Valve assembly and valve system used for controlling flow rate of fluid

Abstract

To provide a mass flow meter.SOLUTION: A mass flow meter includes a flow pathway through the mass flow meter, the flow pathway comprising a first cavity and a second cavity. The mass flow meter also includes a laminar flow element adjacent to the first cavity and the second cavity, the first cavity being upstream of the laminar flow element and the second cavity being downstream of the laminar flow element. A pressure transducer is positioned in at least one of the first cavity or the second cavity, includes at least one diaphragm and measures linear and non-linear responses of the at least one diaphragm to a first pressure to determine a voltage signal indicative of a pressure. The mass flow meter converts a pressure reading value obtained from the pressure transducer into a signal indicative of a mass flow rate through the laminar flow element.SELECTED DRAWING: Figure 1

Description

[Background technology]

[0001] Equipment used in the manufacture of semiconductor wafers is required to operate with high precision to maintain desired production yields. In the process of producing integrated circuits, semiconductor wafers are treated with certain chemicals in a process chamber. Mass flow controllers (MFCs) are used to deliver these chemicals to the process chamber in a consistent manner and at precise flow rates. This can be extremely challenging as MFCs must hold very tight accuracy, operate at multiple set points, and be constantly stopped and restarted during the wafer manufacturing process. To manage such accuracy, current state of the art MFCs are equipped with processor-based control units, numerous sensors, and advanced diagnostic systems.

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

[0003] [Figure 1] FIG. 1 is a schematic illustration of a pressure-based mass flow controller having a flow sensor upstream of a valve in accordance with certain embodiments of the present disclosure.

[0004] [Diagram 2] 1 is a schematic illustration of a combination absolute and differential pressure transducer assembly in accordance with certain embodiments of the present disclosure;

[0005] [Figure 3A] 1 is an illustration of a pressure sensor, in accordance with certain example embodiments. [Figure 3B] 1 is an illustration of a pressure sensor, in accordance with certain example embodiments.

[0006] [Figure 4]FIG. 1 is an illustration of performance modeling of a prototype MFC implemented in accordance with one embodiment of the present teachings, having a dominant linear range from 0 psi to 5 psi and a non-linear range from 5 psi to 60 psi.

[0007] [Diagram 5] FIG. 1 is an illustration of test data showing performance characteristics (sensor sensitivity and nonlinearity) of a pressure sensor implemented in accordance with one embodiment of the present invention, illustrating the improved performance of the embodiment when extending the device's range of use into the nonlinear range.

[0008] [Figure 6] FIG. 1 is an illustration showing a comparison of the performance of a conventional sensor used in an MFC and a sensor used in an MFC implemented in accordance with one embodiment of the present invention.

[0009] [Figure 7] FIG. 1 is an illustration of an aging test showing the stability over time of a prototype pressure sensor implemented in accordance with one embodiment of the present invention.

[0010] [Figure 8] FIG. 2 is an illustration of a computing machine and system application modules in accordance with certain example embodiments.

[0011] [Figure 9] FIG. 1 is an illustration of a comparison of deflection and nonlinearity between a conventional 50 PSI linear range pressure transducer using a thicker 25 micron (micrometer) diaphragm and a 5 PSI linear range pressure transducer of an embodiment of the present invention using a thinner 10 micron diaphragm. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The depicted diagrams are merely examples and are not intended to assert or imply any limitation with respect to the environment, architecture, design, or process in which different examples may be implemented.

[0013] The present invention relates generally to methods and systems for controlling the mass flow rate 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 refer to any type of substance in any state capable of flowing. The term "gas" is used herein to refer to any fluid whose density is substantially dependent on absolute pressure, such as ideal or non-ideal gases, vapors, and supercritical fluids. The term "liquid" is used herein to refer to any fluid whose density is substantially independent of absolute pressure.

[0014] Diaphragms are used in pressure sensors to convert deflections caused by pressure acting on the diaphragm into a voltage signal that the MFC uses to calculate flow rate. The overpressure rating of a pressure sensor is the maximum pressure the device can experience without introducing a calibration shift of the material. The overpressure rating of a pressure sensor is typically four times its full-scale rating. The full-scale rating has historically been the point at which the PT displays a TBNL of 1%. Many modern pressure sensors are manufactured by utilizing semiconductor fabrication techniques to form extremely small silicon diaphragms with piezoelectric limiting elements located at high strain locations on the silicon diaphragm. Silicon, being single crystal, is an effective material for diaphragm applications. In accordance with the teachings of the present invention, with a properly tailored design, silicon-based diaphragms can be deflected well beyond the linear pressure deflection range (primarily bending-based mechanisms) and into an extended nonlinear pressure deflection range (primarily membrane-based mechanisms) without generating localized material dislocations or stress rises that can cause yielding and permanent calibration shifts.

[0015] The teachings of certain embodiments of the present invention allow for the implementation of improved MFCs that utilize pressure sensors that provide a large ratio of maximum overpressure to annual zero point drift, regardless of the linearity of the signal. This ratio determines the stable dynamic range of the pressure-based MFC over the course of a year. The magnitude of the pressure transducer's annual zero point drift causes long-term pressure measurement errors primarily at low flow rates, and determines the minimum flow rate at which the MFC's flow error can be tolerated for use. The annual drift of a pressure transducer is generally a percentage of its linear full scale. In industry, an annual drift of 0.05% of the predominant linear full scale is generally acceptable for annual measurements. As shown by embodiments of the present invention, if the same transducer can be used in the nonlinear region (without material damage), for example, with pressure readings 10 times its linear limit, the annual drift at 0.05% linear full scale is only 0.005% of its maximum overpressure or nonlinear full scale. Thus, by utilizing the nonlinear region of the converter, an MFC implemented in accordance with the teachings of the present invention has significantly improved year-to-year stability over its maximum operating range, thereby significantly improving the performance and value of the MFC. As another advantage, the increased operating range of the MFC of various embodiments of the present invention allows a single MFC to replace two conventional MFCs.

[0016] Although the making and using 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 a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative and do not define the scope of the present disclosure. For purposes of clarity, the present disclosure may not describe all features of an actual implementation.

