An apparatus and method for utrasonic sensing

Abstract

A fluid sensing apparatus for monitoring a fluid comprising: an ultrasonic sensor comprising a plurality of ultrasonic transducer elements arranged to emit and receive ultrasonic waves with a plurality of polarisations and / or frequencies, wherein the ultrasonic sensor is configured to generate a sensor output signal based on the received ultrasonic waves; a backing plate, wherein the ultrasonic transducer elements are mounted on the backing plate; and a control system configured to: receive the sensor output signal from the ultrasonic sensor; and calculate at least one property of a fluid, wherein the at least one property is calculated based on the received sensor output signal during a sample testing time-domain window.

Description

[0001] P610131PC00

[0002] An Apparatus and Method for Sensing

[0003] Field

[0004] The present teachings relate to a fluid sensor apparatus comprising an ultrasonic sensor.

[0005] Background

[0006] It is advantageous to understand the real-time condition of a fluid across a variety of industrial sectors. Monitoring the properties of fluid products and industrial process fluids is critical to ensuring efficient and successful operations and outcomes. Current methods for understanding fluid properties most commonly involve sampling and laboratory analysis. However, this has many disadvantages including requiring significant manual intervention which can be prone to operator variability and can increase time required and costs of testing whilst ultimately being limited by the frequency of sampling.

[0007] In-line sensors are known. However, they rely on sensor products with limited use by monitoring a single property such as electrical conductivity or impedance. These systems are disadvantageous as they are not reliable forms of monitoring when multiple properties are changing in a fluid such as a highly complex single-phase or multi-phase fluid stream, or when properties do not exhibit a monotonic change.

[0008] The present teaching seeks to provide an improved fluid sensor apparatus.

[0009] Summary

[0010] In accordance with a first aspect, there is provided a fluid sensing apparatus for monitoring a fluid comprising: an ultrasonic sensor comprising a plurality of ultrasonic transducer elements arranged to emit and receive ultrasonic waves with a plurality of polarisations and / or frequencies, wherein the ultrasonic sensor is configured to generate a sensor output signal based on the received ultrasonic waves; a backing plate, wherein the ultrasonic transducer elements are mounted on the backing plate; and a control system configured to: receive the sensor output signal from the ultrasonic sensor; and calculate at least one property of a fluid, wherein the at least one property is calculated based on the received sensor output signal during a sample testing time-domain window.

[0011] Therefore, a means to accurately and completely characterise industrial process and product fluids in a real-time, cost effective, robust, and non-invasive way is provided.In turn, this allows for optimisation of fluid properties and processes, reduction of risk, and minimisation of waste.

[0012] Specifically, a means to identify fluid types and grades, measure parameters under actual processing conditions, and provide real time measurements for instant feedback and process control is provided. Such means can provide a scalable system by arranging a plurality of the fluid sensing apparatus within a processing system which allows for characterization of large volumes of fluids. A means to characterise the entire fluid rather than sampling and testing the fluid in batches is also provided.

[0013] Fluids can be purposefully complex and highly engineered such as with fully formulated lubricants which contain a variety of additives to achieve desired properties, or they can naturally be complex in their nature such as a fluid within an anaerobic digester that contains a complex mixture of organic matter in various stages of decomposition. Fluids can also be simple in their nature such as with pure methanol as a fuel source.

[0014] The precision and adaptability of ultrasonic techniques make them a reliable tool in the analysis of complex fluids. For example, in drug formulation, ultrasonic techniques can monitor the molecular weight of fluids in real-time, ensuring the consistency and quality of drug delivery systems. Complex fluids are also used in the food and beverage industry. In this industry, ultrasonic detection may be used to determine the molecular weight of additives or entrained species in liquids, gaseous, or multi-phase fluid systems, ensuring the correct formulation and improving the quality control process. Complex fluids are used in the oil and gas industry. In this industry, ultrasonic detection may be used in the measurement of the molecular weight of liquid or gaseous hydrocarbons. Complex fluids may also be used in environmental monitoring. Here ultrasonic sensors can be used to track pollutants in water bodies by analysing the molecular weight of dissolved organic matter, providing crucial data for environmental assessments. Complex fluids are also used in semiconductor manufacturing, biomedical industries, healthcare, internal combustion engines, and water / wastewater.

[0015] The sensor may be applied to standard fluids, high viscosity fluids, highly compressible gaseous fluids, or fluids undergoing thermodynamic phase transitions, including but not limited to solidification, crystalisation, condensation, evaporation, sublimination or deposition.

[0016] The sample testing time-domain window may be predetermined. This may be based on the arrangement of ultrasonic transducer elements used, the polarisation of theultrasonic transducer elements, the fluid being monitored, and / or the size / material of the ultrasonic sensor.

[0017] The ultrasonic sensor may further comprise: a reflector body arranged such that the ultrasonic waves are transmitted through said reflector body, wherein the ultrasonic waves are reflected off a boundary of the reflector body back towards the ultrasonic transducers.

[0018] The reflector body may be mounted to the backing plate, wherein reflector body has a thickness such that it extends beyond the ultrasonic transducer elements so that the emitted ultrasonic waves travel through the reflector body and are reflected at a boundary between the reflector body and a fluid to be monitored, wherein the reflection is during the sample testing time-domain window.

[0019] The ultrasonic sensor may further comprise a reference feature, wherein the reference feature defines a boundary with the reflector body.

[0020] Each ultrasonic transducer element may be arranged to receive reflected ultrasonic waves emitted from a different transducer element.

[0021] The ultrasonic sensor may comprise a second plurality of ultrasonic transducer elements which are configured to receive ultrasonic waves without actively emitting ultrasonic waves.

[0022] The ultrasonic sensor may comprise at least one of: an ultrasonic longitudinal wave transducer configured to transmit an ultrasonic longitudinal wave and to receive the ultrasonic longitudinal wave signal reflected from a boundary; and an ultrasonic shear wave transducer configured to transmit an ultrasonic shear wave and to receive the ultrasonic shear wave signal reflected from a boundary.

[0023] The ultrasonic sensor may oscillate in radial, thickness, flexural, longitudinal or shear mode. For example, the ultrasonic sensor may oscillate in the plane of the face of the transducer and / or may oscillate in a transverse direction. A disc or ring ultrasonic sensor may oscillate in a radial direction.

[0024] The ultrasonic sensor may comprise a plurality of ultrasonic transducer elements arranged in a co-planar configuration, or alternatively, distributed across a plurality of planes in diverse spatial orientations.

[0025] The reference feature may be embedded within the reflector body.

[0026] The reference feature may be an air gap or known material extending only partially across the path of the emitted ultrasonic wave such that a first proportion of the emitted ultrasonic waves do not interact with the reference feature and a second proportion ofthe emitted ultrasonic waves are reflected at the boundary between the reflector body and the reference feature.

[0027] The reference feature may abut an external layer of the reflector body or may be at least partially covering an external layer of the reflector body.

[0028] The reference feature may be configured so that the emitted ultrasonic waves are partially reflected at the boundary between the reflector body and the reference feature and are partially transmitted through the reference feature.

[0029] The fluid sensing apparatus may further comprise an acoustically tuned reflector layer arranged between the reference feature and the boundary to the fluid being monitored. The control system may be further configured to calculate at least one property of the reference feature, wherein the at least one property is calculated based on the received sensor output signal during a reference testing time-domain window, wherein the reference testing time-domain window is distinct from the sample testing time-domain window; and compare the calculated at least one property of the reference feature with a known value of the at least one property to calibrate the ultrasonic sensor.

[0030] The reference testing time-domain window may be predetermined. This may be based on the arrangement of ultrasonic transducer elements used, the fluid being monitored, the size / material / arrangement of the reference feature and / or the size / material of the ultrasonic sensor.

[0031] The at least one property may be calculated based on a change in amplitude of the reflected ultrasonic waves for different ultrasonic wave polarisations and / or frequencies. The at least one property may be calculated based on a change in the time-of-flight of the reflected ultrasonic waves for different ultrasonic wave polarisations and / or frequencies.

[0032] The at least one property may be calculated based on a change in phase of the reflected ultrasonic waves for different ultrasonic wave polarisations and / or frequencies.

[0033] The at least one property may be calculated based on a comparison of the reflected ultrasonic waves detected by a transducer element distinct from the emitting transducer element.

[0034] The at least one property may be calculated based on reflected ultrasonic waves only. The ultrasonic sensor may be configured to be removably couplable to a fluid chamber and / or flow line.The ultrasonic sensor may be configured to be embedded into a fluid chamber manifold and / or flow line manifold.

[0035] The ultrasonic sensor may be on a probe wand configured to be inserted into a fluid to be monitored.

[0036] The acoustic impedance of the acoustically tuned reflector layer may have an acoustic impedance gradient between the transducer and the boundary to the fluid to be monitored. For example, the acoustic impedance of the acoustically tuned reflector layer may be greater at the side closer to the transducer than at the side closer to the boundary to the fluid to be monitored. The acoustic impedance of the acoustically tuned reflector layer may be lower at the side closer to the transducer than at the side closer to the boundary to the fluid to be monitored.

[0037] The ultrasonic sensor may further comprise surface wave transducers configured to emit surface waves with a plurality of polarisations and / or frequencies.

[0038] The ultrasonic sensor may comprise a bifurcation wherein a first ultrasonic transducer array is arranged on a first portion of the bifurcation and a second ultrasonic transducer array is arranged on a second portion of the bifurcation. The ultrasonic sensor may form a fixed gap between the first portion of the bifurcation and the second portion of the bifurcation. The ultrasonic sensor may comprise a reflector body arranged between the first portion of the bifurcation and the second portion of the bifurcation. The reflector body may have a varying thickness along the length of the bifurcation. Therefore, the gap between the two portions of the bifurcation may vary along the length of the bifurcation.

[0039] The ultrasonic sensor may comprise at least one instrumented foil, wherein the instrumented foil comprises the ultrasonic transducer array. The ultrasonic sensor may comprise a plurality of instrumented foils, wherein instrumented foils are arranged adjacent and / or opposing each other to define a gap between instrumented foils. The ultrasonic sensor may comprise a reflector body arranged in the path of ultrasonic waves emitted by the instrumented foil(s).

[0040] In accordance with a second aspect, there is provided a method of determining at least one property of a fluid using a fluid sensing apparatus comprising an ultrasonic sensor, a backing plate, and a control system according to any preceding claim, the method comprising: emitting ultrasonic waves having a plurality of polarisations and / or frequencies from a plurality of ultrasound transducer elements; receiving ultrasonic waves having a plurality of polarisations and / or frequencies, wherein the received ultrasonic waves have reflected from a boundary between the ultrasonic sensor and fluid; generating a sensor output signal based on the received ultrasonic waves; andtransmitting the sensor output signal to a control system, wherein the control system is configured to calculate at least one property of the fluid, wherein the at least one property is calculated based on the received sensor output signal during a sample testing time-domain window.

[0041] The method may further comprise: generating a control signal based on the at least one property calculated; transmitting the control signal to a component of a fluid processing system, wherein the component may be a display, a memory device, a further control system, a heating element, a mechanical stirrer, a dosing system, an actuator, a valve, a pump, a diverter and / or a pressure regulator.

[0042] In accordance with the first aspect and / or second aspect, the following examples may be provided:

[0043] The at least one property may be acoustic impedance, speed of sound, specific gravity, kinematic viscosity, particulate content, elemental analysis, and / or slurry agglomeration characterisation. The control signal may be transmitted to downstream valves which may actuate the valves to dynamically route the fluid into onward sorting or directly into collection vessels when a threshold is met. The fluid may be directed into recirculation loops if further processing is required.

[0044] The at least one property may be phase velocities and / or molecular relaxation peaks. These acoustic profiles may be iteratively cross-referenced against equations of state and critical constants to quantify individual gas species within a gas sample. The control signal may be transmitted to a control unit (such as an Engine Control Unit, ECU, when used for internal combustion engine exhaust monitoring). The control signal may indicate that the measurement of the gas species is greater than a threshold which indicates that an acceptable limit has been breached. The ECU may transmit further signals to optimise engine conditions such as by dynamically trimming fuel injector pulse durations and modulating the exhaust gas recirculation valve. This can provide a continuous closed-loop suppression of unwanted emissions.

[0045] The at least one property may be kinematic viscosity (derived from simultaneous density and dynamic viscosity tracking), the decoupled quantification of bubble and particulate content derived from shear and longitudinal attenuation profiles, and / or molecular weight derived from frequency dependant acoustic attenuation spectroscopy. The control signal may be transmitted to a Programmable Logic Controller (PLC) to execute automated closed-loop interventions. In a primary feedback configuration, the PLC may implement a Proportional-Integral-Derivative (PID) control algorithm to adjust a Variable Frequency Drive (VFD) on a component such as a sludge transfer pump. This can optimise energy efficiency and prevent blockages. In a secondary configuration, thePLC may implement flow-paced feedforward logic combined with a PID feedback trim. The component controlled may be chemical metering pumps.

