EA043606B1 - IMPROVED TOF FLOWMETER WITH SOUND SIGNAL BEAM FORMATION - Google Patents

Abstract

A method and corresponding device for determining the flow velocity in a fluid pipeline are proposed. The fluid pipeline is equipped with first, second, and third ultrasonic measuring transducers, wherein the corresponding connecting lines between the measuring transducers extend outside the axis of symmetry of the fluid pipeline. The first and second measuring signals are supplied to the first ultrasonic measuring transducer and received by the second and third ultrasonic measuring transducers, respectively. The measuring signals comprise a corresponding time-reversed portion of the response signal. The corresponding first and second response signals are measured, and the flow velocity is obtained from at least one of the first and second response signals.

Description

The present invention relates to flow meters, and in particular to time-of-flight ultrasonic flow meters.

Various types of flow meters are currently used to measure the volumetric flow rate of a fluid such as a liquid or gas through a pipe. Ultrasonic flow meters are either Doppler flow meters, which use the acoustic Doppler effect, or time-of-flight flow meters, sometimes also called transmitted signal flow meters, which use the difference in signal propagation time caused by the relative motion of the source and the medium. The transit time is also called the time of flight or transit time.

A time-of-flight ultrasonic flow meter measures the difference in transit time between ultrasonic pulses traveling in the direction of and against the flow. Ultrasonic flow meters are available as in-line flow meters, also known as immersion or submersible flow meters, or as clamp-on flow meters, also known as non-immersible flow meters. Other types of flow meters include venturi, weir, radar, coriolis, differential pressure, magnetic inductive, and other flow meter types.

In the presence of non-standard flow profiles or open channels, more than one propagation path may be necessary to determine the average flow velocity. Among other things, multi-path propagation procedures are described in hydrometric standards such as IEC 41 or EN ISO 6416. As an additional application, ultrasonic flow meters are also used to determine flow profiles, for example with the Acoustic Doppler Current Meter (ADC). ADC is also suitable for measuring water velocity and discharge in rivers and open waters.

The object of the present invention is to provide an improved time-of-flight flowmeter and a corresponding computer-implemented method for measuring the average flow velocity or flow profile of a fluid in general and in particular for liquids such as water or for gases.

In the flow measuring device according to the present invention, sound measuring transducers, for example in the form of piezoelectric elements, also known as piezoelectric measuring transducers, are used to generate and receive a test signal and a measuring signal.

Alternative sound transmitters include lasers that vibrate a metal membrane or other light-absorbing surface, or electrodynamic loudspeakers. Pressure waves can also be generated in other ways. The receiving side can also be represented by other means that differ from piezoelectric transducers, but detect ultrasonic waves.

Although the term piezoelectric transducer is often used in this description, it also refers to other sound wave transducers that produce or detect ultrasonic waves.

The measurement signal according to the present invention can be formed by a matched filter. If a pulse with a sharp peak is used as a test or verification signal, the received signal at the measuring transducer is the impulse response of the pipeline or channel of the fluid. According to the present invention, an inverted version of the impulse response with respect to time is sent back through the same channel as a measurement signal either in the opposite direction or in the same direction. This results in a signal with a peak at the initial stage, where the original source was, or a signal with a peak as at the initial receiver, respectively.

Inversion with respect to time can be achieved in several ways. When using analog means to record the response signal, the recorded response signal can be played back in reverse. When using digital means to record discrete values of the response signal, the order of the recorded discrete values is reversed to obtain an inverted signal. This can be achieved by inverting the time stamp values of each recorded discrete value by multiplying the corresponding time value by (-1). When playing back according to the ascending order of the time stamp values, the recorded discrete values are played back in reverse order. In other words, the inverted response signal is the recorded response signal, but played back in reverse.

The ultrasonic flow meter according to the present invention provides a focusing property by using the above-mentioned inverted signal or a similarly shaped signal for the ultrasonic flow meter to form a response signal that is concentrated both in space and in time. This, in turn, leads to a higher amplitude at the receiving piezoelectric element and a better signal-to-noise ratio.

Thanks to the ultrasonic flowmeter according to the present invention, the focusing and beam forming properties can be obtained under very ordinary conditions. For example, the focusing property is obtained even when only one ultrasonic transmitter is activated and even when the inverted signal is reduced to a signal that is only roughly digitized in the amplitude range, with sufficient time resolution of the inverted signal. In addition, the flowmeter according to the present invention can be used with clamp-on measuring transducers that are easy to place on a pipe and for which no changes to the pipe are required.

In the ultrasonic flowmeter according to the present invention, the technical features that ensure good connection and directionality of the clamp-on measuring transducers, and to reduce scattering, may not be necessary, or, on the contrary, their exclusion may even improve the beam forming characteristic. In order to ensure increased scattering, a connection material can be selected that is adapted to the refractive index of the liquid or the measuring transducers, and measuring transducer connections that provide more shear waves can be used.

Preferably, the frequency of the sound waves used in the flowmeter according to the present invention is from >20 kHz to 2 MHz, which corresponds to an oscillation period of 0.5 microseconds (μs), but can even be up to 800 MHz. In many cases, ultrasonic flowmeters operate well above the hearing threshold with frequencies of several hundred kHz or higher. The frequency of time-of-flight ultrasonic flowmeters is typically in the kHz or MHz range.

According to one aspect of the present invention, a computer-executable method for determining the flow rate of a fluid in a pipeline or fluid channel, in particular a pipe or tube, using a time-of-flight ultrasonic flow meter is described. In a preferred embodiment, the expression computer-executable refers to execution on electronic components with a fine structure, such as microprocessors, ASIC chips, FPGAs, etc., which can be used in portable or compact stationary digital signal processing devices that are typically smaller in size than workstations or mainframe computers and which can be placed at a desired location along a fluid pipe.

In the following, the terms channel, pipeline, passage, etc. are used as synonyms. The subject of the invention can be applied to all types of pipelines for fluid media, regardless of their respective shape and regardless of whether they are open or closed. The subject of the invention can also be applied to all types of fluid media or gases, regardless of whether they are gases or liquids, or a mixture thereof.

The term computer is often used throughout the invention. Although a computer refers to devices such as a laptop or desktop computer, the signal transmission and reception can also be performed by microcontrollers, ASIC chips, FPGAs, etc.

In addition, the connecting line between the measuring transducers can be offset relative to the center of the fluid pipeline in order to obtain the flow velocity in a predetermined layer, and more than one pair of measuring transducers can be provided. In addition, the measuring signal can be provided by more than one measuring transducer, and/or the response signal to the measuring signal can be measured by more than one measuring transducer.

The energy E of the signal s(t) in a time interval can be determined based on the expression

E = £dt |s(t)| ² or its discrete version e = ZIUMOI ² , where the time interval is given as [T1, T2] or [m*At, n*At], respectively.

The leading part of the measurement signal can significantly influence the resulting signal, which has peaks in space and time.

In some specific embodiments, the measurement signal or response signal may be provided by an amplitude-modulated oscillatory signal that is digitized with respect to the amplitude, for example, with a resolution of 1 to 12 bits. This may provide advantages in terms of computation speed and memory capacity, and may even result in an increased signal peak. In particular, the data presented in the graphical materials of the present invention were obtained with a resolution of 12 bits, with the exception of Figs. 30-35, which were obtained with a coarser resolution than 12 bits.

According to a further embodiment, the measuring signal that is fed to the measuring transducer may comprise an oscillatory signal that is modulated according to a 0-1 modulation, either providing a predetermined amplitude or not providing any amplitude, or, in other words, providing zero amplitude.

According to an additional aspect, a device for measuring the flow rate in a time-of-flight ultrasonic flow meter is disclosed. The device comprises a first connector for connecting a first piezoelectric element, a second connector for connecting a second piezoelectric element, an optional digital-to-analog converter (DAC) that is connected to the first

- 2 043606 connector, and an optional analog-to-digital converter (ADC), which is connected to the second connector.

In addition, the device comprises a machine-readable memory device, an electronic timer or oscillation generator, a transmitting unit for sending a pulse signal to the first connector and a receiving unit for receiving a response signal to the pulse signal from the second connector.

The terms flow velocity, flow speed and flow rate are used synonymously in this application.

Although the device may be provided as an analog device without an analog-to-digital and digital-to-analog converter and without a machine-readable memory unit, it is also possible to provide the device or parts thereof using a digital computing system.

In particular, various signal processing units, such as a speed processing unit, a selection unit, and an inverting unit, may be provided in whole or in part using a specialized electronic component or a program memory with a set of machine-readable instructions. Similarly, the measuring signal generator and the pulse signal generator of the transmitting unit may be provided in whole or in part using a specialized electronic component, which may contain a set of machine-readable instructions.

According to an additional embodiment, the device comprises a direct digital signal synthesizer (DDS), which comprises the above-mentioned ADC. The DDS comprises a frequency control register, a reference oscillator, a oscillator with numerical program control and a low-pass reconstruction filter. In addition, the ADC is configured to be connected to the first and to the second connector via a low-pass reconstruction filter.

In addition, according to the present invention, a flow measurement device is disclosed with a first piezoelectric measuring transducer, which is connected to a first connector, and with a second ultrasonic measuring transducer, such as a piezoelectric measuring transducer, which is connected to a second connector. In particular, ultrasonic measuring transducers, such as piezoelectric measuring transducers, can be provided with fastening means, such as a clamping mechanism, for fastening them to a pipe.

In addition, according to the present invention, a flow measurement device with a pipe part is disclosed. A first ultrasonic measuring transducer, such as a piezoelectric measuring transducer, is mounted on the pipe part at a first location, and a second ultrasonic measuring transducer, such as a piezoelectric measuring transducer, is mounted on the pipe part at a second location. In particular, the measuring transducers can be fixed on the pipe part. Providing the device with a pipe part can provide advantages when the device is pre-adjusted with respect to the pipe part.

The device can be made compact and portable. The portable device according to the present invention, which is equipped with measuring transducers designed with the possibility of installation on the surface, such as clamp-on measuring transducers, can be used to check the pipe in any accessible place. In general, the device can be fixed or portable. Preferably, the device is compact enough to be placed in the required place and sufficiently protected from environmental conditions, such as humidity, heat and corrosive substances.

Moreover, according to the present invention, a machine-readable code is disclosed for performing the method of measuring flow according to the present invention, wherein the machine-readable memory device comprises the machine-readable code and a specialized electronic component that is configured to perform the steps of the method according to the present invention.

In particular, the specialized electronic component can be provided with an electronic component containing the above-mentioned machine-readable memory device, such as EPROM, EEPROM, flash memory, etc. According to other embodiments, the specialized electronic component is provided with a component with a hardware-implemented or with a circuit providing various configurations, such as an application-specific integrated circuit (ASIC) or a field-programmable logic array (FPGA).

In a further embodiment, the specialized electronic component according to the present invention is provided by a plurality of interconnected electronic components, for example an FPGA, which is connected to a suitably programmed EPROM in a multi-channel device. Further examples of the specialized electronic component are programmable integrated circuits, such as programmable logic arrays (PLA) and complex programmable logic devices (CPLD).

It is expedient to determine whether an existing testing device measures the flow velocity of a fluid in a fluid pipeline according to the present invention. For this purpose, the fluid pipeline is provided with a fluid that has a predetermined velocity relative to the fluid pipeline. A test pulse signal is fed to a first ultrasonic measuring transducer, such as a piezoelectric measuring transducer

- 3 043606 a transducer of a testing device, wherein the first piezoelectric measuring transducer is mounted on a pipeline for a fluid at a first location, followed by receiving a test signal of response to a test pulse signal at a second piezoelectric measuring transducer of the testing device, wherein the second ultrasonic measuring transducer, such as a piezoelectric measuring transducer, is mounted on the pipeline for a fluid at a second location.

In addition, the present invention discloses a computer-executable method for determining the flow rate of a fluid in a fluid pipeline using predetermined measurement signals in a device with three or more ultrasonic measuring transducers. The predetermined signals comprise a first measurement signal and a second measurement signal.