[0017] Unless otherwise indicated, all numbers expressing properties such as amounts of components, molecular weights, reaction conditions, and the like used in this specification and the related claims are understood to be modified in all instances by the term "about". Thus, unless indicated to the contrary, the numerical parameters set forth in the following specification and the appended claims are approximations that may vary depending on the desired properties sought to be obtained by the examples of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. It should be noted that when "about" is present at the beginning of a numerical list, the "about" modifies each numerical value in the numerical list. Furthermore, in some numerical listing ranges, some lower limits recited may be greater than some upper limits recited. Those skilled in the art will recognize that a selected subset will require the selection of an upper limit that exceeds the selected lower limit. Furthermore, although the voltage signals discussed herein are discussed as positive voltages, negative voltage signals or differential voltage signals can be generated, used, or detected without departing from the scope of the present invention.

[0018] Provided herein is a valve assembly for controlling a fluid flow rate. The valve assembly includes a valve block having an upstream reservoir, a downstream reservoir, and a valve seat for communicating a fluid from an upstream location to a downstream location. The valve assembly further includes a stand-alone valve having a movable member, a sensor chip package having at least one sensor coupled to the stand-alone valve, and a controller interface. The controller interface transmits at least one measured parametric value provided by the at least one sensor and receives a control signal used to adjust a valve stroke of the stand-alone valve. The control signal is determined based on the at least one measured parametric value.

[0019] Also presented herein is a fluid processing system for use in a manufacturing facility. The fluid processing system includes a valve block, a stand-alone valve, an upstream fluid source fluidly coupled to the stand-alone valve, a downstream process tool fluidly coupled to the stand-alone 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 an MFC. As used herein, downstream or downstream side refers to the position or side furthest from the fluid source.

[0020] The valve block includes an upstream reservoir, a downstream reservoir, and a valve seat for communicating fluid from an upstream location to a downstream location. The standalone valve has a movable member, and the sensor chip package has at least one sensor coupled to the valve. The control unit includes an interface communicatively coupled to the standalone valve and the sensor chip package. The control unit generates a control signal used to control a stroke of the standalone valve based on at least one parametric value from the sensor chip package.

[0021] 1 shows a schematic illustration 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. The MFC 5 operates on the principle that changes in fluid flow rate cause 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 illustrated embodiment, the MFC 5 comprises a power connector 10, a flow path 15, a flow control valve assembly 20, and at least one embodiment of a combination absolute and differential pressure transducer assembly 25. The MFC 5 further comprises an inlet port 30 for introducing fluid into the device, an outlet port 35 through which the fluid exits (e.g., to a processing chamber), and a laminar flow element 40. In some embodiments, the inlet port 30 may further comprise an inlet orifice block 31 disposed within the inlet port 30 and blocking at least a portion of the flow of fluid therethrough. Fluid may enter the MFC 5 via the inlet port 30 and flow within the MFC 5 along a flow path 15. In some embodiments, the flow path 15 may be maintained at a constant temperature. The flow control valve assembly 20 is disposed along the flow path 15 adjacent the outlet port 35 and downstream of both the combination absolute and differential pressure transducer assembly 25. The flow control valve assembly 20 may comprise a proportional control valve (e.g., a solenoid or piezo control valve) that is adjustable to control the amount of fluid through the MFC 5. The flow control valve assembly 20 can actuate the control valve at any desired speed sufficient to control the flow rate through the flow control valve assembly 20. Additionally, the actuation speed can be programmable and adjustable such that the control valve can be actuated continuously or in steps.

[0023] Continuing with the description of FIG. 1, the MFC 5 further comprises a proportional-integral-derivative (hereinafter "PID") controller 45, which may include logic, circuitry, memory, and one or more processing elements (processors). In this example, a PID controller is illustrated, but it should be understood that the PID controller is only one of many potential valve controllers, as would be readily apparent to one of ordinary skill in the art. For example, in some embodiments, the PID controller 45 may be replaced with 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 application. The controller may be implemented as either hardware or firmware. The PID controller 45 is configured to control the position of the valve in the flow control valve assembly 20 according to a set point indicative of a desired mass flow rate. For example, in one embodiment, the PID controller 45 receives absolute and differential pressures from the combined absolute and differential pressure transducer assembly 25 and a set point signal indicative of a desired flow rate through the laminar flow element 40. The PID controller 45 uses the received information to convert knowledge of both the absolute pressure, the differential pressure, and the properties and characteristics of the fluid in the laminar flow element 40 into a signal indicative of the mass flow rate through the laminar flow element 40. For example, in one embodiment, the PID controller 45 can relate the pressure drop to a volumetric flow rate and convert the volumetric flow rate to a mass flow rate with density compensation at a given temperature and pressure. The PID controller 45 can then generate a valve drive signal to control the flow control valve assembly 20 such that the signal indicative of the mass flow rate through the laminar flow element 40 substantially matches the received set point signal. For example, in one embodiment, the control valve drive signal is generated based on an error signal that is the difference between a set point signal indicative of a desired mass flow rate of the fluid and a feedback signal related to the actual mass flow rate determined by the PID controller 45 using the combined absolute and differential pressure transducer assembly 25. In some examples, the desired flow rate of the set point signal is 10% or less. In some examples, the outlet pressure may be greater than about 2 psia.

[0024] In one embodiment, the circuit board 50 can be attached to the back of the combination absolute 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 any transducer-specific balance resistors or other trim resistors. In some embodiments, the circuit board 50 can have a memory component configured to store data, such as, but not limited to, calibration data for the combination absolute and differential pressure transducer assembly 25. The circuit board 50 can include one or more accelerometers to enable automatic compensation for the effects of gravity or acceleration on the measured pressure. The circuit board 50 can also include instrumentation amplifiers or other amplifiers and other components configured to amplify the output signals of the absolute and differential pressure transducers. The circuit board 50 can be supported by pins from the combination absolute and differential pressure transducer assembly 25 that provide electrical connections to the absolute and differential pressure transducers included within the combination absolute and differential pressure transducer assembly 25. In one embodiment of the invention, at least one of the pressure sensors comprising pressure transducer assembly 25 is operable to generate voltage readings in response to both linear and non-linear changes to the diaphragm of the pressure sensor. In another embodiment of the invention, at least one of the pressure sensors comprising pressure transducer assembly 25 is operable to generate voltage readings in response to non-linear changes to the diaphragm of the pressure sensor. In yet another embodiment of the invention, at least one of the pressure sensors comprising pressure transducer assembly 25 is operable to generate voltage readings in response to pressures that fall into a non-linear region of operation of the diaphragm of the pressure sensor.

