Fluid differential pressure measuring device with diaphragm

Abstract

A kind of fluid differential pressure measuring device, measuring diaphragm, push rod, first cavity, second cavity;Measuring diaphragm is limited between first cavity and second cavity to form measuring diaphragm unit, and measuring diaphragm unit is used to respond fluid differential pressure;Push rod passes through and is connected with the measuring diaphragm;The first cavity and second cavity have through hole, and the hole edge is connected with the push rod, and the structure of the connection includes telescopic part, and the telescopic part is used to realize the isolation of the corresponding cavity measuring pressure space and the displacement of the push rod;The push rod conducts the axial force generated by the measuring diaphragm unit to sensor or mechanical indicating mechanism, to realize the measurement of relevant variable of the fluid differential pressure.The design optimizes the structure of micro differential pressure sensor with measuring diaphragm, so that measuring pressure cavity and force transmission cavity are completely independent, and multiple fluid differential pressure sensing measurement can be realized, and can be widely applied.

Description

Technical Field

[0001] This utility model relates to the field of industrial and civil fluid measurement, specifically to a fluid differential pressure measuring device. Background Technology

[0002] In the field of micro-differential pressure measurement of fluids in industrial and civil pipelines, some devices use measuring diaphragms in conjunction with force sensors or conversion mechanisms to measure micro-differential air pressure. For example, DWYER Corporation in the United States offers several products equipped with measuring diaphragms for measuring differential pressures ranging from 5 Pa to 2000 Pa. These products confine the measuring diaphragm within a high-pressure measuring chamber and a low-pressure measuring chamber. The measuring diaphragm senses the fluid pressure difference and causes displacement of a push rod, which is then measured using a displacement sensor, force sensor, or conversion mechanism.

[0003] This type of product has advantages such as reasonable structure and low cost. However, in the structure of this type of product, the pressure measuring chamber of the measuring diaphragm contains a force transmission component or sensor. This design is not conducive to measuring the pressure difference of corrosive gases or liquids, which limits the wider application of this type of product.

[0004] Furthermore, this type of measuring device with a measuring diaphragm generally only measures a single pressure difference and cannot perform sensing and calculation of multiple pressure differences, which limits the wider application of this type.

[0005] In summary, using measuring diaphragms to better measure pressure differences of corrosive gases or liquids is an urgent problem to be solved; at the same time, there is room for further improvement in the sensing and calculation of multiple pressure differences. Utility Model Content

[0006] This invention features an innovative design for a measuring diaphragm structure. A typical design includes: a measuring diaphragm, a push rod, a first cavity, and a second cavity. The measuring diaphragm is positioned between the first and second cavities to form a measuring diaphragm unit, which is used to sense fluid pressure differentials. The push rod passes through and connects to the measuring diaphragm. The first and second cavities have through openings, the edges of which are connected to the push rod. The connecting structure includes a telescopic section, which is used to isolate the measuring pressure space of the corresponding cavities and to displace the push rod. The push rod transmits the axial force generated by the measuring diaphragm unit to a sensor or mechanical indicating mechanism to measure the relevant variables of the fluid pressure differential.

[0007] Furthermore, the opening and the telescopic part have a preset shape and area, so that the effective high-pressure sensing area and the effective low-pressure sensing area of ​​the measuring diaphragm unit are equal.

[0008] Furthermore, the telescopic part is made of a thin material with a low elastic modulus.

[0009] Furthermore, the back pressure spaces at both ends of the push rod are configured to have equal pressure.

[0010] Furthermore, the spaces at both ends of the push rod are configured to be at ambient air pressure and have the same pressure.

[0011] Furthermore, the spaces at both ends of the push rod are connected by pipes and linked to the same pressure space to achieve the same pressure.

[0012] Furthermore, the measuring device is configured to perform zero-position calibration and measurement with the push rod in a vertical position.

[0013] Furthermore, the measuring device is configured to perform zero-position calibration and measurement when the push rod is in a horizontal state; the measuring device includes an elastic rope suspending the push rod to achieve centering of the push rod.

[0014] Furthermore, the push rod is provided with a limit component for overpressure protection.

[0015] Furthermore, the measuring device includes multiple measuring diaphragms, which are respectively located between their respective first and second cavities to form multiple measuring diaphragm units; the measuring diaphragms pass through and are connected to the push rod in sequence, and the measuring diaphragm units sense the corresponding fluid pressure difference and generate corresponding axial forces that act together on the push rod.

[0016] This design optimizes the structure of a micro differential pressure sensor with a measuring diaphragm, eliminating the need for force transmission components or sensors within the pressure measuring chamber, thus expanding the measurement range of the fluid being measured. It has wide applicability. Attached Figure Description

[0017] Figure 1 is a cross-sectional view of Example 1 of the fluid differential pressure measuring device.

[0018] Figure 2 is a cross-sectional view of Example 2 of the fluid differential pressure measuring device.

[0019] Figure 3 shows an example of a displacement sensor.

[0020] Figure 4 shows Example 2 of measuring the diaphragm.

[0021] Figure 5 shows Example 2 of the diaphragm measurement unit.

[0022] Figure 6 shows Example 3 of the diaphragm measurement unit.

[0023] Figure 7 shows a three-dimensional view of the diaphragm.

[0024] Figure 8 shows a three-dimensional view of the connecting diaphragm.

[0025] Figure 9 is a three-dimensional view of the first cavity.

[0026] Figure 10 shows an example of a measuring diaphragm with a pull rope.

[0027] Figure 11 is a schematic diagram of the measuring valve assembly in application example 1.

[0028] Figure 12 is a schematic diagram of the measuring valve assembly in application example 2.

[0029] Figure 13 shows application example 1.

[0030] Figure 14 is a partial cross-sectional view of application example 1.

[0031] Figure 15 shows application example 2. Detailed Implementation

[0032] Example 1 of the fluid differential pressure measuring device in this utility model is a design of an average value measuring device for air micro differential pressure with a multi-diaphragm structure for the HVAC field. Figure 1 is a cross-sectional view.

[0033] The diagram shows four measuring diaphragm units; a first cavity 201, a second cavity 202, and a measuring diaphragm 1 located between them constitute a measuring diaphragm unit. The first cavity and the second cavity can be collectively referred to as the measuring pressure cavity; the measuring pressure cavity and the measuring diaphragm together constitute a high-pressure measuring space 18 and a low-pressure measuring space 19; the high-pressure measuring space 18 and the low-pressure measuring space 19 can be collectively referred to as the measuring pressure space. The first cavity and the second cavity are fastened together using mounting bolts 24.

[0034] As shown in Figure 9, the first cavity 201 is made of aluminum alloy and is a hollow cylindrical shape with a wall thickness of 1mm and an inner diameter of 65mm at the diaphragm mounting location. It has 6 through holes 25 for connecting with the second cavity 202, and 6 screw holes 27 on the inner edge for connecting and fixing the diaphragm. The outer edge is designed with an annular groove 30 for sealing and limiting the measuring diaphragm. The inner edge is designed with an annular groove 30 for sealing and limiting the connecting diaphragm 4. The upper part of the cavity is designed with a strip groove 23 for connecting the space between the cavities to the external environment, so that the pressure in the middle space 20 or the end cap 205 is the same as the air pressure in the external environment. The side of the cavity is designed with a cavity nozzle 21 for connecting the measuring tube 13. The central space 20 is located between the two pressure measuring chambers and is separated from the measured air by a connecting diaphragm. In the example, there are 3 central spaces. After adopting the design of the strip groove 23, their pressure is the same as the ambient pressure. Since the pressure inside the end cap 205, the pressure inside the force transmission chamber 206, and the pressure sensed by the sensor vent are also the ambient pressure, the resultant force of the axial force of the external environment on the push rod is basically zero.