The fluid pipeline is provided with a fluid medium that has a predetermined speed relative to the fluid pipeline. In addition, the fluid pipeline is provided with a first ultrasonic measuring transducer, a second ultrasonic measuring transducer and a third ultrasonic measuring transducer. In particular, the second measuring transducer and the third measuring transducer can be located at a distance relative to the first measuring transducer and relative to the longitudinal direction of the pipeline.

The measuring transducers are arranged so that the corresponding connection lines between the first ultrasonic measuring transducer, the second ultrasonic measuring transducer and the third ultrasonic measuring transducer extend beyond the axis of symmetry of the fluid medium pipeline. In particular, the connection line can be shifted by 5% or more, or by 10% or more relative to the average diameter of the pipeline or relative to the average radius of the pipeline.

For example, the average radius of a pipeline can be determined relative to a reference point at

J |f | or p—Jo t axis of symmetry as and or as N etc.

The first predetermined measuring signal is supplied to the first ultrasonic measuring transducer, and the first response signal of the first predetermined measuring signal received at the second ultrasonic measuring transducer is measured, for example, by determining the voltage generated by the second ultrasonic measuring transducer.

Similarly, the second predetermined measuring signal is supplied to the first ultrasonic measuring transducer, and the second response signal of the second predetermined measuring signal received at the third ultrasonic measuring transducer is measured.

The first predetermined measuring signal and the second predetermined measuring signal respectively comprise a time-reversed portion of the response signal to the corresponding pulse signal or a signal obtained from it.

In particular, the corresponding measuring signal can be generated from a pulse signal that is transmitted between the same pair of measuring transducers as the measuring signal. The generation of the measuring signal can be performed by means of an actual measurement, by means of simulation, or by means of a combination of both.

The measuring signal can be sent in the same direction or in the opposite direction compared to the pulse signal from which it is generated. In particular, if the fluid is moved relative to the pipeline during the calibration process by which the measuring signal is generated from the pulse signal, it may be advantageous for reasons of stability to transmit the measuring signal in the same direction as the pulse signal.

In other words, in the measurement step, the sequence of the sending measuring transducer and the receiving measuring transducer may be the same as in the previous calibration step for generating the measuring signal, or, alternatively, it may be reversed, using the previously sending measuring transducer as the receiving measuring transducer and the previously receiving measuring transducer as the sending measuring transducer.

Typically, the first measuring signal is adapted to a channel or transmission path that is different from the transmission channel of the second measuring signal. Therefore, the first measuring signal and the second measuring signal are usually different from each other. In addition, the measuring signal obtained by sending a pulse signal from the first measuring transducer to the second measuring transducer is usually different from the measuring signal obtained by sending a pulse signal in the opposite direction from the second measuring transducer to the first measuring transducer.

- 4 043606

Typically, the propagation of a pressure signal between a sending and receiving transducer includes not only forward propagation, but may also include one or more reflections on the pipe wall and/or scattering processes in the pipe wall.

In particular, the above-mentioned method can be used in the measurement of flow rate by time of flight (TOF). For the TOF measurement, the steps of supplying a first measuring signal and measuring a corresponding response signal and supplying a second measuring signal and measuring a corresponding response signal are repeated in the reverse direction to obtain the corresponding first response signal with a reverse direction and the second response signal with a reverse direction.

As explained above, performing a measurement in the reverse direction refers to implementing the measurement steps so that the roles of the corresponding measuring transducers are reversed, or in other words, so that the previously sending measuring transducer is used as the receiving measuring transducer, and the previously receiving measuring transducer is used as the sending measuring transducer.

Thus, if the first measurement involves sending a measuring signal in the direction of the fluid flow in the sense that the measuring signal has a velocity component in the direction of the fluid flow, then the corresponding measurement in the opposite direction involves sending a measuring signal against the direction of the fluid flow.

The first response signal and the second response signal to the corresponding first measurement signal and the second measurement signal are used to obtain one or more flow rates of the fluid. In particular, the first response signal can be used to determine the flow rate in the fluid layer that contains the connection line between the first measurement transducer and the second measurement transducer, and the second response signal can be used to determine the flow rate in the fluid layer that contains the connection line between the first measurement transducer and the third measurement transducer.

According to another embodiment, which is applicable for measuring the time of flight, the first predetermined measuring signal with a reverse direction is supplied to the second ultrasonic measuring transducer, and the first response signal with a reverse direction to the first measuring signal with a reverse direction is measured on the second ultrasonic measuring transducer.

Similarly, the second measuring signal with the reverse direction is supplied to the third ultrasonic measuring transducer, and the second response signal with the reverse direction of the second predetermined measuring signal received at the first ultrasonic measuring transducer is measured.

The first measuring signal with a reverse direction and the second measuring signal with a reverse direction respectively contain a time-reversed part of the response signal to the corresponding pulse signal or a signal obtained from it. The corresponding pulse signal refers to a pulse signal that is transmitted between the same pair of measuring transducers as the corresponding measuring signal.

The fluid flow velocity is obtained from at least one of the first response signal, the first response signal with a reverse direction, the second response signal and the second response signal with a reverse direction. In particular, the first response signal and the first response signal with a reverse direction can be used to obtain the flow velocity using the time-of-flight method. Similarly, the second response signal and the second response signal with a reverse direction can be used to obtain the flow velocity using the time-of-flight method.

In another embodiment, in which a measuring signal is also used, passing from the second measuring transducer to the third measuring transducer in the above-mentioned device of three measuring transducers, the measurement further includes the following steps.

The third measuring signal is fed to the second ultrasonic measuring transducer, and the third response signal to the second measuring signal is measured on the third ultrasonic measuring transducer.

Similar to the above embodiments, the third predetermined measurement signal comprises a time-reversed portion of a response signal to the corresponding pulse signal or a signal obtained therefrom.

At least one flow rate of the fluid is obtained from the third response signal. In order to determine at least one flow rate, the first response signal, the first response signal with a reverse direction, the second response signal and the second response signal with a reverse direction can also be used.

In another embodiment, which is applicable for determining the flow velocity in a layer of fluid between the second measuring transducer and the third measuring transducer using the time-of-flight method, the method further includes the following steps.

The third measuring signal with the reverse direction is fed to the third ultrasonic measuring transducer, and the third response signal with the reverse direction is measured to the third measuring signal with the reverse direction received at the second ultrasonic measuring transducer.

Similar to the above embodiments, the third measuring signal with a reverse direction comprises a time-reversed portion of the response signal to the corresponding pulse signal or a signal obtained from it.

At least one flow rate of the fluid is obtained from the third response signal and the third response signal with a reverse direction. In order to determine at least one flow rate, the first response signal, the first response signal with a reverse direction, the second response signal and the second response signal with a reverse direction can also be used.

According to an additional computer-executable method, which is applicable for determining a flow rate in a fluid pipeline using a device of at least two clamp-on measuring transducers, the fluid pipeline is provided with a fluid that has a predetermined velocity relative to the fluid pipeline.

In addition, the pipeline for a fluid medium is provided with a first ultrasonic clamp-on measuring transducer and a second ultrasonic clamp-on measuring transducer. Preferably, the second ultrasonic clamp-on measuring transducer is offset relative to the first ultrasonic clamp-on measuring transducer in the longitudinal direction of the pipeline.

The clamp-on measuring transducers are arranged so that the direct connection line between the first ultrasonic clamp-on measuring transducer and the second ultrasonic clamp-on measuring transducer passes outside the axis of symmetry of the fluid medium pipeline. In particular, the connection line can be shifted relative to the axis of symmetry by 5% or more, or by 10% or more relative to the average diameter or relative to the average radius of the pipeline.

A predetermined measuring signal is supplied to the first ultrasonic clamp-on measuring transducer, and a response signal of the measuring signal received at the second ultrasonic clamp-on measuring transducer is measured.

Similar to the above embodiment, the predetermined measuring signal comprises a time-reversed portion of the response signal to the corresponding pulse signal or a signal obtained from it. The flow rate of the fluid is obtained from the response signal.

Like the above embodiments, the measuring step may also include sending measuring signals in the reverse direction. In particular, the method may include feeding a predetermined measuring signal with a reverse direction to the second ultrasonic clamp-on measuring transducer and measuring a response signal with a reverse direction to the measuring signal with a reverse direction on the second ultrasonic clamp-on measuring transducer.

Similar to the above embodiment, the measuring signal with reverse direction comprises a time-reversed portion of the response signal to the corresponding pulse signal or a signal obtained from it. The flow velocity of the fluid is obtained from the response signal and from the response signal with reverse direction, in particular using the time-of-flight method.

The measuring methods for the above-mentioned device of at least three ultrasonic measuring transducers, which can be provided as immersible measuring transducers or as clamp-on measuring transducers, are similarly also applicable to the corresponding devices of clamp-on measuring transducers.

Clamp-on transducers can provide special advantages in the context of focusing the sound signal at a specific location on the pipeline, also known as beamforming. By using the interaction with the pipeline and, optionally, also with coupling elements, the sound waves of clamp-on transducers can be spread over a wider angle or in more directions than immersion transducers. Coupling elements allow the sound waves to be directed according to Snell's law, but also help generate more modes and dispersion.

The time inversion of the present invention can then be used to generate a measurement signal that adds the various signal components traveling along different paths through superposition, and thus results in a higher signal amplitude at a particular location in the pipeline where the receiving measurement transducer may be located.

The modifications mentioned below relating to multiple measurements and the digitalization step in generating the measurement signal can be applied to all measuring transducer devices according to the present invention.

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In the above-mentioned embodiments, the steps of supplying a pulse signal and receiving a corresponding response signal are repeated a plurality of times and a plurality of response signals are obtained. In particular, the multiple measurements can relate to a given combination of two measuring transducers. A corresponding measurement signal, such as a first and a second measurement signal, is then obtained from the average value of the received response signals.

In particular, obtaining the corresponding measuring signal in the above-mentioned embodiments may include digitizing the corresponding response signal or a signal obtained from it with respect to the amplitude. According to one embodiment, the steps of changing the bit resolution of the corresponding measuring signal and measuring the response signal to this measuring signal are repeated until a measuring signal is found that generates a response signal with the largest maximum amplitude. The measuring signal with the corresponding bit resolution is then selected as the measuring signal.

According to one specific embodiment, the bit resolution of the digitized signal is increased to increase the amplitude of the response signal to the corresponding measurement signal, such as the first and second measurement signal. For example, the bit resolution is increased in predetermined steps and the bit resolution is selected that creates the response signal with the highest amplitude, and the corresponding representation of the measurement signal is stored in the machine-readable memory.

According to another specific embodiment, the bit resolution of the digitized signal is reduced or decreased to increase the amplitude of the response signal to the corresponding measurement signal. For example, the bit resolution is reduced in predetermined steps, the bit resolution that produces the response signal with the highest amplitude is selected, and the corresponding representation of the measurement signal is stored in the machine-readable memory.

In particular, the bit resolution of the digitized signal in terms of amplitude can be selected as a low bit resolution. For example, the low resolution can be a resolution of 1 to 8 bits, or it can be a resolution of 1 to 64 bits.

According to one specific embodiment, at least one of the response signals to the measurement signals is processed to determine a change in the thickness of the pipeline wall or to determine the characteristics of the material of the pipeline walls by determining the characteristics of the longitudinal and transverse sound wave. For example, the characteristics of the transverse and longitudinal waves can be obtained from corresponding portions of the received signal or response signal, which corresponds to different times of occurrence of the acoustic waves.

According to another embodiment, the method includes a preliminary calibration, in which the corresponding measuring signals are generated from a response signal to a pulse signal. The calibration can be performed during factory adjustment or also during operation of the method. The calibration mentioned below can be applied in a similar manner to all combinations of pairs of two measuring transducers, and the calibration can be performed in only one direction with respect to a pair of measuring transducers or in both directions with respect to a pair of measuring transducers. In the former case, one measuring signal is obtained for a pair of measuring transducers, and in the latter case, two measuring signals are obtained for a pair of measuring transducers.

