FLUID SENSING APPARATUS

TECHNICAL FIELD

This invention relates to a method and apparatus for sensing fluids.

BACKGROUND ART

The present invention concerns the detection of particles within a fluid. While fluid flow in most embodiments of the present invention will be a liquid, it is possible that the present invention can also relate to particulate matter in which it is desirable to detect the presence of larger particles. It is envisaged that in most cases however, the present invention will relate to the detection of solids within a liquid.

Particular reference will now be made to the use of the present in the detection of mastitis of milk through determining the presence of clots within the milk. However, this should not be seen as limiting.

Mastitis is a significant problem to be managed by any dairy industry. The udder infections which cause mastitis result in significant loss of income to dairy farmers through the degradation of milk quality, in addition to adding costs for identifying, isolating and treating dairy animals with mastitis.

Clinical mastitis can be identified through the presence of solid clumps, clots or flocculant masses present in the milk produced by an animal. Such clots are readily apparent to the naked eye if mastitic milk is run over a dark smooth surface. However, it is not practical for dairy farmers to strip milk from every udder section of every dairy animal in their herd to detect mastitis problems.

Most milking equipment includes a filter element, generally known as "milk sock", mounted inside a common collection line prior to this line being connected to a milk collection vat or tank. The milk sock consists of a filter or straining element which

catches solid contaminants, such as grass, dirt or mastitic clots within milk delivered by all animals currently being milked.

The presence of mastitic milk clots within or on the milk sock will therefore indicate to a dairy farmer that at least one of their herd has a mastitis problem. However, the dairy farmer will need to in turn inspect each and every animal in their herd to identify which animal has mastitis.

Normal particle counting systems do not work in this situation. This is for at least the following reasons

• The first and most important is that milk is such a highly turbid medium. That is it is full of protein micelles and fat globules.

These interfere with normal particle counting systems. That is the signal that would detect the clots is swamped due to the presence of the fat and protein

• Cost. The dairy shed is a low cost environment. Systems that may be able to detect clots would be far too expensive for dairy farming

• Reliability. The dairy shed has vibration, dust, dirt, high pressure water, cows kicking etc. Delicate systems that may be able to detect clots cannot work reliable in this environment.

• A two phase environment. This makes detection between air bubbles and clots difficult.

One attempt to address this issue is disclosed in US Patent No. 4376053. This patent describes the provision of a filter in the common milk line provided for a single milking station or cup cluster. Such physical filters can be used to detect the

presence of mastitis in a single identified animal as opposed to over the entire herd, as would be the case with inspection of the milk sock as described above.

However, such physical filters need to be manually inspected either during or immediately after the milking of a single animal. This again results in additional time consuming tasks which have to be performed for each animal by a dairy farmer during a milking session. Furthermore, such physical filters can impede milk flows through the long milk line of a single milking station, and can be installed at positions which are difficult for a dairy farmer to access easily and quickly.

It would therefore be of advantage to have a mastitis determination method and apparatus which addressed any or all of the above problems. In particular, a mastitis detection method and apparatus which could automatically indicate the presence of a mastitis problem in a single animal

It would also be an advantage if they provided a method by which contaminants could be detected in other fluids. This could include for example, particles within a crude oil flow such as sand, undissolved components within dyeing agents, particulate matter (grapes, seeds, skin and wines) in wine and dissolved additives within reconstituted drinks.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not

constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF INVENTION

Accordingly to an aspect of the present invention there is provided a method of determining the presence of a discrete anomaly within a fluid,

characterised by the steps of

a) causing fluid to flow past a transducer, and

b) receiving at least one transducer signal which varies with respect to a property of the fluid in the presence of the transducer,

c) determining a quiescent state of the transducer signal, and

d) indicating the presence of a particular discrete anomaly if the transducer signal varies significantly with respect to the quiescent state.

According to yet another aspect of the present invention there is provided a fluid sensing apparatus configured to indicate the presence of a discrete anomaly in a

fluid flow, said apparatus including:

at least one transducer positioned relative to a fluid flow,

the transducer configured to receive a signal which varies with respect to a property of the fluid flowing in the presence of the transducer, and

a property detection element configured to receive at least one transducer signal, and

an indicator element configured to indicate the presence of a discrete anomaly if a change is detected in fluid flow property varies significantly with respect to the quiescent state of the transducer signal.

