Valve assembly and system for controlling flow of fluid

Abstract

A mass flow meter includes a flow path through the mass flow meter, where the flow path includes a first cavity and a second cavity. The mass flow meter also includes a laminar flow element adjacent the first cavity and the second cavity, where the first cavity is upstream of the laminar flow element and the second cavity is downstream of the laminar flow element. A pressure transducer is positioned in at least one of the first cavity or the second cavity, where the pressure transducer includes at least one diaphragm, and linear and non-linear responses of the at least one diaphragm to the first pressure are measured to determine a voltage signal indicative of the pressure. The mass flow meter converts a pressure reading obtained from the pressure transducer into a signal indicative of mass flow through the laminar flow element.

Description

Background Art

[0001] In order to maintain the desired product yield, the equipment used in semiconductor wafer manufacturing needs to operate with high precision. In the process of manufacturing integrated circuits, certain chemicals are used in the processing chamber to process semiconductor wafers. Mass flow controllers (MFCs) are used to deliver these chemicals to the processing chamber in a consistent manner and with accurate flow rates. This can be very challenging because the MFC is required to maintain very strict accuracy, operate under multiple set points, and constantly shut down and restart during the wafer manufacturing process. In order to manage this accuracy, the MFCs of the prior art are equipped with processor-based control units, a large number of sensors, and advanced diagnostic systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0002] For a more complete understanding of the features and advantages of the present disclosure, reference is now made to the detailed description and accompanying drawings, in which corresponding reference numerals in the different drawings represent corresponding parts, and in which:

[0003] Figure 1 is an illustration of a schematic diagram of a pressure-based mass flow controller having a flow sensor upstream of a valve according to certain embodiments of the present disclosure;

[0004] Figure 2 is an illustration of a schematic diagram of a combined absolute and differential pressure transducer assembly according to certain embodiments of the present disclosure;

[0005] 3a and 3b are diagrams of pressure sensors according to certain example embodiments;

[0006] Figure 4 is a graphical representation of performance modeling of a prototype MFC implemented in accordance with one embodiment of the present teachings having a primary linear range of 0 to 5 psi and a non-linear range of 5 to 60 psi;

[0007] Figure 5 is a graphical representation of test data illustrating performance characteristics (sensor sensitivity and non-linearity) of a pressure sensor implemented in accordance with one embodiment of the present invention, demonstrating the improved performance of such an embodiment when extending the range of use of the device into the non-linear region;

[0008] Figure 6 is a graphical representation of the performance of a conventional sensor used in an MFC compared to the performance of a sensor used in an MFC implemented according to one embodiment of the present invention.

[0009] Figure 7 is a graphical representation of an aging test of a prototype pressure sensor implemented in accordance with one embodiment of the present invention, illustrating its stability over time; and

[0010] Figure 8 is an illustration of a computing machine and system application modules according to certain example embodiments.

[0011] Fig. 9 is a graphical representation of a comparison of deflection and non-linearity between a conventional 50 PSI linear area pressure transducer using a thicker 25 micron diaphragm and an embodiment of the present invention's 5 PSI linear area pressure transducer using a thinner 10 micron diaphragm.

[0012] The illustrated drawings are only exemplary and are not intended to assert or imply any limitation with regard to the environment, architecture, design, or process in which different examples may be implemented. DETAILED DESCRIPTION

[0013] The present invention generally relates to methods and systems for controlling the mass flow of fluids, and more particularly to the operation of mass flow controllers (MFCs) and mass flow meters (MFMs) for gases and other compressible or incompressible fluids. The term "fluid" is used herein to describe any type of substance in any state capable of flowing. The term "gas" is used herein to describe any fluid whose density depends substantially on absolute pressure, such as ideal or non-ideal gases, vapors, and supercritical fluids. The term "liquid" is used herein to describe any fluid whose density does not depend substantially on absolute pressure.

[0014] Diaphragms are used in pressure sensors to convert the deflection caused by the pressure applied to the diaphragm into a voltage signal used by the MFC to calculate flow. The overpressure rating of a pressure sensor is the maximum pressure that the device can withstand without introducing material calibration shifts. The overpressure rating of a pressure sensor is typically 4 times the full-scale rating. The full-scale rating has historically been the point at which the PT shows 1% TBNL. Many modern pressure sensors are manufactured by utilizing semiconductor manufacturing methods to form significantly smaller silicon diaphragms in which the piezoelectric limiting elements are located at high strain locations on the silicon diaphragm. Silicon, as a single crystal, is an effective material for diaphragm applications. According to the teachings of the present invention, through appropriately customized designs, silicon-based diaphragms can deflect well beyond the linear pressure deflection range (primarily based on bending mechanisms) into an extended nonlinear pressure deflection range (primarily based on membrane mechanisms) without the presence of localized material dislocations or stress concentration sources that cause buckling and permanent calibration shifts.

[0015] The teachings of certain embodiments of the present invention allow the implementation of an improved MFC that utilizes pressure sensors that provide a large ratio of maximum overpressure to annual zero drift, regardless of the linearity of the signal. This ratio determines the annual stable dynamic range of the pressure-based MFC. The magnitude of the pressure transducer annual zero drift is the primary cause of long-term pressure measurement errors at lower flows, and determines the minimum flow rate at which the flow error of the MFC is acceptable for use. The annual drift of a pressure transducer is typically a percentage of its linear full scale. An annual drift of 0.05% of the predominantly linear full scale measurement per year is typically acceptable in the industry. As demonstrated by embodiments of the present invention, if the same transducer can be used in a nonlinear region with a pressure reading of, for example, 10 times its linear limit (without material damage), an annual drift of 0.05% of the linear full scale will only be 0.005% of its maximum overpressure or nonlinear full scale. Therefore, by utilizing the nonlinear region of the transducer, an MFC implemented according to the teachings of the present invention will significantly increase its annual stability relative to its maximum operating range, thereby significantly improving the performance and value of the MFC. As another advantage, due to the increased operating range of the MFCs of various embodiments of the present invention, a single MFC can replace two conventional MFCs.

[0016] Although the manufacture and use of various embodiments of the present disclosure are discussed in detail below, it should be understood that the present disclosure provides many applicable inventive concepts that can be embodied in many specific contexts. The specific embodiments discussed herein are merely illustrative and do not limit the scope of the present disclosure. For clarity, all features of an actual implementation may not be described in the present disclosure.

[0017] Unless otherwise indicated, all numerical values ​​used in this specification and the associated claims to represent the amount of components, properties such as molecular weight, reaction conditions, etc. should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters listed in the following specification and the attached claims are approximate values ​​that can be varied according to the desired properties that the examples of the present invention strive to obtain. At least, it is not intended to limit the application of the doctrine of equivalents to the scope of the claims, and each numerical parameter should be interpreted at least according to the numerical value of the reported significant figures and by applying ordinary rounding techniques. It should be noted that when "about" is at the beginning of the numerical list, "about" modifies each number in the numerical list. Further, in some numerical range lists, some of the listed lower limits may be greater than some of the listed upper limits. Those skilled in the art will recognize that the selected subset will need to select an upper limit that exceeds the selected lower limit. Further, although the voltage signal discussed herein is discussed as a positive voltage, a negative voltage signal or a differential voltage signal can be generated, used or detected without departing from the scope of the present invention.

[0018] A valve assembly for controlling fluid flow is proposed herein. The valve assembly includes a valve block having an upstream reservoir, a downstream reservoir, and a valve seat for transferring fluid from an upstream position to a downstream position. The valve assembly also includes an independent valve having a movable member, a sensor chip package having at least one sensor coupled to the independent valve, and a controller interface. The controller interface sends at least one measured parameter value provided by the at least one sensor, and receives a control signal for adjusting the valve stroke of the independent valve. The control signal is determined based on the at least one measured parameter value.