During the calibration step, the fluid pipeline is provided with a fluid that is stationary relative to the fluid pipeline or that moves at a predetermined speed relative to the fluid pipeline.

The first pulse signal is supplied to the second ultrasonic measuring transducer, and the first response signal to the first pulse signal is received at the first ultrasonic measuring transducer.

Similarly, the second pulse signal is fed to the third ultrasonic measuring transducer, and the second response signal of at least one pulse signal is received at the first ultrasonic measuring transducer.

A first measuring signal is obtained from a first response signal, and a second measuring signal is obtained from a second response signal.

Obtaining the corresponding first and second measurement signals includes selecting a portion of the corresponding first and second response signals or a signal obtained from them, and reversing this portion of the signal in time.

In other words, a portion of the first response signal is selected and inverted or reversed in time, and the first measurement signal is generated using the inverted portion of the signal. Similarly, a portion of the second response signal is selected and inverted or reversed in time, and the second measurement signal is generated using the inverted portion of the signal.

The first predefined measuring signal and the second predefined measuring signal for further use. As mentioned above, the same calibration process can be used for each combination of two measuring transducers.

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Typically, calibration is also performed in the opposite direction to avoid or compensate for instabilities. Depending on whether calibration is performed under zero flow or non-zero flow conditions, it may be advantageous to provide calibration in both directions and use each of the two generated measurement signals in either direction.

In other words, if during the measurement process the first measuring transducer is a sending measuring transducer and the second measuring transducer is a receiving measuring transducer, then the measuring signal could be generated by sending a pulse signal from the first measuring transducer to the second measuring transducer or by sending a pulse signal from the second measuring transducer to the first measuring transducer.

A similar calibration process can be performed for each pair of two measuring transducers. In particular, the calibration process can be performed in a similar manner for each pair of measuring transducers of the above-mentioned device with three measuring transducers, comprising a first, second and third measuring transducer.

In the specific case of a device of two or more clamp-on measuring transducers, calibration can be performed by means of the following steps. The fluid pipeline is provided with fluid. In particular, the fluid has a predetermined velocity relative to the fluid pipeline.

A pulse signal is supplied to the first ultrasonic clamp-on measuring transducer or the second ultrasonic clamp-on measuring transducer. Then, a response signal to the pulse signal is received on the other of the two ultrasonic measuring transducers, and a measuring signal is obtained from the response signal. Similarly, a pulse signal can be supplied to the second ultrasonic clamp-on measuring transducer, and a response signal can be received on the first ultrasonic clamp-on measuring transducer.

In this case, obtaining the measuring signal includes selecting a portion of the corresponding response signal or a signal obtained from it and reversing this portion of the signal in time. The measuring signal is stored for further use during the measurement process, in particular for determining the flow rate of the fluid medium.

The pulse signal according to the present invention may refer to a single-pulse signal. In general, a pulse signal refers to a signal that has signal energy that is concentrated in a short period of time. In a particular embodiment, the pulse signal extends only for a few carrier oscillation periods, such as 10-20 oscillation periods or less.

In particular, the envelope of a pulse signal can be rectangular, but other shapes are also possible. For example, a pulse signal can correspond to a single spike or pulse, a short rectangular burst, or any other waveform such as a triangular jagged wave, a square wave, a frequency-modulated pulse, a sine wave, or a predefined noise burst such as white noise or pink noise, which is also known as 1/f noise. The calibration method works with almost any waveform of a pulse signal.

In another embodiment, the corresponding response signal is sent and received multiple times, thereby obtaining a plurality of response signals, and the corresponding measurement signal is obtained from the average value of the received response signals.

In particular, obtaining the corresponding measurement signal may include digitizing the corresponding response signal or a signal obtained from it with respect to amplitude.

As also mentioned above, the bit resolution of the digitized signal is increased to increase the amplitude of the response signal to the corresponding measurement signal. In one particular embodiment, the amplitude of the response signal to the generated measurement signal is measured at a predetermined location of the pipeline for measurement signals corresponding to different bit resolutions. The measurement signal with the highest amplitude is then selected and stored in memory for further use.

A similar procedure can also be achieved by reducing the bit resolution of the digitized signal until a response signal of the measuring signal is detected that has a high amplitude, and the corresponding measuring signal is then stored in memory for further use.

In particular, the bit resolution of the digitized signal in terms of amplitude can be selected as a low bit resolution, for example, a resolution of 1 to 10 bits.

In addition, the present invention discloses a machine-readable program code with machine-readable instructions for performing one of the above-mentioned flow measurement methods. Moreover, the present invention also discloses a machine-readable memory device with a machine-readable program code and a specialized electronic component that is used to perform the above-mentioned flow measurement method.

In addition, the present invention discloses a device for measuring the flow rate of a fluid

- 8 043606 of the medium in a pipeline having a device of three measuring transducers. The specified device is used to perform flow measurement by transit time or time of flight.

The device comprises a first connector for connecting a first ultrasonic element, a second connector for connecting a second ultrasonic element, and a third connector for connecting a third ultrasonic element.

In addition, the device comprises a transmitting unit for sending pulse signals and for sending measuring signals, a receiving unit for receiving response signals and a processing unit. The transmitting unit, the receiving unit and the processing unit are provided for receiving the first measuring signal from the first inverted signal, for receiving the second measuring signal from the second inverted signal and for storing the first measuring signal and the second measuring signal.

Similar to the above embodiments, obtaining an inverted signal includes reversing in time a portion of the response signal to a corresponding pulse signal or a signal obtained therefrom.

The processing unit, the transmitting unit and the receiving unit are used to supply a first predetermined measuring signal to the first connector and to receive a first response signal to the first measuring signal at the second connector.

In addition, the processing unit, the transmitting unit and the receiving unit are used to supply the second measuring signal to the first connector and to receive the second response signal to the second measuring signal at the third connector, and to obtain the flow rate of the fluid from at least one of the first response signal and the second response signal.

In addition, the processing unit, the transmitting unit and the receiving unit can be used to perform any of the other measurement and calibration methods described above with respect to the device with three measuring transducers, which can be submersible measuring transducers or clamp-on measuring transducers.

The signal supply may include, in particular, retrieving the stored signal from the computer memory and generating a corresponding electrical signal, which is then transmitted to the measuring transducer, typically via a cable. In addition, the processing unit is used to obtain the flow rate of the fluid medium from at least one of the first response signal and the second response signal.

In particular, the connectors, the transmitting unit, the receiving unit and the processing unit may be provided by a time-of-flight ultrasonic flow meter or a part thereof, and in particular by a portable time-of-flight ultrasonic flow meter or a part thereof.

In another aspect, the present invention discloses a device for measuring the flow rate of a fluid medium in a pipeline in the form of a device with at least two clamp-on measuring transducers. In particular, said device comprises a first connector, a first ultrasonic clamp-on measuring transducer, which is connected to the first connector. Similarly, the device comprises a second connector and a second ultrasonic clamp-on measuring transducer, which is connected to the second connector.

In addition, the device comprises a portion of a pipeline, wherein the first ultrasonic clamp-on measuring transducer is installed on the portion of the pipeline in a first location, and the second ultrasonic clamp-on measuring transducer is installed on the portion of the pipeline in a second location.

The clamp-on measuring transducers are arranged so that the corresponding connection lines between the first ultrasonic clamp-on measuring transducer and the second ultrasonic clamp-on measuring transducer pass outside the axis of symmetry of the pipeline for the fluid medium.

Similar to the above-mentioned device, the said device comprises a transmitting unit for sending pulse signals and for sending measuring signals, a receiving unit for receiving response signals and a processing unit for obtaining a measuring signal from the inverted signal.

Similar to the above embodiments, the inverted signal comprises a time-reversed portion of the response signal to the corresponding pulse signal or a signal derived therefrom.

The processing unit, the transmitting unit and the receiving unit are used to supply a measuring signal to the first connector, to receive a response signal of the first (predetermined) measuring signal at the second connector and to obtain a flow velocity of the fluid from the response signal.

In addition, the processing unit, the transmitting unit and the receiving unit of the device can be used to perform any of the other measurement and calibration methods described above in relation to the device with the first clamp-on measuring transducer and the second clamp-on measuring transducer.

In another embodiment, the device comprises a digital-to-analog converter,

- 9 043606 which is connected to the corresponding connectors, and an analog-to-digital converter which is connected to the corresponding connectors. In addition, the device contains a machine-readable memory device for storing at least one measuring signal.

According to another embodiment, the device comprises a direct digital signal synthesizer, which comprises an ADC, a frequency control register, a reference generator, a generator with numerical program control and a low-pass recovery filter. The ADC is configured to be connected to the corresponding connectors via a low-pass recovery filter.

According to another aspect, the present invention discloses a computer-executable method for determining whether a given testing device or a device under test measures the flow rate of a fluid in a fluid pipeline according to the above-mentioned measuring method. The testing method does not provide a mathematical proof that the same method is used, but provides a probability that is sufficient for practical application.

According to this method, a fluid pipeline is provided with a fluid medium that has a predetermined velocity relative to the fluid pipeline.

The pipeline for a fluid medium is provided with a first ultrasonic measuring transducer and a second ultrasonic measuring transducer, which are installed in corresponding first and second locations.

The test pulse signal is supplied to the first ultrasonic measuring transducer of the testing device, and the test signal of response to the test pulse signal is received at the second ultrasonic measuring transducer of the testing device.

The first test measuring signal is obtained from the first response signal, wherein obtaining the first measuring signal includes reversing in time the corresponding first or second response signal, or a part thereof.

The first test measuring signal is compared with the first measuring signal that is emitted on the measuring transducer of the testing device. It is determined that the testing device uses a method for determining the flow rate of a fluid in a pipeline for a fluid according to one of claims 1-5, if the first test measuring signal and the first measuring signal are similar.

In particular, this method can be performed for each pair of measuring transducers mentioned in one of paragraphs 1-5, and it is determined that the corresponding method is applied if the obtained measuring signals are similar for each such pair of measuring transducers.

More specifically, with respect to the method according to claim 1, the corresponding testing method may further include providing the pipeline for a fluid with a third ultrasonic measuring transducer, supplying a test pulse signal to the first ultrasonic measuring transducer of the testing device or to the second ultrasonic measuring transducer of the testing device, receiving a second test response signal to the test pulse signal at the third ultrasonic measuring transducer of the testing device, obtaining a second test measurement signal from the second test response signal, and comparing the second test measurement signal with a second measurement signal that is emitted at the measuring transducer of the testing device.

It is determined that the testing device uses the method for determining the flow rate of a fluid in a pipeline for a fluid according to paragraph 1, if the first test measuring signal and the first measuring signal are similar.

