Ultrasonic transducer health monitor

Abstract

An ultrasound-based system includes a transmitter and receiver, an ultrasonic transducer including ≥1 piezoelectric element having a matching layer thereon connected to the transmitter. A controller is coupled to the transmitter. The transmitter is used to drive the piezoelectric element with a pulsed electrical signal, wherein the piezoelectric element emits a transmitted ultrasonic signal. A coupled current / voltage measurement circuit is used to sense current or voltage in the transmitter. The controller is used to implement an algorithm for an ultrasonic transducer monitoring method including comparing an amplitude of the pulsed signal to a predetermined limit. When the pulsed signal is determined to be outside the limit, the impedance of the piezoelectric element is determined to be abnormal. When the pulsed signal is within the limit, then the amplitude of the received signal is compared to a lower limit, the amplitude being below the lower limit resulting in a determination that the ultrasonic transducer requires a cleaning operation.

Description

Technical Field

[0001] The disclosed aspects relate to ultrasonic transducer-based systems and devices having at least one ultrasonic transducer. Background Technology

[0002] Ultrasonic-based systems and devices having at least one ultrasonic transducer have applications including as fluid flow meters for oil and gas movement and transport, as non-destructive testing (NDT) devices, and for medical applications (including imaging for health monitoring). Ultrasonic transducers are known to include at least one piezoelectric element, which may include a front impedance matching layer and a backing layer, and a housing in the front, which may be a semi-open or fully closed housing. The performance of an ultrasonic transducer is typically most sensitive to variations in the performance of its piezoelectric element. Ultrasonic transducers may also include encapsulation for safety and / or application requirements, wherein the piezoelectric element is typically encapsulated by a polymer-based adhesive material, resulting in inaccessibility of the piezoelectric element without damaging the encapsulation.

[0003] Regarding flow meters, in various industries involving product flow, there is a need to accurately measure the amount of product flowing at any given time. Several different types of known flow meters exist. These known flow meters include mechanical flow meters (e.g., piston flow meters, Wolftmann flow meters, or jet flow meters, all of which measure the flow rate of fluid through some mechanical device), vortex flow meters (where vortices are generated by blocking part of the fluid path, thus producing voltage pulses whose frequency can be measured and therefore the flow rate can be determined), magnetic flow meters (which measure the potential difference of a conductive fluid due to an applied magnetic field and thus determine the flow rate), turbine flow meters, and rotary flow meters. Static flow meters, including ultrasonic flow meters (USM), are also known (meaning there are no moving parts).

[0004] Ultrasonic flow meters (USMs) are becoming increasingly common in fluid flow measurement because they can measure a wide range of different flow velocities with minimal pressure drop, and they also have non-moving parts, thus offering less mechanical maintenance and better reliability compared to most conventional flow meter types. A key hardware component in a USM is the ultrasonic transducer, also known as an ultrasonic sensor, which includes a piezoelectric element, typically a piezoelectric crystal or piezoelectric ceramic, usually lead zirconate titanate (PZT). As is known in physics, the piezoelectric effect is the ability of certain materials to generate an electric charge in response to applied mechanical stress, and vice versa.

[0005] While a USM may include a single ultrasonic transducer, it typically comprises at least a pair of encapsulated ultrasonic transducers, also known as "canned" ultrasonic transducers. Encapsulation refers to the ultrasonic transducer being encased within an adhesive material, which, as described above, is typically a polymer-based material. In the operation of a USM, the ultrasonic transducer operates by converting electrical energy supplied in the form of pulsed electrical drive signals. The transducer converts the received electrical energy into ultrasonic signals, which are then emitted and directed at the fluid being measured; conversely, the transducer also functions as an ultrasonic receiver.

[0006] As described above, the USM may include a housing, and within the housing may reside a printed circuit board (PCB) including a controller (such as a microcontroller unit (MCU) or digital signal processor) and other electronics, where the controller is typically battery-powered and / or externally line-powered. The electronics may include a radio frequency (RF) unit comprising a transmitter and receiver coupled to an antenna (typically located outside the housing) for providing wireless communication to the USM. The USM includes an ultrasonic transducer pair comprising a first ultrasonic transducer and a second ultrasonic transducer. In a conventional ultrasonic transducer arrangement, the transducers are configured on the same side of the pipe to generate a V-shaped ultrasonic signal path using a single reflection from the pipe after passing through the fluid. Another known ultrasonic transducer arrangement is a direct transport path type that does not involve any signal reflection. Several other known transducer arrangements exist, and the total number of ultrasonic transducers can be as high as approximately 16 or more, typically depending on the pipe diameter and cost constraints.