According to another aspect of the present invention there is provided a set of computer executable instructions which operates the steps of

a) receiving a transducer signal which varies with respect to a property of the fluid flowing in the presence of the transducer, and

b) determining a quiescent state of the transducer signal, and

c) indicating the presence of a particular discrete anomaly if the transducer signal varies significantly with respect to the quiescent state.

The discrete anomaly may be any body or contaminant which is desired to measure in the fluid flow. For example, the anomaly may be undissolved additives, grape seeds, grape skin, sand and so forth. The anomaly may alternatively be of lower density or colour than the fluid surrounding it, for example, entrained air bubbles. In a preferred embodiment of the present invention, the anomaly is a milk clot.

The fluid may be any flowing matter and could include gas, liquid, and particulate

masses such as sand or powder. In some embodiments, the fluid may be of the same general composition as the anomaly it is desired to detect. For example, in preferred embodiments the fluid is milk with the mass being milk clots. However, this should not be seen as limiting as the present invention could be used to determine unwanted contaminants within a fluid flow which have quite a different composition to that fluid.

Reference should now be made to the use of the present invention in relation to determining the presence in mastitic milk in a milk flow.

However it should be appreciated that the present invention does have broader implications as described above.

Further, when the present invention is applied to milk flow, it could be used to determine the presence of masses other than milk clots or indicator of mastitic milk.

Thus the transducer and/or property detection elements may vary according to the property being detected.

It should also be appreciated that in some embodiments the transducer and property detection element are the same component.

It is envisaged that in most embodiments of the present invention the property of the milk that is being measured is optical in nature.

For example, the property being measured may be the absorption or transmission of light in a particular frequency.

For example, a photo diode may be used as the transducer with the photo diode operating in the near infrared range (NIR).

In other embodiments, light at the other end of the spectrum (say blue visible light) may be used.

It should be appreciated that there is a significant advantage to using optical properties as this is a non-invasive way for determining fluid property in comparison to other methods.

However it should be appreciated that the transducer may be looking at another change of property or density, for example mass density or conductivity. With air bubbles, there will be a decrease in density.

The term quiescent state of the transducer signal refers to the normal background signal received by the transducer in the absence of any masses desired to be detected.

Using milk as an example, the milk composition varies considerably during the process of milking with different ratios of fat, water, and protein. However, these variations occur over a period of seconds (or even minutes) during the process of milking. These variations do not represent an event such as a mass (say a mastitic clot) passing a transducer. Such an event leads to a significant change in the signal received from the quiescent signal in terms of the frequency of the event detected and the size or amplitude of the signal.

Thus, it is an important aspect of the present invention to recognise that the signal must be differentiated to distinguish from normal variations in fluid composition passing the transducer (quiescent state) so as to recognise the presence of a mass flowing past the transducer.

Differentiation of the signal over the quiescent state is discussed in greater detail in this specification.

The present invention is adapted to provide a methodology and also preferably an apparatus used to determine the presence of mastitic milk in a milk flow. In particular the present invention may be adapted for installation or use within milking equipment to detect such mastitis problems in real time in relation to a single identified dairy animal.

Reference throughout this specification will be made to the present invention being used in conjunction with a milk flow travelling within the long milk line of a single milking station. The provision of the present invention in or association with such a location allows for a determination to be made as to the presence of mastitis in the single dairy animal currently being milked at the milking station. However, those skilled in the art should appreciate that the present invention may be used in conjunction with other locations associated with milking machinery or milk processing equipment in general, and reference to the present invention being used in conjunction with the long milk line of a single milking station should in no way be seen as limiting.

For example, one embodiment of the present invention may be used with respect to a holding tank which has been adapted to cause fluid flow past a transducer configured to operate in accordance with the present invention.

References to the determination of mastitis throughout this specification will also be made in relation to a determination as to the presence of clinical mastitis with respect to a particular dairy animal. Clinical mastitis results in symptoms which include clots or flakes of solid matter being expressed in the milk of an animal.