[0019] This paper also proposes a fluid handling system for manufacturing facilities. The fluid handling system includes a valve block, an independent valve, an upstream fluid source fluidically connected to the independent valve, a downstream processing tool fluidically connected to the independent valve, and a control unit. As used herein, upstream or upstream side refers to the position or side closest to the fluid source, for example, after the upstream valve or before the downstream valve in the MFC. As used herein, downstream or downstream side refers to the position or side farthest from the fluid source.

[0020] The valve block includes an upstream reservoir, a downstream reservoir, and a valve seat for transferring fluid from an upstream position to a downstream position. The independent valve has a movable member and a sensor chip package, and the sensor chip package has at least one sensor connected to the valve. The control unit includes an interface that can be communicatively connected to the independent valve and the sensor chip package. The control unit generates a control signal for controlling the stroke of the independent valve based on at least one parameter value from the sensor chip package.

[0021] Figure 1 A schematic diagram of a pressure-based mass flow controller (MFC) 5 having a flow sensor upstream of a valve according to certain embodiments of the present disclosure is illustrated. The operating principle of the MFC 5 is that changes in fluid flow rate produce changes in fluid pressure upstream and / or downstream of a flow restrictor (such as a laminar flow element), from which the fluid flow rate can be calculated.

[0022] In the depicted embodiment, the MFC 5 includes a power connector 10, a flow path 15, a flow control valve assembly 20, and at least one embodiment of a combined absolute pressure and differential pressure transducer assembly 25. The MFC 5 also includes an inlet port 30 for introducing fluid into the device and an outlet port 35 from which the fluid exits (e.g., to a processing chamber), and a laminar flow element 40. In some embodiments, the inlet port 30 may also include an inlet orifice plate 31 that is disposed within the inlet port 30 and blocks at least a portion of the fluid flow passing through the inlet port. The fluid may enter the MFC 5 via the inlet port 30 and flow within the MFC 5 along the flow path 15. In some embodiments, the flow path 15 may be maintained at a constant temperature. The flow control valve assembly 20 is positioned along the flow path 15 near the outlet port 35 and is positioned downstream of the combined absolute pressure and differential pressure transducer assembly 25. The flow control valve assembly 20 may include a proportional control valve (e.g., a solenoid valve or a piezoelectric control valve) that is adjustable to control the amount of fluid passing through the MFC 5. The flow control valve assembly 20 may actuate the control valve at any desired rate sufficient to control flow through the flow control valve assembly 20. Further, the actuation rate may be programmable and adjustable such that the control valve may be actuated continuously or in a step-like process.

[0023] continue Figure 1, the MFC 5 also includes a proportional-integral-derivative (hereinafter referred to as "PID") controller 45, which may include logic, circuits, memory, and one or more processing elements (processors). Although a PID controller is illustrated in this specific example, it should be understood that the PID controller is only one of many possible valve controllers, as will be readily apparent to those of ordinary skill in the art. For example, in some embodiments, the PID controller 45 may be replaced by a lead-lag controller, a gain lead-lag controller (e.g., as described in U.S. Pat. No. 6,962,164, which is incorporated herein by reference in its entirety), or any other controller sufficient for the present application. The controller may be implemented as hardware or firmware. The PID controller 45 is configured to control the position of the valve within the flow control valve assembly 20 according to a set point indicating a desired mass flow rate. For example, in one embodiment, the PID controller 45 receives an absolute pressure and a differential pressure from a combined absolute pressure and differential pressure transducer assembly 25 and a set point signal indicating a desired flow rate through the laminar flow element 40. The PID controller 45 uses the received information to convert the information of both the absolute pressure, the differential pressure, and the fluid properties and characteristics of the laminar flow element 40 into a signal indicating the mass flow rate through the laminar flow element 40. For example, in one embodiment, the PID controller 45 associates the pressure drop with the volume flow rate, which can then be converted into the mass flow rate using the density correction at a given temperature and pressure. The PID controller 45 can then generate a valve drive signal for controlling the flow control valve assembly 20 so that the signal indicating the mass flow rate through the laminar flow element 40 substantially matches the received set point signal. For example, in one embodiment, a control valve drive signal is generated based on an error signal, which is the difference between the set point signal indicating the desired mass flow rate of the fluid and the feedback signal, which is related to the actual mass flow rate determined by the PID controller 45 using the combined absolute pressure and differential pressure transducer assembly 25. In some examples, the desired flow rate of the set point signal is less than or equal to 10%. In some examples, the outlet pressure can be higher than about 2psia.

[0024] In one embodiment, the circuit board 50 can be attached to the back of the combined absolute pressure and differential pressure transducer assembly 25. In certain embodiments, the circuit board 50 can include flash memory and a flexible cable connector. The circuit board 50 can also provide a location for mounting a balancing resistor or other trimming resistor for any particular transducer. In some embodiments, the circuit board 50 can have a memory component that is configured to store data, such as but not limited to the calibration data of the combined absolute pressure and differential pressure transducer assembly 25. The circuit board 50 can include one or more accelerometers to allow automatic correction of the effects of gravity or acceleration on the measured pressure. The circuit board 50 can also include an instrumentation amplifier or other amplifier that is configured to amplify the output signals of the absolute pressure transducer and the differential pressure transducer and other components. The circuit board 50 can be supported by the pins of the combined absolute pressure and differential pressure transducer assembly 25 to achieve electrical connection with the absolute pressure transducer and the differential pressure transducer contained in the combined absolute pressure and differential pressure transducer assembly 25. In one embodiment of the invention, at least one of the pressure sensors comprising the pressure transducer assembly 25 is operable to generate a voltage reading in response to both linear and non-linear changes in the diaphragm of the pressure sensor. In another embodiment of the invention, at least one of the pressure sensors comprising the pressure transducer assembly 25 is operable to generate a voltage reading in response to non-linear changes in the diaphragm of the pressure sensor. In yet another embodiment of the invention, at least one of the pressure sensors comprising the pressure transducer assembly 25 is operable to generate a voltage reading in response to a pressure that falls within a non-linear operating region of the diaphragm of the pressure sensor.

[0025] Figure 2 An alternative embodiment of an MFC is illustrated, generally designated 305. MFC 305 is substantially similar to Figure 1 MFC 5; however, Figure 1 The combined absolute and differential pressure transducer assembly 25 has been replaced by a differential pressure transducer assembly 310, which includes an upstream differential pressure membrane, a downstream differential pressure membrane, and a differential pressure transducer similar to the upstream differential pressure membrane 120, the downstream differential pressure membrane 135, and the differential pressure transducer 130. However, in this particular embodiment, there is no absolute pressure transducer positioned with the differential pressure transducer. Alternatively, the absolute pressure transducer can be positioned separately from the differential pressure transducer assembly 310 at a position upstream of the laminar flow element 40, for example, at a position 315 in fluid communication with the feed volume 41; or, alternatively, at a position downstream of the laminar flow element 40, for example, at a position 320 in fluid communication with the inventory volume 42.