The subject matter of the present invention is now explained in more detail with reference to the following figures, in which Fig. 1 shows a first flow meter device with two piezoelectric elements;

Fig. 2 shows the device of the flow meter according to Fig. 1 with one direct signal and two scattered signals;

Fig. 3 shows the device of the flow meter according to Fig. 1, when viewed in the direction of flow;

Fig. 4 shows a second flow meter device with four piezoelectric elements and four direct signals;

Fig. 5 shows the flow meter device according to Fig. 4, viewed in the direction of flow;

Fig. 6 shows a schematic representation of the test signal;

Fig. 7 shows a schematic representation of the response of the test signal;

Fig. 8 shows a schematic representation of the inverted signal;

Fig. 9 shows a schematic representation of the response from an inverted signal;

Fig. 10 shows the first inverted signal in high resolution;

Fig. 11 shows the response of the inverted signal of Fig. 10;

Fig. 12 shows another inverted signal in high resolution;

Fig. 13 shows the response of the inverted signal of Fig. 12;

Fig. 14 shows another high resolution inverted signal;

- 10 043606 in Fig. 15 the response of the inverted signal from Fig. 14 is shown;

Fig. 16 shows another inverted signal in high resolution;

Fig. 17 shows the response of the inverted signal of Fig. 16;

Fig. 18 shows another high resolution inverted signal;

Fig. 19 shows the response of the inverted signal of Fig. 18;

Fig. 20 shows another high resolution inverted signal;

Fig. 21 shows the response of the inverted signal of Fig. 20;

Fig. 22 shows another inverted signal in high resolution;

Fig. 23 shows the response of the inverted signal of Fig. 22;

Fig. 24 shows another inverted signal in high resolution;

Fig. 25 shows the response of the inverted signal of Fig. 24;

Fig. 26 shows another inverted signal in high resolution;

Fig. 27 shows the response of the inverted signal of Fig. 26;

Fig. 28 shows another inverted signal in 12-bit resolution;

Fig. 29 shows the response of the signal from Fig. 28;

Fig. 30 shows another inverted signal in 3-bit resolution;

Fig. 31 shows the response of the signal from Fig. 30;

Fig. 32 shows another inverted signal in 2-bit resolution;

Fig. 33 shows the response of the signal from Fig. 32;

Fig. 34 shows another inverted signal in 1-bit resolution;

Fig. 35 shows the response of the signal from Fig. 34;

Fig. 36 shows a short pulse on the piezoelectric element of the flow meter of Fig. 1;

Fig. 37 shows a signal from the piezoelectric element of the flow meter of Fig. 1, which is obtained from the inverted response of the signal of Fig. 36;

Fig. 38 shows the response of the signal from Fig. 37;

Fig. 39 shows the upstream and downstream cross-correlation function;

Fig. 40 shows an enlarged view of the section of Fig. 39;

Fig. 41 shows the response signal of the inverted signal for a 12-degree misalignment relative to the opposite placement of the piezoelectric elements;

Fig. 42 shows the arrangement of many-to-one flowmeter sensors according to the present invention;

Fig. 43 shows the arrangement of one-to-many type sensors for flow measurement according to the present invention;

Fig. 44 shows a one-to-one arrangement of flow rate sensors in a layer according to the present invention;

Fig. 45 shows a device with multiple sensors for measuring flow in several layers according to the present invention;

Fig. 46 shows a device for measuring flow rate according to the present invention;

Fig. 47 shows a direct digital synthesizer for use in the device of Fig. 46;

Fig. 48 shows a longitudinal section of the asymmetric placement of measuring transducers;

Fig. 49 shows a cross-section of the arrangement according to Fig. 49;

Fig. 50 shows a single cycle measurement signal for time-of-flight measurement;

Fig. 51 shows a measuring signal with ten cycles for measuring the time of flight;

Fig. 52 shows a measuring signal obtained from a time-reversed signal;

Fig. 53 shows a response signal of the signal of Fig. 50, when the transmission channel is provided with an asymmetric device of Figs. 48 and 49;

Fig. 54 shows a response signal of the signal of Fig. 51 for the device of Figs. 48 and 49;

Fig. 55 shows a response signal of the signal of Fig. 52 for the device of Figs. 48 and 49;

Fig. 56 shows the procedure for obtaining measuring signals corresponding to two signal paths in an arrangement with three measuring transducers;

Fig. 57 shows the measurement of the flow rate by the VP using the measuring signals obtained in the method according to item 56;

Fig. 58 shows two different placements of two measuring transducers on a pipeline;

Fig. 59 shows the pressure distributions of the measuring signals obtained in the arrangement according to Fig. 58;

Fig. 60 shows an example of a method for determining whether the device under test uses the same flow measurement method as the control device.

In the following description, details are given to describe embodiments of the present invention. However, it will be apparent to one skilled in the art that the embodiments can be practiced without such details.

Some parts of the embodiments that are shown in the drawings have similar parts. Similar parts have the same names or the same part numbers with a main symbol or alphabetic symbol. The description of such similar parts is also applicable by reference to other similar parts, where appropriate, thereby reducing repetition of text without limiting the present invention.

In Fig. 1 a first device 10 of a flow meter is shown. In the device in the form of a flow meter, a first piezoelectric element 11 is arranged on the outer wall of a pipe 12, which is also called a tube 12. A second piezoelectric element 13 is arranged on the opposite side of the pipe 12 so that a straight line between the piezoelectric element 11 and the piezoelectric element 13 located downstream is oriented at an angle β to the direction 14 of the average flow, which is at the same time the direction of the axis of symmetry of the pipe 12. The angle β is selected to be approximately 45° in the example of Fig. 1, but it can also be larger, such as, for example, 60°, or smaller, such as, for example, 30°.

A piezoelectric element, such as piezoelectric elements 11, 13 in Fig. 1, can generally operate as an acoustic transmitter and as an acoustic sensor. The acoustic transmitter and the acoustic sensor can be provided with the same piezoelectric element or different sections of the same piezoelectric element. In this case, the piezoelectric element or measuring transducer is also called a piezoelectric transmitter when it operates as a transmitter or sound source, and it is also called an acoustic sensor or receiver when it operates as an acoustic sensor.

When the flow direction is as shown in Fig. 1, the first piezoelectric element 11 is also called an upstream piezoelectric element, and the second piezoelectric element 13 is also called a downstream piezoelectric element. The flow meter according to the present invention operates in both flow directions essentially the same, and the flow direction in Fig. 1 is given only as an example.

Fig. 1 shows the flow of electrical signals according to Fig. 1 for a configuration in which the upstream piezoelectric element 11 operates as a piezoelectric measuring transducer and the downstream piezoelectric element 13 operates as an acoustic sensor. For clarity, the device operates upstream and downstream, i.e. the position of the piezoelectric elements can be interchanged.

The first calculation unit 15 is connected to the upstream piezoelectric element 11, and the second calculation unit 16 is connected to the downstream piezoelectric element 13. The first calculation unit 15 comprises a first digital signal processor, a first digital-to-analog converter (DAC) and a first analog-to-digital converter (ADC). Similarly, the second calculation unit 16 comprises a second digital signal processor, a second digital-to-analog converter (DAC) and a second analog-to-digital converter (ADC). The first calculation unit 15 is connected to the second calculation unit 16.

The device with two calculation units 15, 16 shown in Fig. 1 is given only as an example. Other embodiments may have different numbers and arrangements of the calculation units. For example, there may be only one central calculation unit, or there may be two analog-to-digital/digital-to-analog converters and one central calculation unit, or there may be two small calculation units on the measuring converters and one larger central calculation unit.

The computing unit or units may be provided by microcontrollers or application-specific integrated circuits (ASICs), or field-programmable gate arrays (FPGAs), for example. Moreover, the synthesis of the electrical signal from the stored digital signal may be provided by a direct digital synthesizer (DDS), which contains a digital-to-analog converter (DAC).

The method for generating a measuring signal according to the present invention includes the following steps.

A predetermined digital test signal is generated by synthesizing an acoustic signal by means of a digital signal processor of the first computing unit 15. The digital test signal is sent from the first computing unit 15 to the piezoelectric measuring transducer 11 via a signal path 17. The piezoelectric measuring transducer 11 generates a corresponding ultrasonic test signal. The units 15 and 16 can also be provided in one separate unit.

The test signal is provided as a short pulse, for example with one oscillation of 1 MHz or with 10 such oscillations. In particular, the test signal can be provided with a small number of oscillations with constant amplitude, thus approximately corresponding to a rectangular signal. The oscillation or oscillations can have a sinusoidal shape, a triangular shape, a rectangular shape or also other shapes.

An ultrasonic test signal passes through the liquid in pipe 12 to the piezoelectric

- 12 043606 to the sensor 13. In Fig. 1, the direct path of the ultrasonic signal is indicated by arrow 18. Similarly, the direct path of the ultrasonic signal in the opposite direction is indicated by arrow 19. The response signal is received by the piezoelectric sensor 13, sent to the second computing unit 16 via signal path 20 and digitized by the second computing unit 16.

In a further step, a digital measurement signal is obtained from the digitized response signal. Obtaining the measurement refers to inverting the digitized response signal with respect to time. According to further embodiments, the obtaining includes further steps, such as converting to a reduced resolution in the amplitude range, bandpass filtering the signal to eliminate noise, such as low-frequency noise and high-frequency noise. In particular, the bandpass filtering step can be performed before the step of inverting the signal with respect to time.

Signal inversion can be accomplished in various ways, such as by reading the memory region backwards or by reversing the sign of the sinusoidal components in the Fourier representation.

In one embodiment, a suitable portion of the digitized response signal is selected that contains the response from the direct signal. The portion of the response signal is then rotated, or inverted, with respect to time.

In other words, the parts of the response signal that are received later are sent earlier to the inverted measurement signal. If the signal is represented by a sequence with a time order of discrete amplitude values, as an example, the above-mentioned signal inversion means inverting or reversing the order of discrete amplitude values.

The resulting signal in which the direction, or sign, of time has been inverted is also called an inverted signal. The term inverted in this context refers to inversion with respect to the direction of time, not inversion with respect to a value such as an amplitude value.

Fig. 10-19 show as an example digital signals according to the present invention.

In a flow meter according to one embodiment of the present invention, the same measuring signal is used for both directions 18, 19, the downstream and upstream direction, providing a simple and effective device. According to other embodiments, different measuring signals are used for both directions. In particular, the measuring signal can be supplied to the initial receiver of the test signal. Such devices can provide advantages for asymmetrical positions and shapes of the pipe.

A method for measuring the flow rate of a liquid through a pipe, which uses the above-mentioned inverted signal as a measuring signal, comprises the following steps.

The above-mentioned measuring signal is sent from the first calculating unit 15 to the piezoelectric measuring transducer 11 via the signal path 17. The piezoelectric measuring transducer 11 generates a corresponding ultrasonic measuring signal. Examples of such a measuring signal are provided in Fig. 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 37 and 38.

The ultrasonic measuring signal passes through the liquid in the pipe 12 to the piezoelectric sensor 13. The response signal is received by the piezoelectric sensor 13, sent to the second computing unit 16 along the signal path 20 and digitized by the second computing unit 16.

The second calculation unit 16 sends the digitized response signal to the first calculation unit 15. The first calculation unit 15 determines the flight time of the received signal, for example, using one of the methods described below.

A similar method is carried out for the signal passing in the reverse direction 19, namely, the above-mentioned measuring signal is fed to the piezoelectric element 13 located downstream, and the response signal is measured by the piezoelectric element 11 located upstream to obtain the time of flight upstream (TOF_up) in the reverse direction 19. The first calculation unit 15 determines the flow velocity, for example, according to the formula with ^{2 V =} 2-L-cos^ ' ^ ^T0F up - TOF _down ), where L is the length of the straight path between the piezoelectric elements 11, 13; β is the angle of inclination of the straight path between the piezoelectric elements 11, 13 and the direction of the average flow; and c is the speed of sound in the liquid under the given conditions of pressure and temperature.

The square of the speed of sound with ^L 2 can be approximated to the second order by the expression:

TOF _U p * TOFdown which leads to the formula:

- 13 043606

L TOF _up ~TOF _down v —--2 * cos β T0F _up * T0F _down

There is no need to determine the temperature or pressure, which in turn determine the density of the fluid and the speed of sound, or to directly measure the speed of sound or the density of the fluid. Conversely, the first order of error is not excluded for only one direction of measurement.

Instead of using the factor 2 I cos β, the proportionality factor can be derived from a calibration measurement with a known flow velocity. The calibration proportionality factor takes into account additional effects such as flow profiles and the effects of sound waves that have been scattered and do not travel in a straight line.

According to a further embodiment, the process of generating a pulse signal, recording a response signal and obtaining an inverted measuring signal from the response signal is simulated in a computer. Parameters that are important, such as the diameter of the pipe 12 and the locations of the sensors, are provided as input parameters for the simulation.

According to another embodiment, the measuring signal to be supplied to the transmitting piezoelectric element is synthesized using the shape of a conventional response signal into a pulse signal, as exemplified by the waveforms shown in Figs. 37 and 38. For example, the measuring signal can be provided with a 1 MHz sinusoidal oscillation, which is amplitude modulated with an envelope according to a Gaussian probability function with a half-width of 10 μs. The half-width can be selected as an input parameter, which depends on current parameters, such as the diameter of the pipe and the location of the sensor.

