Mass flow meter / controller and method with improved accuracy

Abstract

The disclosed mass flow meter / controller includes a flow tube for directing fluid from an inlet of the flow tube to an outlet of the flow tube, an actuator for inducing vibrations within the flow tube, a light source for emitting light, at least one beam splitter for splitting the light emitted by the light source into a first light beam and a second light beam, a first light sensor for outputting a first measurement value at a first position at a first location on the flow tube based on detection of the first light beam, a second light sensor for outputting a second measurement value at a second position at a second location on the flow tube based on detection of the second light beam, and control circuitry for determining a mass flow rate and / or a density of fluid within the flow tube based on the first and second measurements.

Description

[Technical Field]

[0001] [Related Applications] This application claims the benefit of U.S. Patent Application No. 16 / 870,147, filed May 8, 2020, entitled "MASS FLOW METERS / CONTROLLERS AND METHODS HAVING IMPROVED ACCURACY," the entirety of which is expressly incorporated herein by reference.

[0002] This disclosure relates generally to mass flow measurement and control, and more particularly to mass flow meters / controllers and methods with improved accuracy. [Background technology]

[0003] Mass flow meters based on the Coriolis effect measure the mass flow rate of a medium by determining the phase difference between different portions of a flow tube through which the medium flows. Summary of the Invention

[0004] A mass flow meter / controller with improved accuracy is substantially as illustrated by and described in connection with at least one of the drawings, and as more fully set forth in the claims. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic diagram of an exemplary mass flow meter / controller according to aspects of the present disclosure.

[0006] [Figure 2] 2 is a schematic diagram of an exemplary embodiment of the mass flow meter / controller of FIG. 1 in which a single light source provides multiple light beams that are detected by multiple light sensors.

[0007] [Figure 3]FIG. 2 is a schematic diagram of an exemplary embodiment of the mass flow meter / controller of FIG. 1 including one or more beam splitters that split the light output by a single light source into multiple light beams that are detected by multiple light sensors.

[0008] [Figure 4] 2 is a schematic diagram of an exemplary embodiment of the mass flow meter / controller of FIG. 1 including one or more beam splitters that split the light output by a single light source into multiple light beams that are detected by multiple light sensors, the split light beams having the same direction as the light source.

[0009] [Figure 5] 2 is a schematic diagram of an exemplary embodiment of the mass flow meter / controller of FIG. 1 including one or more beam splitters that split the light output by a single light source into multiple light beams that are detected by multiple light sensors, the split light beams having a direction opposite to that of the light source.

[0010] [Figure 6] 3 is a flowchart illustrating an exemplary method that may be performed by the mass flow meter / controller of FIG. 2 to measure mass flow rate and / or fluid density and / or control mass flow rate. DETAILED DESCRIPTION OF THE INVENTION

[0011] The drawings are not necessarily to scale. Where appropriate, like or identical reference numerals are used to refer to like or identical components.

[0012] The accuracy of mass flow measurement depends on the quality of the signal output by the optical sensor. In conventional optical sensors in Coriolis mass flow meters, separate light sources (e.g., channels) provide the light beams measured by each optical sensor. Optical sensors in conventional configurations output signals that include a DC bias signal and an AC signal due to modulation of the flow tube. In conventional mass flow meters with multiple optical channels, where each optical channel includes a light source, a light source control circuit, and a light sensor, each component of a given channel also generates noise, which contributes to the overall optical channel output signal. For example, each optical channel may include a photosensor noise signal due to the light source control circuit, a photosensor noise signal due to the light source, and an AC noise signal due to the photosensor.

[0013] Because the noise sources mentioned above are uncorrelated random noise, these noise signals cannot be compensated for and can adversely affect flow meter accuracy in conventional flow meters. Thus, for a conventional mass flow meter with two separate channels, there are at least six independent variables that contribute some noise to the overall phase shift value.

[0014] The disclosed example mass flow meter / controllers increase accuracy by reducing the number of independent noise sources in the mass flow measurement. In some disclosed examples, one or more beam splitters split a single light source for use by multiple channels and direct the resulting light beam across different locations on the flow tube to measure the phase difference between those locations.

[0015] An exemplary mass flow meter / controller disclosed includes a flow tube configured to direct fluid from an inlet of the flow tube to an outlet of the flow tube; an actuator configured to induce vibrations within the flow tube; a light source configured to emit light; at least one beam splitter configured to split the light emitted by the light source into a first light beam and a second light beam; a first light sensor configured to output a first measurement value at a first position at a first location on the flow tube based on detection of the first light beam; a second light sensor configured to output a second measurement value at a second position at a second location on the flow tube based on detection of the second light beam; and control circuitry configured to determine at least one of a mass flow rate through the flow tube or a density of a fluid in the flow tube based on the first measurement value and the second measurement value.