Reference throughout this specification will also be made to the present invention being used to detect the presence of mastitic milk clots in milk flows. However

those skilled in the art should appreciate that the present invention may also be used to detect the presence of other forms of solids or particulate materials within a milk flow or even entrained gas bubbles, any of which can immediately change the current density of the milk flow.

The present invention may be implemented through a mastitis determination apparatus which includes at least one transducer. Such a transducer or transducers may be located within or adjacent to a milk flow to allow the milk flow to influence the operation of the transducer's signal. Preferably the transducer selected may produce a signal which varies with respect to the optical properties of milk flowing past the transducer.

The present invention may be employed in conjunction with such flows to monitor the milk flow at the point at which a transducer or transducers are employed. The present invention is employed in conjunction with dynamic milk flows to ensure that the transducer signal will vary so that a rate of change can be determined or a high frequency transducer signal component may be isolated. In effect, the dynamic nature of the milk flow provides a characteristic required for the present invention to function effectively.

In a preferred embodiment a transducer as used in conjunction with the present invention may operate through receiving a reference signal transmitted through the milk flow which has been modified by the characteristics of the milk flow. In such embodiments the transducer or transducers provided need not necessarily extend out to any conduit which carries the milk flow, therefore preventing the present invention from impeding milk flows. The ability to measure non-invasively in food industry systems such as milking machines is of significant advantage - both in terms of efficiency and hygiene.

In a preferred embodiment the present invention may include at least one optical

transducer configured to receive a beam of light transmitted across a milk flow. Optical transducers can be used to measure the absorbance of light transmitted through a milk flow, where the absorbance measured is directly related to the composition of the milk flow. In such embodiments an optical transducer such as a photodiode can receive an incident light beam and subsequently provide an electrical signal which varies in relation to the composition of the milk flow.

In such embodiments the transducer or transducers employed may provide a signal which varies with respect to the composition of the milk currently in the presence of the transducer. Those skilled in the art should appreciate that the clots or masses to be detected in conjunction with the present invention are more optically dense than a normal flow of milk - leading to greater absorption of the signal.

Reference throughout this specification will also be made to a transducer used in conjunction with the present invention being provided by a photodiode or any other similar form of optical transducer. However, those skilled in the art should appreciate that other forms of transducer assemblies or systems may also be employed in conjunction with the present invention, and reference to the above only throughout this specification should in no way be seen as limiting.

For example, in one alternative embodiment a transducer may be provided through a voltage divider circuit with the centre tap between the divider resistances providing an output transducer signal voltage. The resistances of the divider can be located within a milk flow so that mastitic milk clots which collide with the upstream resistance modify the overall balance of resistances within the divider.

Any incident milk clot will therefore cause a change in voltage at the centre tap of the divider, in turn giving a transducer signal which varies in accordance with the overall density of the milk flow.

Reference in general throughout this specification will also be made to the transducer or transducers used having signals which vary with respect to the composition of milk in the presence of the transducer.

In yet another alternative embodiment a transducer may be provided through a capacitive plate arrangement with the plates of the capacitor formed being located on either side of a conduit used to carry the milk flow. The capacitance of such an arrangement may be measured, with variations present in same being attributed to the varying density of the milk flow.

Reference throughout this specification will also be made to the present invention including a single transducer only which provides a single transducer signal. However, those skilled in the art should appreciate that multiple transducers may be provided and used in required and reference to the above only throughout this specification should in no way be seen as limiting.

Preferably the mastitis determination apparatus provided also includes an optical detection element which receives the transducer signal. Such a density detection element may be employed to detect changes in the optical characteristics of the milk flow.

In a further preferred embodiment an optical detection element may be configured to assess the rate of change of a transducer signal. As transducer signals are selected so as to vary with the optical characteristics of the milk flow, a sudden change in such signals can indicate that at least one or potentially more mastitic milk clots have flowed passed the transducer.

Reference throughout this specification will also be made to the optical detection element differentiating over the quiescent state of a transducer signal. However those skilled in the art should appreciate that instantaneous rates of change will be

affected by the speed at which transducer signals can be received and sampled or assessed. Such rate change values can be used to indicate the presence of a mastitic clot irrespective of any average or overall biasing characteristics associated with the milk flow. For example, the composition of a milk flow may vary over time with seasonal variations being present due to environmental factors.

