AU2014224190A1

AU2014224190A1 - Fluid monitoring system

Info

Publication number: AU2014224190A1
Application number: AU2014224190A
Authority: AU
Inventors: Larry Stewart Ellison
Original assignee: SMART SOLUTIONS Ltd
Current assignee: Levno Ltd
Priority date: 2013-03-06
Filing date: 2014-03-06
Publication date: 2015-10-29
Also published as: AU2014101631A4; AU2014224190A2; WO2014136071A1

Abstract

A fluid monitoring system (100) for a tank (102) comprising a fluid measuring device (104) having a controller (160), a sensor arrangement (106), a sensor module (154) in communication with the sensor arrangement (106), and a communications module (108). The sensor arrangement (154) is at least partially locatable within the tank (102) and has a sensor (140) configured to generate an electrical signal relating to an amount of fluid in the tank (102). A server is configured to receive the signal from the sensor arrangement (106). The server (10) is further configured to transmit the signal to a user device (116) remote to the tank (104). The communications module (108) is configured to transmit the signal to the server (110).

Description

WO 2014/136071 PCT/IB2014/059480 1 FLUID MONITORING SYSTEM RELATED APPLICATIONS The full disclosure of New Zealand provisional patent specification 607914, entitled 5 'FLUID MONITORING SYSTEM' and filed 6 March 2013, is hereby incorporated by reference. FIELD OF THE INVENTION The present invention relates to a fluid monitoring system for a tank and a method for 10 monitoring the level of fluid in a tank. BACKGROUND In an environment where tanks are located in remote or rural locations, a person needs to physically go to each tank to determine an amount of fluid in the tank. In 15 the case where the tank is a fuel storage tank, a person may periodically go to each tank to determine the amount of fuel in the tank, and refuel the tank if necessary. If the tank does not require refuelling, the person's time and costs of travelling to the tank are wasted. 20 An embodiment of the present invention seeks to provide a fluid monitoring system that overcomes one or more disadvantages of the above mentioned system. Alternatively or additionally, an embodiment of the present invention seeks to at least provide the public with a useful choice. 25 SUMMARY OF THE INVENTION The present invention provides a fluid monitoring system for a tank, the fluid monitoring system comprising: a sensor arrangement at least partially locatable within the tank and having a 30 capacitive sensor configured to generate an electrical capacitance signal relating to an amount of fluid in the tank; a server being configured to receive the signal, and/or information indicating an amount of fluid in the tank based on the signal, from the sensor arrangement over a communications network, and 35 configured to transmit the signal, and/or information indicating an amount of fluid in the tank based on the signal, to a user device remote of the tank over the communications network; and WO 2014/136071 PCT/IB2014/059480 2 a controller comprising or connected to a communications module, and a sensor module in communication with the sensor arrangement, the communications module being in communication with the sensor module, and configured to transmit the signal, and/or information indicating an amount of fluid 5 in the tank based on the signal, to the server over the communications network. The capacitance signal may relate to a height or a level of fluid in the tank. The fluid may comprise a liquid and/or a gas. The fluid may comprise fuel. The fluid 10 may comprise diesel or petrol. The system may be configured to monitor the level of liquid in the tank. The sensor arrangement may be removably insertable into the tank. Alternatively, the sensor arrangement may be fixedly positioned within the tank. 15 The sensor arrangement may comprise an electrical circuit and the electrical circuit may be configured to generate the signal relating to the amount of fluid in the tank. The capacitive sensor may comprise a cylindrical capacitor having an inner cylinder 20 and an outer hollow cylinder that surrounds the inner cylinder, the inner and outer cylinders being substantially coaxial and having a space therebetween. The capacitive sensor may be configured to generate the capacitance signal based on a level of fluid in the space between the inner and outer cylinders, the level of fluid in the space between the inner and outer cylinders corresponding to a level of fluid in the tank. 25 The capacitive sensor may be locatable at least partially within the tank so that the inner and outer cylinders extend vertically from at or near a top of the tank to at or near a bottom of the tank. 30 The capacitive sensor may comprise at least one spacer for maintaining the spacing between the outer cylinder from the inner cylinder. The spacer may be mounted to the inner cylinder. The outer cylinder may be driven with an oscillating voltage. The outer cylinder may 35 be driven at a peak-to-peak AC voltage of between about 20 mV and about 4 V and a current between about 20 nA and about 20 mA. The outer cylinder may be driven at a WO 2014/136071 PCT/IB2014/059480 3 peak-to-peak AC voltage of up to about 200mV and a current of less than about 500 pA. Alternatively, the capacitive sensor may be a plate capacitor with two spaced apart 5 plates for generating a capacitance signal based on a level of fluid in the space between the plates. The capacitive sensor may comprise aluminium. Additionally or alternatively, the capacitive sensor may comprise stainless steel or another suitable material. 10 The sensor arrangement may comprise a plurality of capacitive sensors positioned within the tank. The communications module may comprise a cellular modem and an antenna. The 15 antenna may be a radio network antenna. The radio network antenna may be a General Packet Radio Service (GPRS) antenna, a code division multiple access (CDMA) antenna, a third generation (3G) antenna, or another suitable radio antenna. The system may further comprise computer memory, wherein the server is configured 20 is to store data representing a plurality of the signals generated and logged over a period of time, and/or information indicating amount(s) of fluid in the tank based on the signals, in the memory; and the server may be configured to transmit the signals, and/or information indicating amount(s) of fluid in the tank based on the signals, to the user device. The memory may be in the form of a database located remote of the 25 tank. The server may be accessible via a communications network, such as a local area network, a wide area network or the Internet. The communications network may comprise a private Access Port Network (APN). 30 The system may comprise a software platform at a user end for communication with the server. The user may access the server and the database through the software platform. The server may be configured so that a user device can access the server via a web interface. The server may be configured to transmit the signal, and/or 35 information indicating an amount of fluid in the tank based on the signal, to at least one of a desktop computing device, a laptop, a tablet and a smart phone device over the communications network.