[0016] In some exemplary mass flow meter / controllers, at least one beam splitter is configured to direct the first and second light beams in opposite directions, and the first and second light sensors are positioned on opposite sides of the at least one beam splitter to receive the first and second light beams, respectively, from the at least one beam splitter. In some examples, the at least one beam splitter includes a first mirror positioned at a substantially 45-degree angle with respect to the light source to reflect a first portion of the light from the light source to form the first light beam, and a second mirror positioned to reflect a second portion of the light from the light source that passes through the first mirror back toward the first mirror. The first mirror is configured to reflect the second portion of the light from the second mirror to form the second light beam.

[0017] In some exemplary mass flow meter / controllers, the at least one beam splitter further comprises a third mirror configured to reflect the first light beam from the first mirror to the first light sensor and a fourth mirror configured to reflect the second light beam from the first mirror to the second light sensor. Some exemplary mass flow meter / controllers further comprise a printed circuit board, and the first light sensor and the second light sensor are mounted on the printed circuit board. In some exemplary mass flow meter / controllers, the printed circuit board is configured to thermally couple the first light sensor and the second light sensor. In some exemplary mass flow meter / controllers, a light source is mounted on the printed circuit board and thermally coupled to the first light sensor and the second light sensor.

[0018] In some example mass flow meter / controllers, the first location of the flow tube, the second location of the flow tube, and a portion of the flow tube between the first and second locations are oriented in a two-dimensional plane, and the actuator is configured to induce vibrations in the flow tube in a direction along the two-dimensional plane. In some example mass flow meter / controllers, the first location of the flow tube, the second location of the flow tube, and a portion of the flow tube between the first and second locations are oriented in a two-dimensional plane, and the actuator is configured to induce vibrations in the flow tube in a direction transverse to the two-dimensional plane.

[0019] In some exemplary mass flow meter / controllers, the at least one beam splitter includes at least one of a cube beam splitter, a plate beam splitter, a pellicle beam splitter, a Wollaston prism, a diffractive beam splitter, an actuating beam splitter, or a fused fiber beam splitter. In some exemplary mass flow meter / controllers, the actuator includes a drive coil configured to actuate the flow tube via a magnet attached to the flow tube. Some exemplary mass flow meter / controllers further include a flow control valve configured to control the flow of fluid through the flow tube, and the control circuitry configured to control the flow control valve based on the determined mass flow rate.

[0020] An exemplary method disclosed involves directing fluid from an inlet to an outlet of the flow tube, inducing vibrations in the flow tube via an actuator, emitting light from a light source, splitting the light emitted from the light source into a first light beam and a second light beam via at least one beam splitter, outputting a first measurement of a first position at a first location on the flow tube via a first light sensor based on detection of the first light beam, outputting a second measurement of a second position at a second location on the flow tube via a second light sensor based on detection of the second light beam, and determining at least one of a mass flow rate through the flow tube or a density of the fluid in the flow tube via control circuitry based on the first measurement and the second measurement.

[0021] In some example methods, splitting the light via at least one beam splitter involves reflecting a first portion of the light from the light source via a first mirror positioned at a substantially 45 degree angle relative to the light source to form a first light beam, reflecting a second portion of the light from the light source that passes through the first mirror back towards the first mirror via a second mirror, and reflecting the second portion of the light from the light source via the first mirror to form a second light beam.

[0022] Some example methods further include directing the first light beam and the second light beam in opposite directions. Some example methods further include reflecting the first light beam via a first mirror to a first light sensor via a second mirror and reflecting the second light beam reflected via the first mirror to a second light sensor. Some example methods further include thermally coupling the first light sensor and the second light sensor. Some example methods further include thermally coupling a light source to the first light sensor and the second light sensor.

[0023] In some examples, splitting the light involves splitting the light using at least one of a cube beam splitter, a plate beam splitter, a pellicle beam splitter, a Wollaston prism, a diffractive beam splitter, an actuating beam splitter, or a fused fiber beam splitter. In some example methods, inducing vibration in the flow tube includes actuating the flow tube via a magnet and a drive coil.

[0024] Figure 1 is a schematic diagram of an example mass flow meter / controller 100. The example mass flow meter / controller 100 of Figure 1 can be used to measure the mass flow rate and / or density of a fluid passing through a conduit connected in series with the mass flow meter / controller 100 and / or to control a valve to control the mass flow rate of a fluid passing through the conduit.

[0025] The example mass flow meter / controller 100 includes a flow base 102, a flow tube 104, a fluid inlet 106, and a fluid outlet 108. The flow tube 104 directs fluid from the fluid inlet 106 to the fluid outlet 108. To measure the mass flow rate and / or density of the fluid flowing through the flow tube 104, the example mass flow meter / controller 100 includes a plurality of optical sensors 110, 112 (also referred to herein as "photo sensors"), an actuator (e.g., a permanent magnet 114 and a drive coil 116) that induces vibrations in the flow tube 104, and control circuitry 122. To reduce measurement errors, the example mass flow meter / controller 100 further includes a temperature sensor 126.

