Fluid-level sensing and monitoring for wastewater

Abstract

A method for determining fluid level in a manhole of a wastewater network by means of a radar distance sensor installed within the manhole at or near the top thereof. The method comprises performing a fluid level measurement event that includes executing a plurality of successive radar distance measurements generating peaks corresponding to surfaces and objects within the manhole. The fluid level is determined by identifying a peak with sufficient amplitude variation and / or phase angle deviation that corresponds to a distance above the manhole invert. A device, system and method for fluid level monitoring in manholes across a wastewater network are also disclosed.

Description

Fluid-Level Sensing and Monitoring for WastewaterTechnical Field

[0001] This invention relates to wastewater systems, in particular methods and apparatus for sensing and monitoring fluid levels in such systems.Background of Invention

[0002] A gravity sewer system is a network of pipes and structures that transport wastewater from homes, businesses, and other sources to a treatment facility or other disposal point using the force of gravity. This system is essential for public health and environmental protection.

[0003] The network of underground sewer pipes is punctuated by manholes that play a crucial role in this system, serving as access points along the sewer lines to facilitate maintenance, inspection, and cleaning. The network may contain different kinds of manholes, including, for example:• Maintenance or access manholes -- These are the most common type and provide access to the sewer system for inspection, cleaning, and maintenance. They are typically equipped with a manhole cover and a ladder or steps for entry.• Drop manholes - Positioned at locations where the sewer line changes elevation significantly, such as at the bottom of a steep incline or where a gravity sewer connects to a force main. Drop manholes help manage flow velocity and prevent sewer surcharge.• Intercepting manholes -- Placed at the junction of multiple sewer lines to intercept and redirect wastewater flow. They help control the direction of flow and manage combined sewer systems.• Ventilation manholes - Installed at intervals to allow the release of gases and odours that can build up in the sewer system. Ventilation manholes help maintain worker safety and prevent odours from escaping into the environment.

[0004] Manholes play an important role in monitoring and maintenance of the sewer system, including in:• Access for inspection and cleaning -- manholes provide access to the sewer system, allowing workers to inspect the condition of pipes, remove debris, and clean the system to maintain its efficiency.• Monitoring flow and levels - manholes may be equipped with sensors to monitor flow rates and water levels, helping operators assess the system's performance and detect issues like blockages or surcharge.• Preventing overflows - drop manholes are crucial for preventing sewer overflows by controlling flow velocity and ensuring the proper functioning of the system, especially in hilly or uneven terrain.• Emergency access -- in case of emergencies, such as blockages or pipeline damage, manholes provide quick access for repairs and maintenance to minimize disruptions and protect public health.

[0005] The main body of a typical gravity sewer manhole is a cylindrical structure made of durable materials like precast concrete, brick, or reinforced plastic. This shaft is typically vertical and extends below the ground surface to the sewer pipe's invert (bottom). The bottom of the manhole is referred to as the "invert." It is designed to match the flow channel of the sewer pipe, ensuring a smooth transition for wastewater as it flows through the manhole. The upper part of the manhole is often wider and provides space for access, inspection, and maintenance. This section may have a taper or cone shape to support the manhole cover and frame. Manholes are equipped with a heavy-duty cover and frame at the surface level. The frame is set into the top of the manhole, securing the cover in place. Inside the manhole shaft, there may be steps or a ladder for workers to descend into the manhole safely.

[0006] While some standardisation of manholes may be possible, in practice each manhole in a sewer network can have a unique structure, to account for the particular depth and arrangement of sewer pipes at the manhole location for example. This can present achallenge when installing sensors for monitoring water levels, and interpreting the signals from such sensors, since each manhole installation is different. Embodiments of the present invention seek to overcome or ameliorate these challenges.

[0007] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.

[0008] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.Summary of Invention

[0009] According to one aspect of the invention, there is provided a method for determining fluid level in a wastewater network enclosure by means of a radar distance sensor installed within a manhole at or near the top thereof, the method comprising performing a fluid level measurement event that includes: executing a plurality of successive radar distance measurements from the radar distance sensor into the wastewater network enclosure; for each of the plurality of successive radar distance measurements, identifying peaks in data representing the strength of radar reflections from surfaces and objects within the wastewater network enclosure together with data representing a corresponding distance of the reflections from the radar sensor; determining a fluid level of a fluid corresponding to an identified peak based on either one or both of an amplitude of the identified peak, and phase angle deviation corresponding to the identified peak.

[0010] The method may include determining a moving surface of the fluid in the wastewater network enclosure based on the phase angle deviation corresponding to the identified peak.

[0011] In some embodiments, the amplitude of the identified peak alone may be sufficient to determine the fluid level, for example when a negligible phase angle deviation is present for each peak. In these cases, the fluid may be stagnant / not moving. As such, the fluid level may be determined based on the identified peak having a largest amplitude.

[0012] In some instances, no peaks may be identified, for example where no flow or no fluid is present in the wastewater network enclosure.

[0013] Optionally, determining the fluid level of the fluid may include determining a phase angle for each identified peak of each radar distance measurement, determining the phase angle deviation between the determined phase angles for each identified peak across all successive radar distance measurements in each measurement event, and identifying a distance corresponding to the identified peak having a highest phase angle deviation.

[0014] Typically, the distance corresponding to the identified peak having the highest phase angle deviation may be used to derive the fluid level.

[0015] The method may further include eliminating any peaks in the data registering at a distance from the radar distance sensor beyond a depth of the wastewater network enclosure. Typically, the furthest fixture in the wastewater network enclosure from the radar distance sensor is the invert. For a given wastewater network enclosure, the distance from the radar distance sensor to the invert may be determined such that during operation, any peaks registering at distances beyond the invert are eliminated or ignored.

[0016] The method may further include determining a surcharge event when the fluid level exceeds a predetermined maximum fluid threshold level. Any suitable maximum fluid threshold may be used. For example, the maximum fluid threshold level may be based on the distance between the radar distance sensor and a manhole table in the wastewater networkenclosure. Alternatively, any other suitable fixture or arbitrary distance may be used to determine the maximum fluid threshold level.

