EP1194744A1

EP1194744A1 - A device and a method for monitoring a vacuum supply pulsator device

Info

Publication number: EP1194744A1
Application number: EP00937473A
Authority: EP
Inventors: Martin SJÖLUND
Original assignee: DeLaval Holding AB
Current assignee: DeLaval Holding AB
Priority date: 1999-06-03
Filing date: 2000-05-29
Publication date: 2002-04-10
Also published as: SE9902047L; AU5264200A; WO2000075610A1; SE516601C2; SE9902047D0

Abstract

A method for monitoring a pulsating flow, the pulsation activated by a pulsation source (1) having a predetermined frequency, at a supervision position a distance away from the pulsation source (1) wherein the steps of indicating a varying signal (100, 101) at said supervision position based on the flow during a time dependent on a pulse identification for the flow, analysing said varying signal (100, 101) regarding its frequency content to identify at least one frequency region, determining at least one value of the amplitude of said signal obtained at said analysis, and comparing, either directly or by means of an algorithm, said obtained value with at least one calculated limit and/or one adaptive limit of a normal operating flow amplitude value.

Description

WO 00/75610 ^L PCT/SEOO/01101

A device and a method for monitoring a vacuum supply pulsator device

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method, in accordance with the preamble of claim 1, for monitoring a vacuum supply pulsator device and an apparatus, according to the preamble of claim 9, for perforating said method.

When milking dairy -uiimals with milking machinery a teat cup can be attached to each of the teats of the animals udder. The teat cup is connected by a flexible hose to a flow regulator on a milk meter which is connected to a milk line leading to a milk storage container. Milk is extracted from the animal by an underpressure in the system which is produced by a high capacity vacuum pump. The underpressure in each teatcup is controlled by a diaphragm in the flow regulator which is subjected to a control underpressure or "vacuum" on one side and which is subjected to a supply underpressure on the other side.

Known vacuum pulsator devices used in milking systems for milking an animal, e.g. a cow, suffers from the disadvantage that they do not include any satisfactory supervision of the flow of milk from the udder of the animal into a vacuum milkingline system. Generally they only include sensor means in, or near to the pulsator itself, either at the inlet or the outlet of the pulsator, which consequently implies that if an error occurs in the milking line itself, no warning or malfunction signal is given, since the pulsator sensor only senses whether it exists a vacuum or underpressure close to the pulsator.

The flow regulator diaphragm has sensing contacts which complete an electrical circuit when the diaphragm is moved into contact with the lid of the control chamber by a pressure in the product chamber which is sufficiently greater than the underpressure in the control chamber. This can occur if a teat cup is removed from a teat. This increases the pressure in the product chamber, causes the diaphragm to make the electrical circuit and thereby operate a valve to connect the control chamber to atmospheric pressure. This cause the diaphragm to close off the product chamber outlet for a predetermined time to allow the milker to refit the teat cup. Thus the diaphragm acts as an automatic switch which can close the outlet in the event of a teatcup being knocked off a teat.

The device according to known technique can only react to a considerable pressure difference which occurs, for example, if a teat cup is completely removed from a teat. There is however a need for means for detecting if a teat cup is leaking or if the air inlets in a teat cup are blocked. It is furthermore desirable to have means which can detemiine the flow rate through the regulator.

Furthermore a minor malfunction, for example, a small leakage of the vacuum milking supply line, which will go un-detected, may incur significant economical cost, due to reduced yield from the animal and furthermore may cause injury to the animal.

Infections of the udder of the animal can also be a result of an undetected malfunction as described above. Another problem, according to known technique, is that it is difficult to detect whether there has been a clogging of air holes in the nύlking line, causing an alteration in the flow of milk. This problem can potentially incur, when automatic milking devices are used, since no attendant is operating the -r-ilking procedure, significant economical costs and ineffectiveness.

It is, accordingly, an object of the present invention to overcome the disadvantages of the known devices and methods.

An other object of the invention is to provide a method and an apparatus for monitoring if a small leakage occurs in a vacuum flow supply line.