[0046] The at least one property may be phase velocity and / or a molecular relaxation peak. These acoustic profiles may be iteratively cross-referenced against equations of state and critical constants to quantify individual gas species within a gas sample. The control signal may be transmitted to a control unit to quantify individual gas species within the gas mixture. Mixture concentrations may be identified by deriving adiabatic compressibility from fluid density and acoustic velocity. The component may be a valve to halt gas flow into a process chamber if the gas mixture is outside of an acceptable threshold. For example, in semiconductor fabrication, the dilution ratio of a critical etchant gas blend at the Point-of-Use immediately preceding a semiconductor dry etching chamber may be monitored using the ultrasonic sensor. The at least one property may be acoustic impedance and / or acoustic velocity to determine the molar fraction of the blend. In a further example, the at least one property may be physical properties of a precursor vapour mixture within a heated delivery conduit disposed downstream of a vapourising vessel or bubbler. Therefore, the at least one property may be a mixture ratio and / or a molecular weight of the vapour stream to determine the real-time concentration of a precursor. This may be used to determine compositional anomalies indicative of thermal degradation, premature condensation, or oligomerisation of the precursor molecules. The control signal may be transmitted to heating elements operably coupled to the vapourising vessel or the associated delivery conduits. Therefore, the precursor vapour pressure may be optimised to stabilise the desired mixture ratio, thereby mitigating thin-film deposition defects while actively preventing the thermal breakdown of the precursor material.

[0047] The at least one property may be the speed of sound, acoustic impedance, precursor mass density, kinematic viscosity, shear-dependent viscosity, and / or viscoelastic moduli. The control signal may be transmitted to a valve to divert fluid. For example, an elevated inferred molecular weight or particulate content indicating a degraded precursor batch may trigger a pneumatic diverter valve to automatically lock out the fluid from a semiconductor manufacturing process.

[0048] The at least one property may be density, viscosity, speed of sound, and / or flow rate. A control system may determine acoustic impedance, absolute density, dynamic viscosity, magnitude and / or phase shift. The control signal may be transmitted to heating elements, a pressure regulator, and / or an actuator. This may be used in Extreme Ultraviolet (EUV) lithography to maximise the conversion efficiency of the CO2 laser-produced plasma and mitigate particulate degradation of the EUV collector optics.The at least one property may be specific gravity, osmolarity, pH, conductivity, density, viscosity, bacterial or particle counts, and / or protein composition. The control signal may be transmitted to a display, memory device, and / or a further control system. The sensor assembly can be used to detect clinical parameters from fluid samples such as blood, urine, saliva, sweat, and / or tears. In such systems it is advantageous to use acoustic mode conversion by implementing a reflector body comprising an angled surface at the boundary interfacing the fluid.

[0049] The at least one property may be shear-dependent viscosity, complex moduli, and / or compressibility / microbubbles. The control signal may be transmitted to spin-coating components to control RPM, a pump to control volumetric rates, and / or a valve to control bubble-triggered purge.

[0050] The at least one property may be acoustic impedance, time-of-flight, and / or frequency sweeps to determine absolute thermodynamic density (tracking refractive index and contamination) and bulk compressibility (detecting cavitation). The control signal may be transmitted to a valve to adjust temperatures and / or flushing of a system.

[0051] The at least one property may be shear-rate-dependent complex viscosity, density, and / or phase angle of the fluid. The control signal may be transmitted to a valve and / or pump.

[0052] The at least one property may be acoustic impedance, compressibility, and / or attenuation spectra which may be used to determine mix ratio, detect agglomerations, and / or characterise microbubbles. The control signal may be transmitted to a further controller to control PID-driven chemical spiking, a valve to control pneumatic flow diversion for agglomerates, and / or a further control system to suspend endpoint metrology when microbubbles appear.

[0053] Brief Description of the Drawings

[0054] By way of example only, certain embodiments will now be described by reference to the accompanying drawings, in which:

[0055] Figure la is a diagram of an exemplary fluid sensing apparatus;

[0056] Figure lb is a diagram of an exemplary fluid sensing apparatus;

[0057] Figures 2a-2e are diagrams of exemplary arrangements of ultrasonic transducers which form multimodal ultrasonic sensors;

[0058] Figures 3a-3c are diagrams of exemplary arrangements of ultrasonic transducers which form multi-frequency ultrasonic sensors;

[0059] Figure 4 is a diagram of an exemplary arrangement of ultrasonic transducers on an acoustically tuned backing plate;Figures 5a-5d are diagrams of exemplary fluid sensing apparatus comprising a reflector body;

[0060] Figures 6a and 6b are diagrams of exemplary fluid sensing apparatus comprising a reference feature;

[0061] Figure 7 is a diagram of an exemplary fluid sensing apparatus;

[0062] Figure 8 is a diagram of an exemplary fluid sensing apparatus;

[0063] Figure 9 is a diagram of an exemplary fluid sensing apparatus;

[0064] Figure 10 is an exemplary method of operating a fluid sensing apparatus;

[0065] Figure 11a is a diagram of an exemplary fluid sensing apparatus;

[0066] Figure lib is a diagram of an exemplary fluid sensing apparatus;

[0067] Figure 12a is a diagram of an exemplary fluid sensing apparatus; and Figure 12b is a diagram of an exemplary fluid sensing apparatus.

[0068] Detailed Description

[0069] Figure la shows a fluid sensing apparatus 10 comprising an ultrasonic sensor shown generally at 20 and a control system 14. The fluid sensing apparatus 10 can be used to monitor a fluid 16 contained in a chamber, vessel, or flowline 12. The chamber, vessel, or flowline 12 is hereinafter referred to as the chamber but can encompass any structure supporting a body of fluid. The ultrasonic sensor 20 includes a plurality of ultrasonic transducer elements 22, 24 arranged to emit ultrasonic waves with a plurality of polarisations and receive ultrasonic waves with a plurality of polarisations.

[0070] The ultrasonic sensor 20 may refer to a general sensing apparatus which comprises the individual components which enable the sensing apparatus to carry out a detection. Such components include the sensor housing, cabling, and the plurality of ultrasonic transducer elements which can generate an ultrasonic wave and the plurality of ultrasonic transducer elements which can detect an ultrasonic wave. The ultrasonic sensor 20 is arranged to produce an ultrasonic wave and direct the ultrasonic wave towards the fluid being monitored. The ultrasonic sensor 20 may be arranged to receive an ultrasonic wave from the fluid being monitored and / or a boundary of the fluid. For example, the ultrasonic wave may be transmitted through the fluid and reflect from a wall of the chamber 12. The reflected ultrasonic wave is received at and detected by the ultrasonic sensor 20.

[0071] The received ultrasonic wave may be detected by a transducer which forms part of the ultrasonic sensor 20. The transducer may be the same transducer which generates an ultrasonic wave or may be a different transducer within the sensor assembly. The received wave may include data relating to properties of the fluid. The data may betransmitted to the control system 14. This may be carried out by the ultrasonic sensor 20 generating a signal indicative of at least one property of the fluid. The signal is a sensor output signal 26 and may be indicative of at least one of the following properties:

[0072] Gas / Moisture, Bubble and Particulate Content C Attenuation a

[0073] Compressibility (3

[0074] Bulk Modulus k

[0075] Density p

[0076] Solidification / crystallization

[0077] Particle Orientation Relative

[0078] Particle Size d

[0079] Particle Count N

[0080] Viscosity rp

[0081] Shear-Dependent Viscosity ? / (y)

[0082] Inferred Molecular Weight Mw

[0083] Acoustic Impedance z

[0084] Moisture (Water) content

[0085] Bulk viscosity p

[0086] Acoustic Velocity c

[0087] 2 Phase flow

[0088] Fluid degradation / Contamination D

[0089] Flow Rate v

[0090] Storage Modulus M'Loss Modulus M"

[0091] Relaxation Time T

[0092] Surface Tension a

[0093] Contact Angle QcTherefore, the ultrasonic sensor may be configured to generate a sensor output signal 26 indicative of at least one property of the fluid by emitting an ultrasonic wave and receiving an ultrasonic wave which has interacted with the fluid.

[0094] The at least one property is calculated based on the sensor output signal 26 received during a sample testing time-domain window. This time-domain window is the time period during which the sensor output is used to calculate the at least one property of the fluid. Outside of this time period the sensor output may be being generated and sent to the control system without the at least one property being calculated.

[0095] The control system 14 may be configured to calculate the at least one property based on the signal 26 which is indicative of the property and may be configured to generate a control system output signal (not shown) corresponding to the at least one property of the fluid. The control system output signal may be transmitted to components of a system for processing the fluid. For example, an apparatus for controlling properties of the fluid and / or fluid processing apparatus. Therefore, the control system output signal may transmit operational commands to components of the apparatus based on the signal 26 indicative of a property of the fluid. The control system 14 may be in wired (as shown) or wireless communication with the ultrasonic sensor 20. The control system 14 may be in wired or wireless communication with other components of the fluid processing system.

[0096] A plurality of the fluid sensing apparatus 10 may be arranged with a fluid processing system.

[0097] Figure lb shows a fluid sensing apparatus 30 comprising an ultrasonic sensor shown generally at 40 and a control system 14. The fluid sensing apparatus 30 is substantially similar to apparatus 10 and can be used to monitor a fluid 16 contained in a chamber 12. The ultrasonic sensor 30 comprises a plurality of ultrasonic transducer elements 42 arranged to emit ultrasonic waves with a plurality of frequencies and receive ultrasonic waves with a plurality of frequencies. All other components of the fluid sensing apparatus 30 are the same as those described in relation to the fluid sensing apparatusThe fluid sensing apparatus 10, 30 may be combined to provide an ultrasonic sensor comprising a plurality of ultrasonic transducer elements arranged to emit ultrasonic waves with a plurality of frequencies and polarisations and receive ultrasonic waves with a plurality of frequencies and polarisations.

[0098] Varying ultrasonic wave modes can be emitted and received by the ultrasonic sensors, for example, surface or Rayleigh wave modes have an elliptical particle motion and travel across the surface of a material. Plate wave modes such as Lamb and Love waves have a complex vibration occurring in materials where the thickness is less than the wavelength of the ultrasonic wave. The most commonly used modes are Longitudinal and Shear bulk waves, which travel through the bulk of the propagating media. The ultrasonic sensors may oscillate in radial, longitudinal, shear or flexural modes.

[0099] Longitudinal waves are a compression wave in which the particle motion is in the same orientation as the propagation of the wave. The particle motion forms successive areas of compression and rarefaction. For shear waves the particle motion is perpendicular to the direction of the propagation. The orientation of the lateral particle motion of a shear wave is known as its polarisation.

[0100] The manner in which the different modes propagate through a medium is sensitive to different characteristics of the medium, for example shear waves are very sensitive to the materials shear stiffness, while a longitudinal wave is sensitive to its compressibility or normal stiffness. This makes different waves suitable for measuring different material characteristics.

[0101] Typically, a wave is transmitted through a material and captured either by the transmitting transducer or a second, receiving transducer. The wave may reflect from a boundary before the wave has interacted with the material or may reflect from a boundary after the wave has interacted with the material. Three key measurements can be made of the captured wave: its amplitude, phase, and transit time through the material (commonly referred to as the Time-of-Flight or ToF). The value reported from these measurements will vary depending upon the wave path, mode, polarisation, frequency and the propagating medium properties. The wave path, mode, polarisation, frequency can be controlled through selection of the ultrasonic transducer, the transducer excitation signal and its mounting approach. This leaves the propagating medium properties as variables to be measured.

[0102] Regardless of the wave type, ultrasonic signals are commonly represented by a timedomain plot of the wave amplitude. This may then be converted to the frequency domain using a Fast Fourier Transform (FFT) which will yield amplitude-frequency and phasefrequency plots.When an ultrasonic signal reaches the boundary between two acoustically dissimilar materials the proportion of wave reflected from and transmitted by the interface can be characterised by the dimensionless reflection and transmission coefficients (R and T respectively) as given below:

[0103]

[0104] where zi and zi are the acoustic impedances of the materials either side of the interface. The acoustic impedance forms a relation between the density of a material, p, and the velocity of sound within the material, v: z =pv. The amplitude of a wave emanating from the boundary (either transmitted by or reflected from) is therefore a function of the material properties either side of that boundary.

[0105] As a wave travels through a bulk material it will also attenuate. This occurs due to three effects: Absorption, Scattering and Beam Spread. Absorption is the conversion of acoustic energy to other forms of energy. In liquids, a common example is the conversion of acoustic energy to thermal energy caused by the internal viscosity of the material. In gases and compressible fluids, absorption is heavily influenced by the thermal conduction and molecular relaxation of the material, wherein the ultrasonic pressure pulse locally disturbs the equilibrium between the translational kinetic energy of the molecules and their internal rotational and vibrational modes. Scattering is the reflection of the wave away from the direction of wave propagation, which is highly pronounced in multi-phase flows where the acoustic impedance severely mismatches between continuous and dispersed phases, meaning the wave is dispersed and is not captured by the receiving transducer. Beam spread is the divergence of an ultrasonic wave as it propagates through a medium, this reduces the intensity of the wave at any given point. Due to the above effects, measuring the change in amplitude of an ultrasonic signal can be used to interrogate a range of material properties and conditions.

[0106] The change in amplitude can be obtained by extracting the peak-value from the timedomain representation of the wave. The change in amplitude can also be obtained by performing an FFT on the time-domain signal and by calculating the change in the transformed values from the frequency-domain curve. The same approaches apply equally to the measurement of both longitudinal and shear wave signals.

[0107] Wave phase offers a further possible method to measure material properties and condition. This measurement is of particular interest for waves reflected from thematerial interface. A phase change can be observed in the waveform time domain representation or from the phase-frequency output of an FFT.

[0108] The amount of time a wave takes to propagate through a medium, a function of the distance travelled and the medium's acoustic velocity, is known as the Time-of-Flight (ToF). The change in time-of-flight is obtained by measuring the time difference between two waveforms in the time-domain plot. The two waveforms may be a reference signal and measured signal and relating to a boundary of the fluid being monitored.

[0109] Most ultrasonic signals emitted from a 'single frequency' transducer comprise a range of frequencies, with the centre frequency relating to the peak frequency of the transducer and the range of the frequency content within the signal termed the transducer bandwidth. The amplitudes and phases of each frequency that make up a wave can be extracted using a Fast Fourier Transform (FFT).