[0017] The method may further include determining a relative flow rate of the fluid in the wastewater network enclosure based on the phase angle deviation corresponding to the identified peak, wherein a greater phase angle deviation is indicative of a higher flow rate, and a smaller phase angle deviation is indicative of a lower flow rate.

[0018] The method may further include reducing a power supply to the radar distance sensor in response to identifying a peak within a predetermined distance from the radar distance sensor. Generally, reducing power supply to the radar distance sensor may reduce the gain applied to the radar signals generated and received by the radar distance sensor. In the event that an identified peak is within a predetermined distance from the radar distance sensor, e.g. relatively close to the radar distance sensor, reflected radar signals from reflective surfaces close to the radar distance sensor may be relatively strong, and too much gain may cause the radar signals to become easily saturated. As such, a low gain would be suitable for obtaining a readable radar signal when measuring small distances. In some examples, the predetermined distance may be roughly 400mm, 500mm, 600mm or 700mm from the radar distance sensor, or any other suitable distance from the radar distance sensor.

[0019] The method may further include reducing a scanning distance of the radar distance sensor in response to identifying a peak within the predetermined distance from the radar distance sensor. Optionally, the scanning distance may be reduced to focus detecting surfaces within a smaller distance from the radar distance sensor. The scanning distance may be reduced to 400mm, 500mm, 600mm or 700mm from the radar distance sensor, or any other suitable distance from the radar distance sensor.

[0020] The method may further include adjusting power supplied to the radar distance sensor based on upper and lower thresholds to adjust a gain applied to the radar distance measurements. Any suitable upper and lower thresholds may be used. Typically, arbitrary upper and lower thresholds may be used based on experimental testing data. Generally, theupper and lower thresholds may be used to ensure that measurements between a usable range (to avoid saturation and excessive noise) can be obtained.

[0021] The adjustment of power to adjust gain may be automatic and continuous for each fluid level measurement event. In particular, the adjustment of gain may incrementally increase or decrease until an identified peak having maximum amplitude is within both upper and lower thresholds.

[0022] Preferably at least two successive radar distance measurements are used in each fluid level measurement event. However, any suitable successive radar distance measurements may be used in each fluid level measurement event. In some embodiments, three, four or more successive radar distance measurements are used in each fluid level measurement event.

[0023] The method for determining fluid level in a manhole of a wastewater network may further include transmitting to a central processor manhole status data and / or operational parameters determined from the radar distance measurements. The method may further include transmitting to the central processor a fluid level in the manhole as determined from the radar distance measurements.

[0024] The method may include a commissioning procedure wherein the radar sensor is installed in the manhole at a known height above the manhole invert level. The commissioning procedure may include recording reference peaks representing radar distance measurements in respect of static surfaces and / or objects in the manhole. The method may further include comparing the peaks identified in a fluid level measurement event with the reference peaks to identify debris or other extraneous static material in the manhole.

[0025] The present invention also provides a method for monitoring fluid level in a manhole of a wastewater network by: installing a radar distance sensor within the manhole at or near the top thereof; and performing a fluid level measurement event to determine a fluid level in the manhole according to the method as disclosed herein.

[0026] The present invention also provides a method for monitoring fluid levels in manholes comprising part of a wastewater network by: installing respective radar distance sensors within a plurality of manholes of the wastewater network; performing a fluid levelmeasurement event to determine a fluid level in each of the respective manholes according to the method as disclosed herein; and reporting the determined fluid levels in the respective manholes to a central processor. Preferably, the operations of performing a fluid level measurement event and reporting the determined fluid levels are performed periodically, e.g. every few minutes to few hours.

[0027] The present invention also provides a device for monitoring fluid level in a manhole of a wastewater network, comprising a radar distance sensor operable by a battery powered control circuit and contained within a sealed housing, wherein the device is operable to carry out the method for measuring and / or monitoring fluid levels as disclosed herein. Meanwhile, a system for monitoring fluid levels in a gravity sewer network comprises a plurality of such devices installed in respective manholes of the wastewater network, the devices being in periodic communication with a central processor for reporting fluid levels measured in said manholes.

[0028] There is also disclosed herein, a method for determining fluid level in a wastewater network enclosure (e.g. a manhole) by means of a radar distance sensor installed within the manhole at or near the top thereof, the method comprising performing a fluid level measurement event that includes: executing a plurality of successive radar distance measurements from the radar distance sensor into the manhole; for each of the plurality of successive radar distance measurements, identifying peaks in data representing the strength of radar reflections from surfaces and objects within the manhole together with data representing the corresponding distance of the reflections from the radar sensor; calculating a rate of change of amplitude in respect of the identified peaks over the plurality of successive measurements; and identifying a fluid level corresponding to an identified peak exhibiting a calculated rate of change greater than a predetermined amount.

[0029] In order that the invention may be more readily understood and put into practice, one or more preferred embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings.

[0030] It will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.Brief Description of Drawings

[0031] The invention may be better understood with consideration of the following detailed description, presented by way of example only and with reference to the accompanying drawings, in which:

[0032] FIGURE 1 shows a central vertical cross-section through a pressure sewer tank, incorporating a radar-based fluid level sensing system;

[0033] FIGURE 2 is a cutaway perspective view of a pressure sewer tank as in Figure 1, shown in situ;

[0034] FIGURE 3 is cutaway perspective view of a typical manhole in a gravity sewer network;

[0035] FIGURE 4 is a sectional top view of the typical gravity sewer manhole;

[0036] FIGURE 5 is a sectional front view of the typical gravity sewer manhole;

[0037] FIGURE 6 is a sectional side view of the typical gravity sewer manhole;

[0038] FIGURE 7 is a diagrammatic sectional front view of a gravity sewer manhole fitted with a radar distance sensor according to an embodiment of the invention;

[0039] FIGURE 8 shows a radar distance sensor according to an embodiment of the invention in underside perspective view;

[0040] FIGURE 9 is a sectional illustration of the radar distance sensor seen in overhead perspective view;

[0041] FIGURES 10 (A)-(C) are simplified graphical representations of the output of the radar distance sensor during a fluid measurement event; and

[0042] FIGURE 11 is a flow chart diagram of a fluid level sensing procedure using the radar distance sensor according to an embodiment of the invention.

