EP2984461A1

EP2984461A1 - Magnetostrictive level probe with integrated quality sensor

Info

Publication number: EP2984461A1
Application number: EP14722757.3A
Authority: EP
Inventors: Lorenzo Caligaris
Original assignee: Start Italiana SRL
Current assignee: Start Italiana SRL
Priority date: 2013-04-08
Filing date: 2014-04-04
Publication date: 2016-02-17
Also published as: WO2014167471A1; ITTO20130280A1

Abstract

Magnetostrictive level probe (1) to determine at least one level (h) of at least one fluid (f) contained in a tank (C). The probe (1) comprises a rod (3), which extends along an axis (k); at least one mobile float (4), which can slide along said axis (k); at least one magnet (40), which is associated with each one of said at least one float (4); a probe body (2), which is fixed close to an end of said rod (3) and comprises at least one electronic circuit (20) that is at least adapted to determine the position of said float (4) in the direction of said axis (k); at least one guide (5), for guiding a high-frequency electric impulse generated by said circuit (20), and at least one first housing structure (32), which longitudinally extends along the direction of said axis (k) and houses a guide (5). The probe comprises at least one second housing structure (60), which extends along the direction of said axis (k) and comprises at least one fluid quality sensor (7), arranged in said second housing structure (60) and electrically connected to said at least one electronic circuit (20). The quality sensor (7) is adapted to measure the density, viscosity and dielectric constant of the fluid content, the quality and/or composition of which are to be determined.

Description

MAGNETOSTRICTIVE LEVEL PROBE WITH INTEGRATED QUALITY

SENSOR

The present invention relates to a magnetostrictive level probe comprising a sensor for detecting the quality of a fluid contained in a tank, the level of which is to be measured. Said level probe, when placed into a tank, can monitor, preferably in real time, the variations in the level of the fluid contained in said tank as well as the composition and/or quality of the fluid contained in the same tank.

In particular, said level probe is a magnetostrictive probe, which utilizes a physical principle called Wiedemann effect to determine the level of the fluid contained in said tank.

Level probes are known which comprise a rod extending along a longitudinal axis, on which at least one float can slide and change its position depending on the level of a fluid contained in a tank or container.

Such probes comprise at least one electronic circuit adapted to determine the position of the float along said rod, for the purpose of determining the level of the fluid contained in the tank.

Typically such probes are of the magnetostrictive type and can determine, with low uncertainty and high resolution, the position of the float along said rod.

Normally such probes are equipped with an electronic circuit comprising a processing unit, which electronic circuit is enclosed in a metal casing, normally referred to as probe body or head, arranged at one end of said rod. Said rod is made of non-magnetic material containing a guide made of ferromagnetic material. A permanent magnet is inserted within the float.

In measurement applications for fuel-containing tanks or reservoirs, such level probes may comprise a float for detecting the level of the fuel contained in the tank and another float, adapted to float on water, for detecting the level of the water on the bottom of the tank.

Such magnetostrictive probes, when placed into a tank, are normally connected to an outer control unit by means of connection cables. Such connection cables transport data to and from the probe, and are also adapted to supply power to the electronic devices included in the probe itself.

Periodically, at regular intervals, the outer control unit interrogates the level probe and receives data from said probe. This probe interrogation is useful to be able to accurately monitor the tank fluid filling and draining operations. Said probe is also used in order to detect any fluid leakage from said tank.

In those applications wherein the fluid contained in the tanks is a fuel, said probe is also used in order to detect any anomalous or unauthorized taking or discharge of fuel through non-authorized channels.

Moreover, the need is felt to be able to constantly monitor over time the quality and typology of the fluid contained in the tank. Monitoring the fluid quality and composition allows detecting any anomalous variations due to undesired contamination or infiltration.

The content of the same container is normally monitored by verifying the characteristics of the fluid contained therein, in order to evaluate the fluid typology and/or quality thereof. Normally this verification/measurement is carried out by means of a separate sensor arranged within an outer casing. Said sensor is an electronic fluid quality sensor adapted to generate an electric signal depending on the quality and/or composition of the fluid.