Thus, a signal indicating the presence of a mass may be differentiated from the quiescent signal through the use of a high pass filter. Such a high pass filter can remove signals which vary over a long period of time (for example as a result of generic change in milk composition) while detecting signals that represent a significant change in composition over a short period of time (say a mass).

The frequency of the high pass filter will naturally vary according to the flow rate of fluid past the transducer, the nature of the quiescent signal and the composition of the mass (whether optical, size or shape) desired to be detected. However, in a typical milking system the flow rate of milk past the transducer is expected to be in the order of 1 to 1.5 meters per second. Given the nature of mastitic clot flows, a high pass filter frequency of 20 Hz is sufficient to allow for a signal corresponding to mastitic masses to pass as opposed to the background (quiescent) signal.

In a further preferred embodiment an optical detection element may use the transducer signals to provide an integer count of the number of mastitic masses which have flowed past the transducer over a measurement period.

In a preferred embodiment a density detection element may be implemented through a comparator circuit which drives or triggers a counter component. A comparator may be readily assembled using well known electrical components to compare received transducer signals with a quiescent signal in real time. An associated digital counter may be provided in a further preferred embodiment which is triggered by a comparator. Such a counter can maintain and increment a

count of mastitic masses detected over a fixed or known measurement period. The count provided can give an indication as to the severity of any mastitis problem through to determining the rate at which mastitic clots are detected.

In a preferred embodiment the density detection element may be configured to assess or isolate at least one high frequency signal component from a transducer signal. Such high frequency signal components are indicative of elevated rates of change in the transducer signal. By isolating such high frequency components the density detection element may readily determine whether the rate of change of a transducer signal exceeds the quiescent signal.

For example, in a further preferred embodiment where a photodiode transducer is employed the electrical transducer signal it supplies may be filtered to investigate the amplitude of any high frequency signal components. If such signal components exceeds a quiescent signal value (say amplitude), then a determination can be made that a mastitic clot is in the vicinity of the transducer.

Preferably the mastitis determination apparatus provided may also include an indicator element configured to indicate the presence of mastitic milk. Preferably such an indicator element may be activated once changes in the composition of the milk flow have been detected at a level high enough to assume that at least one mastitic milk clot has flowed passed the transducer.

In a further preferred embodiment an indicator element may be triggered when a set number of mastitic milk clots have been detected within a fixed period of time. Those skilled in the art should appreciate that this clot count rate may be varied depending on the applications in which the present invention is used to detect either severe or early stage clinical mastitis.

In a preferred embodiment the present invention may be associated with a

sampling chamber well located within the conduit in which the milk flow travels. Preferably such a well may be provided through the technology disclosed in New Zealand Patent No. 519133 which can allow for the settling or dispersal of entrained air from milk. Entrained air bubbles can cause false positive readings through periodically and rapidly changing the current density of a milk flow. By employing a well based sampling chamber in conjunction with the present invention the error producing effects of entrain air may be mitigated.

Further differentiation may be employed in the present invention to remove the effect of air bubbles. This may be in addition to or instead of using a sampling system as described above. For example, in a substantially streamed flow, the air bubbles tend to appear at a substantially constant rate according to a normalised curve. The inventor has found that the count rate of bubbles above a certain threshold is less per minute than that found for mastitic milk. Therefore, if a count is found in a certain range, then that can be attributed to air bubbles. Counts significantly above that range can therefore be attributed to mastitic milk instead.

Alternatively, as mentioned earlier the air bubbles may be specifically detected in some applications of the present invention.

The present invention may provide many potential advantages over the prior art clinical mastitis detection systems.

The present invention may be used to indicate that the presence of clinical mastitis has been determined in conjunction with a single dairy animal. Such an indication may be used in a range of applications ranging from diverting the milk produced by the animal away from a common collection vat, through to directing the animal involved to a holding area or pen for subsequent veterinarian treatment.

The invention may be used to activate an audible or visual alarm system which

alerts a dairy farmer to the detection of mastitis in relation to a particular animal. Those skilled in the art should appreciate that the indications of mastitis provided by the invention may be used in a range of applications.