[0043] FIGURE 12 is a flow chart diagram of a fluid level sensing procedure using the radar distance sensor according to another embodiment of the invention.

[0044] FIGURE 13 is a graphical representation of example output or derived output of the radar distance sensor during a fluid measurement event illustrating signal amplitude.

[0045] FIGURE 14 is a graphical representation of example output or derived output of the radar distance sensor during a fluid measurement event illustrating signal phase angle.

[0046] FIGURE 15 is a flow chart diagram of a fluid level sensing procedure using the radar distance sensor according to a further embodiment of the invention.Detailed Description

[0047] Described embodiments relate to devices, systems and methods to adapted to facilitate accurate sewer monitoring. Some embodiments relate to a sensor unit for sewer monitoring in a manhole. Some embodiments relate to a sewer monitoring system comprising a sensor unit or a plurality of sensor units in communication with a network. Some embodiments relate to a method of installing a sensor unit or a sewer monitoring system.

[0048] Monitoring fluid levels across a gravity sewer network is generally conducted in order to detect rising levels of fluid within the conduits, for example, as a result of blockages within the conduits, before overspill occurs causing damage to the environment and surrounding housing and / or public infrastructure. The specification of international patent publication WO 2016 / 033653, the entire contents of which are incorporated herein by reference, describes systems and methods for monitoring such fluid levels, as well as other relevant parameters. In particular, some embodiments relate to a monitoring system for an access chamber or manhole providing access to a pipe network, the monitoring system including a wireless telemetry unit cooperating with at least one fluid level sensor to determine at least one fluid condition of fluid in a conduit of the pipe network. The wireless telemetry unit may be configured to supply data to be transmitted wirelessly to a remote server or management system.

[0049] By providing such monitoring systems at manholes of pipe networks, fluid conditions of fluid in the manhole and / or conduit may be determined in an efficient and effective manner that minimises power consumption and preserves energy. For example, a threshold fluid level may be indicative of a fluid level of interest in the manhole, whereinwhen the fluid level is below the threshold fluid level, the fluid conduit is deemed to be functioning in an expected manner and when the fluid level reaches or exceeds the threshold fluid level, the fluid conduit is deemed to be functioning in an unexpected manner and it may be desirable for further measurements indicative of the fluid conditions in the manhole to taken for recording purposes and / or to determine whether or not action should be taken immediately or at some time in the future.

[0050] The specification of Australian patent application no. 2021221642 entitled "Fluid- Level Sensing and Monitoring for Wastewater", the entire contents of which are also incorporated herein by reference, discloses a radar-based fluid level sensing system, primarily for use in the context of a pressure sewer tank for controlling the internal pump thereof. Embodiments thereof utilise a non-contact fluid level sensing system incorporating a low power, high precision, pulsed short-range radar sensor. Figures 1 and 2 show an exemplary pressure sewer tank and a pressure sewer system, respectively, including a radar level sensor. The radar level sensor 50 is an in-ground component that is installed within the volume of reservoir 122 near the top of the tank 120 and beneath the tank closure 121.

[0051] The sensor unit 50 is in use supported inside the tank 120, near the top opening, beneath the tank closure 121. The sensor unit 50 includes circuitry contained in a moulded housing. A mounting structure is provided at the rear of the housing for mounting the sensor unit 50 to the inside of the rim 123 of the pressure sewer tank 120 (Figure 1). For example, the mounting structure may be in the form of a plate or flange designed to interfit with existing formations on the rim of the tank or tank closure.

[0052] The sensor unit 50 includes sensing, processing and communications circuitry on a printed circuit board contained within the housing. The sensor unit circuitry includes a high precision, pulsed short-range radar sensor in the form of a one chip system in package (SiP) solution with embedded radio and antenna. The radar sensor emits and receives radio wave signals (represented diagrammatically by arrows 80) by way of a radar lens component 60. The radar sensor does not require an aperture to beam through, in other words, the housing and lens together may be made sealed against fluid ingress. Moreover, the sensor unit circuitry is operated by battery power and communicates wirelessly, meaning that noopenings in the housing are necessary through which to pass power or communication cabling.

[0053] The purpose of the lens 60 is to direct the emissions from the radar sensor, to an extent possible, toward the bottom of the tank and thus toward the surface 141 of fluid 140 in the tank (Figure 1). Reflections of the pulsed radio wave emissions are also detected by the radar sensor and used to determine the distance from the sensor to the reflecting surface (i.e. the fluid surface 141). With prior knowledge of the distance from the mounted sensor to the tank bottom, the measurement made by the radar sensor is representative of the fluid level in the tank.

[0054] The pressure sewer tank 120 has a standardised, preformed structure, wherein the location of internal components such as the pump 124 and the distance from the mounted sensor to the tank bottom are known and consistent from one installation to another. Moreover, the fluid in a pressure sewer tank is generally static (i.e. not flowing), apart from periodic ingress and egress. In contrast, any given manhole in a gravity sewer network may have different internal structure and characteristics as compared to any other manhole in the network. Also, the fluid in the bottom of a gravity sewer manhole is, during ordinary operation, flowing through from inlet(s) to outlet. Embodiments of the present invention provide a radar distance sensor unit, and a method for operation thereof, that enables desired targets (e.g. water, static or flowing) to be readily discerned from the undesired targets (e.g. static objects, manhole ladders, table debris, etc.) within the gravity sewer network without complicating the commissioning process.