WO 2014/136071 PCT/IB2014/059480 4 The system may further comprise an identification module for generating a unique identifier of the tank. The communications module may be configured to transmit the identifier of the tank to the server. The identification module may comprise a Global 5 Positioning System (GPS) unit and a GPS antenna, and the identifier may comprise a position of the tank. The system may comprise a power supply for providing power to at least the sensor arrangement and the communications module. The power supply unit may be located 10 substantially outside the tank. The power supply may be in the form of a power supply unit having a battery. The power supply unit may comprise a lead-acid battery. Alternatively, the power supply unit may comprise a lithium battery, a lithium ion battery, or another suitable battery. Additionally or alternatively, the power supply unit may comprise an electrical charge storage component, such as a 15 super capacitor for example. The power supply unit may be configured to provide a voltage of about 2 V to about 24 V. The power supply unit may be configured to provide a voltage of about 4.2 V. The system may comprise at least one solar panel or photovoltaic cell for charging the power supply unit. 20 The system may comprise a controller for receiving the generated signal from the sensor arrangement, wherein the controller is configured to determine the amount of fluid in the tank based on the generated signal. The controller may comprise a sensor module and/or be in electronic communication with the sensor arrangement for controlling an operation of the sensor arrangement. The controller may comprise or 25 be in electronic communication with a solar panel module, a battery module, a power supply unit module, and the GPS unit. The communications module may be configured to transmit an alert signal to the server when the determined amount of fluid in the tank drops below, or rises above, 30 or substantially equals, a predetermined threshold or amount. The communications module may be configured to transmit an alert signal to the server when there is an extraction or insertion of fluid from the tank. The communications module may be configured to transmit the alert signal to the server when there is unauthorised extraction of fluid from the tank. 35 The system may comprise a housing that is adapted to house the controller, the battery, and the cellular modem. The housing may comprise one or more ports that WO 2014/136071 PCT/IB2014/059480 5 are electronically connected to the controller. Alternatively, each port may be connectable to a respective one of the sensor arrangement, the cellular antenna, the GPS antenna, and the solar panel. The housing may comprise polycarbonate, other suitable polymeric materials, or other suitable materials. An example of other suitable 5 materials includes aluminium. The present invention further provides a method for monitoring the level of fluid in a tank, the method comprising: generating, using a capacitive sensor at least partially located within the tank, 10 an electrical capacitance signal relating to an amount of fluid in the tank; transmitting the signal, and/or information indicating an amount of fluid in the tank based on the signal, to a server over a communications network; and transmitting the signal, and/or information indicating an amount of fluid in the tank based on the signal, from the server to a user device remote of the tank over the 15 communications network. The capacitance signal may relate to a height or a level of fluid in the tank. The fluid may comprise a liquid and/or a gas. The fluid may comprise fuel. The fluid 20 may comprise diesel or petrol. The method may be for monitoring the level of liquid in the tank. The method may comprise removably inserting the sensor arrangement into the tank. Alternatively, the method may comprise fixedly positioning the sensor arrangement within the tank. 25 The sensor arrangement may comprise an electrical circuit and the method may comprise generating the signal relating to the amount of fluid in the tank using the electrical circuit. 30 The capacitive sensor may comprise a cylindrical capacitor having an inner cylinder and an outer hollow cylinder that surrounds the inner cylinder, the inner and outer cylinders being substantially coaxial and having a space therebetween, and the method may comprise generating the capacitance signal based on a level of fluid in the space between the inner and outer cylinders, the level of fluid in the space 35 between the inner and outer cylinders corresponding to a level of fluid in the tank.

WO 2014/136071 PCT/IB2014/059480 6 The method may further comprise locating the capacitive sensor at least partially within the tank such that the inner and outer cylinders extend vertically from at or near a top of the tank to at or near a bottom of the tank. 5 The method may further comprise driving the outer cylinder with an oscillating voltage. The method may comprise driving the outer cylinder at a peak-to-peak AC voltage of between about 20 mV and about 4 V and a current between about 20 nA and about 20 mA. The method may comprise driving the outer cylinder at a peak-to peak AC voltage of up to about 2 V and a current of less than about 500 pA. 10 Alternatively, the capacitive sensor may comprise a plate capacitor having two spaced apart plates; and the method may comprise generating the capacitance signal based on a level of fluid in the space between the plates. 15 The method may further comprise wirelessly transmitting, using the communications module, the generated signal from the sensor arrangement and/or information indicating an amount of fluid in the tank based on the generated signal from the sensor arrangement to the server. The communications module may comprise a cellular modem and an antenna, wherein the antenna may be a radio network 20 antenna. The radio network antenna may be a General Packet Radio Service (GPRS) antenna, a code division multiple access (CDMA) antenna, a third generation (3G) antenna, or another suitable radio antenna. The server may be accessible via a communications network. The communications 25 network may be a local area network, a wide area network or the Internet. The communications network may comprise a private Access Port Network (APN). The server may be in communication with a software platform at a user end. The method may further comprise allowing a user to access the server through the 30 software platform. The method may further comprise generating, using an identification module, a unique identifier of the tank. The method may further comprise transmitting the identifier of the tank to the server, using the communications module. The identification module 35 may comprise a Global Positioning System (GPS) unit and a GPS antenna, and the identifier comprises a position of the tank.

