an optical sensor device arranged to detect optical radiation from said reagent pad supplied with said part of the sample, and to analyse the detected optical radiation to provide an indication of a presence or concentration of said at least one substance, wherein during provision of the part of the sample the reagent pad is facing downward and away from the optical sensor. 
    
    
     
       The invention will now be elucidated by way of a number of exemplary embodiments and the drawings, in which 
         FIG. 1  shows a diagrammatic representation of a milking system according to the present invention; and 
         FIG. 2  diagrammatically shows a partly cross-sectional view through a part of an embodiment of the invention. 
     
    
    
       FIG. 1  shows a diagrammatic representation of a milking system  1  according to the present invention for milking teats  101  of an udder  100  of a dairy animal. The milking system  1  comprises teat cups  2 , connected to short milk lines  3 , debouching in a milk jar  4 , that in turn is connected to a main milk line  5 . A milk pump is denoted  6 , and a three-way valve with 7 connects to a bulk tank line  8  connected to a bulk milk tank  9 , and to a sewer line  10 . 
     A milking robot  11  has a robot arm  12  and a robot control unit  13 . A sampling unit is generally denoted  14 , and a sampling line  15  with an optional sample valve  16 . The sampling unit  14  comprises a supply reel  20  and a collecting reel  21  that is driven by a tape mover  22 , for positioning a tape  23  with reagent pads  24 . A nozzle device for sample droplets is denoted by  25 , a light source  26  emits light  27 , and a camera is denoted by  28 . 
     In use of the milking system  1 , the robot control unit  13  controls the milking robot  11  with the robot arm  12  to attach the teat cups  2  to the teats  101  of the udder  100  of a dairy animal such as a cow. The milk that is subsequently milked leaves the teat cups  2  under the influence of a vacuum, that is applied by a pump not depicted here, via the short milk lines  3 , and is collected in a milk jar  4 . 
     In order to comply with legal requirements, the first milk from each teat must be tested for physical changes, and if desired for other deviant properties. This can be done by means of a separate foremilk test device, or it can be done with the help of the sampling unit  14  as supplied according to the invention. Then use will be made of the alternative sample lines  15 ′. In case of a negative assessment, the milked milk collected in the milk jar  4  will then be pumped to the sewer line  10  by means of the milk pump  6 , via the main milk line  5  and the three way valve  7 . All these devices are under the control of the robot control unit  13 . Contrarily, if the milk is assessed to be of good quality, it will be pumped to the bulk milk tank  9  via the bulk line  8 . 
     It is also possible that the sampling unit  14  takes a sample from the milk jar  4 , in particular a mixed sample from milk that was milked from all teats and during all of the milking. This helps to get a good assessment of the milk that (if not rejected based on the foremilk assessment or otherwise, such as being antibiotics milk) will be sent to the bulk tank  9 , or possible to one of several bulk milk tanks. For example, the milk from different cows could be sent to different bulk tanks, based on their fat content, their protein content or otherwise, as determined by the sampling unit  14 . In such embodiments, as the one shown in  FIG. 1 , the sample line  15  runs from the milk jar  4  to the sampling unit  14 , and optionally has a sample valve  16 . Note that the latter could also be a part internal to the sampling unit  14 . 
     Most often, however, the sampling unit  14  is used to determine a property of the milk from a cow, either per teat quarter  101  or for the whole udder  100 /animal, which property is subsequently used in animal management but not for immediate control of the milk destiny. Examples are the measurement of hormones such as progesterone, that play a role in the reproductive cycle of the animal, or of substances that relate to feeding or metabolic health of the animal. Based on the assessment by the sampling unit  14 , the farmer or the control unit  13  may then adapt feeding, call a veterinary for a health check or for insemination, and so on. It is remarked that in robotic milking systems animal identification systems are present, so that animal ID during milking is known. Thereby, any measurement result will be coupled to the corresponding animal file in a database system. 