[0055] While there can be a great deal of variation from one manhole to another, the features of a typical manhole 300 are shown in Figures 3-6 and outlined below. The manhole 300 as illustrated has vertical walls 302 defining an interior shaft or chamber 304. The channel 306 is a conduit located at the bottom of the manhole for wastewater to flow through from the manhole inlet(s) 308 to outlet 310. The invert 312 is the lowest point of the channel inside the manhole, and the distance between a sewer pipe and a given benchmark, most often the top of the street, is known as the invert elevation. The walls 302 rest on the manhole bench 314 which is the infill concrete poured between the walls of the manhole and the sewer pipes. Its main purpose is to direct flow back into the channel should a back-upoccur in the manhole due to blockage, and it can also be used by maintenance personnel to stand on at the bottom of the manhole when servicing the channel. The chimney 316 of the manhole is the neck of the underground space, connecting the vertical manhole chamber section to a casting frame supporting the manhole lid / cover. Between the chamber and the chimney is a tapering cone section 318. Closing the underground space from the outside are the manhole cover 320 and ring 322. Manhole steps 324, which may be made from concrete, steel or plastic, are steps on the wall of the manhole for personnel to use to safely climb down when inspecting, cleaning or repairing.

[0056] A manhole 300 equipped with a sensor unit 350 according to an embodiment of the invention is shown in Figure 7. The sensor unit 350 is, in use, mounted inside the manhole 300, for instance within the chimney section 316 beneath the manhole cover 320. The sensor unit 350 according to an embodiment of the invention is shown in Figures 8 and 9, and includes circuitry contained in a sealed, moulded housing 352. The housing may include a mounting structure 355 for mounting the sensor unit 350 to the ring 322 or manhole wall, for instance.

[0057] The sensor unit 350 includes sensing, processing and communications circuitry on one or more printed circuit boards 362 contained within the housing. The sensor unit circuitry includes a high precision, pulsed short-range radar sensor 364 in the form of a one chip system in package (SiP) solution with embedded radio and antenna. The radar sensor emits and receives radio wave signals (represented diagrammatically by arrows 380) by way of a radar lens component 360. The radar sensor does not require an aperture to beam through, in other words, the housing and lens together may be made sealed against fluid ingress. Moreover, the sensor unit circuitry is operated from internal electrical power supplied by a battery 366, and is configured to communicate wirelessly by way of an antenna 368, meaning that no openings in the housing are necessary through which to pass power or communication cabling.

[0058] The purpose of the lens 360 is to direct the emissions from the radar sensor, to an extent possible, toward the bottom of the manhole 300. Reflections of the pulsed radio wave emissions are also detected by the radar sensor and used to determine the distance from the sensor to the various reflecting surfaces within the manhole interior, which mayinclude the steps 324, the bench 314, inflow pipes 308 and other components within the manhole, in addition to the surface of the fluid 400. In order to differentiate between the static objects and obstacles in the manhole and the actual surface of the fluid 400 (which is the desired measurement), the sensor unit takes multiple radar sweeps in relative quick succession and compares the resulting measurement data.

[0059] According to an embodiment of the invention, the sensor unit takes multiple (e.g. three) radar sweep readings and records reflected amplitude against individual objects in the manhole including the distance of those objects from the sensor face. Amplitudes recorded against individual objects are then compared across the multiple sweeps to check for variations. If amplitude per sweep varies by a value greater than a pre-determined threshold, then the object is considered as flowing water. If the amplitude variation is less than the predetermined threshold then the object is considered as a stationary component of the manhole i.e. ladder runs, manhole table, manhole chase etc. If the object's amplitude variation is considered static (below variation threshold) but its measured distance places it between the table and the chase bottom (invert level) it can still be considered as the water surface, although not moving. With prior knowledge of the distance from the mounted sensor to the manhole invert, the measurement made by the radar sensor is representative of the fluid level in the sewer at the manhole location.

[0060] Figures 10 (A), (B) and (C) are graphical representations of exemplary outputs of the radar distance sensor over two or three successive sweeps (e.g. three), respectively, useful for illustrating how the operations described above can discern static and moving objects. In these diagrams, the x-axis represents distance from the radar sensor and the y- axis represents the strength of the reflected radar signal corresponding to an object at that distance. As seen in the diagrams, a first peak labelled 385 at a first fixed difference has a substantially constant amplitude across all three sweeps, which represents a fixed object. On the other hand, a second peak labelled 405 at a second fixed distance has an amplitude that varies significantly across the three sweeps, which represents a moving object such as flowing water.

[0061] A flow chart diagram of a procedure 500 for sensing fluid level in a manhole according to an embodiment of the invention is shown in Figure 11. Beginning at operation502, the radar distance sensor is used to generate and record three sample measurements from within the manhole - e.g. data representing the strength of reflected radar pulses corresponding to interpreted distance from the radar sensor, such as illustrated in Figures 10(A)-(C). More than three measurements can be used in this procedure. In some examples, two measurements may be sufficient. The measurements for a single fluid level sensing event are preferably taken in quick succession. For example, the interval between successive sweeps for a single read may be in the order of milliseconds.

[0062] Once the measurements have been recorded, the procedure operates (504) to identify peaks in the measurement samples, corresponding to radar reflections at various distances from the sensor. In a confined space such as a manhole, radar signals emitted from the sensor can reflect off multiple surfaces before being received again, such that some of the measured peaks are artefacts that do not correspond to actual objects. With knowledge of the distance between the invert (the lowest level in the manhole) and where the radar sensor is mounted, at least some of those artefacts can be dismissed by eliminating peaks that register at a distance beyond the invert level (operation 506). The remaining data can then be analysed to assess the interior of the manhole, beginning at operation 508.

[0063] If no peaks are detected across the multiple sample measurements at operation 508, this indicates no radar reflections have been received by the sensor (operation 510). No peaks being detected during the measurement procedure could be due to an error, fault or malfunction in the equipment, such as the radar sensor lens being fouled or obscured. This condition may require attendance by service personnel to resolve.