[0110] Figures 2a-2e and 3a-3c show exemplary arrangements of ultrasonic transducers which can form ultrasonic sensors. The sensors of Figures 2a, 2d, 2e, 3b, and 3c are shown end on so that the surface shown in the figures faces outwards, towards the fluid being measured.

[0111] A transducer assembly may comprise a plurality of elements which produce multiple wave modes or polarisations simultaneously in the same sensor housing by using both shear and longitudinal ultrasonic transducer elements mounted on the same backing layer / plate. The ultrasonic sensor shown in Figure 2a comprises an assembly of one longitudinal wave transducer 52 and one shear wave transducer 54 arranged linearly on a backing plate 50. The same ultrasonic sensor is shown side on in Figure 2b.

[0112] Measurements from the two transducer types may be taken at the same time and the outputs of each transducer can be compared in order to extract additional measurements of the fluid under inspection. The use of two transducers may provide two sensor output signals, one from each transducer. The multiple sensor output signals may be captured at the same time in parallel or near parallel. The responses from the multiple signals can be captured on the same control system, such as an electronic control and data storage system. The multiple data sets may then be used together to obtain the desired measurement output.

[0113] The ultrasonic transducers described herein may be a piezoelectric or Electro Magnetic Acoustic Transducer (EMAT) in either longitudinal, shear, mode converted shear, plate or surface wave type. A mode converted shear sensor may be arranged such that the ultrasonic transducer array emits longitudinal waves which are converted to a shear wave at a boundary. Shear waves may be transmitted through the boundary and interact with the fluid before being reflected back towards the transducer array via theboundary. The shear waves which are passing back through the boundary are converted to longitudinal waves at the boundary. Therefore, the transducer array receives longitudinal waves. This arrangement enables shear waves to be produced using transducer arrays which can only provide longitudinal waves. The ultrasonic transducers may also be arranged in a wedge, comb, direct-write transducer (DWT) or a capacitive or piezoelectric micromachined ultrasonic transducer (cMUT / pMUT) form factor. The transducers may be laser transducers, Fibre-Bragg transducers or any other suitable ultrasonic transducers. A wedge transducer is particularly advantageous for creating a shear transducer via mode conversion. This may be achieved by providing a reflector body at a solid boundary. The reflector body may interface with a known geometry gap at an angle due to the wedge shape of the transducer / reflector body. Incident longitudinal compressional waves emitted by the transducer array can therefore interact with this solid-fluid boundary at an oblique angle. This oblique angle may exceed the critical angle for mode conversion. Due to the acoustic impedance mismatch at the interface, a predictable portion of the longitudinal wave undergoes mode conversion, generating a resultant transverse shear wave.

[0114] The ultrasonic sensor 40 is arranged to generate ultrasonic waves directed at the fluid 16. A proportion of the ultrasonic wave may reflect off a boundary between the fluid 16 and a bounding surface (a wall of the chamber 12) and is detected at the emitting transducer. This arrangement is known as a pulse-echo arrangement. Alternatively, the reflected wave may be received at a different transducer arranged on the same side of the fluid as the emitting transducer. This is known as a pitch-catch arrangement. Finally, a portion of a wave transmitted through the fluid may be received by an ultrasonic transducer arranged on the opposing side of the fluid. This wave path is commonly referred to as through-transmission, orTT.

[0115] Figure 2c shows an example of an ultrasonic sensor comprising a plurality of ultrasonic transducers 52a, 52b, 54a, 54b are arranged in a linear array on a backing plate 50. In this example, the ultrasonic sensor comprises a pair of longitudinal wave transducers 52a, 52b and a pair of shear wave transducers 54a, 54b arranged linearly in a row on the backing plate.

[0116] In ultrasonic sensors comprising a plurality of shear ultrasonic transducers, the shear transducers may be arranged at different orientations to provide an ultrasonic sensor arranged to produce a plurality of shear wave polarisations. The shear transducers may be installed so that their polarisation is in the direction of any fluid flow, perpendicular to fluid flow, or any angle in between.Figure 2d shows an example of an ultrasonic sensor where a plurality of ultrasonic transducers are arranged in two rows on a backing plate 50. In this example, the ultrasonic sensor comprises six longitudinal wave transducers 52a-52f arranged linearly in a first row and six shear wave transducers 54a-54f arranged linearly in a second row on the backing plate 50. The first row and second row are parallel, forming a 2-dimensional array.

[0117] Figure 2e shows an example of an ultrasonic sensor where a plurality of ultrasonic transducers 52a-52c are arranged with multiple shear transducer orientations and multiple longitudinal transducers 54.

[0118] Other transducer arrangements on the backing plate are feasible. For example, the ultrasonic transducers may be arranged in pairs. The ultrasonic transducers may be arranged in a two-dimensional array. The ultrasonic transducers may be arranged as a linear array. Each ultrasonic transducer may have a width in the range of approximately 0.2mm to 20mm. Each ultrasonic transducer may have a length in the range of approximately 0.3mm to 40mm. Each ultrasonic transducer may have a generally rectangular, square, circular or oval shape. Each ultrasonic transducer may have a thickness in the range of approximately 0.02mm to 15mm.

[0119] Amplitude-based measurements using multimodal ultrasonic sensors include a comparative measurement of the gas / moisture, bubble and particulate content as well as a comparative measurement of solidification.

[0120] A single transducer can be used measure gas, moisture, bubble and particulate content; however the additional benefit of the multimodal transducer is the ability to compare the attenuation or time-of-flight of shear and longitudinal transducers in the multimodal assembly to yield additional information concerning the properties of the fluid. The variation of results between the different modes are dependent upon the composition of the propagating medium (the fluid). This information can also be used to self-verify measurements from each mode and also to regulate the effects of temperature and / or pressure. Through transmission multi-modal measurements are highly effective when applied to highly viscous fluids, dense multi-phase mixtures, high-pressure gases, or supercritical fluids that support shear wave propagation, as well as thermodynamic phase transitions such as solidification, crystalisation, or condensation. As with a single element transducer, the measurements could include particle size, particle mass, relative particle elasticity, particle count, and particle proportion (the ratio of particles to fluid).

[0121] A fluid's ability to support a bulk shear wave is strongly influenced by its continuous phase density, pressure, and complex viscosity. However, surface acoustic waves, platewaves, and shear horizontal waves generated by the transducer array may also interact with the boundary layer of low-viscosity or gaseous fluids to yield comparative phase data. There is therefore a significant step change in both the shear wave reflection and transmission coefficients when a fluid undergoes a phase transition such as when it solidifies, condenses, or deposits. The change in the equivalent longitudinal coefficients is less evident, and so comparison of the coefficients of both wave modes (shear and longitudinal) can give a more accurate indication of phase state transitions than either mode on their own.

[0122] Figures 3a-3c show exemplary arrangements of ultrasonic transducers which can form ultrasonic sensors. The sensor of Figure 3a is shown as a side-view and Figures 3b and 3c are shown end on so that the surface shown in the figures faces outwards, towards the material being measured.

[0123] The ultrasonic sensors of Figures 3a-3c each comprise a plurality of ultrasonic transducers 62 operating at different frequencies arranged on a backing plate 60. The transducers may be piezoelectric or EMAT in either longitudinal, shear, mode converted shear, plate or surface wave type. The transducers may also be arranged in a wedge, comb, direct-write transducer (DWT) or a capacitive or piezoelectric micromachined ultrasonic transducer (cMUT / pMUT) form factor. Each transducer may have a bandwidth of frequencies that it can generate and receive.

[0124] Having multiple transducers of different frequencies housed within a single ultrasonic sensor, referred to as an array or a multi-frequency array, can yield additional information about the fluid when compared with an ultrasonic sensor comprising a single frequency. The use of multiple frequencies may also allow self-verification of measurements taken. This transducer assembly may comprise multiple mode elements. To achieve wide frequency spectrum measurements, the ultrasonic sensor may comprise an array of longitudinal wave transducers 62 with different frequencies, and / or an array of shear wave transducers with different frequencies. The transducers 62 may be arranged on a backing plate 60. For example, the multi-frequency ultrasonic sensor may comprise an array of longitudinal wave transducers having frequencies of 0.001MHz, 0.5MHz, 2.5MHz, 5MHz, 8MHz, 10MHz, 15MHz, 20MHz, 50MHz, and 150MHz. For example, as shown in Figure 3a, an ultrasonic sensor may comprise a 0.1MHz, 1MHz, 3MHz, 8MHz, 20MHz, and 50MHz longitudinal element in an array mounted within a single sensor housing. A further view of the ultrasonic sensor is shown in Figure 3b. The ultrasonic sensor may be a pMUT style multi-frequency array transducer without a backing plate.The sensor may have a combination of multiple frequencies and multiple modes. An example of a sensor with a multi-frequency array of longitudinal wave transducers 72 and a multi-frequency array of shear wave transducers 74 is shown in Figure 3c. The transducers 72, 74 may be arranged on a backing plate 70.

[0125] The measurements from each transducer may be compared and / or combined to achieve a wide frequency-spectrum analysis measurement of the fluid properties. As various wave frequencies have been shown to interact with fluids differently, the different frequencies produce different attenuation profiles and acoustic velocities (referred to as phase velocities). Moreover, each frequency also has a different wavelength, and therefore the manner in which the various wavelengths interact with features depends upon the feature size relative to the wavelength. Multi-frequency measurements from a multi-frequency sensor can therefore yield additional measurements not possible with a single element transducer.

[0126] Examples of the amplitude and ToF measurements which can be achieved using a multifrequency transducer include the complex viscosity, shear rate dependant viscosity, molecular weight, and particle characterisation.

[0127] Specifically, different shear wave frequencies induce different shear rates on the fluid. Therefore, by measuring the viscosity with a range of frequencies a multi-frequency transducer assembly may measure the fluid behaviour across a range of shear rates, giving a comprehensive and accurate assessment of the state of the fluid and its complex viscosity or shear rate dependence within a processing machine.

[0128] This is particularly relevant for non-Newtonian fluids. This means that the viscosity of the fluid is shear rate dependent. As with a single element transducer the viscosity of fluid can either be calculated using an analytical relationship, an example being the Maxwell model for viscoelastic behaviour.

[0129] zf / 4(1 — sin 0

[0130] TJ = - I - -

[0131]

[0132] A \(1 + RsCCS 0 )

[0133] where r / is viscosity (in cm2 / s, known as Stokes), zi is the acoustic impedance of the material bounding the fluid, p\ is the density of the fluid, co is the angular frequency of the wave, Rs is the shear wave reflection coefficient, 0 is the wave phase, and T is the relaxation time. The density can be measured from a longitudinal ultrasonic sensor, and the relaxation time from the following relationship:

[0134] __ (1 - - 4(fissin fl)2

[0135]

[0136] 4C0fl_(l ~ >2) sin flIf Newtonian behaviour is assumed a simpler alternative model, the Greenwood model, may be used to determine the viscosity of the fluid as follows:

[0137]

[0138] Using an ultrasonic sensor, this viscosity, as well as the effective complex viscosity of multi-phase dispersions, can be measured for the fluid in situ and under process conditions. In multi-phase dispersions, the propagation of the ultrasonic wave is influenced by the effective mass and effective compressibility of the total mixture, allowing the determination of dispersed phase volume fractions. It is also possible to obtain viscosity or phase-fraction data by conducting a calibration ramp where fluids of known viscosity or known gas-liquid ratios are used to create a reference curve relating reflection and attenuation coefficients to the desired fluid property. Using this approach, it is not necessary to know the fluid density or relaxation time.

[0139] Another pair of rheological parameters that can be measured ultrasonically are a fluid storage modulus (M') and loss modulus (M") as follows:

[0140]

[0141] Where c is the longitudinal ultrasonic velocity in the fluid and a is the attenuation coefficient. Longitudinal waves can therefore be used for monitoring the fluid storage modulus and loss modulus.

[0142] Figure 4 shows an exemplary arrangement of an ultrasonic sensor comprising a plurality of ultrasonic transducers 82a, 82b, 84a, 84b each arranged on an acoustically tuned backing plate 86. Alternatively, the transducers may be arranged on a shared acoustically tuned backing layer 86.

[0143] The ultrasonic sensor may comprise a backing plate on which the transducers may be mounted. The backing plate may be acoustically tuned and / or the individual transducers may have individual acoustically tuned backing plates / layers 86 which are then arranged on a backing plate 80. The acoustically tuned components may provide a means of controlled damping. The controlled acoustic impedance enhances the damping of theultrasonic sensor to provide a controlled damping effect. The ultrasonic sensor is thereby considered to be "acoustically tuned" by the damping.

[0144] The damping may be provided by incorporating a damping layer intermediate (between) the transducer elements and the backing plate. In an alternative arrangement, a damping layer may be embedded in a backing plate adjacent the transducers. Damping may additionally or alternatively be achieved by manufacturing the backing plate with tuned acoustic impedance materials. Greater damping increases the bandwidth of the transducers and results in a higher sensitivity across a wider range of frequencies. Sensor backing also dissipates wave propagation from the rear of a transducer, so that this does not interfere with the response from the wave emanating from the front of the transducer. To achieve a desired damping effect and allow the rear facing wave to dissipate via the backing plate, the backing of the ultrasonic sensor (damping layer and / or backing plate / layer) may be configured to have an acoustic impedance similar to that of the transducer. For example, the backing plate may be manufactured from a suspension of a metal powder in an organic base, where the metal suspension acts to increase the acoustic impedance of the mix and help scatter the rear facing wave. The organic base may comprise a bonding or setting material such as an epoxy resin. The organic base may therefore aid the absorption of the ultrasonic and bonding of the backing to the transducers.