[0035] The space outside the first cavity 201 at the top of the diagram is protected by an end cap. The space inside the end cap has the same pressure as the environment due to the effect of the strip groove. The force transmission cavity and the second cavity 202 at the bottom are connected by screws 31 to protect the corresponding space. A vent 22 is provided on the outside of the force transmission cavity to ensure that the pressure inside the cavity is the same as the environment.

[0036] The measuring diaphragm refers to the diaphragm used to drive the push rod. It has a high-pressure measuring space 18 and a low-pressure measuring space 19 on its two sides. The measuring diaphragm is a key component for sensing fluid pressure differences. In this example, it is connected and fixed to the push rod 5 via a set screw or other components. The push rod 5 is a rigid component connected to the measuring diaphragm and driven by it, transmitting force to a sensor or mechanical indicating mechanism. This force changes with the fluid pressure difference. It can generally be designed as a circular shaft; multiple rods can be connected to the measuring diaphragm separately and then combined. In this example, a solid PVC cylinder with a diameter of 4mm is used, but it can be optimized as a hollow cylinder. In this example, four measuring diaphragm units sense the fluid pressure difference and generate corresponding axial forces. These axial forces act together on the push rod, and the middle diaphragm is subjected to the resultant force of multiple axial forces applied by the push rod. The middle diaphragm senses this resultant force and then transmits the corresponding pressure through the intermediate medium 8 in the pressure-conducting tube 11, thereby enabling the pressure-sensitive layer in a differential pressure sensor such as a MEMS to sense the change in the resultant force. Various force transmission components can be designed between the push rod and the sensor or mechanical indicating mechanism. These force transmission components sense the axial force of the push rod and transmit it to the sensor or mechanical indicating mechanism. The transmission process may involve changes in the magnitude or direction of the force, and can consist of one or more components. In the example, a pressure plate, intermediate diaphragm, and pressure-conducting tube constitute the force transmission component. The mechanical indicating mechanism is a mechanical transmission structure that transmits, amplifies, or transforms the force transmitted by the push rod, using a mechanical display component to indicate the measured value. Examples include combinations of connecting rods, gears, pointers, and leaf springs, widely used in differential pressure gauges for cleanrooms.

[0037] As shown in Figure 7, in the example of the measuring device, the measuring diaphragm is circular. Its push rod mounting part 101 is made of rigid material, including a mounting hole 101a for the push rod, a screw hole 27 for fixing the push rod, and a limiting groove 30 for connecting and limiting the diaphragm 4. The push rod mounting part is fixedly connected to a rigid diaphragm 102 with a thickness of 1 mm. The mounting part and the rigid diaphragm can be made of PVC or other lightweight materials, and can be integrally molded using a mold, with reinforcing ribs designed locally. The rigid diaphragm is connected to the soft diaphragm 104 at the junction 103 using an adhesive bonding process. The soft diaphragm body is 1 mm thick and has a telescopic part 28 and limiting ribs 29. The soft diaphragm is made of silicone. The telescopic part is designed with a thin wall, combining the low elastic modulus and super-elasticity of silicone to adapt to the displacement of the rigid part and reduce the corresponding additional axial force. The flexible diaphragm can be manufactured and connected to the rigid diaphragm using a partial overmolding process. In the manufacturing process, the interface of the rigid diaphragm is first cleaned and pre-treated, then a special adhesive is applied, and liquid silicone is used to vulcanize and mold the diaphragm around its perimeter to obtain the measuring diaphragm. In actual manufacturing, the push rod mounting part of the measuring diaphragm and the rigid diaphragm can be designed as separate parts. After the rigid and flexible diaphragms are connected and molded, the push rod mounting part and the rigid diaphragm are then bonded or welded together for fixation.

[0038] The rigid portion of the measuring diaphragm can be flexibly designed, as shown in Example 2 of Figure 4; it modifies the measuring diaphragm design of Example 1 of the measuring device. In this example, the soft diaphragm 104 is directly connected to the mounting portion, and a rigid annular thin plate 39 replaces the rigid diaphragm. The rigid annular thin plate and the soft diaphragm are bonded together to form a rigid composite layer. Furthermore, by controlling the inner diameter of the rigid annular thin plate, a soft gap can be left near the mounting portion to dampen axial forces.

[0039] The radial cross-section of the telescopic part can be a semi-circular ring as shown in the example; it can be designed with a thickness of approximately 50 μm, and the inner radius of the ring can be designed to be 1~2 mm. The thickness or inner diameter can be adjusted based on the elastic modulus of the silicone under different stresses to calculate the additional axial force, or by referring to the tensile strength of the silicone. The calculation of the additional axial force can be based on the maximum displacement of the push rod, combined with the elastic modulus and dimensions. The telescopic part can be designed in other different shapes.

[0040] The connecting diaphragm 4 connects the measuring diaphragm to the high-pressure or low-pressure chamber. Figure 8 shows a three-dimensional view of the connecting diaphragm. The connecting diaphragm is fixed to the chamber by screws 31 passing through an annular gasket 32 ​​and through-hole 25, forming a sealed space between the high-pressure or low-pressure chamber. A telescopic section 28 is also designed, using a thin material with low elastic modulus to accommodate the displacement of the push rod and reduce the corresponding additional axial force. The center of the annular gasket 32 ​​is located on the push rod axis and can be made of various rigid materials; other connection methods such as bonding can also be used to achieve a seal between the connecting diaphragm and the chamber. In the example, the connection between the connecting diaphragm and the measuring diaphragm is designed with a partially concave shape in the measuring pressure chamber to facilitate convenient and accurate installation positioning. The connecting diaphragm can be made of silicone and injection molded. The shape and size of the telescopic section can be consistent with the telescopic section of the measuring diaphragm, or the thickness or inner diameter of the telescopic section can be adjusted based on the calculation of the additional axial force according to the elastic modulus corresponding to different stresses.

[0041] The connection between the aforementioned connecting diaphragm and the measuring diaphragm essentially achieves a flexible connection between the measuring pressure chamber and the push rod. In practical designs, the measuring pressure chamber can be directly connected to the push rod via the connecting diaphragm. In this case, the measuring diaphragm can be connected to the push rod using a push rod mounting part of other shapes.

[0042] During measurement, the pressure difference between the two sides of the measuring diaphragm, connecting diaphragm, and intermediate diaphragm increases, leading to increased internal stress. This increases the radial force exerted by the diaphragm on the centrally located push rod. The annular design of the expansion joint allows the diaphragm to center the push rod; the centering performance improves with increasing pressure difference. Example 1 fully utilizes the inherent centering function of the measuring diaphragm, connecting diaphragm, and intermediate diaphragm. The combination of a vertical push rod and a horizontal diaphragm achieves excellent centering characteristics. The expansion joint can be made of various types of rubber materials with low elastic modulus and high elasticity.