[0064] During the ordinary course of events, the measurements taken during a fluid level sensing event will result in peaks being detected at operation 508. That being the case, the peaks detected across the multiple sample measurements are analysed at operation 512 so as to determine the rate of change in the magnitude of each peak, as compared between the different measurements. A peak that corresponds to a fixed surface or static object within the manhole shows no significant amplitude variation across the multiple radar measurements. On the other hand, reflections of the radar signal from flowing water in the bottom of the manhole will typically manifest in significant variation of the corresponding measurement peak amplitude.

[0065] If variable peaks are detected at operation 514 the procedure acts to identify the variable peak exhibiting the greatest rate of change at operation 516. Should the peak with the greatest rate of change correspond to a reflection from a surface determined to be above the invert but below the manhole table, this is indicative of a heathy manhole with fluid flow within normal parameters (518). On the other hand, if the peak with the greatest rate of change corresponds to a level that is higher than the manhole table, this is indicative of fluid flow in the manhole that greater than normal (e.g. a surcharge event, 520).

[0066] During commissioning of the radar sensor in a given manhole, measurements are taken and stored that provide a reference spectrum of peaks that correspond to static objects and surfaces in that particular manhole. Then, should no variable peaks be detected from measurements taken during a fluid level sensing event at operation 514, the spectrum containing the static peaks is compared with the reference spectrum for that manhole. If the static peaks from the measurement match the peaks from the reference data, this is indicative of a heathy manhole that simple has not fluid flow at that time (524). On the other hand, if the peaks from the measurement do not match the reference peaks, this may indicate that there is debris in the manhole (526).

[0067] It has been observed that in some instances, particularly when a surface of the fluid is moving slowly, the fluid level may be more reliably and accurately determined based on a change in phase angle of the detected radar signal. As such, another method 600 as executed by a controller coupled to the radar sensor unit 50 for sensing fluid level in a manhole according to another embodiment of the invention will now be described with reference to Figure 12. As referred to herein, a device for monitoring fluid level in a manhole of a wastewater network, may comprise a radar distance sensor and a controller configured to carry out the methods described herein, for example the methods described herein with reference to Figures 10 to 15. The radar distance sensor may be operable by a battery powered control circuit comprising the controller.

[0068] Beginning at step 602, the radar distance sensor 50 is used to generate and record multiple sample measurements from within the manhole (also referred to herein as an access chamber). The radar distance sensor 50 and its associated controller may be configured to perform one or more fluid level measurement events. Each fluid levelmeasurement event may include two or more sample measurements using the radar distance sensor 50. In some embodiments, three sample measurements may be taken. In some embodiments, any two or more sample measurements may be taken. Generally, it has been observed that three measurements are sufficient to achieve results of satisfactory reliability and accuracy. Figures 13 and 14 illustrate example graphs illustrating reflected radar signals detected by the radar distance sensor 50 following the multiple sample measurements. In the particular example shown, three sample measurements were taken. Similarly to method 500 previously described with reference to Figure 11, the measurements for a single fluid level sensing event are preferably taken in quick succession. For example, the interval between successive sweeps may be in the order of milliseconds.

[0069] At step 604, once the measurements have been recorded, the controller such as a microprocessor coupled to the radar distance sensor 50 may be configured to identify amplitude peaks in the detected radar signal corresponding to radar reflections at various distances from the sensor. As illustrated in Figure 13, two amplitude peaks 630, 632 can be detected in the radar signal. A low amplitude peak 630 is present at approximately 1170mm from the radar distance sensor 50, and a high amplitude peak 632 is present at approximately 1350mm from the radar distance sensor 50. As previously mentioned, radar signals corresponding to existing known static objects and surfaces within the manhole may be predetermined and stored in the controller as reference spectrums or reference signal waveforms so that they can be readily identified during live measurements. As such, in the present example shown in Figure 13, the low amplitude peak 630 may be determined to be the manhole table.

[0070] At step 606, with knowledge of the distance between the invert (the lowest level in the manhole) and where the radar sensor 50 is mounted, the controller eliminates any peaks which register at distances beyond the invert level. In Figures 13 and 14, peaks beyond the invert (e.g. greater than 1800mm away from the radar sensor 50) are not shown.

[0071] At query step 608, the controller may identify an amplitude peak in the radar signal if a series of adjacent data points with amplitudes greater than a signal floor (e.g. noise floor) of the radar signal are detected. For example, the controller may be configured to identify amplitude peaks in the radar signal if adjacent data points having an amplitude of atleast three times greater than the noise floor are detected. Generally, the peak distance may be taken to be the highest amplitude data point in the peak. If amplitude peaks are detected in the radar signal, the method 600 proceeds to step 610. If not, the method 600 proceeds to step 626.

[0072] If no peaks are detected across the multiple sample measurements at step 608, it may be determined that there is no fluid flow in the corresponding manhole and that the manhole is functioning effectively at step 626.

[0073] At step 610, the controller determines the phase angle deviation in the radar signal corresponding to each identified peak in step 308. As shown in Figure 14, the phase angle deviation corresponding to peak 630 at approximately 1170mm is negligible. However, a noticeable phase angle deviation 634 corresponding to peak 632 at approximately 1350mm can be detected. The noticeable phase angle deviation 634 indicates that the peak 632 has detected the level of a moving fluid withing the manhole. Typically, the closer that the detected phase angle deviation is to zero, the greater the confidence that the detected object is stationary.

[0074] It has been observed that the phase angle deviation in the radar signal for a fluid, even a very low or imperceptible flow rates, may be orders of magnitude higher than static fixtures in the manhole. Moreover, radar signal amplitude variation may be small to negligible when the fluid surface is moving very slowly, as illustrated in the example in Figures 13 and 14. In some embodiments, data received by the radar sensor unit 50 may be a sequence of complex numbers representing reflected signal by distance as in phase and quadrature values from which the signal amplitude and phase angle may be derived. In one example, the phase angle deviation may be calculated as the standard deviation of the sum of in-phase and quadrature values across all measurements at the distance corresponding to a detected amplitude peak 630, 632.

