Fluid Sensing Devices and Mass Flow Controllers

Abstract

A fluid sensing device and a mass flow controller comprising a fluid flow channel. The fluid flow channel has a flow restriction, a first fluid port at a first position upstream of the flow restriction, a second fluid port at a second position downstream of the flow restriction, a fluid sensor in fluid communication with the first fluid port and the second fluid port, and a laminar flow element. The laminar flow element comprises a flow stabilizing bar extending along the fluid flow channel at least from the first position to the second position to define a fluid sensing portion of the fluid flow channel between an outer wall of the fluid flow channel and an outer surface of the flow stabilizing bar. The flow restriction comprises reducing the hydraulic diameter of the fluid sensing portion of the fluid flow channel, which is achieved by reducing the diameter of the fluid flow channel or increasing the diameter of the flow stabilizing bar or both reducing the diameter of the fluid flow channel and increasing the diameter of the flow stabilizing bar. A mass flow controller comprising such a fluid sensing device is also provided.

Description

Technical Field

[0001] The present invention relates to a fluid sensing device, and more particularly to a fluid sensing device used with a fluid control valve, for example in a mass flow controller or a mass flow meter. Background Art

[0002] Fluid control valves are widely used to control the flow of fluids. The controlled fluid may include a gas, a liquid, or a combination thereof. In some cases, the fluid may also contain suspended particles. Although fluid control valves vary greatly in the specific configuration used to open and close a fluid communication path through a valve (usually a proportional valve), one particular type of valve actuation is performed using a solenoid. In a solenoid actuated valve, an electric current passes through an electromagnetic coil, wherein the coil is usually formed around a magnetic core. The coil generally includes a wire wound around a bobbin many times to form a plurality of so-called turns. The energized solenoid generates a magnetic field. The magnetic field strength is proportional to the number of turns and the current provided to the wire. As is well known in the art, in order to increase the magnetic field provided by the solenoid, the number of turns can be increased and / or the current provided to the wire can be increased. The magnetic field is usually operated on a movable armature connected to a plunger, which is configured to engage with a valve seat (which surrounds an inlet and / or outlet through which a fluid can pass), thereby changing the flow restriction generated by the valve seat and the sealing portion of the plunger. Other types of actuation such as piezoelectric actuation can be used.

[0003] Mass flow controllers ("MFCs") are widely used to measure and control fluid flow. A typical MFC includes a fluid sensing device, a fluid control valve, and a controller for controlling the fluid control valve. The fluid sensing device generally includes a flow channel extending between an inlet and an outlet, and a fluid sensor in communication with the flow channel. During operation of the MFC, the controller determines the flow rate through the flow channel based on a sensor signal from the fluid sensor, and operates the control valve accordingly to maintain the desired flow. There are two main types of MFCs: thermal-based, and pressure-based.

[0004] The operating principle of a thermal MFC is that the mass flow rate of a fluid flowing in a flow channel can be determined based on the rate of heat transfer from the walls of the flow channel to the fluid and based on the specific heat of the fluid. A thermal MFC typically comprises a heating element wrapped around a thin wall tube through which a laminar fluid flow is established and maintained. As long as laminar flow is maintained, the mass flow rate of the fluid can be determined based on the change in resistance of the heating element in response to the change in fluid temperature as the fluid flows through the tube. Other types of thermal MFCs are particularly suitable for use with calorimetric flow sensors or calorimetric micro flow sensors.

[0005] Pressure-based MFCs use flow restrictions such as nozzles or orifices along the flow path to create a pressure drop from which the flow rate can be determined. In such MFCs, the flow rate can be determined by physically measuring the bypass flow formed by the pressure difference, or by mathematically calculating the flow rate based on the principle that the fluid flow rate through the flow restriction varies with the pressure drop across the flow restriction. By sensing the fluid pressure p1 upstream of the flow restriction and the fluid pressure p2 downstream of the flow restriction, the pressure drop can be calculated and the flow rate determined.

[0006] In other types of MFCs, the principles of thermal-based and pressure-based MFCs may be combined, for example by measuring heat transfer from and / or to a fluid flowing along a bypass passage that bypasses a restriction in a main flow passage.

[0007] In both types of MFCs, the accuracy of fluid control achieved by the device depends on the accuracy of the sensor signal from the fluid sensing member. This can be compromised by turbulence in the flow path, which can cause fluctuations in fluid flow and pressure and can make accurate sensing difficult. This can be particularly problematic for devices that use simple orifice-type flow restrictions to create a pressure differential. Due to turbulence, noise and variability in the sensed pressure across the flow restriction can make it difficult to process the output signal of the sensed pressure or measured flow rate.

[0008] In order to solve this problem, it is known to place laminar flow elements in the flow channel of flow sensing devices to filter the fluid flow and thereby reduce turbulence. Such laminar flow elements are often more complex and expensive components of multiple parts downstream of the flow restriction portion through which the fluid is guided in the flow channel. Although these devices may be effective in reducing the turbulence in the flow channel, they may also lead to an increase in manufacturing costs and complexity, and may not be suitable for application in, for example, a fluid sensing device for a micro MFC.

[0009] The present invention seeks to provide an improved flow sensing apparatus which overcomes or alleviates one or more problems associated with the prior art. Summary of the invention

[0010] According to a first aspect of the present invention, there is provided a fluid sensing device, comprising: a fluid flow channel having an inlet and an outlet; a flow restriction portion located between the inlet and the outlet; a first fluid port located at a first position upstream of the flow restriction portion; a second fluid port located at a second position downstream of the flow restriction portion; a fluid sensor in fluid communication with the first fluid port and the second fluid port; and a laminar flow element comprising a flow stabilizing bar extending along the fluid flow channel at least from a first position to a second position to define a fluid sensing portion of the fluid flow channel between an outer wall of the fluid flow channel and an outer surface of the flow stabilizing bar, wherein the flow restriction portion comprises reducing a hydraulic diameter of the fluid sensing portion of the fluid flow channel. The reduction in the hydraulic diameter of the fluid sensing portion of the fluid flow channel is achieved by reducing the diameter of the fluid flow channel, or by increasing the diameter of the flow stabilizing bar, or by both reducing the diameter of the fluid flow channel and increasing the diameter of the flow stabilizing bar.