The verification of the typology and/or quality of the fluid does not take place in real time, but only when said electronic fluid quality sensor is immersed into the fluid.

In order to obtain a correct analysis of the fluid contained in the tank, the data thus obtained must then be processed also on the basis of the data obtained from other sensors placed into the liquid.

Magnetostrictive level probes are also known, from United States patent application US2013008247A1, wherein a fluid density sensor is comprised at one end of the probe rod. Said quality sensor is a float countered by a spring. Based on the movement of said float, a processing circuit can, through suitable computation algorithms, determine the density and, through further empirical calculations, estimate the quality of the fluid contained in the tank.

Quality is determined by using just one parameter, i.e. density, which is normally measured by means of a float countered by a spring.

Density sensors are also known which can determine the fluid density by means of a frequency-tunable fork sensor. Such a sensor is a separated sensor that comprises a processing system for determining the density of the fluid in which it is immersed.

The present invention aims at solving the above- mentioned problems by providing a level probe, comprising at least one quality sensor, which is not affected by the aforementioned drawbacks, and which can reduce uncertainty and increase resolution in the determination of the quality and/or composition of the fluid.

One aspect of the present invention relates to a level probe having the features set out in the appended independent claim 1.

Auxiliary features of the probe are set out in the appended dependent claims.

The features and advantages of the probe according to the present invention will become clear and apparent from the following description of at least one embodiment of the level probe and from the annexed drawings, wherein:

• Figures 1A and IB show, in a side view, the two embodiments of the level probe according to the present invention;

· Figures 2A and 2B illustrate the first embodiment shown in Figure 1A, wherein Figure 2A is a transparent side view of the probe and Figure 2B is a sectional top view (2B-2B) of the rod of Figure 2A;

• Figures 3A and 3B illustrate the second embodiment shown in Figure IB, wherein Figure 3A is a transparent side view of the probe and Figure 3B is a sectional top view (3B-3B) of the rod of Figure 3A;

• Figures 4A and 4B show the rods in the two embodiments, wherein Figure 4A is a sectional side view (4A-4A) of the rod of Figure 2B and Figure 4B is a sectional side view (4B-4B) of the rod of Figure 3B;

• Figure 5 shows a three-dimensional graph for determining the typology and/or quality of the fluid;

• Figures 6A and 6B schematically show the mechanical and electrical interconnections of the probe; in particular, Figure 6A shows the physical interconnection between the probe and a central control unit when the same probe is placed into a tank; Figure 6B shows the electric connections between the electric devices comprised in the level probe of the present invention and the same central control unit;

• Figures 7A and 7B respectively show a non- limiting embodiment of the resonant fork and the non- limiting equivalent circuit of the fork of Figure 7A, electrically connected to a generator and to an amplifier for transmitting the signals to a processing circuit.

With reference to the above-mentioned drawings, level probe 1, of the magnetostrictive type, is adapted to determine at least one level "h" of at least one fluid "f" contained in a tank "C", as shown by way of example in Figure 6A.

Level probe 1 comprises: a rod 3, which longitudinally extends along an axis "k"; at least one mobile float 4, which can slide along the direction of said axis "k".

At least magnet 40 is associated with each mobile float 4, it being preferably comprised in the same float 4, more preferably incorporated therein. An embodiment not shown in the drawings comprises a first float, adapted to float on fluids such as fuels, and a second float, adapted to float on water.

Said probe 1 comprises a probe body 2, which is fixed close to a first end 31' of said rod 3.

Said probe body 2 comprises at least one electronic circuit 20, which is at least adapted to determine the position of said at least one float 4 in the direction of said axis "k".

Said probe body 2 is preferably fixed to one end of rod 3. More preferably, said probe body is fixed to the upper end, or first end, 31' of rod 3 in the operating configuration of probe 1, as clearly visible in Figures 1A, IB, 2A, 3A and 6A.

For the purposes of the present invention, in the probe's operating configuration shown, for example, in Figure 6A, the lower end or second end 31" of rod 3 is meant to be that end which will be immersed first into fluid "f", whereas the upper end or first end 31' of rod 3 is meant to be that end which will not be totally immersed into fluid "f", being opposite to the lower end or second end 31" of rod 3.