[0026] The flow tube 104 is configured in a U-shape. The drive coil 116 generates an alternating magnetic field, which generates a driving force on the permanent magnet 114. The permanent magnet 114 is attached to the flow tube 104 and transmits the driving force to the flow tube 104, causing vibration within the flow tube 104. The flow tube 104 vibrates at a certain frequency, and the control circuitry 122 can control the drive coil 116 to approximate the vibration frequency to the natural frequency of the flow tube 104. The movement of the medium (e.g., gas or liquid) inside the flow tube 104 generates a Coriolis force, which causes a phase shift between a first location 118 on the flow tube 104 upstream of the actuator and a second location 120 on the flow tube 104 downstream of the actuator. The optical sensors 110, 112 measure the position of the flow tube 104 at the first location 118 and the second location 120 and output respective signals (e.g., measurements) having the same frequency but with a phase or time difference.

[0027] The example control circuitry 122 determines the mass flow rate through the flow conduit 104 and / or the density of the fluid within the flow conduit 104 based on the first measurement from the optical sensor 110 and the second measurement from the optical sensor 112. In some examples, the control circuitry 122 controls the mass flow rate through the flow conduit 104 using a flow control valve 124. The control circuitry 122 can control the flow control valve 124 based on a comparison of the desired flow rate to the measured flow rate and can include one or more control loops, such as a proportional-integral-derivative (PID) controller and / or filters.

[0028] The example control circuitry 122 of FIG. 1 may be a general purpose computer, a laptop computer, a tablet computer, a mobile device, a server, an embedded device, and / or any other type of computing device.

[0029] The example control circuitry 122 of FIG. 1 includes a processor 132. The example processor 132 may be any general-purpose central processing unit (CPU) from any manufacturer. In some other examples, the processor 132 may include one or more special-purpose processing units, such as a graphics processing unit and / or a digital signal processor. The processor 132 executes machine-readable instructions 134. The machine-readable instructions 134 may be stored locally to the processor (e.g., in an internal cache), in random access memory 136 (or other volatile memory), in read-only memory 138 (or other non-volatile memory, such as flash memory), and / or in a mass storage device 140. The example mass storage device 140 may be a hard drive, a solid-state storage device, a hybrid drive, a RAID array, and / or any other mass data storage device.

[0030] The bus 142 allows communication between the processor 132 , the RAM 136 , the ROM 138 , the mass storage device 140 , the network interface 144 , and / or the input / output interface 146 .

[0031] The example network interface 144 includes hardware, firmware, and / or software that connects the control circuitry 122 to a communications network 148, such as the Internet. For example, the network interface 144 may include wireless and / or wired communications that comply with IEEE 802.X for transmitting and / or receiving communications.

[0032] Example control circuitry 122 can access non-transitory machine-readable medium 152 via I / O interface 146 and / or I / O device(s) 150. Examples of machine-readable medium 152 in Figure 1 include optical disks (e.g., compact discs (CDs), digital versatile / video discs (DVDs), Blu-ray® discs, etc.), magnetic media (e.g., floppy disks), portable storage media (e.g., portable flash drives, Secure Digital (SD) cards, etc.), and / or any other type of removable and / or installable machine-readable medium.

[0033] To determine the mass flow rate, the example control circuitry 122 can use the mass flow rate equation shown below in Equation 1: MF=FCF*Δt (Equation 1)

[0034] In Equation 1, MF is the mass flow rate (e.g., kilograms per second (kg / s)), FCF is the flow calibration factor, which is a constant for a particular device (e.g., based on calibration), Δt=θ / 2πF′, where θ is the phase difference between the output signals from the optical sensors 110, 112, and F is the natural frequency of the flow tube 104.

[0035] Figure 2 is a schematic diagram of an exemplary embodiment of the mass flow meter / controller 100 of Figure 1 in which a single light source 202 (e.g., an LED) provides multiple light beams 204, 206 that are detected by the light sensors 110, 112. The light source 202 is controlled by a light source controller 208. By reducing the light source to one, the example of Figure 2 reduces the number of independent noise or error sources in the measurement and increases the accuracy of the mass flow and / or density measurement(s). The light sensors 110, 112 output resulting signals to respective amplifiers 210, 212, which may be implemented within the control circuitry 122 of Figure 1.

[0036] The light source 202 can be configured to emit light in multiple directions to direct multiple light beams 204, 206 from the same light source 202 to two different light sensors 110, 112, allowing the light sensors 110, 112 to measure vibrations of the flow tube 104 via the light beams 204, 206. Additionally or alternatively, as described in more detail below, the mass flow meter / controller can include one or more beam splitters and / or the light sensors 110, 112 can be configured to output measurements of the positions of the first location 118 and the second location 120 on the flow tube 104 based on detection of multiple light beams generated using the single light source 202.

[0037] FIG. 3 is a schematic diagram of another exemplary embodiment of the mass flow meter / controller 100 of FIG. 1 that includes a beam splitter 302 that splits light 304 output by a single light source 306 into multiple light beams 308, 310 that are detected by the light sensors 110, 112.