[0145] The target acoustic impedance of the damping layer / backing plate depends on the specific transducer element material used, and the front face material.

[0146] In addition to acoustically tuning the backing plate or backing plate damping layer material properties, the thickness of the layer may be adjusted. The layer can then act to constructively or destructively interfere internal reflections to improve the performance of the transducer.

[0147] The following (Table 1) is a summarised list of some of the potential material properties that can be characterised using the ultrasonic sensors described in relation to Figures 2-4:

[0148] Probe Type Algorithm Wave Mode Measurement

[0149] Section 1 - Single Transducer

[0150] Single Amplitude - R* Shear or Acoustic Impedance Transducer Longitudinal

[0151]

[0152] Single Amplitude - R* Longitudinal Density

[0153] Transducer

[0154] and

[0155] ToF

[0156] Single Amplitude - TT** Shear or Attenuation

[0157] Transducer Longitudinal

[0158] Single Amplitude - TT** Shear or Gas / Moisture, Bubble and Particulate Transducer Longitudinal Content

[0159] Single Amplitude - R* Shear Viscosity and Inferred Molecular Transducer Weight

[0160] and

[0161] Optionally Phase

[0162] Single Amplitude - TT** Shear or Solidification

[0163] Transducer Longitudinal

[0164] Or

[0165] Amplitude - R*

[0166] Single ToF Shear or Acoustic Velocity

[0167] Transducer Longitudinal

[0168] Single ToF Longitudinal Bulk Modulus / Compressibility Transducer

[0169] Single ToF Shear Shear Modulus (due to Solidification Element Under Pressurisation or During Thickening)

[0170] Single ToF Long. Young's Modulus (due to Solidification Element Under Pressurisation or During

[0171] Thickening)

[0172]

[0173] Single ToF Shear Fluid Particle Orientation - Relative Transducer

[0174] Single ToF Longitudinal Flow Rate

[0175] Transducer

[0176] Single Phase Shear or Solidification

[0177] Transducer Longitudinal

[0178] Section 2 - Multi-Modal Sensor

[0179] Multi-Modal Amplitude - TT** Shear and Gas / Moisture, Bubble and Particulate Longitudinal Content - Comparative

[0180] Multi-Modal Amplitude - TT** Shear and Solidification - Comparative Longitudinal

[0181] Multi-Modal ToF Shear and Bulk Modulus / Compressibility Longitudinal

[0182] Multi-Modal ToF Shear and Poisson's Ratio (due to Solidification Long. Under Pressurisation or During Thickening)

[0183] Multi-Modal ToF Shear and 1st Lame parameter (due to Long. Solidification Under Pressurisation or During Thickening)

[0184] Multi-Modal ToF Multiple Fluid Particle Orientation - Absolute Shear

[0185] Polarisations

[0186]

[0187] Multi-Modal Phase Shear and Solidification - Comparative Longitudinal

[0188] Section 3 - Multi-Frequency Sensor

[0189] MultiAmplitude - R* Multiple Shear Rate Dependant Viscosity Frequency Shear

[0190] and

[0191] Frequency

[0192] Optionally Phase

[0193] MultiAmplitude - R* Multiple Molecular Weight and Particle Frequency Longitudinal Characterisation

[0194] and

[0195] Frequency

[0196] ToF

[0197]

[0198] * "Amplitude - R" refers to amplitude measurements taken from waves reflected from the fluid interface

[0199] ** "Amplitude - TT" refers to amplitude measurements taken from waves which have travelled through the fluid being measured

[0200] Section 2 of Table 1 lists measurements which may be taken using a multi-modal sensor (i.e. the use of longitudinal waves, shear waves, and / or multiple shear wave polarisations). Exemplary parameters which may be monitored using measurements from a multi-modal sensor include Pressure, Temperature, Viscoelastic Moduli, Specific Volume, Inferred Molecular Weight, Freezing Point Margin, Composition & Fluid Mix Ratios, Volatile Organic Compounds, Slurry & Agglomeration Characterisation, Moisture & Volatiles, Fatty Acid Methyl Esters (FAME), Yield Stress, Rheopexy (Anti-thixotropy), Total Base / Acid Number (TBN / TAN), Total Dissolved Solids, API Gravity, Molar Refraction, Peroxide Value, Osmolarity, Lymph and Blood Specific Properties, Chemical Oxygen Demand, Total Organic Carbon, Specific Heat Capacity, Mass Diffusivity, Fluid Shear Stress, Dielectric Strength, Electrolyte Balance & Brine Concentration, Drying Time, Levelling, & Sagging, Internal Energy, Saturation Index, Cetane Number & Index Brix.

[0201] Section 3 of Table 1 lists measurements which may be taken using a multi-frequency sensor. Exemplary parameters which may be monitored using measurements from a multi-frequency longitudinal sensor include Acoustic Velocity, Acoustic Impedance, Bubble Sizing & Concentration, Reflection Coefficient, Wear Debris Size & Concentration,Soot Content & Volume Fraction, Two-Phase Flow & Void Fraction, Insoluble Impurities, Compressibility Factor, Surface Tension, Fluid Solubility, Dielectric Constant (Relative Permittivity), Specific Weight, Foaming Capacity and Foamability, Liquid-Vapour Interaction Characterisation, Dew Point, Boiling Site Density, Parachor, Electrical Conductivity, Biochemical Oxygen Demand, Cloud Point, Enthalpy, Entropy, Absorbance & Transmittance, Soret Coefficient, Particle Count & Mass, Octane Number, Calorific Value and Water Activity.

[0202] Exemplary parameters which may be monitored using measurements from a multifrequency longitudinal sensor with elements arranged in multiple planes include Particle Sizing & Airborne Distribution, Bacterial Count & Microbial Colony Formation, Identification & characterisation of Individual Solid Elements suspended in a fluid and Water Content.

[0203] Exemplary parameters which may be monitored using measurements from a multifrequency shear sensor include Dynamic Viscosity, Kinematic Viscosity, Thixotropy, Free Fatty Acids, Contact Angle, Biostability, Rheochor, Pour Point and Unsaponifiable Residue.

[0204] The ultrasonic sensors described in relation to Figures 2 to 4 can be used in the fluid sensing apparatus shown in Figures la and lb as well as the fluid sensing apparatus shown in Figures 5a-5d, 6a-6b, 7, 8, and 9.

[0205] Figure 5a shows a fluid sensing apparatus 90 according to an embodiment. The fluid sensing apparatus 90 comprises an ultrasonic sensor 100 and control system 14. The ultrasonic sensor 100 comprises a plurality of ultrasonic transducer elements 102, 104 arranged to emit ultrasonic waves with a plurality of polarisations and receive ultrasonic waves with a plurality of polarisations and may be substantially similar to the transducer elements 22, 24. The fluid sensing apparatus 90 may be used to monitor a fluid 16 contained by a chamber 12. The control system 14 may comprise the same features as that described in relation to Figure la.

[0206] The fluid sensing apparatus 90 may comprise a reflector body 106. The reflector body 106 may be arranged such that the ultrasonic waves emitted by the transducer elements 102, 104 are transmitted through the reflector body. The reflector body 106 defines a boundary, and at least a portion of the ultrasonic waves emitted by the transducer elements are reflected at the boundary. In use, the boundary of the reflector body 106 will define a boundary between the reflector body 106 and the fluid 16 that is to be tested. Put another way, the ultrasonic waves are transmitted through the reflector body 106 and at least a portion of the ultrasonic waves emitted by the transducer elementsis reflected at a boundary between the reflector body 106 and the fluid back towards the transducers 102, 104.

[0207] The reflector body 106 may be mounted to a backing surface or backing plate 108. The backing plate 108 supports the ultrasonic transducers 102, 104. The reflector body 106 may be dimensioned to extend beyond the ultrasonic transducer elements 102, 104 mounted to the backing plate 108. The ultrasonic transducer elements 102, 104 may be embedded within the reflector body 106 or arranged in a layer between the backing plate 108 and reflector body 106. The reflector body 106 may be acoustically tuned so that the measurement sensitivity with the fluid 16 can be maximised. This can be done by increasing the acoustic similarity between the reflector body 106 and the fluid 16. At least a part of the reflector body 106 may be arranged between the ultrasonic transducers 102, 104 and the fluid 16 to be tested so that the ultrasonic waves travel through the reflector body before interacting with the fluid. The reflector body 106 provides a boundary with the fluid 16 to be monitored so that a reflection of the ultrasonic waves can be achieved without the need for the ultrasonic waves to travel through the fluid and reflect from a boundary which confines the fluid, such as the chamber 12 wall.

[0208] Preferably, the reflector body 106 is a material suitable to allow partial transmission of wave into the fluid, as this ensures changes in the fluid properties are clearly detectable, whilst also reflecting enough of the wave from the fluid to ensure a reliable reading can be made. This can be achieved by selecting a reflector body material to have a suitable acoustic impedance compared to the target fluid. Acoustic impedance is measured in Rayls where 1 Rayl is equal to 1 kg / (s-m2) and is often of the order of 106and so is defined in terms of Mega-Rayls (lxlO6Rayls).

[0209] In one example, when measuring properties of lubricating oil with an acoustic impedance of 1.5 MRayls, an aluminium reflector body may be used which has an acoustic impedance of 17 MRayls. This combination results in a reflection coefficient magnitude of 0.84 which ensures adequate signal is both transmitted into the fluid as well as being reflected.

[0210] Gases typically have much lower acoustic impedances than liquids and so often require a reflector body material with a correspondingly lower acoustic impedance. For example, monitoring gases may require the use of a reflector body formed from polymethyl methacrylate (PMMA) which has an acoustic impedance of approximately 3.2 MRayls. The reflector body may have an acoustic impedance with a gradient so that the acoustic impedance changes gradually across the body. This can ensure that as the wave propagates through the reflector body, it transitions between different acousticimpedances with no distinct interface between them. The ultrasonic sensor may have multiple reflector bodies layered to achieve this matching effect in multiple stages, with each reflector body having a different acoustic impedance. This approach can also be used to gain reference reflections from each reflector body interface. This can then be used for calibration of the ultrasonic sensor.

[0211] Reflection coefficient values between 0.98 and 0.02 are typically targeted to balance both the measurement sensitivity and reflected signal strength. If contacting the fluid, it is preferable for the reflector body material to be chemically compatible with said fluid. Common examples of reflector body materials include metals (steel, aluminium, titanium, brass etc), ceramics (alumina, sapphire, quartz etc), engineering polymers (PMMA, PEEK (Polyether ether ketone), PI (Polyimide), PFA (Perfluoroalkoxy alkane), PVDF (Polyvinylidene Fluoride), PTFE (Polytetrafluoroethylene), ETFE (Ethylene Tetrafluoroethylene), PCTFE (Polychlorotrifluoroethylene), FEP (Fluorinated Ethylene Propylene) etc) and epoxy resins.

[0212] The reflector body is often of a sufficient length to ensure reflected signals can easily be distinguished in the time domain, either from each other, or from the initial transmitted signal. The reflector thickness can be controlled to account for the wavelength of the signal being transmitted. The reflector body size will often therefore depend on the body material and its acoustic velocity, as well as the wave frequency and duration. The reflector body may range from one millimetre to a metre.

[0213] A similar acoustic matching may be carried out for the transducer acoustically tuned layer. However, in this case the layer is preferably matched to the transducer material. In the example of piezoelectric transducers this may involving matching to materials such as Lead Zirconate Titanate (PZT) which has an acoustic impedance of approximately 35MRayls, Barium Titanate which has an acoustic impedance of approximately 20MRayls, Quartz which has an acoustic impedance of approximately 15MRayls, and / or Polyvinylidene Fluoride (PVDF) which has an acoustic impedance of approximately 4-5 MRayls.

[0214] In operation, a first proportion of the received ultrasonic waves may be reflected from a boundary between the reflector body and a fluid being monitored. The reflected ultrasonic waves may be detected by the transducer elements 102, 104 of the ultrasonic sensor 100 which emitted the ultrasonic waves. This is a pulse-echo configuration. As discussed above, the reflection from this boundary will provide data regarding the mediums on each side of the boundary. Therefore, at least one property of the fluid may be determined from this data. The reflected ultrasonic waves may also be detected by other emitting ultrasonic transducers 102, 104. This is a pitch-catch configuration. Ineither configuration, this provides reflection at a fixed point and / or a fixed window in the time-domain response. Ultrasonic waves not reflected from the boundary between the reflector body 108 and fluid 16 may be transmitted across the boundary and through the fluid 16. Additional ultrasonic sensors may be arranged on a far side of the fluid 16 to detect the transmitted ultrasonic waves. This is a pitch-catch configuration.

[0215] Figure 5b shows a fluid sensing apparatus 110 according to an embodiment. The fluid sensing apparatus 110 comprises an ultrasonic sensor 120 and control system 14. The ultrasonic sensor 120 comprises a plurality of ultrasonic transducer elements 122 arranged to emit ultrasonic waves with a plurality of frequencies and receive ultrasonic waves with a plurality of frequencies and may be substantially similar to the transducer elements 42. The fluid sensing apparatus 110 may be used to monitor a fluid 16 contained by a chamber 12. The fluid sensing apparatus 110 may comprise a reflector body 126. The control system 14 and reflector body 126 may be substantially similar to the equivalent features described in relation to Figure 5a.

