A differential pressure flowmeter

Abstract

The present invention relates to the field of measurement technology, and discloses a differential pressure flowmeter, which includes a base assembly and a measurement assembly. The base assembly includes a base, a throttling element and a base cover. The base has a first fluid passage and a second fluid passage; the throttling element and the base cover are both connected to the base, and the base cover is provided with a first high-pressure pressure tapping hole and a first low-pressure pressure tapping hole; the measurement assembly includes a metal housing, a first sensor wafer, a second sensor wafer, a sensor circuit board and a flowmeter circuit board. The metal housing is connected to the base cover. The first sensor wafer and the second sensor wafer are both connected to the sensor circuit board, and the sensor circuit board is electrically connected to the flowmeter circuit board. The first sensor wafer is a differential pressure sensor wafer, and the second sensor wafer is an absolute pressure sensor wafer or a gauge pressure sensor wafer. This flowmeter integrates the first sensor wafer and the second sensor wafer in the metal housing, which can make the structure of the flowmeter compact, avoid electromagnetic interference and improve the measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of measurement, and in particular to a differential pressure flowmeter. Background Art

[0002] A differential pressure flowmeter is a device that calculates the flow volume of a fluid by using the pressure difference ΔP generated by the fluid before and after flowing through a throttling element. During the measurement process, it is necessary to measure the absolute pressure P of the fluid. P can be directly measured by an absolute pressure sensor, or obtained by adding the current atmospheric pressure Pa after measuring the gauge pressure Pg of the fluid by a gauge pressure sensor (P = Pg + Pa). In this application, the absolute pressure P refers to any one of the above two. After measuring the absolute pressure P, the standard condition flow rate Qn can be calculated by the formula Qn = Q×(Tn / T)×(P / Pn), where Tn is a constant with the unit of Kelvin K, Pn is a constant with the same unit as P, T is the current temperature of the fluid, which is measured by a temperature sensor. Q is the flow rate value that the flowmeter needs to measure, Qn is the final output value of the flowmeter after standard conditions, and the measurement of Q is related to the pressure difference ΔP. Therefore, by measuring ΔP, Q can be measured, and finally Qn can be obtained.

[0003] In the differential pressure flowmeters in the prior art, the differential pressure sensor and the absolute pressure sensor are both independent modules and need to be installed independently, which requires a high level of operation for the installation process. This not only affects the assembly efficiency of the differential pressure flowmeter, but also results in an overly large volume of the differential pressure flowmeter, a too large distance between each module or circuit board, leading to too long connecting wires between them, thereby introducing electromagnetic interference and affecting the measurement accuracy of the differential pressure flowmeter. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a differential pressure flowmeter with a compact structure and a small volume, which can reduce electromagnetic interference and improve measurement accuracy.

[0005] To solve the above problems, the technical solution adopted by the present invention is as follows: A differential pressure flowmeter, comprising: a base assembly, including a base, a throttling element, and a base cover, the base having a first fluid passage and a second fluid passage, the throttling element and the base cover are both connected to the base, the base cover is provided with a first high-pressure pressure tapping hole and a first low-pressure pressure tapping hole, and a measurement assembly, including a metal housing, a first sensor wafer, a second sensor wafer, a sensor circuit board, and a flowmeter circuit board, the metal housing is connected to the base cover, the first sensor wafer and the second sensor wafer are both connected to the sensor circuit board, and the first sensor wafer, the second sensor wafer, and the sensor circuit board are all disposed within the metal housing, the sensor circuit board is electrically connected to the flowmeter circuit board, and the signal ground of the flowmeter circuit board is connected to the metal housing, the first sensor wafer is a differential pressure sensor wafer, and the second sensor wafer is an absolute pressure sensor wafer or a gauge pressure sensor wafer; during measurement, the fluid to be measured can sequentially flow through the first fluid passage, the throttling element, and the second fluid passage, the first high-pressure pressure tapping hole can introduce the absolute pressure of the fluid to the first sensor wafer, and introduce the high pressure of the throttling element to the second sensor wafer, the first low-pressure pressure tapping hole can introduce the absolute pressure of the fluid to the second sensor wafer, and introduce the low pressure of the throttling element to the second sensor wafer.

[0006] Compared with the prior art, the beneficial effects of the above technical solution are as follows: This flowmeter can integrate the first sensor wafer and the second sensor wafer together within the metal housing, which can not only reduce the volume of the flowmeter, making the structure of the flowmeter compact, but also the metal housing can form an electromagnetic shielding cover to reduce the electromagnetic interference received by the first sensor wafer and the second sensor wafer, improving the measurement accuracy; at the same time, the first sensor wafer and the second sensor wafer of this flowmeter are connected to the sensor circuit board and integrated within the metal housing together with the sensor circuit board, and the sensor circuit board is electrically connected to the flowmeter circuit board, without the need to additionally introduce long wires, which can avoid the electromagnetic interference caused by introducing long wires and further improve the measurement accuracy; and the signal ground of the flowmeter circuit board is connected to the metal housing, which can also avoid the signal interference caused by human hands touching the flowmeter circuit board or the metal housing, further improving the measurement accuracy; in addition, the first sensor wafer and the second sensor wafer can be encapsulated within the flowmeter during assembly, which can improve the assembly efficiency of the flowmeter.

