WO2013068766A2

WO2013068766A2 - Utility meter data recording system

Info

Publication number: WO2013068766A2
Application number: PCT/GB2012/052803
Authority: WO
Inventors: Matthew Middleton
Original assignee: Metermimic Limited
Priority date: 2011-11-11
Filing date: 2012-11-12
Publication date: 2013-05-16
Also published as: GB2496420A; WO2013068766A3; GB201119471D0

Abstract

The present invention relates to a utility meter data recording system. The system comprises a sensor unit which is arranged to attach to a utility meter in retrofit and non-invasive fashion. The sensor unit comprises a magnetic sensor unit and a first processing unit. A receiver unit is further provided which comprises a second processing unit for processing data from the sensing unit. The receiver unit also comprises a transmitting unit for transmitting data to a remote location across a public or private communication network. This provides significant benefits in that a reduced volume of data may be transferred whilst data is processed locally at the sensing unit allowing significant data processing savings.

Description

Utility Meter Data Recording System

In the quest for efficiency and a better use of resources, there is currently a trend towards automatic meter reading (AMR) in the utility industry. The problem the utility companies are faced with is not only the investment required to replace the existing mechanical meters with AMR devices, but the investment in training required to install the new devices and the disruption caused by having to cut off the supply to do so. Not only is the extra investment a concern, but also the fact that the existing mechanical meters are based on technologies that have been improved and perfected during many years and proven to work in the most extreme conditions. Furthermore, mechanical meters, in particular for the case of water or gas meters, do not require a power source to providing accurate and continuous readings, which is potentially a problem with most AMR devices.

Additionally there is the problem of disposal of the old meters, many of which contain mercury, which is an environmental hazard.

The utility industry has currently installed millions of analogue mechanical metering devices for metering water and gas consumption.

The invention is based on taking advantage of the existing stock of mechanical metering devices and converting the mechanical meters into highly versatile AMR devices.

Some water and gas utility meters have built in magnets as part of their mechanisms or they have been equipped with a rotating magnet to enable an external magnetic detector to be used to extract pulses corresponding to the meter movement and implement an AMR solution. Other utility meters having no magnet present attempt to add a magnet to the rotating mechanism in order to enable pulses corresponding meter movement to be determined. The AMR solution provided by most water meter manufacturers utilises a magnetic proximity switch (Reed switch) which opens and closes depending the position of the moving magnet in the meter. The proximity switch output is connected to a data logger or data communications device to store and transmit the resulting pulses as an indication of water and gas consumption. However, this solution suffers limitations in respect of use of a magnetic proximity switch and also requires the transmission of significant quantities of data. According to the present invention there is a utility meter data recording system comprising a sensor unit arranged to attach to a meter in retrofit and non-invasive fashion, the sensor unit comprising a magnetic sensor unit and a first processing unit, the system further comprising a receiver unit comprising a second processing unit for processing data from the sensor unit and a transmitting unit for transmitting data to a remote location across a public or private communication network.

The presently claimed invention provides significant benefits over the prior art. The present invention firstly enables high definition data (readings (i.e. higher frequency readings)) with higher resiliency and lower energy consumption to be transmitted. This is enabled through processing of data at different intervals. Furthermore, processing data locally at the sensing unit allows savings in the amount of data that needs to be transmitted.

The system may beneficially be termed a utility meter sensing device. The system or device is beneficially a data logging system/device.

The amount of data received by the magnetic sensing unit is beneficially greater than the amount of data transmitted to the receiver unit which is beneficially greater than the amount of data transmitted from the receiver unit to a remote location across a public or private network.

The sensor unit is beneficially arranged to be provided in a water impermeable housing. This may be achieved, for example, as known in the art by provision of the electronic components being potted. The housing for the sensor unit may be a sealed housing. The sensor unit beneficially includes a memory. The magnetic sensor unit preferably includes magneto-resistive elements connected in a Wheatstone bridge configuration.

The first processing unit is beneficially arranged to transmit data to the receiver unit.

The sensor unit and the receiver unit are beneficially moveable relative to each other. This is beneficial as it means the sensor unit can be small and can be located easily in the correct position in order to ensure accurate monitoring of the magnetic field as the counter on the meter rotates. The receiver unit can then be beneficially positioned in proximity of the sensor unit, however, the relative configuration and positions of the sensor unit and receiver unit are not fixed. The sensor unit is beneficially positionable in a plurality of locations relative to the receiver unit. The sensor unit is beneficially provided in a first housing and the receiver unit is beneficially provided in a second housing. Beneficially the first housing is positionable in a plurality of locations relative to the second housing. This is important due to the location in which meters and in particular, for example, water meters are found. There is little room adjacent the water meter meaning that in the present invention the size of the sensor unit can be minimised. The sensor unit can beneficially be positioned separately to the receiver unit.