[0216] Figures 5c and 5d show a fluid sensing apparatus 130 according to an embodiment. The fluid sensing apparatus 130 comprises an ultrasonic sensor 130 and control system 14. The ultrasonic sensor 130 comprises a plurality of ultrasonic transducer elements 142, 144 arranged to emit ultrasonic waves. The ultrasonic transducer elements 142 are arranged to emit ultrasonic waves with a plurality of frequencies and receive ultrasonic waves with a plurality of frequencies and may be substantially similar to the transducer elements 22. Each transducer element may be arranged to emit ultrasonic waves having one peak frequency so that the plurality of transducers emits a plurality of frequencies. The ultrasonic transducer elements 144 are arranged to emit ultrasonic waves with a plurality of polarisations and receive ultrasonic waves with a plurality of polarisations and may be substantially similar to the transducer elements 24. Each transducer element may be arranged to emit ultrasonic waves having one polarisation so that the plurality of transducers emits a plurality of polarisations.

[0217] The fluid sensing apparatus 130 may be used to monitor a fluid 16 confined by a chamber 12. The control system 14 may comprise the same features as that described in relation to Figures 5a and 5b. The fluid sensing apparatus 130 comprises a reflector body 146 which is substantially similar to the reflector body 108 shown in Figures 5a and 5b. Therefore, the fluid sensing apparatus 130 may operate in a pulse-echo and / or pitch-catch configuration. The pitch-catch configuration which utilises ultrasonic waves reflected from the boundary between the reflector body 146 and the fluid 16 to be monitored is demonstrated in Figure 5d by way of the arrows representing the wave paths associated with the ultrasonic transducers arranged to emit and receive a plurality of frequencies of ultrasonic waves.Therefore, the apparatus 130 shown in Figures 5c and 5d can be considered to be a combination of the fluid sensing apparatus 90 and the fluid sensing apparatus 110. Figures 6a and 6b show exemplary arrangements of a reference feature 152, 162 which can be used to calibrate the ultrasonic sensor 150, 160. The reference feature 152, 162 may be combined with any other embodiment described.

[0218] Figure 6a shows part of a fluid sensing apparatus according to any embodiment described with a plurality of ultrasonic transducers 102, 104 forming an ultrasonic sensor 150. The reference material 152, 162 may have has acoustic properties which are substantially different to the reflector body 106 so that the ultrasonic waves emitted from the ultrasonic transducers are at least partially reflected at a boundary between the reflector body and the reference feature 152, 162.

[0219] A calibration is performed by taking measurements using the ultrasonic sensor in a "known state" where the proportion of wave reflected from the measurement interface is known. Typically, a reference fluid of known properties is used and reference measurements are taken across the full range of operating conditions to provide reference values from which a reflection coefficient can be calculated. However, this is an expensive and time-consuming method.

[0220] The ultrasonic sensor 150 comprises the reference feature 152 embedded within the reflector body 106. The reference feature 152 may be formed of any material or may be an air gap. In this embodiment, the reference feature 152 may be sized and located such that a first proportion of the emitted ultrasonic waves do not interact with the boundary between the reflector body 106 and the reference feature 152 and are instead transmitted through the reflector body 106. These transmitted waves may then reflect from the boundary between the reflector body 106 and the fluid to be monitored. A second proportion of the emitted ultrasonic waves may reflect from the reflector body 106 and reference feature 152 boundary. The reference feature 152 may be arranged between the ultrasonic transducers 102, 104 and the fluid to be monitored meaning that a first signal relating to the reference feature 152 will be detected and a second signal relating to the fluid will be detected. Therefore, by considering the time-domain windows for each measurement, a calibration may be taken during a reference time-domain window and a sample measurement may be taken during a sample testing time-domain window.

[0221] The ultrasonic sensor 160 of Figure 6b shows an embodiment in which the reference feature 162 abuts the reflector body 106. In this embodiment, the emitted ultrasonic waves will be transmitted through the reflector body 106 and interact with the boundary between the reflector body 106 and reference feature 162. The reference feature 162 isarranged such that a (second) proportion of the ultrasonic waves are reflected at the boundary between the reflector body 106 and reference feature 162. The remaining (first) proportion of non-reflected ultrasonic waves are transmitted across this boundary and through the reflector body 162. The first proportion of emitted ultrasonic waves are reflected at the boundary between the reference feature 162 and the fluid to be monitored to provide at least one property of the fluid. The properties of the reference feature 162 may be substantially similar to those of the reference feature 152 described in relation to Figure 6a. Therefore, the reference feature 162 may be an air gap or a material with known properties.

[0222] An air gap is particularly advantageous because due to the acoustic dissimilarity between fluid and air, it can be assumed that 100% of the ultrasonic wave will be reflected at the boundary between the reflector body and an air gap.

[0223] Alternatively, the reflector body 106 may form the reference feature 152 itself in which case the reference material 152 is the reflector body 106.

[0224] The reference feature is preferably acoustically tuned to provide a reliable reflection whilst also giving a consistent and / or predictable response across the range of operating conditions of the sensor.

[0225] In the embodiments described, the ultrasonic sensors may be configured in a housing that can be inserted into a fluid chamber or other component of a processing system, such as a tee manifold. The housing may comprise a threaded feature to secure the sensor in place. Exemplary components of a processing system include one or more of a pipe, tank, vessel, feed, filter, container, channel, chamber, clarifier, pump suction and discharge zones, basin, inlet, zone, digester, discharge, centrifuge, conduit, line, tube, duct, reservoir, valve, outlet, manifold, header, drain, exhaust, return, vent, bypass, port, fitting, passageway, separator, reactor, heat exchanger, mixer, column, tower, condenser, boiler, evaporator, scrubber, extractor, sump, vat, pond, lagoon, well, trench, trough, catchment, hose, main, sewer, flume, chute, aqueduct, culvert, penstock, spool, compressor, turbine, accumulator, receiver, trap, strainer, injector, nozzle, extruder, lubricator, radiator, coolers, environment, plenum, space, cavity, atmosphere, stream, bleed, purge, overflow, coupling, joint, flange, annulus, jacket, silo, hopper, drum, barrel, receptacle, bin, canal, river, lake, estuary, bore, borehole, shaft, gallery, void, enclosure, casing, housing, pathway, guideway, intersection, network, grid, matrix, circuit, loop, pool, flowline, gutter or within any processing element, or the influent, or effluent of said processing element.

[0226] Figure 7 shows a cross section of a fluid sensing apparatus 170 arranged on an outer surface of the fluid chamber 12. The fluid sensing apparatus 170 may be a fluid sensingapparatus according any embodiment disclosed. Figure 7 shows an ultrasonic sensor 180 comprising a plurality of ultrasonic transducer elements arranged to emit and receive a plurality of ultrasonic waves having a plurality of polarisations and frequencies, arranged on a backing plate with dampening layers.

[0227] The transducers may be permanently installed onto the outer surface of the fluid chamber or may be non-permanently installed using a clamping system or other attachment system. In such embodiments, the ultrasonic transducers may be arranged to transmit the ultrasonic waves through a wall of the chamber 12.

[0228] Figure 8 shows a cross section of a fluid sensing apparatus 190 arranged partially within the wall 12a of a fluid chamber 12. The fluid sensing apparatus 190 may be a fluid sensing apparatus according any embodiment disclosed. The ultrasonic sensor 200 is embedded within the wall 12a of the chamber 12. This arrangement is advantageous for long term monitoring of a fluid or process. The fluid 16 may be moving through the chamber as part of a fluid processing step, as demonstrated by the single headed arrows.

[0229] Figure 9 shows cross section of a fluid sensing apparatus 210 arranged on a probe 212 which can be inserted into a fluid chamber 12. The fluid sensing apparatus 210 may be a fluid sensing apparatus according any embodiment disclosed. The ultrasonic sensor 220 may be arranged along the length of an elongated probe 212. In the example shown in Figure 9, a plurality of ultrasonic transducers 216 are arranged on a backing plate along the length of the probe. The fluid sensing apparatus 210 may comprise a handle 214 which may house components of the apparatus such as wiring 26 between the transducers 216 and control system 14.

[0230] Figure 11a shows a cross section of a fluid sensing apparatus 240 arranged partially within a fluid chamber 12. The fluid sensing apparatus 240 may be a fluid sensing apparatus according any embodiment disclosed. Figure 11a shows an ultrasonic sensor 250 comprising a plurality of ultrasonic transducer elements arranged to emit and / or receive a plurality of ultrasonic waves which may have a plurality of polarisations and frequencies. Figure 11a further shows an ultrasonic sensor 252 comprising a plurality of ultrasonic transducer elements arranged to emit and / or receive a plurality of ultrasonic waves which may have a plurality of polarisations and frequencies. The first transducer array 250 and second transducer array may be separated by a fixed gap 254. Therefore, the plurality of ultrasonic transducer elements may be arranged in a bifurcated configuration. The fixed gap 254 may be configured to receive the fluid to be monitored 16, facilitating operation of the ultrasonic sensor in both pulse-echo and pitch-catch arrangement. In this configuration, ultrasonic waves emitted by a first transducer 250are transmitted through the fluid 16 within the fixed gap 254 and are received by the second transducer 252. The fixed gap 254 defined by this bifurcated configuration may be sized to correspond to the plurality of frequencies emitted by the ultrasonic transducer elements, thereby supporting frequency-based analysis approaches. For example, by monitoring variations in the resonant interference features established within the fixed gap, a frequency-based methodology can be utilised to extract the acoustic velocity of the fluid.

[0231] Figure lib shows a cross section of a fluid sensing apparatus 260 substantially similar to that of Figure 11a. However, instead of a fixed gap, the fluid sensing apparatus 260 may comprise a gap between the first transducer array 250 and second transducer array 252 which varies in size along the length of the transducer array. The variation in gap may be due to a reflector body 256 arranged in front of each transducer array 250, 252 within the bifurcated configuration. The reflector body / bodies 256 may be arranged such that the ultrasonic waves emitted by the respective transducer elements are transmitted through the reflector bodies. Each reflector body 256 defines a boundary with the fluid to be monitored 16. Therefore, a proportion of the emitted ultrasonic waves may be reflected at the boundary between the reflector body 256 and the fluid 16 back towards the emitting transducers, facilitating boundary reflection measurements. This arrangement allows the apparatus 260 to capture both through-transmission data across a gap and boundary reflection data simultaneously or sequentially.

[0232] The first transducer array 250 and the second transducer array 252 in the bifurcated configuration of Figure 11a and / or Figure lib may each comprise an array of longitudinal wave transducers, an array of shear wave transducers, or a combination of both longitudinal and shear wave transducers. The specific combination of wave modes and / or polarizations can be selected based on the at least one property of the fluid to be calculated.

[0233] Figure 12a shows a cross section of a fluid sensing apparatus 270 arranged within a fluid chamber 12. The fluid sensing apparatus 270 may be a fluid sensing apparatus according to any embodiment disclosed. Figure 12a shows an ultrasonic sensor 280 comprising a plurality of ultrasonic transducer elements arranged to emit and / or receive a plurality of ultrasonic waves which may have a plurality of polarisations and frequencies. The ultrasonic sensor 280 may be arranged in an instrumented foil configuration. In such configuration, a dedicated manifold 282 may be configured to support a plurality of instrumented foils, wherein each instrumented foil contains a plurality of ultrasonic transducer elements. The instrumented foils are positioned such that a fixed gap 284 is defined between adjacent foils. This fixed gap is configured to receive the fluid to be monitored. Within this arrangement, the ultrasonic transducersdeposited on the instrumented foils can operate in a pitch-catch arrangement, wherein ultrasonic waves emitted by a first transducer on a first foil are transmitted through the fluid 16 within the fixed gap 284 and received by a second transducer on an adjacent, opposing second foil. Furthermore, the transducers may operate in a pulse-echo arrangement, wherein a single transducer emits an ultrasonic wave and subsequently detects the wave reflected from a foil or an opposing structure.

[0234] Figure 12b shows a cross section of a fluid sensing apparatus 290 substantially similar to that of Figure 12a. However, the fluid sensing apparatus 290 may further comprise a reflector body 302 arranged in front of each transducer array on the instrumented foils. The reflector body 302 may be arranged such that the ultrasonic waves emitted by the transducer elements are transmitted through said reflector body 302. The reflector body 302 may define a boundary between the reflector body 302 and the fluid to be tested 16 within the fixed gap 284. Accordingly, at least a portion of the ultrasonic waves emitted by the transducer elements may be reflected at the boundary between the reflector body 302 and the fluid 16 back towards the transducers. This facilitates precise boundary reflection measurements, allowing the system to capture both boundary reflection data and through-transmission data concurrently or sequentially.

[0235] The transducer arrays housed within the instrumented foils shown in Figure 12a and / or Figure 12b may comprise longitudinal wave transducers, shear wave transducers, or a combination of both longitudinal and shear wave transducers. Additionally, the ultrasonic transducer elements within the instrumented foils may be specifically configured to operate in either a radial mode, thickness mode, flexural mode, or surface wave mode where the waves propagate along the foil surface.

[0236] Figure 10 shows a method 230 of determining at least one property of a fluid using a fluid sensing apparatus comprising an ultrasonic sensor, a backing plate, and a control system. The fluid sensing apparatus may be that of any embodiment described.

[0237] At a first step, the method comprises emitting ultrasonic waves 232 having a plurality of polarisations from a plurality of ultrasound transducer elements.

[0238] The method comprises receiving ultrasonic waves 234 having a plurality of polarisations, wherein the received ultrasonic waves reflected from a boundary between the ultrasonic sensor and fluid.

[0239] The method comprises generating a sensor output signal 236 based on the received ultrasonic waves.

[0240] The method comprises transmitting the sensor output signal 238 to a control system, wherein the control system is configured to calculate at least one property of the fluid,wherein the at least one property is calculated based on the received sensor output signal during a sample testing time-domain window.

