Fluid velocity meter for installation in pipes

Abstract

A liquid velocity meter for mounting in pipe, which comprises a turbulence-forming sensor housing arranged transversely in the pipe and where the turbulence-forming sensor housing has a triangular cross-section. The turbulence-forming sensor housing has a front surface facing the stream and two equal side surfaces with a top edge aligned with the stream and a sensor flag which extends in a direction of the stream out from the top edge, and with a root part mounted in a top part of the turbulence-forming sensor housing, where the sensor flag has two piezoelectric elements laminated on an elastic, electrically insulating layer, and are connected to a signal conditioner.

Description

[0001] Title: Fluid velocity meter for installation in pipes

[0002] Introduction

[0003] The present invention relates to a fluid velocity meter which is mounted in pipes to primarily measure the velocity and volume flow of the fluid. More specifically it relates to an improved water velocity meter which is capable of measuring lower and higher flow velocities.

[0004] The background of the invention is that piezoelectric sensors may use the piezoelectric effect to measure changes in pressure, acceleration, speed, temperature, load, or force by converting them into an electrical charge, to then convert the electrical charge into the intended unit of measurement.

[0005] Background technology

[0006] For closed pipe systems, there are many different methods for measuring liquid velocity and often include primary instrumentation, such as sensor(s), mounted in a line / pipe cross-section, with cabling up to a room, or “shaft” where the equipment for signal processing is mounted. This equipment is usually available to personnel and often has the option of communicating with a more centrally located monitoring plant. Sensors are often mounted in the pipe, or are part of the pipe, and all or parts of the pipe system must be drained to access maintenance, replacement, or servicing of sensors. Sensors also require access to an external power source in order to be able to be read off and / or store and / or send measured data. There are often expensive sensors and expensive installation with demanding maintenance. Documents as RU21239, US6276218B1 and JPH1054743 describes different types of vortex meters.

[0007] The present invention solves one or more of the above stated problems.

[0008] Brief summary of the invention

[0009] The invention is defined by the independent claim 1 . Further embodiments of the invention are defined in the dependent claims. Advantages of the invention

[0010] This way of designing the liquid velocity meter provides an advantage in that the fluctuations of the sensor flag, due to the turbulence from the liquid flowing towards and around the turbulence-forming sensor housing, forms an alternating voltage signal in the piezoelectric elements and it is the voltage signal that is converted into a velocity signal for the liquid flow. This contributes to the liquid velocity meter measures with good precision, even at low liquid flow.

[0011] Brief description of figures

[0012] Examples and embodiments of the invention will be described in more detail below with reference to the accompanying figures, in which:

[0013] Figure 1 shows the liquid velocity meter 0 in an embodiment where it is seen obliquely from the front, and where the direction of stream is shown towards a first end 41 of the turbulence-forming sensor housing 4,

[0014] Figure 2 shows an embodiment of the turbulence-forming sensor housing 4 and sensor flag 1 seen from above,

[0015] Figure 3 shows an embodiment of the sensor flag 1 seen onto a side surface and where the sensor flag 1 is subdivided roughly into 3 portions: root part 9, transition part 12 and main part 11 of sensor flag 1 ,

[0016] Figure 4 shows an embodiment of the invention in section view the top part 72 and top "edge" 71 with extending I protruding sensor flag 1 as seen from above, where the two piezoelectric elements 2 are shown with an elastic, electrically insulating layer 21.

[0017] Figure 5 shows an embodiment of the root part 9 of the sensor flag 1 , where the root part 9 has a cone-shaped section that sits in the turbulence-forming sensor housing 4. Figure 6 shows an embodiment of the liquid velocity meter 0 attached to a sensor bracket 8 which is mounted in a T-branch 108 of a pipe 100. The section view is shown transverse to the pipe 100 and the T-branch 108.

[0018] Figure 7 shows a similar view as Figure 2, but with an illustration of two different frequencies (f(1), f(2)) with their associated flow rates (V(1), V(2)) and sensor flag amplitudes (A(1), A(2)).

[0019] Fig. 8 illustrates in an isometric view an embodiment of the invention the piezoelectric element 2 of the flag 1 (not shown) with a signal conditioner device 300 in the root part 9, the signal conditioner device 300 connected via short signal conductors 25 to receive analog signals from the piezoelectric elements 2, and optional signal integrator circuit 302 and frequency counter circuit 301.

[0020] Fig. 9 illustrates an edge-on view from below of a printed circuit bord with the signal conditioner I pre-amplifier device 300 and part of the piezoelectric element extending to the left.

[0021] Embodiments of the invention

[0022] The present invention provides a liquid velocity meter such as a water velocity meter, for installation in pipes, comprising a turbulence-forming transverse sensor housing where the turbulence-forming sensor housing has a triangular cross-section with a front surface facing the stream and two equal side surfaces with a top edge aligned with the stream and a sensor flag extending from the top edge, and with a root portion mounted in a top portion of the turbulence-forming sensor housing. The sensor flag has two piezoelectric elements laminated on an elastic, electrically insulating layer.