[0007] During each measurement cycle of the USM, a multiplexer is enabled, which can be located on a PCB that is communicatively coupled to be controlled by a controller. A first ultrasonic transducer acts as a transmitter for emitting ultrasonic waves, and a second ultrasonic transducer acts as an ultrasonic receiver. The ultrasonic transducers can then be switched to exchange roles, such that the first ultrasonic transducer acts as an ultrasonic receiver and the second transducer acts as an ultrasonic transmitter.

[0008] USM (Ultrasound-Scanning Meters) measure flow velocity by analyzing the interaction between emitted ultrasonic waves (or sound waves) and moving fluid. The two most common types of USM are Doppler (reflection) flow meters and transit time (time-of-flight) flow meters. Using the measured velocity and knowing the cross-sectional area of ​​the pipe, a USM can calculate the volumetric velocity of the fluid flowing through it.

[0009] It is known that energy coupling between an ultrasonic transducer and some fluid transport medium (e.g., air or other gases or water) is maximized when the fluid medium and the ultrasonic transducer have matched specific acoustic impedances. An ultrasonic transducer may include an impedance matching layer to more effectively couple ultrasonic energy emitted into the fluid and ultrasonic energy received by the transducer after passing through the fluid. The ultrasonic matching layer is typically a passive layer attached to the front of the ultrasonic transducer. A damping layer may also be disposed on the side of the ultrasonic transducer opposite the matching layer. Summary of the Invention

[0010] This summary is provided to introduce a simplified selection of disclosed concepts, which are further described below in detail with reference to the accompanying drawings. This summary is not intended to limit the scope of the claimed subject matter.

[0011] The disclosed aspects recognize the performance of encapsulated ultrasonic transducers or pairs of encapsulated ultrasonic transducers in ultrasonic transducer-based systems or devices, and that the lifespan of the ultrasonic transducer is affected by the encapsulated piezoelectric element and the electrical connection between the electrodes on the piezoelectric element and the external environment. Such ultrasonic transducers as described above may include a matching layer and a damping layer on the piezoelectric element. Encapsulation prevents the ultrasonic transducer from being repaired or maintained without removing / destroying the encapsulation. To improve the reliability of ultrasonic transducer-based systems or devices with encapsulated ultrasonic transducers, the disclosed aspects include health monitoring of the encapsulated ultrasonic transducers with predictive maintenance, which eliminates the usual need to remove the ultrasonic transducer from its application for repair or maintenance.

[0012] Furthermore, it is recognized that in the case of a USM (Unified Ultrasonic Transducer) mounted on a pipe section for field operation to measure fluid flow, a known frequent failure mode is deformation and / or aging of the piezoelectric element of the ultrasonic transducer, including the commonly used PZT material. Another failure mode is contamination of the mating layer by materials / substances carried by the fluid flowing within the pipe. It is known in the art that these two different USM failure modes cannot be distinguished. A third failure mode of the USM concerns its electrical connection to the electrodes of the piezoelectric element, where the wires may not be properly soldered or may become loose on the electrodes, thus potentially changing position, or the wires may separate due to strain, vibration of the piezoelectric element itself, or due to external vibrations propagating in the pipe.

[0013] Furthermore, in conventional methods for monitoring the health of ultrasonic transducers in ultrasound-based systems or devices (such as USMs), the only signal analyzed is the receiver-side signal. For a USM, there may be more than one pair of ultrasonic transducers, and / or for a USM, even if it supports more than one channel, it may have a single pair of ultrasonic transducers. A channel, as defined herein and as used in the art, refers to an ultrasonic signal emitted in an upstream direction (e.g., from ultrasonic transducer A to ultrasonic transducer B), and a second channel in a downstream direction (i.e., from ultrasonic transducer B to ultrasonic transducer A), wherein the USM has at least one path.

[0014] For example, if the amplitude of the receiver-side signal in one channel is found to be significantly smaller than the amplitude of the receiver-side signal in another channel / path with a different pair of ultrasonic transducers installed, it can be inferred that the pair of ultrasonic transducers being evaluated is not functioning correctly. Similarly, if the amplitude of the receiver-side signal is significantly smaller than its historical signal level, it can also be inferred that the pair of ultrasonic transducers is not functioning correctly. However, this known monitoring method cannot identify the cause of the signal attenuation required to take corrective / remedial measures.