[0025] 2 illustrates an alternative embodiment of an MFC, generally 305. The MFC 305 is substantially similar to the MFC 5 of FIG. 1, except that the combined absolute and differential pressure transducer assembly 25 of FIG. 1 is replaced with a differential pressure transducer assembly 310 that 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 in the same location as the differential pressure transducer. Instead, the absolute pressure transducer can be located separately from the differential pressure transducer assembly 310 at a location upstream of the laminar flow element 40, e.g., at a location 315 in fluid communication with the feed volume 41, or alternatively, at a location downstream of the laminar flow element 40, e.g., at a location 320 in fluid communication with the holding volume 42.

[0026] Generally, the error in the pressure sensor's pressure reading determines the minimum flow rate at which the pressure sensor can be used to adequately measure flow. More specifically, smaller flow rates generate smaller pressure signals, which eventually lead to larger non-flow induced false signals, such as sensor zero drift over the years, which eventually become problematic. As the shrinking pressure induced signal (as flow rates get smaller) becomes indistinguishable from the non-pressure induced false signals, flow calculations based on the composite signal become increasingly inaccurate to the point of being unusable. For example, a 1% best fit at 5 psi linear test pressure transducer that can be used in its non-linear range up to 50 psi can be combined with a flow restricting element to achieve full flow at 50 psi. The absolute error of the sensor is 0.05% of 5 psi (linear rating), but because the sensor can see 50 psi at full flow, the absolute error of the sensor is 0.005% of the 50 psi working pressure, resulting in a 10x reduction in flow error compared to the % full scale working range of a traditional 1% best fit at 5 psi linear test pressure transducer that cannot be used beyond its 5 psi rating. As discussed, such use is limited due to possible damage to the diaphragm design at higher psi and must be combined with a less restrictive flow element that produces a full-scale flow rate at 5 psi full scale. For purposes of the above, error is defined as the pressure transducer's pressure measurement error divided by the full scale use range ("FSUR"), or %FSUR.

[0027] Because the pressure range that a pressure sensor can accurately measure is directly related to the flow rate range that can be accurately measured by the mass flow controller that uses the pressure sensor, a mass flow controller utilizing a NL sensor with a maximum working pressure will be able to measure higher flow rates and will have a lower percent error in measured flow rate, or %FSUR, than a mass flow controller that is limited to a lower maximum pressure with a 1% best fit straight line value when measuring flow rate.

[0028] The designed flow range operation of a mass flow controller, in one embodiment with 1% reading accuracy, is referred to herein as the flow accuracy range. As discussed above, in current MFCs, this is typically defined near the dominant linear operating range of the pressure sensor, i.e., when the linear response of the pressure sensor dominates any non-linear response. At flow rates above or below such flow accuracy range, the accuracy of the flow measurement decreases. For example, a conventional mass flow controller can accurately measure flow rates between 10 sccm and 100 sccm using the linear range of a pressure sensor that can accurately measure pressures between 0.5 psi and 5 psi. Similarly, a conventional mass flow controller can accurately measure flow rates between 100 sccm and 1000 sccm using the linear range of a pressure sensor that can accurately measure pressures between 5 psi and 50 psi.

[0029] In one embodiment of the invention, the laminar flow element is designed to operate accurately over both the 0.5 psi to 5 psi and 5 psi to 50 psi ranges using a pressure transducer that does not suffer material damage when operating at pressures between 0 psi and 50 psi where the performance of the pressure transducer is increasingly dominated by its non-linear characteristics with increasing pressure. More specifically, the differential pressure transducer assembly 310 includes at least one pressure transducer that is designed to operate in the linear and non-linear ranges of the diaphragm contained within the transducer. Thus, in one embodiment of the invention, by using such a pressure transducer, a single MFC can be designed with a flow accuracy range that covers a flow range of 10 sccm to 1000 sccm, and the new MFC can replace two conventional MFCs that were previously required to cover the same flow range. As used herein, the linear range or linear region refers to the pressure range where the linear characteristics of the pressure sensor / pressure transducer dominate the non-linear characteristics of the pressure sensor / pressure transducer. Although the non-linear characteristics of the pressure sensor / pressure transducer may still be present, they are generally less significant than the linear characteristics. Conversely, the nonlinear range or region refers to a pressure range where the nonlinear characteristics of the pressure sensor / transducer are prominent compared to the linear characteristics of the pressure sensor / transducer. Furthermore, the linear characteristics of the pressure sensor / transducer may still be present, but they will not be dominant enough to ignore the nonlinear components. It should be understood that at certain pressures (e.g., 5 psi in some embodiments), both the linear and nonlinear characteristics may be important and should be considered in the design and operation of the pressure sensor / transducer. In particular, in current MFCs, nonlinearity is considered an undesirable complication. In the present invention, the nonlinearity is directly utilized to determine the sensed pressure over a wider range, and the sensed pressure is used to calculate the flow rate over a wider range.

[0030] Existing MFCs designed with transducers intended for use at pressures between 0 psi and 5 psi will damage the transducer and degrade performance when exposed to pressures significantly greater than 5 psi. More specifically, the diaphragm of a pressure transducer designed for low pressure will deform and lose shape or break when exposed to higher pressures (in some embodiments, performance issues and pressure measurement inaccuracies occur when pressures exceed 400% of the 1% nonlinearity rating). More specifically, pressure sensors used by conventional MFCs have an operating limit of four times their designed linearity range before being permanently damaged, but are typically not used beyond two times the linearity range to allow for a safety factor.

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

[0032] 3A and 3B show schematic diagrams of absolute and differential pressure sensors, respectively. In FIG. 3a, volume 402 is isolated from volume 404 by pressure-sensing diaphragm 406. It should be noted that diaphragm 406 may be thinner, more flexible, tapered, and of different widths and thicknesses than those revealed in that figure. Diaphragm 406 may include a pumping element that connects or performs some of the functions of sensor 408, located directly on the surface of the diaphragm or integrated with the diaphragm. As is well understood in the art, an isolation diaphragm (not shown and not relevant 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 for its resistance to corrosion in the presence of fluids expected to be present during operation of the MFC. Alternatively, diaphragm 406 may be a mono-single or a composite material having multiple layers of polysilicon, germanium, titanium, polyethylene, metal, or different materials. Such material selection may depend on the particular application, the fluid used, the desired flow range, life span, flexibility, and resilience. Such selection may also depend on the technical and economic feasibility of the material for a particular application. For example, while within the scope of the teachings of the present invention, stainless steel and other metals may not be economically or technically feasible for manufacturing a miniature pressure sensor using current manufacturing techniques. The dimensions of the diaphragm 406 may also be selected based on the aforementioned and desired performance characteristics of the diaphragm 406. In particular, the thickness and diameter of the diaphragm 406 may be manufactured or selected based on the desired pressure range, stiffness, and linear and nonlinear characteristics. In one embodiment of the present invention, the diameter of the diaphragm 406 used in the pressure sensor is increased and the thickness of the diaphragm is decreased compared to the previous 5 psi device. Such changes facilitate an increase in the relative magnitude of the nonlinear effects to the linear components.Such modifications also prevent damage to the diaphragm by the linear component in each case, compared to conventional MFC diaphragms, and allow the pressure sensor to operate in the nonlinear region without material damage or measurement errors.