     Furthermore, a sampling unit  14  is very generally shown here, in that it contains a supply reel  20  and a collecting reel  21 , between which a tape  23  is advanced by means of tape mover means  22 , such as a cassette deck motor or stepper motor. The tape  23  carries reagent pads  24  that contain reagent that gives a detectable response in the presence of a defined substance, often the intensity of the response depending on the concentration of the substance brought into the reagent via the sample droplet. Such a sample droplet is delivered via the nozzle  25 . A light source  26  then shines light  27  onto the reagent pad  24 , and a camera  28  observes the response, if any, in the reagent pad. The light source  26  may be any suitable light source, such as one or more LEDs, and the emitted light  27  may be visible light, UV(A) radiation, (near) infrared, and so on, depending on the used reagent. Of course, the camera  28  should be adapted to detect radiation coming from the reagent pad  24 . Often, this is reflected or scattered light, but it could be different radiation, such as fluorescence radiation. In any case, details of such radiation and detection may easily be implemented by the skilled person and do not form the present invention as such. 
     In the embodiment shown, the sample droplet is supplied to the reagent pad  24  by the nozzle  25  from below. This allows gravity to support the control over the supplying of the sample droplet, instead of interfering with it when the sample droplet would be provided from above or from the side. More details of this will be provided in relation with  FIG. 2 . 
       FIG. 2  diagrammatically shows a partly cross-sectional view through a part of an embodiment of the invention. Herein, similar parts are given the same reference numerals, sometimes with a single or double prime (‘I’). 
     Here, the tape  23 ′ is provided with a series of reagent pads  24 ′ that have a bottom layer  29  and a top layer  30 . The nozzle  25 ′ is connected to the sample line  15 ″ with a sample pump  15   a , provides a sample droplet  37 , and is provided in, and surrounded by, an overflow cup  34 , which has an overflow space  35  with a drain  36  and is connected to a nozzle mover arm  38  that is moveable in the direction of the double arrow A. A rinsing cup  39  is moveable by means of a connected rinsing cup moving arm  40  in the direction of the double arrow B, and comprises a bottom  41  and a bellows  42 , and surrounds a rinsing space  43 . The camera  28 ′ has a field-of-view  31  with a line of main direction  32 . The light source  26 ′ comprises three LEDs  26 ′- 1  and shines in an solid angle with a line of main direction  33 , that makes an angle α with line  32 . 
     In use of the system, the droplet  37  is provided from below. This means that gravity in principle pulls back the droplet into the nozzle  25 ′, instead of pulling it out of said nozzle. This helps in controlling the forming and the ejection of the droplet  37 . It cannot suddenly drop off from the nozzle, due to some vibration or even mere coincidence. This ensures that the droplet cannot fall from the nozzle onto the camera  28 ′, that images the reagent pads  24 ′. Even if there would be excess liquid supplied to the reagent pad  24 ′, such liquid would not fall onto the camera, or on an optional window provided between the camera and the tape with the reagent pads. In this way, the camera  28 ′ will always have a clear picture of the reagent pads, even without such a window. In the Figure, the camera is tilted slightly to the left. The tilting of the optical path may also be brought about by means of a mirror or the like. 
     Having the sample drop supplied from below also allows an improved control over supplying of the droplet in that excess liquid may now easily be sucked off the reagent pad. Again, gravity helps, by preventing breaking off of the droplet from the nozzle, such that in principle there will remain a connection between the droplet, even when contacting the reagent pad, and the nozzle. In case the connection would be broken after all, that is a clear indication that substantially all liquid has been absorbed by the reagent pad, and thus there will neither be a problem with liquid later on falling off unexpectedly. Obviously, the type of sample pump or dosing pump  15   a  should allow such sucking back, e.g. a peristaltic pump with a reversible pump drive. 
     In a typical operation of the system, first the nozzle  25 ′ can be rinsed with fluid, to remove residues from previous sampling and/or to bring the nozzle to a desired temperature, by rinsing with correspondingly heated fluid. This may be done by supplying liquid via the sample pump  15   a  through the sample line  15 ″, and collecting the liquid emerging from the nozzle  25 ′ in the overflow cup  34  by means of gravity. However, it is advantageous if the liquid for rinsing is supplied more vigorously. This can be achieved by moving the nozzle somewhat away from the tape  23 ′ by operating the nozzle mover arm  38  by any suitable means such as pneumatics or an electromotor, and moving the rinsing cup  39  between the nozzle and the tape by operating the rinsing cup moving arm by, again, any suitable means such as an electromotor, followed by inserting the nozzle into the rinsing space  43 . In practice this will come down to inserting the nozzle  25 ′ together with the overflow cup  34  into the rinsing space  43 . However, if no overflow cup is provided, it is also possible to arrange the rinsing cup with such dimensions that it seals off the nozzle. A drain should then be provided in the rinsing cup  39 . 