[0011] It has been found that this arrangement provides a simple and extremely effective way to reduce turbulence in the flow channel and promote laminar flow upstream and downstream of the flow restriction to improve the accuracy of flow measurement. Without wishing to be bound by theory, it is believed that the presence of the stabilizer bar increases the wetted perimeter of the flow channel and the viscous forces on the fluid, thereby reducing the Reynolds number of the fluid flow passing along the flow channel. By positioning the stabilizer bar so that it extends from at least a first position to a second position along the fluid flow channel, laminar flow at these two positions can be promoted, thereby reducing the changes and noise in the fluid flow characteristics at these positions. Since the fluid sensor is in fluid communication with the first fluid port and the second fluid port at these two positions, this can improve the accuracy of the flow characteristics sensed by the fluid sensor member. This is different from some prior art examples, in which the laminar flow element is downstream of the first position and therefore may not improve the flow stability at the first position.

[0012] The fluid sensing device of the present invention can be easily used in any number of different applications, such as controlling industrial processes, conducting laboratory experiments, or for safety reasons. For example, in an apparatus for mass flow control or volume flow control, the fluid sensing device can be used only for flow rate information, or as a component of flow regulation. The fluid sensing device of the present invention is particularly useful in accurate fluid sensing for flow control, such as in a mass flow controller. The fluid sensing device of the present invention can be configured for use with gases or liquids.

[0013] Flow restriction may be achieved by a change in diameter of only one of the fluid flow channel and the flow stabilizing bar. In this arrangement, the flow restriction is defined by only one of the fluid flow channel and the flow stabilizing bar, while the diameter of the other remains substantially constant along the fluid sensing portion. In this arrangement, the flow characteristics through the flow restriction portion are independent of the longitudinal position of the laminar flow element within the flow channel. This may advantageously be comparable to an arrangement in which the flow restriction is defined by a change in diameter of both the fluid flow channel and the flow stabilizing member, wherein the hydraulic diameter of the fluid sensing portion may be extremely sensitive to inaccuracies or changes in the longitudinal position of the laminar flow element within the flow channel, as this will change the relative position of the diameter change.

[0014] In certain embodiments, the flow restriction comprises a reduction in diameter of an outer wall of the fluid flow channel. The reduction may comprise a step change in the diameter of the outer wall. The reduction may comprise a gradual change in the diameter of the outer wall. The reduction may be provided only around a portion of the periphery of the fluid flow channel. The reduction may be uniform around the periphery of the fluid flow channel. Preferably, the reduction comprises a tapering of the outer wall extending around the entire periphery of the flow channel.

[0015] The diameter of the outer surface of the flow stabilizing bar may be substantially constant along substantially the entire length of the fluid sensing portion. In such embodiments, the hydraulic diameter of the fluid sensing portion of the fluid flow channel decreases across the flow restriction portion, varying only with the decrease in the diameter of the outer wall of the flow channel. In this arrangement, the flow characteristics through the flow restriction portion are independent of the longitudinal position of the laminar flow element within the flow channel. This can be advantageously comparable to an arrangement in which the diameter of the outer surface of the flow stabilizing bar varies along the length of the flow stabilizing bar, wherein the hydraulic diameter of the fluid sensing portion of the flow channel may be extremely sensitive to inaccuracies or changes in the longitudinal position of the laminar flow element within the flow channel, because this will change the radial distance between the outer surface of the flow stabilizing bar and the outer wall of the flow channel, and thereby change the hydraulic diameter of the fluid sensing portion at a given position along the fluid flow channel.

[0016] Alternatively, the diameter of the outer surface of the flow stabilizing bar may change along the length of the flow stabilizing bar. The diameter of the outer surface may increase along the length of the flow stabilizing bar. The diameter of the outer surface may decrease along the length of the flow stabilizing bar. In the case where the diameter of the outer surface of the flow stabilizing bar increases along the length of the flow stabilizing bar, in the area of ​​the restricted portion, the diameter of the outer wall of the flow channel may decrease, remain unchanged, or increase, provided that the increase in the diameter of the outer surface of the flow stabilizing bar is sufficient to still reduce the radial distance between the outer wall of the fluid flow channel and the outer surface of the flow stabilizing bar across the restricted portion. In the case where the diameter of the outer surface of the flow stabilizing bar decreases along the length of the flow stabilizing bar, the diameter of the outer wall of the flow channel should also decrease so that the radial distance between the outer wall of the fluid flow channel and the outer surface of the flow stabilizing bar across the restricted portion is reduced.

[0017] The flow restriction may include increasing the diameter of the flow stabilizing bar. The increase may include a step change in diameter. The increase may include a gradual change in diameter. The increase may be provided only around a portion of the periphery of the flow stabilizing bar. The increase may be uniform around the periphery of the flow stabilizing bar. Preferably, the increase includes a tapering of the flow stabilizing bar extending around the entire periphery of the flow stabilizing bar. In such embodiments, the diameter of the flow channel may be constant in the region of the flow restriction, so that the flow restriction is limited only by the increase in the diameter of the flow stabilizing bar. The benefit of this may be that it allows the pressure drop across the flow restriction to be changed as required for a given throughput simply by changing the laminar flow element.

[0018] Preferably, the outer surface of the flow stabilizing bar is substantially continuous. That is, the outer surface of the flow stabilizing bar is substantially free of any grooves, protrusions or other surface features that might otherwise prevent flow continuation.

[0019] The flow stabilizing rod may be solid. In such an example, the fluid flowing along the flow channel must flow along the fluid sensing portion.

[0020] In some embodiments, the flow stabilizing bar includes one or more internal flow passages that define an additional flow portion of the fluid flow channel that is separated from the fluid sensing portion. In this arrangement, the fluid can flow along the flow channel through both the fluid sensing portion and the additional flow portion. This can increase the flow rate through the fluid sensing device relative to the arrangement where the flow stabilizing bar is solid. This can be beneficial in the case where the required flow rate is higher than the flow rate supported by the fluid sensing portion alone, without inducing turbulence in the fluid sensing portion.

[0021] Preferably, the flow stabilizing bar extends along the fluid flow passage from a position upstream of the first position to a position downstream of the second position. Alternatively, the flow stabilizing bar may extend along the fluid flow passage from a position upstream of the first position to a position adjacent to the second position. As another alternative, the flow stabilizing bar may extend along the fluid flow passage from a position adjacent to the first position to a position downstream of the second position.