[0023] Embodiments of the mechanical structure are illustrated in Figs. 1 , 2, 3, 4, 5, 6, and 7. The invention provides a fluid velocity meter (0) for mounting in a pipe (100), please see Fig. 3, 4, 5, 6, 7, 8, and 9, all with electronic components arranged in the root part (9), the provided invention comprising

[0024] - a turbulence-forming sensor housing (4) arranged transversely in the pipe (100)

[0025] - wherein the turbulence-forming sensor housing (4) has a triangular cross-section with:

[0026] - a front surface (6) facing the stream,

[0027] - and two equal side surfaces (7) with a top part (72) with a top edge (71) opposite of said front surface (6), aligned with the stream

[0028] - a sensor flag (1) which extends in a stream direction out from the top edge (71), and with a root part (9) mounted in said top part (72) of the turbulence-forming sensor housing (4), and

[0029] - that the sensor flag (1) has two piezoelectric elements (2) laminated on an elastic, electrically insulating layer (21), wherein the root part (9) comprises;

[0030] - a signal conditioner (300) including a preamplifier (310) directly connected, or connected via short signal conductors (25), to receive analog signals from the piezoelectric elements (2), and a communication link (304), connected to the signal conditioner (300), for sending the signals further.

[0031] The preamplifier (310) is connected directly or close to the piezoelectric elements (2) to convert input signals from the piezoelectric elements into stronger output signals from the preamplifier (300), this is particularly important when the fluid velocity meter works and measures at a low fluid flow rate. The preamplifier (310) boosts the signal strength to supply the further converter circuits without significantly degrading the signal-to-noise ratio (SNR) and gives strong enough signals for further processing. In an embodiment the arrangement of the signal conditioner (300) also reduces or removes unwanted signals from the piezoelectric elements, such as noise. Without a preamplifier (310) located directly to, or near, the piezoelectric elements (2) to boost the input signals from the piezoelectric elements (2), there is a risk that the signals to be processed would be noisy or distorted. There are many different signal conditioners on the market, and in one embodiment it is used a differential charge amplifier. A communication link can involve wires, conductors, optical, modbus gateways, radio link, or any other suitable means for communication.

[0032] A signal conditioner is a device or circuit that processes and modifies an input signal to make it suitable for accurate measurement, analysis, or interfacing with other electronic systems, typically by amplifying, filtering, or converting it.

[0033] The signal conditioner (300) comprises a pre-amplifier (310).

[0034] The preamplifier (310) for an analog piezoelectric sensor (2) takes the small electrical charge generated by the sensor (2), amplifies it, and can also filter out unwanted frequencies with a passive band-pass filter, resulting in a stronger and cleaner signal that can be more accurately measured or processed by other electronics downstream (such as the reader) in a measurement or data acquisition system.

[0035] Signal Amplification: The primary function of the preamplifier (310) is to boost the very weak electrical signals generated by the piezoelectric sensor (2). When pressure or force is applied to the piezoelectric sensor, it generates electrical charges, which represents the measured physical phenomenon (e.g. vortex shedding). The signal generated from these excited charges are weak, and are not suitable to drive current across long wires.

[0036] Differential Amplification: In an embodiment of the invention the preamplifier (310) is a differential charge amplifier, which means it amplifies the difference in charge between each of the piezoelectric films (2). This helps to eliminate common-mode noise and enhances the precision of the measurement. It can also be a single-ended amplifier connected to just one of the piezoelectric films, at the cost of worse signal- to-noise ratio.

[0037] Passive Filtering: In an embodiment of the invention the preamplifier might also have passive filtering components to remove DC-components of the signal and for antialiasing. In this context, passive filtering involves the use of capacitors and resistors to selectively allow certain frequencies to pass through while attenuating others. This ensures that only the relevant signal frequencies are amplified, further improving the signal quality. In an embodiment of the invention the signal conditioner (300) comprises at least one frequency counter circuit (301), for counting the frequency of the analog signals and converting the analog signals into digital signals of the frequency.

[0038] A purpose of the frequency counter device is to convert the analog signal into a digital pulse per oscillation (sine-curve). The frequency counter can in one embodiment comprise a fourier transfomer FT. An advantage of the embodiment is that it uses less power than sending analog signals directly and has better noise resistance, i.e. it is less subject to noise in the communication link. It is better to send digital signals than analog signals with regard to distortions.

[0039] In an embodiment of the invention the signal conditioner (300) further comprises at least one signal integrator circuit (302), to integrate the frequency of the analog signals to find the energy / amplitude.