Said probe further comprises: at least one guide 5, for guiding a high-frequency electric impulse generated by said circuit 20; and at least one first housing structure 32, which longitudinally extends along the direction of said axis "k" and houses said at least one guide 5.

For the purposes of the present description, the direction of an axis is meant to be a bundle of straight lines parallel to or coinciding with said axis.

In general, as shown by way of example in Figure 6B, each one of said at least one electronic circuit 20 comprises at least one impulse generator 202, adapted to generate said electric impulse, and at least one receiver 203, adapted to detect the vibration or acoustic wave generated by the magnetostrictive effect of guide 5, and at least one data processing unit 201, adapted to process the data obtained from the measurement in order to determine the position of said at least one float 4 along the direction of axis "k". In particular, the measurement of level "h" will depend on the time elapsed between the transmission of the electric impulse along guide 5 by said at least one generator 202 and the reception of the vibration or acoustic wave, generated by the same guide 5, by said at least one receiver 203.

The operation of electronic circuit 20 for determining the position of said at least one float 4 through the magnetostrictive effect will not be described any further herein because it is known to the man skilled in the art.

The level probe according to the present invention comprises: at least one second housing structure 60, which longitudinally extends along the direction of said axis "k"; and at least one fluid quality sensor 7.

Said at least one quality sensor 7 is arranged in said second housing structure 60. Said quality sensor is held in position by a support element 61.

Said at least one fluid quality sensor 7 is electrically connected to said at least one electric circuit 20. The electric connection is ensured by a connection line, e.g. passing through said support element 61.

Preferably, said quality sensor 7 is adapted to measure the density, viscosity and dielectric constant of the fluid, e.g. contained in tank "C", the quality and/or composition of which are to be determined.

In the preferred embodiment, said quality sensor 7 is a single sensor. Preferably, said single sensor 7 is obtained by means of a tunable fork resonator 70.

For the purposes of the present description, the term "tunable fork" refers to a fork capable of resonating at different frequencies within a known frequency range.

Said fork 70 is adapted to vibrate, in resonance conditions, at a frequency that depends on fluid "f" in which said fork is immersed. When fluid "f" in which the fork is immersed changes, the resonance frequency of the fork will change as well.

Figure 7A shows a non-limiting exemplary embodiment of a fork 70 comprising two prongs 71 which can vibrate, resonating at the resonance frequency.

Said prongs 71 are fixed to the ends of a fixed contact portion. For example, said fork resonator 70 is made of piezoelectric material capable of supplying an electric signal which is proportional to the resonance frequency at which prongs 71 vibrate.

The resonance frequency of the fork resonator can be determined by means of the following formula:

Where :

· "f" is the vibration frequency of the fork prongs ;

• "1.875" is the minimum positive solution of the function cos ( x ) cosh ( x ) = -1

• "1" is the length of the prongs in metres;

· "E" is the Young's modulus of the fork's material ;

• "I" is the second area moment of the cross- section in metres raised to the 4th power;

• "p" is the density of the fluid in which the fork is immersed, expressed in kg/m³.

Figure 7B shows, by way of non-limiting example, an equivalent circuit 73 which can normally be associated with a fork resonator. In particular, equivalent circuit 73 shown herein is a band-pass resonant circuit that comprises a first series resonant circuit and a parallel resonant circuit. Said series resonant circuit is an RLC circuit comprising a series capacity "C_s" , a series resistance "Rs" and an inductance "L", connected in series to one another.

Said parallel resonant circuit is an RLC circuit comprising a parallel capacity "C_p", a parallel resistance "R_p" and an inductance "L". As shown in Figure 7B, inductance "L" is common to both circuits.

The values of the components included in equivalent circuit 31 vary depending on the mechanical and physical characteristics of both the fork and fluid "f" in which the fork is immersed.