[0022] Preferably, the laminar flow element further comprises a support member, through which the stabilizing bar is mounted in the fluid flow channel. The support member may define at least one fluid flow hole communicated with the fluid sensing portion of the fluid flow channel. The support member may be fixed at a position upstream of the first position in the fluid flow channel. The support member may be fixed at a position downstream of the second position in the fluid flow channel. The support member may be attached at the upstream end of the flow stabilizing bar. The support member may be attached at the downstream end of the flow stabilizing bar, or at a position between the upstream end and the downstream end of the flow stabilizing bar. Preferably, the support member is fixed at a position downstream of the second position in the fluid flow channel and is attached at the upstream end of the flow stabilizing bar.

[0023] The support member can be fixed in the flow channel by any suitable means. Preferably, the support member is fixed in the flow channel in a removable manner. That is, the support member can be removed from the flow channel without damaging the laminar flow element or the fluid flow channel. The support member can be fixed in the flow channel by a threaded connection. In such embodiments, the support member includes a thread that engages with a corresponding thread on the outer wall of the fluid flow channel. The support member can be fixed in the fluid flow channel by an interference fit. The support member can be fixed in the fluid flow channel between the bearing surface of the fluid flow channel and the fixture. The bearing surface can be provided by an annular shoulder on the outer wall of the fluid flow channel. The fixture can be a removable fixture, such as a threaded washer. The fixture can be fixed in the fluid flow channel by an interference fit or by a snap fit in a recess in the outer wall of the fluid flow channel.

[0024] The at least one fluid flow aperture may comprise a single aperture.

[0025] The at least one fluid flow hole may include a plurality of fluid flow holes. The plurality of fluid flow holes may be spaced at certain intervals around the periphery of the support. The fluid flow holes may be unevenly spaced around the periphery of the support. The plurality of fluid flow holes may be spaced at regular intervals around the periphery of the support. The plurality of fluid flow holes may be arranged around the outer periphery of the support. Preferably, the plurality of fluid flow holes are arranged at a position between the outer surface of the support and the stabilizer bar. For example, in an intermediate position between the outer surface of the support and the outer surface of the stabilizer bar. In the case where the flow stabilizer bar includes one or more internal flow channels, the plurality of fluid flow holes include at least one fluid flow hole that is fluidly connected to the one or more internal flow channels through the flow stabilizer bar.

[0026] The support member may have any suitable shape. Preferably, the support member has an outer surface that corresponds or conforms in shape to the shape of the outer wall of the fluid flow channel. The outer surface may correspond or conform in shape to the shape of the outer wall of the fluid flow channel so that during use, fluid flowing along the fluid flow channel does not substantially flow between the outer surface of the support member and the outer wall of the fluid flow channel. This may help to produce a uniform fluid flow through the support member. The support member may include one or more flexible seals on its outer surface, the outer surface conforming to the shape of the outer wall of the fluid flow channel through the flexible seal.

[0027] The fluid sensor may include a heater and one or more temperature sensors.

[0028] The fluid sensor may be a pressure sensor. The fluid sensor may be configured to sense a first fluid pressure at a first position and to sense a second pressure in a second position. The fluid sensor may be configured to sense a first fluid pressure at a first position through a first fluid port and to sense a second pressure in a second position through a second fluid port. The fluid sensor may include a first sensor portion positioned in the first fluid port and configured to sense a first fluid pressure at a first position. The fluid sensor may include a second sensor portion positioned in the second pressure port and configured to sense a second fluid pressure at a second position. A first sensor seal may be provided around the first sensor portion to form a seal between an outer surface of the first sensor portion and an inner surface of the first pressure port. A second seal may be provided around the second sensor portion to form a seal between an outer surface of the second sensor portion and an inner surface of the second pressure port. In this way, the fluid in the first and / or second sensor portions is prevented from bypassing the first and / or second sensor portions. The fluid in the first and second pressure ports may enter the housing of the fluid sensor through the first and second sensor portions.

[0029] The fluid sensor may be configured to output a sensor signal comprising a first fluid pressure signal and a second fluid pressure signal. The fluid sensor may be configured to calculate a pressure difference between the first fluid pressure and the second fluid pressure. The fluid sensor may be configured to output a sensor signal comprising a pressure difference signal comprising a plurality of calculated pressure difference values. The fluid sensor may be configured to calculate a flow rate through a fluid flow channel based on the sensed first and second fluid pressure values. The fluid sensor may be configured to output a sensor signal comprising a flow rate signal comprising a plurality of calculated flow rate values.

[0030] The fluid sensor may be a mass flow sensor. The fluid sensing device may include a bypass channel configured to split the flow around the flow restriction portion. The fluid sensor may be a mass flow sensor configured to measure a bypass flow rate through the bypass channel. The first fluid port and the second fluid port may be connected to form part of the bypass channel.

[0031] The fluid sensor may include a single sensing head. The signal from the sensing head may be amplified by different gains. This may increase the effective flow rate measurement range that the fluid sensing device can accurately measure, and may facilitate accurate flow rate readings from the fluid sensor even at very low flow rates. The fluid sensor may include multiple sensing heads within a single sensor. The signal from each sensing head may be amplified by different gains. This may increase the effective flow rate measurement range that the fluid sensing device can accurately measure, and may facilitate accurate flow rate readings from the fluid sensor even at very low flow rates. The fluid sensing device may include multiple sensors. The multiple sensors may each be in fluid communication with the fluid sensing portion through a first and second fluid port. Alternatively, the fluid sensing device may include a first fluid sensor in fluid communication with the first fluid sensing portion through a first and second port, and other fluid sensors in fluid communication with other fluid sensing portions through other fluid ports at other locations in the fluid flow channel.

[0032] In certain embodiments, the fluid sensing device further comprises another fluid sensor, wherein the fluid sensing portion comprises a first fluid sensing portion extending from a first position to a second position and a second fluid sensing portion extending from a third fluid port at a third position of a fluid flow channel upstream of the flow restriction portion to a fourth fluid port at a fourth position of a fluid flow channel downstream of the flow restriction portion, wherein the fluid sensor is in fluid communication with the first fluid sensing portion through the first and second fluid ports, and wherein the other fluid sensor is in fluid communication with the second fluid sensing portion through the third and fourth fluid ports. The first and second fluid sensing portions may be located at the same circumferential position around the flow stabilizing bar. Preferably, the first and second fluid sensing portions are at different circumferential positions around the flow stabilizing bar. The fluid sensing device may further comprise a third, fourth, fifth, sixth or more fluid sensing portions at different circumferential positions around the flow stabilizing bar. These additional fluid sensing portions may each be in fluid communication with different fluid sensors.