[0040] The signal integrator circuit (302) increases the accuracy of the measurements at low flow rates. The signal integrator circuit (302) generates short pulses when the integration reaches a certain threshold. The integrator circuit outputs the integral of the input signal over a frequency range based on a circuit time constant and the bandwidth of the amplifier. The input signal is applied to the inverting input so the output is inverted relative to the polarity of the input signal

[0041] In an embodiment of the invention the signal conditioner (300) further comprises a reader device (303), for processing analog or digital signals into measuring values of at least a fluid flow rate (V).

[0042] In an embodiment of the invention the reader device (303) comprises;

[0043] - at least one electrical energy source such as a battery, and

[0044] - at least one microcontroller.

[0045] The reader 303 is arranged to processes the signals from either the piezoelectric elements (2) directly, the signal conditioner (300), the frequency counter circuit (301) and / or the signal integrator circuit (302) into measuring values. The invention also provides a method for measuring flow rate of a fluid in a pipe (100), by means of a flow velocity meter (0) herein presented, wherein the method comprises the steps of: a1) installing the fluid velocity meter (0) in the pipe (100) for measuring the fluid flow rate (V), b1) sending the analog signal from the piezoelectric elements (2) to the signal conditioner (300) to strengthen the signal for further processing and to increase noise-tolerance, c1) sending the amplified signal to the reader device (300), d1) processing the signal in the reader device (300) into at least a measurement value of fluid flow rate (V).

[0046] In an embodiment of the invention the method further comprises the following steps after b1 and before c1 : b2) sending the analog signal from the preamplifier to the frequency counter circuit (301) if no previous measuring values are registered or if the latest measured fluid flow rate (V) is equal or above a given flow rate threshold, or b3) sending the analog signal from the preamplifier to the signal integrator circuit (302) if the latest measured value of fluid flow rate (V) is less than the given flow rate threshold.

[0047] In an embodiment of the invention the flow rate threshold is 3 m3 / s

[0048] In an embodiment of the invention the method further comprises the following step after d1 : e1) sending the signal from the reader (300) out of the pipe (100) via a communication link (304).

[0049] In an embodiment of the invention the elastic, electrically insulating layer is a biaxially oriented polyethylene terephthalate material. Biaxially oriented polyethylene terephthalate is a type of stretched polyester film. It is a highly elastic material, which is electrically insulating and has a high tensile strength. It is chemically stable and can act as both a gas and odor barrier. Well-known brand names such as Mylar, Melinex and Hostaphan are often used for such products. This particular type of stretched polyester film, or plastic, is perhaps better known by the abbreviation BoPET. The elastic, electrically insulating layer may extend from the root portion to near the end of the flag. Reinforced rubber or plastic may be another embodiment of the elastic, electro-insulating layer.

[0050] In another embodiment of the invention where the elastic, electrically insulating layer forms a distance between the piezoelectric elements and at the same time isolates them from each other, so that they are alternately stretched and compressed in their longitudinal directions by the sensor flag. The advantage of having two piezoelectric elements with a distance between them in the sensor flag, is to force the piezoelectric elements to alternately stretch and compress even more, so that they give off even stronger voltage signals.

[0051] In an embodiment of the invention, the sensor flag may have an elastic and insulating mantle that encloses the piezoelectric elements. This is to prevent wear and tear on the piezoelectric elements that are in the liquid stream. Another advantage of such a robust design is that the sensor flag will be maintenance-free during its lifetime, which is assumed to be 20 years. As long as the sensor flag is not damaged by foreign objects or gets any kind of undesired coating.

[0052] In a further embodiment, the mantle may be an elastic and insulating and mechanically resistant protective layer, preferably silicone. The mantle may enclose both sides of the piezoelectric elements and parts, or the whole part, of the elastic, electrically insulating layer.

[0053] In an embodiment of the invention the root part is wider than a main part of the sensor flag, with a circular segment-shaped transition part between the root part and the main part which has a contour radius. A contour radius in the transition between the root part and the main part of the sensor flag contributes to a smoother transfer of forces between the parts, and it takes more to get fatigue cracks in the transition area than with a perpendicular transition. In an embodiment of the invention the sensor flag has a bend or curvature in an outermost part of the sensor flag. The outermost end of the sensor flag is the end furthest from the turbulence-forming sensor housing. In one embodiment, there is a bend near 1 / 3 of the outermost part of the sensor flag. This is an advantage for sensor flags considering very low fluid velocities, which produce so little turbulence around the turbulence-formed sensor housing, so that sensor flag deflection / amplitude must be provoked by making a bend near the outermost part.

[0054] In another embodiment, the mantle may also include the root part and be designed to fit into the turbulence-forming sensor housing with the triangular cross-section, and fill all or parts of the turbulence-forming sensor housing, so that the sensor flag is held in the desired position, see in particular Figure 5.

[0055] In another embodiment of the invention, the sensor flag is used to measure pressure. The advantage of having two piezoelectric elements is that pressure may be measured due to capacitance between the two piezoelectric elements. Only one sensor installed in the piping system is needed to measure both flow rate and pressure. Another advantage is that the difference in pressure loss may be read between several sensors that are installed in the same closed pipe system. This may also be used to detect leaks in the pipeline network.