[0033] To better understand the above, it is useful to understand bending and membrane action. For the sake of discussion, we will use the simplified cases of bending in a beam and membrane action in a chord. For more complex geometries, such as the deflection of a diaphragm when pressure is applied to one side of the diaphragm, both effects are present. In reality, mass flow controller diaphragms are generally shaped differently than chords or beams (e.g., various cross sections, tapers, curvatures, variable diameters and thicknesses, etc.). However, this simplification is illustrative of the linear and non-linear performance of the diaphragm. Those skilled in the art will appreciate that the shape of the diaphragm dictates its own "bending" (or, more accurately, "deflection" when one deviates from the simplified beam / chord configuration), which is necessarily more complicated than the following description and illustrated equations, as the shape of the diaphragm changes compared to a simple beam. However, the following description is sufficient to teach the basic principles of linear and non-linear behavior and the mechanisms at work in a diaphragm. More specifically, the bending stiffness of a rectangular beam is proportional to the cube of the thickness ("t") of the beam multiplied by the width ("b") of the beam.

[0034] K bending ≒bt 3 ≒t 3 (Formula 1)

[0035] Similarly, the thickness and diameter of the diaphragm 406 can be manufactured or selected to affect the range, stiffness, and linear and non-linear characteristics of the diaphragm itself.

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

[0037] K elongation ≒bt≒t 1 (Formula 2)

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

[0039] The above ignores the membrane effect of a forcer applied to the diaphragm, as described later below.

[0040] The above principles are applied to a sensor 408 coupled to the diaphragm 406. In one embodiment, the sensor 408 is a capacitance sensor. Alternatively, the sensor 408 may be a strain gauge, a piezoelectric sensor, a resistive sensor, or any other suitable sensor. In general, deflection of the diaphragm 406 induces a measurable electrical signal proportional to the deflection by measuring a change in capacitance, resistance, voltage, current, or other electrical, electromechanical, or electromagnetic property.

[0041] With respect to the operation of FIG. 3A, the introduction of fluid into the volume 402 exerts a force on the diaphragm 406. The higher the pressure in the volume 402 relative to a reference pressure in the volume 406, the greater the force acting on the diaphragm 406. Depending on the properties, dimensions, and other characteristics of the diaphragm 406, such force results in a deflection of the diaphragm 406. The magnitude of such deflection is measured by the sensor 408 and is generally linear for a particular range of forces (corresponding to a particular range of pressures in the volume 402). In other words, an increase in force generally causes an increase in the magnitude of the deflection of the diaphragm 406. Initially, such an increase occurs according to a linear relationship between two variables that can be measured by the sensor 408. Such a linear relationship is important for the operation of a pressure sensor in a mass flow controller, whose purpose is to monitor pressure and thereby determine flow rate, as described above. For example, in implementing a pressure sensor for an appropriate flow rate range, a table can be utilized to store data used to plot a linear x and y relationship between the magnitude of such deflection and the amount of pressure applied to the sensor 408.

[0042] As the deflection of the diaphragm increases, this increase is increasingly caused by the nonlinear relationship between force and deflection. Currently, MFCs do not utilize pressure sensors designed to allow operation in the highly nonlinear range due to the damage problems described above, and most commercially available pressure sensors have overpressure limits that are three or four times the designed linearity range. Various embodiments of the disclosed invention can utilize MFCs that are more than 20 times the designed linearity range. In one embodiment of the invention, the pressure sensor is designed such that the maximum design deflection of the diaphragm (linear performance region) exceeds the thickness of the diaphragm, where the thickness is the thickness of the region of the diaphragm where the deflection occurs. An engineering rule of thumb is that the nonlinear component becomes significant when the deflection approaches a mid-range percentage of the diaphragm thickness. In another embodiment of the invention, the pressure sensor is designed such that the maximum design deflection of the diaphragm exceeds two times the thickness of the diaphragm. In another embodiment of the invention, the pressure sensor is designed such 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 such 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 the deflection occurs. In another embodiment of the invention, the pressure sensor is designed such 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 such that the maximum design deflection of the diaphragm ranges between half and twice the thickness of the diaphragm.

[0044] FIG. 3B illustrates the use of a differential pressure sensor 410. A differential pressure sensor can eliminate a source of error that can occur with an absolute pressure sensor. In FIG. 3B, volume 412 is isolated from volume 414 by diaphragm 416. In one embodiment, two pressure sensors 418 and 420, e.g., absolute pressure sensor 418 and differential pressure sensor 420, can be used in a single housing. The pressure measurements of pressure sensors 418 and 420 can be used in combination to determine a change in flow rate, as discussed above. The discussion above regarding diaphragm 406 of FIG. 3A also applies to diaphragm 416.

[0045] As previously mentioned, the dimensions and other characteristics of the diaphragm in an MFC may be selected based on the particular application, the fluid used, the desired flow range, the maximum operating pressure, life, flexibility, resilience, or other desired performance characteristics. One of the most important of such performance characteristics is the desired flow range (the range of flow rates expected to be measured and controlled by the MFC), which corresponds to the range of pressures expected to be measured by a sensor such as sensors 408 and 420 or 418. More specifically, only certain diaphragms have historically been used over certain flow ranges because of the need to maintain a linear relationship between pressure and the amount of deflection of the diaphragm. Thus, the performance characteristics of the diaphragm, including but not limited to the dimensions of such diaphragms, may be selected by the designer of the pressure sensor or MFC based on the expected range of flow rates required for a particular MFC. Outside such flow ranges (pressures below or above the measured pressure corresponding to the flow rates measured by the MFC within such flow range), the deflection and physical changes of the selected diaphragm no longer follow a linear relationship with pressure. For any diaphragm, there are both linear and nonlinear responses to the diaphragm's reaction to pressure. However, within the intended flow range, the linear response dominates the nonlinear response such that when measuring the change in the diaphragm as pressure changes, an overall linear or first order relationship (as can be stored in a table in the MFC's memory) still predominates. The limited range of the diaphragm is an important design limitation for MFCs. A particular MFC can only be used for a certain range of flow rates because linear performance is only possible over a certain pressure range and therefore a certain flow rate range. If a wider range of performance is required, then either multiple MFCs must be used (increasing system cost, complexity, maintenance needs, and speed of performance) or different MFCs must be substituted for different flow rate ranges when required (increasing cost, system downtime, and complexity).