WO 2014/136071 PCT/IB2014/059480 7 The method may further comprise the server storing data representing a plurality of the signals generated and logged over a period of time, and/or information indicating amount(s) of fluid in the tank based on the signals, in computer memory; and transmitting the logged signals, and/or information indicating amount(s) of fluid in the 5 tank based on the signals, to the user device. The memory may be in the form of a database located remote of the tank. The method may further comprise receiving, by a controller, the generated signal from the sensor arrangement, and determining, by the controller, the amount of fluid in the 10 tank based on the generated signal. The method may further comprise controlling an operation of the sensor arrangement using the controller. The controller may comprise or be in electronic communication with a solar panel module, a battery module, a power supply unit module, and the GPS unit. 15 The method may further comprise transmitting an alert signal, using the communications module, to the server when the determined amount of fluid in the tank drops below, or rises above, or meets, a predetermined threshold. The method may further comprises transmitting an alert signal, using the communications module, to the server when there is an extraction or insertion of fluid from the tank. The 20 method comprises transmitting an alert signal, using the communications module, to the server when there is unauthorised extraction of fluid from the tank. The present invention still further provides a fluid monitoring system for a tank, the fluid monitoring system comprising: 25 a fluid measuring device having a controller, a sensor arrangement, a sensor module in communication with the sensor arrangement, and a communications module, the controller comprising or being connected to, and for controlling an operation of, the communications module and the sensor module, 30 the sensor arrangement being at least partially locatable within the tank and having a sensor configured to generate an electrical signal relating to an amount of fluid in the tank; a server being configured to receive the signal, and/or information indicating an amount of fluid in the tank based on the signal, from the sensor arrangement over 35 a communications network, and WO 2014/136071 PCT/IB2014/059480 8 configured to transmit the signal, and/or information indicating an amount of fluid in the tank based on the signal, to a user device remote of the tank over the communications network; and the communications module being in communication with the sensor module, 5 and configured to transmit the signal, and/or information indicating an amount of fluid in the tank based on the signal, to the server over the communications network. To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest 10 themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting. Where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if 15 individually set forth. As used herein '(s)' following a noun means the plural and/or singular forms of the noun. 20 As used herein the term 'and/or' means 'and' or 'or' or both. The term 'comprising' as used in this specification means 'consisting at least in part of'. When interpreting each statement in this specification that includes the term 'comprising', features other than that or those prefaced by the term may also be 25 present. Related terms such as 'comprise' and 'comprises' are to be interpreted in the same manner. The term 'connected to' includes all direct or indirect types of communication, including wired and wireless, via a cellular network, via a data bus, or any other 30 computer structure. It is envisaged that they may be intervening elements between the connected integers. Variants such as 'in communication with', 'joined to', and 'attached to' are to be interpreted in a similar manner. The term 'computer-readable medium' should be taken to include a single medium or 35 multiple media. Examples of multiple media include a centralised or distributed database and/or associated caches. These multiple media store the one or more sets of computer executable instructions. The term 'computer readable medium' should WO 2014/136071 PCT/IB2014/059480 9 also be taken to include any medium that is capable of storing, encoding or carrying a set of instructions for execution by a processor and that cause the processor to perform any one or more of the methods described above. The computer-readable medium is also capable of storing, encoding or carrying data structures used by or 5 associated with these sets of instructions. The term 'computer-readable medium' includes solid-state memories, optical media and magnetic media. It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 10 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5, and 3.1 to 4.7) and, therefore, all sub-ranges of all ranges expressly disclosed herein are hereby expressly disclosed. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are 15 to be considered to be expressly stated in this application in a similar manner. In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically 20 stated otherwise, reference to such external documents or such sources of information is not to be construed as an admission that such documents or such sources of information, in any jurisdiction, are prior art or form part of the common general knowledge in the art. 25 Although the present invention is broadly as defined above, those persons skilled in the art will appreciate that the invention is not limited thereto and that the invention also includes embodiments of which the following description gives examples. BRIEF DESCRIPTION OF THE FIGURES 30 Embodiments of the invention will now be described, by way of non-limiting example, with reference to the figures in which: Figure 1 shows a general fluid monitoring system diagram of the system according to an embodiment of the present invention; Figure 2 shows a simplified block diagram of a fluid measuring device of the 35 system of figure 1; Figure 3 shows a perspective view of a first end of a capacitive sensor according to an embodiment of the present invention; WO 2014/136071 PCT/IB2014/059480 10 Figure 4 shows perspective view of a second end of the capacitive sensor of figure 3 disassembled; Figure 5 shows another perspective view of the capacitive sensor of figure 3 disassembled; 5 Figure 6 shows an example response of the capacitive sensor to a change in liquid level in the tank; Figure 7 shows an example response of the capacitive sensor to a change in liquid volume in the tank; Figure 8 shows a sensor module block diagram according to an embodiment of 10 the present invention; Figure 9 shows a flow chart of a method for determining a level of liquid in a tank according to an embodiment of the present invention; Figure 10 shows a perspective view of housing for the controller and a power supply according to an embodiment of the present invention; 15 Figure 11 shows a side view of the housing shown in figure 10; Figure 12 shows a front view of an interior section of the housing shown in figure 10; and Figure 13 shows a simplified block diagram of an example form of a computing device that may form at least part of the server and/or a user device for accessing the 20 server. DETAILED DESCRIPTION A fluid monitoring system 100 according to an embodiment of the present invention is shown in figure 1. The system 100 is configured to monitor the level of fluid in a tank 25 102 using a fluid measuring device (or transceiver device) 104 that is positioned in proximity of, and at least partially within, the tank 102. With reference to figure 2, the device 104 comprises a sensor arrangement 106 which is configured to generate a signal relating to an amount of fluid in the tank 102. The device 104 further comprises a communications module 108 for transmitting the generated signal, from 30 the sensor arrangement 106 and/or information indicating an amount of fluid in the tank 102 based on the generated signal from the sensor arrangement 106, to a server 110 via a communications network 112. The server 110 comprises or is connected to computer memory, in the form of a database 114, for storing data relating to the amount of fluid in one or more tanks. In the device 104, the communications module 35 108 is electronically connected to the sensor arrangement 106.