[0056] In an embodiment of the invention the piezoelectric element is used to generate electrical alternating voltage and thus energy. The generated energy may be used to recharge batteries, so that the energy may be stored and used later. The generated energy may, for instance, be used to send signals to an external receiver, store data and or add energy to process the voltage signals into speed and or pressure readings.

[0057] In one embodiment of the invention, the turbulence-forming sensor housing is arranged to extend diametrically in the pipe where it is arranged. The advantage of having the sensor housing diametrically is that it may be attached at both ends, so that it reduces vibrations in the turbulence-forming sensor housing. Another advantage is to avoid unwanted, unexplained turbulence of streams past the end of the triangular turbulence-forming sensor housing, turbulence frequencies that would only interfere with the more controllable conditions with the turbulence-forming sensor housing diametrically in the tube. The pipe where the turbulence-forming sensor housing is arranged may be a T-pipe, t-branch or ordinary straight pipe or curved pipe.

[0058] In another embodiment of the invention, the turbulence-forming sensor housing is arranged to extend partially diametrically in the pipe where it is arranged.

[0059] In an embodiment of the invention a first end is mounted axially in a sensor bracket held in a T-branch of a pipe where a curved inner surface is in line with the pipe wall of the pipe. This is to achieve the same diameter around where the liquid velocity meter is arranged in the T-branch, as in the pipe where the T-branch is connected to. That again to measure the same volume flow past the turbulence-forming sensor housing in the T-branch, as if it were mounted in the pipe itself. The advantage is that one end of the T-branch may be equipped with a flange, so that there is access to the sensor bracket and the turbulence-forming sensor housing via the T-branch. This provides quick access to fluid velocity sensors for repair, maintenance, or replacement.

[0060] In an embodiment of the invention the sensor bracket is designed to be pulled out and pushed in again. This is to be able to carry out replacements and maintenance on the liquid velocity meter. By installing the T-branch between two shut-off valves, maintenance or replacement of the turbulence-forming sensor housing may be done by blinding off the T-branch for a shorter period. It may also be possible to install a third shut-off valve, in connection with the sensor bracket, so that the entire sensor bracket may be lifted out of the pipe system and blinded off without having to shut off the liquid stream.

[0061] In another embodiment of the invention the T-branch has a diameter corresponding to the pipe. In another embodiment of the invention the T-branch has a smaller diameter than the Pipe.

[0062] In an embodiment of the invention the turbulence-forming sensor housing is reversible about its longitudinal axis, so that the flag can be turned with the stream direction in the pipe. This has an advantage if the stream direction reverses, so that the sensor with the flag may be rotated about its own axis to stand with the front face facing the stream direction again.

[0063] In an embodiment of the invention the turbulence-forming sensor housing detects that the stream direction is turning. In pipe systems that are interconnected as a ring, the stream direction may change several times within a short period, and it would then be an advantage if this is detected.

[0064] An embodiment of the invention the sensor bracket is arranged to rotate 180 degrees about its axis. Where the turbulence-formed sensor housing, which is fixed in the sensor bracket, may be turned 180 degrees if the stream direction in the pipe reverses.

[0065] The invention in an embodiment the sensor bracket has motorized rotation. Where the sensor flag turns and becomes static - is turned / rotated by a motor. When turning by an electric motor or hydraulic motor with an electric pump, the energy used may come from a battery or several batteries, which again get all or some of the charge from the electrical energy produced by the piezoelectric elements.

[0066] The invention in an embodiment where the sensor flag has piezoelectric elements that are used as an acoustic microphone to pick up sound in order to detect leaks. By having several such sensors with microphones placed over a pipeline network, in addition to detecting leaks, it is also possible to identify the location within which pair of sensors the leak is located. The invention in one embodiment where the liquid velocity meter is calibrated for the type of liquid it is installed in. Another embodiment is that the liquid velocity meter is calibrated in a liquid with a corresponding viscosity to the liquid in which it is to be installed.

[0067] The invention in an embodiment where the liquid velocity meter is calibrated for the type of pipe dimension in which it is installed. In a further embodiment, the liquid velocity meter may include electronics with software that includes algorithms to adapt the liquid velocity meter to the pipe dimension in which the liquid velocity meter is to be installed.

[0068] The liquid velocity meter may have a design that allows calibration to take place manually, remotely and or automatically. An advantage of remote calibration is that the sensor may be re-calibrated by an inner reduction of the pipe. Reduction of the inner pipe diameter may occur when a fouling is formed.

[0069] In one embodiment of the invention, the alternating voltage signal may be taken out over signal conductors, which may extend to a room, a shaft or in a T-branch, where the voltage signal may be measured, stored and or converted to output the fluid velocity.

[0070] In one embodiment of the invention, the liquid velocity meter may be used in liquid- filled pipes.