There is beneficially a wired connection between the sensor unit and the receiver unit. However, it will be appreciated that in some embodiments, wireless communication may be achieved. A benefit of wired communication is that power may be transmitted from the receiver unit to the sensor unit thereby again minimising the relative size of the sensor unit.

A power source is beneficially positionable in a plurality of locations relative to the sensor unit and preferably the receiver unit. A third housing is beneficially provided including a power source therein. This third housing is beneficially positionable in a plurality of locations relative to the second housing and first housing. This third housing is beneficially moveable relative to the first and second housings. Again, this provides increased flexibility for positioning in an area of limited space. The power source beneficially provides power to the sensor unit and the receiver unit. The power source may directly provide power to the sensor unit or alternatively, may provide power to the receiver unit which is in series with the sensor unit. This means power need not directly be supplied to the sensor unit.

The sensor unit is beneficially arranged to count pulses representative of the rotations of a meter magnet, and transmit the count (data) to the receiver unit. This may be achieved by transmitting a count after a specific time interval. Alternatively, the sensor unit is arranged to provide a signal to the receiver unit once a predetermined number of pulses from the meter is received.

The first processing unit beneficially further comprises a microcontroller, and preferably further comprises a signal conditioning block including an amplification circuit, and optionally a filtering circuit and optionally includes a threshold detection circuit.

The microcontroller beneficially counts the pulses from the meter.

The receiver unit is beneficially arranged to be located in proximity of the sensor unit. The receiver unit is beneficially arranged to be provided in a water impermeable housing. This may be achieved, for example, as known in the art by provision of the electronic components being potted. The housing for the receiver unit may be a sealed housing.

The power source is beneficially arranged to supply power to the receiver unit.

The receiver unit is beneficially portable.

An attachment arrangement is beneficially provided for attaching the sensor unit to a meter. Suitable attachment arrangements may be, for example, straps, hook and loop type fastening arrangements, and other means of securing the sensor unit to a meter to ensure that the pulses recorded represent the rotations of the meter magnet.

Also according to the present invention there is a method of sensing usage recorded by a utility meter, the method comprising: providing a sensing unit comprising a magnetic sensor unit and a first processor and securing the sensing unit to a meter in a non-invasive fashion; processing data representative of usage recorded by a utility meter by the first processor; transmitting the processed data to a receiver unit; further processing the processed data at the receiver unit to provide secondary processed data and transmitting the secondary processed data to a remote location across a public or private communications network. In one aspect of the invention there is a utility meter sensing device for attaching in a noninvasive fashion to an existing meter in retrofit fashion, the device comprising: a sensor unit (2) comprising a magnetic sensor unit (12) and a first processing unit (10), said sensor unit for attachment to an existing meter (1), a receiver unit capable of collecting readings and status information from the sensor unit, said receiver unit also comprising a second processing unit, said receiver unit also comprising a transmitting unit for transmitting data to a remote location across a public or private network, whereby, the arrangement allows for a reduced need for continuous data transmission between the sensor unit and the receiver unit in order to maintain a predetermined level of data logging frequency.

The first processing unit (10) is beneficially configured to automatically adapt the gain of the magnetic sensor unit (12) according to the existing meter it is attached to.

The sensor unit (2) beneficially comprises memory means (16).

The first processing unit (10) is beneficially capable of automatically storing a

predetermined quantity of logging data, before it sent to the receiver unit.

The sensor unit (2) optionally comprises a signal conditioning circuit (14).

The signal conditioning circuit (14) optionally comprises an amplification circuit (26).

The signal conditioning circuit (14) beneficially comprises a filtering circuit (30). gnal conditioning circuit (14) beneficially comprises a threshold detection circuit (30).

The signal conditioning circuit (14) beneficially comprises an analogue to digital converter The sensor unit (2) beneficially comprises illuminated status indicators (18).

The sensing device beneficially comprises a power supply (22) either within the housing of the sensor unit (2) or remote (e.g. from the receiver unit).

The sensor unit (2) beneficially comprises a wired communication interface circuit (21 ') or alternatively a wireless communication interface circuit (21)

The sensor unit (2) beneficially comprises a wireless (21) communication interface circuit (21 ') and a power supply (22).

The sensor unit (2) beneficially comprises a magnetic sensor unit (12) with magneto- resistive elements in a magnetic sensor connected in a Wheatstone bridge configuration (65).

The invention extends to an automatic meter reading system comprising a utility meter sensing device as hereinbefore described.