The flow meter according to the present invention can also be provided as a predetermined flow meter, in which the measurement signal is generated during a test session at the plant site, in particular when the flow meter is supplied together with a pipe section.

According to a simple embodiment of the present invention, the time of flight in the upstream and downstream direction is determined by estimating the time of the maximum amplitude of the received signal relative to the time of sending the measurement signal. In order to achieve greater accuracy, the maximum can be determined using the envelope of the received signal. According to a further embodiment, the measurement is repeated several times, and the average time of flight is used.

According to a further embodiment of the present invention, the time of flight of the signal is estimated using a cross-correlation method. In particular, the corresponding time offsets can be estimated by cross-correlating the received downstream or upstream signal with the received signal at zero flow rate according to the formula: CO

SigFlow(t) = _SigFlow (t) _-SigNoFlow (t + τ), t = - 00 where Sig_Flow represents the upstream or downstream signal under the measurement condition when there is fluid flow through the pipe, and where Sig_NoFlow represents the signal under the calibration condition with zero flow. The infinite sum limits represent a sufficiently large time window [-T1, +T2]. In general, -T1 and +T2 do not have to be the same, and from a practical point of view this can be an advantage for a flow meter.

The TOF_up - TOF_down time offset is then obtained by comparing the time of the maximum of the upstream correlation function with the time of the maximum of the downstream correlation function. The envelope of the correlation function can be used to more accurately determine the location of the maximum.

In another embodiment, a separate evaluation unit is provided between the first calculation unit 15 and the second calculation unit 16, which performs the evaluation of the signal arrival time and the flow rate.

In general, the measured signal of an acoustic sensor is obtained from the superposition of scattered signals and the direct signal. The scattered signals are reflected from the inner and outer walls of the pipe one or more times, including additional scattering processes in the pipe wall. This is shown as an example in Fig. 2.

The configuration of the measuring transducer of Fig. 1 is a straight-line or Z-configuration. Other arrangements that utilize reflections on the opposite side of the pipe are also possible, such as a V- and W-configuration. The V- and W-configuration operate based on reflections on the pipe wall, which induce more scattering than the Z-configuration. The subject invention has advantages with these configurations, provided that the paths are understood correctly.

In the V-configuration, two measuring transducers are mounted on the same side of the pipe. To record a 45° reflection, they are spaced approximately one diameter apart.

- 14 043606 pipes in the direction of flow. In the W-configuration, three reflections are used. Similar to the V-configuration, two measuring transducers are mounted on the same side of the pipe. To record the signal after two reflections at 45°, they are placed at a distance of two pipe diameters in the direction of flow.

Fig. 2 shows, as an example, a first acoustic signal 1, which passes directly from the piezoelectric element 11 to the piezoelectric element 13, a second acoustic signal 2, which is scattered once on the circumference of the pipe 12, and a third signal 3, which is scattered three times on the circumference of the pipe 12.

For simplicity, the scattering events are shown as reflections in Figs. 2-5, but the actual scattering process may be more complex. In particular, the scattering of greatest importance typically occurs on the pipe wall or on the material that is mounted in front of the piezoelectric measuring transducers. Fig. 3 shows the view of Fig. 2 in the flow direction in the observation direction A-A.

Fig. 4 and 5 show a second arrangement of sensors, in which the additional piezoelectric element 22 is located at an angle of 45° to the piezoelectric element 11 and the additional piezoelectric element 23 is located at an angle of 45° to the piezoelectric element 13.

In addition, Fig. 4 and 5 show a straight or level line, the acoustic signal path for a situation in which the piezoelectric elements 11, 22 operate as piezo-measuring transducers and the piezoelectric elements 13, 23 operate as acoustic sensors. The piezoelectric element 23, which is located behind the pipe 12 in the view of Fig. 4, is shown by a dotted line in Fig. 4.

Fig. 6-9 shows a simplified method for generating a measurement signal from a test signal response. In Fig. 6-9, scattering losses are indicated by the shaded portions of the signal and arrows.

When examining Fig. 6-9, it is assumed that the acoustic signal propagates only along a path in the form of a straight line, along the first scattering channel with a time delay of Δt and along the second scattering channel with a time delay of 2Δt. Signal attenuation along the paths is not considered.

A test signal in the form of a rectangular burst is fed to the piezoelectric element 11. Due to scattering, the first part of the signal amplitude is lost due to the first scattering path and appears after a time Δt, and the second part of the signal amplitude is lost due to the second scattering path and appears after a time 2Δt. This produces a signal according to the white columns in Fig. 7, which is recorded on the piezoelectric element 13.

The signal processor inverts this recorded signal with respect to time, and it feeds the inverted signal into the piezoelectric element 11. The same scattering process, as explained earlier, is now applied to all three components of the signal. As a result, a signal according to Fig. 9 is recorded on the piezoelectric element 13, which is approximately symmetrical.

In reality, the received signals will be distributed in time, and there is often a shock wave that passes through the pipe material and arrives before the direct signal. This surface wave is rejected by choosing an appropriate time window for generating the inverted measurement signal. Similarly, signals that originate from multiple reflections and arrive later can be rejected by limiting the time window and/or by selecting specific parts of the signal.

The following Table 1 shows the measured time delays for a straight alignment, or in other words, for a straight line connection between the piezoelectric contact elements on a DN 250 pipe in a plane perpendicular to the longitudinal extension of the DN 250 pipe. The flow rate refers to the water flow through the DN 250 pipe.

In this document, a 1-cycle VP refers to a pulse, such as the pulse shown in Fig. 36, which is generated by a piezoelectric element that is excited by an electrical signal with 1 oscillation having a period of 1 μs. A 10-cycle VP refers to a signal that is generated by a piezoelectric element that is excited by an electrical signal with 10 constant-amplitude sinusoidal oscillations having a period of 1 μs.

Consumption/Method 21 ^m3 /h 44 ^m3 /h 61 ^m3 /h VP with 1 cycle 7 ns 18 ns 27 ns VP with 10 cycles 9 ns 19 ns 26 ns Time when appealing 8 ns 18 ns 27 ns

- 15 043606

The following table shows the measured time delays for a 12 degree misalignment relative to a flat line junction between the piezoelectric patch elements on the pipe.

DN 250 in a plane perpendicular to the longitudinal extension of the DN 250 pipe (see also Fig. 48 and 49).

Consumption/Method 21 ^m3 /h 44 ^m3 /h 61 ^m3 /h VP with 1 cycle 10 ns 21 ns 28 ns VP with 10 cycles 9 ns 17 ns 26 ns Time when appealing 4 ns 12 ns 26 ns

Figure 9-27 shows the high-resolution inverted signals and their corresponding response signals. The voltage is represented in arbitrary time units in microseconds.

The time axes in the upper figures show the transmission time of the inverted signal. The transmission time is limited by the time window that is used to record the inverted signal. In the example of Fig. 9-27, the time window begins just before the onset of the maximum that occurs from the direct signal and ends 100 µs after it.

The time axes in the lower figures are centered around the maximum of the response signals and last 100 µs, which is the size of the time window for the inverted signal, before and after the maximum of the response signals.

Fig. 28-35 shows the digitized inverted signals in high resolution and in 12-, 3-, 2- and 1-bit resolution in the amplitude range and their corresponding response signals. The voltage is presented in volts over time in microseconds. The signals in Fig. 28-35 were obtained for a DN 250 pipe filled with water.

The time window length for the inverted signal is 450 μs. Therefore, the time window in Figs. 28-35 is more than four times larger than that shown in the previous Figs. 9-27.

In Fig. 28-35 it can be seen that even digitizing with 1-bit resolution produces a sharp spike. It can be seen that the spike becomes even more pronounced for lower resolutions. A possible explanation for this effect is that in the example of Fig. 28-35 the overall energy of the input signal is increased by using coarser digitizing in the amplitude range, while the response signal remains concentrated in time.

Fig. 36 shows a signal generated by a piezoelectric element after receiving an electrical pulse that lasts approximately 0.56 μs, which is equal to a frequency of 3.57 MHz. Due to the inertial force of the piezoelectric element, the maximum amplitude for a negative voltage is smaller than for a positive voltage, and there are multiple wave reverberations before the piezoelectric element stops.

Fig. 37 shows an electrical signal that is supplied to a piezoelectric element, such as the upstream piezoelectric element 11 of Fig. 1. The signal of Fig. 37 is obtained by forming an average of ten digitized response signals into a signal of the type shown in Fig. 36 and inverting the signal, wherein the response signals are received by a piezoelectric element, such as the downstream piezoelectric element 13 of Fig. 1.

In the example of Fig. 37, the digitized signals are obtained by clipping a portion of the signal from the response signal that begins approximately 10 μs before the start of the response signal envelope and that ends approximately 55 μs after the response signal envelope. The shape of the response signal envelope of Fig. 37 is similar to the shape of a Gaussian probability distribution, or, in other words, a suitably shifted and scaled version of exp(-x ^λ 2).

Fig. 38 shows a portion of a response signal to the signal shown in Fig. 37, wherein the signal of Fig. 37 is supplied to a first piezoelectric element, such as the upstream piezoelectric element 11, and is received at a second piezoelectric element, such as the downstream piezoelectric element 13 of Fig. 1.

Fig. 39 shows an upstream cross-correlation function and a downstream cross-correlation function, which are obtained by cross-correlating the upstream signal and the downstream signal of the device of Fig. 1 with the signal obtained at zero flow rate, respectively.

Fig. 40 shows an enlarged view of the section of Fig. 39. The two position indicators indicate the positions of the corresponding maxima of the cross-correlation function upstream and downstream. The time difference between the maxima is the magnitude of the time difference between the upstream and downstream signal.

Fig. 41 shows the response signal, which was obtained under similar conditions as for the signal

- 16 043606 response of Fig. 37. Unlike the device of Fig. 37, the piezoelectric elements are misaligned by degrees relative to the arrangement in the form of a straight line along the perimeter of the pipe. The offset is shown in the inset drawing of Fig. 41. Fig. 41 shows that even under the conditions of misalignment there is a fairly well defined response signal.

Fig. 42-45 show, as an example, different arrangements of clamp-on piezoelectric measuring transducers for which the flow measurement according to the present invention can be used. In particular for clamp-on measuring transducers, the flow measurement method according to the present invention can lead to an improvement in the signal-to-noise ratio in the devices shown in Fig. 42-45 or in other similar measuring transducer devices. In addition, the flow measurement method can provide energy savings by providing an increased signal amplitude of the response signal for a given signal transmission power. In this way, the signal transmission power can be reduced.

Figs. 42-45 are aligned so that the gravity force acting on the liquid in the pipe 12 is directed downwards. However, devices that are rotated relative to the devices shown in Figs. 42-45 can also be used. The direction of observation in Figs. 42-45 runs along the longitudinal axis of the pipe 12. The upstream or downstream position of the measuring transducer in Fig. 42-45 is not indicated.

In the device of Fig. 42, an array of five piezoelectric elements 31-35 is provided in a first location and another piezoelectric element 36 is located upstream or downstream of the first location. The array of piezoelectric elements 31-35 can be used to obtain a predetermined wave front and to achieve improved focusing of an acoustic wave in a predetermined direction when the array of five elements 31-35 is used as a transmitter and the additional element 36 is used as a receiver.

In the device of Fig. 43, one piezoelectric element 37 is provided at the first location, and an array of five piezoelectric elements 38-42 is located upstream or downstream of the first location. The array of piezoelectric elements 38-42 can be used to obtain an improved recording of the wave front of the response signal. The improved recording can then be used to obtain an improved measuring signal for the flow, which is then applied to one piezoelectric element 37.

Fig. 44 shows a device consisting of two piezoelectric elements 43, 44, in which one element is located downstream relative to the other. The distance d from the connection line between the piezoelectric elements 43, 44 to the axis of symmetry of the pipe 12 is approximately half the radius of the pipe 12, so that the flow layer can be measured at a distance d to the central axis of the pipe 12.

