GB2546126A

GB2546126A - Flow detection device

Info

Publication number: GB2546126A
Application number: GB1609091.2A
Authority: GB
Inventors: Bailey Samuel; Gray Greer
Original assignee: HomeServe Ltd
Current assignee: HomeServe Ltd
Priority date: 2016-01-06
Filing date: 2016-05-24
Publication date: 2017-07-12
Anticipated expiration: 2036-05-24
Also published as: GB2546126B; GB201609091D0

Abstract

A water flow detector 10 comprises: a processor 40 that determines a first temperature difference between an ambient temperature (determined by temperature sensor 20) and a temperature of a pipe temperature sensor 16, wherein: the processor generates an indicator of pipe temperature curvature based on outputs of the pipe temperature sensor, identifies a said indicator that exceeds a threshold indicator value and stores a said pipe temperature sensor output received when the curvature exceeds said threshold indicator value. The processor also estimates a temperature of water entering the building based on at least one said stored pipe temperature sensor output; determines a second temperature difference between the estimated temperature and the determined ambient temperature and determines a flow parameter that is a function of a ratio of the first temperature difference to the second temperature difference on order to determine the presence of a flow.

Description

FLOW DETECTION DEVICE

Field of the Invention

The present application generally relates to a water flow detector for detecting a flow in a building water supply system comprising a pipe, a method for detecting a flow in such a building water supply system, and to a method of providing water consumption feedback to a user of such a building water supply system.

Background to the Invention

Being able to detect fluid flow in a pipe has many useful applications. A key one is detecting the presence of leaks in a pipe system. Detecting flow in a system when all taps and valves are closed will usually indicate the presence of a leak in the system being monitored.

Pipe systems can be used to transmit a complete range of fluids from air and other gasses, including combustible gasses to liquids. The liquids can be water, oils or any other liquid. In any pipe system it is important to know if there is leakage in the pipe system.

Many technologies exist for measuring flow. Many involve a mechanical device in the flow e.g. an impellor or nutating disc. In order to fit these, the system must be drained and the device inserted in the pipe. This can be inconvenient. Additionally, there is a risk of leak in the area where the measurement device has been inserted.

Non-invasive measuring techniques also exist - e.g. ultrasound and thermal mass flow measurement. However, ultrasound systems tend to be relatively expensive and do not detect flow velocities less than around 1cm/sec. Thermal mass flow metering requires the fluid to be heated by an element which requires too much power for a system to be battery powered for an extended period of time.

It is an object of some embodiments of the present invention to provide a preferably non-invasive method of detecting fluid flow in a pipe system.

It is also desirable in some embodiments to be able to monitor flow rates - or lack thereof remotely from a central control unit or monitoring station.

Embodiments of the present invention provide a system, device and a method for non-invasively detecting fluid flow in a pipe. Advantageously, the method and system or device may be a low powered method suitable for a battery powered monitor.

Advantageously, an improved flow detector may detect water flow, preferably at least high flow rate, e.g., catastrophic leakages. Such detection with high speed, reliability and/or accuracy, and/or with minimum false alarms to a user is generally desirable. Such an improved flow detector is preferably manufactured at low cost.

For use in understanding the present invention, the following disclosures are referred to: - US2010/206090 A1 (Stack); - EP2840362 (Kamstrup); - WO2015/097407 A1 (GRDF) - US2012/206272 A1 (Borlee); - US9146172 B2 (Trescott); - US7308824 B2 (Trescott); - http://www.aircon.panasonic.eu/GB_en/happening/4679/found to be available at 24.11.15; - http://www.neptuneoceanographics.com/thermal-leak-detection.php found to be available at 24.11.15; - WO01/25743 A2 (Espensen); -WO2011/107101 A1 (Klokker); - US5918268 A (Lukas); and - US5415033 A (Maresca).

Summary

Aspects of the present invention are defined below. Preferred embodiments are defined in the appended dependent claims.

According to a first aspect of the present invention, there is provided a water flow detector for detecting a flow in a building water supply system comprising a pipe, the flow detector configured to determine ambient temperature and having a pipe temperature sensor configured to be mounted adjacent or in thermal contact with a pipe of the pipe system, and a processor configured to determine a first temperature difference that is between the determined ambient temperature and a temperature of the pipe temperature sensor, wherein: the processor is configured to generate an indicator of pipe temperature curvature based on outputs of the pipe temperature sensor; the processor is configured to identify a said indicator that exceeds a threshold indicator value and to store a said pipe temperature sensor output received when the curvature exceeds said threshold indicator value; the processor is configured to estimate a temperature of water entering the building based on at least one said stored pipe temperature sensor output; the processor is configured to determine a second temperature difference that is between the estimated temperature and the determined ambient temperature; the processor is configured to determine a flow parameter that is a function of a ratio of the first temperature difference to the second temperature difference; and the processor is configured to determine presence of a flow based on the flow parameter.

Advantageously, such a water flow detector may be used to detect and indicate (for example internally, audibly and/or visibly on the detector housing, by notification to a user (e.g. to the user’s mobile phone) and/or by notification to an external or central control unit) a flow that is a leak, such a leak potentially being anywhere within the pipe system of the building (e.g., domestic or office building) and generally downstream of the detector. Such an embodiment may be desirable in particular for indicating a high flow or catastrophic leak, e.g., a burst pipe condition, which may be detected when the flow parameter exceeds a threshold. Rapid response to such a leak may be achieved using the pipe temperature sensor, which may be the only temperature sensor and/or may be inside a housing that may further contain the processor (processing means, ECU). Specifically, the pipe temperature sensor may be within the housing, and/or at, on or within a wall of the housing. An attachment (e.g, spring-loaded clip) of the housing for mounting the housing to the pipe may bias the pipe temperatures sensor into direct or close contact with the pipe. Any ambient temperature sensor that is present may be further contained in the housing.

The indicator of pipe temperature curvature may indicate a second differential of pipe temperature change relative to time. In a preferred embodiment, the curvature indicator may indicate extremes in the pipe temperature based on filtering the pipe temperature for peaks in the curvature (which is relative to time). Regardless, the indicated curvature (preferably magnitude thereof) relative to the threshold indicator value, which may be a preset and/or locally stored value, may be used to estimate the water temperature.

The function is preferably a monotonic function of the ratio. An embodiment may determine if the flow parameter is substantially (e.g., exactly) proportional to the ratio of the first and second temperature differences. More specifically, the flow parameter may be determined to be equal to (or at least proportional to) (Tair-Tpipe)/(Tair-Twater), wherein Tair is the determined ambient temperature, Tpipe is the temperature of the pipe temperature sensor and Twater is the estimated temperature of water entering the building.

There may further be provided the water flow detector wherein the processor is configured to determine, based on a plurality of said pipe temperature sensor outputs, when the pipe temperature tends towards (e.g., converges towards) an end value, and to determine the end value, wherein the processor is configured to perform the determination of the ambient temperature based on at least one said determined end value. For example, the ambient temperature may be determined to be substantially (e.g., exactly) equal to the most recently determined end value, or different to that value by a preferably fixed offset.

There may further be provided the water flow detector, wherein the processor is configured to perform said determination of when the pipe temperature tends towards an end value by determining when the pipe temperature tends substantially exponentially towards an end value,

There may further be provided the water flow detector, wherein the processor is configured to estimate the ambient temperature based on, e.g., equal (albeit optionally with a fixed offset) to, a time-based smoothing or average of a plurality of said determined end values.

There may further be provided the water flow detector, wherein the processor is configured to detect at least one maximum and/or minimum of said determined end values and to estimate the ambient temperature based on, e.g., equal to or as an average of, said maxima and/or minima end values.

There may further be provided the water flow detector, comprising another temperature sensor, wherein the processor is configured to perform the determination of the ambient temperature based on at least one output of the another temperature sensor.

There may further be provided the water flow detector, wherein the processor is configured to indicate a flow when the flow parameter (preferably a magnitude thereof) exceeds a threshold flow parameter value, optionally wherein the threshold flow parameter is 0.1, 0.2, 0.9, 0.95 or 0.98.

There may further be provided the water flow detector, wherein the flow indication indicates a high flow leak (e.g., indicates a catastrophic leak and/or does not provide other possible indications, e.g., no flow, low flow and/or medium flow). This may occur for example using a threshold flow parameter of 0.9, 0.95 or 0.98.

There may further be provided the water flow detector, comprising a timer to determine when the flow parameter remains greater than a threshold flow parameter value for a time longer than a threshold time duration, and to indicated presence of a flow responsive to a said determination by the timer, optionally wherein the threshold flow parameter value is 0.1, 0.2, 0.9, 0.95 or 0.98.

There may further be provided the water flow detector, wherein said threshold time duration is at least 20 minutes, more preferably at least one hour. Preferably, the threshold time duration can be varied automatically to be set at a value that is above the duration for which normal flow is usually observed in the building.

There may further be provided the water flow detector, configured to receive input from at least one of a user and a control unit, and to vary the threshold time duration according to said input. Such input may be received wirelessly or through a physical user interface on the water flow detector housing. Such a control unit may be a central control unit or monitoring station that interfaces with a plurality of the water flow detectors preferably located in other buildings.

There may further be provided the water flow detector, wherein the processor is configured to determine a temperature versus time gradient based on outputs of the pipe temperature sensor, and to restart the timer when the determined gradient exceeds a gradient threshold.

There may further be provided the water flow detector, configured to increase the threshold time duration when the flow parameter remains greater than a said threshold flow parameter value for a time that is longer than a threshold time interval, wherein the threshold time interval is shorter than said threshold time duration.

There may further be provided the water flow detector, wherein the processor is configured to estimate the temperature of water entering the building based on (e.g., equal to or proportional to; albeit optionally with a fixed offset) an average of a plurality of said stored temperature sensor outputs.

There may further be provided the water flow detector, wherein the processor is configured to indicate a flow (or leak) when the flow parameter is between a first threshold flow parameter value and a second threshold value, optionally wherein the first threshold flow parameter is 0.1, 0.05 or 0.02 and/or the second threshold value is 0.9, 0.95 or 0.98. The detector may then indicate (e.g., by notifying a user and/or control unit) a medium flow / leak. Additionally or alternatively, the processor may be configured to indicate (e.g. internally to the detector, preferably by similar notification to the user and/or control unit and/or audibly or visibly on the detector housing) no flow/leak when the flow parameter is below a threshold flow parameter value, optionally wherein the threshold flow parameter is 0.1, 0.05 or 0.02.

In preferred embodiment, the processor is configured to determine presence of a leak based on the flow parameter. Any above-mentioned determination of presence of, or indication of, flow may result in or comprise the detector indicating a leak. Preferably the leak is indicated as above, e g., internally, audibly and/or visibly on the housing, notified to a user (e.g., to a mobile phone), and/or to an external control unit. Such a water flow detector may be referred to as a water leak detector. In this regard, ‘flow’ and ‘leak’ may be used interchangeably in the above description of the water flow detector, a leak being a specific form of a flow.

According to a second aspect of the present invention, there is provided a method for detecting a flow in a building water supply system comprising a pipe, the method comprising: determining ambient temperature; using a temperature sensor to detect a temperature of the pipe, the temperature sensor mounted adjacent or in thermal contact with the pipe; estimating a temperature of water entering the pipe, based on output of the temperature sensor; and determining when the pipe temperature remains substantially constant for a period of time greater than a threshold time duration, and if it is determined that the pipe temperature has remained substantially constant for a said period of time, then indicating a flow if: a difference between the estimated temperature and a said pipe temperature detected during said period is less than a first threshold temperature difference; a difference between the ambient temperature and the pipe temperature is greater than a second threshold temperature difference; and a difference between the ambient temperature and the estimated temperature is greater than a third threshold temperature difference.