[0026] In general, the error of the pressure reading of the pressure sensor determines the minimum flow rate at which the pressure sensor can be used to fully measure the flow rate. More specifically, a smaller flow rate produces a smaller pressure signal, and eventually, the erroneous non-flow induced signal (sensor annual zero drift) becomes larger and eventually becomes a problem. Because it is impossible to distinguish between the reduced pressure induced signal (due to the smaller flow rate) and the erroneous non-pressure induced signal, the flow calculation based on the combined signal becomes increasingly inaccurate to the extent that it is no longer sufficient for use. For example, a 5psi, 1% best fit straight line test pressure transducer that can be used in a nonlinear region up to 50psi can be paired with a flow restriction element to achieve full flow at 50psi. Because the absolute error of the sensor is 0.05% of 5psi (linear rating), but the sensor will observe 50psi at full flow, the absolute error of the sensor will be 0.005% of the 50psi use pressure, and the flow error of the MFC is compared to the conventional 5psi, 1% best fit line test pressure transducer that cannot be used when exceeding the 5psi rating, 1 / 10 of the full scale use range. As discussed, such use is limited due to the potential for damage to the diaphragm design at higher psi and must be paired with a less restrictive flow element that produces full scale flow at 5 psi full scale. For purposes of the foregoing, error is defined as the pressure transducer's pressure measurement, err, divided by the Full Scale Usage Range ("FSUR") or %FSUR.

[0027] Because the pressure range that a pressure sensor can accurately measure is directly related to the flow range that can be accurately measured by a mass flow controller using the pressure sensor, a mass flow controller utilizing an NL sensor with a maximum operating pressure can measure high flow rates and measure flow rates with a lower percentage error, or %FSUR, relative to the measured flow rate than a mass flow controller with a lower maximum pressure limited to its 1% best fit straight line value.

[0028] The design flow range operation of the mass flow controller (in one embodiment, at 1% reading accuracy) is referred to herein as the flow accuracy range. As discussed above, in current MFCs, this is typically defined around the main linear operating range of the pressure sensor, that is, when the linear response of the pressure sensor is dominant relative to any nonlinear response. At flow rates above or below this flow accuracy range, the flow measurement will not be as accurate. For example, traditionally, a mass flow controller may be able to accurately measure a flow rate between 10 and 100 sccm using the linear range of a pressure sensor that can accurately measure pressures between 0.5 and 5psi. Similarly, traditionally, a mass flow controller may be able to accurately measure a flow rate between 100 and 1000 sccm using the linear range of a pressure sensor that can accurately measure pressures between 5 and 50psi.

[0029] In one embodiment of the present invention, the laminar flow element is designed to operate accurately in two ranges of 0.5 to 5psi and 5 to 50psi using a pressure transducer that does not suffer material damage when operating at a pressure between 0 and 50psi, wherein the performance of the pressure transducer is gradually dominated by its nonlinear characteristics as the pressure increases. More particularly, the differential pressure transducer assembly 310 includes at least one pressure transducer, which is designed to operate in the linear and nonlinear ranges of the diaphragm included in the sensor. Therefore, in one embodiment of the present invention, using such a pressure transducer, a single MFC can be designed to have a flow accuracy range covering a flow range of 10 to 1000sccm, thereby allowing a new MFC to replace two conventional MFCs previously required to cover the same flow range. As used in this specification, a linear range or linear region refers to a pressure range where the linear characteristics of a pressure sensor / transducer are dominant relative to the nonlinear characteristics of the pressure sensor / transducer. Although the nonlinear characteristics of the pressure sensor / transducer may still exist, they are generally less substantial than linear characteristics. In contrast, a nonlinear range or region refers to a pressure range over which the nonlinear characteristics of a pressure sensor / transducer become significant compared to the linear characteristics of the pressure sensor / transducer. Likewise, while the linear characteristics of the pressure sensor / transducer may still exist, they are no longer sufficiently dominant to allow the nonlinear component to be ignored. It should be understood that at certain pressures (e.g., 5psi in some embodiments), both linear and nonlinear characteristics may be substantial and should be taken into account in the design and operation of the pressure sensor / transducer. It is worth noting that in current MFCs, nonlinearity is considered an undesirable complexity. In the present invention, nonlinearity is directly exploited to determine the sensed pressure over a wider range, which is then used to calculate the flow rate over a wider range.

[0030] In existing MFCs designed with transducers intended for pressures between 0 and 5 psi, the transducers will be damaged and performance degraded when exposed to pressures substantially exceeding 5 psi. More specifically, the diaphragm of a pressure transducer designed for low pressures will deform and distort or rupture when exposed to higher pressures (in some embodiments, if the pressure exceeds 400% of the 1% non-linear rating), resulting in performance problems and inaccurate pressure measurements. More specifically, pressure sensors used in conventional MFCs have an operating limit of 4 times their designed linear range, exceeding which they are permanently damaged, but are typically not used beyond 2 times this range for safety reasons.

[0031] According to the teachings of certain embodiments of the present invention, a single pressure sensor having a specific operating range in the linear performance region of its diaphragm is utilized. However, in addition to characterizing its output to determine the pressure in response to the performance of the diaphragm in its linear region, its output is additionally characterized to determine the pressure in response to the performance of the diaphragm in its nonlinear region, as discussed below. In this way, a single MFC can replace the performance of multiple MFCs to operate over a wider range of desired mass flow rates. For example, in the above example, the two mass flow controllers can be replaced by a single mass flow controller capable of measuring 10 to 1000 sccm using a pressure sensor having a linear range of 0.5 to 5 psi and a nonlinear range of 5 to 50 psi. In such a single mass flow controller, the ratio of the maximum 1% rated flow to the minimum 1% rated flow is equal to 10 to 1 in the linear operating range, but will increase to 100 to 1 in the nonlinear operating range. In upstream valve operation, this ratio can be increased to 1000 to 1 due to the flow characteristics of compressible flow at higher pressure drops when the control valve is located upstream.

[0032] FIG. 3a and FIG. 3b illustrate schematic diagrams of an absolute pressure sensor and a differential pressure sensor, respectively. In FIG. 3a, volume 402 is isolated from volume 404 by a pressure sensing diaphragm 406. It should be noted that diaphragm 406 can be thinner and more flexible, and can be tapered, and have a width and thickness different from that apparent from its illustration. Diaphragm 406 can contain transmitting elements that are directly disposed on the surface of the diaphragm or integral therewith, interfaced with sensor 408 or perform part of the function of the sensor. As is well known in the art, an isolation diaphragm (not shown, and not related to the teachings of the present invention) is typically used to isolate the pressure sensing diaphragm from the corrosive effects of the process fluid. In one embodiment, diaphragm 406 is a ceramic diaphragm selected based on its corrosion resistance in the presence of fluids expected to be present during operation of the MFC. Alternatively, diaphragm 406 can be single crystal silicon or polycrystalline silicon, germanium, titanium, polyethylene, metal, or a composite material having multiple layers of different materials. The selection of such material can depend on specific application, the fluid used, the expected flow range, life, flexibility and elasticity. This selection can also depend on the technical and economic feasibility of the material for a specific application. For example, although within the scope of the teachings of the present invention, stainless steel and other metals may be economically or technically unfeasible for manufacturing small pressure sensors using current manufacturing technology. The size of diaphragm 406 can also be selected based on the aforementioned and expected performance characteristics of diaphragm 406. In particular, the thickness and diameter of diaphragm 406 can be manufactured or selected based on the expected pressure range, rigidity, and linear and nonlinear characteristics. In an embodiment of the present invention, compared with existing 5psi equipment, the diameter of the diaphragm 406 used in the pressure sensor increases, and the thickness of the diaphragm decreases. This change promotes the increase of the relative magnitude of the nonlinear effect relative to the linear component. In each case compared with conventional MFC diaphragms, this change also prevents damage to the diaphragm from the linear component to allow the pressure sensor to operate in a nonlinear range without material damage or inaccurate measurement.