The receiver unit is beneficially housed in a second container that is separate from a first container housing the sensor unit (2).

The said second container is beneficially neither contained within, nor is containing the first container.

Also according to an aspect of the present invention there is a sensor unit (2) for a utility meter sensing device comprising: a magnetic sensor unit (12), a processing unit (10), a data storage means (16), a communication circuit (20, 21, 21 ') and a signal conditioning circuit (14). The signal conditioning circuit beneficially comprises an amplification circuit (26).

The signal conditioning circuit beneficially further comprises a filtering circuit (30).

The signal conditioning circuit beneficially further comprises a threshold detection circuit (34).

The signal conditioning circuit beneficially further comprises an analogue to digital converter (35).

The sensor unit beneficially further comprises an internal power supply circuit or alternatively an internal power source.

The communication circuit is beneficially configured as either a wired or a wireless communication circuit.

Also according to an aspect of the present invention there is a method of configuring a sensor unit (2) as defined herein comprising the steps of: providing a data connection to a second processing unit comprising data storage means holding configuration files for different models of meters, downloading the configuration data to the sensor unit, setting up signal conditional parameters on the sensor unit, detecting rotating magnetic field on the meter.

The sensor unit operates in conjunction with the receiver unit (data logger) to form a utility meter sensing system and with the remote server to form a complete AMR system.

The main features and advantages of the sensor unit are:

1. Universal retrofit sensing solution for monitoring of water and gas utility meters with detectable rotational magnetic field with rotations corresponding to the usage of water and gas. The sensor unit is not restricted to a specific utility meter manufacturer or type. Small size enabling easy attachment to water and gas meters without obscuring any part of the meter register to comply with the regulations of the utility companies, Low power consumption enabling the batteries of the external data logger to last for several years. Local intelligence within the sensor unit enabling adaptive control of the gain and filtering of the signal from the ferromagnetic sensor. This enables the sensor unit to operate with different meters regardless of the specific characteristics of their rotating magnets. In addition, it enables the subsystem to recover from strong external magnetic fields which may impact on the accuracy of other magnetic detectors such as the proximity switches provided by utility meter manufacturers. Local storage of accumulated and time stamped data enabling the sensor unit to minimise its interaction with the external data logger and thus, reducing power consumption further. Data storage in non- volatile memory enables the date and time stamped data to be preserved in the event of power loss to the sensor for any reason including tampering with the device. Automatic programming and configuration of the sensor by the external data logger for optimisation of operation, power consumption and programming of events. These events may include frequency of communications with the data logger, alarms for specific water and gas usage levels, data quality and tampering conditions. Simple and remotely controlled commissioning process from a remote server to avoid incorrect installation. LED indicators to provide visual feedback to installers and users about the status of the magnetic sensor and the associated data logger. ATEX Zone 0 approved with all electronic components potted, meaning that the receiver and preferably the sensor unit are sealed to prevent water, gas or moisture ingress.

The present invention has now been described by way of example only with reference to the accompanying drawings wherein:

Figure 1 represents a full AMR system including the sensor unit and receiver unit according to an exemplary embodiment of the present invention and a remote server.

Figure 2 represents an example of a means of attachment of the sensor unit to a water meter.

Figure 3 is a schematic block diagram of the sensor unit according to an exemplary embodiment of the present invention.

Figure 4 is a block diagram of the signal conditioning block in the sensor unit according to an exemplary embodiment of the present invention.

Figure 5 is a block diagram of an alternative implementation of the signal conditioning block according to an exemplary embodiment of the present invention.

Figure 6 is a block diagram of the wired version of communication block according to an exemplary embodiment of the present invention.

Figures 7 and 8 are illustrations of the multiple sensor units connected via wire, or wireless, respectively, to a single data logger using a junction box according to an exemplary embodiment of the present invention.

Figure 9 is a block diagram of the wireless version of the communications block according to an exemplary embodiment of the present invention.

Figure 10 is a schematic flow chart of a sensor unit microcontroller software/system operation according to an exemplary embodiment of the present invention. Figure 11 is a schematic diagram of a typical Wheatstone bridge used in the preferred embodiment of the magnetic sensor.

Figure 12 is an illustration of an exemplary embodiment of the invention in a modular AMR system.

Figure 1 shows a full AMR system (which is attached non-invasively to the gas or water meter (1)), the receiver unit (4) according to the invention plus and the remote server (7) to which data from the receiver unit (4) is transferred. The receiver unit (4) will be termed a data logger (4) in the subsequent exemplary embodiments.

The sensor unit (2) communicates with the data logger (4) via the local communication link (3). The local communication link (3) may be implemented in a number ways including:

Using a direct cable from the sensor unit.