As can be seen in Figure 7B, an amplifier circuit 74 is preferably connected downstream of equivalent circuit 73. Said amplifier circuit 74 is electrically connected to fork 70. Said amplifier circuit 74 is adapted to amplify the signal to be transmitted to a data processing circuit and to remove any noise therefrom. One possible embodiment of said amplifier circuit 74 is, for example, an operational amplifier.

As shown in Figure 7B, an electric generator 72 is preferably connected upstream of equivalent circuit 73. Said generator is electrically connected to fork 70.

Said electric generator 72 is, for example, a frequency generator, e.g. an astable oscillator or multivibrator.

Said electric generator 72 is adapted to supply at least one electric signal to fork 70, which will start to oscillate (vibrate) at a certain frequency depending on the characteristics of the fluid in which fork 70 is immersed. From the resonance of prongs 71 of fork 70 one can determine the density, viscosity and dielectric constant of fluid "f". The present description will not illustrate in detail the principle of operation of the fork resonator used for determining the density, viscosity and dielectric constant of fluid "f", in that it is known, for example, from patent application US20030041653.

The use of a probe comprising a fork-type quality sensor 7 allows complying with the safety electric specifications relating to, in this specific case, combustible fluids "f". It also allows using just one sensor for determining three fundamental characteristic parameters of a fluid.

Said quality sensor 7 is preferably arranged within an outer casing 76, as shown in the annexed drawings.

Casing 76 is preferably made of plastic material suitably treated in accordance with the specifications.

Said outer casing 76 allows sensor 7 to be immersed into fluid "f" for effecting the measurement. The same outer casing 76 prevents access to the same sensor 7 from the outside, so that it cannot be tampered with.

In general, probe body 2 is preferably made of metallic material, appropriately treated to comply with the above-mentioned safety regulations.

Said probe body 2, preferably cylindrical in shape, is rigidly and sealingly secured at its lower end to rod 3, e.g. it is screwed to the latter by means of a sealed thread. At its upper end, said probe body 2 comprises a top closing element 25, e.g. a cover, fitted with fastening means, preferably screws, or said closing element 25 is screwed to probe body 2 by means of sealed threaded portions .

Electronic circuit 20 and the other electronic devices comprised in probe body 2 are held in a predetermined position by a plurality of retaining elements, which also act as dampers for the vibrations caused, for example, by shocks undergone by the probe itself, which might otherwise cause probe 1 to malfunction or the electronic devices included in probe body 2 to break. Preferably, said support element 61 for holding quality sensor 7 in position within the second housing structure 60 is mechanically connected to said retaining elements comprised in the probe body.

Said electronic circuit 20 comprises at least one data processing unit 201 adapted to process the data coming from guide 5. Said at least one data processing unit 201 is adapted to process the data coming from said at least one quality sensor 7.

Preferably, electronic circuit 20 comprises a single data processing unit 201 for processing both the data coming from guide 5 and the data coming from said at least one quality sensor 7.

In general, said at least one data processing unit 201 can process data coming from said quality sensor 7 for the purpose of determining, in real time, the quality and/or composition of fluid "f" contained in tank "C".

In particular, said at least one data processing unit 201 can determine, as a function of the frequency at which said at least one fork 70 oscillates (vibrates) in resonance conditions, at least one triad of values. Said triad of values includes, for example, the density, the viscosity and the dielectric constant of fluid "f" in which fork 70 is immersed.

Said data processing unit 201 is adapted to execute a computer program, suitably stored in a non-volatile memory medium. Said computer program, executed by data processing unit 201, can obtain said triad of values through suitable computational algorithms, based on the frequency at which said fork 70 vibrates (oscillates) in resonance conditions.

More in detail, said electric circuit 20 comprises at least one non-volatile memory medium 22.

Said at least one memory medium 22 stores at least one at least three-dimensional database.

For the purposes of the present description, the term "at least three-dimensional database" refers to a database, e.g. an at least three-dimensional matrix of memory locations, which can handle at least three independent parameters for data storage.

Said at least three-dimensional database associates at least one datum or result with each triad of values determined by the data processing unit 201. Said datum or result relates, for example, to the quality and/or composition of the fluid on which sensor 7 has carried out the measurements.