[0075] Furthermore, the controller may determine a flow rate of the fluid in the manhole based on the detected phase angle deviation. Typically, the greater the phase angle deviation corresponding to an amplitude peak, the greater the flow rate of the detected fluid. Conversely, the smaller the phase angle deviation corresponding to an amplitude peak, the lower the flow rate of the detected fluid.

[0076] At query step 612, if the controller determines that there is noticeable phase angle deviation corresponding to a detected amplitude peak from step 608 as previous discussed, the method 600 proceeds to step 614. If not, the method 600 proceeds to step622.

[0077] At step 614, the controller determines that the fluid level is detected by the distance (e.g. 1350mm from the radar sensor unit 50) corresponding to the amplitude peak 632 having phase angle deviation 634.

[0078] At query step 616, the controller determines whether the fluid level (1350mm) is above the invert and below the manhole table. As previously mentioned, distances between the radar sensor unit 50 and stationary known fixtures in the manhole such as the invert and the manhole table can be predetermined when the system is commissioned for each manhole, and the confirmed distances of the stationary fixtures may be pre-programed and stored in non-volatile memory on the controller. During live measurement events, the controller compares the detected fluid level against distances of stationary fixtures such as the invert and the manhole table and determines whether the detected fluid level is above the invert and below the manhole table. If so, the method 600 proceeds to step 618. If not, the method 600 proceeds to step 620.

[0079] At step 618, the controller determines that the detected fluid level is above the invert and below the manhole table. As such, the controller determines that the corresponding manhole is operating with a healthy level of fluid flow.

[0080] At step 620, the controller determines that the detected fluid level is not below the manhole table. As such, the controller may determine that the corresponding manhole is experiencing a surcharge. In some examples, an alarm and / or notification may be generated to alert maintenance personnel.

[0081] At query step 622, the controller determines whether each of the detected amplitude peaks in step 608 correspond with known static fixtures identified during initial configuration or commissioning of the radar sensor system. If so, the method 600 proceeds to step 626, in which the controller determines that the manhole is operating effectively with no fluid flow (e.g. dry). If not, the method 600 proceeds to step 624.

[0082] At step 624, the controller determines that the fluid level corresponds to the distance measurement registered by the greatest amplitude peak in step 608. In this case, no meaningful phase angle deviation is detected at any of the amplitude peaks. In this scenario, the fluid may be stagnant (not moving). Once the fluid level is determined, the method 600 proceeds to step 616 as previously described.

[0083] In practice, it has been observed that the radar sensor unit 50 may be subject to reflections from the radar sensor lens adjacent the radar sensor. As such, in some embodiments, the controller may be configured to mask or otherwise ignore reflection signals from a certain distance from the radar sensor to radar sensor lens (e.g. 0mm to 250mm). This may enable the controller to effectively eliminate spurious reflections from inside the radar sensor lens.

[0084] However, in some scenarios, when the fluid level in the manhole is close to the radar sensor unit 50 and / or in a shallow manhole, the controller may be adjusted / reconfigured to operate across a different more specific (e.g. smaller) range, which may include the masked range between the radar sensor to the radar sensor lens. In these scenarios, the controller may operate in a specific close-range mode to ensure that suitable measurements can be obtained for further processing to determine the fluid level.

[0085] Alternatively, or in addition, the controller may be configured to modulate gain for the radar signal so that the measured signal waveform is generally within desired maximum and minimum thresholds, so as to improve signal clarity and more effective processing. In this regard, a further method 700 as executed by a controller coupled to the radar sensor unit 50 for sensing fluid level in a manhole according to another embodiment of the invention will now be described with reference to Figure 15.

[0086] In Figure 15, like numerals refer to like method steps previously described with reference to Figure 12. In particular, method steps 602 to 626 are similar to those described in method 600 illustrated in Figure 12.

[0087] As previously described, at steps 602 to 606, the controller operates the radar sensor unit 50 to record multiple sensor measurements in succession (602), identifies anyamplitude peaks (604) and eliminates any peaks registering beyond the known invert level of the manhole (606).

[0088] At query step 702, the controller determines whether it is operating in a 'close range mode' in which the controller is configured to measure across a more specific range of distances closer to the radar sensor lens when compared to standard operating range. The default setting is that the controller is not operating in a 'close range mode'. Moreover, once the method 700 is complete, the controller switches the 'close range mode' to its default setting, being off. If the controller is operating in the 'close range mode', the method 700 proceeds to automatic gain control starting at query step 708. If not, the method 700 proceeds to query step 704.

[0089] At query step 704, the controller determines whether an amplitude peak in the radar signal has been detected within a predetermined distance from the radar sensor lens. In one example the predetermined distance is 500mm. As such, if the controller determines that there is an amplitude peak within 500mm of the radar sensor lens, the method 700 proceeds to step 706. If not, the method 700 does not turn on 'close range mode', and proceeds to automatic gain control starting at query step 708.

[0090] At step 706, the controller sets 'close range mode' as active and returns to step 602 to obtain new sample measurements. In 'close range mode', the controller is reconfigured to focus on and operate over a smaller distance from the radar sensor with low gain, for example, the controller may be reconfigured to operate between 35mm to 500mm from the radar sensor. Typically, the controller may control the power supplied to the radar sensor unit 50 to modulate the gain. To operate the radar sensor unit 50 at low gain, the controller may reduce the power supplied to the radar sensor unit 50 to a predetermined level. Operating the radar sensor unit 50 with low gain may reduce noise in the radar signal, and the effect of echoes as well as reflections from the radar sensor lens. When operating in 'close range mode,' radar sensor measurements (602) may be improved or optimised for detecting fluid levels at shorter distances from the radar sensor unit (50).

[0091] At query step 708, the controller determines whether gain saturation in the received radar signals is present. If so, the method 700 proceeds to step 710. If not, the method 700 proceeds to query step 714.