[0043] Furthermore, the measuring diaphragm can be designed and improved. The measuring diaphragm in Figure 10 is an improvement on the measuring diaphragm of the measuring device example 1, with the addition of 6 pull ropes 38. The annular portion containing limiting ribs near the through hole is made of rigid PVC material, and the pull ropes 38 are located between the junction and the aforementioned annular portion. The pull ropes have a preset length and a certain tensile strength; they can be made of lightweight materials such as polypropylene fiber or glass fiber; low-elongation materials are preferred. When the push rod is in the centered state, the pull ropes are in a slack state. When the push rod is displaced due to device vibration or external force, the pull ropes can extend and straighten to limit the push rod mounting part, preventing excessive displacement that could damage the telescopic part and cause significant disturbance to the differential pressure measurement value. The diameter and number of pull ropes can be determined based on the ultimate tensile force calculation and experiment. In the design of the measuring device, the position of the pull ropes can be flexibly set, not limited to the diaphragm, but can be set between the push rod and the side wall of the cavity; simultaneously, pull ropes with the same function can also be set inside the intermediate diaphragm and the connecting diaphragm for limiting.

[0044] The installation of the pull rope can be achieved through a drilling and glue-filling process. First, drill holes of a certain depth in the relevant areas, clean the inside of the holes, apply special adhesive to the inside of the holes, place the pull rope in the holes, and use precision glue-filling equipment to fill the holes with special glue, allowing the glue to stand and cure.

[0045] The components of the septum 3 in the example include a rigid part 301 of the intermediate septum, a telescopic part 28, and an annular fixing part 302 connected to the telescopic part.

[0046] The annular fixing part is connected and fixed to the force transmission cavity 206, forming a seal on the pressure-conducting cavity. The force transmission cavity is made of stainless steel. The telescopic part 28 is annular, with a cross-sectional shape consistent with the telescopic part of the measuring diaphragm. It is made of a thin material with low elastic modulus, and can be designed to be about 50 μm thick. The inner radius of the annulus can be designed to be 1~2 mm. The additional axial force can be calculated based on the elastic modulus of the material under different stresses, and the above thickness and inner diameter can be adjusted accordingly. A soft material that is immiscible with the intermediate medium 8, such as fluorosilicone rubber, can be used. The rigid part of the intermediate diaphragm can be made of lightweight materials, such as Teflon or PVC; or it can be made of stainless steel sheet. The annular fixing part can be made of stainless steel. The forming and connection process of the telescopic part of the intermediate diaphragm can adopt a local wrapping forming process similar to that of the measuring diaphragm. The connection and fixation between the intermediate septum and the force transmission cavity can be achieved by welding. A limiting step can be machined into relevant parts of the force transmission cavity, and the intermediate septum can be placed on it. Pulse laser welding is then performed under the pressure of the heat dissipation fixture. After welding, sealant is applied for sealing. Alternatively, the connection and fixation between the intermediate septum and the force transmission cavity can refer to the gasket design in CN 202580374 U "Compression-type Pipe Fittings" for compression and fixation of the intermediate septum. Internal installation threads can be machined into relevant parts of the force transmission cavity. Grooves can be machined into relevant parts of the force transmission cavity to place O-rings, and the intermediate septum is placed on top of the O-rings. A gasket with external threads is machined, and mounting bosses and other mounting parts are machined on the gasket. Using a clamp, the gasket is screwed into the force transmission cavity, and the O-ring is compressed to form a seal on the intermediate septum.

[0047] The measuring diaphragm, intermediate diaphragm, and soft parts connecting the diaphragm can be manufactured using mold compression molding or injection molding processes. During the manufacturing process, the control of vulcanization temperature can be optimized or secondary vulcanization can be implemented to improve molding accuracy.

[0048] In the example, the push rod end is designed with a boss 34 for limiting the cylindrical helical spring 33; the other end of the cylindrical helical spring 33 is limited to the lower pressure plate 35 with a boss. A retaining ring 502 and a locking sleeve 501 with a set screw are used to limit the push rod 5 to prevent overpressure of the sensor; the limiting plate 10 is connected by a screw on the side and a force transmission cavity, used to limit the push rod, and its position can be adjusted vertically. The spring 33 is located between the push rod and the pressure plate, and can dampen the force between the push rod and the sensor. The spring, as a damping component, works in conjunction with the limiting component to achieve good overpressure protection performance; the spring can be designed as other damping components such as a rubber spring. The damping component is not a necessary component in this invention and can be designed as needed. In the design, the pressure plate can be connected and fixed using adhesive and an intermediate septum; the pressure plate and the intermediate septum may also not be connected.

[0049] A gap is left between the push rod and the limiting plate, so that there is no resistance to the push rod at this point, and at the same time, the back pressure above the diaphragm in the middle is the ambient pressure; through holes can be further provided on the limiting plate to balance the air pressure.

[0050] When the four pressure measuring chambers are connected to the same pressure, zero-point calibration can be performed via the circuit. During measurement, the push rod is pushed downward slightly by the corresponding measuring diaphragm, and a greater pressure is applied to the pressure plate 35 by the spring. After transmission through the intermediate diaphragm, the pressure of the intermediate medium increases, and the sensor transmits a signal to the calculation circuit, which can calculate the arithmetic mean of each pressure difference. When the air pressure difference is too large, the push rod will be blocked by the limiting plate for overpressure protection. During the measurement process, the pressure of an individual first chamber may be less than the pressure of the corresponding second chamber, causing the corresponding measuring diaphragm to exert an upward axial force on the push rod.

[0051] Furthermore, when the four sets of pressure measuring chambers are connected to the same air pressure difference, the force exerted by each measuring diaphragm on the push rod is the same, and the calculation circuit can obtain the air pressure difference value.

[0052] In Example 1, the actual forces acting on the intermediate septum include the axial force exerted by the diaphragm unit on the push rod, the back pressure, and the pressure generated by the weight of the push rod and diaphragm components. In this invention, the axial force refers to the axial force generated by the pressure of the fluid being measured in the pressure measurement space on the push rod, excluding the axial force generated by the diaphragm's own weight. The resultant force of these axial forces acts on the intermediate septum with a corresponding pressure, which can be positive or negative depending on the direction. In practical design, the first chamber can be connected to the low-pressure side of the fluid, and the second chamber can be connected to the high-pressure side of the fluid. The axial force acting on the push rod is upward, and the pressure sensed during the differential pressure sensing layer test is less than the pressure at zero. This design is also feasible.

[0053] Compared to traditional single-diaphragm designs, the design of multiple diaphragm measuring units achieves the arithmetic mean of multiple pressure differences at a lower cost, making it widely applicable in fluid flow measurement. It also allows for a smaller size, facilitating industrial applications. Furthermore, with appropriate design, the displacement of the measuring diaphragm during measurement is minimal, or even negligible after eliminating damping, reducing the breathing effect of the measuring chamber. Various precision filters can be installed at suitable locations on the measuring tube 13 to prevent dust from causing sensing errors in the measuring diaphragm.

[0054] The intermediate medium that works in conjunction with the intermediate diaphragm, as a liquid medium for transmitting pressure, can be an electrically insulating liquid with a small coefficient of expansion, such as silicone oil, or a liquid medium such as natural or synthetic grease; the rigid pressure-conducting tube 11 is connected to the sensor nozzle 601, and silicone oil fills the space between them up to the differential pressure sensitive layer; the differential pressure sensor transmitter 6 has a vent 22 at the bottom so that the pressure on the other side of the sensor is the ambient pressure.