WO 2014/136071 PCT/IB2014/059480 11 The server 110 is accessible by one or more end user devices 116 via the communications network 112. The server 110 controls access to the database 114, and is configured to store data relating to an amount of fluid in the tank 102 in the database 114, to look up data stored in the database 114, and to send data relating to 5 an amount of fluid in the tank 102 to the user device 116. In the embodiment described, the fluid in the tank 102 to be monitored comprises fuel, such as petrol and/or diesel, and the system is configured to monitor the level of fuel in the tank 102. The system is designed to be intrinsically safe. According to 10 other embodiments, the system may be configured to monitor other fluids, including gases, and other liquids such as water or milk. The tank 102 may be permanently located in a single location. Alternatively, the tank may be moveable. For example, the tank may be mounted to a truck or other vehicle. 15 The sensor arrangement The sensor arrangement 106 is preferably removably insertable into the tank 102. In an alternative embodiment, the sensor arrangement 106 may be fixedly positioned 20 within the tank 102. The preferred form of the sensor arrangement 106 comprises an electrical circuit that is configured to generate an electrical signal relating to the amount of fluid in the tank 102. The electrical circuit may comprise an arrangement of passive electronic 25 components (such as capacitors, resistors, and inductors) and/or active electronic components (such as integrated circuits). Referring to figures 3 to 5, the sensor arrangement 106 comprises a capacitive sensor (or 'probe') 140 that is configured to generate a capacitance signal that relates to the 30 height of fluid in the tank 102 relative to the capacitive sensor 140. The sensor arrangement 106 may comprise more than one capacitive sensor positioned within the tank 102. The capacitive sensor 140 comprises a cylindrical capacitor having an inner cylinder 35 142 and an outer hollow cylinder 144 that surrounds the inner cylinder 142. The inner and outer cylinders (or electrodes) 142, 144 are substantially coaxial with each other and have a space 146 therebetween. Referring to figure 5, a spacer 148 is provided WO 2014/136071 PCT/IB2014/059480 12 to prevent the inner cylinder 142 from contacting the outer cylinder 144 and to maintain a uniform spacing between the inner and outer cylinders 142, 144. The spacer 148 is removably connected to the inner cylinder 142. The inner and outer cylinders 142, 144 may be located at least partially within the tank 102 to extend from 5 at or near a top of the tank 102 to at or near a bottom of the tank 102. Alternatively, a user interested when the amount of fuel in the tank 102 is nearing empty, for example, may locate the inner and outer cylinders 142, 144 to extend vertically from a location intermediate the top and the bottom to at or near the bottom. The capacitance signal will only change when the level of the fluid is between the location 10 intermediate the top and the bottom and at or near the bottom of the tank 102. Referring to figure 4, the capacitive sensor 140 comprises a mount 150, which is configured to rest on a wall of the tank 102 being monitored. The mount 150 has a nose 152 that protrudes or sticks into the interior of the tank 102. The nose 152 is a 15 hollow cylinder having an externally threaded wall for threadably engaging the outer cylinder 144, and an internally threaded wall for threadably engaging the inner cylinder 142. The typically solid inner cylinder 142 may have a diameter of between, for example, 20 about 3 mm and about 8 mm. According to one preferred form of the capacitive sensor 140, the inner cylinder 142 has a diameter of about 4.76 mm. The outer cylinder 144 may have an inner diameter of between, for example, about 10 mm and about 20 mm and a thickness between about 0.7 mm and 3 mm. According to one preferred form of the capacitive sensor 140, the outer cylinder 144 may have a 25 diameter of 12.7 mm and a wall thickness of about 1.4 mm. The inner and outer cylinders 142, 144 of the capacitive sensor 140 are configured to be immersed in the liquid in the tank 102. A change in level of liquid in the space 146 between the inner and outer cylinders 142, 144 results in a change in the capacitance signal generated by the capacitive sensor 140. The capacitive sensor 140 is placed substantially 30 vertically in the tank 102 so that the level of liquid between the cylinders 142, 144 changes as the volume of liquid in the tank 102 changes. Capacitance is linearly dependent on the relative permittivity of the material between plates of the capacitor. When the capacitive sensor 140 is positioned in a liquid, the 35 capacitance of the sensor 140 depends on the level of liquid in the space 146 between the cylinders 142, 144. Liquid has a different relative permittivity than air. Fuel has a relative permittivity of about 2.1, while air has a relative permittivity of about 1.0.

WO 2014/136071 PCT/IB2014/059480 13 The measured capacitance is used to determine the level or height of the liquid relative to the capacitive sensor 140. The volume of liquid in the tank 102 can be determined by multiplying the determined level or height of the liquid with geometry of the tank 102. 5 The formula for determining the capacitance Cprobe of a cylindrical capacitor is shown below: C probe = 2 ;Tc O~ L ln( ) a where Eo is the absolute permittivity (8.854e-12 Fm-1), Er is the relative permittivity of 10 the dielectric between the inner and outer cylinders, L is the length of the shortest of the inner and outer cylinders 142, 144, a is the radius of the inner cylinder 142, and b is the inner radius of the outer cylinder 144. The height of the liquid H;iqu idcan be determined from the measured capacitance based 15 on the following formula: I( b ln(-) H liquid = ( liquid - Ea,, )* a * (Cea,red - C,,) 2w 0 j where Eliquid is the permittivity of the liquid, Eair is the permittivity of air, Cmeasured is the measured capacitance of the probe, and Cair is the measured capacitance in air. 20 The outer cylinder 144 may be driven at a peak-to-peak AC voltage of between about 20 mV and about 4 V and a current between about 20 nA and about 20 mA. Preferably, the outer cylinder 144 is driven with an oscillating voltage with a peak-to peak voltage of up to about 200 mV and a current of less than about 500 pA. 25 The inner and outer cylinders (or electrodes) 142, 144 are formed of aluminium. The inner and outer cylinders 142, 144 may alternatively or additionally be formed of stainless steel and/or another suitable material. Figure 6 shows an example capacitive response of the capacitive sensor 140 to a 30 change in liquid level in the tank 102 from a trial run. The capacitive sensor 140 used in this run had an inner cylinder diameter of about 5 mm, an outer cylinder inner diameter of about 10 mm and a length of about 700 mm. The typical response is substantially linear. The height of liquid in the tank 102 relative to the capacitive WO 2014/136071 PCT/IB2014/059480 14 sensor 140 can be determined from the measured capacitance of the capacitive sensor 140. Based on the geometry of the tank 102, the volume of liquid in the tank 102 can be 5 determined accordingly. Figure 7 shows the relationship between the capacitance measured by the capacitive sensor 140 and the volume of the tank 102. In this run, the tank 102 is substantially cylindrical with an inner radius of about 321 mm and a length of about 935 mm. The tank 102, as shown in figure 1, is a substantially horizontal cylinder tank. However, it will be understood the present system and 10 method may be applicable to other tanks. For example the tank may be a substantially vertical cylinder tank. Alternatively, the tank may be any other suitable receptacle, container, or structure for holding a liquid or gas having other shapes. The results of the capacitance, height, and volume measurements for the trial run are 15 shown in the table below. Capacitance (DF) Height (mm) Volume (L) 57.7 13.4 1.5 61.0 50.0 10.9 63.5 78.2 21.0 69.3 143.0 50.3 73.7 193.3 76.7 79.2 255.2 112.1 82.6 292.6 134.3 86.3 334.5 159.4 90.3 379.2 186.1 94.2 423.5 211.8 95.8 440.8 221.5 97.4 459.7 231.9 101.9 510.1 257.9 109.2 592.1 291.8 112.4 627.3 300.9 111.1 613.0 297.8 According to other embodiments, the capacitive sensor may be a plate capacitor with two spaced apart plates for generating a capacitance signal based on a level of fluid 20 between the plates.