[0015] One disclosed embodiment includes an ultrasound-based system comprising a transmitter and a receiver, and an ultrasonic transducer including at least one piezoelectric element having a matching layer thereon connected to at least the transmitter. A controller is coupled to the transmitter. The transmitter is used to drive the ultrasonic transducer with a pulsed electrical signal, and in response, the ultrasonic transducer emits an ultrasonic signal. A current or voltage measurement circuit is coupled to sense current or voltage in the transmitter. The controller is used to implement an algorithm for an ultrasonic transducer monitoring method, the method comprising comparing the amplitude of the pulsed signal with at least one predetermined limit. When the pulsed signal is determined to exceed the predetermined limit, the impedance of the piezoelectric element is determined to be abnormal. When the pulsed signal is found to be within the predetermined limit, the amplitude of the received signal is compared with a lower limit, the amplitude of which, if below the lower limit, results in a determination that cleaning operations for the matching layer are required. Attached Figure Description

[0016] Figure 1A This is a block diagram of an exemplary USM, according to an exemplary aspect, installed on a pipe section for measuring the flow rate of fluid flowing through the pipe section, wherein the USM includes an ultrasonic transducer pair, the ultrasonic transducer pair including a first ultrasonic transducer and a second ultrasonic transducer that together realize indirect path (reflection path) sensing, wherein the USM is shown as including a current measurement circuit coupled to a transmitter.

[0017] Figure 1BThis is a block diagram of an exemplary medical ultrasound imaging system for health monitoring. The probe shown includes at least one ultrasound transducer composed of an array of piezoelectric elements, each of which emits focused ultrasound energy into the body and receives the resulting ultrasound reflections.

[0018] Figure 2 It is a block diagram representation of a corresponding component of an exemplary current measurement circuit coupled to a portion of the transmitter of an ultrasonic transducer-based system or device, according to an exemplary aspect.

[0019] Figure 3 Exemplary pulse current waveform patterns are shown, illustrating waveforms with high amplitude limits, waveforms with low amplitude limits, and waveforms with normal amplitude.

[0020] Figure 4 This is a flowchart illustrating the steps in an exemplary method for monitoring the health status of an ultrasonic transducer in an ultrasound-based system or device. Detailed Implementation

[0021] The disclosed embodiments are described with reference to the accompanying drawings, in which the same reference numerals are used throughout the drawings to denote similar or equivalent elements. The drawings are not drawn to scale and are provided only to illustrate certain aspects of the disclosure. Several aspects of the disclosure are described below with reference to exemplary applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a complete understanding of the disclosed embodiments.

[0022] Figure 1A This is a block diagram depicting an exemplary USM 100 for measuring the flow rate of fluid flowing in a pipe section of pipe 160, wherein the USM 100 includes an ultrasonic transducer pair comprising a first ultrasonic transducer and a second ultrasonic transducer shown as T1 and T2, each transducer including at least one piezoelectric element shown as 121 of T1 and 122 of T2, wherein T1 and T2 together achieve indirect path (reflection path) sensing. As mentioned above, another known ultrasonic transducer arrangement is a direct transport path type that does not involve any ultrasonic reflection (i.e., face-to-face), and another type of single transducer that provides both Tx and Rx using a single reflection path may also exist.

[0023] USM 100 is shown as including a current or voltage measurement circuit 200 that is located close to or electrically coupled to sense a pulsed electrical signal (hereinafter “pulse signal”, typically a pulsed current) flowing in the transmitter (Tx) 111. One way to sense the pulsed current is by adding a sensing resistor 225 connected in series within Tx 111, as described below. Figure 2As shown, the voltage across the sensing resistor 225 can be easily converted into current using Ohm's law. Another exemplary way to sense a pulse current is by including a Hall effect sensor located near the side (non-contact), which is a device for measuring the amplitude of the magnetic field generated by the pulse current, wherein the level (amplitude) of the pulse current can be determined by the measured magnetic field.

[0024] USM 100 is shown as including an outer housing 108 (also referred to as a casing) having ultrasonic transducers T1 and T2 on the same side of a pipe section 160, wherein T1 and T2 are spaced apart from each other by a distance d. This casing enables a reflective path (indirect path) sensing configuration. The ultrasonic transducers T1 and T2 are shown as including a matching layer 140 facing the pipe section on one side of piezoelectric elements 121 and 122, and a damping layer 127 is positioned on the piezoelectric elements 121 and 122 opposite to the matching layer 140. An encapsulation layer 173 is present, shown as encapsulating both T1 and T2. Housing 108 may comprise various different materials, including brass, titanium, aluminum alloy, or possibly plastic, depending on the application.