[0038] 3 includes a first mirror 312 oriented at a 45-degree angle relative to light 304 from light source 306. The first mirror 312 reflects a first portion of the light 304 from light source 306 to form a first light beam 308 and directs the first light beam 308 toward a first light sensor 110. A first location 118 on flow tube 104 is positioned between the first mirror 312 and the light sensor 110 such that the first location 118 on flow tube 104 blocks a portion of the first light beam 308 based on vibrations of flow tube 104.

[0039] The beam splitter 302 includes a second mirror 314 that reflects a second portion 316 of the light 304 from the light source 306 that passes through the first mirror 312 back toward the first mirror. The first mirror 312 reflects the second portion of the light from the second mirror 314 to form a second light beam 310 and directs the second light beam 310 toward the second light sensor 112. The second location 120 on the flow tube 104 is positioned between the first mirror 312 and the light sensor 112 such that the second location 120 on the flow tube 104 intercepts a portion of the second light beam 310 based on vibrations of the flow tube 104.

[0040] The beam splitters (e.g., mirrors 312, 314) are configured to direct the first light beam 308 and the second light beam 310 in opposite directions, and the first light sensor 110 and the second light sensor 112 are positioned on opposite sides of the beam splitters to receive the first light beam 308 and the second light beam 310, respectively, from the at least one beam splitter (e.g., from mirrors 312, 314).

[0041] In contrast to the conventional Coriolis mass flowmeters described above, the exemplary flowmeter of Figure 3 has reduced phase noise. Because only one light source 306 is used for both channels (e.g., both optical sensors 110, 112), the noise contributions to each channel from the light source 306 and the light source controller 208 are not independent because the noise contributions are generated by the same components (e.g., the light source 306 and the light source controller 208) for both channels and can be compensated for by the control circuitry 122. As a result, the disclosed exemplary mass flowmeter of Figure 3 reduces the number of noise contributing elements from six to two, improving the measurement accuracy of the exemplary mass flowmeter over conventional mass flowmeters.

[0042] FIG. 4 is a schematic diagram of an exemplary embodiment of the mass flow meter / controller 100 of FIG. 1 that includes one or more beam splitters (e.g., mirrors 312, 314) that split the light 304 output by a single light source 306 into multiple light beams 308, 310 that are detected by multiple light sensors 110, 112.

[0043] In the example of FIG. 4 , the optical sensors 110, 112 are thermally coupled to one another via a printed circuit board 402. That is, the optical sensors 110, 112 are coupled to the same printed circuit board 402, which further includes paths of thermally conductive material 403 (e.g., strips of copper, aluminum, etc.) coupling the optical sensors 110, 112. Because the optical sensors 110, 112 have several parameters that are temperature-dependent, temperature differences between the optical sensors 110, 112 can result in differences in the output signals and additional phase errors. The example printed circuit board 402 reduces the temperature-dependent phase difference between the optical sensors 110, 112 by placing the optical sensors 110, 112 in close proximity, thereby reducing or substantially eliminating the temperature gradient between the optical sensors 110, 112.

[0044] The example light sensors 110, 112 are mounted on the circuit board 402 instead of being mounted on the opposite side of the flow tube 104 from the mirror 312. The third mirror 404 is configured at a 45 degree angle with respect to the first light beam 308a from the first mirror 312 to reflect the first light beam 308a to the first light sensor 110. The fourth mirror 406 is configured at a 45 degree angle with respect to the second light beam 310a to reflect the second light beam 310a from the first mirror 312 to the second light sensor 112. Both mirrors 404, 406 reflect almost all of the incident light (e.g., the first light beams 308a, 308b and the second light beams 310a, 310b) by 90 degrees and direct the light beams 308a, 308b, 310a, 310b toward the light sensors 110, 112 so that the light beams 308b, 310b incident on the light sensors 110, 112 travel in the same direction (e.g., 0 degrees relative to the emitted light 304 generated by the light source 306).

[0045] In the example of Figure 4, the vibration direction of flow tube 104 is different from the example of Figure 3. A first location 118 on flow tube 104, a second location 120 on flow tube 104, and the portion of flow tube 104 between first location 118 and second location 120 (e.g., the U-shaped portion of flow tube 104) are oriented on a two-dimensional plane 214, as shown in Figures 2-5. In the example of Figure 3, the vibration direction of flow tube 104 is transverse to plane 214, while the vibration direction in the examples of Figures 2, 4, and 5 is within plane 214. The actuator (e.g., drive coil 116 and / or magnet 114) is configured to obtain the vibration direction based on the placement of optical sensors 110, 112 and light beams 308, 310 relative to flow tube 104.