     Preferably, when inserted, the nozzle  25 ′ with the overflow cup  34  is sealed by the bellows  42  of the rinsing cup  39 . Thereby, the overflow space  35  and the rinsing space  43  form one sealed off space. Now, rinsing fluid may be supplied to the nozzle  25 ′ with vigour, such as with 2 m/s. The liquid will then be ejected from the nozzle but remain within the overflow space/rinsing space  35 / 43 . From there, the fluid will be drained by means of the drain  36 . Finally, it will be ensured that the nozzle is completely filled with sample liquid, in particular milk, by pressing the nozzle  15 ″ against the bottom  41 , being a flat part, of the rinsing cup  39  and eject more liquid. The bottom  41  is somewhat elastic, and this ensures that there will be a clearly defined meniscus of sample liquid in the now completely filled, and air bubble-less nozzle. The nozzle arm  38  will then move the nozzle downward, out of the rinsing cup  39 , and the rinsing cup moving arm  40  will move the rinsing cup  39  to the side, to clear the way for the nozzle to reach the reagent pads. 
     Next, a dosing pump, in particular the sample pump  15   a , such as a peristaltic pump, may dose a known amount of sample fluid, to form the sample droplet  37  of now known dimensions. This helps in preventing excess fluid that may drop off unexpectedly, and also ensures that it will be known when the droplet  37  will touch the reagent pad  24 ″. The nozzle mover  38  will then move upward again to bring the droplet  37  to a reagent pad  24 ′, where a reaction and response may be brought about. 
     This reaction can be observed by the camera  28 ′, that looks straight down through the tape, with a field-of-view  31  with a central line  32 . This allows the camera  28 ′ to observe the reaction in the reagent pad  24 ′ from the opposite side with respect to the sample liquid supplied in the droplet  37 . This prevents that already coloured reagent material blocks the observation of further response in fresh reagent material, or that not yet absorbed sample liquid blocks the view altogether. This is particularly helpful in double layer reagent pads such as shown in the figure. Sometimes it takes a two-step reaction, such as in the case of flow-through tests. Herein, the present set-up with the double layer may provide an alternative to these flow-through tests or also lateral flow tests. Since these take more time, it is then advantageous when more than one reagent pad  24 ′ is in the field-of-view  31 , since the tape and thus each pad  24 ′ is advanced one pad length for every sampling, such as for every milking. Since the latter may be as short as five minutes, it is advantageous to allow more pads in the view of the camera  28 ′ to allow more time for observing the response. It is remarked that even with single layer reagent pads  24 ′, having more pads in view of the camera is useful, since then the concentration of the reagent in the pad  24 ′ may be less than would be needed if the response would have to be assessed in those five minutes. 
     It is remarked that the camera  28 ′ need not itself be positioned (directly or not) above the tape  23 ′, as long as the optical path (the “view”) of the camera  28 ′ is on the other side of the tape  23 ′ as where the reagent pads  24 ′ are. In other words, the camera should look through the tape. The physical position of the camera  28 ′ may be changed e.g. by using mirrors or the like. These may e.g. be used to fold up the optical path, and make the analyser device more compact. 
     The light source  26 ′ used in the present embodiment comprises three LEDs  26 ′- 1 . These can be white light LEDs that together shine a homogeneous but bright light, in a main direction  33  that makes a sharp angle α with the line  32  of the camera&#39;s field-of-view, in order to prevent blurring or glaring of the camera image. The light source may also comprise other types, such as a combination of red, green and blue LEDs, halogen incandescent and so on. The light emitted may be visible light, near infrared, ultraviolet (UVA) or the like. The tape  23 ′ should of course be transparent for the light used. 
     The above described embodiments only serve to help explain the invention without limiting this in any way. The scope of the invention is rather determined by the appended claims.