[0033] The fluid sensing portion may include a first fluid sensing portion defined between a first surface portion of the flow stabilizing bar and an outer wall of the flow channel and a second fluid sensing portion between a second surface portion of the flow stabilizing bar and an outer wall of the flow channel. The first and second surface portions may be located at the same circumferential position around the flow stabilizing bar. Preferably, the first and second surface portions are at different circumferential positions around the flow stabilizing bar. The first and second surface portions may be diametrically opposed.

[0034] The flow stabilizing bar may be centrally located within the fluid flow channel. Alternatively, the flow stabilizing bar may be offset from the central axis of the fluid flow channel. In this arrangement, the percentage change in the hydraulic diameter across the flow-restricting portion is different for different areas around the periphery of the flow stabilizing bar. In certain embodiments, the first and second fluid sensing portions are at different circumferential positions around the flow stabilizing bar, and the flow stabilizing bar is offset from the central axis of the fluid flow channel. In this arrangement, the ratio between the hydraulic diameters upstream and downstream of the flow-restricting portion is different for the first and second fluid sensing portions. This means that for the first fluid sensing portion, the pressure drop across the flow-restricting portion will be different from the pressure drop of the second fluid sensing portion. This can increase the effective flow rate measurement range that the fluid sensing device can accurately measure and can facilitate accurate flow rate readings from the fluid sensor even at extremely low flow rates.

[0035] The flow stabilizing bar may be offset from the central axis of the fluid flow channel so that the first surface portion of the flow stabilizing bar is closer to the outer wall of the flow channel than the second surface portion of the flow stabilizing bar. In this arrangement, for the first fluid sensing portion, the percentage change in hydraulic diameter across the restricted portion will be different from the percentage change in hydraulic diameter across the second fluid sensing portion. Therefore, for the first fluid sensing portion, the pressure drop across the restricted portion will be higher than the second fluid sensing portion. In other examples, the flow stabilizing bar may be offset from the central axis of the fluid flow channel so that the first surface portion of the flow stabilizing bar is farther away from the outer wall of the flow channel than the second surface portion of the flow stabilizing bar.

[0036] In the case where the flow stabilizing rod is offset from the central axis of the fluid flow channel, the pressure drop across the flow restriction portion can be higher for one of the first fluid sensing portion and the second fluid sensing portion than for the other. This can increase the effective flow rate measurement range that the fluid sensing device can accurately measure and facilitate accurate flow rate readings from the fluid sensor even at extremely small flow rates.

[0037] The fluid sensing device may be used in any suitable assembly.For example, the fluid sensing device may form part of a fluid manifold.

[0038] According to a second aspect of the invention there is provided a mass flow controller comprising a fluid control valve, control electronics and a fluid sensing device according to the first aspect, wherein the control electronics is configured to control the fluid control valve based on a sensor signal provided by the fluid sensing device.

[0039] The fluid control valve may be a proportional valve.

[0040] The mass flow controller may be a micro mass flow controller. As used herein, the term "micro mass flow controller" refers to a mass flow controller having a housing having a maximum dimension of less than 100 mm, preferably less than 80 mm in any direction. The micro flow controller may have a maximum length of less than 80 mm and a maximum height of less than 50 mm.

[0041] Within the scope of the present application, it is expressly intended that the various aspects, embodiments, examples and alternatives set forth in the preceding paragraphs, in the claims and / or in the following description and drawings, in particular individual features thereof, may be considered independently or in any combination. That is, all embodiments and / or features of any embodiment may be combined in any manner and / or combination, unless such features are incompatible. The applicant has the right to change any initially filed claim or to file any new claim accordingly, including the right to amend any initially filed claim that is attached to any other claim and / or incorporates any features of any other claim, although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Other features and advantages of the present invention will be further described, by way of example only, with reference to the accompanying drawings, in which:

[0043] Figure 1 is a perspective, partially cross-sectional view of a mass flow controller incorporating a fluid sensing device according to a first embodiment;

[0044] Figure 2 yes Figure 1 A top view of a mass flow controller;

[0045] Figure 3 It runs through Figure 2 A cross-sectional view taken along line III-III in FIG.

[0046] Figure 4 It runs through Figure 2 A cross-sectional view taken along line IV-IV in FIG.

[0047] Figure 5 yes Figures 1 to 4 A top perspective view of a solid body of a mass flow controller;

[0048] Figure 6 yes Figure 1 A perspective view of a laminar flow element of a fluid sensing device shown in FIG.

[0049] Figure 7 yes Figure 6 An upstream end view of a laminar flow element;

[0050] Figure 8 yes Figure 6 and Figure 7A cross-sectional view of a laminar flow element;

[0051] Fig. 9 yes Figures 1 to 4 a schematic cross-section of a fluid sensing device of a mass flow controller showing fluid flow through the device;

[0052] Fig.10 is a perspective, partially cross-sectional view of a mass flow controller incorporating a fluid sensing device according to a second embodiment;

[0053] Fig.11 is a schematic cross-sectional view of a fluid sensing device of a third embodiment;

[0054] Fig.12 is a partial cross-sectional view of a portion of a fluid sensing device of a fourth embodiment;

[0055] Fig.13 is Fig.12 An end view taken in the direction of arrow XIII in FIG. 1 ; and

[0056] Fig.14 A cross-sectional view of a portion of a fifth embodiment of a fluid sensing device is shown. DETAILED DESCRIPTION

[0057] Figures 1 to 9 A first mass flow controller 100 including a fluid sensing device 120 according to a first embodiment of the present invention is shown. The mass flow controller 100 includes a housing 101 having a fluid inlet 102 and a fluid outlet 103. The housing 101 contains a fluid control valve 104, such as a proportional valve, and control electronics 105 mounted on a main PCB 106. In this example, the housing 101 includes a solid body 107 and a cover 108 removably secured to the solid body 107 by a screw 109. The fluid control valve 104 is positioned along a fluid flow path extending between the fluid inlet 102 and the fluid outlet 103, and is configured to adjust the flow rate through the mass flow controller 100 based on a control signal from the control electronics 105 so as to achieve or maintain a desired flow rate. Figure 1 As shown, the fluid inlet 102 and the fluid outlet 103 may be threaded to allow for easy coupling to a threaded connector.