Similarly as for the first aspect, the flow indication may specifically be an indication of a leak, e.g., the indication being internally, audibly and/or visibly on a detector housing, direct to a user (e.g., to a mobile phone) and/or to an external control unit. Embodiments may be advantageous for rapidly detecting and indicating a high flow or catastrophic leak, e.g., a burst pipe condition.

There may further be provided the method, wherein the threshold time duration is at least 20 minutes, preferably at least one hour.

The first, second and/or third threshold difference may be the same or different. At least one of these differences may be at least 0.2 deg C, preferably at least 0.5 deg C, more preferably at least 1 deg C.

There may further be provided the method, wherein said determining ambient temperature comprises estimating ambient temperature by determining when the pipe temperature tends (or converges) towards an end value, determining the end value, and determining an estimation of the ambient temperature based on at least one said determined end value. For example, the ambient temperature may be estimated as equal to the most recently determined end value, albeit with an optional fixed offset.

There may further be provided the method, wherein said determining ambient temperature is performed based on an output of an ambient temperature sensor.

Advantageously, and similarly as for the first aspect, such flow detection may be leak detection and such flow indicating may indicate a leak. In this regard, and similarly as for the first aspect, it is noted that ‘flow’ and ‘leak’ may be used interchangeably in relation to the above method, a leak being a specific form of a flow.

According to a third aspect of the present invention, there is provided a method of providing water consumption feedback to a user of a building water supply system comprising a pipe, the method optionally using the water flow detector of the first aspect and/or the method of the second aspect, the method of providing feedback comprising: using a temperature sensor to detect a temperature of the pipe, the temperature sensor mounted adjacent or in thermal contact with the pipe; and at least one of: (a) determining when a magnitude of the pipe temperature has a peak and a time differential of the pipe temperature approaching the peak exceeds a threshold differential value, preferably wherein said threshold differential value is negative, and, responsive to a said detection, indicating a short duration water usage; and (b) determining a flow parameter that is substantially proportional to a ratio of a first temperature difference to a second temperature difference, wherein the first temperature difference is between a determined ambient temperature and a said detected temperature of the pipe, and the second temperature difference is between an estimated temperature of water entering the pipe and the determined ambient temperature, measuring a duration for which the determined flow parameter remains above a threshold flow parameter value, and determining how long water has been used for based on the measured duration.

Thus, short and/or long duration usage may be informed to the user, based on the time differential (dTp/dt, where Tp is pipe temperature and t is time) and/or a sufficiently long duration of a sufficiently high flow parameter magnitude (e.g., at least 0.8, 0.9, 0.05 or 0.98 for high flow, or 0.1 or 0.2 for low flow, if the flow parameter value is determined based on a ratio as described above for the first aspect).

The estimate of temperature of the water entering the pipe may be achieved as outlined above for the first aspect, this being generally based estimate the temperature of water entering the building based on stored pipe temperature sensor outputs, e.g., an average of a plurality of stored temperature sensor outputs.

In an optional embodiment, alternatively or additionally to determining how long water has been used for based on the measured duration, (b) may comprise detecting when the flow parameter (preferably magnitude thereof) remains greater than a threshold flow parameter value for a time longer than a threshold time duration and responsive to a said detection, indicating a long duration water usage.

The feedback to the user may indicate that the user is a heavy water consumer or a light water consumer based on a number or frequency of a said plurality of indications of short duration water usage and a number or frequency of a said plurality of indications of long duration water usage. For example, the feedback indicating that the user is a heavy or light water consumer may be based on a ratio of a number or frequency of a said plurality of indications of short duration water usage to a number or frequency of a said plurality of indications of long duration water usage.

Additionally or alternatively, the feedback may be based on comparing at least one said indication of water usage with indications of water usage of other water users, and determining in which quantile of distribution of water usage the user of the building water supply system is in.

Similarly as for the first and second aspects, it is noted that ‘flow’ and ‘leak’ may be used interchangeably in relation to the method, a leak being a specific form of a flow.

Any one or more of the above aspects may be combined, with/without any of the optional features, within any of the embodiments (e.g., fluid flow detector, leak detector and/or water supply system comprising such a leak detector) disclosed below.

An embodiment of a fluid flow detector is for detecting fluid flow in a pipe system, the detector having a first temperature sensor to detect ambient temperature, a second temperature sensor configured to be mounted adjacent or in thermal contact with a pipe of the pipe system, a processing means configured to determine a temperature difference between the first and second temperature sensors and if the temperature difference is below a predetermined threshold for a predetermined period, to determine that no fluid if flowing in the pipe system. The processing means may comprise one or more processors.

The inventor has determined that in a pipe system, if there is no flow of fluid in the pipe system, the temperature of the fluid in the pipe, sufficiently distant from any other sources of heating or cooling, will approach ambient temperature over a period of time. By determining the ambient temperature of air or other medium around the pipe system and the temperature of the fluid in the system, it is possible to determine if fluid is flowing in the pipe system. If the temperature of the fluid in the pipe system is monitored over a period and compared to ambient temperature and the two values approach each other and maintain a predetermined difference or less for a predetermined time, a no flow condition can be determined to exist. If the temperature differences remain outside a predetermined set of parameters, it can be assumed there is a flow in the pipe system.

If on the other hand, the difference in temperatures between the “ambient” and the fluid in the pipe is greater than a predetermined value for a predetermined period, there can be assumed to be a flow condition.

The fluid flow detector may comprise a single device or a system having more than one device. Thus, references to a device throughout this specification are interchangeable with references to a system.

There may be provided the device in which a zero flow condition is determined if the temperature difference between the temperature sensors is less than about 1.0 deg C (degrees Centigrade) for at least one hour. (The fluid flow detector being referred to as a device; as noted the detector may be a system comprising more than one device).

There may further be provided the device in which a zero flow condition is determined if the temperature difference between the temperature sensors is less than about 0.5 deg C and preferably (i.e., optionally) less than 0.3 deg C for at least one hour.

There may further be provided the device in which a zero flow condition is determined if the temperature difference between the temperature sensors is less than 0.1 deg C for at least one hour.

The determination of a zero flow condition is particularly useful in a number of environments or installations such as domestic, office or industrial water systems, reserve or standby fluid pipe systems such as might be employed in emergency or backup systems.

In such systems there are periods when it can be anticipated there will not be any fluid flow. This lack of flow will provide sufficient time for the fluid temperature to converge to the ambient temperature. Such periods can be, for example, overnight or at weekends.

There may further be provided the comprising means in which in an alarm signal is generated if the temperature differences fall outside predetermined parameters for a predetermined time. Such a means may be implemented in various ways, for example using an audible and/or visual indication and/or communication to a remote entity, and may be described as an alarm generator.

In one example, ideally suited to such a system is a domestic or office water supply system. In these systems, water is supplied from a mains system normally entering a building from under the ground. In normal circumstances, when fluid is flowing, there will be a temperature difference between the incoming fluid and the temperature of the air surrounding the pipe several centimetres from the ground. By monitoring these two temperatures over a period of time their convergence can be monitored and providing the difference in the determined temperatures are less than a predetermined value for a predetermined period, a leak free condition can be considered to be achieved. However, if there is a continuing small temperature difference, particularly during a time when no flow would be expected, a leak condition can be considered to arise and an alarm or alert can be raised.

Preferably, the temperature sensor used to detect the water temperature is in good thermal contact with the pipe. Alternatively, if the sensor is in close proximity to the pipe it may be possible to measure the temperature of the fluid in the pipe with sufficient accuracy to enable a control and monitoring unit to detect a temperature difference.

Various mechanisms can be envisaged to ensure the pipe sensor is in good contact with the pipe. These could include biasing the sensor so that it is biased into contact with the pipe by spring or other biasing means. Alternatively, and more advantageously from the device construction point of view, a spring clip can be used to ensure the device is securely clipped to the pipe and can be arranged to ensure the temperature sensor is in good contact with the pipe. Alternatively a strap or other tie mechanism could pass around the pipe, securing the sensor to the pipe. This could apply a pressure maintaining the thermal contact with the pipe.

The device is provided with an Electronic Control Unit (ECU) or a microcontroller which can be configured to have one of many arrangements. It can be provided with a large number of pre-programmed calibrations and measure temperatures and signal alarms according to a set of pre-programmed instructions.

Alternatively, each device can be provided with an ECU which is capable of calibrating the measurements obtained from the two temperature sensors and be further calibrated according to the type and details of the installation. This latter is advantageous in that it should ensure greater accuracy and reduce the number of false alarms.

The ECU needs to be capable of monitoring the outputs provided by each of the temperature sensors and comparing them over an extended period of time to determine any differences and whether the differences fall within pre-determined thresholds. If the appropriate criteria are satisfied an alarm signal can be generated.

In a domestic or office environment, the temperature of the incoming cold water in a water supply varies through the year, but is typically different to room temperature due to the water being chilled or heated by the earth surrounding the subterranean supply pipes. Water flowing through the pipes will then tend to chill the pipes (or warm them, depending on the climate or time of year) to a measurable degree, even at very low flow rates (down to 5ml/min). This phenomenon can be used to detect whether or not water is flowing in the pipe.

By measuring the temperature difference for an extended period of time, the presence (or absence) of flow can be detected. For a typical domestic dwelling, periods of zero flow (e.g. at night) can be expected. If flow is detected, it probably indicates the presence of a water leak or a dripping tap or valve in a toilet. A user can then be alerted to the presence of the leak so they can fix the problem, reducing water damage to a property and reducing water wastage.

It is also now well known that in modern domestic environments it is increasingly common to operate water consuming domestic appliances, such as washing machines or dishwashing machines, at night in order to benefit from cheaper energy tariffs available. Operation of such appliances will result in a rapid and significant flow of water at periods during the operation cycle. This rapid flow will cause a sudden change in temperature of the water in the pipe. The monitoring system may therefore be provided with means, generally comprising a processor and/or at least one temperature sensor, to detect the sudden and significant temperature change and an ECU may be programmed to ignore or discount such sudden surges and not produce an alarm condition.

In such circumstances the monitoring system may be triggered to reset itself so it again waits for the temperatures to converge, and begin monitoring afresh.

There is further provided a leak detector comprising the fluid flow detector, wherein the leak detector is configured to indicate a leak detection if the temperature difference is not below a predetermined threshold for the predetermined period, wherein the leak detector is configured to indicate a leak of the pipe system preferably wherein the pipe system is of a domestic building or of an office water supply system.

Advantageously, the leak detector is for detecting a leak in a domestic building or office water supply system comprising a pipe, the leak detector having a first temperature sensor detecting ambient temperature, a second temperature sensor configured to be mounted adjacent or in thermal contact with a pipe of the pipe system, and a processor configured to determine a temperature difference between the first and second temperature sensors, wherein the processing means is configured to determine a heat transfer indicator based on a ratio of an indicator of time gradient of the sensed pipe temperature relative to the determined temperature difference between the first and second temperature sensors, wherein said temperature of the pipe is sensed by the second temperature sensor, the processing means further configured to determine if the heat transfer indicator is below a predetermined threshold for a predetermined period and to: if the heat transfer indicator is below a predetermined threshold for a predetermined period, indicate a leak detection; and/or if the heat transfer indicator is not below a predetermined threshold for a predetermined period, indicate absence of a leak detection.