[0046] 4, the light source 306 and / or the light source controller 208 are coupled to a second printed circuit board 408 separate from the printed circuit board 402. In the example of FIG. 4, the light sensors 110, 112 may be physically separated from the light source 306 and the light source controller 208. Temperature differences may occur between the light sensors 110, 112 and the light source 306 and the light source controller 208 due to the physical separation, which may result in differences in output signals, additional phase errors, and loss of measurement accuracy. FIG. 5 is a schematic diagram of an exemplary implementation of the mass flow meter / controller 100 of FIG. 1 including one or more beam splitters (e.g., mirrors 312, 314) that split the light 304 output by the single light source 306 into multiple light beams 308, 310 that are detected by the multiple light sensors 110, 112. In the example of FIG. 5, the light sensors 110 , 112 , the light source 306 , and the light source controller 208 are thermally coupled to one another via a printed circuit board 502 .

[0047] Because the photosensors 110, 112, the light source 306, and the light source controller 208 have several parameters that are temperature dependent, temperature differences between the photosensors 110, 112 can result in differences in the output signals and additional phase errors. The example printed circuit board 502 has traces of thermally conductive material 504 (e.g., strips of copper, aluminum, etc.) that couple the photosensors 110, 112, the light source 306, and the light source controller 208. The example arrangement of the photosensors 110, 112, the light source 306, and the light source controller 208 in Figure 5 reduces temperature-dependent phase errors in the photosensors 110, 112, the light source 306, and the light source controller 208 by placing these components in close proximity, thereby reducing or substantially eliminating temperature gradients between the components.

[0048] 5 includes a third mirror 506 and a fourth mirror 508 to allow a single light source 306 to provide light beams 308, 310 to light sensors 110, 112 located on the same printed circuit board 502 in a manner that causes light beams 308a, 308b, 310a, 310b to traverse the flow tube 104. The third mirror 506 is configured at a 45-degree angle with respect to the first light beam 308a to reflect the first light beam 308a from the first mirror 312 to the first light sensor 110. The fourth mirror 508 is configured at a 45-degree angle with respect to the second light beam 310a to reflect the second light beam 310a from the first mirror 312 to the second light sensor 112. Both mirrors 506, 508 reflect almost all of the incident light (e.g., the first light beam 308a and the second light beam 310a) by 90 degrees and direct the light beams 308b, 310b toward the light sensors 110, 112 so that the light beams 308b, 310b incident on the light sensors 110, 112 travel in the opposite direction (e.g., 180 degrees relative to the emitted light 304 generated by the light source 306).

[0049] Due to the different locations of optical sensors 110, 112 relative to flow tube 104 (compared to the example of FIG. 4), mirror 506 is oriented at a 90 degree angle compared to the orientation of mirror 404 in FIG. 4, and mirror 508 is oriented at a 90 degree angle compared to the orientation of mirror 406.

[0050] 3-5 include one illustrative embodiment of a beamsplitter, however, any type of beamsplitter may be used. Exemplary beamsplitters that may be used include a cube beamsplitter, a plate beamsplitter, a pellicle beamsplitter, a Wollaston prism, a diffractive beamsplitter, an actuating beamsplitter, or a fused fiber beamsplitter.

[0051] Figure 6 is a flow chart illustrating an example method 600 that may be performed by the mass flow meter / controller 100 of Figures 2-5 to measure mass flow rate and / or fluid density and / or control mass flow rate. The example method 600 is described with reference to the example mass flow meter / controller 100 of Figures 1 and 3, although the method 600 may be performed using any of the disclosed example mass flow meter / controllers.

[0052] In block 602, the flow tube 104 directs fluid from an inlet of the flow tube 104 to an outlet of the flow tube 104. In block 604, an actuator induces vibrations in the flow tube 104.

[0053] In block 606, control circuitry 122 controls light source 306 to emit light 304 by controlling light source controller 208. For example, control circuitry 122 may enable light source controller 208 to enable light source 306. In block 608, one or more beam splitters (e.g., mirrors 312, 314) split the light 304 emitted by light source 306 into a first light beam 308 and a second light beam 310.

[0054] In block 610, the first optical sensor 110 measures a first position of the first location 118 on the flow tube 104 based on the detection of the first optical beam 308 or 308b and outputs a first measurement (e.g., after amplification by the amplifier 210). In block 612, the second optical sensor 112 measures a second position of the second location 120 on the flow tube 104 based on the detection of the second optical beam 310 or 310b and outputs a second measurement (e.g., after amplification by the amplifier 212). The first and second measurements may be signals indicative of the magnitudes of the first and second optical beams 308, 308b and 310, 310b, respectively, received by the optical sensors 110, 112. The amplitudes of the signals may change based on blockage of the optical beams 308, 308b, 310, 310b by the flow tube 104, which blockage changes as a result of vibration of the flow tube 104.

[0055] In block 614, the control circuitry 122 determines the mass flow rate through the flow tube 104 (e.g., based on the phase difference between the first measurement and the second measurement) and / or the density of the fluid within the flow tube 104 (e.g., based on the vibration frequency of the flow tube 104).

[0056] In block 616, the control circuitry 122 determines whether to control the flow rate. For example, a mass flow controller may be configured to control the flow rate, while a mass flow meter omits controlling the flow rate. If controlling the flow rate (block 616), the control circuitry 122 adjusts the flow control valve 124 based on the difference between the measured flow rate and the target flow rate.