[0241] The method may comprise generating a control signal based on the at least one property calculated and transmitting the control signal to a component of a fluid processing system, wherein the component may be a display, a memory device, a further control system, a heating element, a mechanical stirrer, a dosing system, an actuator, a valve, a pump, a diverter and / or a pressure regulator. Other components may be envisaged. For example, a fluid undergoing transformation in a production process may be monitored in order to change the processing via an automated closed loop feedback system or though manual intervention. Such monitoring can ensure that the processing remains within safe limits or within preset conditions required for the production of a final product. For example, for quality assessment processes. The at least one calculated property may be indicative of wider system behaviours which can then be used as feedback via the control signal for quality assessment or process intervention.

[0242] The method may be applied to various industrial applications, including monitoring oil properties in combustion engines. As combustion engine vehicles are used in service, the lubricating oil can degrade and become contaminated through various mechanisms. The extent of this degradation is a function of the vehicle use duty cycle which can vary significantly between different geographical regions and between different driving styles. For example, the same model of truck that performs frequent heavily laden short journeys in very hilly terrain will see higher rates of lubricant degradation per km travelled than the same truck with a light load performing infrequent long journeys on flat motorways.

[0243] Lubricant changes are traditionally performed after a certain distance travelled, which can lead to either wasted lubricant, which is still performing well, or it can result in excessive engine wear due to operating with degraded lubricants that have been run beyond their design life. Furthermore, variations in fuel types, such as more environmentally friendly combustion fuels, result in different lubricant degradation mechanisms, introducing more uncertainties about the optimum servicing strategy of their vehicles in service.

[0244] For Haulage vehicle fleets, lubricant maintenance is a significant operational cost. By performing in-line lubricant condition monitoring, it is possible to track the remaining life of the lubricant in service to plan strategic pre-emptive services only when they are needed, eliminating unnecessary waste oil, optimising service intervals, reducing downtime, saving customers cost, and minimising engine wear. By tracking the oil degradation data across multiple vehicles in service, it is possible to develop advancedalgorithmic models of lubricant degradation rates as a function of the operating duty cycle, allowing the accurate prediction of lubricant remaining life considering operating variables such as vehicle speed, torque, temperature, humidity, base oil type, formulation type etc. Deployment of such a lubricant-life model would reduce the need for every unit in service to be equipped with oil condition monitoring capabilities but would achieve the same result of advanced engine tribological management.

[0245] Existing in-oil condition-monitoring product solutions are predominantly based on electrical conductivity and impedance measurements, which can indicate a change in lubricant condition but can lead to issues when multiple degradation mechanisms are occurring simultaneously. For example, increasing diesel contamination could result in the traditional sensor outputting a drop in the oil quality signal, whilst water contamination could result in a false reading of increased oil quality. For this reason, that such systems are not suitable for reliable field measurements. In-line optical systems have been successfully demonstrated in laboratory environments but have had limited success in the field due to their fragile nature, and issues with varnishing and other contaminants building up on the optical window adversely affecting any long-term monitoring.

[0246] In-line oil laboratory sampling can provide advanced measurements of oil degradation characterisation, however obtaining frequent oil samples for in-service vehicles is a costly and labour-intensive process, and only provides information about that specific vehicle type, oil type, and operating duty cycle. As such any lubricant-life models would be based on unrepresentative data sets with not many data points.

[0247] Active ultrasonics for lubricant condition monitoring therefore provides a low cost, high sensitivity, and robust measurement method as in-line ultrasonic sensors may be installed in the oil lines in the vehicle. By providing real-time measurements such as lubricant viscosity, density, and compressibility, lubricant degradation can be estimated in real-time. This information allows the owner / operator to schedule the precise time when an oil change is needed.

[0248] Lubricant condition monitoring is one example of an application of a fluid sensing apparatus and method. Further applications include the measurement and / or monitoring of food and beverage processing, water / wastewater / sewerage / sanitation / salinisation, chemical production / processing, advanced materials processing, personal care product / cosmetics processing, fast moving consumer goods processing, metal processing, mineral / mining extraction / processing, mineral / material recovery, phytomining, agricultural and irrigation, agronomy, agroindustry, hydroponics, aquaponics, algaculture, mariculture, plant cell culture, protein crop cultivation,mycoprotein production, plastics / polymer / biopolymer / recycled polymer processing, oil and gas / petrochemical processing, HVAC / refrigeration, energy, biogas, pyrolysis, nuclear, liquification, hydrogen / green hydrogen, fuel-cells, heat pumps, bioreactors / photobioreactors / digesters / fermenters / algae processing, compressors, turbines, paper and pulp processing, semiconductor production, textiles processing, dying, painting / coating, fuel / biofuel / biogas processing / monitoring, power generation, transport including aerospace, marine, automotive, heavy haul, city transit, off-highway vehicles, biotechnology / bioprocessing / biochemical / biomedical applications including health monitoring, pharmaceutical processing, space exploration, construction and civil engineering applications such as geopolymers / concrete pouring / curing.

[0249] The following description provides further exemplary arrangements in which an ultrasonic sensor as described above may be used in a system. While the following exemplary industrial applications may be described with reference to specific sensor configurations (such as a bifurcated, probe, foil, or embedded wall arrangement), it will be appreciated by those skilled in the art that any of the ultrasonic sensor configurations, modes, arrangements, and internal sub-components, including but not limited to reflector bodies, reference features, acoustically tuned reflector layers, and matching sensitivity layers described herein may be interchangeably deployed across any of the described fluid processing systems and applications.

[0250] Wide-Spectrum Ultrasonic Array for Supporting Mineral Recovery

[0251] A fluid sensing apparatus may be deployed for continuous, deterministic closed-loop monitoring of mineral recovery processes. The recovery system is specifically configured for the extraction of target elements including Li, Co, Ni, Mn, Pt, Pd, Rh, Ru, Au, Ag, Cu, Sn, In, Ga, Ge, Ta, W, Nd, Pr, Dy, Tb, Sm, and La from element-bearing substrate such as PCBs, solar panels, magnets, hard disk drives, spent batteries, fly ash, bottom ash, electroplating sludge, red mud, catalytic converters, EAF dust, waste incineration bottom ash, mine tailings, ores, biomass, residues, and wastewater effluent. The minerals could be contained in fluids such as sulfuric, hydrochloric, nitric, phosphoric, citric, and oxalic acids, hydrogen peroxide, organic extractants such as a tertiary-branched-chain carboxylic acid, specifically a neodecanoic acid, Bis(2,4,4-trimethylpentyl)phosphinic acid, D2EHPA, kerosene, and phosphonium ionic liquids, aqueous solutions, bacterial bio-oxidation broths, EDTA / chelating solutions, enzymatic or biosorbent cell-free extracts, deep eutectic solvents (DES), halogen-based fluids, or hydroxyoximes.

[0252] In some configurations, the fluid sensing apparatus comprises an instrumented manifold defining at least one fixed gap, or a plurality of gaps having different fixed widths. Thegap width may be configured to generate acoustic resonances within the at least one gap based on an operating transducer frequency and one or more properties of a target fluid. The instrumented manifold is configured for fluidic communication with channels having a cross-sectional dimension in a range from about 10 pm to about 10 mm. In further configurations, the apparatus may comprise a plurality of internal instrumented foils, for example the instrumented foils as described in relation to Figures 12a and 12b. The instrumented foils may be each supported within a single manifold, or optionally within a plurality of manifolds. The instrumented foils may define a fixed gap between adjacent foils which can receive the fluid and therefore signals may be transmitted directly through the centre of the medium / fluid. This arrangement is suited for scalability as the external manifold can change in size, but the internal foil distribution can remain constant. Therefore, the system can be configured for integration into pipes with diameters from 500 pm to heavy industrial pipe manifolds having internal diameters up to about 1500 mm. The reflector body material may be selected based on the target fluid and both its acoustic properties and chemical compatibility. For example, when deployed in aggressive fluid environments such as strong acids, the reflector body may comprise chemically inert fluoropolymers, such as PTFE, PVDF, or PFA, or inert ceramics, such as alumina or quartz. The desired acoustic properties of the reflector body may be similar to those described in relation to the fluid sensing apparatus comprising a reflector body.

[0253] The sensing array may comprise multi-modal (longitudinal and shear) and multifrequency piezoelectric transducer elements sweeping a frequency bandwidth of 0.001 MHz to 50 MHz. A central processing system may execute simultaneous pitch-catch and pulse-echo measurements within specific sample testing time-domain windows to calculate an array of fluid properties. Measurements configured to be executed include acoustic impedance, speed of sound, specific gravity, kinematic viscosity, particulate content, elemental analysis, and slurry agglomeration characterisation. The processed fluid, optionally processed to a binary or near-binary state (i.e. the processed fluid has only one or two elements in), passes over the sensing region where the control system may isolate frequency dependent attenuation profiles via Fast Fourier Transform (FFT) to distinguish solid metal particulates from entrained gases based on complex phase signatures. For highly processed fluids, elemental analysis may be supported by a pre-established calibration matrix. To provide additional validity, this phase data may be coupled with an additional shear-wave verification step; because gases completely reject shear waves, the system mathematically isolates the shear attenuation profile at the solid-liquid boundary to exclusively quantify the solid fraction, which is then subtracted from the longitudinal profile to definitively decouple the gaseous bubbleconcentration. Telemetry from the sensing apparatus may be provided to a deterministic closed-loop controller, which actuates downstream valves in milliseconds to dynamically route the fluid into onward sorting or directly into collection vessels upon meeting programmed thresholds, or into recirculation loops if further processing is required. Internal Combustion Engine Exhaust Monitoring

[0254] A fluid sensing apparatus may be deployed in the exhaust line of an internal combustion engine for the real-time monitoring of exhaust gases and the closed-loop optimisation of combustion parameters. The target fluid may be a high-temperature, high-velocity exhaust gas mixture containing variables such as oxygen, nitrogen oxides, carbon monoxide, hydrocarbons, particulate matter (pm), soot, nitrogen, carbon dioxide, water, sulfur oxides, nitrous oxide, ammonia, and acetaldehyde. The apparatus may be geometrically scalable for installation in automotive gasoline engine exhaust pipes having internal diameters between 40 mm and 130 mm, as well as other combustion engines having pipe diameters ranging from 30 mm up to 2000 mm, including heavy haul, marine, power generation, and large marine two-stroke engines running on fuels including 2-stroke fuel, nitromethane, methanol, white gas, gasoline, petrodiesel, ethanol, biodiesel, liquefied petroleum gas, compressed natural gas, aviation gasoline, marine diesel oil, heavy fuel oil, liquefied natural gas, syngas, ammonia and hydrogen. For high-flow rate conditions, a sampling bypass, a dead leg or plenum box may be used to condition the flow to a reduced or stabilised flow velocity to support measurements requiring precise acoustic velocity measurements. The control system may concurrently measure the local flow rate in parallel with gas species analysis to dynamically compensate for flow-induced measurement errors. To mitigate fouling or condensation, this section of the apparatus may include a self-cleaning geometry or a purge port to periodically flush the measurement zone, optionally triggered by the control system upon detection of a signal attenuation threshold. The sensing apparatus may comprise an internal instrumented foil array configuration, as described in relation to Figures 12a and 12b, wherein a plurality of aerodynamic foils project into the exhaust stream, which may be profiled to minimise vortex shedding and may incorporate damping layers to suppress flow-induced vibration, defining fixed measurement gaps. To extend the life of the sensing apparatus experiencing the extreme thermal and highly corrosive environment, the reflector bodies and protective encapsulations may be fabricated from Inconel, Stainless Steel, or Alumina ceramics and may be configured for flexural mode operation or may comprise an acoustic impedance gradient. An internal reference feature cavity may be integrated into the reflector body to facilitate automated temperature compensation. The transducers may be specifically configured to emit multi-frequency longitudinal waves in the 1 kHz to 1.5MHz range (e.g., 100 kHz, 250kHz, 500 kHz). Gap distances may be controlled to ensure signal propagation and high-levels of measurement sensitivity in both the time and frequency domain.

[0255] A specifically tuned, multi-frequency longitudinal transducer array may be provided across the exhaust stream which may allow the simultaneous capture of frequencydependent absolute Time-of-Flight and broadband attenuation signatures to accurately derive both phase velocities and molecular relaxation peaks. These dynamically extracted acoustic profiles may be iteratively cross-referenced against a multidimensional lookup matrix of equations of state temperature-dependent relaxation shifts, and stored critical constants to quantify dominant individual gas species, or target binary and ternary subsets within the complex exhaust matrix. The measurements may be compared to acceptable limits and if a threshold is breached, an output signal from the controller may be transmitted directly to an Engine Control Unit (ECU). The ECU may transmit further signals derived from the acoustic phase to optimise conditions, for example to dynamically trim fuel injector pulse durations and modulate the exhaust gas recirculation valve, thereby providing a continuous closed-loop suppression of unwanted emissions.

[0256] Wastewater Process

[0257]

[0258] The fluid sensing apparatus may be provided in an automated closed-loop process control within fluid processing networks, such as water treatment facilities. The fluid sensing apparatus may comprise a multi-modal ultrasonic sensor arranged in a bifurcated configuration, as described in relation to Figures 11a and lib, with a selectively dimensioned fixed gap. The sensor may be arranged at critical locations throughout a plant including pipes, tanks, vessels, feeds, filters, containers, channels, chambers, clarifiers, pump suction and discharge zones, basins, tanks, inlets, digesters, discharges, centrifuges or any process core, influent, or effluent to measure different physical and chemical properties in real-time. The sensor housing and reflector body may be fabricated from highly resistant and chemically compatible materials including AISI 316L stainless steel, Titanium (Ti6AI4V), or alumina for alkaline streams, or chemically resistant fluoropolymers such as PTFE, PVDF, PFA, ETFE, PCTFE, or FEP for acidic streams, with both longitudinal and shear piezoceramic transducers with physical thicknesses ranging from 0.02 mm to 15 mm, and widths from 0.2 mm to 20 mm. This helps to provide resistance to corrosive effluents. The sensor housing and reflector body may be formed of different materials.