In the flow regulator device according to the present invention a contactless proximity sensor is provided which generates a signal proportional to the distance between a movable diaphragm and a fixed point on the flow regulator. This makes it possible to measure the distance between the diaphragm and the outlet of the regulator and, if desired, to estimate the fluid flow in the regulator.

SUMMARY OF THE INVENTION

This has been solved by a method as defined in the introduction, which is characterized by indicating a periodic deviation or changes of the flow during an arbitrary time. This variation will further on also be called a varying signal. The method is furthermore characterized by analysing the varying signal regarding its frequency content to identify at least one frequency region, detem-ining at least one value of the amplitude of the signal obtained at the analysis, and comparing, either directly or by means of an algorithm, the obtained value with at least one calculated limit of a normal operating flow amplitude value. The value can also be compared with an adaptive value, provided during the normal operating flow of milk.

In this way, a supervision of the pulsation source and the flow of fluid can be achieved, which enables the determination of an eventual alteration in the normal operating flow of fluid. That is, a sensor measuring the flow of milk will receive a signal comprised of: an average flow + the periodic deviation due to a pulsation created by the pulsation source + a measurement noise. By filtering the sensor signal, the periodical deviation or, as a term used in this application, the varying signal can be analysed regarding its frequency content as described above.

Preferably, the analysing is performed using high pass or band pass filtering a measuring signal before indicating the varying signal. In this way the varying signal can be provided before analysing it.

Suitably, the analysing is performed using Fourier analysis. In this way the amplitude of the filtered varying signal can be obtained. Preferably, the analysing is made by means of an adaptive filter. In this way the amplitude of the filtered varying signal can be obtained.

Suitably, a malfunction signal is produced if the value of the amplitude of the signal decreases below said at least one calculated limit of a normal operating flow amplitude value. In this way a malfunction signal is produced if a difference in the quantity of the flow occur, by means of a change in the pulsation of flow.

Preferably, a warning signal is produced if said value for a number of sequence measurement cycles has a tendency to go towards one of said at least one calculated limit of a normal operating flow amplitude value. In this way a warning signal could indicate a starting malfunction.

Suitably, said analysing described above is performed according to the operating frequency of the pulsation source. In this way the at least one frequency region can be analysed. It is thereby possible to adapt the impulse identification dependent on the frequency of the pulsation source. The frequency of the signal is typically 0,8-1,0 Hz.

Preferably, the varying signal, is produced by means of a sensor means adapted to sense said flow of fluid. Subsequently the varying signal can be fed to a function supervision means for the impulse identification. The supervision means is designed to analyse the varying signal provided from said sensor and to identify at least one frequency region and create an amplitude value to be compared with at least one calculated limit of a normal flow amplitude value. An important feature of the invention and an advantage of this arrangement is that said sensor means simultaneously can be used to measure the flow of fluid by integrating a value produced by means of said sensor means over time.

The mentioned objects have furthermore been solved by an apparatus as defined in the introduction, which is characterized in that the function supervision means is adapted to analyse a varying signal provided from said sensor means based on the flow of a fluid, software is provided in said function supervision means designed to analyse the frequency content in said varying signal to identify at least one frequency region and create an amplitude value to be compared to at least one calculated limit value for a normal flow value. In this way the flow of fluid can be analysed and at least one calculated limit value for a normal flow amplitude value can be compared with the actual flow amplitude value in at least one frequency region. Thereby it is possible to monitor the flow and the pulsation source, due to the variance and the changes of the flow amplitude.

Preferably, software is provided in said function supervision means designed to signal a malfunction signal if an amplitude value of the analysed varying signal, in at least one frequency region, decreases below at least one calculated limit of a normal flow amplitude value. Subsequently, if the flow amplitude value of the analysed varying signal decreases below said at least one calculated value, an alarm or error signal is produced by means of a supervision means, designed to create this alarm signal.