Using a wired network configuration such as Ethernet or RS485 serial network.

Wireless network using proprietary protocols or standard wireless network configuration such as Bluetooth and IEEE 802.15.4 networks.

A combination of the above implementation of the local communication link (3) may be used. This means that multiple magnetic sensor units (2) may be connected to the data logger (4). Some of these sensor units (2) may be connected to the data logger (4) using a wired network, whilst other sensor units (2) may be connected simultaneously to the same data logger using a wireless network.

The data logger (4) preferably communicates with the remote server via the public telephone network, mobile or wired, and the internet via the remote communication link (5). The remote communication link (5) may be implemented in a number of different ways including:

The data logger (4) may include a mobile phone modem (GSM, GPRS or 3G) which communicates uses the mobile phone network (6) as a gateway to access the internet (6). The remote server (7) is connected to the internet (6) and can then communicate with the data logger (4)

The data logger (4) may include a wireless network transceiver that connects to a standard wireless LAN router which will enable it to access the internet (6) via a broadband telephone connection (5)

The data logger (4) may have an Ethernet interface which will enable it to communicate with a standard wired router or broadband model to access the broadband wired telephone link and connect to the sever (7) via the internet.

The data logger (4) may include a standard telephone line wired modem and can be connected to the telephone network (5) to access the internet (6). Accessing the internet will require dialling to an internet service provider (ISP).

The skilled person could also implement the communications link (5) via radio, Wi-Fi or other common forms of wired, optical or radio communication means

The data logger 4 consists of the following building blocks: Microcontroller. Non- volatile memory (NVM).

Communication circuit to implement the local communication link (3) described above.

Communication circuit to implement the remote communication link (5) described above.

Power supply circuit for the mains powered version of the data logger (5) or a battery pack.

The functions of the data logger (4) include:

Control of communications with server (7) and the sensor unit (2) Control of the operation of sensor unit (2)

Provision of memory space for the storage of meter 1 usage data received from the sensor unit (2)

Provision of power to the sensor unit (2) for the wired version of the subsystem. Sensor unit (2)

Prior art systems generally use magnetic proximity switches such as Reed switches. These suffer from the following limitations:

1. Each proximity switch product is dedicated to one type of water and gas meter and model. Considering the large number of meter manufacturers and the wide range of water and gas meter types and sizes, the dedicated proximity solution requires utility companies and other AMR providers to carry a large inventory of different types of proximity switches. Therefore, there is a total lack of a standardised and universal solution.

2. Some mechanical utility meters are not designed for interfacing to proximity

switch products and therefore, cannot be monitored remotely using this technique.

3. Many of the proximity switch products, especially for water meters, are bulky and can be difficult to fit in meters located in confined spaces. In addition, they can cover part of the meter face making it difficult to read the meter register. This may result in the utility companies removing the proximity switch as a result of complaints from their meter reading staff.

4. Proximity switch products do not have any local intelligence or capability to

accumulate the meter reading at the sensor unit. Therefore, a proximity switch has to communicate with an associated data logger continuously and cannot operate independently.

5. The lack of local intelligence prevents the data logger from getting any information relating to tampering with the proximity switch.

6. Only one proximity sensor can be used per meter. Therefore, if two data loggers are required to monitor the meter reading, special wiring to the proximity switch is required whilst it is installed in the field to comply with the regulations of the utility companies.

7. Proximity switches suffer from serious limitations at high flow rates due to mechanical switch bouncing which may result in incorrect number of pulses being reported.

8. As a mechanical switch, a proximity switch has a limited life beyond which it has to be replaced due to mechanical failure, thus adding to the cost of the AMR system.

9. The magnetic field detection sensitivity of utility meter proximity switches is fixed and therefore, if there is a change in the strength of the rotating magnet or internally generated magnetic field due to aging of the meter, the proximity switch is likely to fail in detecting the true figures for water or gas usage.

10. In many cases the proximity switch for a utility meter is already installed on the meter. In such cases, the installation of an AMR system requires the installer to wire the proximity switch cable to the AMR system. This manual can be time consuming and error prone. In addition, water meters in particular are located in deep pits or boundary boxes resulting in further complication in respect of the wiring operation during installation of the AMR system.

Figure 2 shows how the sensor unit (2) of the present invention is attached to the meter non-invasively using a strap (23), and/or an adhesive resin or adhesive pad (21). It illustrates an example of the preferred attachment method to a typical water meter.

Figure 3 shows the sensor unit (2), which is fully integrated and housed in a single small enclosure, preferably made of plastic. The enclosure is preferably transparent or semi- transparent in all or part, allowing green and red light emitting diodes (LEDs) (18) inside the sensor enclosure to be clearly seen.