[0046] When an MFC is operating outside of its intended flow range, the readings of a sensor, such as sensor 408, become increasingly affected by the nonlinear components of a diaphragm, such as diaphragm 406. To better understand this, there are two mechanisms that occur in a diaphragm when it is deflected by a force or pressure. The first is a deflection mechanism similar to bending in beam theory, where the deflection is linear with respect to the force, as discussed above. The second is a stretching mechanism, which is membrane theory and is nonlinear, where the material stretches to accommodate the required stretch in the centerline length of the diaphragm. Membrane theory is based on the amount of "stretch" required, and the magnitude is dependent on the angle of the "stretch". Both the deflection mechanism and the membrane mechanism are always present, but within the linear flow range of the diaphragm the effect of the membrane is not significant. For small deflections, the geometry that deflects a flat diaphragm produces minimal "stretch" and the force resisting the membrane stretch is countered by the force resisting the diaphragm deflection. In one embodiment, the sensing diaphragm of the first pressure sensor can operate predominantly in a linear range until the deflection of such sensing diaphragm is greater than 50% of the thickness of the diaphragm. In another embodiment, the membrane of the second pressure sensor can operate in a linear range until the deflection of such membrane is greater than the thickness of the diaphragm. After such deflection, the non-linear behavior of the membrane must be considered.

[0047] As the diaphragm deflects larger, the increase in "stretch" per unit deflection becomes larger, and eventually the membrane forces are no longer insignificant compared to the bending forces, and nonlinear forces increasingly cause the deflection curve to grow. Initially, the forces driving the growth of the deflection curve are dominated by linear deflection mechanisms. As the deflection increases, the nonlinear membrane forces become significantly larger. For simplicity, when in the linear region, consider the diaphragm to be a simple flat beam with fixed supports at both ends when subjected to a relatively small deflection due to a force at its center. For small loads / deflections, the beam does not need to stretch much to minimize the deflection and membrane action. Rather, the diaphragm deflects similarly to beam theory, where the deflection is linear with respect to the applied force.

[0048] D=K Geo ×force (equation 3)

[0049] As the deflection increases, the beam stretches at a greater rate, causing membrane forces to increase and nonlinearity to occur. The physical dimensions of the diaphragm affect the linear and nonlinear components of how the diaphragm responds to the forces acting on it from fluid pressure. In bending theory, the stiffness of a square beam is proportional to the cube of the beam's thickness (or depth, "t") times the beam's width ("b").

[0050] K bending ≒bt 3 ≒t 3 (Formula 4)

[0051] In membrane theory, stiffness in extension is proportional to the cross-sectional area of ​​the member. As the diaphragm deflects, the angle of the force vector becomes increasingly non-perpendicular, so the amount of extension per unit of deflection increases.

[0052] K elongation ≒bt≒t 1 (Formula 5)

[0053] where cross-sectional area = width "b" x thickness "t". As an example, if the diaphragm is doubled in thickness, the membrane effect doubles, but the bending contribution increases by a factor of eight. As the diaphragm heats up, the linear range increases, but it becomes about eight times stiffer.

[0054] Combining the linear and nonlinear responses of the diaphragm and expressing it mathematically, the force acting on the diaphragm (the pressure of the fluid in the volume containing the diaphragm) is:

[0055]

number

[0056] (Formula 6)

[0057] where P=pressure, y=deflection, the rest are fixed values ​​for the particular diaphragm, shape, and diaphragm material properties: 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 flow range of a conventionally designed MFC, the measurements of sensor 408, or another pressure sensor as described above, are used by a processor of the MFC, such as processor 510 described below, to measure the linear, non-linear, or a combination of linear and non-linear performance of diaphragm 406 to determine the pressure of the fluid in volume 402. In one embodiment, both a differential pressure sensor and an absolute pressure sensor form sensor 408.

[0059] Referring to FIG. 4, a comparison is shown of a model of an MFC operating in both linear and nonlinear regions with a model of a conventional MFC operating only in the linear region. Both models utilize calculations based on compressible flow equations for laminar flow elements. The MFC implemented according to the teachings of the present invention has a 1%R error operating range between 500 to 1 of the designed minimum flow rate, while the conventional MFC has an operating range between 20 to 1 of the designed minimum detectable flow rate. More specifically, FIG. 7 shows the magnitude of annual sensor drift. At a maximum inlet pressure of 38 psi, at 100% flow rate, the conventional MFC using a 50 psi 1% best fit linear conventional PT has an annual sensor drift of 0.05% of the linear full scale rating, or 0.25 psi / year, while the MFC using a 5 psi 1% best fit linear pressure transducer operable at 50 psi has an annual sensor drift of 0.025 psi / year, a 10-fold improvement.

[0060] Referring to FIG. 5, testing of a prototype pressure sensor implemented in accordance with one embodiment of the teachings of the present invention, having a linear range of 0 psi to 5 psi and a non-linear range of 5 psi to 60 psi, is shown. FIG. 5 shows the calibration curve and the change in the output of the pressure sensor compared to the pressure measured in PSI units. As shown, the performance curve shows a polynomial curve expected from the calculated relationship between pressure and output voltage. Thus, a prototype MFC using this pressure sensor is shown to be successful in tracking pressure, and thus flow rate, up to the non-linear operating region of the pressure sensor.

[0061] Referring to FIG. 6, a comparison of the performance of a conventional sensor used in an MFC and a sensor used in an MFC implemented in accordance with one embodiment of the present invention is illustrated showing the improved performance of such an embodiment. As shown, the pressure sensitivity (rate of change in mV output of the pressure sensor with respect to a change in psi) is 4 times to 14 times more sensitive in the MFC of the present invention over an operating range of 0 psi to 60 psi. As shown in FIG. 6, the response of the measured voltage at the terminals of the pressure transducer of the MFC implemented in accordance with one embodiment of the present invention (linear region up to 5 psi and extending into the nonlinear region up to 60 psi) is 14% nonlinear (shown as a 14% deviation from a best-fit straight line), whereas the measured voltage at the terminals of a standard 50 psi linear pressure transducer is less than 1% nonlinear. Tested data shows that when an embodiment of the present invention is used to measure pressures three times greater than those limited to a 1% best-fit straight line model, the sensitivity of the performance is improved, and the sensitivity of the performance is further improved when at least 8 times greater. Although the zero drift (flow rate measured when no fluid is flowing) is the same between the pressure sensors of the two MFCs, the sensor sensitivity is still about four times more accurate at low pressures, making zero drift less of an issue in the MFC of the present invention. Overall, within 1% accuracy / stability range of the pressure sensor, the MFC of the present invention is a vast improvement over the conventional MFC.