[0025] As is known in acoustics, the thickness of the matching layer 140 is typically equal to one-quarter of the sound wavelength (λ / 4) to minimize reflections at the front of the matching layer 140, thus favoring the emitted wave. Having found the optimal impedance value, the next step is to determine the material used to find one with that specific impedance. For this purpose, the known Mason model, used as a theoretical matching layer modeling algorithm, can be used. A suitable thickness for the matching layer 140 may also be found through computer numerical simulation or comparative testing.

[0026] The damping layer 127 typically comprises a low-density material, such as porous foam or polymer. The damping layer 127 may optionally also include a relief layer, which typically also comprises a low-density material, such as porous foam or polymer.

[0027] USM 100 is attached to pipe sections of pipe 160, typically using an airtight and high-pressure resistant mechanism inserted into the pipe section, or configured as a clamping device mounted externally to the pipe section. Although Figure 1A Not shown, but T1 and T2 may each have their own separate encapsulation chamber.

[0028] As described above, piezoelectric elements 121 and 122 are typically piezoelectric crystals or piezoelectric ceramics (typically PZT) that vibrate when a pulse signal (received from Tx 111) is applied to them, thereby generating ultrasonic waves. When a pulse signal is applied to piezoelectric elements 121 and 122, the piezoelectric elements will resonate at a frequency where their impedance is at its minimum. Accordingly, the current drawn into Tx 111 is at its maximum. In operation, enabled by a numerically controlled multiplexer (MUX) 115, ultrasonic pulses are alternately emitted by one of the piezoelectric elements 121 and 122 of the ultrasonic transducers for T1 and T2, and received by the piezoelectric element of the other ultrasonic transducer required for flow measurement. When a single transducer is used for both Tx and Rx, the MUX 115 functions as a switch or duplexer.

[0029] Angled axial signal path in Figure 1A The dashed lines inside the pipe are shown in the diagram. As is known in the art, the USM 100 may include... Figure 1A The diagram shows more than two ultrasonic transducers, typically ranging from two to 16, or even more, depending on the tube diameter, in T1 and T2. Although USM 100 is shown as including separate Tx 111 and receiver (Rx) 112, a single transceiver may also exist as an alternative to the shown separate Tx 111 and Rx 112, coupled to T2 and T1 respectively by MUX 115. This MUX allows the piezoelectric elements T2 and T1 to exchange (alternately) transmit and receive roles, such that Tx 111 is on at one moment and Rx 112 is on at another moment. The operating conduit 160 contains a fluid, which may be a liquid or gas, such as natural gas or hydrogen.

[0030] USM 100 generally also includes a controller 120, which typically includes a microprocessor, digital signal processor (DSP), or MCU. This controller has an associated memory, shown as “MEM” 124, which stores code for algorithms, including algorithms for implementing the disclosed methods and for fluid velocity measurement. Controller 120 is coupled to Tx 111 and Rx 112, and is also coupled to control MUX 115. Controller 120 is also configured to control MUX 115 to switch Tx and Rx roles in specified time slots.

[0031] The algorithm executed by controller 120 can be implemented in hardware and / or software. Regarding a hardware-based implementation, the algorithm equations can be translated into digital logic gate patterns, such as using VHDL (Hardware Description Language), which can then be implemented using programmable devices (such as Field Programmable Gate Arrays (FPGAs), Complex Programmable Logic Devices (CPLDs), or Application-Specific Integrated Circuits (ASICs)) to realize the logic gate patterns. Regarding a software-based implementation, the algorithm code is generally stored in memory, such as memory 124, which can be implemented by controller 120.

[0032] The USM 100, as described above, is also shown to include a current or voltage measurement circuit 200, an RF unit 148, and a battery 178 that provides power to the corresponding active components of the USM 100 that require power. (The following description...) Figure 2 An exemplary current or voltage measurement circuit 200 is shown. An RF unit 148 is coupled to an antenna 149 external to the housing 108, which enables the USM 100 to communicate over the air with one or more remote locations, typically for communication with a control room. Figure 1A The diagram also shows a human-machine interface (HMI) 126 coupled to the controller 120. This HMI may include a keyboard and display for use by an operator or technician, if desired. The operator or technician can use the HMI 126 to adjust the operating parameters of the USM 100.

[0033] Figure 1B This is a block diagram depicting an exemplary medical ultrasound imaging system 150 for health monitoring. The probe 190 shown includes at least one ultrasound transducer 190a composed of an array of piezoelectric elements, each piezoelectric element emitting focused energy into the body and receiving the resulting reflection. In addition to ultrasound used for medical imaging, only one ultrasound transducer may exist in the NDT system, which is composed of, for example... Figure 1B The multiplexer or T / R switch shown as 152 is controlled to function as an ultrasound transmitter at a first time point, and then changed at a second time point to subsequently function as an ultrasound receiver.