Preferably, said datum or result is univocal in relation to the fluid composition.

In some embodiments not illustrated herein, said database may have more than three dimensions, associated with as many parameters.

Said three-dimensional database is graphically represented in Figure 5, wherein a predetermined fluid is associated with each triad of values of density, viscosity and dielectric constant. In the cases illustrated herein, the fluids are combustible fluids, preferably in the liquid state .

Preferably, probe 1 comprises at least one temperature sensor 75, which is electrically connected to said electronic circuit 20, in particular to said data processing unit 201. Said at least one temperature sensor is arranged in proximity to said quality sensor 7. Preferably, a single temperature sensor 75 is used. Said at least one temperature sensor 75 is preferably arranged within an outer casing 76.

In cooperation with quality sensor 7, temperature sensor 75 allows determining the quality and/or composition of fluid "f" contained in tank "C" with better precision.

The use of a further parameter for determining the quality and/or composition of fluid "f" allows to reduce even further any uncertainty about the quality and/or composition of fluid "f". As temperature changes, in fact, some fluids may vary their own density and/or viscosity and/or dielectric constant.

In this embodiment, it may be necessary to implement a four-dimensional database, the added fourth parameter being temperature .

In general, as shown in Figures 6A and 6B, the data obtained from probe 1 and then more or less processed in accordance with the present invention are preferably transmitted, e.g. via a data line 81, to a central control unit 8. Said control unit 8 is preferably external to probe 1 and external to tank "C". Said control unit 8 is preferably arranged in a place easily accessible to the inspection personnel, preferably remotely from probe 1.

Normally said central control unit 8 comprises a device for displaying and storing the data received from the probe.

Said line 81 is an electric cable for data transmission, or a wireless line using radio waves. Said line 81 is used for transmitting the data relating to the level and/or quality of fluid "f", obtained through the measurements carried out by the probe. In addition, said line 81 is also used for transmitting the data through which control unit 8 interrogates said probe 1 in order to enable it to carry out at least one measurement of the level and/or quality and/or composition of fluid "f" contained in tank "C".

Said line 81 is preferably connected to probe 1 according to the present invention through at least one connector 811, which is preferably located at the top of probe body 2.

Data transmission is preferably serial, e.g. according to the RS485 protocol.

In general, during an operating step of inserting probe 1 into tank "C", said probe 1 is so arranged that longitudinal axis "k" of rod 3 is perpendicular to the surface of fluid "f" contained in tank "C".

During an operating step of taking measurements, e.g. measurements of the level and/or quality and/or composition of fluid "f", control unit 8 interrogates probe 1 and enables it to carry out one or more measurements, e.g. of the level and/or quality and/or composition of fluid "f". Circuit 20 processes, through said data processing unit 201, the data obtained by means of one or more measurements and transmits such data to control unit 8.

Said probe body 2 comprises at least one electric charge accumulation device 21, preferably a battery, adapted to ensure power supply to said electronic circuit 20 in the event of an electric blackout, e.g. if line 81 connecting it to said central control unit 8 is interrupted, or if power is removed from unit 8, so that control unit 8 can no longer interrogate probe 1 at regular intervals . Preferably, electronic circuit 20 comprises a recharging device (not shown), which is adapted to recharge accumulation device 21 when there is a power signal to probe 1, e.g. in the presence of connection line 81 between probe 1 and outer control unit 8.

In general, said at least one non-volatile memory medium 22 also stores the data processed by said data processing unit 201 of circuit 20, e.g. in chronological order .

When all the data stored have been correctly transferred to external unit 8, the contents of the memory locations of medium 22 occupied by the processed data can be deleted, so that they can be reused right away for saving new measurement data, e.g. in the event that the line 81 connecting the probe to external unit 8 is lost or that the same unit 8 no longer interrogates the probe for taking measurements.

Describing more in detail the implementation of level probe 1, in a first embodiment thereof said rod 3 is obtained through cooperation between the first housing structure 32 and the second housing structure 60. In the present embodiment, said at least one float 4 is assembled and arranged in a manner such that it can slide along said housing structures (32, 60) . In the present embodiment, said at least one float 4 utilizes said housing structures (32, 60) as guides on which it can slide.