The processing means may be configured to determine a best fit exponential function to the sensed temperature of the pipe and determine said indicator of time gradient of temperature of the pipe on the basis of said exponential function. A preferred embodiment of the leak detector implements the above leak detection based on if the temperature difference is not below a predetermined threshold for the predetermined period and further implements the above leak detection based on the ratio of an indicator of time gradient of the sensed pipe temperature relative to the determined temperature difference. The two methods - the first based on if the temperature difference is not below a predetermined threshold for the predetermined period, the second based on the ratio of an indicator of time gradient of the sensed pipe temperature relative to the determined temperature difference - may be combined in an embodiment, e.g., may run in parallel to provide redundancy and/or to improve robustness. If either algorithm predicted a leak a number (1 or more) of times then a leak could be reported for example by outputting an alarm. In an embodiment, a result from either method may over-ride the result from the other, for example where the method based on gradient indicator is deemed more reliable, this may over-ride any leak detection result from the temperature difference-based method. In an embodiment where both methods are run in parallel, an alarm may be reported if either detect a leak. Alternatively, the temperature difference method could be run to detect low flow leaks when the starting temperature difference is high (e.g. above 0.5 or 1C), and the gradient based method run when the starting temperature difference(s) are low (e.g. below 0.5 or 1C). The gradient based method could be run to pick up high flow rate leaks when the temperature difference is high.

The processing means may be configured to monitor an indicator of a second order derivative with respect to time of the pipe temperature sensed by the second temperature sensor and to detect if said second order derivative indicator has been below a predetermined value for a predetermined time duration, wherein the leak detector is configured to perform, in response to a said detection that said second order derivative indicator has been below a predetermined value for a predetermined time duration, said determining if the temperature difference is below a predetermined threshold for a predetermined period or said determining if the heat transfer indicator is below a predetermined threshold for a predetermined period. This may be advantageous, for example to allow a lack of water usage for a period to be established before allowing leak monitoring to begin.

The leak detector may be configured to detect when an indicator of a second order derivative of the pipe temperature with respect to time exceeds a predetermined value and to start a said predetermined period in response to a said detection. This may be advantageous for example if is desired to ensure that a predetermined period for monitoring for a leak is always started from a last water usage detection.

Furthermore, the leak detector may be configured to vary the predetermined threshold dependent on a said temperature difference at the start of the predetermined period. Such variation may be implemented at a unit that is remote from the pipe, for example dependent on a weather forecast.

The leak detector may be configured to determine a time when the pipe should have no flow in the absence of any leak and, if there is any residual temperature difference between the pipe and ambient at that time, adjust a said predetermined threshold dependent on said residual temperature difference. This be may be viewed as a form of calibration. The determination of the time when the pipe should have no flow may be based on existing data stored internally, e.g, the leak detector already knows that no flow should occur at, e.g., 3am, each night, or the leak detector may learn such a time based on information received from a remote entity. Preferably the leak detector monitors for such a residual temperature difference only during a set period, e.g., the first 24hrs, of the device being powered up, before normal leak monitoring operation is allowed to begin.

Preferably, the leak detector comprises an alarm generator to output an alarm in response to at least one said leak detection, the leak detector configured to detect a change in the sensed pipe temperature and to disable the alarm generator until a predetermined number of said changes in the sensed pipe temperature (preferably relative to the ambient temperature) has been detected, wherein the predetermined number is at least one, preferably wherein the change detection comprises a detection that a pipe temperature change (preferably relative to the ambient temperature) and/or a rate of change of the pipe temperature (preferably relative to the ambient temperature) exceeds a respective predetermined value. The detection of the predetermined number may require such detection within a predetermined time interval, e.g., may require 3 such changes to be detected during a time span of 24hrs. Advantageously, the requirement to detect such a number of changes may ensure that the leak detector only begins to monitor for leaks after it is established with reasonable certainty that the leak detector is actually fitted to a pipe. A leak detector may comprise an alarm generator to output an alarm in response to at least one said leak detection and comprising a user interface to enable a user to stop the alarm, the leak detector configured to store internally and/or communicate externally that, and preferably also when, the alarm has been stopped. Thus, a third party may be able to establish that the alarm has been reset.

Preferably, the leak detector comprises an alarm generator to output an alarm in response to a predetermined number of said leak detections, wherein said predetermined number is at least two and each said leak detection occurs during a respective one of successive said predetermined periods. Such an embodiment may effectively filter leak detections to prevent or reduce false alarms.

The leak detector may comprise an alarm generator to output an alarm in response to at least one leak said detection during a said predetermined period, the leak detector further configured to disable a said alarm output (preferably for a predetermined time duration) by the alarm generator if: a change of at least the sensed pipe temperature (preferably relative to the ambient temperature) indicates presence of a leak during a first said predetermined period; and then a change of at least the sensed pipe temperature (preferably relative to the ambient temperature) indicates absence of a leak during a second said predetermined period, wherein the first and second said predetermined periods are successive said predetermined periods, and optionally if a change of at least the sensed pipe temperature (preferably relative to the ambient temperature) indicates presence of a leak during a third said predetermined period, wherein the second and third said predetermined periods are successive said predetermined periods. Thus, false alarms may be prevented or reduced based on pattern detection, e.g., leak - no leak, leak - no leak - leak, or a longer pattern. The successive predetermined periods may comprise for example successive night periods, e.g., starting at 3am on each of successive nights. In an embodiment, the leak/no leak decision may not be a binary decision. It could be based on an average of the temperature difference over several measurements. For example, if there are two successive measurements, one where the temperature difference is significantly above the threshold and one where it is only slightly below, the average difference may then be above the threshold and the alarm can be raised. Alternatively the detector may monitor the average temperature difference for a given installation, and if it changes by an amount above a threshold, then to raise an alarm.

An embodiment of the leak detector comprises an alarm generator to output an alarm in response to at least one said leak detection, the leak detector configured to detect if the sensed pipe temperature is substantially constant for a predetermined time duration at a temperature that differs from the sensed ambient temperature by more than a predetermined amount and, in response to the detection, immediately trigger the alarm generator to output a said alarm, preferably wherein said predetermined period is at least one hour. Such an embodiment may be advantageous for detecting an undesirable high flow condition, e.g., with water flow similar to for running a bath. (In comparison, a low flow condition occurs for example where a tap is left dripping). The embodiment may be of advantage for detecting a burst pipe. For a burst pipe or other high flow condition detected by such an embodiment, the pipe temperature may tend to the maximum (minimum) draw down temperature depending on whether the water temperature is higher (lower) than ambient and may on the day. Some example values of the substantially constant temperature difference may be 2-3 degrees, e.g., 1, 2, 3, 4, 5 or 10 deg C.

There may further be provided the leak detector comprising an alarm generator to output an alarm in response to at least one said leak detection, wherein the processing means is configured to detect when a change in the sensed pipe temperature immediately follows a predetermined time duration during which the sensed pipe temperature tracks the sensed ambient temperature, wherein the predetermined time duration preferably comprises at least a predetermined number of 24 hour periods (e.g., seven, i.e., 1 week) and the predetermined number is at least two, wherein the processing means is configured to immediately trigger the alarm generator to output a said alarm in response to a said change detection, preferably wherein the change detection comprises a detection that a pipe temperature (preferably relative to ambient temperature) change and/or a rate of change of the pipe temperature (preferably relative to ambient temperature) exceeds a respective predetermined value. The temperature tracking may be caused by a no flow condition and may be identified by detecting there is a substantially constant, e.g., zero or more, offset between the pipe and ambient temperatures over the predetermined time duration. Such a leak detector may be effectively establish that a user is on holiday (wherein there may be no flow so that the pipe and ambient temperatures track) and on this basis establish that a new flow detection is likely to be caused by a leak. This may be particularly advantageous for detecting a likely burst pipe. Example values of such an offset between the pipe and ambient temperatures are, e.g., 2-3 degrees, e.g., 1, 2, 3, 4, 5or 10 degrees.

The leak detector may comprise an alarm generator to output an alarm in response to at least one said leak detection, wherein the processing means is configured to detect a crossing point of the sensed pipe temperature and the sensed ambient temperature, and to disable (for at least a predetermined time duration and/or for the duration of a concurrent predetermined period during which monitoring for a leak is occurring) the leak alarm generator when such a crossing point is detected. This may prevent or reduce a false alarm that may otherwise be generated due to a thermal mass lag effect.

Preferably, the leak detector is configured to process an output of the second temperature sensor to filter out periodic temperature changes during a said predetermined period and to thereby provide a filtered pipe temperature profile, wherein the sensed pipe temperature for use in leak detection is a temperature of the profile, preferably wherein the filtering reduces an effect of a Torbeck valve on a said leak detection. Such periodicity may be every e.g., 5 or 10 minutes, or every, e.g., 5 hours. To identify such periodic temperature changes preferably a mask is applied to filter out periodic changes that may occur from normal daily water usage, e.g., events occuring every 24 hrs.

There may further be provided the leak detector comprising an arrangement having said temperature sensors and the processing means, the leak detector further comprising a remote unit, wherein the leak detector is arrangement to transmit to the remote unit data points comprising at least one of: at least one sensed pipe temperature, preferably including a temperature of the pipe as sensed at the start of a said predetermined period; at least one sensed ambient temperature, preferably including a temperature of the ambient as sensed at the start of a said predetermined period, wherein the remote unit is arranged to vary a said predetermined threshold on the basis of the transmitted data points. Either or both such starts of a said predetermined period is preferably a time where water use was last detected.

There may further be provided a leak detector having an electronic control unit configured to determine whether the device is subject to a repeated heating or cooling from an external heat source or sink, wherein a said heating or cooling comprises at least two successive crossing points of the sensed pipe and ambient temperatures, preferably wherein the electronic control unit is configured to alert a user that it is unable to determine if a leak condition is present.

Generally, the repeated heating or cooling is intermittent. For example, the external heat source/sink may be a central heating system water pipe through which hot water flows intermittently. The crossing points may occur when the pipe temperature rises (falls) to cross the ambient temperature and then falls (rises) to cross back over the ambient temperature. Preferably an ECU of such a fluid flow detector is configured to determine whether the device is subject to the repeated heating or cooling and/or to alert the user that it is unable to determine if a leak condition is present.

Such detection of whether the device, e.g., the second temperature sensor for detecting the pipe temperature, is subject to a repeated heating or cooling may be useful where a water pipe is placed next to a heating pipe, for example when the heating comes on intermittently thus affecting the temperature of the neighbouring pipe being monitored for leak detection. This may be similar to where the pipe is next to e.g. a concrete slab such that the ambient and pipe temperatures may not converge within a predetermined period of time so that it may be more difficult to determine whether or not there is a leak. An embodiment may determine if the pipe temperature is always different to, e.g. sits below, the ambient temperature. In this case the temperatures may not converge due to a leak or continual thermal conduction from the pipe to a high heat capacity object such as ground.

In this regard, it is noted that it is generally necessary or at least advantageous to have seen a convergence between the ambient and pipe temperatures before deciding that a lack of convergence means anything regarding presence or absence of a leak. A preferred leak detection system may therefore be configured to only be able to provide a leak detection alarm (e.g., visual and/or audible notification or alert) if it has previously detected that a predetermined period has elapsed with no flow.