[0034] By emitting acoustic energy into the body and receiving and processing the reflected sound, phase array ultrasound systems can generate images of internal organs and structures, map blood flow and tissue motion, and provide accurate blood velocity information. Conventionally, the large number of high-performance phase array transmitters and receivers required to implement these medical imaging systems results in large and expensive implementations. Recently, advancements in integration have allowed system designers to migrate to smaller, less expensive, and more portable ultrasound imaging system solutions with performance approaching that of these larger systems.

[0035] Although the medical ultrasound imaging system 150 is shown as having a single ultrasound transducer 160a, typical ultrasound imaging systems use multiple ultrasound transducers configured for specific diagnostic applications. Each ultrasound transducer includes an array of piezoelectric transducers (such as those including PZT) that emit focused acoustic energy into the body and receive the resulting acoustic reflections. As is known in the art, each piezoelectric element can be connected to other components in the medical ultrasound imaging system 150 using a thin (small diameter) coaxial cable. A typical ultrasound transducer 190a for the medical ultrasound imaging system 150 has 32 to up to 512 piezoelectric elements and typically operates at frequencies from 1 MHz to 15 MHz. Most medical ultrasound imaging systems provide two to up to four switchable connectors to allow clinicians to easily switch between various piezoelectric elements for each different type of examination.

[0036] A typical phase array ultrasound system will have 32 to up to 256 ultrasound transmitters and receivers. In most cases, the ultrasound system will have fewer transmitters and receivers than the number of available piezoelectric elements. In these cases, a high-voltage switch located in the ultrasound transducer or system acts as a multiplexer to connect specific transducer elements to specific transmitter / receiver (Tx / Rx) pairs. In this way, the medical ultrasound imaging system 150 can dynamically change the active transducer aperture on the available array of transducer elements provided by the ultrasound transducer 190a.

[0037] A Tx path 155 is shown, which includes a T / R switch 152 driven by a multiplexer shown as a high-voltage (HV) multiplexer 153. A time gain compensation (TCG) path 165 is present, which includes a variable gain amplifier (VGA) 166 coupled to an anti-aliasing filter (AAF) 167, which in turn is coupled to an ADC shown as a high-speed ADC 168. A continuous wave Doppler (CWD) path 170 is present, which includes a low-noise amplifier (LNA) 171 between the T / R switch 152 and the VGA 166, an I / O processing 172 with an input coupled to the output of the LNA 171, and an output to an ADC, shown as a first precision ADC 173a and a second precision ADC 173b with corresponding outputs coupled to a Doppler processing block 185. The medical ultrasound imaging system 150 is shown as including other blocks, including a beamformer controller 179 and a digital beamformer 180 that receives the output signal of a high-speed ADC 168, which is typically routed via a high-speed low-voltage differential signaling (LVDS) serial interface.

[0038] In spectrum processing, the beamformed digital signal is digitally filtered, mixed to baseband at the transmit frequency using a quadrature local oscillator (LO), and then sampled at the transmit pulse repetition frequency (PRF). A Fast Fourier Transform (FFT) is then typically used to generate an output spectrum representing the signal's velocity content. The signal amplitude for each bin of the FFT output is calculated and compressed to optimize the available dynamic range for a visible display. The signal amplitude is then typically displayed relative to time on a display (not shown).

[0039] The disclosed USM (such as Figure 1A The USM 100 shown) and other ultrasound-based systems (such as Figure 1B The illustrated medical ultrasound imaging system 150 and the disclosed method are capable of classifying all three individual transducer problems identified herein as significant potential issues for the ultrasound transducer. The primary objective is to identify aging phenomena of the piezoelectric element at an early stage, enabling the generation of alerts to customers / users (e.g., in the case of USM, to gas facility companies or service providers of ultrasound systems), which allows for planning or remedial action for the ultrasound transducer. For example, once the problem is alerted, the ultrasound transducer can be replaced while remaining on-site for the expected period with minimal downtime impact.