[0055] The differential pressure sensor can employ existing wet-type semiconductor strain gauge MEMS sensors. The strain gauges change resistance through the piezoresistive effect. The core structure of the sensor is fabricated using a series of mature micro-nano fabrication processes, such as silicon etching, bonding, and sacrificial layer release, ensuring good reliability. Typically, four semiconductor strain gauges are integrated onto the sensitive membrane. These strain gauges are usually formed through selective doping, such as boron diffusion. They are arranged in different strain regions of the membrane and connected to form a Wheatstone bridge circuit. When a differential pressure exists, the deformation of the sensitive membrane causes the resistance of each strain gauge to change in opposite directions, resulting in a differential voltage signal output by the bridge that is proportional to the differential pressure. This sensitive membrane acts as the differential pressure sensing layer, sensing the pressure from the silicone oil on one side and the ambient pressure on the other. With zero fluid pressure differences in the four measuring diaphragm units, the differential pressure sensor can achieve zero-point calibration. The pressure at the sensor vent, the central space, the force transmission cavity, and the space inside the end cap does not need to be the ambient pressure. These pressures can be obtained by connecting to other pressure spaces through pipes; this pressure can be called the reference pressure or back pressure.

[0056] In summary, the spaces of the sensor's vent, the central space, the force transmission cavity, and the end cap in Example 1 can be collectively referred to as the back pressure space. The back pressure space is one or more pressure spaces, characterized in that it is not a measurement pressure space, but its pressure acts on the connecting diaphragm, the cross-section of the push rod, the central diaphragm, or the measuring diaphragm, forming an axial force on the push rod. The pressure of the back pressure space may affect zero-point calibration. In Example 1, the pressure in the central space acts simultaneously on the mounting parts of both the connecting diaphragm and the measuring diaphragm. Since the mounting parts on both sides are fixedly connected to the push rod, it forms a bidirectional axial force on the push rod. If the pressure in the central space is not equal to the ambient pressure, since the four measuring diaphragm units are designed with identical shapes and sizes, the actual impact on zero-point stability is relatively small. Inconsistent pressures in the force transmission cavity, the sensor vent, and the end cap will significantly affect measurement accuracy and zero-point calibration.

[0057] The differential pressure sensor can also utilize existing technology, employing a capacitive MEMS differential pressure sensor filled with silicone oil and featuring a wet channel, achieving measurement in conjunction with an intermediate diaphragm. The core structure consists of a pair of parallel opposing plates, with a movable plate fixed to a fixed plate via a suspended support structure, forming a sensing capacitor. When the sensor is subjected to external pressure, the intermediate medium applies pressure to the movable plate, causing elastic deformation and altering the distance between the two plates, resulting in a change in the capacitance value of the sensing capacitor. The movable plate uses an insulating material as the contact diaphragm, such as alumina ceramic coated with a metal film or a single-crystal silicon diaphragm. These materials not only possess excellent mechanical strength and overload resistance, but their insulating properties also help reduce leakage current and improve signal stability, making them suitable for differential pressure monitoring under complex operating conditions. The sensing capacitor is connected to a signal processing circuit; its changes are processed by the circuit and accurately converted into an electrical signal output proportional to the differential pressure, achieving high-precision pressure measurement.

[0058] Differential pressure sensors can also be resistance strain gauge sensors, which use metal strain gauges as resistance strain gauges and are attached to the differential pressure sensitive layer to form a bridge to output differential pressure signals.

[0059] With the intermediate diaphragm and the measuring diaphragm unit structure clearly defined, the average value of the pressure difference measured by the aforementioned differential pressure sensor and the pressure difference of the measured air can be used for calculation of the calculation circuit based on structural parameters such as the effective sensing area of ​​the diaphragm or by establishing a linear relationship through experiments.

[0060] In the example, the height of the intermediate septum is lower than the height of the differential pressure sensor. This height difference reduces the stress on the differential pressure sensing layer when it is at the zero-point measurement position. The pressure-conducting tube can be a pipe with a smaller inner diameter, such as a stainless steel capillary tube with an inner diameter of 50µm, to reduce the impact of intermediate medium expansion on the zero-point measurement. After being sealed on both sides by the intermediate septum and the pressure-sensitive layer, the pressure-conducting tube becomes a closed space, which can be called a pressure-conducting cavity. Its form can be simplified; the differential pressure sensor can be placed below the intermediate septum, shortening the length of the pressure-conducting cavity. Using a thinner or shorter pressure-conducting cavity significantly reduces the additional pressure effect caused by the volume change of silicone oil at different temperatures, avoiding a significant impact on measurement accuracy and zero-point calibration.

[0061] The liquid column filled with silicone oil below the intermediate diaphragm expands or contracts with temperature changes, causing its height to change accordingly. The density of the silicone oil changes accordingly, ensuring that the pressure exerted by the liquid column on the differential pressure sensitive layer remains essentially unchanged with temperature. This characteristic, combined with the optimized design of the pressure-conducting cavity, results in minimal zero-point drift of the measuring device; if necessary, temperature measurement can also be used to compensate for and correct the zero point.

[0062] Furthermore, microporous components can be incorporated into the conduction channels of the intermediate medium to prevent liquid hammer from affecting the sensor. Alternatively, a sintered filter can be placed in front of the differential pressure sensing layer to reduce the impact of the intermediate medium's inertia, thereby minimizing its adverse effects on sensor measurements. A filter gap of 5-10 μm can be used, and the optimal position and configuration of the sintered filter can be determined experimentally.

[0063] The intermediate septum can be configured with a smaller area to further amplify the pressure value. Micro-differential pressure measurement can be achieved using a higher range and more economical differential pressure sensor, with measurement accuracy and stability exceeding that of some small-range differential pressure sensors. For example, a typical piezoresistive 2000 Pa MEMS sensor, compared to a piezoresistive 100 Pa MEMS sensor, has a larger or thicker differential pressure sensing layer under the same structure. The pressure-sensitive structure often has higher rigidity, and its sensitivity to external interference such as encapsulation stress and temperature fluctuations is often significantly reduced, exhibiting better overall stability. Specifically, this includes lower full-scale temperature drift, lower zero-point temperature drift, lower zero-point temperature rise drift, and lower long-term zero-point drift. When a measurement device is designed with a 2000 Pa sensor and an intermediate septum, it can have lower zero-point drift compared to a 100 Pa sensor with the same structure. In micro-differential pressure measurement in the HVAC field, zero-point drift error is one of the main technical indicators that needs to be guaranteed. The combination of a measuring diaphragm, an intermediate septum, and a higher range sensor can lead to better applications. The design of the measuring device example 1 can use a piezoresistive MEMS differential pressure sensor with a higher range, which can achieve low zero-point drift measurement of differential pressure of 5~100pa while ensuring measurement accuracy.