WO 2014/136071 PCT/IB2014/059480 15 The sensor arrangement 106 may comprise one or more other sensors, each configured to generate a signal that relates to the height and/or volume of fluid in the tank 102. For example, the sensor arrangement 106 may comprise an ultrasonic (or 5 'ultrasound') sensor/probe suitable for generating a signal to measure the height and/or volume of other fluids such as milk. The sensor module 10 With reference to figure 8, a sensor module 154 is provided to process signals from the capacitive sensor 140 and to control the operation of the capacitive sensor 140. A 'module' is a collection of analogue and digital electronics. A module may be a pre made module such as a GPRS cellular module purchased from a supplier. A module may include software which controls specific parts such as a modem driver. A module 15 may include a digital logic block, such as a field-programmable gate array (FPGA) or similar configurable logic blocks. A module may be a combination of two or more of the above features. The sensor module 154 comprises an integrated circuit (IC). An example of a suitable 20 IC for the sensor module 154 may be a capacitance-to-digital converter sensor IC, such as an AD7746 for example. The sensor IC of the sensor module 154 allows for two capacitances 702, 704 to be measured by a capacitance sensor 706. The first capacitance measurement 702 is a reference calibration capacitance, and the second capacitance measurement 704 is the capacitance that is measured by the sensor 25 arrangement 106. The sensor IC additionally measures an external temperature 708, which is used in a calibration procedure described below. The sensor module 154 further comprises a communications channel 710 for communicating data to a controller or the communications module that is described in further detail below. The sensor module 154 additionally comprises memory 712 for storing calibration data for 30 example. The sensor module 154 comprises a range extension circuit 714 to enable a larger capacitance to be measured than the range possible with the sensor IC alone. A probe calibration procedure is carried out to compensate for large variations caused by 35 the range extension circuit 714, manufacturing variations in the capacitive sensor 140 and also due to the inherent nature of the capacitive measurement method. This probe calibration procedure uses a reference capacitor having a known capacitance.

WO 2014/136071 PCT/IB2014/059480 16 The reference capacitor has a similar capacitance to the capacitance of the capacitive sensor 140 when the tank 102 is 'empty'. The calibration procedure essentially calibrates the sensor 140 for any offset or linearity errors. 5 The steps of the calibration procedure are set out below: 1) look up a unique sensor identification number from non-volatile memory 712 2) measure the calibration capacitance and the zero capacitance (no probe connected), calculate the gradient from these two points, and store the gradient in non-volatile memory 712 10 3) connect the capacitive sensor 140 (in air environment 25'C) and increase an offset until measurements from both the calibration capacitor and the capacitive sensor 140 are above zero, but close as possible, and store offset in non-volatile memory 4) store the offset, calibration value, and probe capacitance in air in non-volatile 15 memory 712 5) store probe dimensions in non-volatile memory 712. The unique sensor identification number is unique to the sensor. In one embodiment, the number comprises a EEPROM IC with built in 64-bit unique number. In an 20 alternative embodiment, the number is assigned at factory calibration. The number is required for identifying the sensor to the remote server 110 and enables tracking of the sensor electronics though factory calibration, to field connection to a tank 102. Additionally, each communications module 108 has a unique identification number for identifying the device 104. In one embodiment, the number is the IMEI number 25 provided by the cellular modem. This number is used for tracking each device 104 and is sent to the server 110 with each message for message source identification such as a MAC address is used in a computer. The two different identification numbers, a unique identification number for the device 104 and a unique identification number for each sensor of the device 104, allow multiple sensors electronics (each 30 with one probe) to be connected to one cellular module (sending device). The calibration data variables that are gathered during this calibration procedure are stored in the calibration storage memory 712. The controller and/or software platform and/or remote server 110 described below uses these data variables to make (more 35 accurate) height calculations. Some calculations and averaging may be performed on server 110 and some may be performed on the device 104. The device 104 sends the calibration values to the server 110 when the device 104 is turned on. The device 104 WO 2014/136071 PCT/IB2014/059480 17 calculates the capacitance from the slope and the offset. The device 104 notifies the server 110 if a capacitance threshold level change is detected. The server 110 calculates height and then volume from the sent capacitance values, the calibration values and the stored tank dimensions (on database) information to derive a tank 5 volume. The method 800 for the determining the liquid level is shown in figure 9. Once the device 104 is turned on 802, calibration data is read 804 from the calibration storage memory of the sensor module 154. The sensor module 154 measures 806 the raw 10 data from the capacitive sensor 140. The raw data is converted 808 into capacitance measurements using the calibration data. The capacitance measurements are averaged 810, and a determination is made 812 if there is a change of level in the tank 102. If there is a change in level, a notification is sent 814 to the remote server 110. Once the notification is sent or if there is no change in level, the controller goes 15 back to the step of determining 806 the raw data from the capacitive sensor. The communications module and identification module The communications module 108 is configured to wirelessly transmit the determined 20 amount of fluid to the remote server 110 by the communications network 112. The communications module 108 comprises or is in communication with a cellular modem and a radio network antenna. The type of radio network antenna that is used depends on the technology available. For example, the radio network antenna could be a Global Packet Radio Service (GPRS) antenna, a code division multiple access (CDMA) 25 antenna, or a third generation (3G) antenna, or another suitable radio antenna. The communications module 108 is configured to transmit an alert signal to the server 110 over the radio network when the determined amount of fluid in the tank 102 drops below, or rises above, or meets, a predetermined threshold. 30 Alternatively, the communications module may comprise or be in communication with a satellite modem and a satellite antenna, and be configured to communicate with and transmit signals to the server 110 via one or more satellites. The device 104 further comprises an identification module 156 for generating an 35 identifier of the tank 102. The communications module 108 is configured to transmit the identifier of the tank 102 to the remote server 110. The server 110 may store data relating to multiple sensors and multiple tanks in the database 114. The WO 2014/136071 PCT/IB2014/059480 18 identification module 156 comprises a GPS unit and a GPS antenna, and the identifier comprises a position of the tank 102. The server and the database 5 The server 110 and the database 114 are both typically located remote of the tank 102. They are accessible by user device 116 over the communications network 112, such as via a local area network, a wide area network or the Internet. The communications network may include private Access Port Network (APN). 10 The system comprises a software platform at the user device 116 for communication with the server 110. An end user can access the server through the software platform to obtain information stored in the database 114 about the amount of fuel in the tank 102. An end user can also access the server to generate and/or view reports of 15 historical fuel usage from one or more tanks that is stored in the database 114. A user will typically access the server 110/database 114 via a web interface. The user device 116 will typically comprise a general-purpose programming device, such as one or more of a desktop computing device, laptop, tablet or smart phone. 20 Figure 13 shows a simplified block diagram of an example form of a computing device 200 that may form at least part of the server 110 and/or the user device 116. Sets of computer executable instructions are executed within device 200 that cause 25 the device 200 to perform the methods described above. Preferably the computing device 200 is connected to other devices. Where the device is networked to other devices, the device is configured to operate in the capacity of a server or a client machine in a server-client network environment. Alternatively the device can operate as a peer machine in a peer-to-peer or distributed network environment. The device 30 may also include any other machine capable of executing a set of instructions that specify actions to be taken by that machine. These instructions can be sequential or otherwise. A single device 200 is shown in Figure 2. The term 'computing device' includes any 35 collection of machines that individually or jointly execute a set or multiple sets of instructions to perform any one or more of the methods described above.