[0092] At step 710, the controller decreases the gain (e.g. by reducing power supplied to the radar sensor unit 50). In one embodiment, the controller may decrease the gain incrementally by a predetermined amount.

[0093] At query step 712, the controller checks whether a predetermined retry count is exceeded, or whether a minimum or maximum gain (e.g. minimum or maximum power supply levels available from the available power supply) has been reached. If so, the method 700 proceeds to process the radar sensor signals obtained from the most recent sweep of sensor measurements from query step 608 to step 626 as previously described with reference to Figure 12. If the controller determines that the retry count is not exceeded, or that a minimum or maximum gain has not been reached, the method 700 returns to step 602 to obtain a new sweep of measurements using the newly adjusted gain at step 710. Any suitable retry count may be used (e.g. 20) to prevent the controller from being stuck in an infinite loop of gain adjustment. Each time a new sweep of radar sensor measurements is taken in step 602 via the automatic gain control function in steps 708 to 712, the retry count increments. If the controller determines that a maximum retry count is reached or exceeded, the controller exits the gain control function loop, and proceeds to query step 608 with the current radar sensor measurements.

[0094] At query step 714, the controller determines whether the maximum amplitude of the radar sensor signals is above a predetermined high threshold. If so, the method 700 proceeds to step 710 to decrease the gain incrementally. If not, the method 700 proceeds to query step 716.

[0095] At query step 716, the controller determines whether the maximum amplitude of the radar sensor signals is below a predetermined low threshold. If so, the method 700 proceeds to step 718 to increase the gain. If not, the maximum amplitude of the radar sensor signals is between the high and low thresholds and the method 700 proceeds to process the radar sensor signals obtained from the most recent sweep of sensor measurements from query step 608 to step 626 as previously described with reference to Figure 12.

[0096] The high and low thresholds may be determined arbitrarily, for example based on experimental data. The high and low thresholds may be determined to guide the power supply / gain modulation in steps 708 to 712 so as to predominantly maintain the radar sensormeasurements within a desirable range to facilitate interpretation and processing in steps608 to 626.

[0097] The automatic gain control function in steps 708 to 712 dynamically adjusts for improved or optimised signal detection to ensure that the most appropriate level of gain or power is applied to the radar sensor unit 50 to maintain the detected signals within a desirable range. Typically, if the gain is low, relevant weak signals may be missed but noise in the signals is relatively low. Conversely, if the gain is high, weak signals may be amplified, but noise in the signals may also be increased. By adjusting the gain adaptively to maintain the maximum amplitude within upper and lower thresholds, the controller optimises the level of signal and noise amplification. This provides further clarify, accuracy and reliability of sensor signal interpretations.

[0098] The radar level sensor configured for use in gravity sewer manholes as disclosed herein can form part of a monitoring system through use of a wireless telemetry unit configured to wirelessly transmit data relating to fluid level measurements to a remote server or management system. The processing of the multiple sweeps is done internally by the device, so all data processed is internally with only the level of the wanted object reported or a zone alarm A or B depending on the liquid height to the manhole lid (zone alarms are site configured information for spill alarm call ins). The device reports this by 4G NB1 through the mobile phone network from under the manhole lid. Experimentally it has been found that there is signal available even under manholes with 4G NB1 telecommunications system.

[0099] For use in discerning a fluid surface reflection peak from a static object peak, the appropriate threshold may be determined by site visit observations across multiple manholes with varying flow rates and chase sizes, and may also vary depending on the associated gain that is set on the device during commissioning. The interval between successive sweeps during a single fluid level measurement event is only fractions of a second, but the interval between measurements can be configured appropriately, for example between 5 to 60 minutes.

[0100] By providing such monitoring systems at manholes of pipe networks, fluid conditions of fluid in the manhole and / or conduit may be determined in an efficient and effective manner that minimises power consumption and preserves energy. For example, a threshold fluid level may be indicative of a fluid level of interest in the manhole, wherein when the fluid level is below the threshold fluid level, the fluid conduit is deemed to be functioning in an expected manner and when the fluid level reaches or exceeds the threshold fluid level, the fluid conduit is deemed to be functioning in an unexpected manner and it may be desirable for further measurements indicative of the fluid conditions in the manhole to taken for recording purposes and / or to determine whether or not action should be taken immediately or at some time in the future.

[0101] While embodiments of the invention have been described in the context of gravity sewer manholes, the same apparatus, systems and methods can equally be applied for monitoring fluid levels in pressure sewers, in place of the radar-based fluid level sensing system described earlier herein. Accordingly, the term 'wastewater network enclosure' is used herein to encompass both manholes in a gravity sewer system and pressure sewer tanks.

[0102] Embodiments have been described herein by way of example, with reference to various possible features and functions. Such embodiments are intended to be illustrative rather than restrictive. It should be understood that embodiments include various combinations and sub-combinations of features described herein, even if such features are not explicitly described in such a combination or sub-combination.Interpretation

[0103] This specification, including the claims, is intended to be interpreted as follows:

[0104] Embodiments or examples described in the specification are intended to be illustrative of the invention, without limiting the scope thereof. The invention is capable of being practised with various modifications and additions as will readily occur to those skilled in the art. Accordingly, it is to be understood that the scope of the invention is not to be limited to the exact construction and operation described or illustrated, but only by the following claims.

[0105] Moreover, any feature or element described within one embodiment may be combined with any feature or element as described with respect to any other embodiment detailed within this specification, as deemed suitable and appropriate by those skilled in the art.

[0106] The mere disclosure of a method step or product element in the specification should not be construed as being essential to the invention claimed herein, except where it is either expressly stated to be so or expressly recited in a claim.

[0107] The terms in the claims have the broadest scope of meaning they would have been given by a person of ordinary skill in the art as of the relevant date.

[0108] The terms "a" and "an" mean "one or more", unless expressly specified otherwise.