[0071] Detailed description of embodiments of the invention

[0072] Figures 0 - 9 show one or more embodiments of a liquid velocity meter according to the present invention.

[0073] The invention provides a fluid velocity meter (0) for mounting in a pipe (100), please see Fig. 3, 4, 5, 6, 7, 8, and 9, all with electronic components arranged in the root part (9), the provided invention comprising

[0074] - a turbulence-forming sensor housing (4) arranged transversely in the pipe (100) - wherein the turbulence-forming sensor housing (4) has a triangular cross-section with:

[0075] - a front surface (6) facing the stream,

[0076] - and two equal side surfaces (7) with a top part (72) with a top edge (71) opposite of said front surface (6), aligned with the stream

[0077] - a sensor flag (1) which extends in a stream direction out from the top edge (71), and with a root part (9) mounted in said top part (72) of the turbulence-forming sensor housing (4), and

[0078] - that the sensor flag (1) has two piezoelectric elements (2) laminated on an elastic, electrically insulating layer (21), wherein the root part (9) comprises;

[0079] - a signal conditioner (300) directly connected, or connected via short signal conductors (25), to receive analog signals from the piezoelectric elements (2), and a communication link (304), connected to the signal conditioner (300), for sending the signals further.

[0080] The signal conditioner (300) is connected directly or close to the piezoelectric elements 2 to convert input signals from the piezoelectric elements into stronger output signals from the preamplifier (300), this is particularly important when the fluid velocity meter works and measures at a low fluid flow rate. The signal conditioner (300) boosts the signal strength to supply the further converter circuits without significantly degrading the signal-to-noise ratio (SNR) and gives strong enough signals for further processing. The arrangement of the signal conditioner (300) also reduces or removes unwanted signals from the piezoelectric elements, such as noise. Without a preamplifier located directly to, or near, the piezoelectric elements to boost the input signals from the piezoelectric elements, there is a risk that the signals to be processed would be noisy or distorted. There are many different signal conditioners on the market, and in one embodiment it is used a differential charge amplifier. A communication link can involve wires, conductors, optical, modbus gateways, radio link, or any other suitable means for communication. In an embodiment of the invention the signal conditioner (300) comprises at least one frequency counter circuit (301), for counting the frequency of the analog signals and converting the analog signals into digital signals of the frequency.

[0081] A purpose of the frequency counter device is to convert the analog signal into a digital pulse per oscillation (sine-curve). The frequency counter can in one embodiment be a fourier transfomer FT. An advantage of the embodiment is that it uses less power than sending analog signals directly and has better noise resistance, i.e. it is less subject to noise in the communication link. It is better to send digital signals than analog signals with regard to distortions.

[0082] The frequency counter circuit (301) in an embodiment of the invention comprises "signal to pulse converter”. A main purpose of the signal to pulse converter is converting an analog signal, often a sine wave or any waveform with varying frequency, into a series of pulses where the width or duration of each pulse is proportional to the frequency of the input signal. The primary function of a signal-to- pulse converter is to measure the frequency of the input analog signal. It does this by counting the number of cycles (periods) of the input signal within a specific time window. The converter generates a series of output pulses, where each pulse represents a specific number of cycles of the input signal that occurred during a predetermined time interval. The width of each pulse is directly related to the frequency of the input signal. Higher input frequencies result in narrower pulses, and lower frequencies result in wider pulses.

[0083] In an embodiment of the invention, for most accurate measurements, the signal converter should use the output signal from the preamplifier, but can also use signals from one of the piezoelectric films directly.

[0084] The primary benefit of the signal to pulse converter is to allow low-energy frequency measurements, as an alternative to more energy-demanding signal processing techniques, such as Fourier transforms.

[0085] In an embodiment of the invention the signal conditioner (300) further comprises;

[0086] - at least one signal integrator circuit (302), to integrate the frequency of the analog signals to find the energy / amplitude.

[0087] The signal integrator circuit (302) increases the accuracy of the measurements at low flow rates. The signal integrator circuit (302) generates short pulses when the integration reaches a certain threshold. The integrator circuit outputs the integral of the input signal over a frequency range based on a circuit time constant and the bandwidth of the amplifier. The input signal is applied to the inverting input so the output is inverted relative to the polarity of the input signal.

[0088] In an embodeiment of the invention the signal integrator circuit (302) comprises a circuit or device that serves the purpose of relating the amplitude (peak-to-peak voltage) of an input analog signal into a series of pulses, where the pulse width or duration of each pulse is proportional to the amplitude of the input signal.

[0089] Such a circuit can for instance comprise the following components: An absolute value circuit, into a voltage integrator, into a comparator that resets the integrator.

[0090] For the most accurate measurements, the circuit should use the output from the preamplifier, but can also use the signals from one of the piezoelectric films directly at the cost of worse accuracy.

[0091] It can alternatively be one of the following:

[0092] - An absolute value circuit into a peak detector.

[0093] - An absolute value circuit into a power analyzer.