[0057] After adjusting the flow control valve (block 618) or if the flow is not controlled (block 616), control returns to block 602 to continue measuring and / or controlling.

[0058] The methods and systems can be implemented in hardware, software, and / or a combination of hardware and software. The methods and / or systems can be implemented centrally in at least one computing system, or in a distributed fashion where different elements are distributed across several interconnected computing systems. Any kind of computing system or other apparatus adapted to perform the methods described herein is suitable. A typical combination of hardware and software can include a general-purpose computing system, along with a program or other code that, when loaded and executed, controls the computing system to perform the methods described herein. Another typical embodiment can include one or more application-specific integrated circuits or chips. Some embodiments can include a non-transitory machine-readable (e.g., computer-readable) medium (e.g., flash memory, optical disk, magnetic storage disk, etc.) that stores one or more lines of code executable by a machine, thereby causing the machine to perform a process as described herein. As used herein, the term "non-transitory machine-readable medium" is defined to include all types of machine-readable storage media and to exclude propagating signals.

[0059] Although the present methods and / or systems have been described with reference to certain specific embodiments, those skilled in the art will recognize that various modifications can be made and equivalents can be substituted without departing from the scope of the present methods and / or systems. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the scope of the present disclosure. For example, blocks and / or components of the disclosed examples can be combined, divided, rearranged, and / or otherwise modified. Therefore, the present methods and / or systems are not limited to the particular embodiments disclosed, but it is contemplated that the present methods and / or systems will include all embodiments falling within the scope of the appended claims.

[0060] As used herein, the terms "circuit" and "circuitry" refer to physical electronic components (i.e., hardware) and any software and / or firmware ("code") that can comprise, be executed by, and / or otherwise be associated with hardware. As used herein, for example, a particular processor and memory can include a first "circuit" when executing a first one or more lines of code, and can include a second "circuit" when executing a second one or more lines of code. As used herein, "and / or" means any one or more of the items in the list connected by "and / or." As an example, "x and / or y" means any element of the triplet {(x), (y), (x, y)}. In other words, "x and / or y" means "one or both of x and y." As another example, "x, y, and / or z" means any element of the seven-element set {(x), (y), (z), (x,y), (x,z), (y,z), (x,y,z)}. In other words, "x, y, and / or z" means "one or more of x, y, and z." As used herein, the term "exemplary" means serving as a non-limiting example, instance, or illustration. As used herein, the term "for example" begins a list of one or more non-limiting examples, instances, or illustrations. As used herein, circuitry is "operable" to perform a function whenever it includes the necessary hardware and code (if either is necessary) to perform that function, regardless of whether implementation of that function is disabled or enabled (e.g., by a user-configurable setting, factory trim, etc.).

[0061] The methods and / or systems can be implemented in hardware, software, or a combination of hardware and software. The methods and / or systems can be implemented centrally in at least one computing system, or in a distributed fashion where different elements are distributed across several interconnected computing systems. Any kind of computing system or other apparatus adapted to perform the methods described herein is suitable. A typical combination of hardware and software can be that of a general-purpose computing system, with programs or other code that, when loaded and executed, controls the computing system to perform the methods described herein. Another typical embodiment can include application-specific integrated circuits or chips. Some embodiments can include a non-transitory machine-readable (e.g., computer-readable) medium (e.g., a flash drive, optical disk, magnetic storage disk, etc.) that stores one or more lines of code executable by a machine, thereby causing the machine to perform a process as described herein.