Suitably, software is provided in said function supervision means designed to signal a warning signal if an amplitude value of the analysed varying signal for a number of sequence measurements cycles has a tendency to go towards one of said at least one calculated limit of a normal operating flow amplitude value. Subsequently, if the flow amplitude values of the analysed varying signal have a tendency to go towards the calculated limit, that means that a malfunction is being near by hand, a warning signal can be produced by means of a supervision means, designed to create this warning signal.

Preferably, the sensor means comprises a first position sensor adapted to sense the position or the relative position per time interval of a diaphragm plate and it is simultaneously adapted to sense a first varying signal included in the measuring signal. Thereby said first position sensor may be used to feed said varying signal to said function supervision means simultaneously with using said first position sensor measuring the flow of fluid. Suitably, the sensor means comprises a second position sensor adapted to sense the position or the relative position per unit of time of a scale weighing plate arranged in a weighing means for determining the quantity of fluid leaving said flow sensing device per unit of time and said second position sensor is simultaneously adapted to sense a second varying signal of the flow of fluid. Hereby the second position sensor may be used to feed said varying signal to said function supervision means simultaneously with using said second position sensor measuring the flow of fluid.

Preferably, the apparatus for performing an animal related operation having a function supervision means comprising at least one monitoring device, for controlling the pulsation source. In this way a monitoring function is achieved for an animal related operation, for example an automatic milking device.

The word comprising can in this application, if needed, be replaced by the word including. The word fluid may of course, when using milking machines, mean the word milk.

DRAWING SUMMARY

The invention will now be described more closely by means of examples of embodiments with reference to the accompanying drawings, in which

Figure 1 illustrates a monitoring device according to a first embodiment of the invention and

Figure 2 illustrates a monitoring device according to a second embodiment of the invention.

Figure 3a)-3c) shows a cross-section through a sensing device in accordance with the present invention. DETAILED DESCRIPTION OF THE INVENTION

Referring to figure 1 a supervision device comprises a pulsation source, such as a pulsator 1, provided with an inlet vacuum supply line 2 and two outlet vacuum supply lines 4, which each via a T-connection divides into two supply lines each connectable to separate teat cups 3, i.e. to the flexible air chamber 3a of each teat cups. In figure 1 the connections of only one particular teat cup are schematically illustrated. Each teat cup is individually connected to a similar system.

The pulsator 1 is connected to an exciter set 6. The frequency of the pulsator may be, for example, 1 Hz. A sensor means 5 is arranged on said inlet vacuum supply line 2, for monitoring whether there is a vacuum or not.

A first vacuum milking supply 7 line is connectable to said teat cup 3 and to a milk flow regulator device 9. Additionally a second vacuum milking supply line 16 is connectable from said milk flow regulating device 9 to a vacuum separator 18, creating the depression.

A diaphragm plate 9a is arranged in said milk flow regulator device 9 for regulating the flow of milk. Lifting of the plate 9a is made possible by means of a vacuum line 14, causing depression. The flow of milk is consequently controlled by means of the pressure difference between both sides of the diaphragm plate 9a.

The milk flow regulator device 9 is, by means of modem technique, provided with a first position sensor 11 which output is fed to a control unit 15. The control unit 15 is commonly used to indicate by means of the diaphragm plate 9a, for example, if the teat cup has been fallen of the teat of the animal, since the plate 9a will be lifted in an upper position, due to the vacuum in the vacuum line 14. However, as realised by the inventor of this application, it is possible to use said position sensor 11 to indicate the speed of the milk. However, it is also possible to have the instant position as an output and provide the speed indication by a sampling rate.

Thus, according to prior usage, the sensor means 11 indicates, by means of the control unit 15, a successful fitting "on the teat" of the teat cup, that is the plate will fall from top to bottom and likewise a successful removal "off the teat", that is the plate will go up to a top position. The top position can also indicate that said teat cup 3 has fallen of a teat.

The present invention makes use of the design that the signal from the sensor means comprises a first varying signal 100, based on the output signal of said sensor 11, is fed to a function supervision means 13. The output signal is substantially arranged for signalling the position and/or speed of said diaphragm plate 9a, as been described above.