WO 2014/136071 PCT/IB2014/059480 19 The example computing device 200 includes a processor 205. One example of a processor is a central processing unit or CPU. The device further includes read-only memory (ROM) 210 and random access memory (RAM) 215. Also included is a Basic Input/Output System (BIOS) chip 220. The processor 205, ROM 210, RAM 215 and the 5 BIOS chip 220 communicate with each other via a central motherboard 225. Computing device 200 further includes a power supply 230 which provides electricity to the computing device 200. Power supply 230 may also be supplemented with a rechargeable battery (not shown) that provides power to the device 200 in the 10 absence of external power. Also included are one or more drives 235. These drives include one or more hard drives and/or one or more solid state flash hard drives. Drives 235 also include optical drives. 15 Network interface device 240 includes a modem and/or wireless card that permits the computing device 200 to communicate with other devices. Computing device 200 may also comprise a sound and/or graphics card 245 to support the operation of the data output device 260 described below. Computing device 200 further includes a cooling 20 system 250 for example a heat sink or fan. Computing device 200 includes one or more data input devices 255. These devices include a keyboard, touchpad, touchscreen, mouse, and/or joystick. The device(s) take(s) input from manual keypresses, user touch with finger(s) or stylus, spoken 25 commands, gestures, and/or movement/orientation of the device. Data output device(s) 260 include(s) a display and/or printer. Device(s) 260 may further include computer executable instructions that cause the computing device 200 to generate a data file such as a PDF file. 30 Data port 265 is able to receive a computer readable medium on which is stored one or more sets of instructions and data structures, for example computer software. The software causes the computing device 200 to perform one or more of the methods or functions described above. Data port 265 includes a USB port, Firewire port, or other 35 type of interface. The computer readable medium includes a solid state storage device. Where drives 235 include an optical media drive, the computer readable medium includes a CD-ROM, DVD-ROM, Blu-ray, or other optical medium.

WO 2014/136071 PCT/IB2014/059480 20 Software may also reside completely or at least partially within ROM 210, within erasable non-volatile storage and/or within processor 205 during execution by the computing device 200. In this case ROM 210 and processor 205 constitute computer 5 readable tangible storage media. Software may further be transmitted or received over a network via network interface device 240. The data transfer uses any one of a number of well known transfer protocols. One example is hypertext transfer protocol (http). 10 Power supply unit The system comprises a power supply for supplying power to the device 104 in the form of power supply unit 158 that is located outside the tank 102 for safety. The power supply unit 158 comprises a lead-acid battery. According to other 15 embodiments of the system, the power supply unit 158 comprises a lithium battery, a lithium ion battery, or another battery. According to further embodiments, the power supply unit 158 comprises an electrical charge storage component, such as a super capacitor for example. The power supply unit 158 is arranged to provide a voltage of about 2 V to about 24 V, and preferably 4.2 V. 20 Advantageously, the relatively low power requirements of the sensor arrangement 106 and communications module 108 enable the device 104 to substantially run off solar power. In one embodiment, the system comprises photovoltaic cells for collecting solar energy to charge the power supply unit 158. 25 Alternatively the power supply for supplying power to the device 104 may be a mains power supply. Method for monitoring the level of fluid 30 The method for monitoring the level of fuel in the tank 102 according to an embodiment of the present invention comprises: generating a signal relating to an amount of fluid in the tank 102 using the sensor arrangement 106 locatable within the tank 102. The generated signal is representative or indicative of the level of fuel in 35 the tank 102. The sensor arrangement 106 is removably inserted into the tank 102 through an aperture in a wall of the tank 102. In an alternative embodiment, the WO 2014/136071 PCT/IB2014/059480 21 method may comprise fixedly positioning the sensor arrangement 106 within the tank 102. Features of the sensor arrangement 106 have been previously described. The method comprises transmitting, using the communications module 108 that is 5 electronically coupled to the sensor arrangement 106, the generated signal from the sensor arrangement 106, and/or information indicating an amount of fluid in the tank 102 based on the generated signal from the sensor arrangement 106, to the server 110 that is accessible by a user. For example, where the sensor arrangement 106 comprises a capacitive sensor, the communications module 108 may transmit the 10 capacitance measurements to the server 110, and the volume and/or level values are calculated based on the capacitive measurements at the user device 116 for example. Alternatively, the capacitance measurements may be converted to height or volume values of fuel in the tank 102 before the measurements are transmitted to the server 110 and remote database 114. Features of the communications module 108, server 15 110 and remote database 114 have been previously described above. The method further comprises generating, using the identification module 156, an identifier of the tank 102. Features of the identification module 156 have been previously described above. 20 The method further comprises transmitting an electrical alert signal, using the communications module 108, to the server 110 when the determined amount of fluid in the tank 102 drops below, or rises above, or meets, a predetermined threshold. The method can further comprise transmitting an electrical alert signal, using the 25 communications module 108, to the server 110 when there is an extraction or insertion of fluid from the tank 102, such as an extraction or insertion of fluid from the tank 102 that exceeds a predetermined amount. The method can additionally comprise transmitting an electrical alert signal, using the communications module 108, to the server 110 any time there is an extraction of fluid from the tank 102 to alert a 30 user to an unauthorised extraction or theft of fluid from the tank 102. The alert signal can instantly alert end users to changes in volumes of the fluid in the tank 102. The method further comprises sending details that may include information about height or volume values of fuel in the tank 102, an identifier of the tank including the 35 tank's location and/or the alert signal to the user device 116. The controller WO 2014/136071 PCT/IB2014/059480 22 With reference to figure 2, the device 104 also comprises a controller 160, which comprises or is in communication with the power supply unit 158, the sensor module 154, the communications module 108, and the identification module 156 that have 5 been previously described above. The controller 160 may be configured to control operation of the sensor module 154, the communications module 108, and the identification module 156 The controller 160 may comprise a processor, which is any suitable computing device 10 that is capable of executing a set of instructions that specify actions to be carried out. The term 'computing device' also includes any collection of devices that individually or jointly execute a set or multiple sets of instructions to control aspects of the system including but not limited to the operation of the fluid monitoring system. 15 The controller 160 includes or is interfaced to a computer-readable medium on which is stored one or more sets of computer-executable instructions and/or data structures. The instructions implement one or more of the methods for controlling the operation of the fluid monitoring system. The instructions may also reside completely or at least partially within the controller 160 during execution. In that case, the controller 160 20 comprises machine-readable tangible storage media. Advantageously, the controller 160 is configured to obtain software updates from the server 110 over the communications network 112. For example, the controller 160 may comprise a boot loadable interface that allows new or more sensors to be added 25 to the system. The housing A preferred form of the device 104 is shown in figures 10-12. The device 104 30 comprises a housing 180, which houses the power supply unit 158, controller 160 and the different modules that have been previously described above. The sensor module 154 is located in a separate housing 182 (not shown in figure 11). In other embodiments, the sensor module 154 may be located in the same housing 180 as the other modules. The housing 180 is formed of a polycarbonate material or another 35 suitable polymeric material. The housing 180 may alternatively comprise another suitable material such as aluminium for example. The housing 180 has one or more ports that is/are connectable to the cellular antenna 184, and for connecting to the WO 2014/136071 PCT/IB2014/059480 23 sensor module 154 in the separate housing 182. The GPS antenna is positioned within the housing 180. The housing 180 is further provided with a photovoltaic cell 186 behind a substantially 5 optically transparent face of the housing 180. The photovoltaic cell 186 is configured to charge the power supply unit 158 in the housing 180, when needed. Referring to figure 11, silica-gel 188 may be provided in the housing 180 between the battery 190 of the power supply unit 158 and a wall of the housing 180. 10 The device 104 may also comprise an accelerometer (not shown) for detecting tampering with the sensor arrangement 106 and/or the device 104. For example, an accelerometer may be coupled to the capacitive sensor 140. Alternatively, an accelerometer may be located in or on the housing 180. The controller 160 may be 15 configured to cause the communications module 108 to transmit an alert signal to the remote server 110 when the accelerometer detects movement, such as unauthorised movement, of the capacitive sensor 140 and/or the housing 180. It is not the intention to limit the scope of the invention to the abovementioned 20 examples only. As would be appreciated by a skilled person in the art, many variations are possible without departing from the scope of the invention.