[0033] In order to better understand the foregoing, it is helpful to gain an understanding of bending action and membrane action. For discussion, simplified cases of bending in a beam and membrane action in a cable are used. When one side of the diaphragm is exposed to pressure, these two actions exist simultaneously in the more complex deflection geometry of the diaphragm. In practice, the shape of the diaphragm in a mass flow controller is typically different from the shape of the cable or beam (for example, with different cross-sections, tapers, curvatures, and variable diameters and thicknesses). However, this simplification illustrates the linear and nonlinear performance of the diaphragm. It should be recognized by those of ordinary skill in the art that the geometry of the diaphragm will indicate the unique "bending" of the diaphragm itself (or more accurately, "deflection" when deviating from the simplified beam / cable configuration), and since the geometry of the diaphragm changes compared to a simple beam, its bending will necessarily be more complex than the equations described and shown below. However, the following description is sufficient to teach the basic principles of linear and nonlinear operation and the mechanisms that work in the diaphragm. More specifically, the bending stiffness of a rectangular beam is proportional to the cube of the thickness of the beam ("t") multiplied by its width ("b").

[0034] K 弯曲 ≈bt 3 ≈t 3 . (Equation 1)

[0035] Similarly, the thickness and diameter of the diaphragm 406 may be manufactured or selected by virtue of its effect on range, stiffness, and linear and non-linear characteristics.

[0036] The elongation stiffness is proportional to the cross-sectional area of ​​the member.

[0037] K 伸长 ≈bt≈t 1 . (Equation 2)

[0038] Cross-sectional area = width "b" * thickness "t".

[0039] The foregoing neglects the membrane effects of the force applicator applied to the diaphragm, which membrane effects are described later below.

[0040] The above principles apply to a sensor 408 coupled to the diaphragm 406. In one embodiment, the sensor 408 is a capacitive sensor. Alternatively, the sensor 408 may be a strain gauge, a piezoelectric sensor, a resistive sensor, or any other suitable sensor. In general, whether by measuring changes in capacitance, resistance, voltage, current, or other electrical, electromechanical, or electromagnetic properties, a deflection in the diaphragm 406 results in a measurable electrical signal that is proportional to the deflection.

[0041] With respect to the operation of FIG. 3a, the introduction of fluid into volume 402 will exert a force on diaphragm 406. The higher the pressure in volume 402 relative to the reference pressure in volume 406, the higher the force exerted on diaphragm 406. Depending on the nature, size and other characteristics of diaphragm 406, this force will cause a deflection of diaphragm 406. The magnitude of this deflection is measured by sensor 408 and is generally linear for a specific range of forces (corresponding to a specific range of pressures in volume 402). In other words, an increase in force generally causes an increase in the deflection of diaphragm 406. Initially, this increase should occur according to a linear relationship between two variables, which can be measured by sensor 408. This linear relationship is important for the operation of the pressure sensor in a mass flow controller (whose purpose is to monitor pressure and thereby determine flow as described above). For example, when implementing a pressure sensor for an appropriate flow range, a table can be used to store data for plotting a linear x and y relationship between the magnitude of this deflection and the amount of pressure applied to sensor 408.

[0042] As the deflection of the diaphragm increases, this increase will increasingly occur due to the nonlinear relationship between force and deflection. Currently, due to the above-mentioned damage problems, MFCs do not utilize pressure sensors designed to allow operation in a high nonlinear range, and the overpressure limit of most commercial pressure sensors is 3 or 4 times the designed linear range. In various embodiments of the disclosed invention, MFCs with more than 20 times the designed linear range can be utilized. In one embodiment of the present invention, the pressure sensor is designed so that the maximum design deflection (linear performance area) of the diaphragm exceeds the thickness of the diaphragm, where the thickness is the thickness of the area of ​​the diaphragm where the deflection occurs. The engineering rule of thumb is that the nonlinear component becomes significant when the deflection approaches a moderate percentage of the thickness of the diaphragm. In another embodiment of the present invention, the pressure sensor is designed so that the maximum design deflection of the diaphragm exceeds twice the thickness of the diaphragm. In another embodiment of the present invention, the pressure sensor is designed so that the maximum design deflection of the diaphragm reaches or exceeds half the thickness of the diaphragm.

[0043] In one embodiment of the invention, the pressure sensor is designed so that the maximum design deflection of the diaphragm reaches or exceeds the thickness of the diaphragm, where the thickness is the thickness of the diaphragm in the region of the diaphragm where deflection occurs. In another embodiment of the invention, the pressure sensor is designed so that the maximum design deflection of the diaphragm reaches or exceeds twice the thickness of the diaphragm. In yet another embodiment of the invention, the pressure sensor is designed so that the maximum design deflection of the diaphragm ranges between half and twice the thickness of the diaphragm.

[0044] FIG3b illustrates the use of a differential pressure sensor 410. A differential pressure sensor can remove a source of error that an absolute pressure sensor may encounter. In FIG3b, volume 412 is isolated from volume 414 by a diaphragm 416. In one embodiment, two pressure sensors 418 and 420 may be used in a single housing, such as an absolute pressure sensor 418 and a differential pressure sensor 420. The pressure measurements of pressure sensors 418 and 420 may be used in combination to determine changes in flow, as discussed above. The above discussion of diaphragm 406 of FIG3a will also apply to diaphragm 416.

[0045] As previously mentioned, the size and other characteristics of the diaphragm in the MFC can be selected based on a specific application, the fluid used, the expected flow range, the maximum operating pressure, the life span, flexibility, elasticity or other expected performance characteristics. The most important one of these performance characteristics is the expected flow range (the flow range expected to be measured and controlled by the MFC) and the pressure range expected to be measured by the sensor (such as sensor 408 and 420 or 418). More specifically, due to the need to maintain the linear relationship between the deflection amount of pressure and the diaphragm, a specific diaphragm has always been used only within a specific flow range. Therefore, the performance characteristics of this diaphragm (including but not limited to the size of this diaphragm) can be selected by a pressure sensor or an MFC designer based on the flow range expected to be required by a specific MFC. Outside this flow range (under a pressure lower than or higher than the measured pressure corresponding to the flow measured by the MFC in this flow range), the deflection and physical changes of the selected diaphragm will no longer follow a linear relationship with the pressure. For any diaphragm, there are both linear and nonlinear responses about how the diaphragm reacts to pressure. However, within the expected flow range, the linear response is dominant relative to the nonlinear response, so that overall, when measuring how the diaphragm changes when the pressure changes, a linear or first-order relationship (such as a table that can be stored in the memory of the MFC) still dominates. The limited range of the diaphragm is a key design limitation to the MFC. Because linear performance is only possible over a certain range of pressures and therefore flows, a specific MFC can only be used for a certain range of flows. If a wider performance range is required, multiple MFCs must be used (increasing system cost, complexity, maintenance requirements, and performance speed), or MFCs of different flow ranges must be replaced when necessary (increasing cost, system downtime, and complexity).

[0046] If the MFC is operated outside of its expected flow range, the readings of the sensor (such as sensor 408) are increasingly affected by the nonlinear components of the diaphragm (such as diaphragm 406). To better understand this, when the diaphragm is deflected by force or pressure, two mechanisms occur in the diaphragm. The first is a deflection mechanism, similar to bending in beam theory, where the deflection is linearly related to the force as discussed above. The second is a stretching mechanism, which is caused by the material stretching to accommodate the required growth in the length of the centerline of the diaphragm, which is membrane theory and is nonlinear. Membrane theory is based on a magnitude that depends on the amount of "stretching" required and the angle of "stretching". Both the deflection mechanism and the membrane mechanism are always present, but the membrane effect is not significant within the diaphragm linear flow range. For small deflections, the "stretching" produced by the geometry that deflects the flat diaphragm is minimal, and the force resisting the membrane stretching is negligible relative to the force resisting the diaphragm deflection. In one embodiment, the sensing diaphragm of the first pressure sensor can operate dominantly in the linear range until the deflection of such a sensing diaphragm is greater than 50% of the diaphragm thickness. In another embodiment, the membrane of the second pressure sensor can be operated in a linear range until the deflection of such membrane is greater than the membrane thickness. After exceeding such deflection, non-linear operation of the membrane must be considered.