Particularly for clamp-on measuring transducers such as the piezoelectric elements 43, 44 shown in Fig. 44, the flow measurement according to the present invention provides an improved signal at the receiving piezoelectric element 44, 43 by means of beam formation.

Fig. 45 shows a device of eight piezoelectric elements 45-52, which are spaced from each other by 45°. As for the upstream and downstream placement, several devices are possible.

In one device, the sensor locations alternate around the perimeter between upstream and downstream placement, for example, 45, 47, 49, 51 upstream and 46, 48, 50, 52 downstream.

In another device, the first four elements in order around the perimeter, for example, 45-48, are located upstream or downstream relative to the other four elements, for example, 49-52. In yet another device with 16 piezoelectric elements, all piezoelectric elements 45-52 shown in Fig. 45 are located in one plane, and the device of Fig. 45 is repeated in the upstream or downstream direction.

Fig. 46 shows, as an example, a flow measuring device 60 for measuring the flow in the device of Fig. 1 or other devices according to the invention. In the device of Fig. 1, the flow measuring device 60 is provided with a first and a second computing unit 15, 16.

The flow measurement device 60 comprises a first connector 61 for connecting the first piezoelectric measuring transducer and a second connector 62 for connecting the second piezoelectric measuring transducer. The first connector 61 is connected to a digital-to-analog converter (DAC) 64 via a multiplexer 63. The second connector 62 is connected to an analog-to-digital converter 65 via a demultiplexer 66.

The ADC 65 is connected to a signal selection unit 67, which is connected to a signal inverting unit 68, which is connected to a bandpass filter 69, which is connected to a machine-readable memory device 70. In addition, the ADC 65 is connected to a speed calculation unit 71.

The DAC 64 is connected to the pulse signal generator 72 and the measuring signal generator 73. The measuring signal generator is connected to the pulse generator 72 via the command line 74. The speed calculation unit 71 is connected to the measuring signal generator 73 via the second command line 75.

In general, the pulse signal generator 72 and the measuring signal generator comprise hardware elements, such as an oscillation generator, and software elements, such as a pulse generator module and a measuring signal generator module. In this case, the command lines 74, 75 can be provided with software interfaces between the corresponding modules.

During the signal generation phase, the pulse signal generator sends a signal to the DAC 64, the selection unit 67 receives the corresponding input signal via the ADC 65 and selects a portion of the input signal. The inverting unit 68 inverts the selected portion of the signal with respect to time, the optional bandpass filter 69 filters low and high frequencies, and the resulting measuring signal is stored in the machine-readable memory 70. When the word signal is used with reference to the signal control stage, it may, in particular, refer to the representation of the signal in the machine-readable memory.

In particular, a signal representation can be defined by a pair of digitized amplitude values and associated discrete times. Other representations include, among others, Fourier coefficients, wavelet coefficients, and an envelope for the amplitude modulating the signal.

Fig. 47 shows a second embodiment of a flow measuring device 60' for measuring the flow rate in the device of Fig. 1 or other devices according to the invention. The flow measuring device 60' comprises a direct digital synthesizer (DDS) 76. For simplicity, only the components of the DDS 76 are shown. The DDS 76 is also called an arbitrary waveform generator (AWG).

The DSC 76 comprises a reference oscillator 77 which is connected to a frequency control register 78, a direct numerical control (DNC) oscillator 79 and a DAC 64. The input of the DNC 79 for N channels is connected to the output of the frequency control register 78. The input of the DAC 64 for M channels is connected to the DNC 79 and the input of the low-pass reconstruction filter is connected to the DAC 64. As an example, the DNC oscillator 79 with a clock frequency of 100 MHz can be used to generate a signal modulated in amplitude at 1 MHz.

The output of the low-pass recovery filter 80 is connected to the piezoelectric measuring transducers 11, 13 according to Fig. 1.

Due to the inertia of the quartz oscillator, it is often advantageous to use an oscillator with a higher frequency than the carrier wave to produce a predetermined amplitude modulated signal, for example using a direct digital synthesizer as shown in Fig. 47.

In particular, the steps of the method, namely storing the digital representation of the signal and performing operations such as selecting a portion of the signal, reversing the signal in time, and filtering the signal, can be interchanged. For example, the signal can be stored in the form of a time-inverted signal, or it can be read in reverse order to obtain a time-inverted signal.

Since the present invention is explained with respect to a DN 250 round pipe, it can easily be applied to other pipe sizes or even other pipe shapes. Although embodiments are explained with respect to clamp-on measuring transducers, immersible measuring transducers that enter the pipe can also be used.

Fig. 48 and 49 show an asymmetrical device of a measuring transducer, in which the second measuring transducer is offset by 12 degrees relative to the axis of symmetry of the pipeline 12.

Fig. 50 shows a measuring signal with one cycle for measuring the time of flight, and Fig. 51 shows a measuring signal with ten cycles for measuring the time of flight. The signals shown in Fig. 50 and 51 can be used for measuring the time of flight. In addition, the signals can also be used for generating a measuring signal according to the present invention using the time inversion of a received response signal, such as the response signals shown in Fig. 52 and 53.

Fig. 52 shows an example of a measurement signal that is obtained from a time-reversed signal that is stored at low resolution.

Fig. 53-55 show response signals to the corresponding signals shown in Fig. 5052. The response signal is removed by the receiving measuring transducer 11, 13 of the asymmetric device shown in Fig. 48, 49, in response to the signal of the sending measuring transducer, which is excited by the signal shown in Fig. 50.

In particular, Fig. 53 shows a response signal of the signal of Fig. 50, Fig. 54 shows a response signal of the signal of Fig. 51 for the device shown in Figs. 48 and 49, and Fig. 55 shows a response signal of the signal of Fig. 52 for the device shown in Figs. 48 and 49. In the examples shown, the response signal is more concentrated in time, has a higher amplitude and has a better defined envelope in comparison with the signals shown in Figs. 52 and 53.

The result shown in Fig. 55 shows that the benefits of impulse response time inversion, which allow, among other things, the use of lower energy signals, can be retained for coarser resolution and asymmetric transducer designs.

The results shown in Fig. 55 show that the use of the time-inverted signal according to the present invention can provide short time delays compared to the conventional measurement of the Doppler shift by time of flight using a signal with 1 or 10 oscillation cycles. Fig. 55, being the result of the device shown in Figs. 48 and 49, further shows that the measurement signal according to the present invention can be used for beamforming purposes.

Table 2 shows the resulting time delays for the asymmetric device shown in Figs. 48, 49 and for the corresponding flow rates of 21, 44 and 61 cubic meters per hour.

^^consumption Methods^^. 21 ^m3 /h 44 ^m3 /h 61 ^m3 /h VP with 1 cycle 10 ns 21 ns 28 ns VP with 10 cycles 9 ns 17 ns 26 ns inverted signal 4 ns 12 ns 26 ns

Additional examples of beamforming applications are shown in Figs. In general, yX = W* (A-1)/2 X, there are *-4=1 ^{v 7/} direct transmission paths between N transducers, ignoring wall reflections, that are provided on the pipeline. These transmission paths generally have different properties and provide different response signals.

In case all N measuring transducers are installed at different heights with respect to the flow direction or longitudinal direction of the pipeline, all these transmission channels can be used for flow measurements. Signal propagation between measuring transducers, which is perpendicular to the mean flow, is generally not useful for obtaining flow velocity components, but can still be used to determine contamination and changes in the pipeline material, and changes in the properties of the measuring transducers and their connection to the pipeline.

The flow measurement by the VP includes measurement in both directions with respect to a given transmission channel between two measuring transducers. The flow measurement by the VP, which includes transmission channels between the first measuring transducer and N-1 other measuring transducers, requires at least N successive measurements: the first measurement with the measuring signal supplied to the first measuring transducer, and N-1 successive measurements with the measuring signals supplied to each of the N-1 other measuring transducers.

In general, the required measurement signals are different for each transmission channel, and separate forward and backward measurements are needed for each transmission channel. Thus, 2x(N-1) measurements are required. For example, in the example shown in Fig. 57, max 2x(3-1)=4 measurements are possible, but not necessarily required.

The signals shown in Figs. 41 and 55 are produced by measuring transducers which radiate mainly in a preferred direction, with a maximum angle of approximately 12° to either side of the preferred direction. The directivity of the measuring transducers is achieved, among other things, by adjusting the shape of the measuring transducers and their coupling to the pipeline. Depending on the angle between the measuring transducers, not all paths can provide a sufficiently strong signal on the receiver side, especially if the sender has a high directivity. The use of only well-known methods can lead to results as shown in Fig. 53 and Fig. 54, which are generally too noisy for carrying out flow measurements. However, with the proposed method using inverted measuring signals, it is possible to achieve sufficiently good signals, such as those shown in Fig. 55.

The use of the measuring signal according to the present invention, in which time reversal is used, makes it possible to provide measuring transducers with less directivity. The measuring signal focuses the signal energy on the receiver, and the received signal is still sufficiently strong.

Similar to the measurement using only two measuring transducers or only one transmission channel, the flow measurement can be performed using a predetermined measuring signal or a signal that is obtained by means of a preliminary calibration. During the calibration step, the measuring signals are obtained from the response signals to the pulse signals. According to one example, a pulse signal is applied to a measuring transducer to obtain one or more response signals on other measuring transducers. The measuring signals are obtained by applying a time inversion to the response signals or a part thereof.

In one example, in which there are four measurement paths, successive measurements are taken along the first path, the second path, the third path, and the fourth path. The successive measurements are used to obtain the total flow and/or flows in a predetermined layer or location.

One or more flow rates can then be obtained by comparing the measurements with a predetermined flow profile. For example, the predetermined flow profile can be obtained by modeling. In another embodiment, the flow rate for a specific layer or location is estimated using the results from one or more measurement signals and known methods for calculating a flow profile. In one embodiment, the total volumetric flow rate is obtained by applying the calculated or modeled flow profile to the cross-sectional area of the pipeline.

Fig. 56 and 57 show the measurement of flow rate by time of flight using three measuring transducers and two transmission paths.

Fig. 58 and 59 show the measurement of pressure in a device with two measuring transducers. The pressure scale in Fig. 59 is presented in arbitrary units (a.u.).

The measuring signal according to the present invention is fed to the first measuring transducer 11, and the resulting pressure distribution is measured on the circumference of the pipeline 12. The measuring transducers 11, 13 are offset in the longitudinal direction, similar to the device shown in Fig. 1.

In a first example, a measuring signal, which is adapted to the signal path between the measuring transducer 11 and the measuring transducer 13, is sent from the measuring transducer 11 to the opposite measuring transducer 13 and the resulting pressure distribution is measured. This yields a curve similar to the pressure distribution 90 shown in Fig. 59, which has a peak at the location of the measuring transducer 13.

In the second example, a measuring signal which is adapted to the signal path between the measuring transducer 11 and the measuring transducer 13 is sent from the measuring transducer 11 to the measuring transducer 13' and the resulting pressure distribution is measured. In contrast to the first device, the measuring transducer 13' is offset by an angle of 45 degrees relative to the connection line passing through the first measuring transducer and the center of the pipeline 12. Even in this situation, the resulting pressure distribution forms a peak around the location of the measuring transducer 13', which means that the signal energy is concentrated around the location of the measuring transducer 13'.

Thus, the measuring signal according to the present invention, which is obtained using time reversal of the signal between the corresponding measuring transducers, results in obtaining a pressure signal which is not only concentrated in time, as shown in the corresponding second figure of the set of figures 10-35, but the resulting pressure distribution is also concentrated in space.

When using a standard signal such as a pulse signal, spatial concentration can also be achieved, but only at a fixed location close to the opposite side of the sending measuring transducer. However, when using a signal according to the present invention, which contains a time-reversed part, the pressure concentration peak can be moved.

The ultrasonic measuring transducers 11, 13, 23 shown in Figs. 56-59 can be represented by mounted measuring transducers, which are mounted on the outer side of the pipeline, or by immersible measuring transducers, which protrude into the inner part of the pipeline 12 from the outer part of the pipeline 12.