The building blocks of the sensor unit (2) are shown in Figure 3 and include: Magnetic sensor (12)

The magnetic sensor (12) shown in Figure 3 is preferably a solid state magneto-resistive device. A magneto-resistive material changes its resistance when exposed to a magnetic field. Sensors based on different types of magneto-resistive technology are available commercially.

There are usually four magneto-resistive elements in a magnetic sensor connected in a Wheatstone bridge configuration as shown in Figure 11. The Wheatstone bridge is powered by DC voltage (Vb) and develops a voltage across its outputs (Vo+ and Vo-) when exposed to an external magnetic field. The developed voltage is proportional to the strength or direction of the applied magnetic field depending on the type of magnetic sensor used.

Signal conditioning block (14)

The signal conditioning block (14) in Figures 3 to 6 consists of the following circuits: Amplification circuit (26)

The amplification circuit (26) of Figure 4 amplifies the differential voltage of the magnetic sensor bridge that appears between terminals Vo+ and Vo- (Figure 11), as a result of a change in the magnetic field strength or direction. This differential voltage is usually small and amplification is required to enable its reliable by other parts of the sensor subsystem. This analogue circuit may be implemented as a difference amplifier using one or more operational amplifiers. The preferred implementation is to use an instrumentation amplifier due to its superior performance.

The gain of the amplification circuit is determined by the values of the gain resistors, In this, implementation the gain of the circuit is variable and may be altered under the control of the microcontroller. This is implemented by using analogue switched or digital potentiometers.

The reason for the including a variable gain capability is to enable the sensor subsystem of this invention to be optimised for use with different types of water and gas meter, as the strengths of the magnetic fields generated by the meter types vary considerably. This allows the same unit to cater for a wide range of meters with the consequential advantages in costs due to scale of manufacturing, spare parts and training costs. The variable gain capability is used in two ways in this invention:

1. The first is to receive the optimum gain setting for a specific type of meter from the remote data logging device and store it in the non- volatile memory (16). The microcontroller will then set the gain of the amplification circuit for the sensor subsystem at the time of installation. The gain value will not be changed unless a new value is downloaded and stored in the non-volatile memory.

2. The second approach is to alter the gain adaptively during the operation of the sensor subsystem. This achieved by increasing or decreasing the gain value to achieve optimum operation.

Filtering circuit (30)

The filtering circuit (30) in Figure 4 performs analogue filtering of the amplified sensor signal that appears at the output of the amplification circuit. The purpose of the filtering is to remove unwanted noise resulting from external electrical or magnetic interference. An example of such interference is mains noise from adjacent equipment. Such unwanted noise may affect the operation of the threshold circuit and result in false detections.

The filtering circuit is implemented with operational amplifiers and passive components. The filter configuration and parameters may be fixed or variable. In this implementation variable filter configuration and parameters are proposed to ensure optimum operation. Changing the filter configuration and parameters are achieved by utilising analogue switches and digital potentiometers under the control of the microcontroller. As an example, the filtering circuit can be configured to implement a high pass filter if there are large static magnetic fields, a notch filter to remove 50Hz mains noise or a low pass filter to remove all signal frequency above the maximum rotation speed of the water or gas meter. As with amplification circuit, the filter parameters may be sent by the remote data logger (4) and stored in the non-volatile memory (16) by the microcontroller (10).

Threshold detection circuit (34) The threshold detection circuit (34) of Figure 4 converts the analogue sensor signal representing the strength or direction of the magnetic field to digital pulses. Each pulse may represent a full rotation of part of a rotation for the internal magnet of the water or gas meter. These pulses are fed into a counter circuit or the microcontroller (10) to be counted as representing rotations of the meter and thus, the movement of its least significant register digit.

The threshold detection circuit receives its input from the output of the filtering circuit. The circuit is a comparator circuit that may be implemented with commercially available analogue comparators or an operational amplifier configured as a comparator. Hysteresis is included in the configuration of the comparator to ensure reliable operation by avoiding false triggering from noise and interference. As with amplification circuit, the threshold detection and hysteresis parameters may be sent by the data logger (4) and stored in the non-volatile memory (16) by the microcontroller (10).

Microcontroller (10)

The microcontroller performs a wide range of functions in the sensor unit (2). Its main functions are:

1. Counting the pulses representing the rotations of meter (1) magnet. These pulses are counted for a specific time interval based on a parameter received from the remote data logger. At the end of this time interval, the reading is stored in the non-volatile memory (16) with an associated time stamp. A new pulse counting time interval is started on completion of the previous interval. This time interval represents the meter usage profile resolution. For example, pulses may be counted for 15 minutes before storing accumulated count value. In his case, the meter usage profile resolution is 15 minutes. The time interval parameter may be varied depending on the requirements of the application. It may be received from the data logger (4) and stored in the non- volatile memory (16) of the sensor unit (2).