[0259] The sensor may comprise transducer arrays emitting both longitudinal and shear waves across a broad frequency spectrum from 30 kHz to 50 MHz. Utilising combinations of pulse-echo boundary reflection and pitch-catch through-transmission, the controlsystem may process time-of-flight data and calculate complex frequency dependent reflection coefficients from signals transformed via fast Fourier transform. This acoustic processing can provide real-time calculation of target parameters including kinematic viscosity (derived from simultaneous density and dynamic viscosity tracking), the decoupled quantification of bubble and particulate content by mathematically separating shear boundary reflection and longitudinal attenuation profiles, and molecular weight using frequency dependant acoustic attenuation spectroscopy.

[0260] These real-time physical and chemical property measurements may be transmitted to a Programmable Logic Controller (PLC) to execute automated closed-loop interventions across varying fluid types, including non-Newtonian primary sludge and chemical reagents. In a primary feedback configuration, the PLC utilises a Proportional-Integral-Derivative (PID) control algorithm to dynamically adjust a Variable Frequency Drive (VFD) or equivalent actuator on a sludge transfer pump in direct response to real-time viscosity shifts, thereby optimising energy efficiency and preventing blockages. In a secondary compound configuration, the system may execute automated chemical dosing, utilising flow-paced feedforward logic combined with a PID feedback trim derived from the sensor's real-time composition measurements to control chemical metering pumps.

[0261] Multi-Parameter Gas Property Sensor Manifold for Semiconductor Fabrication Process imisation

[0262] The fluid sensing apparatus may comprise an instrumented manifold configured to mount in-line onto existing industrial piping or ducting ranging from 12 mm to 2000 mm internal diameter. The fluid sensing apparatus may comprise a multi-frequency longitudinal ultrasonic sensor comprising a plurality of ultrasonic transducer elements mounted upon an acoustically tuned backing plate. The transducer elements may be configured to sweep a frequency spectrum ranging from 1 kHz to 50 MHz, simultaneously emitting and receiving longitudinal compression waves. The active sensing elements may be arranged away from the wetted process fluid to reduce the risks of particulate contamination and material outgassing when exposed to highly reactive process chemistries such as CF4, SF6, SiH4, NF3, Trimethylaluminum (TMA), and Tetrakis(dimethylamido)titanium (TDMAT).

[0263] The ultrasonic transducer arrays may be integrated into aerodynamic, pressure-balanced internal foils supported by a dedicated manifold. These instrumented foils, as described in relation to Figures 12a and 12b, define a fixed controlled gap between adjacent foils, receiving the fluid and transmitting signals directly through the centre of the medium. Therefore, the instrumented foils may be implemented over largedimensional ranges where the distances between the foils are decoupled from the pipe diameter. The apparatus may further comprise at least one reflector body arranged such that ultrasonic waves transmit through the body and reflect off the boundary interface with the fluid. An internal reference feature, comprising an air gap, sealed reference cavity, or known material, may extend (only) partially across the acoustic wave path. A first proportion of the wave may bypass the reference feature to interrogate the fluid within a sample testing time-domain window, while a second proportion may reflect off the reference feature to support auto-calibration within.

[0264] The apparatus may simultaneously capture frequency-dependent Time-of-Flight and broadband attenuation signatures to determine both phase velocities and molecular relaxation peaks. These dynamically extracted acoustic profiles may be iteratively cross-referenced against a multidimensional lookup matrix of equations of state and stored critical constants, accounting for carrier-gas specific molecular energy transfer rates, to quantify individual gas species within the gas mixture. Mixture concentrations can be identified by deriving adiabatic compressibility from fluid density and acoustic velocity. These data extraction methodologies enable high-speed closed-loop feedback control in critical industrial environments. In a first industrial scenario, the apparatus may continuously monitor the dilution ratio of a critical etchant gas blend comprising NF3 or CF4 and an Argon binary carrier gas at the Point-of-Use immediately preceding a semiconductor dry etching chamber. The sensor may measure the acoustic impedance and acoustic velocity to determine the quantitative molar fraction of the blend. If an incorrect dilution ratio is detected, which may result in sidewall bowing or loss of etch selectivity, the system may trigger an automated sub-second, or optionally submillisecond hardware interlock to halt the gas flow before it reaches the process chamber. This may be done by transmitting a control signal to a valve. This can eliminate wafer scrap and dynamically optimise abatement scrubber systems for environmental compliance. In a further exemplary embodiment, the apparatus may be configured to monitor the physical properties of a precursor vapour mixture within a heated delivery conduit disposed downstream of a vapourising vessel or bubbler. The sensor system may continuously monitor the mixture ratio and the molecular weight of the vapour stream to determine the real-time concentration of a precursor such as, but not limited to, TMA or TDMAT, entrained within a carrier gas. Furthermore, by evaluating the molecular weight, the system may detect compositional anomalies indicative of thermal degradation, premature condensation, or oligomerisation of the precursor molecules. Upon detecting a deviation from a predetermined target profile, an integrated processor or controller may execute a closed-loop feedback operation. For example, a control signal may be transmitted to one or more heating elements operably coupled to thevapourising vessel or the associated delivery conduits. This continuous thermal modulation may precisely adjust the vapourisation temperature to optimise the precursor vapour pressure and stabilise the desired mixture ratio, thereby mitigating thin-film deposition defects while actively preventing the thermal breakdown of the precursor material.

[0265] Wide-Spectrum Multi-Modal Probe for Precursor Characterisation

[0266] The fluid sensing apparatus may be configured for the real-time, in-situ characterisation of complex fluid properties in highly sensitive semiconductor-grade liquid precursors. The system may monitor a wide range of fluids, including but not limited to Tetraethyl orthosilicate (TEOS), Trimethylaluminum (TMA) , highly reactive Lewis acidic precursors, and complex multi-component cocktails such as Lead Zirconate Titanate thin-film precursor (PZT-TF) and Barium Strontium Titanate (BST) formulations dissolved in organic solvents.

[0267] The fluid sensing apparatus may comprise an ultrasonic sensor housing a plurality of piezoelectric transducer elements mounted on an acoustically tuned backing plate. To enable wide-spectrum analysis, the transducer array may comprise multi-frequency longitudinal transducers operating from 0.5 MHz to 15 MHz, alongside multi-polarisation shear transducers operating from 0.2 MHz to 30 MHz. The fluid sensing apparatus may be arranged in at least two arrangements. Firstly, the transducers may be embedded within a threaded multi-modal in-ampoule probe. This probe is configured to be vertically inserted directly into standard semiconductor process ampoules or high-capacity bulk delivery vessels possessing volumetric capacities ranging from 0.5 Litres to 50 Litres. This probe may comprise an external reflector body fabricated from alumina, sapphire and / or 316L stainless steel and may further comprise an internal time-domain reference air gap. This can provide continuous signal amplitude and thermal calibration where the surface acts as a solid-fluid reflector boundary. The multifrequency longitudinal waves may propagate past the reflector body and through the liquid precursor reflecting off the internal ampoule wall.

[0268] In another arrangement, the fluid sensing apparatus may comprise a multi-modal, multi-frequency array configured for non-intrusive external mounting to the outside of the ampoule or delivery pipeline. The array may be fixed to the exterior wall using a high-tension fixing mechanism, for example a band clamp or tension strap fabricated from a high-temperature alloy like Alloy 625, or any other mechanical clamping system. To ensure repeatable acoustic coupling, a non-contaminating coupling medium is used for example a high-purity dry-coupled elastomer pad or thermally conductive inorganic cement. Multi-frequency longitudinal waves may propagate through the ampoule walland may be partially reflected at the solid-liquid interface. The remaining wave energy may propagate through the liquid precursor reflecting off the internal back wall.

[0269] The control system may receive sensor output signals during a specified sample testing time-domain window and may calculate a plurality of fluid properties. These may include fluid properties such as the speed of sound, acoustic impedance, precursor mass density, kinematic viscosity, shear-dependent viscosity, and viscoelastic moduli.

[0270] The continuous data feed may provide one or more automated closed-loop feedback configurations. For example, if the control system generates a severe alert based on elevated inferred molecular weight or particulate content indicating a degraded precursor batch, a control signal may be transmitted to a pneumatic diverter valve to automatically lock out the fluid from the semiconductor manufacturing process. This automated intervention can reduce yield loss and minimises hazardous chemical waste.

[0271] Ultrasonic Sensor Array for EUV Molten Tin Characterisation and Control

[0272] The fluid sensing apparatus may be configured to characterise and control molten tin, which serves as the primary fuel source within a laser-produced plasma (LPP) Extreme Ultraviolet (EUV) lithography droplet generator. The fluid sensing apparatus may generate a high-resolution, real-time output of the fluid's density, viscosity, and flow rate to ensure that the tin droplets maintain a strictly controlled diameter. The fluid sensing apparatus may comprise a high-temperature resistant manifold which may define a fluid path. The fluid sensing apparatus may further comprise a solid reflector body which may be formed of Alumina, optionally with oxide coating, Sapphire or Zirconium. This can enable the fluid sensing apparatus to withstand high thermal loads and resist chemical erosion. These materials can provide an acoustic impedance match with the molten tin. The fluid temperature within the manifold may be maintained between 232°C and 600°C. The ultrasonic sensor may comprise an acoustically tuned multi-modal ultrasonic sensor array comprising both longitudinal and shear wave transducers embedded within the manifold, operating within a frequency range of 100 kHz to 50 MHz to emit and receive ultrasonic waves with a plurality of polarisations and frequencies. An internal air gap may be embedded within the reflector body to serve as a reference feature for absolute thermal calibration of the acoustic signal.

[0273] The control system may process the raw sensor output by isolating a predetermined sample testing time-domain window corresponding to the boundary between the reflector body and the molten tin. The control system may determine the acoustic impedance and absolute density of the fluid by comparing the peak amplitude of a reflected longitudinal wave against an internal reference feature, while concurrently using a pitch-catch transmission to extract the speed of sound via time-of-flight cross-correlation. Dynamic viscosity may be computed by applying a Fast Fourier Transform to reflected shear wave signals from the solid-fluid interface to extract the complex shear reflection coefficient. This may be used to determine both magnitude and phase shift.

[0274] The determined property fluids may provide distinct feedback loop configurations: thermal regulation, pressure regulation, and piezoelectric (PZT) or high-temperature electroacoustic actuation. By synchronising the mechanical modulation waveform with the quantitative real-time properties of the molten tin, the formation of off-axis satellite droplets may be prevented, maximising the conversion efficiency of the CO2 laser-produced plasma and substantially mitigating particulate degradation of the highly sensitive EUV collector optics.

[0275] A Low-Cost Acoustic Sensor for Health Monitoring

[0276] The fluid sensing apparatus may comprise a micro-machined ultrasonic sensor assembly comprising a Piezoelectric Micromachined Ultrasonic Transducer (PMUT) array or a Capacitive Micromachined Ultrasonic Transducer (CMUT). The PMUT array may comprise a plurality of individual transducer elements utilising piezoelectric thin films, such as PZT or AIN. These may have a thickness in a range between 0.2 micrometers and 5.0 micrometers. The array may be configured to generate and receive broad-bandwidth ultrasonic waves across a frequency spectrum of 1 MHz to 50 MHz.

[0277] The sensor assembly may further comprise a solid reflector body that extends from the PMUT array to interface with a microfluidic channel. The channel may define a known geometry gap or series of known gaps dimensioned between 5 micrometers and 2mm to ensure efficient acoustic propagation. Optionally, the gap may be tuned to match the transducer resonant frequency. This can enable constructive and destructive interference to be tracked in the frequency domain. The fluid sensing apparatus may be configured for acoustic mode conversion. In such configuration, a portion of the solid boundary of the reflector body interfacing with the known geometry gap may be geometrically angled. Corresponding incident longitudinal compressional waves emitted by the PMUT array may strike this solid-fluid boundary at an oblique angle configured to exceed the critical angle for mode conversion. Due to the acoustic impedance mismatch at the interface, a predictable portion of the longitudinal wave undergoes mode conversion, generating a resultant transverse shear wave. The fluid sensing apparatus may further comprise internal reference features comprising air gaps extending partially across the acoustic wave path and integrated into the reflector body to provide a known reflection signal for continuous system calibration.A control system may receive the reflected and transmitted acoustic signals captured by the PMUT array within sample testing time-domain windows. By applying mathematical transformations, including Fast Fourier Transforms (FFT), the system may determine complex reflection coefficients and absolute Time of Flight data. The system may apply this acoustic data to calculate clinical parameters from a fluid sample such as a single blood drop. Haematocrit may be identified by mathematically isolating the erythrocyte-derived longitudinal scattering profile from background plasma noise via Fast Fourier Transform (FFT) based acoustic attenuation spectroscopy. Cardiovascular disease risk may be assessed by generating a shear-dependent viscosity curve derived from the multi-frequency shear sensors. Changes associated with coagulation and sepsis risks may be monitored by calculating the viscoelastic storage and loss moduli from the shear wave phase lag, allowing the identification of structural blood clot formation. Concurrently, acoustic signatures correlating to metabolic markers such as glucose, protein, and osmolarity profiles may be mathematically isolated via multi-frequency acoustic dispersion profiling. This may be carried out by utilising an internal reference feature to compensate for thermal and environmental drift in order to resolve the acoustic velocity shifts associated with these markers.