[0047] As the deflection of the diaphragm increases, the incremental "stretch" per unit deflection grows, and eventually, the membrane force is no longer insignificant compared to the bending force and a gradually nonlinear force versus deflection curve is induced. Initially, the force versus deflection curve is dominated by a linear deflection mechanism. As the deflection increases, the nonlinear membrane forces increase and become significant. When in the linear region, for simplicity, when the diaphragm experiences relatively small deflections due to the force at its center, the diaphragm is considered to be a simple flat beam with fixed supports at both ends. For small loads / deflections, the beam does not need to stretch much to produce the deflection, and the membrane action is minimal. In effect, diaphragm deflection is similar to beam theory, where the deflection is linearly related to the applied force.

[0048] D=K Geo *Force. (Equation 3)

[0049] As the deflection increases, the beam stretches at an increasing rate and the membrane forces become significant, causing nonlinearity. The physical dimensions of the diaphragm affect the linear and nonlinear components of how the diaphragm reacts to the forces exerted on it by fluid pressure. In bending theory, the stiffness of a square beam is proportional to the thickness (or depth "t") of the beam raised to the third power times the width of the beam ("b").

[0050] K 弯曲 ≈bt 3 ≈t 3 . (Equation 4)

[0051] In membrane theory, the elongational stiffness is proportional to the cross-sectional area of ​​the member. As the diaphragm deflects, the amount of stretch per unit deflection increases because the angle of the force vector becomes less perpendicular.

[0052] K 伸长 ≈bt≈t 1 (Equation 5)

[0053] Where cross-sectional area = width "b" * thickness "t". As an example, if the thickness of the diaphragm is doubled, the membrane effect is doubled, while the bending contribution increases by a factor of 8. A thicker diaphragm will have a longer linear range, but the stiffness will increase by about 8 times.

[0054] When the linear and nonlinear responses of the diaphragm are viewed in combination and expressed mathematically, the force exerted on the diaphragm (the pressure of the fluid in the volume containing the diaphragm) is as follows:

[0055] P=cy+dy 3 In the formula

[0056]

[0057] Where P = pressure, and y = deflection. The rest are fixed values ​​for the specific diaphragm, geometry, and properties of the diaphragm material, where a = diameter, h = thickness, E = Young's modulus, and Mu = Poisson's ratio.

[0058] In the present invention, rather than relying on the linear performance characteristics of diaphragm 406 within the conventional design flow range of the MFC, a processor of the MFC (such as processor 510 described below) uses measurements from sensor 408 or another pressure sensor to measure the linear performance, nonlinear performance, or a combination of linear and nonlinear performance of diaphragm 406 to determine the pressure of the fluid within volume 402. In one embodiment, both a differential sensor and an absolute sensor form sensor 408.

[0059] refer to Figure 4 , presents a comparison of a model of an MFC operating in both the linear and nonlinear regions with a model of a conventional MFC operating only in the linear region. Both models utilize calculations based on the compressible flow equation for laminar flow elements. An MFC implemented in accordance with the teachings of the present invention has a 1%R error operating range between 500 to 1 of the design minimum flow rate, while a conventional MFC has an operating range between 20 to 1 of the design minimum detectable flow rate. More specifically, Figure 7The magnitude of sensor annual drift is illustrated. At 100% flow given a maximum inlet pressure of 38 psi, a conventional MFC utilizing a 50-psi 1% best fit straight line conventional PT has a sensor annual drift of 0.05% of the linear full scale rating or 0.25 psi / year, while an MFC utilizing a 5-psi 1% best fit straight line pressure transducer capable of 50 psi operation has a sensor annual drift of 0.025 psi / year, a tenfold improvement.

[0060] refer to Figure 5 , illustrates testing of a prototype pressure sensor having a linear range of 0 to 5 psi and a non-linear range of 5 to 60 psi, implemented in accordance with one embodiment of the present teachings. Figure 5 The calibration curve is shown, as well as the change in the output of the pressure sensor compared to the measured pressure (in PSI). As illustrated, the performance curve demonstrates the polynomial curve expected from the calculated relationship between pressure and output voltage. Thus, a prototype MFC using this pressure sensor demonstrates successful tracking of pressure well into the non-linear operating region of the pressure sensor, and therefore successfully tracks flow.

[0061] refer to Figure 6 , illustrates the performance of a conventional sensor used in an MFC compared to the performance of a sensor used in an MFC implemented according to an embodiment of the present invention, demonstrating the improved performance of such an embodiment. As shown, the pressure sensitivity (rate of change of the mV output of the pressure sensor with respect to changes in psi) of the MFC of the present invention is 4 to 14 times higher across the operating range of 0 to 60 psi. Figure 6 As shown, the response of the measured voltage at the terminals of the pressure transducer of an MFC implemented according to one embodiment of the present invention (linear region up to 5 psi and non-linear range extending to up to 60 psi) is 14% non-linear (shown as a 14% deviation from the best fit straight line), while the measured voltage at the terminals of a standard 50 psi linear pressure transducer is less than 1% non-linear. The tested data demonstrate that embodiments of the present invention show improved performance sensitivity when used to measure pressures three times the pressure limited to the 1% best fit straight line model, and show further improved performance sensitivity at at least eight times. Although zero drift (flow measured when the fluid is not flowing) is similar between the pressure sensors in the two MFCs, the sensor sensitivity is still four times higher at low pressures, making zero drift less of a problem in the MFC of the present invention. Overall, the 1% accuracy / stability range of the pressure sensor and therefore the MFC of the present invention is greatly improved compared to conventional MFCs.

[0062] refer to Figure 7, illustrates an aging test of a prototype pressure sensor implemented in accordance with one embodiment of the present invention. During the six month test period, a linear range 5 psi pressure sensor (capable of use at up to 60 psi without material failure) was subjected to varying pressures and temperature changes over certain time ranges shown. At the end of the six months, the drift was less than 0.05% error of its linear full scale. Given that most MFCs are designed to meet specification requirements with less than 1% error of full scale measurement, the MFC of the present invention operated well within such design limitations. This testing also verifies that Figure 6 1% annual stability assumption.

[0063] Reference now Figure 8 , illustrates a computing machine 500 and a system application module 600 according to an example embodiment. The computing machine 500 may correspond to any of the various computers, mobile devices, laptop computers, Internet of Things (IoT), servers, embedded systems, or computing systems presented herein. The module 600 may include one or more hardware or software elements, such as other OS applications and user and kernel space applications, which are designed to facilitate the computing machine 500 to perform the various methods and processing functions presented herein. The computing machine 500 may include various internal components or attached components, such as a processor 510, a system bus 520, a system memory 530, a storage medium 540, an input / output interface 550, a network interface 560 for communicating with a network 570 (e.g., cellular / GPS, Bluetooth, WIFI, or Devicenet, EtherCAT, Analog, RS485, etc.), and one or more sensors 580.

[0064] The computing machine can be implemented as a conventional computer system, an embedded controller, a laptop computer, a server, a mobile device, a smart phone, a wearable computer, a custom machine, any other hardware platform, or any combination or multiplicity thereof. The computing machine can be a distributed system configured to function using multiple computing machines interconnected via a data network or bus system.