[0094] The primary benefit of this circuit is to allow accurate low-energy amplitude measurements.

[0095] In an embodiment of the invention the signal conditioner (300) further comprises a reader device (303), for processing analog or digital signals into measuring values of at least a fluid flow rate (V).

[0096] In an embodiment of the invention where the reader device (303) comprises;

[0097] - at least one electrical energy source such as a battery, and

[0098] - at least one microcontroller.

[0099] In an embodiment of the invention the reader device (303) may also be arranged as a gateway: Modem, antenna.

[0100] In an embodiment frequency counting may be used for fluid velocities over 0.1 m / s, amplitude (3) for low fluid velocities.

[0101] The reader 303 is arranged to processes the signals from either the piezoelectric elements (2) directly, the signal conditioner (300), the frequency counter circuit (301) and / or the signal integrator circuit (302) into measuring values. The invention also provides a method for measuring flow rate of a fluid in a pipe (100), by means of a flow velocity meter (0) herein presented, wherein the method comprises the steps of: a1) installing the fluid velocity meter (0) in the pipe (100) for measuring the fluid flow rate (V), b1) sending the analog signal from the piezoelectric elements (2) to the signal conditioner (300) to strengthen the signal for further processing and to increase noise-tolerance, c1) sending the amplified signal to the reader device (300), d1) processing the signal in the reader device (300) into at least a measurement value of fluid flow rate (V).

[0102] In an embodiment of the invention the method further comprises the following steps after b1 and before c1 : b2) sending the analog signal from the preamplifier to the frequency counter circuit (301) if no previous measuring values are registered or if the latest measured fluid flow rate (V) is equal or above a given flow rate threshold, or b3) sending the analog signal from the preamplifier to the signal integrator circuit (302) if the latest measured value of fluid flow rate (V) is less than the given flow rate threshold.

[0103] In an embodiment of the invention the flow rate threshold is 3 m3 / s

[0104] In an embodiment of the invention the method further comprises the following step after d1 : e1) sending the signal from the reader (300) out of the pipe (100) via a communication link (304).

[0105] Figure 1 illustrates an embodiment of the liquid velocity meter 0 with a turbulenceforming sensor housing 4. The turbulence-forming sensor housing 4 has a front surface 6, which is to face the stream direction co. In an embodiment the front surface 6 has a mounting port 42. The mounting port 42 is arranged so that it is possible to carry out maintenance and I or replacements of components such as sensor flag 1, signal conductor(s) 25, root part 9 and / or piezoelectric element 2. The turbulence-forming sensor housing has two equal side surfaces 7, which extend from the front plate and obliquely backwards to the transition part with a contour radius R1, 12, so that sensor flag 1 is perpendicularly mounted and backwards on the front plate 6 when stationary. The figure further shows a mounting stem 5 on top of the turbulence-forming sensor housing. The mounting stem 5 is also shown with two signal conductors 25 which are connected to the piezoelectric elements 2. There is also shown in the Figure an option to have an additional mounting stem at the bottom of the turbulence-forming sensor housing 4 or only mounting stem 5 at the bottom . If there is only one mounting stem at the bottom, the signal conductors 25 must pass through the mounting stem 5 at the bottom of the turbulence-forming sensor housing 4. The figure shows the sensor flag 1 shaped with a circular segment-shaped transition part 12 with a contour radius R1 from a root part 9 to the sensor flag 1. Furthermore, the figure shows the sensor flag 1 with a flag end radius R2. The sensor flag 1 is also shown with the two piezoelectric elements 2 and how they are mounted inside the sensor flag 1 on each side and with one space, and which are each connected to a separate signal conductor 25. The turbulence-forming sensor housing 4 is shown with a top edge 71 and a top part 72 of the turbulenceforming sensor housing 4. Such a design may be symmetrical about the horizontal center of the turbulence-forming sensor housing 4. Figure 1 further shows a sensor flag displacement / amplitude A, which occurs when a fluid flow with stream direction co hits the turbulence-forming sensor housing 4, so that the two piezoelectric elements 2 which are mounted in the sensor flag will receive tensile and compressive stress in turn (this is shown in more detail in Figure 7). The alternating voltage signal is taken out over signal conductors 25 and the voltage signal is measured and converted to output fluid velocity.

[0106] In Figure 2, we see an embodiment of the liquid velocity meter seen from above and downwards on the turbulence-forming sensor housing 4 with a triangular crosssection. Here, in outline, shown with a front surface 6, two side surfaces 7, a sensor flag 1. The figure also shows the mounting stem 5, mounted on top of the turbulence-forming sensor housing 4 and with two signal conductors 25 pulled through. The turbulence-forming sensor housing 4 is shown with a top part 72 of the turbulence-forming sensor housing 4 and a top edge 71 . The sensor flag 1 is indicated with two piezoelectric elements 2, which are installed inside the sensor flag 1. The sensor flag 1 is also shown with a root part 9 arranged inside it the turbulence-forming sensor housing 4. The stream direction co is shown by the Figure perpendicular to the turbulence-forming sensor housing 4 and the sensor flag 1 is shown with a sensor flag displacement / amplitude A.