Claims

1. A fluid monitoring system for a tank, the fluid monitoring system comprising: a sensor arrangement at least partially locatable within the tank and having a 5 capacitive sensor configured to generate an electrical capacitance signal relating to an amount of fluid in the tank; a server being configured to receive the signal, and/or information indicating an amount of fluid in the tank based on the signal, from the sensor arrangement over a communications network, and 10 configured to transmit the signal, and/or information indicating an amount of fluid in the tank based on the signal, to a user device remote of the tank over the communications network; and a controller comprising or connected to a communications module, and a sensor module in communication with the sensor arrangement, 15 the communications module being in communication with the sensor module, and configured to transmit the signal, and/or information indicating an amount of fluid in the tank based on the signal, to the server over the communications network.

2. The fluid monitoring system of claim 1, wherein the capacitance signal relates 20 to a level of fluid in the tank.

3. The fluid monitoring system of claim 1 or claim 2, wherein: the capacitive sensor comprises a cylindrical capacitor having an inner cylinder and an outer hollow cylinder that surrounds the inner cylinder, the inner and outer 25 cylinders are substantially coaxial and have a space therebetween; the capacitive sensor is configured to generate the capacitance signal based on a level of fluid in the space between the inner and outer cylinders, and the level of fluid in the space between the inner and outer cylinders corresponds to a level of fluid in the tank. 30

4. The fluid monitoring system of claim 3, wherein the capacitive sensor is locatable at least partially within the tank so that the inner and outer cylinders extend vertically from at or near a top of the tank to at or near a bottom of the tank. 35

5. The fluid monitoring system of claim 3 or claim 4, wherein the outer cylinder is driven with a peak-to-peak AC voltage of between about 20 mV and about 4 V, and a current between about 20 nA and about 20 mA. WO 2014/136071 PCT/IB2014/059480 25

6. The fluid monitoring system of claim 5, wherein the outer cylinder is driven with a peak-to-peak AC voltage of less than about 200mV and a current of less than about 500 pA. 5

7. The fluid monitoring system of claim 1 or claim 2, wherein the capacitive sensor comprises a plate capacitor having two spaced apart plates, and the capacitive sensor is configured to generate the capacitance signal based on a level of fluid in the space between the plates. 10

8. The fluid monitoring system of any one of claims 1 to 7, wherein the communications module comprises a cellular modem and an antenna, and the controller is configured to cause the communications module to transmit the generated signal, and/or information indicating an amount of fluid in the tank based 15 on the signal, to the server over a cellular network.

9. The fluid monitoring system of any one of claims 1 to 7, wherein the communications module comprises a satellite modem and an antenna, and the controller is configured to cause the communications module to transmit the 20 generated signal, and/or information indicating an amount of fluid in the tank based on the signal, to the server via one or more satellites.

10. The fluid monitoring system of any one of claims 1 to 9, wherein the server is configured to transmit the signal, and/or information indicating an amount of fluid in 25 the tank based on the signal, to the user device over a local area network, a wide area network or the Internet.

11. The fluid monitoring system of any one of claims 1 to 10, wherein the controller comprises or is connected to an identification module for generating a unique identifier 30 of the tank, and the controller is configured to cause the communications module to transmit the unique identifier to the server over the communications network.

12. The fluid monitoring system of claim 11, wherein the identification module comprises or is connected to a Global Positioning System (GPS) unit, and the unique 35 identifier comprises a position of the tank. WO 2014/136071 PCT/IB2014/059480 26

13. The fluid monitoring system of any one of claims 1 to 12, wherein the server is configured so that the user device can access the server via a web interface.

14. The fluid monitoring system of any one of claims 1 to 13, wherein the server is 5 configured to transmit the signal, and/or information indicating an amount of fluid in the tank based on the signal, to at least one of a desktop computing device, a laptop, a tablet and a smart phone device over the communications network.

15. The fluid monitoring system of any one of claims 1 to 14, comprising computer 10 memory; wherein the server is configured is to store data representing a plurality of the signals generated over a period of time, and/or information indicating amount(s) of fluid in the tank based on the signals, in the memory; and the server is configured to transmit the signals, and/or information indicating 15 amount(s) of fluid in the tank based on the signals, to the user device.