[0065] Processor 510 can be designed to execute code instructions to perform operations and functions described herein, manage request flows and address mappings, and is designed to perform calculations and generate commands. Processor 510 can be configured to monitor and control the operation of components in a computing machine. Processor 510 can be a general-purpose processor, a processor core, a multiprocessor, a reconfigurable processor, a microcontroller, a digital signal processor ("DSP"), an application-specific integrated circuit ("ASIC"), a controller, a state machine, a gated logic, a discrete hardware component, any other processing unit, or any combination or multiplicity thereof. Processor 510 can be a single processing unit, multiple processing units, a single processing core, multiple processing cores, a dedicated processing core, a coprocessor, or any combination thereof. According to some embodiments, processor 510 and other components of computing machine 500 can be software-based or hardware-based virtualized computing machines executed in one or more other computing machines.

[0066] The system memory 530 may include non-volatile memory, such as read-only memory ("ROM"), programmable read-only memory ("PROM"), erasable programmable read-only memory ("EPROM"), flash memory, or any other device capable of storing program instructions or data with or without the application of power. The system memory 530 may also include volatile memory, such as random access memory ("RAM"), static random access memory ("SRAM"), dynamic random access memory ("DRAM"), and synchronous dynamic random access memory ("SDRAM"). Other types of RAM may also be used to implement the system memory 530. The system memory 530 may be implemented using a single memory module or multiple memory modules. Although the system memory 530 is depicted as part of the computing machine, those skilled in the art will recognize that the system memory 530 may be separate from the computing machine 500 without departing from the scope of the present technology. It should also be understood that the system memory 530 may include or operate in conjunction with a non-volatile storage device such as storage medium 540.

[0067] Storage medium 540 may include a hard disk, a floppy disk, a compact disk read only memory ("CD-ROM"), a digital versatile disk ("DVD"), a Blu-ray disk, a magnetic tape, a flash memory, other non-volatile storage devices, a solid state drive ("SSD"), any magnetic storage device, any optical storage device, any electrical storage device, any semiconductor storage device, any physically based storage device, any other data storage device, or any combination or multiplicity thereof. Storage medium 540 may store one or more operating systems, application programs and program modules, data, or any other information. Storage medium 540 may be part of or connected to a computing machine. Storage medium 540 may also be part of one or more other computing machines that communicate with the computing machine (such as a server, a database server, a cloud storage device, a network-attached storage device, etc.).

[0068] The application module 600 and other OS application modules may include one or more hardware or software elements configured to facilitate the computing machine to perform the various methods and processing functions presented herein. The application module 600 and other OS application modules may include one or more algorithms or instruction sequences stored as software or firmware associated with the system memory 530, the storage medium 540, or both. Therefore, the storage medium 540 may represent an example of a machine or computer readable medium, on which instructions or codes for execution by the processor 510 may be stored. A machine or computer readable medium may generally refer to any one or more media for providing instructions to the processor 510. Such a machine or computer readable medium associated with the application module 600 and other OS application modules may include a computer software product. It should be understood that a computer software product including the application module 600 and other OS application modules may also be associated with one or more processes or methods for transmitting the application module 600 and other OS application modules to the computing machine via a network, any signal bearing medium, or any other communication or transmission technology. The application module 600 and other OS application modules may also include hardware circuits or information for configuring hardware circuits, such as microcode or configuration information for FPGAs or other PLDs. In an exemplary embodiment, the application module 600 and other OS application modules may include algorithms capable of performing the functional operations described by the computer system flow diagrams (operating modes) presented herein.

[0069] Input / output ("I / O") interface 550 may be configured to be connected to one or more external devices to receive data from the one or more external devices and to send data to the one or more external devices. Such external devices and various internal devices may also be referred to as peripheral devices. I / O interface 550 may include both electrical and physical connections for connecting various peripheral devices to computing machine or processor 510. I / O interface 550 may be configured to transmit data, address and control signals between peripheral devices, computing machine or processor 510. I / O interface 550 may be configured to implement any standard interface, such as small computer system interface ("SCSI"), serial attached SCSI ("SAS"), fiber channel, peripheral component interconnect ("PCI"), PCI express (PCIe), serial bus, parallel bus, advanced technology attachment ("ATA"), serial ATA ("SATA"), universal serial bus ("USB"), Thunderbolt, FireWire, various video buses, etc. I / O interface 550 may be configured to implement only one interface or bus technology. Alternatively, I / O interface 550 may be configured to implement a variety of interface or bus technologies. I / O interface 550 may be configured to operate as part, all, or in conjunction with system bus 520. I / O interface 550 may include one or more buffers for buffering transmissions between one or more external devices, internal devices, computing machines, or processors 520.

[0070] I / O interface 520 can connect the computing machine to various input devices, including a mouse, a touch screen, a scanner, an electronic digitizer, a sensor, a receiver, a touch pad, a trackball, a camera, a microphone, a keyboard, any other pointing device, or any combination thereof. I / O interface 520 can connect the computing machine to various output devices, including a video display, a speaker, a printer, a projector, a tactile feedback device, an automation control, a robotic component, an actuator, a motor, a fan, a solenoid, a valve, a pump, a transmitter, a signal transmitter, a lamp, etc.

[0071] The computing machine 500 can operate in a networked environment using logical connections to one or more other systems or computing machines on the network through the NIC 560. The network may include a wide area network (WAN), a local area network (LAN), an intranet, the Internet, a wireless access network, a wired network, a mobile network, a telephone network, an optical network, or a combination thereof. The network may be packet-switched, circuit-switched, of any topology, and may use any communication protocol. The communication links within the network may involve various digital or analog communication media, such as fiber optic cables, free space optics, waveguides, electrical conductors, wireless links, antennas, radio frequency communications, etc.

[0072] The one or more sensors 580 may be position sensors and pressure sensors. The pressure sensor may be an absolute pressure (P) sensor or a differential pressure (DP) sensor. The position sensor may be a capacitive sensor, an optical sensor, a strain gauge sensor, or a magnetic sensor. The sensor 180 may be a conventional sensor or a semiconductor-based sensor.

[0073] The processor 510 may be connected to other elements of the computing machine or various peripheral devices discussed herein via a system bus 520. It should be understood that the system bus 520 may be internal to the processor 510, external to the processor 510, or both. According to some embodiments, any of the processor 510, other elements of the computing machine, or various peripheral devices discussed herein may be integrated into a single device, such as a system on a chip (“SOC”), a system on a package (“SOP”), or an ASIC device.

[0074] Embodiments may include computer programs that embody the functions described and illustrated herein, wherein the computer programs are implemented in a computer system that includes instructions stored in a machine-readable medium and a processor that executes these instructions. However, it should be clear that there may be many different ways to implement the embodiments in computer programming, and unless otherwise disclosed for exemplary embodiments, the embodiments should not be interpreted as being limited to any computer program instruction set. Further, a skilled programmer will be able to write such a computer program based on the flowcharts, algorithms, and associated descriptions attached in the application text to implement the embodiments in the disclosed embodiments. Therefore, for a full understanding of how to make and use the embodiments, it is considered unnecessary to disclose a specific program code instruction set. Further, it will be understood by those skilled in the art that one or more aspects of the embodiments described herein may be performed by hardware, software, or a combination thereof, such as may be embodied in one or more computing systems. In addition, any reference to an action performed by a computer should not be interpreted as being performed by a single computer, because more than one computer may perform the action.

[0075] The example embodiments described herein can be used with computer hardware and software that perform the previously described methods and processing functions. The systems, methods, and processes described herein can be embodied in a programmable computer, computer executable software, or digital circuitry. The software can be stored on a computer readable medium. For example, a computer readable medium can include a floppy disk, RAM, ROM, hard disk, removable media, flash memory, memory stick, optical media, magneto-optical media, CD-ROM, etc. The digital circuitry can include an integrated circuit, a gate array, a building block logic, a field programmable gate array (FPGA), etc.