[0062] Although the present method and / or system has been described with reference to certain specific embodiments, those skilled in the art will recognize that various modifications and equivalents may be substituted without departing from the scope of the present method and / or system. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the scope of the present disclosure. Therefore, the present method and / or system is not limited to the particular embodiments disclosed. Instead, the present method and / or system includes all embodiments falling within the scope of the appended claims, both literally and under the doctrine of equivalents. The inventions disclosed herein include the following: [Aspect 1] a flow tube configured to direct fluid from an inlet of the flow tube to an outlet of the flow tube; an actuator configured to induce vibrations in the flow tube; a light source configured to emit light; at least one beam splitter configured to split light emitted by the light source into a first light beam and a second light beam; a first optical sensor configured to output a first measurement of a first position of a first location on the flow tube based on detection of the first optical beam; a second optical sensor configured to output a second measurement of a second position at a second location on the flow tube based on detection of the second optical beam; control circuitry configured to determine at least one of a mass flow rate through the flow tube or a density of a fluid within the flow tube based on the first measurement and the second measurement; A mass flow meter / controller comprising: [Aspect 2] 2. The mass flow meter / controller of claim 1, wherein the at least one beam splitter is configured to direct the first light beam and the second light beam in opposite directions, and the first light sensor and the second light sensor are positioned on opposite sides of the at least one beam splitter to receive the first light beam and the second light beam, respectively, from the at least one beam splitter. [Aspect 3] The at least one beam splitter comprises: a first mirror positioned at a substantially 45 degree angle relative to the light source to reflect a first portion of light from the light source to form the first light beam; a second mirror positioned to reflect a second portion of the light from the light source that passes through the first mirror back towards the first mirror; wherein the first mirror is configured to reflect the second portion of light from the second mirror to form the second light beam. [Aspect 4] The at least one beam splitter comprises: a third mirror configured to reflect the first light beam from the first mirror to the first light sensor; a fourth mirror configured to reflect the second light beam from the first mirror to the second light sensor; 4. The mass flow meter / controller of embodiment 3, further comprising: [Aspect 5] 5. The mass flow meter / controller of aspect 4, further comprising a printed circuit board, wherein the first optical sensor and the second optical sensor are mounted to the printed circuit board. [Aspect 6] 6. The mass flow meter / controller of claim 5, wherein the printed circuit board is configured to thermally couple the first optical sensor and the second optical sensor. [Aspect 7] 7. The mass flow meter / controller of claim 6, wherein the light source is mounted on the printed circuit board and thermally coupled to the first light sensor and the second light sensor. [Aspect 8] 5. The mass flow meter / controller of claim 4, wherein the first location of the flow tube, the second location of the flow tube, and a portion of the flow tube between the first location and the second location are oriented on a two-dimensional plane, and the actuator is configured to induce vibrations in the flow tube in a direction along the two-dimensional plane. [Aspect 9] 4. The mass flow meter / controller of claim 3, wherein the first location of the flow tube, the second location of the flow tube, and a portion of the flow tube between the first location and the second location are oriented on a two-dimensional plane, and the actuator is configured to induce vibrations in the flow tube in a direction transverse to the two-dimensional plane. [Aspect 10] 2. The mass flow meter / controller of embodiment 1, wherein the at least one beam splitter comprises at least one of a cube beam splitter, a plate beam splitter, a pellicle beam splitter, a Wollaston prism, a diffractive beam splitter, an actuating beam splitter, or a fused fiber beam splitter. [Aspect 11] 2. The mass flow meter / controller of embodiment 1, wherein the actuator includes a drive coil configured to actuate the flow tube via a magnet attached to the flow tube. [Aspect 12] 2. The mass flow meter / controller of claim 1, further comprising a flow control valve configured to control the flow of fluid through the flow tube, wherein the control circuitry is configured to control the flow control valve based on the determined mass flow rate. [Aspect 13] directing a fluid from an inlet of a flow tube to an outlet of said flow tube; inducing vibrations in the flow tube via an actuator; emitting light from a light source; splitting light emitted from the light source into a first light beam and a second light beam via at least one beam splitter; outputting, via a first optical sensor, a first measurement of a first position of a first location on the flow tube based on detection of the first light beam; outputting, via a second optical sensor, a second measurement of a second position at a second location on the flow tube based on detection of the second light beam; determining, via control circuitry, at least one of a mass flow rate through the flow tube or a density of fluid within the flow tube based on the first measurement and the second measurement; A method comprising: [Aspect 14] Splitting the light through the at least one beam splitter includes: reflecting a first portion of light from the light source via a first mirror positioned at a substantially 45 degree angle relative to the light source to form the first light beam; reflecting, via a second mirror, a second portion of the light from the light source that passes through the first mirror back toward the first mirror; reflecting the second portion of light from the light source via the first mirror to form the second light beam; 14. The method of embodiment 13, comprising: [Aspect 15] 15. The method of embodiment 14, further comprising directing the first light beam and the second light beam in opposite directions. [Aspect 16] 16. The method of claim 15, further comprising: reflecting the first light beam through the first mirror to the first light sensor through the second mirror; and reflecting the second light beam reflected through the first mirror to the second light sensor. [Aspect 17] 17. The method of embodiment 16, further comprising thermally coupling the first optical sensor and the second optical sensor. [Aspect 18] 18. The method of embodiment 17, further comprising thermally coupling the light source to the first light sensor and the second light sensor. [Aspect 19] 14. The method of embodiment 13, wherein splitting the light comprises splitting the light using at least one of a cube beamsplitter, a plate beamsplitter, a pellicle beamsplitter, a Wollaston prism, a diffractive beamsplitter, an actuating beamsplitter, or a fused fiber beamsplitter. [Aspect 20] 14. The method of embodiment 13, wherein inducing vibration in the flow tube comprises actuating the flow tube via a magnet and a drive coil.

Claims

1. a flow tube configured to direct fluid from an inlet of the flow tube to an outlet of the flow tube; an actuator configured to induce vibrations in the flow tube; a light source configured to emit light; at least one beam splitter configured to split light emitted by the light source into a first light beam and a second light beam; a first optical sensor configured to output a first measurement of a first position of a first location on the flow tube based on detection of the first optical beam; a second optical sensor configured to output a second measurement of a second position at a second location on the flow tube based on detection of the second optical beam; control circuitry configured to determine at least one of a mass flow rate through the flow tube or a density of a fluid within the flow tube based on the first measurement and the second measurement; Equipped with the at least one beam splitter is configured to direct the first light beam and the second light beam in opposite directions, and the first light sensor and the second light sensor are positioned on opposite sides of the at least one beam splitter to receive the first light beam and the second light beam, respectively, from the at least one beam splitter.