An embodiment comprises a water supply system comprising the leak detector and at least one water pipe, preferably wherein the leak detector is attached to a said water pipe where water enters a building and/or at a stop cock.

Embodiments of the invention may comprise a controller which includes a microprocessor, working memory and program memory coupled to one or more of the components of the system. The or each processor may be implemented in any known suitable hardware such as a microprocessor, a Digital Signal Processing (DSP) chip, an Application Specific Integrated Circuit (ASIC), Field Programmable Gate Arrays (FPGAs), etc. The or each processor may include one or more processing cores with each core configured to perform independently. The or each processor may have connectivity to a bus to execute instructions and process information stored in, for example, a memory.

Embodiments of the invention may further provide processor control code to implement the above-described system and control procedures, for example on an embedded processor. The code may be provided on a carrier such as a disk, CD- or DVD-ROM, programmed memory such as read-only memory (Firmware), or on a data carrier such as an optical or electrical signal carrier. Code (and/or data) to implement embodiments of the invention may comprise source, object or executable code in a conventional programming language (interpreted or compiled) such as C, or assembly code, code for setting up or controlling an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array), or code for a hardware description language such as Verilog (Trade Mark) or VHDL (Very high speed integrated circuit Hardware Description Language). As the skilled person will appreciate such code and/or data may be distributed between a plurality of coupled components in communication with one another. A possible embodiment of the device is described below.

An example of such a device will include two high precision temperature sensors, a power supply and an electronic control unit (ECU) enclosed in a housing which is connected to a pipe. One temperature sensor is positioned such that it is in good thermal contact with the pipe, at sufficient distance from any heat sinks or sources, including the earth or any other conduits or passages that the pipe has passed through, so that they do not unduly heat or cool the pipe, it is also sufficiently close to where the pipe leaves the earth, passage or conduit when so that any fluid flowing in the pipe during a leak does not have time to reach ambient temperature before it reaches the sensor. The other temperature sensor is positioned such that it has good thermal contact with the ambient air in the general region of the pipe temperature sensor, but not so close its measurements will be unduly affected by it. Preferably it is shielded from any heating or cooling drafts or air currents which might affect the values. The sensors are connected to an ECU or microcontroller which monitors the measurements over a period of time to determine whether there is a flow in the pipe. The microcontroller can then issue an alert via a suitable method if flow is present when it is outside the predetermined parameters or is not expected.

Under normal operation (no leaks present), if all taps and valves on the circuit are closed such that there is no flow, the temperature of the pipe (and its contents) will slowly tend to converge to that of the ambient air. For a typical domestic water pipe it will take around 3 hours for it to be within 0.1C of the air temperature.

If there is a flow in the pipe, the temperature of the pipe will not tend to equal the air temperature. For larger flow rates, the pipe temperature will stay close to the incoming fluid temperature, whereas for slower flow rates, the pipe temperature will stay closer to the ambient temperature than in the other case.

The ECU or microcontroller can be programmed to detect the temperature differences and monitor them over time. It is clearly advantageous that if there is a sudden increase in flow rates caused by say the flushing of a toilet or drawing water for a bath or shower, that the system does not signal an alarm. Following such an event, the ECU will normally be programmed to restart the monitoring period.

Advantageously and optionally, the ECU will be provided with means, e.g., clock and/or calendar, to determine the time of day and more preferably, the actual date. The ECU programmed in this manner should be able to determine that a period of low or zero fluid flow is to be expected, as would be the case in the middle of the night.

It will also be apparent that the temperature differences between the ambient temperature and pipe temperature will also vary according to the material from which the pipe is made and its diameter. For larger diameter pipes containing more liquid it will clearly take longer for them to approach and reach ambient temperature than a smaller diameter pipe. Also, it will be appreciated that pipes made from metals such as copper, steel or lead will conduct heat far more efficiently than pipes made from plastics materials. Therefore a different rate of temperature convergence can be expected in view of such differences.

Advantageously, the ECU or microcontroller can be calibrated and set to take account of such variations.

Brief Description of the Drawings

Embodiments of the invention will now be described with reference to the accompanying drawings in which: FIG 1 shows an example of a flow detector device attached to a pipe. FIG 2 shows a top view of the detector device. FIG 3 shows a side elevation indicating how contact is made with the pipe. FIG 4 shows a block diagram of the inter-connection of the components. FIG 5a is a graph showing the temperature of the pipe and the ambient air over a 5 hour test period with no flow in the pipe where the water is warmer than ambient. FIG 5b is a graph showing the temperature of the pipe and the ambient air over a 5 hour test period with a small amount of flow in the pipe where the water is warmer than ambient. FIG 6a is a graph showing the temperature of the pipe and the ambient air over a 5 hour test period with no flow in the pipe where the water is warmer than ambient. FIG 6b is a graph showing the temperature of the pipe and the ambient air over a 5 hour test period with a small amount of flow in the pipe where the water is cooler than ambient.

Fig 7 is the block diagram of the system where a shut off valve is used to shut off the water supply in the event of a leak being detected.

Fig. 8a is a graph showing the temperature of the pipe and the ambient air over a test period with no flow in the pipe where the water is warmer than ambient.

Fig. 8b is a graph showing the temperature of the pipe and the ambient air over a test period with a small amount of flow in the pipe where the water is warmer than ambient.

Fig. 9a is a graph showing the temperature of the pipe and the ambient air over a test period with no flow in the pipe where the water is warmer than ambient.

Fig. 9b is a graph showing the temperature of the pipe and the ambient air over a test period with a small amount of flow in the pipe where the water is cooler than ambient.

Figs. 10 and 11 show further examples of temperature-time traces.

Fig. 12 shows an example implementation of a fluid flow detector system/device.

Fig- 13 shows an example computing device or system on which at least the processing means, e.g., electronic control unit, of an embodiment of the invention may be implemented.

Fig. 14 shows an example high flow graph of pipe and air temperatures.

Fig. 15 shows an example of a high flow graph showing measured pipe temperatures.

Fig, 16 shows an example of a water leak detector, optionally comprising a timer T1 and/or omitting an ambient temperature sensor.

Detailed Description of Preferred Embodiments

Embodiments of the invention will now be described in more detail with reference to the drawings in which like references refer to like features in the various figures. FIG 1 shows an example of a fluid flow detection device according to an embodiment of the present invention. The device is contained within a housing 10, is attachable to a pipe 12 by means of a biasable pipe clip 14. This particular device is used as a water flow detector for a domestic or office environment. Larger scale devices and housings could be used for a factory, but frequently factories operate for large portions of a day and may not have long enough periods of zero flow for satisfactory operation and require more sophisticated and complex monitoring systems. FIG 2 shows a top view of the device which may conveniently include indicator or display elements to show the state of operation of the device. These could include a system operation indicator 22 an alarm indicator 24, or a loud speaker 26 from which an audible alarm could be emitted. FIG 3 shows a side elevation of the housing 10 secured to a pipe 12 by connector 14. A temperature sensor 16 extends from the case of the housing and is shown contacting the pipe 12 to determine the outer temperature of the pipe 12. FIG 4 shows a block diagram of the components comprising the device and their inter connections. The housing 10 encloses an electronic control unit (ECU) 40 for monitoring temperatures, time and controlling the device. The device is powered by a power supply 42, normally comprising one or more batteries. The selection of batteries will be chosen to provide long life in the environment in which the device is installed. Temperature sensor 16 is shown as in contact with pipe 12 to measure the temperature of the pipe. Ambient temperature is measured by temperature sensor 20. An alarm unit 46 can include a visible alarm means, typically an LED, or an audible means or driver therefor. For some applications, a wireless connection 48 will also be provided, so enabling the device to periodically transmit data to a remote station and so send an alarm signal when needed. The wireless connection could also receive information or data from a remote station.

In another example embodiment of the invention, the power could be supplied by a mains network. In a further example, a more sophisticated power supply system is provided in which the power supply comprises a mains power supply connected with one or more batteries.

Suitable temperature sensors are for example Resol FKP6 PT1000 temperature sensors. Other devices which have been found to work well can be found in the class of PT1000 platinum sensors.

Figure 5a shows a graph of the temperature measured by each of the sensors over a period of time. The graph shows temperature along the Y axis, and time along the X-axis. The dashed line is a trace of ambient temperature over a selected measurement period, in this example 2-3 hours. The solid line shows how the temperature of water in the pipe varies. In region A, a significant flow has been occurring and the water temperature is significantly higher than the ambient temperature. (This can occur in some tropical climates and late in summer when the ground temperature has risen and is consistently (during the course of a day or so) higher than the general air temperature. The spikes indicate how the temperature has risen sharply as a significant draw down occurs and show the temperature has begun to fall towards ambient. This draw down could be a flushing of a toilet or water for a basin or sink.

In Region B, the water temperature can be seen to fall towards ambient.

In Region C, the temperatures are considered to be within the predetermined conditions and so equal. This condition would indicate there is no flow of water in the system.

Figure 5b shows a similar situation to the one in Figure 5a, but in this example, the two temperatures never quite converge, as can be seen in all regions. From this it can be concluded that there is always a flow and there is a leak in the system.

Figure 6a shows a graph of the temperature measured by each of the sensors over a period of time. The graph shows temperature along the Y axis, and time along the X-axis. In this example the ambient temperature shown by the dotted line is higher than the incoming water pipe temperature shown by the solid line. Such situations can arise in cold or temperate climates where ground temperatures can be and frequently are lower than the ambient air temperature. In region A tap on off events can be seen as indicated by the spikes in the pipe temperature. In region B the pipe temperature is rising towards the ambient temperature. In region C the two temperatures are more or less convergent, and so satisfying the criteria set out that the temperatures must be within narrow bands. This convergent set of temperatures would indicate that there is no leak in the system.

Figure 6b shows the ambient temperature (shown by the dotted line) is higher than the incoming water pipe temperature shown by the solid line. The various spikes in Region A show how the inlet water temperature falls as water is drawn off through the system, and then rises towards ambient, until the next draw off, when it falls again. In region B, there is a prolonged period without a significant draw off of water. However, as can be seen in Region C, the two temperatures do not converge closely within the predefined limits, always maintaining a difference of temperature T. Providing this temperature difference (or temperature) is greater than a predetermined value, which can vary according to the geographical and physical location of the device, it can be assumed there is a leak in the system. If it is a significantly large temperature difference (or temperature), as in this example, it can be assumed there is a reasonable flow rate of leak - rather than just a dripping tap. In some regions, a temperature difference of approximately 1°C will be expected, but more commonly the temperature difference will be expected to remain below approximately 0.3°C and preferably 0.1 °C for a no flow condition to exist.

An audible alert - such as a loud speaker will normally be used to provide the alert signal. Optionally the device will also be provided with a wireless or other communications link. The wireless link can be deployed to receive commands and transmit information to a remote station, either continuously on a predetermined period basis.

It is therefore possible to discriminate between the two main conditions determined by the device, flow and no flow. By monitoring the temperatures during a period when no flow is expected, any detected flow indicates that a possible leak is present in the system. The leak may be due to pipe or pipe joint failure, dripping taps, failed cisterns in toilets or any other condition which would result in continuous water flow in a pressurised plumbing system.

In one possible embodiment of the device, the device operates for 24 hours a day on a domestic water main. Typically at night there will be no water flowing in the pipes as no taps will be used and appliances such as washing machines will have finished their cycles.