2. Sending the stored pulse count values with their associated time stamps to the data logger (4) via the communication block 3 of Figure 3. The pulse count data is sent to the data logger (4) at fixed time intervals based on the communication interval parameter that is downloaded to the sensor unit (2) and stored in non- volatile memory (16). This parameter may be changed and a new parameter sent to the microcontroller (10) by the data logger (4).

3. Receiving the parameters for the gain, filtering and threshold detection circuits from the data logger (4) and storing them in the non-volatile memory (16). Figure 4 shows the microcontroller (10) which then applies these parameters to the gain (26) filtering (30) and threshold detection (34) circuits. The parameters will be applied again if a new set of parameters is received from the data logger (4).

4. Generate alarm conditions and communicate them to the data logger (4). These alarm conditions are based on alert parameters received from the data logger (4) and stored in non-volatile memory (16). These alarm parameters may include maximum and minimum water or gas usage level over a specific period of time, device tampering conditions, and malfunction of other parts of the sensor unit (2).

5. Control of the LED indicators (18) to provide diagnostic information during the installation of the sensor subsystem.

Non-volatile memory (16)

The non-volatile memory (NVM) (16) may be implemented as a separate integrated circuit (IC) or as part of the microcontroller. Many commercially available

microcontrollers have built-in non-volatile memory.

The technology of the NVM should enable its contents to be written to and erased for large number of cycles. Such technologies may include EEPROM, flash or other types of multitime time erasable memories.

As stated above, the NVM (16) is used to store the collected meter data with the associated time stamps and the operating parameters for the sensor unit (2) including:

1. Operating parameters for the gain (26), filtering (30) and threshold detection (34) circuits.

2. The meter usage profile resolution parameter and the communication period parameter.

3. Alert parameters for the alarm conditions relating to the meter usage profile and the function of the sensor unit (2).

LED indicators (18)

In this implementation two LED indicators (18) with different colours (for example: red and green) are used to provide diagnostic information during the installation of the sensor unit (2). This information may include:

1. Success of failure of communications between the sensor unit (2) and the data logger (4).

2. Detection of the rotating magnetic field of the water or gas meter (1) to which the sensor unit (2) is attached.

3. Power status of the sensor unit (2), Communication block (20)

The communication block (20) of Figure 3 enables the sensor unit (2) to communicate with the data logger (4). The sensor unit (2) communicates with the data logger for the following purposes:

1. Send the accumulated meter usage data from the NVM (16) to the data logger (4).

2. Send alarm conditions and diagnostic information about the operation of the sensor unit (2) to the data logger (4).

3. Receive operating parameters for the sensor unit (2) circuits from the data logger (4).

4. Receive timing parameters and alarm conditions from the data logger (4).

In this invention the communication block (20) is implemented using a number of methods. These methods can be classified into two categories: Wired communications:

The wired communications methods include a range of direct link methods using metal cables or fibre optic cables. These methods may include a number of different implementations including: a. Direct cable link enabling the connection of a single sensor unit (2) to the data logger (4) as shown in Figure 6.

b. Network cable connection using proprietary or standard network protocols such as Ethernet and RS485. This approach enables more than one sensor unit (2) to be connected to a single data logger (4) as shown in Figure 7. Wireless communications:

The wireless communication approach (Figures 8 & 9) includes a range of radio frequency communication methods. These methods may include a number of different implementations including: a. Proprietary wireless communications circuits using standard frequencies which normally do not require a licence of used at a specified power level such as 2.4GHz. In this implementation a wireless transceiver IC, with associated external passive components and antenna, is included in the communication block (20) of the sensor unit (2). A similar IC will also be included in the data logger (4) circuit to enable the sensor unit (2) to communicate with the data logger (4). The software for the communication protocol may be executed by a processor included in the transceiver IC, a separate processor or the microcontroller (10) of the sensor subsystem. b. Wireless communications based on standard protocols such as Bluetooth, Wireless LAN (WiFi) and sensor networks using the standard IEEE802.15.4 protocol including the Zigbee implementation. With this implementation also a communication IC, with the associated external passive components and antenna, is included in the communication block (20) of the sensor unit (2).

A similar IC will also be included in the data logger 4 circuit to enable the sensor unit (2) to communicate with the data logger (4). The software for the standard communication protocol may be executed by a processor included in the communication IC, a separate processor or the microcontroller (10) of the sensor unit (2).