[0040] When piezoelectric elements, such as USM including PZT, have aged, it is recognized that the impedance of the piezoelectric element can change, which will affect the impedance applied to the piezoelectric element. Figure 1A The diagram shows the drive current for the drive circuit of Tx 111, where impedance typically increases with aging, reducing the drive current. In cases where the piezoelectric element has broken wires or loose solder to its electrodes, or a broken piezoelectric crystal, this can cause the current drawn from Tx 111 to change to a minimum, or no current at all in the open circuit condition. This can indicate canned ultrasonic transducers (such as those hidden by encapsulation materials) that cannot be externally inspected. Figure 1A Check if the package layer 173 shown is connected correctly.

[0041] The second objective is to identify the cause of abnormal attenuation of the received ultrasonic signal, which can affect the measurement accuracy of ultrasonic transducer-based systems because reduced signal amplitude decreases the signal-to-noise ratio (SNR) of the received signal. As mentioned above, the received signal amplitude can be evaluated to diagnose this problem. The third objective is to prevent short-circuit failures caused by improper wiring (such as short-impedance or low-impedance wire connections between the two terminals on the piezoelectric element used for the transducer cable), internal short circuits in the piezoelectric element, or improper soldering of wiring connectors on the electrodes of the piezoelectric element. When powered by battery 178, short circuits or associated low-resistance conditions will cause battery 178 to discharge rapidly, resulting in a significantly shorter lifespan than expected.

[0042] Figure 2 This is a block diagram representation of corresponding components of an exemplary current or voltage measurement circuit according to an exemplary aspect, shown as follows: Figure 1A Box 200 in the diagram is now shown as a current or voltage measurement circuit 200' coupled to a portion of the Tx circuit. The pulse is shown as being generated by a DC / DC boost power converter 220 coupled to one or more nodes of the Tx circuit, wherein the DC / DC boost power converter 220 receives a DC power source (not shown in the diagram for simplicity). Figure 2 (shown in the diagram), and receives a suitable modulation signal (such as a pulse width modulation (PWM) signal) at its input to enable control of the pulse width of the output. The current or voltage measurement circuit 200' includes a sensing resistor 225 connected in series between the DC / DC power converter 220 and the power switch 230. The power switch 230 is shown as coupled to a pulse driver 235, which is coupled to a MUX 115, which is then coupled to a piezoelectric element of an ultrasonic transducer shown as T1 or T2.

[0043] The current or voltage measurement circuit 200 includes a current-sensing amplifier 201 connected across a sensing resistor 225. This current-sensing amplifier amplifies a current waveform coupled to an electrical isolator 202, which is coupled to an amplifier 203, which can be configured as a voltage follower. Amplifier 203 is shown as an input connected to a high-speed ADC 168, which may have two channels. One channel can be used for ultrasonically received signals, such as determining flow velocity, and the other channel can be used for, as disclosed, aspects including analyzing the waveform of pulse signals. The output of the high-speed ADC 168 is shown as an input connected to a central processing unit (CPU) 205, which may include an MCU. The CPU 205 has an associated memory shown as MEM 206.

[0044] The high-speed ADC 168 typically provides a sampling rate of at least 4 million samples per second (SPS). Current or voltage measurement circuitry 200 captures the drive current waveform of the piezoelectric element of the ultrasonic transducer applied to the transmitter side. Also shown as part of the current or voltage measurement circuitry 200 is a comparator 208 providing short-circuit protection. The reference voltage for the comparison operation performed by comparator 208 is fixed and may be contained in memory within the block shown as comparator 208. Comparator 208, upon triggering, may send a power-off signal configured to turn off the DC / DC boost converter 220, and also a power-off signal to turn off the power switch 230.

[0045] This sensed pulse signal can be processed by the CPU 205 using its MEM 206, or by another computing device using a pattern checking algorithm that can utilize a reference waveform (such as one obtained after the USM has undergone functional testing in the factory where it is manufactured) to check the integrity of the current waveform signal. The CPU 205 will typically collect more than one current waveform and check the corresponding current waveform against the reference waveform.

[0046] Figure 3 Three exemplary pulse signal waveforms are shown, including a waveform shown as a high amplitude limit, a waveform shown as a normal amplitude, and a waveform shown as a low amplitude limit. If the amplitude of the sensed pulse signal is outside the high and low amplitude limits, this indicates that the impedance of the transmitting piezoelectric element is abnormal, and therefore the risk of being in the aforementioned failure modes / problems (including continuing the aging process that could lead to later system failure) is increased.