Said position sensor 11 may, for example, be a linear potentiometer or a linear inductive contactless sensor.

The function supervision means 13 analyses the varying signal by means of an impulse identification, for example by filtering it, such as by a high pass or a band pass filter and/or by making a frequency analysis or an adaptive filter analysis to identify at least one frequency region.

A value will then be determined of the amplitude of said impulse of the signal obtained by the analysis. This value could be compared with at least one calculated limit of a normal operating flow amplitude value.

Using the Fourier analysis, said at least one limit may, for example, be obtained by means of a predetermined empirical value, and when using a neural filter the at least one limit may be obtained automatically. Said function supervision means 13 is adapted to signal a malfunction signal 110 if the value of the amplitude of said filtered varying signal impulse decreases below the calculated limit of normal operating flow amplitude value. Said malfunction signal 110 may, for example, be used to cause a shutdown of the pulsator 1. The shut down may be done automatically and furthermore it is also or alternatively possible to alarm service personnel by means of a mobile telephone e.t.c. The signal 110 can have different characters depending upon different kinds of malfunctions.

Figure 2 shows an example of a second embodiment of the invention, in which parts denoted with a reference sign correspond to parts of the first embodiment with the same reference sign.

A second position sensor 12 sensing the movement of a weighing plate 10a, provided in a weighing means 10. Said sensor 12 sense the position or the position per unit of time of said weighing plate 10a. The main task for said second position sensor 12 is to make it possible to determine the quantity of milk per unit of time, i.e. the flow rate of fluid. Its output is therefore sent to a calculating device 12a making the calculation of the milk flow and/or quantity.

Said position sensor 12 may, for example, be a linear potentiometer or a linear inductive contactless sensor.

In the supervision device, according to the second embodiment of the invention a second varying signal 101, based on the output signal of said second position sensor 12, is fed to a function supervision means 13', according to this embodiment. The output signal of the second position sensor 12 is, as been described above, also substantially arranged for signalling the position or/and speed of a scale weighing plate 10a installed in said weighing means 10, according to known technique.

The second varying signal 101 is analysed in the same way as the signal 100, described in the embodiment of figure 1, and a value is determined by means of an impulse identification. The second embodiment implies, consequently, that the function supervision means 13 is adapted to signal a second malfunction signal 111. The signal 111 can have different characters depending upon different kinds of malfunctions.

The analysis could also identify a trend of decreasing amplitudes in a number of frequency regions. This trend could be used for detecting a starting malfunction as well. That means that the trend, by means of modern technique, could be analysed for providing a warning signal 112. The warning signal 112 may, for example, indicate a starting malfunction, but wherein a shutdown of said vacuum supply pulsator is not necessary. The signal 112 can have different characters depending upon different kinds of malfunctions. Of course, the warning signal 112 can be provided as in the first described embodiment as well.

The solid arrows in figure 1 and 2 show the direction of the vacuum flow and the dashed arrows show the direction of the electrical signals. It is to be noted that a combination could be provided of the features accordingly to the invention shown in both figures 1 and 2, such that a combined function supervision means 13, 13' is provided with varying signals from both the position sensors 11 and 12. The supervision means could then provide a complex arsenal of warning signals useful for the control of the milking system.

The weighing means 10 may, for example, comprise at least one light emitting diode (not shown) for measuring the flow of milk and sensing the status of the flow. This diode (not shown) may be used in the same way as the sensors 11, 12 described above. It means, that the light emitting diode may be used for feeding a measuring signal to the function supervision means 13, 13', which measuring signal can be filtered for providing a varying signal (not shown) and, for example, analysing it regarding its frequency region. Measuring the phase of the pulsation for all cups simultaneously will give a relative measurement between the cups. If this relationship not is in order an alarm or error signal can be provided from the function supervision means 13.

During use an underpressure is present in the device, which underpressure is provided by a high capacity vacuum source 18.