The device is programmed to monitor and recognise a pattern in temperature change in the detectors. After a period when there are no sudden changes in pipe temperature (due to taps switching on) have stopped or appliances being used the ECU can be programmed to determine if the pipe temperature has not changed rapidly or significantly and compare it to the ambient temperature. It also recognises that the ambient air temperature is stable (within limits) so the device is not being adversely affected by other heat sources (for example being near a radiator or hot water pipe).

The ECU can be programmed to monitor the changes measured by the temperature detection means of the temperature of the water pipe and the ambient air. The water pipe temperature will generally be an exponential approach towards air temperature with a slope within certain limits. In a “no leak” condition, the asymptotic difference between the pipe and air temperatures will be below a calibrated value, between 0 and 0.5°C, typically between 0 and 0.3°C, but preferably between 0 and 0.1°C. If the asymptotic temperature difference is higher than these values for greater than a predetermined period of time, say an hour or more, then there is usually flow in the pipe indicating a leak.

In another possible embodiment, the ECU in the detector may determine whether the device is subject to a constant heating or cooling from an external heat source or sink. In this case it may alert the user that it is unable to determine if a flow condition is present.

In another embodiment, the device may detect that its sensors are giving invalid values due to an error or component failure and alert a user to the fault.

On detecting a leak the device may alert a user by one of many different means typical of such domestic alarms. For example it may use an audible alert. Alternatively, or additionally, it may also include a light or a display. To avoid waking a user at night, it may wait until it next detects flow (because a user has woken up) before issuing an alert.

The device may also issue alerts and other information via a remote telemetry system. This could be one of any such technologies known in the art. For example using a cellular phone modem, an internet connection, a home automation protocol (e.g. Z Wave), a landline phone modem, an acoustic modem or any other such transmission mechanism.

In another possible embodiment, the device detects the sudden changes in pipe temperature relative to air temperature which are characteristic of taps turning on or toilet flushes. It can be calibrated to estimate frequency and quantity of water usage. Dips (or peaks) in the pipe temperature show water usage. Counting short dips shows the frequency of water usage for low use items (hand washing, toilet flushing). The height of the dips give an estimate of the incoming mains water temperature. When the pipe temp is approximately the same as the input water temperature for an extended period of time, we can assume we have constant flow over that time period. This indicates either shower, bath filling or other extended use such as irrigating a lawn.

According to another feature of an embodiment, the ECU restarts the determination of the predetermined period of time if the difference between the ambient and pipe temperatures suddenly changes to be greater than the predetermined value. Thus if a sudden sharp difference of temperature is detected between the two sensors, the ECU can be programmed to determine that a flow of water has occurred and so restart its monitoring process.

According to another feature of an embodiment, the ECU determines if the temperature difference between the ambient and pipe sensors is tending to or approximating to an exponential approach to 0 and if so indicating there is no flow in the pipe system. If the two temperatures do not converge exponentially after a period of say an hour, the device can be programmed to generate an alarm signal.

In yet another possible embodiment, the device can be programmed to note the absence of water usage over a period of time. This information may then be used to check on the presence and activity of a person in the home. For example if an elderly or vulnerable person has not used water for a predetermined period, such as a day, it may indicate that they have a problem and a carer can be alerted.

In yet another possible embodiment, the device can be programmed to rank a water leak rate according to size of the temperature difference (assuming it has reached a constant or substantially constant difference for a period of time,) thus providing an indication of the severity of the leak. If the pipe temperature stays at close to the estimated incoming water temperature (using the dip height method above), then the leak is a reasonably high flow rate. If it is within 0.5°C or so of the air temperature, it is typically a dripping leak. Temperatures in the middle indicate a medium flow leak.

In yet another embodiment, the device may have a ‘holiday’ mode that can be set by a user who knows that no water flow should be expected for e.g. 72 hours or 14 days or however long a user is absent. If any water flow is detected during that period, an alert would then be triggered.

In a further embodiment the device may connect to a service which could alert the user (e.g. by text, email or smartphone app) of the presence of leaks automatically, or it could send the alert directly to a maintenance company. The service may also alert a service provider or a plumber who could then check the leak. The device could also contact for example a neighbour who may check on a property.

Figure 7 shows a possible additional feature in which the device is connected to and controls a powered shut-off valve. The device may then, depending upon the estimated severity of the leak, shut off the water supply in response to a leak. It could also shut-off the water when the device is in holiday mode, or only if any flow is detected when it is holiday mode. Fig 7 shows a device 10 monitored by the ECU 40 and fitted to the pipe 12 . If a leak is detected or there is flow for more than a predetermined period of time, then the controller can shut off the supply in pipe 12 using the valve 50.

In this embodiment, the user may also be able to shut off the water for example using a remote switch, or another interface such as a smart phone app.

In an alternative and further embodiment the ECU may be configured to monitor flow and signal an alarm if there is no flow for a given period of time. For example, the alarm may sound if there is no flow for more than 36 hours. In another embodiment the alarm signal may be sent if there is no flow detected for periods between 18 and 24 hours. This embodiment could be particularly useful as an aid to monitor people living in sheltered or supported accommodation where lack of water flow for an extended period could be an indication the person or persons are in need of help. Clearly, a balance needs to be struck between having a period that is not too long so that the person is not left for too long if help is needed and a period which is too short that it leads to false alarms.

An alarm signal can be generated if the predetermined conditions for flow (or lack of flow) are met. The alarm could be an audible alarm generated by the audible signal generating means on the device itself. Alternatively or additionally, a visible alarm signal could be generated.

It can be expected that normally devices according to embodiments of this invention will be located close to the place where the water inlet enters a building and so are frequently located in cupboards, cellars, possibly even at a remote stop cock, and so not conveniently visible. It is therefore convenient for the device to be fitted with a wireless transmitter means to transmit the alarm to a station where it is more conveniently received and monitored. Alternatively the device may be located outside in a meter pit, in which case a wireless transmitter may also be more convenient as an audible alert may not be heard.

Advantageously, the wireless transmitter can also be programmed to transmit additional information from time to time. Such information could conveniently include information about flow rates and periods of zero flow, information about the state and condition of the batteries to provide low battery warnings, other error messages to indicate sensor errors or the like.

Preferably the power supply is a battery or set of batteries selected to provide long maintenance free life in an environment in which the device operates. However, it could advantageously be connected to a mains power supply.

In yet another alternative arrangement, the power supply comprises a mains power supply connected to a battery pack up system to provide power in the event of mains failure.

The following describes features, any one or more of which may additionally or alternatively be present in any embodiment such as an embodiment described above or below.

Indoor Usage

Generally, the ECU, or at least the pipe temperature sensor, may be connected to an indoor pipe, e.g., a water pipe preferably close to where the pipe enters a building (for example through the floor). In this regard, it is noted that the pipe may be close to additional heat sources, e.g., other plumbing for example carrying hot flowing water such as for a central heating system.

Thermal Mass Lag effect

In some circumstances, a high heat capacity local object, e.g. a concrete block and/or other plumbing as above, may result in a different temperature versus time progression of the pipe temperature relative to the ambient pressure during a no flow period. This may lead to the pipe temperature crossing the ambient, e.g., air, temperature as mentioned above, and may restrict the ability to confirm presence or absence of a leak.

In the event of a residual temperature difference after a no flow period of three to four hours for example, it is preferable that no alarm (e.g., visual and/or audible notification or alert) indicating a leak is generated if the residual temperature difference is due to thermal mass lag. Thus, if a crossing point is detected then it may be preferable to disable such an alarm. For example, the alarm may be disabled regardless of whether it is detected that the air and pipe temperatures are converging (see leak detection methods below based on time gradient of pipe temperature). An embodiment may be configured to detect a crossing point and thus to conclude that the mass lag effect is occurring, and to enable or disable a leak alarm accordingly, for example for a predetermined period of time until monitoring for a leak may restart.

Variable Leak Detection Threshold

Where in an embodiment a leak condition is determined using a threshold, for example at least based on a temperature difference between the pipe and ambient relative to a predetermined threshold for a predetermined period as described above and/or based on a temperature gradient and predetermined threshold as described below (see equations 4a, 4b, 6a, 6b below), it may be advantageous to vary such a threshold(s) for example according to the time of year. Regardless of whether or not the flow detection system, e.g., ECU thereof, is able to track the time of year for example by means of an internal electronic calendar, the threshold may be varied based on a starting difference between the pipe and ambient temperatures.

The starting temperature difference may be the difference in readings of the two temperature sensors at the start of the predetermined period used to monitor for a leak. The start of the predetermined period may be identified when it is detected that the difference between the temperatures suddenly changes at a rate above a predetermined value and/or may be the last detected time point where the temperature versus time gradient of the pipe temperature reverses sign such that the pipe temperature tends towards the ambient temperature.

If the starting temperature difference is smaller, then a lower threshold may be applicable. For example, if the starting temperature is 4°C then a pre-determined threshold may have a value of 0.3°C, or if the starting temperature difference is 0.5°C then the threshold may be 0.1 °C.

Calibration

Where in an embodiment a leak condition is determined using a threshold, for example at least based on a temperature difference between the pipe and ambient relative to a predetermined threshold for a predetermined period as described above and/or based on a temperature gradient and predetermined threshold as described below (see equations 4a, 4b, 6a, 6b below), the embodiment may further be configured to perform a offset procedure similar to a calibration. This may be advantageous in view of the potential scenario that the pipe temperature does not approach the ambient temperature at least within the predetermined period because of the thermal lag effect of a local object having significant thermal mass capacity.

Where an embodiment knows that the pipe should have no flow in the absence of any leak, for example based on a communication from a remote entity and/or because it has determined that a stop cock coupled to the pipe is off , the embodiment may determine if there is any residual temperature difference between the pipe and ambient and, if there is, adjust, e.g., increase or decrease, the predetermined threshold accordingly. Thus, a form of calibration procedure or adjustment may be performed. Alternatively, in such a case where an embodiment determines if there is any residual temperature difference between the pipe and ambient, the embodiment may alert the user, e.g., by a visual and/or audible signal or notification, that the embodiment is unable to detect a leak and/or that the attachment to the pipe (e.g., at least the pipe temperature sensor) needs to be moved to a different position on the pipe, e.g., away from the ground.

Similarly, a calibration procedure may be carried out for example in a factory before delivery to a user, to reduce any effects due to mismatching of the temperature sensors. An offset to be applied to any determined temperature difference on which a leak status may be detected may be determined by placing the unit in a thermally insulated environment, e.g., insulated box, and waiting for a relatively long duration e.g. six hours, before measuring any temperature difference between the sensor readings and adjusting the offset accordingly. This may be performed by a test mode of the unit when the unit is first powered up.

Initiating Leak Detection Operation

An embodiment may be configured to detect when the unit is mounted on a pipe such that operation for monitoring for any leak can be started. The unit may be configured to wait until a sudden change in pipe temperature relative to the ambient temperature is detected, preferably repeatedly such as at least three times in 24 hours. The unit may then effectively know that it is in use, i.e. no longer separate from a pipe to be monitored.

Such a feature may give confidence for example to an insurer that any readings or notifications arising from the unit relating to leak detection have resulted from events occurring while the unit was fitted to a pipe.