[0064] When the measuring device example 1 measures only a single air pressure difference, only a pair of first and second chambers can be designed. Further, the structure can be simplified by having the force sensing chamber directly serve as the second chamber, eliminating the air vent and adding a chamber nozzle to connect the force sensing chamber to the low-pressure side of the measured air, allowing the pressure of the force sensing chamber to act directly on one side of the measuring diaphragm; eliminating the diaphragm connection allows the high-pressure fluid to act on the entire other side of the measuring diaphragm, including the middle section, as in the diaphragm structure of the Magnesense series sensors from Dwyer, USA; in this case, the back pressure of the differential pressure sensor's differential pressure sensing part needs to be kept consistent with the measured low pressure.

[0065] Based on the measurement device example 1, when only a pair of first and second chambers are designed, the diameter of the intermediate septum can be designed to be in the range of 6mm to 10mm to achieve a 40 to 100 times amplification of the measured pressure. A differential pressure sensor with a range of 4kpa to 10kpa can be designed to achieve an air pressure differential measurement range of 100pa. A larger inner diameter of the measuring pressure chamber can be designed to increase the diameter of the intermediate septum.

[0066] The design of the measuring device in Example 1 is suitable for differential pressure measurement of various gaseous fluids. When applied to liquid differential pressure, after the measured medium enters the measuring diaphragm, an exhaust pipe and exhaust device can be connected to an appropriate location in the pressure chamber to expel air, achieving a certain level of measurement accuracy. For liquid differential pressure measurement, a diaphragm similar to an intermediate diaphragm can also be added to the pressure measuring channel, allowing the measuring diaphragm to remain filled with air; one side of the added diaphragm is air, and the other side is the fluid being measured. This design can also achieve a certain level of measurement accuracy. A typical design with an intermediate diaphragm and intermediate medium can be summarized as a fluid differential pressure measuring device with an intermediate medium, characterized by comprising a measuring diaphragm, a push rod, an intermediate diaphragm, an intermediate medium, a pressure-conducting cavity, and a differential pressure sensitive layer; the measuring diaphragm is located between a first cavity and a second cavity; one end of the push rod is fixedly connected to the measuring diaphragm, and the other end of the push rod is provided with the intermediate diaphragm; the intermediate diaphragm is disposed on one side of the pressure-conducting cavity, and the differential pressure sensitive layer is disposed on the other side of the pressure-conducting cavity, the pressure-conducting cavity being a closed structure filled with the intermediate medium; the middle portion of the measuring diaphragm and the middle portion of the intermediate diaphragm each include a rigid portion with a predetermined area, the edges of the rigid portions being fixedly connected to telescopic portions, the telescopic portions being used to realize the displacement of the rigid portions; the measuring diaphragm senses the fluid differential pressure and generates an axial force acting on the push rod, the intermediate diaphragm senses the axial force and causes the differential pressure sensitive layer to deform through the intermediate medium; the deformation causes changes in the electrical parameters of the relevant components of the differential pressure sensitive layer, the changes being used by the signal processing circuit to output the fluid differential pressure signal. The preferred design prioritizes a horizontally positioned diaphragm. This horizontal positioning fully utilizes the diaphragm's centering characteristics, ensuring that horizontal interference forces or vibrations do not significantly affect the measurement structure, thus providing horizontal anti-interference capabilities. In this design, since the intermediate medium transmits fluid pressure, the position and orientation of the differential pressure sensitive layer can be flexibly set; for example, the differential pressure sensitive layer can be adjacent to the intermediate diaphragm, forming a compact structural design.

[0067] The differential pressure measuring device can also adopt a vertical placement design for the diaphragm, as shown in Example 2 of the fluid differential pressure measuring device in Figure 2. Its design is mostly the same as that of Example 1 of the fluid differential pressure measuring device. After the push rod is placed horizontally, the corresponding measuring diaphragm unit is placed vertically. The intermediate diaphragm is designed to be smaller in size than that in Example 1, and the local parts of the force transmission cavity are modified accordingly. The positions of the nozzles of the 8 cavities are changed to the mirror positions of Example 1. The strip grooves on the 4 first cavities are removed, and the original strip grooves are designed as planes. A back pressure pipe 37 is added and connected to the vents 22 of the 3 central spaces, the force transmission cavity, the end cap, and the sensor. The back pressure pipe can be made of various hard or soft materials. An elastic rope 36 is added in the force transmission cavity and the end cap to suspend the push rod and center it.

[0068] The small size of the intermediate diaphragm amplifies the pressure sensed by the sensor, facilitating measurement and reducing zero-point drift caused by the push rod in a horizontal position. Furthermore, the pressure plate connected to the intermediate diaphragm can be made of a thin, lightweight material; a rubber-type damping component can replace the spring to optimize the force on the intermediate diaphragm; alternatively, the damping component can be eliminated, with the push rod acting directly on the intermediate diaphragm. In this case, a limiting component can be designed on the left side of the intermediate diaphragm or inside the sensor. Under the suspension of the elastic rope, the push rod can be centered at zero position through position adjustment; the elastic rope, as an auxiliary centering component, reduces additional errors caused by misalignment during measurement. The design of the elastic rope can be combined with the aforementioned pull rope design for limiting, forming protection for the telescopic part. The elastic rope can be made of silicone or other rubber materials, and the optimal diameter and design length can be determined experimentally. Alternatively, the design can omit the elastic rope, utilizing the tension generated by the telescopic part of the diaphragm to suspend the push rod while optimizing its weight; in this case, centering is not a necessary measurement condition.

[0069] The three central spaces, force transmission chamber, and end caps are connected by pipes to ensure identical back pressure, allowing for zero-point calibration of the sensor. Furthermore, they can be connected to a suitable pressure space. When measuring air pressure differentials, if the low-pressure value is high, such as when measuring the flow velocity in a high static pressure duct, the back pressure pipe interface 3701 can be connected to the static pressure sampling port in the duct to achieve a higher back pressure. A higher back pressure results in a lower pressure differential across the diaphragm, leading to lower internal stress in the diaphragm's expansion joint, a lower elastic modulus, and thus better working characteristics.

[0070] The horizontally positioned push rod design allows the measuring device to accurately measure minute pressure differences in liquids. After installing a venting device on the back pressure connector and venting measures are taken on the back pressure connector connected to the sensor, most of the gas in the three central spaces, the force transmission chamber, the end cap, and the sensor can be expelled. Further venting by connecting the nozzle to the pressure measuring chamber with a venting device allows most of the gas in the measuring device to be expelled, thus enabling accurate measurement of liquid pressure differences. When measuring liquid pressure differences, a sensor with a vertically positioned pressure-sensitive layer can be used for easy venting.

[0071] The arrangement of the push rod of the differential pressure measuring device is not limited to vertical or horizontal placement; it can also be placed at an angle for certain measurement accuracies.

[0072] The differential pressure measuring device can also be designed using a displacement sensor to achieve differential pressure measurement, as shown in Figure 3. In this design, the push rod is placed in a horizontal position, and a hard steel ball 503 is provided at the end of the push rod. This ball attracts the magnetic seat 904 fixed on the leaf spring 903, thus limiting the push rod. The upper end of the leaf spring is fixed on the force transmission cavity 206. The non-magnetic hard plate 905 is connected and fixed to the magnetic seat 904, and the magnet 901 is fixed to one end of the non-magnetic hard plate. The horizontal position of the magnet 901 changes with the average differential pressure of the fluid being measured. The displacement sensor 902, located inside the circuit cavity 907, senses the positional change of the magnet 901 through the Hall effect and generates an electrical signal that is transmitted to the circuit. The partition 906 isolates the circuit cavity 907 from the force transmission space, ensuring a stable air pressure in the force transmission cavity where the leaf spring is located. A vent 22 is provided on the side of the force transmission cavity 206.