As can be seen in figure 3 a) flow regulator 9 comprises a control chamber 119 connected via an outlet 121 to vacuum line 112 and separated from a product chamber 123 by a flexible diaphragm 9a. The vacuum line 112 maintains a desired reference pressure Pref in the control chamber 119. Product chamber 123 has an inlet 127 connected to line 7 and an outlet 129 connected to the vacuum source 18 via the milk meter and milk pipe (not shown for reasons of clarity). Vacuum source 18 subjects the product chamber to a working underpressure Pwork. When Pref and Pwork are the same the diaphragm takes up the neutral position N (shown in figure 3a).

If there is a pressure difference Pdiff between Pref and Pwork then the diaphragm is moved out of the neutral position N towards the chamber with the lowest pressure. If Pwork is less than Pref the diaphragm is moved from the neutral position N to a position N' shown in figure 3b) where it is closer to the outlet 129. This reduces the outlet flow area between the mouth of the outlet and the diaphragm and causes an increase in Pwork. This causes the diaphragm to move back towards the neutral position N until an equilibrium position is reached. If Pwork is greater than Pref the diaphragm is moved from the neutral position N to a position N" shown in figure 3c) where it is further away from the outlet 129. This increases the outlet flow area between the mouth of the outlet and the diaphragm and causes an decrease in Pwork. This causes the diaphragm to move back towards the neutral position N until an equilibrium position is reached. In this way the working pressure is maintained at the reference value set in the control chamber 119. Flow regulator 9 has a proximity sensing means 131 comprising a target sensing means 133 preferably fixedly mounted on or in control chamber 119 and a target 135 fixed to diaphragm 9a on the side of the diaphragm facing the control chamber 119. Target sensing means 133 and target 135 are preferably so mounted in order to prevent them being contaminated by the milk in the "wet" product chamber 123. Target sensing means 133 is preferably mounted on the lid of control chamber 119 as far away as possible from the diaphragm 125 in order to achieve the greatest possible range of measurements.

In this embodiment target sensing means 133 is a Hall-effect sensor which produces an signal S proportional to the distance between it and the target 135 which is a magnet. Any other sensing system which produces a signal proportional to the distance between the target and the target sensing means can be used, e.g. systems based on potentiometers, photocells or other opto-electrical means, capacitance or the like.

The signal S can be processed in a control means 137 which, for example, can deteπnine the distance between the outlet 129 and diaphragm 9a. This distance can be compared to reference values stored in a memory or shown on a gauge to determine if there is leakage in the system. The comparison can also detect if the air inlet 139 in the teat cup 3 is blocked.

The measured distance between the outlet 129 and the diaphragm 9a can also be used in a method to calculate the area of the flow path between the outlet 129 and the diaphragm 9a. The effective area of the flow path is equal to a value related to the circumference of the outlet multiplied by the outlet height between the outlet and the diaphragm. The flow through the area depends on the pressure in the system and the flow for different pressures can be determined by experimentation. As the working pressure Pwork is the same as Pref which is known it is therefore possible to calculate the flow volume through the outlet and hence to measure the quantity of milk passing through the regulator. In a further embodiment the position sensing means comprises a strain gauge means attached to flexible diaphragm and which measure the strain in the diaphragm as it moves from an end position close to the outlet to a second end position close to the control chamber.

OPERATION

During a normal milking procedure the sensor means sense, by means of a control unit 15, the position of the diaphragm plate 9a for regulating the flow of milk through the regulating device 9, where the plate 9a is lifted and lowed by means of a balancing vacuum supply 14. By means of said control unit 15 the sensor means 11 indicates a successful fitting "on the teat" of the teat cup, that is the plate will fall from top to bottom and likewise a successful removal "off the teat", that is the plate will go up to a top position. The top position can also indicate that a teat cup has fallen of a teat.

The sensor means used according to known technique, as been described above, can sense a major malfunction, but it can not sense if dirt, a smaller leakage, or other minor malfunctions arise in the milking line or the teat cup. For example, the rubber wall in the teat cup between vacuum supply line from the pulsator and the milking line inside the teat cup may be frayed or damaged. This can not be detected with prior known techniques.