[0062] Referring to FIG. 7, an aging test of a prototype pressure sensor implemented in accordance with one embodiment of the present invention is shown. During a 6-month test, a pressure sensor with a linear range of 5 psi (usable up to 60 psi without material damage) was subjected to varying pressure and temperature changes over a certain time frame as shown. At the end of the 6 months, the drift was less than 0.05% of its linear full-scale error. Given that most MFCs are designed to meet specifications with less than 1% error in full-scale measurement, the MFC of the present invention performs well within such design constraints. Such testing also verified the 1% annual stability assumption of FIG. 6.

[0063] 8, a computing machine 500 and a system application module 600 are shown according to an example embodiment. The computing machine 500 can correspond to various computers, mobile devices, laptop computers, Internet of Things (IoT), servers, embedded systems, or any of the computing systems presented herein. The module 600 can include one or more hardware or software elements, such as other OS applications and user and kernel space applications, designed to facilitate the computing machine 500 to execute the various methods and processing functions presented herein. The computing machine 500 can include various internal 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 570, such as a network interface 560 for communicating with a network such as Cellular / GPS, Bluetooth, WiFi, or Devicenet, EtherCAT, Analog, RS485, and one or more sensors 580.

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

[0065] The processor 510 can be designed to execute code instructions to perform the operations and functions described herein, manage request flow and address mapping, perform calculations and generate commands. The processor 510 can be configured to monitor and control the operation of components in the computing machine. The 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, gate logic, a discrete hardware component, any other processing unit, or any combination or plurality thereof. The 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 certain embodiments, the processor 510 can be a software-based or hardware-based virtual computing machine executing within one or more other computing machines, along with other components of the computing machine 500.

[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 shown as being part of the computing machine, those skilled in the art will understand that the system memory 530 may be separate from the computing machine 500 without departing from the scope of the subject 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 a storage medium 540.

[0067] The 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 memory 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 plurality of such. The storage medium 540 may store one or more operating systems, application programs and program modules, data, or any other information. The storage medium 540 may be part of a computing machine or may be connected to a computing machine. The storage medium 540 may also be part of one or more other computing machines in communication with the computing machine, such as a server, a database server, cloud storage, network attached storage, etc.

[0068] The application module 600 and other OS application modules may include one or more hardware or software elements configured to facilitate a computing machine to execute various methods and processing functions presented herein. The application module 600 and other OS application modules may include one or more algorithms or sequences of instructions stored as software or firmware in association with the system memory 530, the storage medium 540, or both. The storage medium 540 may thus represent an example of a machine or computer readable medium that may store instructions or code for execution by the processor 510. A machine or computer readable medium may generally refer to any medium or media used to provide instructions to the processor 510. Such machine or computer readable media associated with the application module 600 and other OS application modules may include computer software products. It should be understood that the computer software products including the application module 600 and other OS application modules may also be associated with one or more processes or methods for distributing the application module 600 and other OS application modules to a computing machine via a network, any signal-carrying medium, or any other communication or distribution technology. Application module 600 and other OS application modules may also include hardware circuitry or information for configuring the hardware circuitry, such as microcode or configuration information for an FPGA or other PLD. In one example embodiment, application module 600 and other OS application modules may include algorithms capable of performing the functional operations described by the flowcharts (modes of operation) of the computer system presented herein.

[0069] The input / output ("I / O") interface 550 can be configured to couple to one or more external devices, receive data from one or more external devices, and transmit data to one or more external devices. Such external devices, along with various internal devices, may also be known as peripheral devices. The I / O interface 550 can include both electrical and physical connections for coupling various peripheral devices to the computing machine or processor 510. The I / O interface 550 can be configured to communicate data, address, and control signals between the peripheral devices and the computing machine or processor 510. The I / O interface 550 can be configured to implement any standard interface, such as Small Computer System Interface ("SCSI"), Serial Attached SCSI ("SAS"), Fibre 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 multiple interface or bus technologies. I / O interface 550 may be configured to operate as part of, as all of, 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] The I / O interface 520 can couple the computing machine to a variety of input devices, including a mouse, a touch screen, a scanner, an electronic digitizer, a sensor, a receiver, a touch pad, a track ball, a camera, a microphone, a keyboard, any other pointing device, or any combination thereof. The I / O interface 520 can couple the computing machine to a variety of output devices, including a video display, speakers, printers, projectors, haptic feedback devices, automation controls, robotic components, actuators, motors, fans, solenoids, valves, pumps, transmitters, signalers, lights, etc.

[0071] The computing machine 500 may operate in a networked environment, with logical connections through the NIC 560 to one or more other systems or computing machines over a network. 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 a packet-switched network, a circuit-switched network of any topology, and may use any communication protocol. The communication links in the network may involve a variety of digital or analog communication media, such as fiber optic cables, free-space optics, wave guides, electrical conductors, wireless links, antennas, radio frequency communications, and the like.

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

[0073] The processor 510 may be connected to other elements of the computing machine or to the various peripherals 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, the processor 510, the other elements of the computing machine, or any of the various peripherals discussed herein may be incorporated into a single device, such as a system on a chip ("SOC"), system on a package ("SOP"), or ASIC device.

[0074] The embodiments may include a computer program that embodies the functions described and illustrated herein, the computer program being implemented in a computer system that includes instructions stored in a machine-readable medium and a processor that executes the instructions. However, it should be apparent that there may be many different ways of implementing the embodiments in computer programming, and the embodiments should not be construed as being limited to any one set of computer program instructions unless otherwise disclosed in the exemplary embodiments. Furthermore, a skilled programmer would be able to write such a computer program to implement one of the disclosed embodiments based on the accompanying flowcharts, algorithms, and related descriptions in the body of the application. Thus, disclosure of a particular set of program code instructions is not deemed necessary to fully understand how to make and use the embodiments. Furthermore, a person skilled in the art would understand that one or more aspects of the embodiments described herein may be performed by hardware, software, or a combination thereof, such that they may be embodied in one or more computing systems. Furthermore, any reference to an act performed by a computer should not be construed as being performed by a single computer, since two or more computers may perform the act.