[0107] In Figure 3 we see a more descriptive part of an embodiment of the sensor flag 1 . Figure 3 shows an embodiment of the sensor flag 1 divided into three parts, wherein

[0108] - there is a root part 9 which may extend from the beginning of the sensor flag 1 to

[0109] - a circular segment-shaped transition part 12 with a contour radius R1 , which extends further to

[0110] - a main part 11 of the sensor flag 1 and which ends with a flag end radius R2. Figure 3 shows further an embodiment of the sensor flag 1 with a mantle 22 and where the mantle 22 may be a silicone mantle 220. The Figure also shows an embodiment of how the mantle 22 may encapsulate the two piezoelectric elements 2 and the signal conductors 25.

[0111] Figure 4 shows an embodiment of sensor flag 1 which has two piezoelectric elements 2 laminated on an elastic, electrically insulating layer 21. The figure also shows an alternative embodiment where the elastic, electrically insulating layer 21 is a biaxially oriented polyethylene terephthalate material 210. The figure shows further, the sensor flag 1 with a root part 9 that extends between the two side surfaces 7 of the turbulence-forming sensor housing 4 and how the signal conductors may be drawn up and or down and through the dotted indication of a mounting stem 5. The figure shows a mantle 22 that encloses and encapsulates the two piezoelectric elements 2, the elastic, electrically insulating layer 21 and the signal conductors 25 through the turbulence-forming sensor housing 4. The figure also shows an embodiment where the main part 11 of the sensor flag 1 has a horizontal flag radius R4. An embodiment of how the sensor flag 1 is divided into three main parts, with a root part 9, a circular segment-shaped transition part 12 and a main part 11 of sensor flag 1 is also shown in the figure. Figure 5 shows an embodiment of the root part 9, and where the root part 9 fills the triangular-shaped cavity 44 in the turbulence-forming sensor housing 4. The triangular-shaped cavity in the turbulence-forming sensor housing 4 is designed so that the sensor flag 1 can be changed, in its entirety, out through mounting port 42, by removing the cover 43 for mounting port 42. The signal conductors 25 may thus be drawn out from the mounting stem 5, so that a new sensor flag 1 with signal conductors 25 may be mounted in the turbulence-forming sensor housing 4.

[0112] In Figure 6, we see an embodiment of the turbulence-forming sensor housing 4 installed in a T-branch connected to a pipe 100. The figure also shows the turbulence-forming sensor housing 4 with a mounting stem 5, which is mounted in a sensor bracket 8. The figure also shows a signal conductor 25 which comes from the turbulence-formed sensor housing 4 and up via the mounting stem 5. The figure shows that the signal conductor 25 stops in the bracket, but another embodiment could be that the signal conductor 25 continues out of the T-branch 108 through the flange at the top. It is also clear from the figure how the sensor bracket 8 with its curved inner surface 81 is placed down into a pipe 100 via a T-branch 108. The figure also shows how pipe wall 101 in the T-branch 108 and the curved inner surface 81 of the sensor bracket 8 form a corresponding diameter as the pipe 100. Furthermore, we can see from the Figure that the entire sensor bracket 8 may be pushed out of the T-branch 108, so that repairs, maintenance and or replacements may be carried out. It is also shown in the Figure that an axis 30 which the sensor bracket 8 may be rotated around, in order to have the first end 41 of the turbulenceforming sensor housing 4 facing the stream direction, if it were to turn. Another embodiment is if only the turbulence-forming sensor housing 4 is rotated about its longitudinal axis. The rotation of the sensor bracket 8 and or the turbulence-forming sensor housing 4 may be done manually, with the help of a motor, an accumulator of some kind, and or that it is rotated automatically by changing the stream direction, so that the first end 41 of the turbulence-forming sensor housing 4 is always directed against the stream direction. Figure 7 shows an embodiment of the sensor flag 1 , seen from above, where the sensor flag 1 is illustrated with two different frequencies (f(1) and f(2)), and with associated two different flow rates (V(1) and V(2)), of which f(1)<f(2) and V(1)<V(2). The figure also shows how the curvature of the sensor flag 1 shifts towards the end of the sensor flag 1 with increasing frequency. Alternating curvatures of the sensor flag 1 contribute to the alternating stretching and contraction of the piezoelectric elements 2 installed in the sensor flag 1. The figure also shows turbulence around the turbulence-forming sensor housing at the side surfaces 7.