2. A flow tube configured to guide a fluid from an inlet of the flow tube to an outlet of the flow tube; an actuator configured to induce vibrations in the flow tube; a light source configured to emit light; at least one beam splitter configured to split light emitted by the light source into a first light beam and a second light beam; a first optical sensor configured to output a first measurement of a first position of a first location on the flow tube based on detection of the first optical beam; a second optical sensor configured to output a second measurement of a second position at a second location on the flow tube based on detection of the second optical beam; control circuitry configured to determine at least one of a mass flow rate through the flow tube or a density of a fluid within the flow tube based on the first measurement and the second measurement; Equipped with The at least one beam splitter comprises: a first mirror positioned at a substantially 45 degree angle relative to the light source to reflect a first portion of light from the light source to form the first light beam; a second mirror positioned to reflect a second portion of the light from the light source that passes through the first mirror back towards the first mirror; wherein the first mirror is configured to reflect the second portion of light from the second mirror to form the second light beam.

3. The at least one beam splitter comprises: a third mirror configured to reflect the first light beam from the first mirror to the first light sensor; a fourth mirror configured to reflect the second light beam from the first mirror to the second light sensor; The mass flow meter of claim 2 further comprising:

4. The mass flow meter of claim 3 , further comprising a printed circuit board, the first optical sensor and the second optical sensor being mounted to the printed circuit board.

5. The mass flow meter of claim 4 , wherein the printed circuit board is configured to thermally couple the first optical sensor and the second optical sensor.

6. The mass flow meter of claim 5 , wherein the light source is mounted on the printed circuit board and thermally coupled to the first light sensor and the second light sensor.

7. 4. The mass flow meter of claim 3, wherein the first location of the flow tube, the second location of the flow tube, and a portion of the flow tube between the first location and the second location are oriented on a two-dimensional plane, and the actuator is configured to induce vibrations in the flow tube in a direction along the two-dimensional plane.

8. 3. The mass flow meter of claim 2, wherein the first location of the flow tube, the second location of the flow tube, and a portion of the flow tube between the first location and the second location are oriented in a two-dimensional plane, and the actuator is configured to induce vibrations in the flow tube in a direction transverse to the two-dimensional plane.

9. 3. The mass flow meter of claim 1, wherein the at least one beam splitter comprises at least one of a cube beam splitter, a plate beam splitter, a pellicle beam splitter, a Wollaston prism, a diffractive beam splitter, an actuating beam splitter, or a fused fiber beam splitter.

10. The mass flow meter of claim 1 or 2, wherein the actuator includes a drive coil configured to actuate the flow tube via a magnet attached to the flow tube.

11. 3. The mass flow meter of claim 1, further comprising a flow control valve configured to control the flow of fluid through the flow tube, wherein the control circuitry is configured to control the flow control valve based on the determined mass flow rate.

12. directing a fluid from an inlet of a flow tube to an outlet of said flow tube; inducing vibrations in the flow tube via an actuator; emitting light from a light source; splitting light emitted from the light source into a first light beam and a second light beam via at least one beam splitter; outputting, via a first optical sensor, a first measurement of a first position of a first location on the flow tube based on detection of the first light beam; outputting, via a second optical sensor, a second measurement of a second position at a second location on the flow tube based on detection of the second light beam; determining, via control circuitry, at least one of a mass flow rate through the flow tube or a density of fluid within the flow tube based on the first measurement and the second measurement; Including, Splitting the light through the at least one beam splitter includes: reflecting a first portion of light from the light source via a first mirror positioned at a substantially 45 degree angle relative to the light source to form the first light beam; reflecting, via a second mirror, a second portion of the light from the light source that passes through the first mirror back toward the first mirror; reflecting the second portion of light from the light source via the first mirror to form the second light beam; A method comprising:

13. The method of claim 12 , further comprising directing the first light beam and the second light beam in opposite directions.

14. 14. The method of claim 13, further comprising reflecting the first light beam through the first mirror to the first light sensor, and reflecting the second light beam reflected through the first mirror to the second light sensor.

15. The method of claim 14 , further comprising thermally coupling the first photosensor and the second photosensor.

16. The method of claim 15 , further comprising thermally coupling the light source to the first light sensor and the second light sensor.

17. 13. The method of claim 12, wherein splitting the light comprises splitting the light using at least one of a cube beamsplitter, a plate beamsplitter, a pellicle beamsplitter, a Wollaston prism, a diffractive beamsplitter, an actuating beamsplitter, or a fused fiber beamsplitter.

18. The method of claim 12 , wherein inducing vibration in the flow tube comprises actuating the flow tube via a magnet and a drive coil.

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