Since the milking line 7 is a free-standing component, a malfunction here was earlier undetectable. That is the pulsator 1, which creates the impulse, does not co-operate with the milking line. Since the sensor 5, mounted on the pulsator, did not sense the impulse of the pulsator, the malfunction could earlier not be detected. That means, that using known techniques, a feed-back could not be established.

In the case of a malfunction, for example a small leakage on the milking line, there will be some milk flow from the udder of the animal, but at a reduced rate. By means of the invention this malfunction can be detected and harm the animal, such as infection etc, can be avoided, i.e. by analysing said varying signal 100, 101 of the sensor 11, 12 and particularly indicating the impulse in this signal emanating from the pulsator 1.

Thus, the varying signal 100, 101 is based on the flow during a time dependent on a pulse identification time for the flow. This varying signal 100, 101 is analysed regarding its frequency content to identify at least one frequency region. Furthermore a value of the amplitude of the signal obtained at the analysis is deteπnined and is compared, either directly or by means of an algorithm, with at least one calculated limit of a normal operating flow amplitude value. The varying signal 100, 101 is filtered by means of high band pass filtering and thereafter a Fourier analysis or a 2 to 4 pole selectivity adaptive control is made for analysing the filtered signal.

According to the invention a malfunction signal 110, 111 is provided if the value of the amplitude of said impulse decreases below the at least one calculated limit of a normal operating flow amplitude value. This signal can be fed, for example, to a mobile telephone and/or an alarm indicating device and/or a control unit for controlling the milking flow.

A warning signal 112 is provided if the value for a number of sequence measurements cycles has a tendency to go towards one of the at least one calculated limit of a normal operating flow amplitude value. This signal can be fed as been described above.

Of course it is possible to operate the pulsator using another frequency than one impulse per second. In the invention the frequency analysis is preferably made in the region of the frequency of the pulsator. That is, if the pulsator frequency is 1Hz, the analysis identifies the frequency region of 1 Hz. The value of the amplitude of this frequency region can be compared with a calculated amplitude value for a normal operating flow.

If a malfunction is detected, then an alarm could be signalled to operating personnel, at the same time as the pulsator could be shut down automatically and the cow released. The invention could also be used to detect filled air holes in the ntilking lines. For making a smooth flow of milk, the milking lines have small holes, according to known technique. If a hole would be filled, the milk flow will be effected. A device and a method according to the invention makes it possible to detect such possible clogging the air hole.

Even though the invention was developed for milking machines the device according to the invention is applicable to other applications where monitoring devices for controlling a pulsating flow of fluid of a vacuum supply system are used.

Claims

1. A method for monitoring a pulsating flow, the pulsation activated by a pulsation source (1) having a predetermined frequency, at a supervision position a distance away from the pulsation source (1), characterized by the steps of

-indicating a varying signal (100, 101) at said supervision position based on the flow during a time dependent on a pulse identification for the flow,

-analysing said varying signal (100, 101) regarding its frequency content to identify at least one frequency region, -determining at least one value of the amplitude of said signal obtained at said analysis, and

- comparing, either directly or by means of an algorithm, said obtained value with at least one calculated limit and/or one adaptive limit of a normal operating flow amplitude value.

2. A method according to claim 1, wherein the further step of high pass or band pass filtering a measuring signal (99) in order to indicate said varying signal (100, 101).

3. A method according to claim 1, wherein said analysing is performed by means of Fourier analysis.

4. A method according to claim 1, wherein the analysing is performed by means of an adaptive filter.

5. A method according to any one of the preceding claims, wherein providing a malfunction signal (110, 111) if said value of the amplitude of said signal decreases below said at least one calculated limit of a normal operating flow amplitude value.

6. A method according to any one of the preceding claims, comprising the step of providing a warning signal (112) if said value for a number of sequence measurements cycles has a tendency to go towards one of said at least one calculated limit of a normal operating flow amplitude value.

7. A method according to any one of the preceding claims, wherein said analysing is adapted to the operating frequency of said pulsation source (1).