Figures 1A, 2A, 3A and 4A illustrate, by way of non- limiting example, a probe 1 according to said first embodiment .

As can be seen in the above-mentioned drawings, said housing structures (32, 60) are arranged parallel to each other, properly spaced apart, and are kept in position by a fixing portion 30. Said fixing portion 30 is preferably located at the first end 31' of rod 3.

Said fixing portion 30 is in turn fixed to probe body 2. Each one of said housing structures (32, 60) is made from drawn plastic or metallic material, preferably nonmagnetic. Preferably, said housing structures (32, 60) are then subjected to a surface treatment, e.g. as required by safety regulations for use in inflammable or explosive environments .

Said first and second housing structures (32, 60) preferably have a cylindrical shape, closed at the bottom at the second end 31" of rod 3. The same first and second housing structures (32, 60) are open at the top, at the first end 31' of rod 3, where they are connected to fixing portion 30.

Said first and second cylindrical housing structures (32, 60) are internally hollow for substantially their whole length, each one defining an inner housing. The opening in the upper portion of the housing structures (32, 60) is such as to allow access to the inner portion and to allow communication with probe body 2.

Each inner housing has such dimensions as to allow, respectively: the first housing structure 32 to house said guide 5, and said second housing structure 60 to house at least said quality sensor 7.

Said guide 5 preferably covers the whole length of the first housing structure 32, so that the level measurement can be taken, through the magnetostrictive effect, along the entire length of rod 3.

As shown in Figures 1A and IB, said at least one float

4 envelops said housing structures (32, 60), moving in a direction coinciding with axis "k" along which rod 3 extends. In particular, the longitudinal axis of symmetry of float 4 corresponds to said axis "k".

As shown in Figure 2B, said float 4 envelops said housing structures (32, 60) . Said float 4 comprises two through holes (42, 42') in which said first housing structure 32 and said second housing structure 60 are respectively arranged, said structures being preferably inserted therethrough.

Said two holes (42, 42') are arranged, for example, in such a way that the segment joining the centres of the two holes (42, 42 ') passes through the central point of float 4.

For the purposes of the present description, the term "central point" refers to the point through which the longitudinal axis of symmetry of float 4 passes, in the direction of axis "k".

Preferably, said through holes (42, 42 ') have two different diameters. More preferably, the first through hole 42, associated with the first housing structure 32, has a smaller diameter than the second hole 42', associated with the second housing structure 60.

Describing more in detail the embodiment shown in Figure IB, said holes are circular holes secant to each other .

Said at least one float 4 incorporates or encloses, e.g. within an inner housing, at least one magnet 40. Said at least one magnet 40 is arranged in proximity to the first through hole 41, so that, once float 4 has been assembled to rod 3, the same magnet 40 is close to the first housing structure 32 where guide 5 is located. In the present embodiment, the longitudinal extension of said second housing structure 60 equals the length of rod 3.

In the second embodiment of probe 1, rod 3 is manufactured as a monolithic body. Rod 3 is preferably made of drawn plastic or metal material, which is then subjected to a surface treatment as required by safety regulations for use in inflammable or explosive environments. Figures IB, 3A, 3B and 4B illustrate, by way of non-limiting example, said second embodiment of rod 3.

In addition to said first housing structure 32 and said second housing structure 60, rod 3 comprises a third housing structure 31. Preferably, said third housing structure 31 also extends along the direction of axis "k". More preferably, said third housing structure 31 extends for substantially the whole length of rod 3.

Said first housing structure 32, said second housing structure 60 and said third housing structure 31 are obtained in the inner portion of rod 3 through holes that create a housing capable of containing, respectively, said guide 5 in the first housing structure 32 and said quality sensor 7 in said second housing structure 60. Said third housing structure 31 houses said at least one float 4, so that the latter can slide along a direction parallel to said axis "k". Said third housing structure 31 is so shaped as to be substantially inaccessible from the outside of said rod 3.