[0047] If the sensed pulse signal waveform is determined to be normal, the receiver signal level may be relatively small compared to the expected receiver signal level. A primary cause of a relatively small receiver signal level could be a coating or viscous fluid contaminant layer deposited on the matching layer of the receiver-side piezoelectric transducer, which, as described above, is exposed to the fluid flowing in the pipe. In this case, an alarm may be generated, which may include a wired or wireless signal. Wired connections may include the RS 485 communication standard used with Supervisory Control and Data Acquisition (SCADA) systems. The alarm may be sent to the gas facility company or supplier's service center as a reminder to schedule preventative maintenance involving cleaning the ultrasonic transducer, especially for relatively small-diameter integrated flow tubes (e.g., those included in conventional sampling USMs) used to measure the gas flow rate through the USM. The cleaning process is typically implemented manually, where the ultrasonic transducer or USM is removed from the pipe section and then cleaned. Generally, gas pipes and flow meters require maintenance every two years, including pipe cleaning, according to global regulations.

[0048] The disclosed aspects will help monitor the health of ultrasound-based systems such as the USM and can provide alerts, as described above, to remind customers to clean the USM, such as by using antenna 149 to wirelessly transmit the alert. Figure 1A The alarm sent by the RF unit 148 shown. Regarding the third issue mentioned above, the disclosed current or voltage monitoring circuit can also trigger an overcurrent protection warning, enabling remedial measures to improve the reliability of the USM.

[0049] Figure 4This is a flowchart illustrating the steps of an exemplary method 400 for monitoring an ultrasonic transducer in an ultrasound-based system. Step 401 includes providing an ultrasonic transducer including at least a first piezoelectric element and a controller, the first piezoelectric element having a matching layer electrically connected to at least a transmitter thereon, and the controller having an associated memory coupled to the transmitter. Step 402 includes the transmitter driving the first piezoelectric element with a pulsed electrical signal (pulse signal) to generate an emitted ultrasonic signal. Step 403 includes sampling the pulse signal. Step 404 includes, in response to receiving the emitted ultrasonic signal, the ultrasonic transducer or a second ultrasonic transducer spaced apart from the ultrasonic transducer generating a received signal, the second ultrasonic transducer including at least a second piezoelectric element, the second piezoelectric element also having a matching layer thereon.

[0050] Step 405 includes comparing the amplitude of at least the pulse signal with at least one predetermined limit, wherein when the pulse signal exceeds the predetermined limit, the impedance of the first piezoelectric element is determined to be abnormal. Step 406 includes, when the pulse signal is determined to be within the predetermined limit, comparing the amplitude of at least the received signal with a lower amplitude limit, wherein when the amplitude of the received signal is at or below the lower amplitude limit, it is determined that the ultrasonic transducer or the second ultrasonic transducer requires a cleaning operation of the matching layer.

[0051] While various disclosed embodiments have been described above, it should be understood that they are presented by way of example only and not limitation. Many changes may be made to the subject matter disclosed herein without departing from the spirit or scope of this disclosure. Furthermore, while a particular feature may be disclosed only with respect to one of several implementations, such feature may be combined with one or more other features of other implementations as may be desired or advantageous for any given or particular application.

Claims

1. A method for monitoring an ultrasonic transducer of an ultrasound-based system (100), the ultrasonic transducer comprising at least a first piezoelectric element having a matching layer (140) thereon electrically connected to at least a transmitter (111), wherein the ultrasound-based system (100) further comprises a controller (120) having an associated memory (124) coupled to the transmitter, the method comprising: The transmitter uses a pulse signal to drive the first piezoelectric element to generate an ultrasonic signal; The pulse signal is sampled; In response to receiving the transmitted ultrasonic signal, the ultrasonic transducer or a second ultrasonic transducer spaced apart from the ultrasonic transducer generates a received signal, the second ultrasonic transducer including at least a second piezoelectric element, the second piezoelectric element also having a matching layer thereon, and The amplitude of at least the pulse signal is compared with a high amplitude limit and a low amplitude limit, wherein when the amplitude of the pulse signal exceeds the high amplitude limit and the low amplitude limit, the impedance of the first piezoelectric element is determined to be abnormal; When the pulse signal is determined to be within a low amplitude limit and a high amplitude limit, the amplitude of at least the received signal is compared with the low amplitude limit, wherein when the amplitude of the received signal is at or below the low amplitude limit, it is determined that the ultrasonic transducer or the second ultrasonic transducer requires a cleaning operation of the matching layer.

2. The method of claim 1, wherein the ultrasound-based system (100) comprises the ultrasound transducer as a single ultrasound transducer, and wherein the ultrasound-based system further comprises a duplexer positioned between the controller (120) and the single ultrasound transducer, the duplexer being used to control the ultrasound transducer to switch between transmitting and receiving.