[0073] Differential pressure measuring devices can also employ various force sensors in conjunction with push rods to sense fluid pressure differences. For example, using an S-type force sensor with a 10g range, the push rod is connected to the force-receiving end of the sensor to measure the force. Alternatively, a leaf spring with attached resistance strain gauges can be used. The strain gauges are attached to specific areas of the leaf spring's surface and connected to form a Wheatstone bridge. When an external force is applied to the force-receiving end through the push rod, the leaf spring undergoes a slight deformation, causing a change in the resistance of the strain gauges. The Wheatstone bridge outputs an electrical signal proportional to the applied force, thus achieving accurate force measurement.

[0074] The structure of the measuring diaphragm unit in Example 1 of the measuring device can be modified to achieve the same function, as shown in Figures 5 and 6. In Example 2 of the measuring diaphragm unit, push rods 5, driven by the measuring diaphragm 1, are located within the high-pressure measuring space 18 and the low-pressure measuring space 19. The characteristic feature is that the end face of the first cavity is connected to the movable cavity 26 via the connecting diaphragm 4. The movable cavity 26 is fixedly connected to the push rod, and the second cavity also has a movable cavity 26 of the same area. This design ensures that the effective sensing area for high pressure and the effective sensing area for low pressure of the measuring diaphragm unit are equal.

[0075] In this invention, the effective sensing area for high pressure refers to the area corresponding to the axial force exerted by the fluid pressure in the high-pressure space on the push rod, and the effective sensing area for low pressure refers to the area corresponding to the axial force exerted by the fluid pressure in the low-pressure space on the push rod. Essentially, the movable cavity can be considered part of the push rod; its presence reduces either the effective sensing area for high pressure or the effective sensing area for low pressure.

[0076] Furthermore, the design of the measuring diaphragm unit Example 3 is largely the same as that of Example 2, except that the push rod passes completely through the cavity; after designing a fixed bracket for the cavity, this type can also be applied to a differential pressure averaging device with multiple measuring diaphragms.

[0077] A detailed analysis of the design of the measuring diaphragm in Figure 1 reveals several commonalities in the examples. As shown in the detailed diagram, the high-pressure fluid enters the interior of the telescopic section through the measuring gap 1801, exerting a force on the cross-section of the telescopic section. This force causes a loss in the effective high-pressure sensing area, which is approximately half the projected area of ​​the telescopic section on the horizontal plane. By using the same shape and size for both the first and second cavities, and employing telescopic sections of the same shape and area, the effective high-pressure sensing area and the effective low-pressure sensing area of ​​the measuring diaphragm can be made equal. The advantages of the measuring diaphragm in Figure 1 lie in its simple assembly and smaller manufacturing volume.

[0078] Essentially, in this example, the push rod and the pressure chamber wall are sealed together, achieving isolation of the pressure measurement space within the corresponding chamber and displacement of the push rod. The connection can be made solely through a telescopic section, or it can be a combination of the telescopic section and other components. The telescopic section achieves isolation of the pressure measurement space and displacement of the push rod, including axial and radial displacement. In summary, the aforementioned high-pressure and low-pressure chambers have through openings, the edges of which are connected to the push rod. This connection includes a telescopic section for isolating the pressure measurement space of the corresponding measuring diaphragm unit and displacing the push rod. The opening and the telescopic section have a predetermined shape and area such that the effective sensing area for high pressure and the effective sensing area for low pressure of the corresponding measuring diaphragm unit are equal.

[0079] The telescopic part can be made of a thin material with a suitable elastic modulus so as not to significantly affect the measurement accuracy of the differential pressure sensor. The telescopic part should not be limited to components made of materials such as rubber. Under some operating conditions, the deformation of the differential pressure sensitive layer is minimal. When no damping component is installed, the axial displacement of the push rod is minimal. This should not be interpreted as the push rod having no displacement; in this case, a metal material with a high elastic modulus can be used.

[0080] Meanwhile, the design of multiple measuring diaphragms described above has wide applications in engineering. It achieves complete isolation between the measured fluid and the force transmission components, enabling accurate measurement; it allows for accurate measurement of low-range fluids using high-range differential pressure sensors; and it enables low-cost measurement of the arithmetic mean of multiple fluid differential pressures, significantly reducing manufacturing and maintenance costs.

[0081] Its typical simplified design can be summarized as follows: a fluid differential pressure measuring device, characterized by comprising a measuring diaphragm, a push rod, a first cavity, and a second cavity; the measuring diaphragm is positioned between the first and second cavities to form a measuring diaphragm unit, which is used to sense fluid differential pressure; the push rod passes through and connects to the measuring diaphragm; the first and second cavities have through openings, the edges of which are connected to the push rod, and the connecting structure includes a telescopic part, which is used to isolate the measuring pressure space of the corresponding cavity and to displace the push rod; the push rod transmits the axial force generated by the measuring diaphragm unit to a sensor or mechanical indicating mechanism for measuring the relevant variables of the fluid differential pressure. In the design, the openings and the telescopic part have preset shapes and areas, such that the effective sensing area for high pressure and the effective sensing area for low pressure of the measuring diaphragm unit are equal. The telescopic part is generally a thin material with a low elastic modulus, used to accommodate the displacement of the rigid part and reduce the corresponding additional axial force.

[0082] One of the conditions for the above measurement is that the back pressure spaces at both ends of the push rod are configured to have equal pressure, so that the pressure at both ends of the push rod will not cause interference from axial force during the test; the two ends include the push rod near the end face of the measuring pressure chamber at the beginning and end, for example, near the end face of the second chamber at the bottom in device example 1.

[0083] Furthermore, the back space of the telescopic part and the spaces at both ends of the push rod can be configured to have equal pressure to ensure zero-position stability; furthermore, the back pressure space of the telescopic part and the back pressure spaces at both ends of the push rod can be connected through pipes to the same pressure space to achieve the same pressure.

[0084] The differential pressure measuring device can be configured to perform zero-point calibration and measurement when the push rod is in a vertical position; the differential pressure measuring device can also be configured to perform zero-point calibration and measurement when the push rod is in a horizontal position. Various damping components can be provided between the push rod and the sensor to dampen the force exerted by the push rod on the sensor; various limiting components can be designed.

[0085] The differential pressure measuring device can be configured as multiple measuring diaphragms, each of which is located between its respective first and second cavities to form multiple measuring diaphragm units; the measuring diaphragms pass through and are connected to the push rod in sequence, and the measuring diaphragm units sense the corresponding fluid differential pressure and generate corresponding axial forces that act together on the push rod.

[0086] The design of multiple diaphragms has wide applications in the HVAC field, as shown in Figures 11-15. The meaning and definition of the average differential pressure measuring component in this invention are consistent with those in "A Modular Flow Measurement Method, Device and Its Application," CN 116295672 A. Please refer to this publication for details. Regarding the measuring sub-channel, interval component, measuring sub-region, regional differential pressure, detection tube, and average flow... The definitions of parameters such as velocity-related variables, structural coefficients, theoretical flow coefficients, and measurement flow coefficients are consistent with the published text.