16. The fluid monitoring system of claims 15, wherein the memory is in the form of a database. 20

17. The fluid monitoring system of any one claims 1 to 16, comprising: a power supply for providing power to one or more of the controller, sensor module, the controller sensor module, sensor arrangement and the communications module; and at least one solar panel or photovoltaic cell for charging the power supply. 25

18. The fluid monitoring system of claim 17, wherein the power supply comprises at least one of a lead-acid battery, a lithium battery, a lithium ion battery and a super capacitor. 30

19. The fluid monitoring system of any one claims 1 to 16, comprising: a power supply for providing power to one or more of the controller, sensor module, the controller sensor module, sensor arrangement and the communications module; and wherein the power supply is a mains power supply. 35

20. The fluid monitoring system of any one of claims 17 to 19, wherein the power supply is substantially located outside the tank. WO 2014/136071 PCT/IB2014/059480 27

21. The fluid monitoring system of any one of claims 1 to 20, wherein the controller is configured to cause the communications module to transmit an electrical alert signal, and/or information related to the alert signal, to the server when there is an 5 extraction of fluid from the tank or insertion of fluid into the tank.

22. The fluid monitoring system of any one of claims 1 to 21, wherein the controller is configured to cause the communications module to transmit an electrical alert signal, and/or information related to the alert signal, to the server when an amount of 10 fluid in the tank drops below, rises above or substantially equals a predetermined amount.

23. The fluid monitoring system of claim 21 or claim 22, wherein the server is configured to transmit the alert signal and/or information representing the alert signal 15 to the user device.

24. A method for monitoring the level of fluid in a tank, the method comprising: generating, using a capacitive sensor at least partially located within the tank, an electrical capacitance signal relating to an amount of fluid in the tank; 20 transmitting the signal, and/or information indicating an amount of fluid in the tank based on the signal, to a server over a communications network; and transmitting the signal, and/or information indicating an amount of fluid in the tank based on the signal, from the server to a user device remote of the tank over the communications network. 25

25. The method of claim 24, wherein the capacitance signal relates to a level of fluid in the tank.

26. The method of claim 24 or claim 25, wherein the capacitive sensor comprises a 30 cylindrical capacitor having an inner cylinder and an outer hollow cylinder that surrounds the inner cylinder, the inner and outer cylinders are substantially coaxial and have a space therebetween; and the method comprises generating the capacitance signal based on a level of fluid in the space between the inner and outer cylinders, the level of fluid in the 35 space between the inner and outer cylinders corresponding to a level of fluid in the tank. WO 2014/136071 PCT/IB2014/059480 28

27. The method of claim 26, comprising locating the capacitive sensor at least partially within the tank such that the inner and outer cylinders extend vertically from at or near a top of the tank to at or near a bottom of the tank. 5

28. The method of claims 26 or claim 27, comprising driving the outer cylinder with a peak-to-peak AC voltage of between about 20 mV and about 4 V, and a current between about 20 nA and about 20 mA.

29. The method of claim 28, comprising driving the outer cylinder with a peak-to 10 peak AC voltage of less than about 200mV and a current of less than about 500 pA.

30. The method of claim 24 or claim 25, wherein the capacitive sensor comprises a plate capacitor having two spaced apart plates; and the method comprises generating the capacitance signal based on a level 15 of fluid in the space between the plates.

31. The method of any one of claims 24 to 30, comprising transmitting the signal, and/or information indicating an amount of fluid in the tank based on the signal, to the server over a cellular network. 20

32. The method of any one of claims 24 to 30, comprising transmitting the signal, and/or information indicating an amount of fluid in the tank based on the signal, to the server via one or more satellites using a satellite modem. 25

33. The method of any one of claims 24 to 32, comprising transmitting the signal, and/or information indicating an amount of fluid in the tank based on the signal, to the user device over a local area network, a wide area network or the Internet.

34. The method of any one of claims 24 to 33, comprising: 30 generating a unique identifier of the tank; and transmitting the unique identifier to the server over the communications network.

35. The method of claim 34, comprising: 35 generating the unique identifier using a Global Positioning System (GPS) unit; wherein the unique identifier comprises a position of the tank. WO 2014/136071 PCT/IB2014/059480 29

36. The method of any one of claims 24 to 35, wherein the user device accesses the server via a web interface.

37. The method of any one of claims 24 to 36, wherein the server transmits the 5 signal, and/or information indicating an amount of fluid in the tank based on the signal, to at least one of a desktop computing device, a laptop, a tablet and a smart phone device over the communications network.

38. The method of any one of claims 23 to 37, comprising the server storing data 10 representing a plurality of the signals generated and logged over a period of time, and/or information indicating amount(s) of fluid in the tank based on the signals, in memory; and transmitting data representing the signals, and/or information indicating amount(s) of fluid in the tank based on the signals, to the user device. 15

39. The method of claim 38, wherein the memory is in the form of a database.

40. The method of any one of claims 24 to 39, comprising providing power to at least the capacitive sensor using a power supply; and 20 charging the power supply using at least one solar panel or photovoltaic cell.

41. The method of claim 40, wherein the power supply comprises at least one of a lead-acid battery, a lithium battery, a lithium ion battery and a super capacitor. 25

42. The method of claim 40 or claim 41, comprising locating the power supply substantially outside the tank.

43. The method of any one of claims 24 to 42, comprising transmitting an electrical alert signal, and/or information related to the alert signal, to the server over the 30 communications network when there is an extraction of fluid from the tank or insertion of fluid into the tank.

44. The method of any one of claims 24 to 42, comprising transmitting an electrical alert signal, and/or information related to the alert signal, to the server over the 35 communications network when an amount of fluid in the tank drops below, rises above or substantially equals a predetermined amount. WO 2014/136071 PCT/IB2014/059480 30

45. The method of claim 43 or claim 44, comprising transmitting the alert signal and/or information representing the alert signal over the communications network from the server to the user device. 5

46. A fluid monitoring system for a tank, the fluid monitoring system comprising: a fluid measuring device having a controller, a sensor arrangement, a sensor module in communication with the sensor arrangement, and a communications module, the controller comprising or being connected to, and for controlling an 10 operation of, the communications module and the sensor module, the sensor arrangement being at least partially locatable within the tank and having a sensor configured to generate an electrical signal relating to an amount of fluid in the tank; a server being configured to receive the signal, and/or information indicating 15 an amount of fluid in the tank based on the signal, from the sensor arrangement over a communications network, and configured to transmit the signal, and/or information indicating an amount of fluid in the tank based on the signal, to a user device remote of the tank over the communications network; and 20 the communications module being in communication with the sensor module, and configured to transmit the signal, and/or information indicating an amount of fluid in the tank based on the signal, to the server over the communications network.

47. The fluid monitoring system of claim 46, wherein the sensor arrangement 25 comprises at least one of a capacitance sensor and ultrasonic sensor, the or each of the capacitance sensor and/or ultrasonic sensor being configured to generate an electrical signal relating to an amount of fluid in the tank.