8. A method according to any one of the preceding claims, comprising the step of providing said varying signal (100, 101) by means of a sensor means (11, 12) adapted to sense said flow of fluid.

9. A monitoring device for controlling a pulsation source (1), which by its action provides a pulsation to a fluid in a fluid supply line (7) connectable to a flow sensing device (9) comprising a diaphragm plate (9a) sensing the flow of fluid in said fluid supply line (7), sensor means (11, 12) adapted to sense the flow of fluid, a function supervision means (13, 13') associated with said sensor means (11, 12), characterized in that

-said function supervision means (13, 13') is adapted to analyse a varying signal (100, 101) provided from said sensor means (11, 12) based on the flow of fluid, and -software provided in said function supervision means (13, 13') designed to analyse the frequency content in said varying signal to identify at least one frequency region and create an amplitude value to be compared to at least one calculated limit of a normal flow amplitude value.

10. A monitoring device according to claim 9, wherein software is provided in said function supervision means (13, 13') designed to raise a malfunction signal (110, 111) if an amplitude value of said analysed varying signal (100, 101) in at least one frequency region decreases below at least one calculated limit of a normal flow amplitude value.

11. A monitoring device according to claim 9, wherein software is provided in said function supervision means (13, 13') designed to signal a warning signal (112) if an amplitude value of the analysed varying signal (100, 101) for a number of sequence measurements cycles has a tendency to go towards one of said at least one calculated limit of a normal operating flow amplitude value.

12. A monitoring device according to anyone of claims 9-11, wherein said flow sensing device (9) comprises a control chamber (119) separated by a fluid-tight flexible diaphragm (9a) from a product chamber (123) wherein the control chamber (119) is subjected to a reference pressure (Pref) and the product chamber (123) is subjected to a working pressure (Pwork) and wherein the diaphragm (9a) and the device are provided with co-operating target means (135) and target sensing means (133) wherein said target sensing means (133) produce an output signal (S) proportional to the distance between said target means (135) and said target sensing means (133).

13. A monitoring device according to claim 12, wherein said target means (135) is attached to said diaphragm (9a).

14. A monitoring device according to claim 12, wherein said target sensing means (133) is attached to said diaphragm (9a).

15. A monitoring device according to claim 12-14, wherein said target means (133) is a magnet and said target sensing means (135) is a Hall-effect sensor.

16. A momtoring device according to claim 12-14, wherein said co-operating target means (135) and target sensing means (133) are opto-electrical devices.

17. A momtoring device according to claim 12-14, wherein said co-operating target means (135) and target sensing means (133) are resistive devices.

18. A monitoring device according to claim 12-14, wherein said co-operating target means (135) and target sensing means (133) are capacitive devices.

19. A momtoring device according to claim 12-14, wherein said co-operating target means (135) and target sensing means (133) are inductive devices.

20. A monitoring device, wherein said flow sensing device (9) comprising a control chamber (119) separated by a fluid-tight flexible diaphragm (9a) from a product chamber (123) wherein the control chamber (119) is subjected to a reference pressure (Pref) and the product chamber (123) is subjected to a working pressure (Pwork) characterised in that said diaphragm (9a) is provided with strain-gauge means which produce an output signal (S) proportional to the distance between said diaphragm (9a) and said control chamber (119).

21. A monitoring device according to claims 9-11, wherein said sensor means comprises a first position sensor (11) adapted to sense the position or the relative position per time interval of said diaphragm plate (9a) and simultaneously adapted to sense a first varying signal (100) included in said measuring signal (99).

22. A monitoring device according to claims 9-11, wherein said sensor means comprises a second position sensor (12) adapted to sense the position or the relative position per unit of time of a scale weighing plate (10a) arranged in a weighing means (10) for determining the quantity of fluid leaving said flow sensing device (9) per unit of time by means of a calculating device (12a) and said second position (12) sensor is simultaneously adapted to sense a second varying signal (101) of the flow of fluid.

23. An apparatus for performing an animal related operation comprising at least one monitoring device according to any one of the preceding claims for controlling said pulsation source (1).