Fig. 60 shows an example of a method for determining whether the test device uses the same flow measurement method as the control device. In a first step, the control device selects a test pulse signal. For example, this may include selecting a waveform for performing amplitude modulation of a sine wave from a set of stored waveforms, such as a square wave, a sine wave, a jagged wave, etc.

In the next step, the test pulse signal is fed to the first measuring transducer. In the next step, the corresponding test response signal is obtained at the second measuring transducer. In the following steps, the test response signal or part thereof is inverted and a test measuring signal is obtained. The measuring transducers to which the control device is connected are preferably measuring transducers of the testing device.

- 20 043606

In the next step, the test measuring signal is compared with the actual measuring signal of the test device. If the test measuring signal is similar to the measuring signal of the test device, it is decided that the test device uses the same method as the control device. Alternatively or additionally, the control device can apply the test measuring signal to the measuring transducer, receive a corresponding test response signal and compare this test response signal with the response signal with the measuring signal of the test device.

The monitoring device may receive or measure the test device signals as electrical signals by connecting a wired connection from the test device to the measuring transducers, or alternatively, the signals may be measured by placing a microphone in the pipeline and receiving the microphone signal.

If the signals are not similar, the same process is repeated with additional available test pulse signals to see if one of the test pulse signals results in a test measurement signal and/or a response signal to it that is similar to the measurement signal and/or a response signal to it. In the event that a test device pulse signal is available, the control device may select the available pulse signal or a similar pulse signal instead of testing different test pulse signals, or it may narrow the selection of test pulse signals.

For a test device that uses multiple signal paths and/or combinations of pairs of sending and receiving measuring transducers to measure flow, the control device repeats the method shown in Fig. 60 for multiple signal paths and/or for multiple combinations of measuring transducers, and the corresponding measuring signals and/or response signals to the measuring signals are compared.

Although the above description is very specific, it should not be taken as limiting the scope of the embodiments, but as simply providing an idea of the proposed embodiments. The steps of the method can be performed in an order different from that shown in the provided embodiments, and the division of the measuring device into processing units and their respective relationships can differ from those shown in the provided embodiments.

In particular, the advantages of the embodiments presented above should not be taken as limiting the scope of the embodiments, but as simply explaining the likely achievements when implementing the described embodiments in practice. Thus, the scope of the embodiments should be determined by the claims and their equivalents, and not by the examples given.

Embodiments of the present invention may also be described using the following lists of features, combined into paragraphs. The corresponding combinations of features, which are described in the list of paragraphs, are considered as a separate subject of the invention, respectively, which may also be combined with other features of the invention.

1. A method for determining the flow rate of a fluid in a fluid pipeline, comprising providing the fluid pipeline with a fluid that has a predetermined velocity with respect to the fluid pipeline, providing the fluid pipeline with a first ultrasonic transducer, a second ultrasonic transducer and a third ultrasonic transducer, wherein the corresponding connection lines between the first ultrasonic transducer, the second ultrasonic transducer and the third ultrasonic transducer extend outside the axis of symmetry of the fluid pipeline, supplying a first measuring signal to the first ultrasonic transducer, measuring a first response signal to the first measuring signal on the second ultrasonic transducer, supplying a second measuring signal to the first ultrasonic transducer, measuring a second response signal to the second measuring signal on the third ultrasonic transducer, wherein the first measuring signal and the second measuring signal respectively comprise a time-reversed portion of the response signal to the corresponding pulse signal or a signal obtained therefrom, obtaining the flow rate of the fluid from at least one of the first response signal and the second response signal.

2. The method according to claim 1, including feeding the first measuring signal in the opposite direction to the second ultrasonic measuring transducer,

- 21 043606 measuring a first response signal with a reverse direction to a first measuring signal with a reverse direction on a second ultrasonic measuring transducer, feeding a second measuring signal with a reverse direction to a third ultrasonic measuring transducer, measuring a second response signal with a reverse direction to a second measuring signal with a reverse direction on the first ultrasonic measuring transducer, wherein the first measuring signal with a reverse direction and the second measuring signal with a reverse direction respectively comprise a time-reversed portion of the response signal to a corresponding pulse signal or a signal obtained from it, obtaining a flow velocity of a fluid from at least one of the first response signal, the first response signal with a reverse direction, the second response signal and the second response signal with a reverse direction.

3. The method according to claim 1 or 2, comprising feeding a third measuring signal to a second ultrasonic measuring transducer, measuring a third response signal to the second measuring signal on the third ultrasonic measuring transducer, wherein the third measuring signal comprises a time-reversed portion of the response signal to the corresponding pulse signal or a signal obtained therefrom, obtaining at least one flow rate of the fluid from the third response signal.

4. The method according to claim 3, comprising supplying a third measuring signal with a reverse direction to a third ultrasonic measuring transducer, measuring a third response signal with a reverse direction to the third measuring signal with a reverse direction on a second ultrasonic measuring transducer, wherein the third measuring signal with a reverse direction comprises a time-reversed portion of the response signal to the corresponding pulse signal or a signal obtained therefrom, obtaining at least one flow velocity of the fluid from the third response signal and the third response signal with a reverse direction.

5. A method for determining the flow rate of a fluid in a fluid pipeline, comprising providing the fluid pipeline with a fluid that has a predetermined velocity with respect to the fluid pipeline, providing the fluid pipeline with a first ultrasonic clamp-on measuring transducer and a second ultrasonic clamp-on measuring transducer, wherein the connection line between the first ultrasonic clamp-on measuring transducer and the second ultrasonic clamp-on measuring transducer extends outside the axis of symmetry of the fluid pipeline, supplying a measuring signal to the first ultrasonic clamp-on measuring transducer, measuring a response signal to the measuring signal on the second ultrasonic clamp-on measuring transducer, wherein the measuring signal comprises a time-reversed portion of the response signal to the corresponding pulse signal or a signal obtained therefrom, obtaining the flow rate of the fluid from the response signal.

6. The method according to claim 5, comprising feeding a measuring signal with a reverse direction to a second ultrasonic clamp-on measuring transducer, measuring a response signal with a reverse direction to the measuring signal on the first ultrasonic clamp-on measuring transducer, wherein the measuring signal comprises a time-reversed portion of the response signal to the corresponding pulse signal or a signal obtained from it, obtaining the flow velocity of the fluid from the response signal.

7. A method according to any of the preceding paragraphs, wherein the portion of the signal that is used to obtain the corresponding measurement signals comprises a first portion near the maximum amplitude of the response signal and a final portion of the signal, wherein the final portion of the signal extends in time after the time of reaching the maximum amplitude.

8. The method according to one of the preceding paragraphs, including processing at least one of the response signals to determine a change in the thickness of the pipeline wall or to determine the characteristics of the material of the pipeline walls by determining the characteristics of the longitudinal and transverse sound wave.

9. The method according to claim 1, comprising providing a fluid pipeline with a fluid, providing a first pulse signal to one of the first or second ultrasonic measuring transducer, receiving a first response signal to the first pulse signal on the other of the first or second ultrasonic measuring transducer, providing a second pulse signal to one of the first or third ultrasonic measuring transducer, receiving a second response signal to the second pulse signal on the other of the first or third ultrasonic measuring transducer, obtaining a first measurement signal from the first response signal, obtaining a second measurement signal from the second response signal, wherein obtaining the respective first and second measurement signals includes selecting a portion of the respective first and second response signals or a signal obtained therefrom and reversing this portion of the signal in time, storing the first measurement signal and the second measurement signal for further use.

10. The method according to claim 5, including providing a pipeline for a fluid with a fluid, providing a pulse signal to one of the first ultrasonic clamp-on measuring transducer and the second ultrasonic clamp-on measuring transducer, receiving a response signal to the pulse signal on the other of the first ultrasonic clamp-on measuring transducer and the second ultrasonic clamp-on measuring transducer, obtaining a measuring signal from the response signal, wherein obtaining the measuring signal includes selecting a portion of the corresponding response signal or a signal obtained from it and reversing this portion of the signal in time, storing the measuring signal for further use.

11. The method according to claim 9 or 10, comprising repeating the steps of supplying a pulse signal and receiving a corresponding response signal multiple times, thereby obtaining a plurality of response signals, obtaining a corresponding measurement signal from the average value of the received response signals.

12. The method according to one of claims 9 to 11, wherein obtaining the corresponding measurement signal includes digitizing the corresponding response signal or a signal obtained from it with respect to amplitude.

13. The method according to claim 12, including increasing the bit resolution of the digitized signal to increase the amplitude of the response signal to the corresponding measurement signal.

14. The method according to claim 12, including reducing the bit resolution of the digitized signal to increase the amplitude of the response signal to the corresponding measurement signal.

15. The method according to claim 12, wherein the bit resolution of the digitized signal relative to the amplitude is a low bit resolution.

16. Machine-readable program code containing machine-readable instructions for performing the method according to one of paragraphs 1-15.

17. A machine-readable storage device, wherein the machine-readable storage device contains a machine-readable program code according to paragraph 16.

18. A specialized electronic component designed to perform the method according to one of paragraphs 1-15.

19. A device for measuring the flow rate of a fluid in a pipeline using a time-of-flight ultrasonic flowmeter, comprising a first connector for connecting a first ultrasonic element, a second connector for connecting a second ultrasonic element, a third connector for connecting a third ultrasonic element, a transmitting unit for sending pulse signals and for sending measuring signals, a receiving unit for receiving response signals, a processing unit for obtaining a first measuring signal from a first inverted signal, for obtaining a second measuring signal from a second inverted signal and for storing the first measuring signal and the second measuring signal, wherein obtaining the first inverted signal and the second inverted signal includes reversing in time a portion of the response signal to the corresponding pulse signal or a signal obtained from it, and wherein the processing unit, the transmitting unit and the receiving unit are used to supply the first measuring signal to the first connector and receive the first response signal to the first measuring signal at the second connector, supply the second measuring signal to the first connector, receive the second response signal to the second measuring signal at the third connector,

- 23 043606 and obtaining a flow rate of the fluid from at least one of the first response signal and the second response signal.

20. A device for measuring the flow rate of a fluid in a pipeline using a time-of-flight ultrasonic flow meter, comprising a first connector, a first ultrasonic clamp-on transducer that is connected to the first connector, a second connector, a second ultrasonic clamp-on transducer that is connected to the second connector, a portion of the pipeline, wherein the first ultrasonic clamp-on transducer is mounted on the portion of the pipeline at a first location, and a second ultrasonic clamp-on transducer is mounted on the portion of the pipeline at a certain location, wherein the respective connection lines between the first ultrasonic clamp-on transducer and the second ultrasonic clamp-on transducer extend outside the axis of symmetry of the pipeline for the fluid, a transmitting unit for sending pulse signals and for sending the measuring signals, a receiving unit for receiving the response signals, a processing unit for obtaining a measuring signal from the inverted signal, wherein obtaining the inverted signal includes reversing in time a portion of the response signal to the corresponding pulse signal or a signal obtained therefrom, and wherein the processing unit, the transmitting unit and the receiving unit are used to supply the measuring signal to a first connector, receiving a response signal to the first measurement signal at the second connector, and obtaining a flow rate of the fluid from the response signal.

21. The device according to claim 20, further comprising a digital-to-analog converter (DAC), wherein the DAC is connected to the first connector, an analog-to-digital converter (ADC), wherein the ADC is connected to the second connector, a machine-readable memory device for storing the measurement signal.

22. The device according to claim 20, further comprising a selection unit, wherein the selection unit is used to select a portion of the received response signal to the pulse signal or a signal obtained therefrom, and an inversion unit, wherein the inversion unit is used to invert in time the selected portion of the received response signal to obtain an inverted signal.

23. The device according to claim 20, comprising a direct digital signal synthesizer, wherein the direct digital signal synthesizer comprises an ADC, a frequency control register, a reference oscillator, a numerically controlled oscillator and a low-pass recovery filter, wherein the ADC is configured to be connected to the first and second connectors via the low-pass recovery filter.