[0058] The fluid sensing device 120 includes a fluid flow channel 121, which is surrounded and defined by an outer wall 122 of the channel 121 and forms part of a fluid flow path through the mass flow controller 100. The fluid flow channel 121 extends from a channel inlet 123 (which is in fluid communication with the fluid inlet 102 of the mass flow controller 100) to a channel outlet 124 (which is in fluid communication with the fluid outlet 103 of the mass flow controller 100 through the fluid control valve 104). In this example, the fluid flow channel 121 is circular in cross-section, but other cross-sectional shapes may also be suitable. The fluid sensing device also includes a flow restriction 125 at a position along the length of the fluid flow channel 121, which is configured to generate a pressure difference in the fluid flowing along the channel 121. In this example, the flow restriction 125 includes a gradually decreasing diameter of the outer wall 122 of the fluid flow channel 121, so that the cross-sectional area of ​​the fluid flow channel 121 is reduced in this area, and the flow rate of the fluid when passing through the flow restriction 125 is increased. This will produce a pressure drop across the flow restriction 125. In other examples, the flow restriction may include a step change in outer wall diameter and / or a change in diameter of an outer surface of a laminar flow element positioned in the flow channel 121 , as described below.

[0059] The fluid sensing device 100 also includes a fluid sensor 130 mounted on an auxiliary printed circuit board 140. The main PCB 106 is spaced apart from the auxiliary printed circuit board 140 in a direction perpendicular to the plane of the auxiliary printed circuit board 140 and is electrically connected to the auxiliary printed circuit board 140 via an electrical connector 141. The main printed circuit board 106 is removably mounted to the solid body 107 via the same screws 109 as the cover 108. The main printed circuit board 106 can be considered a "main" PCB because it supports the control electronics 105 of the mass flow controller 100. The auxiliary printed circuit board 140 on which the fluid sensor 130 is mounted can be considered an "auxiliary" PCB. In other examples, such as those described below with respect to Fig.10

[0046] As discussed in the embodiments, the mass flow controller may include a single PCB upon which both the control electronics 105 and the fluid sensor 130 are mounted directly.

[0060] As best in Fig. 9As seen in FIG. 1 , the fluid sensor 130 is in fluid communication with a first location 131 of the fluid flow channel 121 upstream of the restricted portion 125 via a first fluid port 132, and is in fluid communication with a second location 133 of the fluid flow channel 121 downstream of the restricted portion 125 via a second fluid port 134. However, in other examples, the fluid sensor may be in fluid communication with only a single location of the fluid flow channel. The fluid sensor 130 is configured to generate a sensor signal indicative of a flow rate of a fluid passing along the fluid flow channel 121, so that the control electronics 105 can control the fluid control valve 104 accordingly to achieve a desired flow rate through the mass flow controller 100.

[0061] In this example, the fluid sensor 130 is a pressure sensor and includes a first sensor portion 135 positioned in the first fluid port 132 and a second sensor portion 136 positioned in the second fluid port 134. The first sensor portion 135 and the second sensor portion 136 each provide an opening through which a fluid can enter and / or leave a housing 137 of the fluid sensor 130. The first sensor portion 135 enables the fluid sensor 130 to sense or measure a first fluid pressure P1 at a first location 131, while the second sensor portion 136 enables the fluid sensor 130 to sense or measure a second fluid pressure P2 at a second location 133. The first sensor portion 135 and the second sensor portion 136 extend into the first fluid port 132 and the second fluid port 134, respectively. An O-ring 138 is provided around each of the first sensor portion 135 and the second sensor portion 136 to form an elastic seal between the first sensor portion 135 and the first fluid port 132 and between the second sensor portion 136 and the second fluid port 134, respectively, to prevent fluid leakage.

[0062] Due to the flow restriction 125, the flow rate at the second position 133 tends to be higher than the flow rate at the first position. Therefore, the second fluid pressure P2 tends to be lower than the first fluid pressure P1. Based on the sensed values ​​of P1 and P2, the pressure difference AP across the flow restriction 125 can be calculated, and the flow rate through the fluid flow channel 121 is determined based on the principle that the fluid flow rate through the flow restriction is proportional to the pressure difference across the flow restriction. The pressure difference AP can be determined by the fluid sensor 130 or by the control electronics 105. In the case where the pressure difference AP is determined by the control electronics, the sensor signal may include a first pressure signal of the first fluid pressure P1 over time and a second pressure signal of the second fluid pressure P2 over time. In the case where the pressure difference AP is determined by the fluid sensor, the sensor signal may include a pressure difference signal of the pressure difference AP over time. The fluid sensor may be configured to determine the flow rate, in which case the sensor signal may include a flow rate signal.

[0063] In other examples, the fluid sensor 130 may be a mass flow sensor. For example, the first fluid port 132 and the second fluid port 134 may be connected to form a bypass channel (not shown), a portion of the fluid flow around the bypass channel is diverted by the flow restriction portion 125, wherein the fluid sensor is configured to measure the bypass flow rate around the bypass channel. Then, the fluid flow rate along the fluid flow channel may be calculated based on the bypass flow rate.

[0064] As best in Figures 3 to 5 As seen in the solid body 107, the solid body 107 is formed of a block of solid material in which a plurality of holes are defined to form various ports or conduits and thereby accommodate other components of the mass flow controller 100. The fluid sensing device 120 also includes an optional pressure compensation chamber 142 in fluid communication with another location 143 along the fluid flow channel 121 through a pressure compensation port 144. The pressure compensation chamber 142 is defined by a container in the form of a cavity 145 in the outer surface of the solid body 107 and by an auxiliary printed circuit board 140 that closes the cavity 145. The auxiliary printed circuit board 140 is held in place against the cavity 145 by a pair of screws 146 extending into threaded holes 1071 in the solid body 107. The auxiliary printed circuit board 140 is sealed against the cavity 145 by an elastomeric seal 147 that rests in a continuous groove 148 formed in the outer surface of the solid body 107 and extending around the cavity 145. The elastomeric seal 147 prevents fluid leakage between the auxiliary printed circuit board 140 and the solid body 107. In this way, the auxiliary printed circuit board 140 forms the upper wall of the pressure compensation chamber 142. Therefore, the lower side of the auxiliary printed circuit board 140 on which the fluid sensor 130 is mounted is exposed to the high pressure in the pressure compensation chamber 142, while the upper side of the auxiliary printed circuit board 140 is exposed to atmospheric pressure. This means that the auxiliary printed circuit board should be constructed to withstand the difference between atmospheric pressure and the high pressure in the pressure compensation chamber 142 during operation. However, this also means that the components of the mass flow controller located above the auxiliary printed circuit board 140 (such as the main printed circuit board 106) are at atmospheric pressure and do not have to be constructed to withstand high pressure. The first fluid port 132, the second fluid port 134 and the pressure compensation port 144 extend to the bottom of the cavity 145. The pressure compensation port is open to the pressure compensation chamber. The first and second fluid ports 132, 134 each have a cup 1321, 1341 at their cavity ends and a seal holder 1322, 1324 surrounding the cup 1321, 1341, wherein an O-ring surrounding each sensor portion is positioned to isolate the first and second fluid ports from the pressure compensation chamber.