[0076] refer to Fig. 9, illustrates a comparison of deflection and nonlinearity between a conventional 50 PSI linear area pressure transducer using a thicker 25 micron diaphragm and an embodiment of the 5 PSI linear area pressure transducer of the present invention using a thinner 10 micron diaphragm. As shown, the nonlinearity during deflection over the entire pressure range of 0 to 60 PSI in the conventional pressure transducer peaks at about 0.03%. Alternatively, the nonlinearity during deflection over the entire pressure range of 0 to 60 PSI in the nonlinear pressure transducer peaks at about 12%. Therefore, thinning the diaphragm thickness (thereby increasing both nonlinearity and deflection) can be used to obtain the desired nonlinearity and performance of a particular MFM or MFC. Thinning the diaphragm can also reduce bending stress levels so that larger deflections can be achieved without degrading the device. Referring to the above discussion of bending action and membrane action, bending is a source of stress concentration on the surface of the diaphragm, while membrane action applies stress to the entire cross-section of the diaphragm. Although current manufacturing techniques may limit the diaphragm thickness to 5 microns for many applications, it is contemplated that the present invention will work equally well with diaphragms of even thinner thicknesses. The diameter of the diaphragm may also be used to determine the stiffness of the pressure transducer. These two features may be varied simultaneously in the transducer design.

[0077] The example systems, methods, and actions described in the previously presented embodiments are illustrative, and in alternative embodiments, certain actions may be performed in a different order, performed in parallel with each other, omitted entirely, and / or combined between different example embodiments, and / or certain additional actions may be performed without departing from the scope and spirit of the various embodiments. Such alternative embodiments are therefore included in the description herein.

[0078] As used herein, unless the context clearly indicates otherwise, the singular forms "a / an" and "said" are also intended to include plural forms. It should be further understood that the terms "include" and / or "comprise" used in this specification specify the presence of stated features, integrators, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integrators, steps, operations, elements, parts, and / or their collections. As used herein, the term "and / or" includes any and all combinations of one or more items in the associated listed items. As used herein, phrases such as "between X and Y" and "between about X and Y" should be interpreted as including X and Y. As used herein, phrases such as "between about X and Y" mean "between about X and about Y". As used herein, phrases such as "from about X to Y" mean "from about X to about Y".

[0079] As used herein, "hardware" may include a combination of discrete components, integrated circuits, application specific integrated circuits, field programmable gate arrays, or other suitable hardware. As used herein, "software" may include one or more objects, agents, threads, lines of code, subroutines, separate software applications, two or more lines of code or other suitable software structures (wherein the processor includes one or more microcomputers or other suitable data processing units, memory devices, input-output devices, displays, data input devices such as keyboards or mice, peripheral devices such as printers and speakers, associated drivers, control cards, power supplies, network devices, docking stations, or other suitable devices in combination with processors or other devices under the control of a software system) operated in two or more software applications on one or more processors, and other suitable software structures. In an exemplary embodiment, software may include one or more lines of code or other suitable software structures operated in a general software application such as an operating system, and one or more lines of code or other suitable software structures operated in a special software application. As used herein, the term "connection" and its cognate terms (such as "couple" and "coupled") may include physical connections (such as copper conductors), virtual connections (such as through randomly assigned memory locations of a data storage device), logical connections (such as through logic gates of a semiconductor device), other suitable connections, or suitable combinations of such connections. The term "data" may refer to suitable structures for using, transmitting, or storing data, such as data fields, data buffers, data messages having data values ​​and sender / receiver address data, control messages having data values ​​and one or more operators that cause a receiving system or component to perform a function using the data, or other suitable hardware or software components for electronic processing of data.

[0080] Generally, a software system is a system that operates on a processor to perform a predetermined function in response to a predetermined data field. For example, a system can be defined by the function performed by the system and the data field where the function is performed. As used herein, a NAME system (wherein NAME is typically the name of a general function performed by the system) refers to a software system that is configured to operate on a processor and perform the disclosed function on a disclosed data field. Unless a specific algorithm is disclosed, any suitable algorithm known to those skilled in the art for performing functions using associated data fields falls within the scope of the present disclosure. For example, a message system that generates a message including a sender address field, a receiver address field, and a message field will include software that operates on a processor, and a message system can obtain a sender address field, a receiver address field, and a message field from a suitable system or device such as a buffer device or a buffer system of the processor, and a sender address field, a receiver address field, and a message field can be combined into a suitable electronic message format (such as an email message, a TCP / IP message, or any other suitable message format with a sender address field, a receiver address field, and a message field), and an electronic message transceiving system and device of a processor can be used to send an electronic message through a communication medium such as a network. Those of ordinary skill in the art will be able to provide specific coding for specific applications based on the foregoing disclosure, which is intended to illustrate exemplary embodiments of the present disclosure rather than to provide tutorials for those less professional than those skilled in the art, such as those who are not familiar with programming in a suitable programming language or processor. Specific algorithms for performing functions may be provided in the form of a flowchart or other suitable format, wherein data fields and related functions may be illustrated in an exemplary order of operations, wherein the order may be rearranged appropriately, and unless expressly stated to be limiting, it is not intended to be limiting.

[0081] As used herein, unless the context clearly indicates otherwise, the singular forms "a / an" and "said" are also intended to include plural forms. It should be further understood that the terms "include" and / or "comprise" used in this specification specify the presence of stated features, integrators, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integrators, steps, operations, elements, parts, and / or their collections. As used herein, the term "and / or" includes any and all combinations of one or more items in the associated listed items. As used herein, phrases such as "between X and Y" and "between about X and Y" should be interpreted as including X and Y. As used herein, phrases such as "between about X and Y" mean "between about X and about Y". As used herein, phrases such as "from about X to Y" mean "from about X to about Y".

[0082] The embodiments of the above disclosure have been given for the purpose of illustration and to enable one of ordinary skill in the art to practice the disclosure, but the disclosure is not intended to be exhaustive or limited to the forms disclosed. Many insubstantial modifications and variations will be apparent to one of ordinary skill in the art without departing from the scope and spirit of the disclosure. The scope of the claims is intended to broadly cover the disclosed embodiments and any such modifications. In addition, the following clauses represent additional embodiments of the disclosure and should be considered within the scope of the disclosure:

[0083] Item 1, a mass flow meter, the mass flow meter comprising: a flow path through the mass flow meter, wherein the flow path includes a first cavity and a second cavity; a laminar flow element adjacent to the first cavity and the second cavity, wherein the first cavity is upstream of the laminar flow element and the second cavity is downstream of the laminar flow element; a pressure transducer positioned in at least one of the first cavity or the second cavity, wherein the pressure transducer includes at least one diaphragm, and wherein the pressure transducer measures a linear and nonlinear response of the at least one diaphragm to a first pressure to determine a voltage signal indicative of the pressure; and converting a pressure reading obtained from the pressure transducer into a signal indicative of a mass flow rate through the laminar flow element.

[0084] Item 2, a mass flow meter as described in Item 1, wherein the mass flow meter communicates with a controller, the controller being operable to receive a set point signal indicative of a desired flow rate through the laminar flow element; and a control valve drive signal so that the signal indicative of the mass flow rate through the laminar flow element substantially matches the received set point signal.

[0085] Clause 3. The mass flow meter of clause 1, wherein the diaphragm is rated for a pressure range of 0 to 50 psi.