[0087] Figure 13 shows application example 1, and Figure 14 is a partial cross-sectional view of it. The device in Figure 13 modifies the averaging pitot tube to form a novel rhomboid averaging pitot tube. The example includes a first total pressure measuring hole 01h, a second total pressure measuring hole 02h, a third total pressure measuring hole 03h, a fourth total pressure measuring hole 04h, and a first low pressure measuring hole 01l, a second low pressure measuring hole 02l, a third low pressure measuring hole 03l, and a fourth low pressure measuring hole 04l. The space near the first total pressure measuring hole is enclosed by the cavity partition plate 16, the high and low pressure partition plate 14, and the averaging pitot tube wall 15, forming a high-pressure measuring cavity. The other three total pressure measuring holes, using the same design, have corresponding high-pressure measuring cavities, and the four low-pressure measuring holes have corresponding low-pressure measuring cavities. The first total pressure measuring hole, the first low-pressure measuring hole, and the corresponding measuring pressure cavities constitute a measuring module. Similarly, the other total pressure measuring holes and low-pressure measuring holes constitute three other measuring modules.

[0088] The internal pressures of the four high-pressure chambers are led out by the internal measuring tube 17 and connected to the four first chambers through the measuring tube. Similarly, the internal pressures of the four low-pressure chambers are led out by the internal measuring tube 17 and connected to the four second chambers through the measuring tube. The novel averaging pitot tube has a first high-pressure nozzle 1201h, a second high-pressure nozzle 1202h, a third high-pressure nozzle 1203h, a fourth high-pressure nozzle 1204h, a first low-pressure nozzle 1201l, a second low-pressure nozzle 1202l, a third low-pressure nozzle 1203l, and a fourth low-pressure nozzle 1204l. In this design, each pair of tested modules is connected to the corresponding diaphragm measuring unit.

[0089] Figure 11 is a schematic diagram of the measuring valve assembly in Application Example 1. Each measured nozzle and each measuring pressure chamber is connected via measuring tube 13. Individual differential pressure and differential pressure averaging measurements are achieved by controlling the measuring switching valve, thus realizing high-precision flow measurement. The measuring tube can take various forms and, together with the internal measuring tube, can be collectively referred to as the pressure measuring channel.

[0090] Specifically, when the eight unified switching valves v0 are open, the following valves are closed: the first high-pressure measuring valve v01ha, the second high-pressure measuring valve v02ha, the third high-pressure measuring valve v03ha, the fourth high-pressure measuring valve v04ha, the first low-pressure measuring valve v01la, the second low-pressure measuring valve v02la, the third low-pressure measuring valve v03la, the fourth low-pressure measuring valve v04la, the second unified high-pressure measuring valve v02hb, the third unified high-pressure measuring valve v03hb, the fourth unified high-pressure measuring valve v04hb, the second unified low-pressure measuring valve v02lb, the third unified low-pressure measuring valve v03lb, and the fourth unified low-pressure measuring valve v04lb; and the first unified high-pressure measuring valve v01hb and the first unified low-pressure measuring valve v01lb. This valve operation enables individual measurement of the regional differential pressure of the first measured module. This operation uniformly performs the same differential pressure measurement on all measuring diaphragm units, and can be called uniform differential pressure measurement.

[0091] The aforementioned unified switching valve, high-pressure measuring valve, low-pressure measuring valve, unified high-pressure measuring valve, and unified low-pressure measuring valve can be collectively referred to as measuring switching valves.

[0092] Then, the same actions are performed on the second, third, and fourth tested modules and their corresponding measurement switching valves to measure the regional pressure difference corresponding to the second, third, and fourth tested modules. The calculation circuit calculates the average flow velocity of the fluid measurement channel when the area weights of the tested modules are equal; the formula is as follows:

[0093]

[0094] ΔP1, ΔP2, ΔP3, and ΔP4 represent the regional pressure differences corresponding to each measured module, and ρ represents the fluid density.

[0095] k1, k2, k3, and k4 are the theoretical flow coefficients of the four measured modules at different flow velocities. In this invention, the theoretical flow coefficient refers to the flow coefficient of the measurement sub-channel containing the measured module placed in a straight uniform flow field, with a preset flow velocity corresponding to the corresponding pressure difference. When there are no spacers between the measured modules, the measurement sub-channel is the fluid measurement channel; the local measurement area corresponding to the measured module is called the measurement sub-region. The above measurement and calculation achieve a relatively accurate measurement of the total flow rate of the fluid measurement channel.

[0096] Then, eight unified switching valves (v0, v01hb, v01lb, v02hb, v02lb, v03hb, v03lb, v04hb, v04lb) were closed. The following valves were then opened: the first high-pressure valve (v01ha), the second high-pressure valve (v02ha), the third high-pressure valve (v03ha), the fourth high-pressure valve (v04ha), the first low-pressure valve (v01la), the second low-pressure valve (v02la), the third low-pressure valve (v03la), and the fourth low-pressure valve (v04la). The average pressure difference ∆p of the four regions was measured. a The calculation can be simplified; the simplified formula is:

[0097]

[0098] K a For the entire averaging tube at ΔP a The corresponding theoretical flow coefficient.

[0099] Under conditions of insufficient flow development, and when the flow velocities of the four measured modules are not significantly different, the above simplified calculation formula has a certain degree of accuracy.

[0100] Traditional averaging pitot tubes connect the total pressure measurement orifice and the low-pressure measurement orifice for measurement. The high-pressure average and low-pressure average differ from the arithmetic mean. Under fully developed flow conditions, the accuracy is high when calculated using the flow coefficient. However, in some underdeveloped flow conditions, measurement accuracy is lost. Severe non-uniform flow velocity distribution and asymmetry increase the flow velocity inside the detection tube cavity, resulting in large local pressure losses, and the average pressure deviating from the designed theoretical average. Enhanced flow within the detection tube cavity also reduces averaging performance to varying degrees. In some cases, increased fluid inflow and outflow velocities at the measurement orifices cause the collected pressure values ​​to deviate excessively from the actual total or low pressure values ​​at the measurement orifices.

[0101] Under certain measurement conditions, the static pressure difference at the measurement cross section is too large, and the distribution characteristics may change with the total flow rate. The principle of measuring the average value determines that the static pressure distribution difference affects the measurement accuracy and further affects the establishment of the mathematical relationship between the measured average flow velocity and the actual average flow velocity, which in some cases brings certain difficulties to the numerical correction.

[0102] By adopting the solution of this utility model, fluid flow between the measured modules is completely eliminated, and fluid inflow and outflow at the measuring hole of the detection tube are largely eliminated. Furthermore, its measurement principle determines that the uneven distribution of static pressure in the fluid measurement channel has virtually no impact on measurement accuracy. Under certain working conditions, the above simplified calculation formula significantly improves measurement accuracy compared to traditional averaging pitot tube measurements, and can already meet the accuracy requirements of some engineering measurements. At the same time, adopting the solution of this utility model greatly reduces the risk of dust accumulation inside the detection tube.

[0103] Furthermore, v0 and ΔP can be recorded for the same total flow rate. a The total flow rate can be continuously changed to measure and calculate different values ​​of v0 and ΔP. a The values ​​form a sample database, which can then be used to establish a ΔP-value database through interpolation or fitting. a The function v0 = f(ΔP) is the independent variable and the function value is the function v0 = f(ΔP). a It can be applied to measurements. Experiments can also be conducted under different ρ and viscosity coefficient ν conditions to obtain functions of multiple independent variables for measurement.