[0065] In this example, the other location 143 (from which the pressure compensation port 144 extends) is downstream of both the first location 131 and the second location 133 from which the first fluid port 132 and the second fluid port 134 extend. However, in other examples, the pressure compensation port 144 may be connected to a different location along the fluid flow channel 121, such as a location upstream of one or both of the first location 131 and the second location 133.

[0066] In order to improve the flow sensing accuracy, the fluid sensing device 120 also includes a laminar flow element 150 located in the fluid flow channel 121. The laminar flow element 150 includes a stabilizing rod 151 and a support member 152, and the stabilizing rod 121 is centrally mounted in the fluid flow channel 121 by the support member. The stabilizing rod 151 extends along the fluid flow channel 121 through the flow restriction portion 125 at least from the first position 131 to the second position 133 to promote laminar flow and suppress turbulence in the fluid flow channel 121. In this example, the stabilizing rod 151 extends from a position upstream of the first position 131 to a position downstream of the second position 133. The support member 152 of the laminar flow element 150 is fixed in the fluid flow channel 121, at the upstream end of the stabilizing rod 151. The support member 152 can be fixed in the flow channel 121 in a fixed manner, or fixed in a removable manner. In this example, the support member 152 includes a thread 156 on its outer surface 154 that engages with a corresponding thread on the outer wall 122 of the flow channel 121. Thus, the support 152 is removably secured within the flow passage 121 by a threaded connection at a location upstream of the first location 131 .

[0067] As best in Figures 6 to 8 As seen in the figure, the support 152 of the laminar flow element 150 includes a plurality of fluid flow holes 155 spaced at regular intervals around the periphery of the support 152 and spaced from the outer surface 154 of the support. The fluid flow holes 155 allow fluid to pass through the support 152 and promote a more uniform fluid flow along the fluid flow channel 121. The support 152 may have any suitable shape. In this example, the outer surface 154 of the support 152 corresponds in shape to the outer wall 122 of the flow channel 121 and is fixed by a threaded connection. This prevents or reduces the amount of fluid that can pass between the outer surface 154 of the support 152 and the outer wall 122 of the flow channel 121. Since the outer surface 154 corresponds in shape to the outer wall 122 of the flow channel 121, substantially all of the fluid flowing along the fluid flow channel flows through the fluid flow holes 155. In other examples, one or more outer holes may be formed between the outer surface of the support and the outer wall of the flow channel so that the fluid can pass around the outer surface of the support.

[0068] As best in Fig. 9As seen in FIG. 1 , the outer wall 122 of the fluid flow channel 121 and the outer surface 153 of the stabilizer bar 151 together define an annular fluid sensing portion 126 of the fluid flow channel 121, through which the fluid flows along the flow channel. In this example, the stabilizer bar 151 is solid, and therefore all fluids flowing along the flow channel must flow along the fluid sensing portion 126. The outer surface 153 of the flow stabilizer bar 151 is substantially continuous. That is, the outer surface 153 of the flow stabilizer bar 151 is substantially free of any grooves, protrusions, or other surface features that may otherwise prevent flow continuation. The outer surface 153 of the flow stabilizer bar 151 may be smooth. In this example, the diameter of the outer surface 153 is substantially constant along the entire length of the stabilizer bar 151. Therefore, the cross-sectional area of ​​the fluid sensing portion 126, which changes with the radial distance between the outer wall 122 of the fluid flow channel 121 and the outer surface 153 of the flow stabilizer bar 151, decreases across the flow restriction portion, completely changing with the decrease in the diameter of the outer wall 122 of the flow channel 121. In other examples, the diameter of the outer surface 153 may change along the length of the stabilizer bar 151. The diameter of the outer surface 153 may increase or decrease along the length of the bar, provided that the radial distance between the outer wall 122 of the fluid flow channel 121 and the outer surface 153 of the flow stabilizer bar 151 is reduced to define the restricted portion. In examples where the diameter of the outer surface of the flow stabilizer bar increases, the diameter of the outer wall of the flow channel may decrease, remain the same, or increase in the area of ​​the restricted portion, provided that the increase in the diameter of the outer surface of the flow stabilizer bar is sufficient to still reduce the radial distance between the outer wall of the fluid flow channel and the outer surface of the flow stabilizer bar across the restricted portion.

[0069] During operation of the mass flow controller 100, fluid enters the housing 101 through the fluid inlet 102 and into the fluid flow channel 121 through the channel inlet 123. When the fluid reaches the laminar flow element 150, it passes through the plurality of fluid flow holes 155 in the support 152 and enters the annular fluid sensing portion 126 of the fluid flow channel 121 defined between the stabilizer bar 151 and the outer wall 122 of the fluid flow channel 121, wherein the fluid travels along the length of the stabilizer bar 151, passes through the flow restriction 125 and exits the fluid flow channel 121 at the channel outlet 124. From the fluid sensing portion 126, the fluid enters the housing 137 of the fluid sensor 130 through the first fluid port 132 and the second fluid port 134. The fluid sensor 130 monitors the first fluid pressure P1 at the first location 131 and the second fluid pressure P2 at the second location 133, and outputs the sensed values ​​of P1 and P2 as sensor signals to the control electronics 105. The control electronics 105 determines the pressure drop AP across the restricted portion 125 by subtracting P2 from P1. Based on the pressure drop AP, the control electronics 105 calculates the flow rate through the fluid flow channel 121 and compares this flow rate with the desired flow rate in a conventional manner. If the calculated flow rate is greater than or less than the desired flow rate, the control electronics 105 controls the fluid control valve 104 to adjust the flow rate as needed. Since the pressure compensation chamber 142 is in fluid communication with the fluid flow channel through the pressure compensation port 144, the pressure compensation chamber 142 is filled with fluid at the same pressure P3 as at another location 143 along the fluid flow channel 121. In this arrangement, the outer surface of the housing 137 of the fluid sensor 130 is exposed to high pressure that varies with the pressure P3 of the fluid flowing along the flow channel 121 at the other location 143. At the same time, the inner surface of the housing 137 is exposed to high pressure that varies with the pressures P1, P2 of the fluid flowing along the flow channel 121 at the first location 131 and the second location 133. This means that the housing of the fluid sensor only needs to resist a relatively small difference between the pressure P3 at another location and the first and second pressures P1 and P2 at the first and second locations, rather than the full difference between atmospheric pressure and the first and second fluid pressures P1 and P2.