The start of leak detection operation may be indicated by communicating this to a remotely located control entity and/or may be recorded internally within the unit, preferably recording the date at which the unit was mounted onto the pipe, or incrementing an internal timer so the total time that the device has been fitted to a pipe is known.

Alarm re-set

An embodiment may have a re-set button to allow a user to deactivate an alarm (e.g., visual and/or audible notification or alert) that has been activated in the event of the system/device indicating a leak. Preferably, the system, e.g., ECU, is configured to store internally and/or communicate externally that the alarm has been re-set (e.g., including a time of the re-set), and may further store and/or communicate when the alarm has been re-set (e.g., including a time of the re-set). This may allow determination for example by an insurer of when the alarm has been re-set but no call out for attending to a potential leak has been initiated. The re-setting of the alarm may be communicated, e.g., wirelessly, to a remote entity.

Alarm filtering A preferred embodiment does not provide an alarm, e.g. notification to the user and/or an audible and/or visual indication by the unit, every time a potential leak is detected. Such an alarm may be provided only when a potential leak detection occurs repeatedly on each of a pre-determined number of periods when no flow would be expected in the absence of a leak, e.g. three night time such periods.

Similarly, if a temperature pattern is detected having transition(s) corresponding to at least one leak-no leak transition during each of a pre-determined number of such periods then no alarm may be generated. Such a pattern may merely indicate that a user has a tendency to sometimes leave a tap dripping and not fully off and later to turn it off fully, for example. Preferably, no alarm is generated until at least seven night-time periods (or other periods of no flow expectation during a respective 24 hour periods) have occurred.

Burst pipe indication

An embodiment may be configured to detect when the pipe temperature stays substantially constant at a temperature that differs significantly by a pre-determined amount at least from the ambient temperature. In this case, the pipe temperature may have previously varied according to fluid (e.g. water) usage but then remain at the substantially constant temperature without beginning any rise towards the ambient temperature. The substantially constant temperature may be detected as corresponding to a water temperature estimated based on the preceding variations according to usage.

If the pipe temperature remains at the constant temperature for a pre-determined period, preferably longer than the longest period of usage expected for full flow such as when a user is washing a car (e.g. longer than 1 hour), this may indicate a burst pipe condition. Preferably, the detection of the substantially constant temperature for the pre-determined period results in the unit immediately issuing an alarm (e.g., visual and/or audible notification or alert). It is preferable in this case that the generation of a leak alarm is not disabled even for verification over more than one 24 hour period. In other words, preferably no verification is to be performed before issuing an alarm in the case of a potential burst pipe detection.

Holiday mode

An embodiment may be configured to detect when a pre-determined number of, e.g., 24 hour, periods have passed with no flow, for example encompassing seven nights. Such no flow may be detected by determining that the pipe temperature tracks the ambient temperature throughout the predetermined number of such periods. If such an extended no flow period has occurred and the embodiment subsequently detects a sudden change in pipe temperature, for example indicated by a rate of change of pipe temperature greater than a pre-determined amount or a change in magnitude of pipe temperature greater than a pre-determined amount preferably over a predetermined minimum period such as 60 minutes, an alarm (e.g., visual and/or audible notification or alert) may be generated due to the risk of the change indicating a burst pipe. Preferably no delay e.g. due to verification, is allowed before such an alarm is issued.

Torbeck valve A property may have one or more valves that allow for automatic re-filling of tanks. Such a valve is for example a Torbeck valve for re-filling the tank or cistern of a toilet. The valve may have hysteresis built in such that it allows flow intermittently, e.g. periodically, for example every few hours. An embodiment may be configured to detect a repetitive, e.g., periodic, flow pattern corresponding to such a valve. Such a pattern may be detected from corresponding changes of pipe temperature. The embodiment may be programmed to filter out such changes from the pipe temperature profile to be monitored for leak detection relative to the ambient temperature. In this way, false leak alarms may be reduced or prevented.

Remote Communication

An embodiment may output a minimum of data points from temperature profiles of the air and pipe and send these to a remote entity for determination of a leak/no leak status. Such data points may comprise the ambient temperature, pipe temperature, starting temperature and/or temperature-time gradient(s) of the ambient and/or pipe temperature profiles at the time point when the flow was last detected, e.g. water was last used. Such data points may be transmitted, e.g. wirelessly, to a remote control unit that decides if a leak has occurred based on those data points. This may be advantageous where the remote system decides what should be an appropriate predetermined threshold of temperature difference, for example depending on weather patterns/forecasts. The remote entity may adjust such a threshold on the fly for example in case of a heatwave where the ambient temperature is of the order of e.g. 30°C and the pipe temperature is therefore not able to catch up during the predetermined period.

By varying such a threshold remotely, the remote system may be able to ensure that all devices are disabled from providing any leak alarm and/or ensure that any such alarm is ignored. Such remote control of the alarm process may be advantageous where sufficient data on preceding weather conditions is not able to be programmed into a leak detection unit mounted on a pipe. By providing the leak detection remotely, the system has some flexibility.

Taking into account that a leak detection may not necessarily be in radio communications at all times with a remote entity, a leak detection unit may have two modes of operation. In a first mode where radio communications are possible, the remote system may decide based on data points from the leak detection unit when an alarm is to be generated. In another mode, the unit detects that it is out of radio communication and is then configured to make decisions on alarms internally. An embodiment of the leak detection unit may have an indicator for indicating to the user whether or not the unit is able to perform radio communications with the remote entity. Where the unit is not in radio communications, it may be configured to provide notification to the user, e.g. to the user’s mobile phone, to inform that the unit is operating in the independent, isolated mode.

In a preferred embodiment, data may be sent to a remote unit wirelessly, e.g., using sigfox (RTM) (this may be advantageous where there are bandwidth constraints). A unit that is local to, eg., attached to, the pipe may look for smooth regions where we can check for leaks (for example, it may look to (re-)start a predetermined period each time a water usage/flow is detected), then a predetermined threshold for leak detection may be adjusted at the remote unit to allow for temperature variations, desired sensitivity of the detectors, and/or to classify the leak according to severity.

Data that may be sent using, e.g. sigfox (RTM), may comprise for example: message type; message count; indication that ambient and pipe temperatures have crossed; pipe temperature sample(s), ambient temperature sample(s); indicator of time interval between each pipe temperature sample; and/or battery voltage.

Where more bandwidth is available, the ambient/air and pipe temperatures may be sent to the remote unit at every sample point. These may be batched and sent as a group to save battery power (e.g. send the last 10 samples every 1000 seconds). The leak detection algorithm may then be run remotely (permitting updates to be applied without needing to reprogram the detectors in the field).

Start of predetermined period

The predetermined period during which an embodiment monitors for a leak, e.g., by monitoring to detect a below threshold temperature difference and/or convergence of pipe and ambient temperature profiles, may have a predetermined duration, e.g. 2.7 hours, beginning at a starting time. The starting time may be determined by detecting a peak in d2T/dt2, taking into account the sign of this second differential (the term ‘differential’ being used interchangeably with ‘derivative’ throughout this specification, for example the second order derivative d2T/dt2 being referable to as a second derivative/differential of temperature with respect to time). Such a peak may be interpreted as indicating a water usage/flow and may thus be used to trigger the start of a new predetermined period, e.g., to re-start an existing monitoring period. When the second order differential is negative and the pipe temperature is greater than the ambient/air temperature, this may indicate the start of the predetermined period. When the second order differential is positive and the pipe temperature is less than the air temperature, this may similarly start a predetermined period.

Additional or Alternative Leak Detection

One method of leak detection involves using a determination of temperature difference between pipe and ambient air sensors and determining if the temperature difference is below a pre-determined threshold for a pre-determined period, as described elsewhere in this specification. However, depending for example on the time of year and/or a local climate, the temperature of the pipe may not be substantially constant throughout a period of no flow. Consequently, additionally or alternatively to the above method, an embodiment may determine a leak/no leak state based on whether or not the pipe temperature and ambient temperature tend to converge (as opposed to, e.g., ‘tracking’, i.e., generally staying parallel with a constant or zero offset).

Generally, in a no flow (e.g. no leak) condition, the pipe and ambient air temperatures may tend to gradually converge. In a flow or leak condition, the pipe temperature may tend to a constant temperature without returning to or at least converging towards the ambient temperature; this may even involve the pipe temperature crossing the ambient temperature.

In one scenario, in the no flow condition, the pipe temperature may gradually drop or rise depending on the environment so that the temperature difference between the ambient and pipe temperature sensors generally reduces. Bearing this in mind, it may be advantageous for detecting a leak to monitor the progression of the pipe and/or ambient temperature relative to each other, for example by monitoring progression of a gradient of temperature vs time of at least the pipe temperature. Such monitoring may allow early detection of a leak without awaiting detection of a sufficiently low and/or constant temperature difference between the sensors, e.g., without waiting to see if the pipe and ambient temperatures track and/or become closer than a threshold difference apart.

Thus, a preferred embodiment, additionally or alternatively to the monitoring of the temperature difference relative to a threshold, may monitor whether or not the pipe temperature tends to converge towards the ambient temperature, when there has been no other water usage for a length of time (for example 5 minutes). Detecting such a lack of water usage may be done by monitoring the second differential of the pipe temperature relative to time (i.e., d2Tp/dt2), and waiting for it to be below a certain threshold, indicating no sudden changes in temperature and hence no changes in flow due to taps switching off and on or other intermittent usage. To monitor for convergence, an embodiment may monitor the pipe and air temperatures based for example on the equations below.

The rate of change of the measured local pipe temperature can be considered to be: dTp/dt = hl(Ta-Tp) + h2(Tw-Tp) (1) wherein Tp is the pipe temperature, Ta is the ambient temperature and Tw is the temperature of the water entering the pipe from the mains supply, hi may be considered a (generally constant) transfer coefficient between the pipe and the ambient (e.g. air), and h2 may be considered to be a flow-dependent (thus, may be non-constant) transfer coefficient between the pipe and mains water supply. h2 may be strongly dependent upon the rate of flow of the water in the pipe, q. If q is zero (no leak), then h2 will be very close to zero. If q is non zero, then h2 may start to affect, and/or have a greater effect on, dTp/dt.

If there is flow through the pipe, then the coefficient of heat transfer between the water and the pipe, h2 may be larger relative to hi. Over a period of time (typically 5 mins to 3 hours), Tp will generally tend towards Tw. As Tp approaches Tw, the rate of change of Tp, dTp/dt may be small, even if there is a still a relatively large difference between the air temperature and the pipe temperature (Ta-Tp). This may be indicative of flow in the pipe and presence of a leak.

One embodiment of implementing this in practice is as follows:

Rearranging (1) for hi gives hi = [(dT p/dt)-h2(Tw-T p)]/(T p - Ta) (2)

When h2 is large, (1) shows that generally Tp will tend towards Tw over time as Tp will asymptotically approach the water temperature. Tp may approach a steady state as the h2(Tw-Tp) term becomes smaller, and we can then approximate (2) based on the observables Tp and Ta as hi' = (dTp/dt)/(Tp - Ta) (3)

If hi' is small, then the gradient in the pipe temperature over time is small relative to the difference between the pipe and the ambient/air temperatures. The pipe temperature may then be not tending towards the ambient/air temperature in a way which would be expected under a no leak condition, i.e., there may be an additional heat source or sink being applied to the pipe, potentially indicating the presence of flow in the pipe and thus a leak.