[0075] The example embodiments described herein can be used with computer hardware and software to perform the methods and processing functions described above. The systems, methods and procedures 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, computer readable media can include floppy disks, RAM, ROM, hard disks, removable media, flash memory, memory sticks, optical media, magneto-optical media, CD-ROMs, etc. Digital circuitry can include integrated circuits, gate arrays, building block logic, field programmable gate arrays (FPGAs), etc.

[0076] Referring to FIG. 9, a comparison of deflection and nonlinearity is shown between a conventional 50 PSI linear range pressure transducer using a thicker 25 micron diaphragm and a 5 PSI linear range pressure transducer of an embodiment of the present invention using a thinner 10 micron diaphragm. As shown, for the conventional pressure transducer, the nonlinearity in deflection peaks at about 0.03% throughout the pressure range from 0 PSI to 60 PSI. Alternatively, for the nonlinear pressure transducer, the nonlinearity in deflection peaks at about 12% throughout the pressure range from 0 PSI to 60 PSI. Thus, by reducing the thickness of the diaphragm (thereby increasing both the nonlinearity and deflection), the desired nonlinearity and performance of a particular MFM or MFC can be achieved. Also, by reducing the thickness of the diaphragm, bending stress levels can be reduced, allowing for larger deflections without degrading the device. Referring to the discussion of bending and membrane action above, bending creates stresses on the surface of the diaphragm, whereas membrane action creates stresses across the entire cross section of the diaphragm. Current manufacturing techniques may limit the diaphragm thickness to 5 microns for many applications, but the invention is expected to be useful for diaphragms of even smaller thickness. The diameter of the diaphragm can also be used to determine the stiffness of the pressure transducer. In the design of the transducer, both features can be varied simultaneously.

[0077] The example systems, methods, and acts described in the embodiments presented above are exemplary, and in alternative embodiments, certain acts may be performed in different orders, in parallel with one another, omitted entirely, and / or combined between different example embodiments, and / or certain additional acts may be performed, without departing from the scope and spirit of the various embodiments. Accordingly, such alternative embodiments are included in the description herein.

[0078] As used herein, the singular forms "a", "an" and "the" are intended to include the plural, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising" as used herein specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. As used herein, phrases such as "between X and Y" and "between about X and Y" should be interpreted to include 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, an integrated circuit, an application specific integrated circuit, a field programmable gate array, 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 operating in one or more processors (wherein the processor may include one or more microcomputers or other suitable data processing units, memory devices, input / output devices, displays, data input devices such as keyboards or mice, peripherals such as printers and speakers, associated drivers, control cards, power supplies, network devices, docking station devices, or other suitable devices operating under the control of a software system with a processor or other devices), two or more lines of code or other suitable software structures operating in two or more software applications, or other suitable software structures. In one exemplary embodiment, the software may include one or more lines of code or other suitable software structures operating in a general-purpose software application, such as an operating system, and one or more lines of code or other suitable software structures operating in a dedicated software application. As used herein, "couple" and cognate terms such as "couples" and "coupled" may include a physical connection (such as through copper conductors), a virtual connection (such as through randomly assigned memory locations in a data memory device), a logical connection (such as through logic gates in a semiconductor device), any other suitable connection, or a suitable combination of such connections.The term "data" may refer to any suitable structure for using, transporting, or storing data, such as a data field, a data buffer, a data message having a data value and sender / recipient address data, a control message having a data value and one or more operators that cause a receiving system or component to perform some function with the data, or other suitable hardware or software component for the electronic processing of data.

[0080] Generally, a software system is a system that runs on a processor to perform a given function in response to a given data field. For example, a system can be defined by the function that the system performs and the data field on which the system performs the function. As used herein, a NAME system (wherein the NAME is typically the name of the generic function performed by the system) refers to a software system that runs on a processor and is configured to perform a disclosed function on a disclosed data field. Unless a specific algorithm is disclosed, any suitable algorithm known to one of ordinary skill in the art for performing a function with an associated data field is contemplated as being within the scope of this disclosure. For example, a message system that generates a message including a sender address field, a recipient address field, and a message field includes software operating on a processor that can obtain the sender address field, the recipient address field, and the message field from a suitable system or device of the processor, such as a buffer device or system, assemble the sender address field, the recipient address field, and the message field into a suitable electronic message format (such as an email message, a TCP / IP message, or any other suitable message format having sender address fields, recipient address fields, and message fields), and transmit the electronic message using the electronic messaging system and device of the processor over a communication medium, such as a network. One of ordinary skill in the art will be able to provide specific encoding for a particular application based on the above disclosure, which is intended to illustrate exemplary embodiments of the present disclosure, but is not intended to provide guidance to persons other than those skilled in the art, such as persons unfamiliar with programming in a suitable programming language or with processors.Specific algorithms for performing certain functions may be provided in flowchart form or other suitable format, and data fields and associated functions may be shown in an exemplary sequence of operations, which sequence may be rearranged as suitable and is not intended as limiting unless expressly stated to be limiting.

[0081] As used herein, the singular forms "a", "an" and "the" are intended to include the plural, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising" as used herein specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. As used herein, phrases such as "between X and Y" and "between about X and Y" should be interpreted to include 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 above disclosed embodiments are presented for illustrative purposes and to enable those skilled in the art to practice the present disclosure, but the present disclosure is not intended to be exhaustive or limited to the disclosed forms. Many insubstantial modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the present disclosure. The claims are intended to broadly encompass the disclosed embodiments and any such modifications. In addition, the following items represent further embodiments of the present disclosure and should be considered to be within the scope of the present disclosure:

[0083] Item 1. A mass flow meter, a flow path through the mass flow meter, the flow path including a first cavity and a second cavity; a laminar flow element adjacent to the first cavity and the second cavity, with the first cavity upstream and the second cavity downstream; a pressure transducer disposed in at least one of the first cavity or the second cavity, the pressure transducer including at least one diaphragm, the pressure transducer measuring linear and nonlinear responses of the at least one diaphragm to a first pressure to determine a voltage signal indicative of pressure; Equipped with A mass flow meter that converts a pressure reading obtained from the pressure transducer into a signal indicative of mass flow through the laminar flow element.