Said third housing structure 31 also acts as a still tube where the measurement of level "h" takes place, thus reducing any measurement uncertainty due to fluid turbulences . The dimensions of said first housing structure 32 are substantially the same as those of the first housing structure 32 of the previously described first embodiment of the probe.

Said third housing structure 31 preferably has an ellipsoidal shape, and is so sized as to allow said at least one float 4 to be positioned and to slide along the direction of said axis "k". The shape of said third housing structure 31 is such as to prevent float 4 from suffering sticking or other technical problems. Such a shape allows fluid "f" to flow within the third housing structure 31 and free float 4 should the latter get temporarily stuck.

As an alternative or in addition to its shape, said third housing structure 31 comprises longitudinal grooves, preferably four of them. Said longitudinal grooves extend for the whole length of the same housing structure 31.

Said longitudinal grooves are adapted to prevent the float from sticking to the walls of cavity 31.

Said second cavity 60 preferably has a circular or ellipsoidal shape, or any other shape suitable to allow inserting and properly positioning quality sensor 7.

In the non-limiting exemplary embodiment shown in Figures 3A, 3B and 4B, said second housing structure 60 and said third housing structure 31 communicate with each other, as clearly visible in Figure 3B.

In order to allow fluid "f" contained in tank "C" to flood cavity 31, so that its level can be measured, said rod 3 comprises at least one hole that allows, whether directly or indirectly, flooding the same third housing structure 31 when probe 1 is placed in an operating condition into tank "C". In an alternative embodiment (not shown), in order to reduce any measurement uncertainty or possible errors due to the effect of float 4 sticking to the inner walls of the third housing structure 31, it is conceivable to use a rod 3 comprising a plurality of independent third structures 31 parallel to one another and preferably equidistant from said guide 5, such that simultaneous level measurements can be taken on multiple floats 4.

In both embodiments shown in the annexed drawings, said quality sensor 7 is preferably arranged in the central region of the second housing structure 60 with respect to the longitudinal extension of the same.

Said second housing structure 60 comprises at least one through hole 601 adapted to allow fluid "f" contained in tank "C" to enter the same second housing structure 60. Said at least one through hole 601 allows fluid "f" to flood said second housing structure 60.

Preferably, said at least one through hole 601 is located on the side walls of the second housing structure 60, which, as aforementioned, has a cylindrical shape. Said at least one through hole 601 may possibly be located in the lower portion of the second housing structure 60, e.g. in proximity to the second end 31" of rod 3.

More preferably, said second housing structure 60 comprises at least two through holes 601. Said at least two through holes 601 are located one in the lower portion and the other in the upper portion, e.g. in proximity to the two ends (31', 31") of rod 3, for the purpose of allowing fluid "f" to be supplied and drained.

In the embodiments shown in Figures 1A, IB, 2A, 3A, 4A and 4B, the upper and lower portions of the second housing structure 60 comprise each a plurality of through holes 601.

In one embodiment not illustrated in the drawings, said second housing structure 60 comprises a through hole 601 in the central portion of the same housing structure 60.

Preferably, said at least one through hole 601 comprises an anti-intrusion device, which allows fluid "f" to enter the second housing structure 60, and possibly also the third housing structure 31, when probe 1 is inserted in tank "C", while nonetheless preventing any foreign body from getting into the housing structures (60, 31) . Said anti-intrusion device, which will not be described in detail herein, is adapted to prevent the entry of any foreign body both when the probe is inside tank "C" and when the probe is extracted from tank "C".

The anti-intrusion device will not be illustrated any further herein because it is known to those skilled in the art .

In general, each one of said housing structures (32,

60 and 31) is substantially inaccessible from the outside.

For the purposes of the present invention, the expression "cavity substantially inaccessible from the outside" refers to the fact that it is impossible to introduce any foreign bodies into the housing structures (32, 60, 31) .

Such inaccessibility of said housing structures prevents the probe from being tampered with.

The use of said quality sensor, comprised in the level probe, allows to obtain a single multifunctional device. The use of a fork-type quality sensor allows to overcome the drawbacks of the prior art, wherein float-type sensors equipped with a countering spring are only used.