Thus, if it is detected that (dTp/dt)/(Tp - Ta) < THRESH (4a) over a period of several minutes to a few hours, this may be interpreted as indicating a leak, where THRESH is a value that is preferably close to zero but sufficient to allow for variations due to noise and/or water temperature changes.

And if (dTp/dt)/(Tp - Ta) >= THRESH (4b) then this may be interpreted as indicating that there is not a leak. Example values of THRESH may be, e.g., 0.001, 0.005, 0.01, 0.1 or 1.

In an embodiment, rather than calculating the first differential dTp/dt by calculating the difference between Tpn and Tpn-i where Tpn and Tpn-i are the values of Tp in successive time periods (which calculation may amplify any noise in the readings), exponential function(s) may be fitted (e.g., finding a best fit for example by means of a least squares fitting method) to the Tp and/or Ta samples over a region in which there has been no previously calculated water usage (this may have been indicated by other means). The exponential function(s) may then be used to calculate a value indicative of dTp/dt by analytical differentiation of the fitted exponential. Each fitted exponential function for the pipe and air temperature may be of the form a + bt + ce* where a, b, c and/or d are generally taken to be constants and t is an indicator of time. In this case analytical differentiation of the function may calculate the value indicative of dTp/dt by calculating b + cdect.

Advantageously, the use of an equation above, e.g., (3), (4a) and/or (4b), may allow an early and/or fast response to a leak condition.

In an embodiment, leak detection based on a ratio such as in equation (4a) and/or (4b) may be combined with an above described detection method based on detecting when a temperature difference is below/ not below a predetermined threshold for a predetermined period. For example, they may run in parallel to provide redundancy and/or to improve robustness. If either algorithm predicted a leak a number (1 or more) of times then a leak could be reported for example by outputting an alarm.

To further understand an embodiment implementing a method of leak detection, consider first a situation where generally there is no influence on pipe temperature Tp other than the ambient temperature Ta: for example, there is no leak. In this case:

If the pipe is cooling, then dTp/dt is negative; if the pipe is warming, dTp/dt is positive. Thus,:

where Ah is a constant relating to a contact area between the pipe and fluid (e.g., water) and Mcp is a constant relating to a mass of the pipe and water mass, i.e., Ah/Mcp may be regarded as a heat transfer coefficient b.

If we consider the general mathematical relationship:

where y is a function of time t, then y = Tp - Ta would mean that:

where

so that:

i.e.,

where T0 is the initial temperature of Tp at t = 0.

The above ‘no other influence’ scenario can be used to understand the following using a term F = bF’ to reflect the presence of a leak.

Assume that:

where bF’ is negative is the leak causes the pipe to cool, and positive is the leak causes the pipe to warm. then:

(5)

Using a temperature term x including temperature effect F’: then:

which can be rewritten to give:

F’ may be considered to represent a leak, expressed here as an effective reduction in ambient temperature. Thus, determining whether F is large or small may indicate the presence or absence of a leak.

From (5):

Thus:

If:

(6a) then this may indicate the presence of a leak, where THRESH is a predetermined threshold.

Conversely, if:

(6b) then this may indicate the absence of a leak.

In this way, the observables Tpand Ta can be used to determine presence and/or absence of a leak. Example values of THRESH may be, e.g., 0.001, 0.005, 0.01, 0.1 or 1.

In view of the above, to implement leak detection, a leak detector for detecting a leak in a water supply system comprising a pipe may have a first temperature sensor detecting ambient temperature, a second temperature sensor configured to be mounted adjacent or in thermal contact with a pipe of the pipe system, and a processing means configured to determine a temperature difference between the first and second temperature sensors, wherein the processing means is configured to indicate the presence of a leak if a monitored variable is above a predetermined threshold for a predetermined period, wherein the monitored variable is the sum of an indicator of time gradient of the sensed pipe temperature and a multiple of the temperature difference, where the multiple represents a constant heat transfer coefficient. The leak detection method based on such a sum may be combined with either or both of the two methods based on the temperature difference relative to a predetermined threshold and on hT. Furthermore, optional features provided for either of those two methods, for example with regarding to identifying the starting point for the predetermined period, etc., may be applied for this sum-based method similarly.

In an embodiment, leak detection in line with equation (6a) and/or (6b) may be combined with an above described detection method based on detecting when a temperature difference is below/ not below a predetermined threshold for a predetermined period and/or with a detection method based on a ratio as in equation (4a) and/or (4b). For example, any two or more of these methods may run in parallel to provide redundancy and/or to improve robustness. If either algorithm predicted a leak a number (1 or more) of times then a leak could be reported for example by outputting an alarm.

Generally speaking, the embodiments described herein are implemented indoors, i.e., are attached to a pipe within a property in order to detect leaks. This may be advantageous depending on geographic location, since an outdoor location may require some thermal insulation to prevent the pipe freezing. Such insulation may interfere with monitoring the ambient temperature, depending on the arrangement of sensors.

Regarding further examples of temperature-time traces, the above descriptions of Figs. 5a, 5b, 6a and 6b further serve to describe Figs. 8a, 8b, 9a and 9b, respectively, the latter drawings however covering different periods of time.

Fig. 10 shows further example temperature-time traces of pipe temperature Tp and ambient temperature Ta, including monitoring periods for ‘no flow’ and ‘flow’ instances.

Fig. 11 shows further example temperature-time traces of pipe temperature Tp and ambient temperature Ta. As shown, a maximum ambient / air temperature may be used for a starting temperature difference to trigger a monitoring period. Alternatively, the ambient / air temperature used for the starting difference may be the temperature of the ambient / air at the instant that the pipe temperature curvature is at a maximum.

Fig. 12 shows an example fluid flow detector system 10a, for monitoring a pipe 12a of a water supply system 100. The water supply system may further comprise a stopcock 150, a valve 140 such as a Torbeck valve, and/or a powered shut-off valve 130 which may be controlled for example by the processing means (preferably comprising one or more processors), e.g., ECU 40a. The fluid flow detector system may be a self-contained device for attaching to the pipe 12a, or may comprise a system of couple devices, e.g., the pipe temperature sensor 16a and/or ambient temperature sensor may be provided externally to a device comprising the processing means 40a, e.g., may be coupled by a wire(s) or wirelessly to such a device. The power supply 42a may be coupled to a mains network 120 and/or may comprise a battery(s). The alarm generator 46a is shown in the fluid flow detector system, e.g., in a device housing at least the processing means, however such an alarm generator may additionally or alternatively be provided at a remote entity 110. The alarm generator 46a may send an alarm preferably, wirelessly, to a user 160 and/or to or via a relaying means 48a and/or a remote entity. The fluid flow detector system, e.g., a device comprising at least the processing means, may comprise a relaying means, e.g., a communication interface comprising a transmitter and/or receiver, preferably wireless, for communication with a remote entity 110 (e.g., remote alarm signal receiving station).

Fig. 13 shows an example computing device or system on which at least the processing means, e.g., electronic control unit, of an embodiment of the invention may be implemented. Similarly, remote entity, e.g., remote alarm signal receiving station, may by implemented by such a computing device / system. Each element of Fig. 13 is optional. The computing device/system of Fig. 13 comprises a bus, at least one processor, at least one communication port (e.g., RS232, Ethernet, USB, etc.), and/or memory, all generally coupled by a bus (e.g., PCI, SCSI). The memory may comprise non-volatile memory such as read only memory (ROM) or a hard disk and/or volatile memory such as random access memory (RAM, e.g., SRAM or DRAM), cache (generally RAM) and/or removable memory (e.g., EEPROM or flash memory). The processor may be any known processor, e.g., an Intel (registered trademark) or ARM (registered trademark) processor. A user interface, e.g., display screen and/or keyboard may be provided. The processor 24a may be an ARM (RTM) device or a similar processor produced by another manufacturer such as Intel (RTM).

Further Alternative or Additional features of Embodiments

The following describes features of embodiments, any one or more of which features may be provided in any combination, and in any embodiment disclosed above, for example in an embodiment using the dip (and/or peak) height method.

If a leak is due to a pipe burst or other catastrophic failure, it may be beneficial to detect the leak quickly, e.g., earlier than a 4 hour wait which may otherwise be used to determine a low flow leak.

Continuous water usage may be evident by the pipe temperature tending to be close to the incoming mains water temperature and staying at a close to constant value for a period of time, for example 20 minutes. Such usage may be detected by an algorithm, which is described below with reference to the features 1-9 shown in Figs. 14 and 15, wherein the dash-dot-dash lines indicate estimated air temperatures, and the solid and dotted lines indicate measured pipe temperature and estimated incoming water temperature, respectively. The pipe temperatures of Fig. 14 (labelled 4) and shown similarly in Fig. 15 may be detected by a pipe temperature sensor (thermistor). The ambient (air) temperatures of Fig. 14 (labelled 1) may be measured by a sensor. However, an embodiment may omit an ambient air temperature sensor, and therefore a measured air temperature trace is omitted from Fig. 15.

In the algorithm, and with reference to Fig. 14, the incoming water temperature (3) may be estimated by analysing pipe temperature curvature over time preferably based on the second differential of pipe temperature (d2T/dt2). Specifically, the estimation may look for peaks (2) in the second differential of the pipe temperature (4). Using the second differential may identify points of sharp curvature (e.g., greater than a threshold indicator value) for example where a tap is turned off and on. Taking an average of, or otherwise smoothing, the temperatures at each of these points may give a rolling forward looking estimate of the water temperature entering the building (generally from underground). This temperature of water entering the building generally varies reasonably slowly as the season changes, so may be updated slowly to smooth out points where a very small amount of water usage has chilled the pipe only slightly.

When there is a region (5) where the pipe temperature remains roughly (e.g., exactly) constant for an extended period of time, say 20 minutes, then the pipe temperature may be compared to the estimated water temperature and the air (ambient) temperature (1). If the pipe temperature and estimated water temperature are close (e.g., having less than a threshold temperature difference), but the air temperature is noticeably different to both of them (e.g., having greater than a threshold temperature difference), then a continuous flow condition may be assumed. A flow (or leak) may then by indicated (e.g., internally, audibly and/or visibly on the detector housing, and/or by notification to a user and/or a central control unit). One metric for doing this is a proxy flow estimate based on the ratio of the temperature differences (6) and (7), for example Q=(Tair-T pipe)/(Tair-Twater)

If flow parameter Q is close to 1 or above a defined threshold, then continuous flow may be assumed. Flow (e.g., leak) may then be indicated, e.g., internally and/or preferably by notification directly to the user and/or external control unit. If Q is close to 0, then there is no or low flow, which may similarly be indicated. By repeatedly updating the value of Q as new temperature readings are taken, then the duration of the continuous flow may be measured and monitored, preferably using a timer T1. If any distinct changes in the pipe temperature are observed, for example by measuring the gradient of the pipe temperature and comparing it to a threshold, then the duration estimate may be restarted, as it is likely that the water flow has stopped and restarted, indicating that for example one shower has stopped and another started.

By choosing the duration over which continuous flow is monitored for, unusual or extended water usage may then be alerted. For example if continuous water usage is typically less than 20 minutes, then an alert may be generated when continuous water usage is detected for longer than a threshold time duration of 20 minutes. This may be achieved using a timer T1. This may alert someone to a burst pipe, or possibly a bath that has been left running. More generally, an indication of flow or a leak may be provided internally, audibly and/or visibly on the detector housing, and/or by notification to a user and/or external control unit.