[0070] By enclosing the housing 137 of the fluid sensor 130 within the pressure compensation chamber 142, the outer surface of the housing 137 is exposed to a fluid pressure that is comparable to the fluid pressure inside the housing 137. Therefore, the pressure differential across the housing 137 is small. This means that the housing 137 does not have to be constructed to withstand large internal pressures, because these internal pressures will be commensurate with the large external pressures. Therefore, the complexity, size and weight of the fluid sensor can be reduced relative to conventional fluid sensing devices. In fact, under the arrangement of the present invention, it is possible to use a fluid sensor with a housing that can withstand a pressure differential of only 1 bar or less.

[0071] Fig.10 A mass flow controller 200 of a second embodiment is shown, which includes a fluid sensing device 220 according to a second embodiment of the present invention. The mass flow controller 200 has a similar structure and function to the mass flow controller 100 of the first embodiment, and similar reference numerals are used to represent similar features. As with the first embodiment, the fluid sensing device 220 includes a laminar flow element 250 having a flow stabilizing rod 251, which is centrally positioned in the fluid flow channel 221 and extends from a position upstream of the first position 231 to a position downstream of the second position 233. The laminar flow element 250 is identical in structure and function to the laminar flow element 150 of the mass flow controller 100 of the first embodiment. The mass flow controller 200 also includes a control electronics 205 mounted on a PCB 206. However, unlike the first embodiment, the fluid sensor 230 is directly mounted on the main PCB 106 together with the control electronics 205. Therefore, the main PCB 106 is the only PCB in the mass flow controller 200. In the absence of an auxiliary printed circuit board, the main PCB 206 forms the upper wall of the pressure compensation chamber 242, is held in place by a pair of screws 209 extending into threaded holes in the solid body 207, and is sealed against the solid body 207 by an elastomeric seal (not shown). Therefore, the lower side of the main PCB 206 is exposed to the high pressure in the pressure compensation chamber 242, while the upper side of the main PCB 206 is exposed to atmospheric pressure. This means that the main PCB 206 should be constructed to withstand the difference between atmospheric pressure and the high pressure in the pressure compensation chamber 242 during operation.

[0072] Furthermore, in the mass flow controller 200 of the second embodiment, another position 243 from which the pressure compensation port 244 extends is upstream of both the first position 231 and the second position 233 rather than downstream.

[0073] Fig.11A schematic cross-sectional view of a fluid sensing device 320 of a third embodiment is shown. The fluid sensing device 320 includes a laminar flow element 350 having a flow stabilizing rod 351, which extends from a position upstream of a first position 331 to a position downstream of a second position 333 along a fluid flow channel 321. The laminar flow element 350 is similar to the laminar flow elements 150 and 250 of the fluid sensing devices of the first and second embodiments. However, the laminar flow element 350 of the third embodiment also includes an internal flow channel 357 extending along the length of the stabilizing rod 351. The internal flow channel 357 is fluidically connected to the channel inlet through a central hole 358 in a support member 352, thereby defining an additional flow portion of the fluid flow channel separated from the fluid sensing portion. In this arrangement, the fluid flows along the flow channel through both the fluid sensing portion and the additional flow portion defined by the internal flow channel 357. This arrangement, which is solid relative to the flow stabilizing rod, can increase the flow rate through the fluid sensing device. This can be beneficial in the case where the required flow rate is higher than the flow rate supported by the fluid sensing portion alone, and turbulence will not be induced in the fluid sensing portion.

[0074] Also like Fig.11 As shown in , the flow stabilizing rod 351 is not centrally mounted, but offset from the central axis of the flow channel so that the outer surface of the rod 351 is closer to the outer wall of the flow channel on one side than on the other side. In this way, the fluid sensing portion of the flow channel includes a first fluid sensing portion 326A between a first side of the flow stabilizing rod 351 and the outer wall of the flow channel and a second fluid sensing portion 326B between a second opposite side of the flow stabilizing rod and the outer wall of the flow channel. Fig.11, the first fluid sensing portion 326A is shown as the upper portion of the flow channel, and the second fluid sensing portion is shown as the lower portion of the flow channel. Since the hydraulic diameter of the first fluid sensing portion 326A is smaller than the hydraulic diameter of the second fluid sensing portion 326B, although the reduction in the flow channel diameter across the restricted portion 325 is the same, the percentage change in the hydraulic diameter across the restricted portion is greater for the first fluid sensing portion than for the second fluid sensing portion. This means that for the first fluid sensing portion 326A, the pressure drop across the restricted portion will be different from the pressure drop of the second fluid sensing portion 326B. To take advantage of this, the fluid sensing device 320 also includes an optional further fluid sensor 370, which is fluidically connected to a third position 371 upstream of the restricted portion 325 through a third fluid port 372 and is fluidically connected to a fourth position 373 downstream of the restricted portion 325 through a fourth fluid port 374. The further fluid sensor 370 is connected to the third and fourth fluid ports and operates in the same manner as discussed above with respect to the fluid sensor 130 of the fluid sensing device 120 of the first embodiment. In this example, the fluid sensor 330 is in fluid communication with the first fluid sensing portion 326A, and the further fluid sensor 370 is in fluid communication with the second fluid sensing portion 326B. This allows for a larger range of flow rates that can be accurately measured by the fluid sensing device 320, and facilitates accurate flow rate readings from the fluid sensor even at very low flow rates.