[0278] The fluid sensing apparatus may provide automated closed-loop feedback. An acoustic self-calibration loop may be provided by a reference air gap echo to dynamically adjust transducer voltage and gain, neutralising environmental drift. Additionally, a shear rate control loop may use the real-time calculated viscosity as a feedback signal to an integrated micro-pump, actively modulating fluid flow to maintain a constant shear rate within the known geometry gap.

[0279] The system may be integrated into a range of form factors including benchtop analysers, and wearables, in-line, non-invasive transcutaneous applications, or in vivo. One example includes a battery-powered handheld clinical analyser. Such an analyser may weigh approximately 650 grams. The second form factor may be a smartphone-connected consumer device comprising a small docking module. Such module may facilitate the home monitoring of chronic conditions such as diabetes and anticoagulation therapy.

[0280] The sample fluid interaction with the sensor assembly may be structurally defined by one of three primary form-factor configurations. Firstly, in a reusable direct contact, the sensor assembly may interface directly with the fluid. To withstand repeated clean-in-place sterilisation protocols and mitigate biofouling without heavily attenuating the acoustic signal, fluid-contacting surfaces may comprise robust, biocompatible materials like Parylene-C, titanium alloys, or passivated silicon nitride. Secondly, for complete separation, the sample fluid may remain entirely isolated within a disposable cartridge.Such cartridge may have a wall comprising a material composition and thickness tuned to function as an acoustic sensitivity layer. The analyser comprises a mechanical clamping mechanism that may lock the cartridge against the sensor face to provide uniform acoustic coupling. Thirdly, the transducer assembly may be housed entirely within the disposable sample cartridge. The fluid directly contacts the internally housed sensor, while the reusable instrument acts solely as an electronic reader, utilising mechanical connectors to establish direct electrical contact with the cartridge.

[0281] These arrangements may be used to analyse other biological fluids, specifically urine, saliva, sweat, and tears, typically utilising micro-volumes in the range of 1 to 5 microliters. The sensor assembly may be configured to extract multi-frequency acoustic data correlated with a broad spectrum of physical and chemical parameters, including specific gravity, osmolarity, pH, conductivity, density, viscosity, bacterial or particle counts, and protein composition. This can enable comprehensive urinary and renal screening (e.g., for chronic kidney disease, pre-eclampsia, and urinary tract infections), saliva-based screening for periodontal disease and correlated systemic conditions, localised tear analysis for dry eye and ocular surface disease assessment via osmolarity tracking, and specialised sweat analysis for cystic fibrosis diagnostics and continuous hydration monitoring.

[0282] Smart-Dispensinq-Manifold for Advanced Photoresist Property Control

[0283] The fluid sensing apparatus may comprise an ultrasonic sensor comprising a 1 to 50 MHz longitudinal and 1 to 20 MHz shear-wave transducer array. The fluid sensing apparatus may further comprise an alumina or sapphire reflector body with internal time-domain reference gap features and ultra-high-purity Polyetheretherketone (PEEK) frequency matching front-face sensitivity layers. The system may monitor fluids ranging from Extreme Ultra Violet (EUV) resists with viscosities of the order of 2.76 mPaS to packaging resins with viscosities of the order of 5700 mPaS and is capable of characterising opaque fluids. By analysing acoustic reflection from the solid-fluid interface and frequency-dependent attenuation through the bulk fluid, shear-dependent viscosity, complex moduli, and compressibility / microbubbles are characterised and reported in real-time. These metrics may provide a semiconductor messaging standard, such as SECS / GEM, integrated closed-loop adjustments for spin-coating RPM, pump volumetric rates, and bubble-triggered purge to ensure optimum process fluid properties.

[0284] Multi-Parameter Monitoring for Immersion Lithography

[0285] The fluid sensing apparatus may comprise an ultrasonic sensor comprising a 20-50 MHz pulse-echo longitudinal transducer array. This may be provided in a non-invasive fusedquartz manifold, or other material adapted to the specific fluid chemistry, housed within an immersion shower head conditioning channel. This may enable monitoring Ultra-Pure Water (UPW) and Gen 2 fluids such as decalin, decahydronaphthalene, cycloalkanes, polycyclic alkanes, and linear alkanes, along with aqueous solutions containing heavy metal inorganic salts such as barium chloride, calcium chloride, and lanthanum chloride, mixtures of crown ethers with salts, strong acids like sulfuric acid and phosphoric acid, surfactants, quaternary ammonium salts, and metal oxide nanoparticle dispersions. This enables the determination of acoustic impedance, time-of-flight, and frequency sweeps to extract absolute thermodynamic density (tracking refractive index and contamination) and bulk compressibility (detecting cavitation). This real-time data can provide immediate closed-loop actions: thermal density drifts trigger valves to correct temperatures, and contamination initiates flushing or interlocks. Concurrently, aeration-induced compressibility shifts prompt fluid delivery adjustments such as hood pressure adjustments, flow rate modifications, scan speed throttling, or temporary purging to eliminate bubbles.

[0286] Direct Liquid Injection (DLI) Ultrasonic Viscosity Control System

[0287] The fluid sensing apparatus may comprise an ultrasonic sensor comprising a two-dimensional array of multi-frequency longitudinal and multi-polarisation shear wave transducers. The ultrasonic sensors may be provided in an Embedded Reflectometric Viscoelastic Manifold. Utilising Maxwell and / or Greenwood data treatment algorithms depending on the fluid's viscoelastic properties, the control system may determine the shear-rate-dependent complex viscosity, density, and viscoelastic phase angle of the fluid. This is particularly advantageous in highly volatile liquid organometallic and high-k dielectric precursors where such sensor may be embedded into a fluid chamber manifold just upstream of the DLI piezo valve. The fluid sensing apparatus may comprise an acoustically tuned reflector body which may be formed of chemically inert materials such as alumina, sapphire or quartz with an optional matching sensitivity layer. This arrangement may reduce outgassing and contamination. The assembly is designed considering hermeticity, connector sealing, and / or moisture exclusion wherein the reflector body or manifold may be structurally dimensioned / sized to act as a pressure boundary that isolates the transducers from the fluid. The fluid sensing apparatus may enable closed-loop control to halt the DLI pump or adjust vapouriser settings if thresholds are breached within highly pressurised liquid or supercritical delivery lines up to 70 MPa at ambient or elevated temperatures. This enables optimal droplet atomisation, reduces liquid-phase defects, reduces vapouriser clogging, and significantly extends deposition hardware lifespan.

[0288] Smart-Instrumented-Manifold for Characterisation for Blending and DistributionThe fluid sensing apparatus may comprise an ultrasonic sensor comprising multifrequency longitudinal and multi-polarisation shear transducers. The transducers may be mounted to an inert acoustically matched reflector, ensuring zero wetted contact between the transducer elements with the fluid. The transducers may reflect waves off the reflector-fluid interface and longitudinal waves may propagate from the wetted boundary through the opaque, non-Newtonian Chemical Mechanical Planarization (CMP) slurries and hydrogen peroxide blends. Optionally, a reference feature is integrated in the reflector body for temperature compensation. By monitoring the received waves, acoustic impedance, compressibility, and attenuation spectra measurements may be taken to determine mix ratio, detect agglomerations, and characterise microbubbles. A control system may receive these determined properties and operate a closed-loop control to automate PID-driven chemical spiking, initiate pneumatic flow diversion for agglomerates, and suspend endpoint metrology or polishing operations when microbubbles appear. This can stabilise material removal rates, reduce micro-scratch defects, and minimise consumable costs.

Claims

48Claims1. A fluid sensing apparatus for monitoring a fluid comprising:an ultrasonic sensor comprising a plurality of ultrasonic transducer elements arranged to emit and receive ultrasonic waves with a plurality of polarisations and / or frequencies, wherein the ultrasonic sensor is configured to generate a sensor output signal based on the received ultrasonic waves;a backing plate, wherein the ultrasonic transducer elements are mounted on the backing plate; anda control system configured to:receive the sensor output signal from the ultrasonic sensor; and calculate at least one property of a fluid, wherein the at least one property is calculated based on the received sensor output signal during a sample testing timedomain window.

2. The fluid sensing apparatus according to claim 1, wherein the ultrasonic sensor comprises:a reflector body arranged such that the ultrasonic waves are transmitted through said reflector body,wherein the ultrasonic waves are reflected off a boundary of the reflector body back towards the ultrasonic transducers.

3. The fluid sensing apparatus according to claim 2, wherein the reflector body is mounted to the backing plate, wherein reflector body has a thickness such that it extends beyond the ultrasonic transducer elements so that the emitted ultrasonic waves travel through the reflector body and are reflected at a boundary between the reflector body and a fluid to be monitored, wherein the reflection is during the sample testing time-domain window.

4. The fluid sensing apparatus according to claim 2 or 3, wherein the ultrasonic sensor further comprises a reference feature, wherein the reference feature defines a boundary with the reflector body.

5. The fluid sensing apparatus according to any preceding claim, wherein each ultrasonic transducer element is arranged to receive reflected ultrasonic waves emitted from a different transducer element.

6. The fluid sensing apparatus according to any preceding claim, where the ultrasonic sensor comprises a second plurality of ultrasonic transducer elements which are configured to receive ultrasonic waves without actively emitting ultrasonic waves.

497. The fluid sensing apparatus according to any preceding claim, wherein the ultrasonic sensor comprises at least one of:an ultrasonic longitudinal wave transducer configured to transmit an ultrasonic longitudinal wave and to receive the ultrasonic longitudinal wave signal reflected from a boundary; andan ultrasonic shear wave transducer configured to transmit an ultrasonic shear wave and to receive the ultrasonic shear wave signal reflected from a boundary.

8. The fluid sensing apparatus according to claim 4, wherein the reference feature is embedded within the reflector body.

9. The fluid sensing apparatus according to claim 8, wherein the reference feature is an air gap or known material extending only partially across the path of the emitted ultrasonic wave such that a first proportion of the emitted ultrasonic waves do not interact with the reference feature and a second proportion of the emitted ultrasonic waves are reflected at the boundary between the reflector body and the reference feature.

10. The fluid sensing apparatus according to any preceding claim when dependent on claim 4, wherein the reference feature abuts an external layer of the reflector body or is at least partially covering an external layer of the reflector body.

11. The fluid sensing apparatus according to claim 10, wherein the reference feature is configured so that the emitted ultrasonic waves are partially reflected at the boundary between the reflector body and the reference feature and are partially transmitted through the reference feature.

12. The fluid sensing apparatus according to claim 11, comprising an acoustically tuned reflector layer arranged between the reference feature and the boundary to the fluid being monitored.

13. The fluid sensing apparatus according to claim 12, wherein the acoustic impedance of the acoustically tuned reflector layer has an acoustic impedance gradient between the transducer and the boundary to the fluid to be monitored.

14. The fluid sensing apparatus according to any preceding claim when dependent on claim 4, wherein the control system configured to:calculate at least one property of the reference feature, wherein the at least one property is calculated based on the received sensor output signal during a reference testing time-domain window, wherein the reference testing time-domain window is distinct from the sample testing time-domain window; and50compare the calculated at least one property of the reference feature with a known value of the at least one property to calibrate the ultrasonic sensor.

15. The fluid sensing apparatus according to any preceding claim, wherein the at least one property is calculated based on a change in amplitude of the reflected ultrasonic waves for different ultrasonic wave polarisations and / or frequencies.

16. The fluid sensing apparatus according to any preceding claim, wherein the at least one property is calculated based on a change in the time-of-flight of the reflected ultrasonic waves for different ultrasonic wave polarisations and / or frequencies.

17. The fluid sensing apparatus according to any preceding claim, wherein the at least one property is calculated based on a change in phase of the reflected ultrasonic waves for different ultrasonic wave polarisations and / or frequencies.

18. The fluid sensing apparatus according to any preceding claim, wherein the at least one property is calculated based on a comparison of the reflected ultrasonic waves detected by a transducer element distinct from the emitting transducer element.

19. The fluid sensing apparatus according to any preceding claim, wherein the at least one property is calculated based on reflected ultrasonic waves only.

20. The fluid sensing apparatus according to any preceding claim, wherein the ultrasonic sensor is configured to be removably couplable to a fluid chamber and / or flow line.

21. The fluid sensing apparatus according to any preceding claim, wherein the ultrasonic sensor is configured to be embedded into a fluid chamber manifold and / or flow line manifold.

22. The fluid sensing apparatus according to any preceding claim, wherein the ultrasonic sensor is on a probe wand configured to be inserted into a fluid to be monitored.

23. A method of determining at least one property of a fluid using a fluid sensing apparatus comprising an ultrasonic sensor, a backing plate, and a control system according to any preceding claim, the method comprising:emitting ultrasonic waves having a plurality of polarisations and / or frequencies from a plurality of ultrasound transducer elements;receiving ultrasonic waves having a plurality of polarisations and / or frequencies, wherein the received ultrasonic waves have reflected from a boundary between the ultrasonic sensor and fluid;generating a sensor output signal based on the received ultrasonic waves; and transmitting the sensor output signal to a control system, wherein the control system is configured to calculate at least one property of the fluid, wherein the at least51one property is calculated based on the received sensor output signal during a sample testing time-domain window.

24. The method according to claim 23, comprising:generating a control signal based on the at least one property calculated; transmitting the control signal to a component of a fluid processing system, wherein the component may be a display, a memory device, a further control system, a heating element, a mechanical stirrer, a dosing system, an actuator, a valve, a pump, a diverter and / or a pressure regulator.

25. The fluid sensing apparatus according to any preceding claim, where the ultrasonic sensor further comprises surface wave transducers configured to emit surface waves with a plurality of polarisations and / or frequencies.

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