[0109] Neither the title nor the abstract of the present application is to be taken as limiting in any way as the scope of the claimed invention.

[0110] Where the preamble of a claim recites a purpose, benefit or possible use of the claimed invention, it does not limit the claimed invention to having only that purpose, benefit or possible use.

[0111] It should be noted that terms of degree such as "generally", "substantially", "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of the modified term if this deviation would not negate the meaning of the term it modifies.

[0112] In the specification, including the claims, the term "comprise", and variants of that term such as "comprises" or "comprising", are used to mean "including but not limited to", unless expressly specified otherwise, or unless in the context or usage an exclusive interpretation of the term is required.

[0113] Furthermore, the recitation of any numerical ranges by endpoints herein includes all numbers and fractions subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.90, 4, and 5). It is also to be understood that all numbers and fractions thereof are presumed to be modified by the term "about" which means a variation up to a certain amount of the number to which reference is being made if the end result is not significantly changed.

[0114] As used herein, the wording "and / or" is intended to represent an inclusive-or.That is, "X and / or Y" is intended to mean X or Y or both, for example. As a further example, "X, Y, and / or Z" is intended to mean X or Y or Z or any combination thereof.

[0115] Throughout the specification, like reference numerals refer to like features described herein. As such, any instance where features or components are indicated with the same references implies a direct correlation to the similar or identical features or components as previously described in the specification.

[0116] The disclosure of any document referred to herein is incorporated by reference into this patent application as part of the present disclosure, but only for purposes of written description and enablement and should in no way be used to limit, define, or otherwise construe any term of the present application where the present application, without such incorporation by reference, would not have failed to provide an ascertainable meaning. Any incorporation by reference does not, in and of itself, constitute any endorsement or ratification of any statement, opinion or argument contained in any incorporated document.

Claims

The claims defining the invention are as follows:

1. A method for determining fluid level in a wastewater network enclosure by means of a radar distance sensor installed within a manhole at or near the top thereof, the method comprising performing a fluid level measurement event that includes: executing a plurality of successive radar distance measurements from the radar distance sensor into the wastewater network enclosure; for each of the plurality of successive radar distance measurements, identifying peaks in data representing the strength of radar reflections from surfaces and objects within the wastewater network enclosure together with data representing a corresponding distance of the reflections from the radar sensor; determining a fluid level of a fluid corresponding to an identified peak based on either one or both of an amplitude of the identified peak, and phase angle deviation corresponding to the identified peak.

2. The method of claim 1, including determining a moving surface of the fluid in the wastewater network enclosure based on the phase angle deviation corresponding to the identified peak.

3. The method of claim 1 or claim 2, wherein determining the fluid level of the fluid includes determining a phase angle for each identified peak of each radar distance measurement, determining the phase angle deviation between the determined phase angles for each identified peak across all successive radar distance measurements in each measurement event, and identifying a distance corresponding to the identified peak having a highest phase angle deviation.

4. The method of any one of the preceding claims, further including eliminating any peaks in the data registering at a distance from the radar distance sensor beyond a depth of the wastewater network enclosure.

5. The method of any one of the preceding claims, further including determining a surcharge event when the fluid level exceeds a predetermined maximum fluid threshold level.

6. The method according to any one of the preceding claims, further including determining a relative flow rate of the fluid in the wastewater network enclosure based on the phase angle deviation corresponding to the identified peak, wherein a greater phase angle deviation is indicative of a higher flow rate, and a smaller phase angle deviation is indicative of a lower flow rate.

7. The method of any one of the preceding claims, further including reducing a power supply to the radar distance sensor in response to identifying a peak within a predetermined distance from the radar distance sensor.

8. The method of claim 7, further including reducing a scanning distance of the radar distance sensor in response to identifying a peak within the predetermined distance from the radar distance sensor.

9. The method of any one of the preceding claims, including adjusting power supplied to the radar distance sensor based on upper and lower thresholds to adjust a gain applied to the radar distance measurements.

10. The method of any one of the preceding claims, wherein at least two successive radar distance measurements are used in each fluid level measurement event.

11. The method of any one of the preceding claims, further including transmitting to a central processor wastewater network enclosure status data and / or operational parameters determined from the radar distance measurements.

12. The method of claim 8, further including transmitting to the central processor a fluid level in the wastewater network enclosure as determined from the radar distance measurements.

13. The method of any one of the preceding claims, including a commissioning procedure wherein the radar sensor is installed in the manhole at a known height above a manhole invert level.

14. The method as claimed in claim 13, wherein the commissioning procedure includes recording reference peaks representing radar distance measurements in respect of static surfaces and / or objects in the manhole.

15. The method as claimed in claim 14, further including comparing the peaks identified in a fluid level measurement event with the reference peaks to identify debris or other extraneous static material in the manhole.

16. A method for monitoring fluid level in a manhole of a wastewater network by: installing a radar distance sensor within the manhole at or near the top thereof; performing a fluid level measurement event to determine a fluid level in the manhole according to the method of any one of claims 1 to 15.

17. A method for monitoring fluid levels in manholes comprising part of a wastewater network by: installing respective radar distance sensors within a plurality of manholes of the wastewater network; performing a fluid level measurement event to determine a fluid level in each of the respective manholes according to the method of any one of claims 1 to 15; and reporting the determined fluid levels in the respective manholes to a central processor.

18. A method for monitoring fluid levels in manholes comprising part of a wastewater network, as claimed in claim 17, wherein the operations of performing a fluid level measurement event and reporting the determined fluid levels are performed periodically.

19. A device for monitoring fluid level in a manhole of a wastewater network, comprising a radar distance sensor operable by a battery powered control circuit and contained within a sealed housing, wherein the device is operable to carry out the method of any one of claims 1 to 12.

20. A system for monitoring fluid levels in a gravity sewer network comprising a plurality of devices according to claim 19 installed in respective manholes of the wastewater network, the devices being in periodic communication with a central processor for reporting fluid levels measured in said manholes.

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