[0075] Fig.12 and Fig.13 A portion of a fluid sensing device 420 of a fourth embodiment is shown. The fluid sensing device 420 includes a laminar flow element 450 having a flow stabilizing rod extending along a fluid flow channel 421 from a position upstream of a first position 431 to a position downstream of a second position 433. The laminar flow element 450 is similar to the laminar flow element 350 of the fluid sensing device 320 of the third embodiment. However, unlike the laminar flow elements of the earlier embodiments, the stabilizing rod of the fourth laminar flow element 450 is not rotationally symmetrical, but has a first section 451A of constant cross-sectional thickness and a second section 451B that abuts against the wall of the flow channel and corresponds in shape to the wall of the flow channel. In addition, the support member 452 includes a fluid flow hole 455 in fluid communication with the fluid sensing portion 426 and a central hole 458 in fluid communication with the internal flow channel 457. In this way, the laminar flow element 450 partially closes the flow channel extending around the stabilizing rod. The fluid flowing along the flow channel must then flow along the internal flow passage 457 or along the fluid sensing portion 426 defined between the outer wall of the flow channel and the first section 451A of the stabilizing bar.

[0076] Fig.14A cross-sectional view of a portion of a fluid sensing device 520 of a fifth embodiment is shown, showing a laminar flow element 550 and a flow channel 521. The fluid sensing device 520 is structurally similar to the fluid sensing device 320 of the third embodiment. However, in the case of the fluid sensing device 520 of the fifth embodiment, the flow channel 521 has a constant diameter, and a flow restriction portion 525 is provided by gradually increasing the diameter of the flow stabilizing bar. In this arrangement, the pressure drop across the flow restriction portion can be changed as required for a given processing volume simply by changing the laminar flow element to a laminar flow element with a different geometry and / or size. In this example, the increase in diameter is uniform around the periphery of the flow stabilizing bar, and includes tapering the flow stabilizing bar outward in a downstream direction extending around the entire periphery of the flow stabilizing bar.

[0077] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. A fluid sensing device, comprising: a fluid flow channel having an inlet and an outlet; a flow-limiting portion located between the inlet and the outlet; a first fluid port at a first location in the fluid flow passage upstream of the restriction; a second fluid port at a second location in the fluid flow passage downstream of the restriction; a fluid sensor in fluid communication with the first and second fluid ports; as well as a laminar flow element comprising a flow stabilizing bar extending along the fluid flow channel at least from the first position to the second position to define a fluid sensing portion of the fluid flow channel between an outer wall of the fluid flow channel and an outer surface of the flow stabilizing bar and between the first position and the second position, wherein the flow restriction portion comprises reducing a hydraulic diameter of the fluid sensing portion of the fluid flow channel by reducing a cross-sectional area of ​​the fluid flow channel and / or by increasing a cross-sectional area of ​​the flow stabilizing bar, and wherein the outer surface of the flow stabilizing bar is substantially continuous. 2 . The fluid sensing apparatus of claim 1 , wherein the cross-section of the fluid flow channel is circular, and wherein the flow restriction portion comprises reducing the diameter of the outer wall of the fluid flow channel.

3. A fluid sensing device according to claim 1 or claim 2, wherein the cross-sectional area defined by the outer surface of the flow stabilizing rod is substantially constant along substantially the entire length of the fluid sensing portion. 4 . The fluid sensing apparatus of claim 1 , wherein the flow restriction portion comprises an increase in a cross-sectional area defined by the outer surface of the flow stabilizing rod.

5. The fluid sensing device of claim 1, wherein the flow stabilizing bar includes one or more internal flow passages defining an additional flow portion of the fluid flow channel separate from the fluid sensing portion.

6. A fluid sensing device according to claim 1, wherein the flow stabilizing rod extends along the fluid flow channel from a position upstream of the first position to a position adjacent to the second position, or from a position adjacent to the first position to a position downstream of the second position, or from a position upstream of the first position to a position downstream of the second position. 7 . The fluid sensing device according to claim 1 , wherein the laminar flow element further comprises a support member, and a stabilizing rod is installed in the fluid flow channel through the support member.

8. The fluid sensing apparatus of claim 7, wherein the support defines at least one fluid flow hole in communication with the fluid sensing portion.

9. The fluid sensing apparatus of claim 8, wherein the at least one fluid flow hole comprises a plurality of fluid flow holes spaced at intervals around a circumference of the support.

10. The fluid sensing apparatus of claim 9, wherein the at least one fluid flow hole comprises a plurality of fluid flow holes spaced at regular intervals around a circumference of the support.

11. A fluid sensing device according to any one of claims 8 to 10, wherein the support member has an outer surface whose shape corresponds to or is consistent with the shape of the outer wall of the fluid flow channel, so that during use, the fluid flowing along the fluid flow channel basically does not flow between the outer surface of the support member and the outer wall of the fluid flow channel.

12. A fluid sensing apparatus according to any one of claims 7 to 10, wherein the support is removably secured within the fluid flow channel.

13. The fluid sensing apparatus of claim 11, wherein the support is removably secured within the fluid flow channel.

14. The fluid sensing device of claim 1, wherein the fluid sensor is configured to measure a first pressure in the first fluid port and to measure a second pressure in the second fluid port.

15. A fluid sensing device according to claim 1, wherein the first fluid port and the second fluid port form part of a bypass channel, during use, a portion of the fluid flow along the fluid flow channel is diverted along the bypass channel, and wherein the fluid sensor is configured to measure the bypass flow rate through the bypass channel.

16. A fluid sensing device according to claim 1, which also includes another fluid sensor, wherein the fluid sensing portion includes a first fluid sensing portion extending from the first position to the second position and a second fluid sensing portion extending from a third fluid port at a third position of the fluid flow channel upstream of the flow restriction portion to a fourth fluid port at a fourth position of the fluid flow channel downstream of the flow restriction portion, wherein the fluid sensor is fluidically connected to the first fluid sensing portion through the first fluid port and the second fluid port, and wherein the other fluid sensor is fluidically connected to the second fluid sensing portion through the third fluid port and the fourth fluid port.

17. The fluid sensing apparatus of claim 16, wherein the flow stabilization rod is offset from a central axis of the fluid flow channel.

18. A mass flow controller comprising: Fluid control valves; Control electronics; as well as The fluid sensing device according to any one of claims 1 to 17, Wherein the control electronics is configured to control the fluid control valve based on a sensor signal provided by the fluid sensing device.

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