The choice of the communication type (wired or wireless) is not exclusive and the skilled would realise that the invention could be implemented with both types working in parallel (i.e. the sensor sub system (2) and/or the datalogger itself could be equipped with both wired and wireless communication circuits.

Figures 7 and 8 shows that in both of the above implementations one or more sensor units may communicate with a single data logger depending on the communication protocol used. This offers an implementation with a network of sensors communicating with a single data logger.

Power supply (22)

In this invention, the power supply (22) of the sensor unit (2) shown in Figure 3 is implemented in one of two possible methods:

1. Remote power supply.

In this method the power supply for the sensor unit (2) is provided by the data logger (4) using a separate cable or the communication cable with separate wires for power supply. It is also possible to use alternative approaches to derive power for the sensor subsystem from the signal lines if the communication standard permits this,

2. Local power supply (Figures 3, 6 & 9).

In this method the power block of the sensor subsystem includes a power source. The power source may be implemented using a number of approaches including: a. A primary battery. In this case the battery has to be replaced after its energy is exhausted.

b. A mains derive power source. In this case the sensor subsystem will include a power supply circuit to convert the AC power to the required DC power. c. A secondary battery (rechargeable) that requires charging by an addition circuit such as a mains power supply or an energy harvesting circuit. Energy harvesting may utilise a number of schemes, such as photovoltaic cells or thermo-generators .

Figure 10 shows a flowchart that describes the interaction between the datalogger (4) and the magnetic sub sensor (2) in order to configure the sub sensor with the adequate settings for sensing a specific utility meter.

The process starts at (70) when an operator fitting the device on site powers up the device. Communication is then initiated between the data logger (4) and the magnetic sub sensor (2). If unsuccessful, at (74), an LED light alerts the operator of a problem.

When communication is set up, the operator can select or identify the specific meter 1 to which the AMR system is to be connected to. Once the meter model is selected or identified, which can be done by using a serial number or a model descriptor, or aiding an operator with a picture or image driven selection menu (which can be stored in electronic form on a device, on the sensor (2), on the datalogger (4), on the server (7), or

alternatively in physical form, as for example in a book or catalogue), the configuration data can be downloaded at (76) from the datalogger or the server. The configuration data is then used at (78) to set up the signal conditioning parameters and the magnetic sensor (12) starts detecting the rotating magnetic field of the meter (1). Once the field is detected at (82), if the device is correctly set up, at (86) the LED lights start pulsing with a predetermined ratio to each revolution upon the rotation of the disk on the meter (1) (however, if the field is not detected correctly, an alert is triggered, preferably via the LED lights at (102)).

The microprocessor (10) will then count the magnetic field rotations and determine the pulse counting interval at (86). The count value will be stored at time stamped at (88), and once the communication interval is reached at (96), sent to the datalogger (4) at (98). The data may still be kept and the memory flushed after a predetermined period of time after the data is sent to the datalogger. The count continues/resumes again at (86) and under normal conditions the process continues a cycle through (86), (88), (96) and (98).

If the microprocessor detects a Zero pulse counting value at (92) or detects abnormal conditions that would merit triggering an alert, it triggers an exception alert at (94) and instructs the communication block (20) to transmit the alert to the datalogger at (100).

In turn the data stored at the datalogger (4) can be sent to the server (7) also at predefined intervals (generally and preferably, the latter intervals being less frequent than the intervals at which data is sent between the subsystem (2) and the datalogger (4)). Having data storage means at different stages in the communication chain that spans between the sub sensor (2), the datalogger (4) and the server (7), enables high definition readings (i.e. higher frequency readings), with higher resiliency and lower energy consumption.

The high definition data can be accumulated at the data storage means on the subsystem (2) itself. The fact that the subsystem (2) is also provided with a microprocessor (10), enables data processing locally at the sensor, which allows savings in the amount of data that needs to be transmitted (for example if readings taken every 15 seconds remain constant for 8 hours, then a single reading coupled with a time range can be sent instead of 1,920 single readings, resulting from 4 readings per minute during 8 hours). Accumulated pre-processed data can then be sent in bursts to the datalogger (4). Such bursts can be at predetermined intervals, or alternatively they can be sent on an opportunistic basis (e.g. as soon as communications signal strength reaches a threshold, or as soon as a certain file size is reached).