The probe according to the present invention is also particularly suited to unconventional measurement conditions, such as high fluid pressure or high fluid velocity .

Through suitable computation algorithms, the probe according to the present invention can detect the percentage of a predetermined fluid contained in a mixture of fluids .

REFERENCE NUMERALS:

Level probe 1

Probe body 2

Electronic circuit 20

Data processing unit 201

Impulse generator 202

Receiver 203

Charge accumulation device 21

Non-volatile memory medium 22

Upper closing element 25

Rod 3

Fixing portion 30

Third housing structure 31

First end 31 '

Second end 31"

First housing structure 32

Float 4

Magnet 40

Through holes 42, 42'

Guide 5

Second housing structure 60 Through hole 601

Support element 61

Fluid quality sensor 7

Fork 70

Prongs 71, 71'

Electric generator 72

Equivalent circuit 73

Amplifier circuit 74

Temperature sensor 75

Outer casing 76

Central control unit 8

Line 81

Connector 811

Tank C

Fluid f

Level h

Axis k

Claims

CLAIMS :

1. A magnetostrictive level probe (1) to determine at least one level (h) of at least one fluid (f) contained in a tank (C) ;

said probe (1) comprises:

• a rod (3), which longitudinally extends along an axis (k) ,

• at least one mobile float (4), for sliding along the direction of said axis (k) ;

· at least one magnet (40), which is associated with each one of said at least one float (4) ;

• a probe body (2), which is fixed close to an end of said rod (3) and comprises at least one electronic circuit (20), said circuit being at least adapted to determine the position of said float (4) in the direction of said axis (k) ;

• at least one guide (5), for guiding a high-frequency electric impulse generated by said circuit (20);

• at least one first housing structure (32), which longitudinally extends along the direction of said axis (k) and houses a guide (5),

said probe is characterized in that:

• it comprises at least one second housing structure (60), which longitudinally extends along the direction of said axis (k) ;

• it comprises at least one fluid quality sensor (7), arranged in said second housing structure (60) and electrically connected to said at least one electronic circuit (20);

· said quality sensor (7) is adapted to measure the density, viscosity and dielectric constant of the fluid contained in the tank (C) , the quality and/or composition of which are to be determined.

2. Probe according to claim 1, wherein said quality sensor (7) is a single sensor, obtained by means of a tunable fork resonator (70) .

3. Probe according to claim 2, wherein the fork (70) comprises two prongs (71, 71') which can vibrate, resonating at the resonance frequency; said prongs (71) are fixed to the ends of a fixed portion.

4. Probe according to claim 1 or 2, wherein said electronic circuit (20) comprises a processing circuit, for processing the data coming both from the guide (5) and from the quality sensor (7) .

5. Probe according to any of the previous claims, wherein a temperature sensor (75) is provided.

6. Probe according to claim 1 or 4, wherein said electronic circuit (20) comprises at least one non-volatile memory unit, where an at least three-dimensional database resides, in which each triad of values, namely density, viscosity and dielectric constant, is associated with at least one datum or result concerning the quality and/or composition of the fluid (f ) .

7. Probe according to claim 1, wherein said at least one second housing structure (60) comprises at least one through hole (601), for allowing the fluid (f) contained in the tank (C) to flood said at least one second housing structure (60).

8. Probe according to claim 1, wherein said rod (3) is obtained from the cooperation of the first housing structure (32) and of the second housing structure (60), which are arranged parallel to each other, properly spaced apart, and are kept in position by a fixing portion (30); said at least one float (4) is assembled and arranged so as to be able to slide along said housing structures (32, 60), thus using them as guides on which it can slide.

9. Probe according to claim 1, wherein said rod (3) is manufactured as a monolithic body and comprises at least one third housing structure (31), which houses said at least one float (4), said structure being so shaped as to be substantially inaccessible from the outside of said rod (3) .

10. Probe according to any of the previous claims, wherein said probe (1) is suited to be connected to an outer control unit (8) by means of at least one data line (81) .