The invention may readily detect the presence of mastitic milk clots through considering the current density of a milk flow. By detecting that the density of such flows has sharply increased at a point in time, this can indicate the presence of a clot. Furthermore, by tracking the rate or number of clots which are detected over a fixed measurement time, an assessment can be made as to the severity of the clinical mastitis problem of a single dairy animal.

It should be appreciated that the present invention also offers many advantages in relation to the generic sensing of anomalies within a fluid flow. In particular the present invention has advantages with regard to single and two phase fluid flow which often has air entrained in liquid. Contaminants can be readily sensed without interrupting the flow of fluid, not only that there is contamination but also the amount of contamination can be readily detected as well. Various control systems can be implemented as a consequence whether an alarm or diversion of the contaminated fluid.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

Figure 1 illustrates a schematic diagram of portions of an optically based mastitis determination apparatus provided in accordance with a preferred embodiment, and

Figures 2a, 2b illustrate an electrical transducer based mastitis

determination apparatus provided in accordance with an alternative embodiment.

Figure 3 illustrates graphical results for clots in water

Figure 4 illustrates graphical results for non clotty milk (Blue and green) and clotty milk (black) run through sensor.

BEST MODES FOR CARRYING OUT THE INVENTION

Figure 1 illustrates a schematic diagram of portions of an optically based mastitis determination apparatus provided in accordance with a preferred embodiment.

The apparatus shown includes a transducer, which is provided in this embodiment by a photodiode (1). The photodiode (1) is configured to receive a modulated light signal transmitted from LED (2). Light from the LED (2) is transmitted across a conduit carrying a milk flow to the photodiode (1). The LED (2) is driven or powered by a 35 kHz oscillator signal which applies a modulation to the light transmitted.

The output of the photodiode (1) is fed through to a current to voltage conversion amplifier (4) which converts the current pulses of the diode into a proportional voltage signal. This voltage signal is supplied to a 35 kHz band pass filter used to remove the effect of ambient light in the signal received by the photodiode (1).

A diode (6) and low pass filter (7) are then provided to demodulate the signal, providing a DC voltage proportional to the amount of light transmitted through the milk flow.

Finally, a high pass filter removes the DC offset component from the signal

resulting in a high frequency signal component only which is directly indicative of the detection of rapid changes in density of the milk flow. This high frequency signal component can in turn be further filtered by a low pass filter (5) to remove any additional noise components prior to supply to a further comparator and counter element (not shown).

As can be seen from figure 1 neither of the photodiode (1) or LED (2) need to be located within a milk flow. Furthermore, the arrangement of filters which receive the output of the photodiode (1) can remove ambient light noise effects and provide an output signal which clearly indicates when a rapid change in density has been detected.

Figures 2a, 2b illustrate an electrical transducer based mastitis determination apparatus provided in accordance with an alternative embodiment.

In particular figure 2a illustrates conditions where a voltage divider transducer does not have a clot present and when a clot is present. As can be seen from the left hand case the transducer output signal provided by the centre tap is expected to sit at half the input voltage as the two resistors are balanced.

Conversely, when a clot hits the upstream resistance, the resistances become unbalanced, resulting in a variation in the output voltage provided at the centre tap.

Figure 2b illustrates elements of a optical detection element provided when the electrical impedance transducer discussed with respect to figure 2a is used.

In this embodiment the voltage divider circuit is driven by a 30 kHz oscillator. The centre tap of the divider provides the output transducer signal which is in turn demodulated. Lastly a high pass filter is provided to amplify the changes made, and then a low pass filter is provided to smooth out any noise effects. The final output signal provided consists of an indication of the high frequency components

of the signal showing when rapid changes in density of the milk flow have been detected.

The results for above system are illustrated below in Figure 3 with the clot count being the y axis. When plastic in water is flushed through it clearly detects these, as the clot count rises from 0 to about 300.

When flushing real milk through the sensor the output is very low, and clotty milk the output is much higher. Figure 4 illustrates results from running real milk through the sensor in the laboratory. The x axis is again time, and the y axis clot count. The lines at the bottom of the graph are clean and clot free milk. The upper line is clotty milk run through the sensor. Clearly there is a significant difference between the two types of milk.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.