[0084] Item 2. The mass flow meter communicates with a controller, and the controller receiving a set point signal indicative of a desired flow rate through the laminar flow element; controlling a valve drive signal such that the signal indicative of mass flow through the laminar flow element substantially corresponds to the received set point signal. 2. The mass flow meter of item 1, wherein the mass flow meter is operable as follows:

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

[0086] Item 4. The mass flow meter of item 1, wherein the diaphragm is rated for a linear region of performance at pressures below 5 psi and a gradually non-linear region of performance at pressures above 5 psi.

[0087] Item 5. The mass flow meter of item 1, wherein the pressure transducer is rated when the pressure in the non-linear performance region of the pressure transducer is greater than five times the pressure in the linear performance region.

[0088] Item 6. A control valve is disposed upstream of the first cavity, and the mass flow meter is mainly used to calculate the compressible laminar flow, m = K × (P 2 -P2 2 3. The mass flow meter of claim 2, wherein a drive signal for the control valve is used to position the control valve using an equation or table based on

[0089] Item 7. The mass flow meter according to item 2, wherein a control valve is disposed upstream of the first cavity, and the mass flow meter uses an equation based primarily on m=K×P1 to calculate sonic flow, and a drive signal for the control valve is used to position the control valve.

[0090] Item 8. The mass flow meter according to item 2, wherein a control valve is disposed downstream of the second cavity, and the mass flow meter uses an equation based primarily on m=K×(P1-P2) / (P1=P2) / 2) to calculate laminar flow, and a drive signal for the control valve is used to position the control valve.

[0091] Item 9. The mass flow meter of item 1, wherein the pressure transducer is an absolute pressure sensor, and the mass flow meter further comprises a differential pressure sensor, the differential pressure sensor including at least one diaphragm, the differential pressure sensor measuring linear and nonlinear responses to a difference between a second pressure and a third pressure on each side of the at least one diaphragm, and determining a voltage signal indicative of the pressure difference.

[0092] Item 10. The mass flow meter of item 1, wherein the pressure transducer comprises a first differential pressure sensor and a second absolute pressure sensor, the first differential pressure sensor and the second absolute pressure sensor measuring linear and non-linear responses of one or more diaphragms and determining a voltage signal indicative of the first pressure.

[0093] Item 11. The mass flow meter of item 1, wherein the pressure transducer is a first pressure sensor and the mass flow meter further comprises a second absolute pressure sensor, each of the plurality of absolute pressure sensors including at least one diaphragm, each absolute pressure sensor measuring linear and nonlinear responses of the respective at least one diaphragm to the pressure and the second pressure, respectively, and determining voltage signals indicative of the pressure and the second pressure.

[0094] Item 12. The mass flow meter according to item 1, wherein the deflection of the diaphragm at the maximum rated operating pressure of the pressure transducer is greater than 50% of the thickness of the diaphragm.

[0095] Item 13. The mass flow meter according to item 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] Item 14. The mass flow meter according to item 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.

[0097] Item 15. The mass flow meter of item 1, wherein the mass flow meter is configured to measure pressure in a nonlinear region of the pressure transducer, and the nonlinear performance is three times that of a 1% best fit linear model.

[0098] Item 16. The mass flow meter of item 1, wherein the mass flow meter is configured to measure pressure in a nonlinear region of the pressure transducer, and the nonlinear performance is 8 times that of a 1% best fit linear model.

Claims

1. A mass flow meter, a flow path through the mass flow meter, the flow path including a first cavity and a second cavity; a laminar flow element adjacent to the first cavity and the second cavity, the first cavity being upstream of the laminar flow element and the second cavity being downstream of the laminar flow element; a pressure transducer disposed within at least one of the first cavity or the second cavity, the pressure transducer including at least one diaphragm, the pressure transducer measuring linear and non-linear responses of the at least one diaphragm to a first pressure to determine a voltage signal indicative of pressure; Equipped with 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. Mass flow meter.

2. The mass flow meter is in communication with a controller, the controller comprising: receiving a set point signal indicative of a desired flow rate through the laminar flow element; controlling a valve drive signal such that the signal indicative of mass flow through the laminar flow element substantially corresponds to the received set point signal.

2. The mass flow meter of claim 1, operable as follows:

3. 2. The mass flow meter of claim 1, wherein the diaphragm has a rated pressure range of 0 psi to 50 psi.

4. 2. The mass flow meter of claim 1, wherein the diaphragm has a pressure rating in a linear performance region less than 5 psi and a pressure rating in a predominantly non-linear performance region greater than 5 psi.

5. 2. The mass flow meter of claim 1, wherein the rated pressure of the pressure transducer in its non-linear performance region is greater than 20 times the rated pressure in its linear performance region.

6. A control valve is disposed upstream of the first cavity, and the mass flow meter is mainly used to calculate the compressible laminar flow, m=K×(P ２ -P2 ２ 3. The mass flow meter of claim 2, wherein a drive signal for the control valve is used to position the control valve using an equation based on

7. 3. The mass flow meter of claim 2, wherein a control valve is disposed upstream of the first cavity, and the mass flow meter uses an equation based primarily on m=K×P1 to calculate sonic flow, and a drive signal for the control valve is used to position the control valve.

8. 3. The mass flow meter of claim 2, wherein a control valve is disposed downstream of the second cavity, and the mass flow meter uses an equation based primarily on m=K×(P1−P2) / (P1=P2) / 2) to calculate laminar flow, and a drive signal for the control valve is used to position the control valve.

9. 2. The mass flow meter of claim 1, wherein the pressure transducer is an absolute pressure sensor, and wherein the mass flow meter further comprises a differential pressure sensor, the differential pressure sensor including at least one diaphragm, the differential pressure sensor measuring linear and non-linear responses to a difference between a second pressure and a third pressure on each side of the at least one diaphragm to determine a voltage signal indicative of the pressure differential.

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

11. 2. The mass flow meter of claim 1, wherein the pressure transducer is a first pressure sensor and the mass flow meter further comprises a second absolute pressure sensor, each of the plurality of absolute pressure sensors including at least one diaphragm, each absolute pressure sensor measuring linear and non-linear responses, respectively, of a respective at least one diaphragm to the pressure and the second pressure to determine voltage signals indicative of the pressure and the second pressure.

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

13. 2. 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. 2. 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 200% of the thickness of the diaphragm.

15. 10. 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 and has a non-linear performance that is three times that of a 1% best fit linear model.

16. 10. The mass flow meter of claim 1, wherein the mass flow meter is configured to measure pressure in a nonlinear region of the pressure transducer and has a nonlinear performance that is 8 times that of a 1% best fit linear model.

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