[0104] Since this invention measures the arithmetic mean, under the condition that the flow field distribution characteristics of the fluid measurement channel remain unchanged under the same total flow rate, the function v0=f(ΔP) a This will enable rapid and accurate measurements. In practical engineering, in most cases, the flow field distribution characteristics of large-sized ducts and fluid pipelines remain unchanged when the total flow rate is constant. Therefore, this function can achieve rapid and accurate measurement and monitoring, and has significant application value.

[0105] Before measurement, the measuring device can open 8 unified switching valves and close all high-pressure measuring valves and low-pressure measuring valves to make the pressure in each first chamber and second chamber equal, thereby performing zero-point calibration before measurement.

[0106] Obviously, by using multiple L-shaped Pitot tubes or multiple S-shaped Pitot tubes, and optimizing the structural design, and combining them with the same switching valve assembly, the above measurements will achieve a significant improvement in measurement accuracy. The same design applies to Fechheimer type Pitot tubes and other types of averaging pitot tubes.

[0107] Figure 12 is a schematic diagram of the measuring valve assembly in Application Example 2, which is a flow measurement system composed of four diamond-shaped averaging pitot tubes. Each measured module composed of one diamond-shaped averaging pitot tube has four total pressure measuring ports 00h and four low pressure measuring ports 00l. The four average differential pressure measuring components have the following nozzles: the 5th high-pressure nozzle 1205h and the 5th low-pressure nozzle 1205l; the 6th high-pressure nozzle 1206h and the 6th low-pressure nozzle 1206l; the 7th high-pressure nozzle 1207h and the 7th low-pressure nozzle 1207l; and the 8th high-pressure nozzle 1208h and the 8th low-pressure nozzle 1208l.

[0108] Figure 12 is a schematic diagram of the measuring valve group in Application Example 2. The measurement principle is the same as that of the new averaging pitot tube. After measuring the arithmetic mean of the switching valve's action, a simple flow rate calculation can be achieved. Furthermore, under the same operating steps, after achieving a unified differential pressure measurement, a more accurate flow rate measurement can be obtained by calculating the regional differential pressure corresponding to the four measured modules, thus obtaining the function v0=f(ΔP). a It is used in measurement.

[0109] The above process can be summarized as follows: A measurement switching valve is used to switch between unified differential pressure measurement and arithmetic mean measurement of differential pressure in each region; unified differential pressure measurement enables individual measurement of differential pressure in each region; the calculation circuit calculates the average flow velocity related variables of the measurement sub-region based on the differential pressure in each region, thereby obtaining the average flow velocity related variables of the measurement region; a functional relationship is established between the average flow velocity related variables and the arithmetic mean of the measurement region; and this functional relationship is applied to the calculation of the average flow velocity related variables of the measurement region. The average flow velocity related variables include the average flow velocity related variables corresponding to the regional differential pressure of the measured module with only one total pressure measurement point; the average flow velocity related variables include the regional differential pressure.

[0110] In this invention, signal transmission includes transmission via wired or wireless communication; the circuit includes circuits of devices such as remote computers and PLCs.

[0111] The valve assembly and measuring tube components of the aforementioned differential pressure measuring device, including the measuring tube 13, can utilize a thinner measuring tube, allowing for modular design and the fabrication of a miniaturized switching module for ease of use. Furthermore, the measuring switching valve is not limited to an electric valve; a manual valve can also be used. This approach saves costs. Furthermore, mechanical indicating mechanisms can be used to achieve simple monitoring and display of average flow velocity-related variables.

[0112] The module under test can be designed with spaced components to form a measurement sub-channel, as shown in Figure 5 of CN 116295672 A, to further improve measurement accuracy; furthermore, setting a rectifier component in front of the module under test will improve measurement accuracy and stability.

[0113] The flow measurement device can use any differential pressure measuring device of the above form to measure the arithmetic mean of multiple fluid differential pressures. Specifically, it can be summarized as follows: the device includes multiple measured modules and a differential pressure measuring device. The measured modules are set in the measurement area and connected to the differential pressure measuring device through a pressure measurement channel to measure the regional differential pressure. The flow measurement device calculates or displays the average flow velocity related variables of the measurement area based on the regional differential pressure. Its characteristic is that the flow measurement device includes the measurement of the arithmetic mean of at least some regional differential pressures and applies it to the calculation or display of the average flow velocity related variables.

[0114] Furthermore, the measuring diaphragm units in the aforementioned fluid differential pressure measuring device can employ different pressure sensing areas to achieve different weighted arithmetic mean measurements.

[0115] The terms “first,” “second,” and “third” used in this article are for descriptive purposes only and should not be interpreted as indicating or implying relative importance.

[0116] In the description of this utility model, it should be understood that the terms "upper", "lower", "horizontal", "middle", "intermediate", "one side", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0117] Finally, it should be noted that the embodiments described in this article have been described in detail. For those skilled in the art, modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A fluid differential pressure measuring device, characterized in that, The device includes a measuring diaphragm, a push rod, a first cavity, and a second cavity. The measuring diaphragm is positioned between the first and second cavities to form a measuring diaphragm unit, which is used to sense fluid pressure differentials. The push rod passes through and connects to the measuring diaphragm. The first and second cavities have through openings, the edges of which are connected to the push rod. The connecting structure includes a telescopic part, which is used to isolate the measuring pressure space of the corresponding cavity and to displace the push rod. The push rod transmits the axial force generated by the measuring diaphragm unit to a sensor or mechanical indicating mechanism to measure the relevant variables of the fluid pressure differential.

2. The measuring device according to claim 1, characterized in that, The opening and telescopic part have a preset shape and area, so that the effective sensing area of ​​the high-pressure diaphragm unit and the effective sensing area of ​​the low-pressure diaphragm unit are equal.

3. The measuring device according to claim 1, characterized in that, The telescopic part is made of a thin material with a low elastic modulus.

4. The measuring device according to claim 1, characterized in that, The back pressure spaces at both ends of the push rod are configured to have equal pressure.

5. The measuring device according to claim 4, characterized in that, The spaces at both ends of the push rod are configured to be at ambient air pressure and have the same pressure.

6. The measuring device according to claim 4, characterized in that, The spaces at both ends of the push rod are connected by pipes and linked to the same pressure space to achieve the same pressure.

7. The measuring device according to claim 1, characterized in that, The measuring device is configured to perform zero-position calibration and measurement when the push rod is in a vertical position.

8. The measuring device according to claim 1, characterized in that, The measuring device is configured to perform zero-position calibration and measurement when the push rod is in a horizontal state; the measuring device includes an elastic rope to suspend the push rod to achieve centering of the push rod.

9. The measuring device according to claim 1, characterized in that, The push rod is equipped with a limit component for overpressure protection.

10. The measuring device according to claim 1, characterized in that, The measuring device includes multiple measuring diaphragms, which are respectively located between their respective first and second cavities to form multiple measuring diaphragm units; the measuring diaphragms pass through and are connected to the push rod in sequence, and the measuring diaphragm units sense the corresponding fluid pressure difference and generate corresponding axial forces that act together on the push rod.

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