24. The device according to claim 20, comprising a portion of a pipeline, wherein the first ultrasonic measuring transducer is mounted on the portion of the pipeline at a first location, and the second ultrasonic measuring transducer is mounted on the portion of the pipeline at a second location.

25. A method for determining whether a testing device measures a fluid flow rate in a fluid conduit according to one of claims 1 to 5, comprising providing the fluid conduit with a fluid that has a predetermined velocity relative to the fluid conduit, providing the fluid conduit with a first ultrasonic transducer and a second ultrasonic transducer, supplying a test pulse signal to the first ultrasonic transducer of the testing device, receiving a test response signal to the test pulse signal at a second ultrasonic transducer of the testing device, obtaining a test measurement signal from the test response signal, wherein obtaining the test measurement signal includes reversing in time the corresponding first or second response signal, or a portion thereof, comparing the first test measurement signal with a first measurement signal that is emitted at the transducer of the testing device, wherein determining that the testing device applies the method for determining the fluid flow rate in the fluid conduit according to one of claims 1 to 5, if the first the test measuring signal and the first measuring signal are similar.

26. The method according to item 25, including

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Claims (15)

providing the fluid conduit with a third ultrasonic transducer, providing a test pulse signal to a first ultrasonic transducer of the test device or a second ultrasonic transducer of the test device, receiving a second test signal in response to the test pulse signal at the third ultrasonic transducer of the test device, obtaining a second test signal measurement signal from the second response test signal, comparing the second test measurement signal with the second measurement signal that is emitted at the test device transducer, and determining that the test device uses the method for determining the flow rate of a fluid in a fluid conduit according to claim 1 , if the first test measurement signal and the first measurement signal are similar. Links: 10 - flow meter device; 11 - piezoelectric element located upstream; 12 - pipe; 13 - piezoelectric element located downstream; 14 - direction of the average flow; 15 - first calculation block; 16 - second calculation block; 17 - signal path; 20 - signal path; 22 - piezoelectric element; 23 - piezoelectric element; 31 -52 - piezoelectric elements; 60, 60' - flow measurement device; 61 - first connector; 62 - second connector; 63 - multiplexer; 64 - DAC; 65 - ADC; 66 - demultiplexer; 67 - signal selection block; 68 - signal inversion block; 69 - bandpass filter; 70 - storage device; 71 - speed calculation block; 72 - pulse signal generator; 73 - measuring signal generator; 74 - command line; 75 - command line; 76 - PDS; 77 - reference generator; 78 - frequency control register; 79 - generator with numerical program control; 80 - low pass filter. CLAIM 1. A system for measuring the flow rate of a fluid in a pipeline (12) for a fluid using a time-of-flight ultrasonic flow meter (10), containing a first connector (61) for connecting the first piezoelectric measuring transducer (11), a second connector (62) for connecting the second piezoelectric transducer (13), a third connector for connecting the third piezoelectric transducer (23), and the corresponding connection lines between the first piezoelectric transducer (11), the second piezoelectric transducer (13) and the third piezoelectric transducer (23) extend outside the axis symmetry of the pipeline (12) for the fluid, the first piezoelectric measuring transducer - 25 043606 (11) and the third piezoelectric measuring transducer (23) are offset relative to the second piezoelectric measuring transducer (13) in the longitudinal direction of the fluid pipeline (12), a transmitting unit containing a pulse signal generator for sending pulse signals and a measuring signal generator for sending measurement signals to the first connector (61), a receiving unit for receiving response signals to pulse signals at the second connector (62), a processing unit for obtaining a first measurement signal from the first inverted signal, for obtaining a second measurement signal from the second inverted signal, and storing a first measurement signal and a second measurement signal, wherein obtaining the first inverted signal and the second inverted signal includes time reversal of a portion of a response signal to a corresponding pulse signal or a signal obtained from a response signal to a corresponding pulse signal, and wherein the transmitting unit is configured to supply the first measurement signal and a second measurement signal into the first connector (61), the receiving unit is configured to receive a first response signal to the first measurement signal at the second connector (62) and receive a second response signal to the second measurement signal at the third connector, and the processing unit is configured to the ability to obtain a fluid flow velocity from at least one of the first response signal and the second response signal using a time-of-flight method by calculating the difference in propagation time of the first measurement signal and the second measurement signal propagating in the fluid in the direction of flow and against the direction of flow. 2. A method for determining the flow rate of a fluid in a fluid pipeline (12) using a time-of-flight flow meter (10), wherein the fluid has a predetermined speed relative to the fluid pipeline (12), and wherein the fluid pipeline (12) The medium is a pipeline for a fluid with an axis of symmetry, and the method includes the following steps: installation on the fluid pipeline (12) of the first piezoelectric measuring transducer (11), the second piezoelectric measuring transducer (13) and the third piezoelectric measuring transducer (23), and the corresponding connection lines between the first piezoelectric measuring transducer (11), the second piezoelectric measuring transducer (13) and the third piezoelectric measuring transducer (23) pass outside the axis of symmetry of the pipeline (12) for the fluid, and the first piezoelectric measuring transducer (11) and the third piezoelectric measuring transducer (23) are offset relative to the second piezoelectric measuring transducer (13) in longitudinal direction of the fluid conduit (12), supplying a first pulse signal to the second piezoelectric transducer (13), receiving a first response signal to the first pulse signal at the first piezoelectric transducer (11), supplying a second pulse signal to the third piezoelectric transducer ( 23), receiving a second response signal to a second pulse signal on the first piezoelectric measuring transducer (11), receiving a first measuring signal, including time reversal of a portion of said first response signal to said first pulse signal or a signal obtained from said first response signal, receiving a second measurement signal, including time reversal of a portion of said second response signal to said second pulse signal or a signal obtained from said second response signal, supplying the first measurement signal to the first piezoelectric measuring transducer (11), and measuring the first response signal to the first measurement signal on the second piezoelectric measuring transducer (13), supplying a second measuring signal to the first piezoelectric measuring transducer (11), measuring a second response signal to the second measuring signal on the third piezoelectric measuring transducer (23), wherein the first measuring signal and the second measuring signal respectively contain an inverted time portion of a response signal to a corresponding pulse signal that is transmitted between the same pair of piezoelectric transducers as the corresponding measurement signal, or a signal derived from a response signal to a corresponding pulse signal, obtaining the fluid flow rate from at least at least one of the first response signal and the second response signal using a time-of-flight method, calculating the difference in propagation time of the first measurement signal and the second measurement signal propagating in the fluid in the direction of flow and against the direction of flow. 3. The method according to claim 2, characterized in that it includes supplying a first measurement signal with a reverse direction to a second piezoelectric measuring transducer (13), measuring a first response signal with a reverse direction to the first measuring signal with a reverse direction on the first piezoelectric measuring transducer (11 ), supplying a second measurement signal with a reverse direction to the third piezoelectric measuring transducer (23), measuring a second response signal with a reverse direction to a second measuring signal with a reverse direction on the first piezoelectric measuring transducer (11), wherein the first measuring signal with a reverse direction and the second the reverse direction measurement signal respectively comprises a time-reversed portion of a response signal to a corresponding pulse signal or a signal derived from a response signal to a corresponding pulse signal, obtaining a fluid flow rate from at least one of the first response signal, the first reverse direction response signal , a second response signal, and a second response signal with a reverse direction. 4. The method according to claim 2, characterized in that it includes obtaining a third measurement signal, including time reversal of a portion of the response signal to a corresponding pulse signal that is transmitted between the second piezoelectric measuring transducer (13) and the third piezoelectric measuring transducer (23), or signal obtained from the response signal to the corresponding pulse signal, supplying a third measurement signal to the second piezoelectric measuring transducer (13), measuring the third response signal to the second measurement signal on the third piezoelectric measuring transducer (23), wherein the third measurement signal includes a time-reversed portion a response signal to the corresponding pulse signal or a signal obtained from the response signal to the corresponding pulse signal, obtaining at least one fluid flow rate from the third response signal. 5. The method according to claim 4, characterized in that it includes supplying a third measurement signal with a reverse direction to the third piezoelectric measuring transducer (23), measuring a third response signal with a reverse direction to the third measuring signal with a reverse direction on the second piezoelectric measuring transducer (13 ), wherein the third reversed measurement signal comprises a time-reversed portion of a response signal to the corresponding pulse signal or a signal derived from the response signal to the corresponding pulse signal, obtaining at least one fluid flow rate from the third response signal and the third response signal with in the opposite direction. 6. The method according to claim 2, characterized in that the part of the signal that is used to obtain the corresponding measurement signals comprises a first part near the maximum amplitude of the response signal and a final part of the signal, wherein the final part of the signal passes in time after the time of reaching the maximum amplitude. 7. The method according to claim 2, characterized in that it includes processing at least one of the response signals to determine a change in the thickness of the wall of the pipeline (12) or to determine the characteristics of the material of the pipeline walls by determining the characteristics of the longitudinal and transverse sound waves. 8. The method according to claim 2, characterized in that it includes providing a fluid conduit (12) with a fluid, providing a first pulse signal to one of the first or second piezoelectric transducer (11, 13), receiving a first response signal to the first pulse signal at the other of the first or second piezoelectric transducer (11, 13), providing a second pulse signal to one of the first or third piezoelectric transducer (11, 23), receiving a second response signal to the second pulse signal at the other of the first or third piezoelectric transducer measuring transducer (11, 23), - 27 043606 obtaining a first measurement signal from a first response signal, obtaining a second measurement signal from a second response signal, wherein obtaining the respective first and second measurement signals includes selecting a portion of the respective first and second response signals or a signal derived from the first and second response signals, and reversing this part of the signal in time, storing the first measurement signal and the second measurement signal for future use. 9. The method according to claim 8, characterized in that it includes repeating the steps of applying a pulse signal and receiving a corresponding response signal a plurality of times to thereby obtain a plurality of response signals, obtaining a corresponding measurement signal from an average value of the received response signals. 10. The method of claim 8, wherein obtaining the corresponding measurement signal includes digitizing the corresponding response signal or a signal derived from the corresponding response signal with respect to amplitude. 11. The method of claim 10, characterized in that it includes increasing the bit resolution of the digitized signal to increase the amplitude of the response signal to the corresponding measurement signal. 12. The method according to claim 10, characterized in that it includes reducing the bit resolution of the digitized signal to increase the amplitude of the response signal to the corresponding measurement signal. 13. The method according to claim 10, characterized in that the bit resolution of the digitized signal with respect to the amplitude is a low bit resolution. 14. A method for determining whether the test device measures the flow rate of a fluid in a fluid conduit (12) according to the method of claim 2, wherein the fluid has a predetermined velocity relative to the fluid conduit (12), wherein the method includes the following steps: installation on the fluid pipeline (12) of the first piezoelectric measuring transducer (11) and the second piezoelectric measuring transducer (13), supplying a test pulse signal to the first piezoelectric measuring transducer (11) of the testing device, receiving a first test signal in response to the test pulse signal at the second piezoelectric measuring transducer (13) of the testing device, obtaining a first test measurement signal from the first test response signal, wherein obtaining the first test measurement signal includes time reversal of the first test response signal or part thereof, comparing the first test measurement signal with the first measurement signal, which is emitted at the measuring transducer of the test device, wherein it is determined that the test device applies the method for determining the flow rate of a fluid in a fluid conduit (12) according to claim 2, if the first test measurement signal and the first measurement signal are similar. 15. The method according to claim 14, characterized in that it includes installing a third piezoelectric measuring transducer (23) on the fluid pipeline (12), supplying a test pulse signal to the first piezoelectric measuring transducer (11) of the test device or to the second piezoelectric measuring transducer (13) of the test device, receiving a second test signal in response to the test pulse signal at the third piezoelectric transducer (23) of the test device, obtaining a second test measurement signal from the second test response signal, comparing the second test measurement signal with a second measurement signal that is emitted at the measuring transducer of the testing device, wherein it is determined that the testing device applies the method for determining the flow rate of a fluid in a fluid pipeline (12) according to claim 2, if the first test measurement signal and the first measurement signal are similar. -