The other advantage of having a local microprocessor is that any irregular situation can be detected in real time by the local sub sensor (2), and alarms transmitted to the server when that happens, without the need of constant communication with the datalogger (4) or the server (7). To provide equivalent near real time awareness, absence of the local microprocessor would instead require constant communication between the magnetic sensor (12) with the datalogger (4) (and/or the server (7)) so that the remote processing of the data could alert of any irregular situation. That requirement of constant

communication is a constant drain on the energy required to operate the AMR system. The constant drain reduces battery life and that in turn affects reliability and resilience, as a device with an exhausted battery is less likely to be able to successfully send data or an alarm signal, perhaps when it is most needed.

In turn the datalogger (4) can also be used to further process the data and store it, so that it can be sent in predetermined or opportunistic bursts to the Server (7). In order to reduce even more the energy consumption of the AMR system, these bursts between the datalogger and the server are preferably less frequent than the bursts between the subsystem (2) and the datalogger (4). Therefore the datalogger would be consolidating log data from the sensor and transmitting less frequently, which is more efficient because it reduces the communication overhead required for each event in which a transmission needs to be established.

Figure 12 shows the modular construction adopted for the magnetic sensor of the invention. The magnetic subsystem (2) is housed in a small separate container from that of the main datalogging unit 4 housed in a second container (110). They are preferably linked by a cable (118), but the skilled person could also implement the connection via a wireless link (in which case a local power source would be required at subsystem (2)). The datalogging unit comprises a receiver unit for receiving and transmitting data to the sub-system (2) and an antenna (120) for wireless communication with (or transmission to) a server (7) at a remote location via a public or private communication network (5, 6). The communication with the server could, of course, also be a cable connection. The datalogger also comprises a second processing unit.

In the preferred embodiment, the main power source for the datalogging unit is housed in a third separate container (112) and connected thereto via cable (116). This has the advantage of allowing change of batteries without any need of opening the housing that contains the delicate electronics, which is a consideration in harsh environments as those encountered particularly by gas and water meters. Additionally such modular construction with a separate housing for the power source makes "hot swapping" the power source a much easier proposition.

The present invention has been described by way of example only and it will be appreciated by the skilled addressee that modifications and variation may be made without departing from the scope of protection afforded by the appended claims.

Claims

1. A utility meter data recording system comprising a sensor unit arranged to attach to a meter in retrofit and non-invasive fashion, the sensor unit comprising a magnetic sensor unit and a first processing unit, the system further comprising a receiver unit comprising a second processing unit for processing data from the sensor unit and a transmitting unit for transmitting data to a remote location across a public or private communication network.

2. A utility meter sensing system according to claim 1, wherein the sensor unit

includes a memory.

3. A utility meter sensing system according to any preceding claim, wherein the

magnetic sensor unit includes magneto-resistive elements connected in a

Wheats tone bridge configuration.

4. A utility meter sensing system according to any preceding claim, wherein the first processing unit is arranged to transmit data to the receiver unit.

5. A utility meter sensing system according to any preceding claim, wherein the

sensor unit and receiver unit are moveable relative to each other.

6. A utility meter sensing system according to any preceding claim, wherein the

sensor unit is provided in a first housing and the receiver unit is provided in a second housing.

7. A utility meter sensing system according to any preceding claim, wherein the

sensor unit is positionable in a plurality of locations relative to the receiver unit.

8. A utility meter sensing system according to any preceding claim further comprising a power source positionable in a plurality of locations relative to the sensor unit and preferably the receiver unit.

9. A utility meter sensing system according to any preceding claim, wherein the

sensor unit is arranged to count pulses representative of the rotations of a meter magnet and transmit the count to the receiver unit.

10. A utility meter sensing system according to any preceding claim, wherein the first processing unit further comprises a microcontroller, and preferably further comprises a signal conditioning block including an amplification circuit, and optionally includes a filtering circuit, and optionally includes a threshold detection circuit.

11. A utility meter sensing system according to any preceding claim, wherein the

receiver unit is arranged to be located in proximity of the sensor unit.

12. A utility meter sensing system according to any preceding claim, wherein the

receiver unit and preferably the sensor unit are arranged to be provided in a water impermeable housing.

13. A utility meter sensing system according to claim 8, wherein the power source is arranged to supply power to the receiver unit.

14. A utility meter sensing system according to any preceding claim, wherein the

receiver unit is portable.

15. A utility meter sensing system according to any preceding claim, comprising an attachment arrangement for attaching the sensor unit to a meter.

16. A method of sensing usage recorded by a utility meter, the method comprising: providing a sensing unit comprising a magnetic sensor unit and a first processor and securing the sensing unit to a meter in a non-invasive fashion; processing data representative of usage recorded by a utility meter by the first processor; transmitting the processed data to a receiver unit; further processing the processed data at the receiver unit to provide secondary processed date and transmitting the secondary processed data to a remote location across a public or private communication network.