[0086] Clause 4. The mass flow meter of clause 1, wherein the rated performance of the diaphragm at pressures less than 5 psi is in a linear region and the rated performance at pressures greater than 5 psi is in a progressively non-linear region.

[0087] Clause 5. The mass flow meter of clause 1, wherein the pressure transducer is rated for a pressure in a non-linear performance region of the pressure transducer that exceeds five times the pressure in a linear performance region.

[0088] Clause 6. A mass flow meter as described in Clause 2, wherein a control valve is positioned upstream of the first cavity, and the mass flow meter uses a flow meter based primarily on m=K*(P1 2 -P2 2) to calculate compressible laminar flow, and wherein a control valve drive signal is used to position the control valve.

[0089] Clause 7. A mass flow meter as described in clause 2, wherein a control valve is positioned upstream of the first cavity and the mass flow meter uses an equation based primarily on m=K*P1 to calculate the acoustic flow, and wherein a control valve drive signal is used to position the control valve.

[0090] Item 8, a mass flow meter as described in Item 2, wherein a control valve is positioned downstream of the second chamber, and the mass flow meter uses an equation primarily based on m=K*(P1-P2) / (P1=P2) / 2) to calculate laminar flow, and wherein a control valve drive signal is used to position the control valve.

[0091] Clause 9, a mass flow meter as described in clause 1, wherein the pressure transducer is an absolute pressure sensor, and wherein the mass flow meter also includes a differential pressure sensor, and wherein the differential pressure sensor includes at least one diaphragm, and wherein the differential pressure sensor measures a linear and nonlinear response to a difference between a second pressure and a third pressure on both sides of the at least one diaphragm to determine a voltage signal indicative of the pressure difference.

[0092] Clause 10, a mass flow meter as described in Clause 1, wherein the pressure transducer includes a first differential pressure sensor and a second absolute pressure sensor, wherein the first differential pressure sensor and the second absolute pressure sensor measure linear and nonlinear responses of one or more diaphragms to determine a voltage signal indicative of the first pressure.

[0093] Item 11. A mass flow meter as described in Item 1, wherein the pressure transducer is a first pressure sensor, and wherein the mass flow meter further comprises a second absolute pressure sensor, and wherein the absolute pressure sensors each comprise at least one diaphragm, and wherein each absolute pressure sensor measures the linear and nonlinear responses of the corresponding at least one diaphragm to the pressure and the second pressure, respectively, to determine voltage signals indicative of the pressure and the second pressure.

[0094] Clause 12. The mass flow meter of clause 1, wherein a deflection of the diaphragm at a maximum rated use pressure of the pressure transducer is greater than 50% of a thickness of the diaphragm.

[0095] Clause 13. The mass flow meter of clause 1, wherein the deflection of the diaphragm at the maximum rated pressure of the pressure transducer is greater than 100% of the thickness of the diaphragm.

[0096] Clause 14. The mass flow meter of clause 1, wherein a deflection of the diaphragm at a maximum rated pressure of the pressure transducer is greater than 200% of a thickness of the diaphragm.

[0097] Clause 15. The mass flow meter of clause 1, wherein the mass flow meter is configured to measure pressure in a non-linear region of the pressure transducer, wherein the non-linear performance is three times greater than a 1% best fit straight line model.

[0098] Clause 16. The mass flow meter of clause 1, wherein the mass flow meter is configured to measure pressure in a non-linear region of the pressure transducer, wherein the non-linear performance is eight times greater than a 1% best fit straight line model.

Claims

1. A mass flow meter, comprising: a flow path through the mass flow meter, wherein the flow path includes a first cavity and a second cavity, a laminar flow element adjacent to the first cavity and the second cavity, wherein the first cavity is upstream of the laminar flow element and the second cavity is downstream of the laminar flow element, a pressure transducer positioned in at least one of the first cavity or the second cavity, wherein the pressure transducer includes at least one diaphragm, and wherein the pressure transducer measures a linear and nonlinear response of the at least one diaphragm to a first pressure to determine a voltage signal indicative of the pressure; and The pressure reading obtained from the pressure transducer is converted into a signal indicative of mass flow through the laminar flow element.

2. The mass flow meter according to claim 1, wherein: The mass flow meter is in communication with a controller, the controller being operable to: receiving a set point signal indicative of a desired flow rate through the laminar flow element; and A valve drive signal is controlled such that the signal indicative of mass flow through the laminar flow element substantially matches the received set point signal.

3. The mass flow meter according to claim 1, wherein: The diaphragm is rated for a pressure range of 0 to 50 psi.

4. The mass flow meter according to claim 1, wherein: The diaphragm is rated for a linear region at pressures less than 5 psi and is rated for a primarily non-linear region at pressures greater than 5 psi.

5. The mass flow meter according to claim 1, wherein: The pressure transducer is rated for a pressure in a non-linear performance region of the pressure transducer that exceeds the pressure in a linear performance region by a factor of twenty.

6. The mass flow meter according to claim 2, wherein: The control valve is positioned upstream of the first chamber, and the mass flow meter uses a mass flow meter based primarily on m=K*(P1 2 -P2 2 ) to calculate compressible laminar flow, and wherein a control valve drive signal is used to position the control valve.

7. The mass flow meter according to claim 2, wherein: A control valve is positioned upstream of the first cavity, and the mass flow meter uses an equation based primarily on m=K*P1 to calculate acoustic flow, and wherein a control valve drive signal is used to position the control valve.

8. The mass flow meter according to claim 2, wherein: A control valve is positioned downstream of the second cavity and the mass flow meter uses an equation primarily based on m=K*(P1-P2) / (P1=P2) / 2) to calculate laminar flow and wherein the control valve is positioned using a control valve drive signal.

9. The mass flow meter according to claim 1, wherein: The pressure transducer is an absolute pressure sensor, and wherein the mass flow meter further comprises a differential pressure sensor, and wherein the differential pressure sensor comprises at least one diaphragm, and wherein the differential pressure sensor measures a linear and nonlinear response to a difference between a second pressure and a third pressure on either side of the at least one diaphragm to determine a voltage signal indicative of the pressure difference.

10. The mass flow meter according to claim 1, wherein: The pressure transducer includes a first differential pressure sensor and a second absolute pressure sensor, wherein the first differential pressure sensor and the second absolute pressure sensor measure linear and non-linear responses of the at least one diaphragm to determine a voltage signal indicative of the first pressure.

11. The mass flow meter according to claim 1, wherein: The pressure transducer is a first pressure sensor, and wherein the mass flow meter further comprises a second absolute pressure sensor, and wherein the absolute pressure sensors each comprise at least one diaphragm, and wherein each absolute pressure sensor measures a linear and nonlinear response of the corresponding at least one diaphragm to the pressure and the second pressure, respectively, to determine a voltage signal indicative of the pressure and the second pressure.

12. The mass flow meter of claim 1, wherein: The deflection of the diaphragm at the maximum rated use pressure of the pressure transducer is greater than 50% of the thickness of the diaphragm.

13. The mass flow meter of claim 1, wherein: The deflection of the diaphragm at a maximum rated pressure of the pressure transducer is greater than 100% of the thickness of the diaphragm.

14. The mass flow meter of claim 1, wherein: The deflection of the diaphragm at the maximum rated pressure of the pressure transducer is greater than 200% of the thickness of the diaphragm.

15. The mass flow meter of claim 1, wherein: The mass flow meter is configured to measure pressure in a non-linear region of the pressure transducer, wherein the non-linear performance is three times greater than a 1% best fit straight line model.

16. The mass flow meter of claim 1, wherein: The mass flow meter is configured to measure pressure in a non-linear region of the pressure transducer, wherein the non-linear performance is eight times greater than a 1% best fit straight line model.

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