[0113] Reference table:

Claims

Claims1. A fluid velocity meter (0) for mounting in a pipe (100), comprising- a turbulence-forming sensor housing (4) arranged transversely in the pipe (100)- wherein the turbulence-forming sensor housing (4) has a triangular cross-section with:- a front surface (6) facing the stream,- and two equal side surfaces (7) with a top part (72) with a top edge (71) opposite of said front surface (6), aligned with the stream characterized by- a sensor flag (1) which extends in a stream direction out from the top edge (71), and with a root part (9) mounted in said top part (72) of the turbulence-forming sensor housing (4), and- that the sensor flag (1) has two piezoelectric elements (2) laminated on an elastic, electrically insulating layer (21), wherein the root part (9) comprises;- a signal conditioner (300) including a preamplifier (310) directly connected, or connected via short signal conductors (25), to receive analog signals from the piezoelectric elements (2), and- a communication link (304), connected to the signal conditioner (300), for sending the signals further.

2. The fluid velocity meter (0) according to claim 1 , where the signal conditioner (300) further comprises;- at least one frequency counter circuit (301), for counting the frequency of the analog signals and converting the analog signals into digital signals of the frequency.

3. The fluid velocity meter (0) according to claim 1 or 2 , where the signal conditioner (300) further comprises;- at least one signal integrator circuit (302), to integrate the frequency of the analog signals to find the energy / amplitude.

4. The fluid velocity meter (0) according to claim 1 , 2 or 3, where the signal conditioner (300) further comprises;- a reader device (303), for processing analog or digital signals into measuring values of at least a fluid flow rate (V).

5. The fluid velocity meter (0) according to claim 4, where the reader device (303) comprises;- at least one electrical energy source , and- at least one microcontroller.

6. A method for measuring flow rate of a fluid in a pipe (100), by means of a flow velocity meter (0) according to one of the claims 1-5, characterized in that the method comprises following steps: a1) installing the fluid velocity meter (0) in a pipe (100) for measuring the fluid flow rate (V), b1) sending the analog signal from the piezoelectric elements (2) to the signal conditioner (300) to strengthen the signal for further processing and to increase noise-tolerance, c1) sending the amplified signal to the reader device (303), d1) processing the signal in the reader device (303) into at least a measurement value of fluid flow rate (V).

7. The method according to claim 6, characterized in that the method further comprises the following steps after b1 and before c1 : b2) sending the analog signal from the preamplifier to the frequency counter circuit(301) if none previous measuring values are registered or if the latest measured fluid flow rate (V) is equal or above a given threshold b3) sending the analog signal from the preamplifier to the signal integrator circuit(302) if the latest measured value of fluid flow rate (V) is less than a given threshold.

8. The method according to claim 6 or 7, characterized in that the method further comprises the following step after d1 : e1) sending the signal from the reader (300) out of the pipe (100) via a communication link (304).

9. The liquid velocity meter (0) according to any of the preceding claims, wherein the elastic, electrically insulating layer (21) is a biaxially oriented polyethylene terephthalate material (210).

10. The liquid velocity meter (0) according to claim 9, wherein the sensor flag (1) has an elastic and insulated mantle (22) which encloses the piezoelectric elements (2).

11. The liquid velocity meter (0) according to any of the preceding claims, wherein the root part (9) is wider than a main part (11) of the sensor flag (1), with a circular segment-shaped transition part (12) between the root part (9) and the main part (11) which has a contour radius (R1).

12. The liquid velocity meter (0) according to any of the preceding claims, wherein the sensor flag (1) is used to measure pressure (P).

13. The liquid velocity meter (0) according to any of the preceding claims, wherein the piezoelectric element (1) also is used to generate electrical alternating voltage and thus energy.

14. The liquid velocity meters (0) according to any of the preceding claims, wherein the turbulence-forming sensor housing (4) is arranged to extend diametrically in the pipe (100) where it is arranged.

15. The fluid velocity meter (0) according to any of the preceding claims, wherein a first end (41) is mounted axially in a sensor bracket (8) held in a T-branch (108) of the pipe (100), where a curved inner surface (81) is in line with the pipe wall (101) of the pipe (100).

16. The liquid velocity meter (0) according to any of the preceding claims, wherein the sensor bracket (8) is designed to be pulled out and pushed in again for repair or replacement.

17. The liquid velocity meter (0) according to any of the preceding claims, wherein the T-branch (108) has a diameter corresponding to the pipe (100).

18. The liquid velocity meter (0) according to any of the preceding claims, wherein , where the T-branch (108) has a smaller diameter than the pipe (100).

19. The liquid velocity meter (0) according to any of the preceding claims, wherein the turbulence-forming sensor housing (4) is reversible about its longitudinal axis, so that the flag (1) can be turned with the liquid flow in the pipe (100).

20. The liquid velocity meter (0) according to any of the preceding claims, wherein the sensor bracket (8) is arranged to rotate 180 degrees about its axis (30)21 . The liquid velocity meter (0) according to any of the preceding claims, wherein the sensor bracket (8) has motorized rotation.

22. The liquid velocity meter (0) according to any of the preceding claims, wherein the sensor flag (1) piezoelectric elements (2) are used as an acoustic microphone to pick up sounds to detect leaks.

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