3. The method of claim 1, wherein the pulse signal comprises a pulse current or a pulse voltage, and wherein the transmitter further comprises a current or voltage measurement circuit (200) for sampling the pulse current or the pulse voltage.

4. The method of claim 1, further comprising generating and transmitting an alarm in response to determining that the impedance of the first piezoelectric element is abnormal or determining that the ultrasonic transducer or the second ultrasonic transducer requires the cleaning operation.

5. The method of claim 1, wherein the ultrasound-based system (100) comprises an ultrasonic flow meter, and wherein the ultrasonic flow meter is mounted on a pipe section.

6. An ultrasound-based system (100), the ultrasound-based system (100) comprising: Transmitter (111) and receiver (112); An ultrasonic transducer comprising at least one piezoelectric element having thereon a matching layer (140) electrically connected to at least the transmitter. The controller (120) has an associated memory (124) coupled to the transmitter. The transmitter drives the piezoelectric element with a pulse signal including pulse current or pulse voltage; A current or voltage measurement circuit (200) is coupled to at least one node in the transmitter for sampling the pulse signal; In response to the pulse signal, the piezoelectric element emits an ultrasonic signal; The controller has an associated memory that stores code for implementing an algorithm for an ultrasonic transducer monitoring method, the monitoring method comprising: The amplitude of the pulse signal sensed by the current or voltage measurement circuit is compared with a high amplitude limit and a low amplitude limit by sampling the pulse signal, wherein when the amplitude of the pulse signal is determined to exceed the high amplitude limit and the low amplitude limit, the impedance of the piezoelectric element is determined to be abnormal. When the pulse signal is determined to be within a low amplitude limit and a high amplitude limit, the amplitude of at least the received signal is compared with the low amplitude limit, wherein when the amplitude of the received signal is at or below the low amplitude limit, it is determined that the matching layer of the ultrasonic transducer requires a cleaning operation.

7. The ultrasound-based system (100) of claim 6, wherein the ultrasound-based system comprises the ultrasound transducer as a single ultrasound transducer, and wherein the ultrasound-based system further comprises a duplexer positioned between the controller (120) and the single ultrasound transducer, the duplexer being used to control the ultrasound transducer to switch between transmitting and receiving.

8. The ultrasound-based system (100) of claim 6, the monitoring method further comprising generating and transmitting an alarm in response to determining that the impedance of the piezoelectric element is abnormal or that the matching layer (140) requires the cleaning operation.

9. An ultrasonic flow meter USM (100), the ultrasonic flow meter USM comprising: An outer casing (108) having attachment features for attaching to a pipe section suitable for allowing fluid to flow therein; A first ultrasonic transducer and at least a second ultrasonic transducer, the first ultrasonic transducer including at least a first piezoelectric element, the second ultrasonic transducer including at least a second piezoelectric element, the first piezoelectric element and the second piezoelectric element each having a matching layer (140) thereon. A transmitter (111) and a receiver (112), the transmitter and the receiver being coupled to the first ultrasonic transducer and the second ultrasonic transducer by a multiplexer; Controller (120), the controller having an associated memory (124) coupled to the transmitter; A transmitter, the transmitter being used to drive the first ultrasonic transducer or the second ultrasonic transducer with a pulse signal; A current or voltage measurement circuit (200) is coupled to at least one node in the transmitter for sampling the pulse signal; In response to the pulse signal, the first ultrasonic transducer or the second ultrasonic transducer is used to transmit an ultrasonic signal; The controller has an associated memory that stores code for implementing an algorithm for an ultrasonic transducer monitoring method, the monitoring method comprising: By sampling the pulse signal, at least the amplitude of the pulse signal sensed by the current or voltage measurement circuit is compared with a high amplitude limit and a low amplitude limit, wherein when the amplitude of the pulse signal is determined to exceed the high amplitude limit and the low amplitude limit, the impedance of the first piezoelectric element or the second piezoelectric element is determined to be abnormal. When the pulse signal is determined to be within a low amplitude limit and a high amplitude limit, the amplitude of at least the received signal is compared with the low amplitude limit, wherein when the amplitude of the received signal is at or below the low amplitude limit, it is determined that the matching layer of the first ultrasonic transducer or the second ultrasonic transducer requires a cleaning operation.

10. The ultrasonic flow meter USM (100) of claim 9, wherein the monitoring method further comprises generating and transmitting an alarm in response to determining that the impedance of the first piezoelectric element or the second piezoelectric element is abnormal or determining that the matching layer (140) of the first ultrasonic transducer or the second ultrasonic transducer requires the cleaning operation.

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