The duration threshold may be varied preferably in response to observed water usage, for example varied automatically by the processor and/or in accordance with direct and/or remote input from a user and/or external control unit. For example if a particular installation often observes continuous water usage for longer periods of time (because longer showers are taken for example) then the duration of full flow before an alert is sent may be adjusted to minimise nuisance alarms during showers. This may involve observing repeated periods of water flow that are shorter than a threshold time duration but longer than a shorter threshold time interval.

An embodiment may use a single sensor, or at least omit the air (ambient) temperature sensor. A flow/leak detector may then have a lower component count and may be manufactured at lower cost. In this regard, Fig, 16 shows an embodiment of a water flow/leak detector 200, which comprises components similarly to the system 10a of Fig. 12 (e.g., at least a pipe temperature sensor 16a and processor 40a), however optionally comprising a timer T1 and optionally omitting an ambient temperature sensor 20a (see Fig. 12). Where an air temperature sensor is not used, high flow leaks may still be determined using a similar method as above. However because the air temperature is no longer directly observable, it may instead be estimated. We refer in this regard to Fig. 15., wherein the dash-dot-dash lines indicate estimated air temperatures. The air temperature may be estimated by looking for an temperature (referred to for example as an end or target temperature) to which the pipe temperature is tending, e.g., when it follows an approximately exponential-type (e.g., proportional to x+ye',(,) where t is time and f(t) is a function of time such as and at+β, wherein x, y, a and/or β may be a constant) curve upwards (8). For example, the first dash-dot line of Fig. 15, where the pipe temperature plateaus, corresponds to such an end temperature of about 18.5 deg C. Determining such an end value, and/or an average of such end values corresponding to respective plateaus, may allow determination of an estimated air (ambient) temperature. Additionally or alternatively, an air temperature (9) may be estimated based on a smoothed and/or average of peak pipe temperatures following a detected such tendency to an end temperature (even if no plateau is reached); this may be preferred where it is desired not to wait for occurrence of a plateau in order to determine an end temperature. Such a temperature estimate using peak temperature(s) is shown by the second dashed-dot line of Fig. 15 at about 17.5 deg C above such peaks in pipe temperature. (Note that air temperature may change more quickly than incoming water temperature, so this preferably updates more rapidly). Using either estimation method when the ambient temperature sensor is omitted, the ratio of Tpipe - Tair(estimated) (10) to Tpipe - Twater (11) may then be calculated again and continuous flow identified using the same metric as above.

The algorithm may also function if water temperature is higher than air temperature, for example if the pipe temperature follows an exponential-type curve downwards and/or troughs are used instead of the above-mentioned peaks.

In an embodiment, timing, duration and/or flow amount of water usage may be estimated (e.g., low, medium, high, or an exact amount of flow and/or duration) from received pipe temperatures e.g., from a pipe temperature graph. For example whenever the pipe temperature dips down rapidly and then increases again (this may be taken to be indicated by a high negative first differential dT/dt, e.g., exceeding a threshold differential value, and/or on the basis a second differential) then short duration water usage may be assumed and preferably notified to a user, e.g., by mobile phone. Also when the pipe temperature similarly dips and rises, and measured Q is also high for a period of time (this preferably detected by measuring a duration for which the determined flow parameter remains above a threshold flow parameter value), then longer duration water usage may be assumed or otherwise determined, and preferably similarly notified. This may then be used to provide feedback to a consumer on the functioning of their leak detector, and/or to help encourage water conservation, for example by comparing them to other water users and/or showing that they are above average water users. Feedback to the consumer may indicate that they are light or heavy water users, and/or may indicate appropriate water saving tips to the user based on the detected usage.

No doubt many other effective alternatives will occur to the skilled person. It will be understood that the invention is not limited to the described embodiments and encompasses modifications apparent to those skilled in the art lying within the spirit and scope of the claims appended hereto.

Claims

1. A water flow detector for detecting a flow in a building water supply system comprising a pipe, the flow detector configured to determine ambient temperature and having a pipe temperature sensor configured to be mounted adjacent or in thermal contact with a pipe of the pipe system, and a processor configured to determine a first temperature difference that is between the determined ambient temperature and a temperature of the pipe temperature sensor, wherein: the processor is configured to generate an indicator of pipe temperature curvature based on outputs of the pipe temperature sensor; the processor is configured to identify a said indicator that exceeds a threshold indicator value and to store a said pipe temperature sensor output received when the curvature exceeds said threshold indicator value; the processor is configured to estimate a temperature of water entering the building based on at least one said stored pipe temperature sensor output; the processor is configured to determine a second temperature difference that is between the estimated temperature and the determined ambient temperature; the processor is configured to determine a flow parameter that is a function of a ratio of the first temperature difference to the second temperature difference; and the processor is configured to determine presence of a flow based on the flow parameter.

2. A water flow detector of claim 1, wherein the flow parameter is determined to be equal to: (Tai r-Tpi pe)/(T ai r-T water), wherein Tair is the determined ambient temperature, Tpipe is the temperature of the pipe temperature sensor and Twater is the estimated temperature of water entering the building.

3. A water flow detector of claim 1 or 2, wherein the indicator of pipe temperature curvature indicates a second differential of pipe temperature change relative to time.

4. A water flow detector of any preceding claim, wherein the function is a monotonic function of the ratio.

5. A water flow detector of any preceding claim, wherein: the processor is configured to determine, based on a plurality of said pipe temperature sensor outputs, when the pipe temperature tends towards an end value, and to determine the end value, wherein the processor is configured to perform the determination of the ambient temperature based on at least one said determined end value.

6. A water flow detector of claim 5, wherein: the processor is configured to perform said determination of when the pipe temperature tends towards an end value by determining when the pipe temperature tends substantially exponentially towards an end value.

7. Water flow detector according to claim 5 or 6, wherein the processor is configured to estimate the ambient temperature based on a time-based smoothing of a plurality of said determined end values.

8. Water flow detector according to any one of claims 3 to 7, wherein the processor is configured to detect at least one of maxima and minima of said determined end values and to estimate the ambient temperature based on said maxima and/or minima end values.

9. A water flow detector of any preceding claim, comprising another temperature sensor, wherein the processor is configured to perform the determination of the ambient temperature based on at least one output of the another temperature sensor.

10. A water flow detector of any preceding claim, wherein the processor is configured to indicate a flow when the flow parameter exceeds a threshold flow parameter value, optionally wherein the threshold flow parameter is 0.1, 0.2, 0.9, 0.95 or 0.98.

11. A water flow detector of claim 10, wherein the flow indication indicates a high flow leak, optionally wherein the threshold flow parameter is 0.9, 0.95 or 0.98.

12. A water flow detector of any preceding claim, comprising a timer to determine when the flow parameter remains greater than a threshold flow parameter value for a time longer than a threshold time duration, and to indicated presence of a flow responsive to a said determination by the timer, optionally wherein the threshold flow parameter value is 0.1, 0.2, 0.9, 0.95 or 0.98.

13. A water flow detector of claim 12, wherein said threshold time duration is at least 20 minutes, more preferably at least one hour.

14. A water flow detector of claim 12 or 13, configured to receive input from at least one of a user and a control unit, and to vary the threshold time duration according to said input.

15. A water flow detector of any one of claims 12 to 14, wherein the processor is configured to determine a temperature versus time gradient based on outputs of the pipe temperature sensor, and to restart the timer when the determined gradient exceeds a gradient threshold.

16. A water flow detector of any one of claims 12 to 15, configured to increase the threshold time duration when the flow parameter remains greater than a said threshold flow parameter value for a time that is longer than a threshold time interval, wherein the threshold time interval is shorter than said threshold time duration.

17. A water flow detector of any preceding claim, wherein the processor is configured to estimate the temperature of water entering the building based on an average of a plurality of said stored temperature sensor outputs.

18. A water flow detector of any preceding claim, wherein the processor is configured to indicate a flow when the flow parameter is between a first threshold flow parameter value and a second threshold value, optionally wherein the first threshold flow parameter is 0.1, 0.05 or 0.02 and the second threshold value is 0.9, 0.95 or 0.98.

19. A water flow detector of claim 18, wherein the flow indication when the flow parameter is between the first threshold flow parameter value and the second threshold value indicates a medium flow.

20. A water flow detector of any preceding claim, wherein the processor is configured to indicate no flow when the flow parameter is below a threshold flow parameter value, optionally wherein the threshold flow parameter is 0.1, 0.05 or 0.02.

21. A water flow detector of any preceding claim, wherein the processor is configured to determine presence of a leak based on the flow parameter.

22. A method for detecting a flow in a building water supply system comprising a pipe, the method comprising: determining ambient temperature; using a temperature sensor to detect a temperature of the pipe, the temperature sensor mounted adjacent or in thermal contact with the pipe; estimating a temperature of water entering the pipe, based on output of the temperature sensor; and determining when the pipe temperature remains substantially constant for a period of time greater than a threshold time duration, and if it is determined that the pipe temperature has remained substantially constant for a said period of time, then indicating a flow if: a difference between the estimated temperature and a said pipe temperature detected during said period is less than a first threshold temperature difference; a difference between the ambient temperature and the pipe temperature is greater than a second threshold temperature difference; and a difference between the ambient temperature and the estimated temperature is greater than a third threshold temperature difference.

23. Method of claim 22, wherein the threshold time duration is at least 20 minutes, preferably at least one hour.

24. Method of claim 22 or 23, wherein at least one of the first to third threshold temperature differences is at least 0.2 deg C, preferably at least 0.5 deg C, more preferably at least 1 deg C.

25. Method of any one of claims 22 to 24, wherein said determining ambient temperature comprises estimating ambient temperature by determining when the pipe temperature tends towards an end value, determining the end value, and determining an estimation of the ambient temperature based on at least one said determined end value.

26. Method of any one of claims 22 to 24, wherein said determining ambient temperature is performed based on an output of an ambient temperature sensor.

27. A method of providing water consumption feedback to a user of a building water supply system comprising a pipe, the method optionally using the water flow detector of any preceding claim and/or the method of any preceding claim, the method of providing feedback comprising: using a temperature sensor to detect a temperature of the pipe, the temperature sensor mounted adjacent or in thermal contact with the pipe; and at least one of: (a) determining when a magnitude of the pipe temperature has a peak and a time differential of the pipe temperature approaching the peak exceeds a threshold differential value, preferably wherein said threshold differential value is negative, and, responsive to a said detection, indicating a short duration water usage; and (b) determining a flow parameter that is substantially proportional to a ratio of a first temperature difference to a second temperature difference, wherein the first temperature difference is between a determined ambient temperature and a said detected temperature of the pipe, and the second temperature difference is between an estimated temperature of water entering the pipe and the determined ambient temperature, measuring a duration for which the determined flow parameter remains above a threshold flow parameter value, and determining how long water has been used for based on the measured duration.

28. The method of claim 27, wherein (b) comprises detecting when the flow parameter remains greater than a threshold flow parameter value for a time longer than a threshold time duration and responsive to a said detection, indicating a long duration water usage.

29. The method of claim 27 or 28, wherein the feedback to the user indicates that the user is a heavy water consumer or a light water consumer based on a a number or frequency of a said plurality of indications of short duration water usage and a number or frequency of a said plurality of indications of long duration water usage.

30. The method of any one of claims 27 to 29, wherein the feedback is based on comparing at least one said indication of water usage with indications of water usage of other water users, and determining in which quantile of distribution of water usage the user of the building water supply system is in.