[0007] The above-mentioned differential pressure flowmeter, wherein the base is provided with a first installation groove, the throttling element is arranged in the first installation groove and is lower than the first installation groove, there is a flow-through groove between the top surface of the throttling element and the bottom surface of the base cover, the throttling element is further provided with a first communication hole and a second communication hole, and the first fluid passage, the first communication hole, the flow-through groove, the second communication hole and the second fluid passage are sequentially communicated.

[0008] The above-mentioned differential pressure flowmeter, wherein the metal shell includes a first shell and a second shell connected to each other, the first shell is connected to the base, the first shell is provided with a receiving groove, the sensor circuit board is connected to the receiving groove, the second shell is provided with a first wafer groove and a second wafer groove, there is a baffle between the first wafer groove and the second wafer groove, and the first sensor wafer and the second sensor wafer are respectively located in the first wafer groove and the second wafer groove, or the first sensor wafer and the second sensor wafer are respectively located in the second wafer groove and the first wafer groove.

[0009] The above-mentioned differential pressure flowmeter, wherein the bottom wall of the receiving groove is provided with a second high-pressure pressure tapping hole and a second low-pressure pressure tapping hole, the second high-pressure pressure tapping hole corresponds to and communicates with the first high-pressure pressure tapping hole, and the second high-pressure pressure tapping hole communicates with the first wafer groove, the second low-pressure pressure tapping hole corresponds to and communicates with the first low-pressure pressure tapping hole, and the second low-pressure pressure tapping hole communicates with the second wafer groove.

[0010] The above-mentioned differential pressure flowmeter, wherein the bottom wall of the receiving groove is provided with a pressure tapping groove, the pressure tapping groove communicates with the second high-pressure pressure tapping hole and the second low-pressure pressure tapping hole, and the pressure tapping groove can introduce the fluid pressure into the first sensor wafer or the second sensor wafer.

[0011] The above-mentioned differential pressure flowmeter further includes an isolation assembly, the isolation assembly includes an isolation plate, a first pressure diaphragm and a second pressure diaphragm, the isolation plate is connected between the base and the base cover, the first pressure diaphragm and the second pressure diaphragm are connected inside the isolation plate, and the first pressure diaphragm isolates the flow-through groove and the first high-pressure pressure tapping hole, the second pressure diaphragm isolates the flow-through groove and the first low-pressure pressure tapping hole, and liquid oil is filled from the top surface of the first pressure diaphragm to the inside of the first wafer groove, and liquid oil is filled from the top surface of the second pressure diaphragm to the inside of the second wafer groove.

[0012] The differential pressure flowmeter described above, the isolation plate is provided with a second installation groove and a third installation groove, the first pressure diaphragm and the second pressure diaphragm are respectively installed in the second installation groove and the third installation groove, the bottom walls of the second installation groove and the third installation groove are respectively provided with a third communication hole and a fourth communication hole, during measurement, the fluid to be measured can act on the first pressure diaphragm and the second pressure diaphragm through the third communication hole and the fourth communication hole respectively.

[0013] The differential pressure flowmeter described above, a gap is reserved between the first pressure diaphragm and the bottom wall of the second installation groove, and a gap is reserved between the second pressure diaphragm and the third installation groove. During measurement, the fluid to be measured is filled between the bottom surface of the first pressure diaphragm and the bottom wall of the second installation groove, and the fluid to be measured is filled between the bottom surface of the second pressure diaphragm and the bottom wall of the third installation groove.

[0014] The differential pressure flowmeter described above, two groups of first pressing rings are arranged in the second installation groove, the first pressure diaphragm is welded between the two groups of first pressing rings, two groups of second pressing rings are arranged in the third installation groove, and the second pressure diaphragm is welded between the two groups of second pressing rings.

[0015] The differential pressure flowmeter described above, the outer peripheral side wall of the first pressing ring is welded to the inner peripheral side wall of the second installation groove, and the second pressing ring is welded to the inner peripheral side wall of the third installation groove.

[0016] The differential pressure flowmeter described above, the base cover is provided with a fourth installation groove, the bottom surface of the first housing is connected to the bottom wall of the fourth installation groove, the bottom wall of the fourth installation groove is provided with a high-pressure end oil pressure compensation groove and a low-pressure end oil pressure compensation groove, the high-pressure end oil pressure compensation groove communicates with the first high-pressure pressure guiding hole and the second high-pressure pressure guiding hole, the low-pressure end oil pressure compensation groove communicates with the first low-pressure pressure guiding hole and the second low-pressure pressure guiding hole, and the first high-pressure pressure guiding hole and the first low-pressure pressure guiding hole can communicate with each other through the fourth installation groove.

[0017] The differential pressure flowmeter described above, the second housing is provided with a high-pressure oil filling hole and a low-pressure oil filling hole, and the high-pressure oil filling hole and the low-pressure oil filling hole communicate with the first wafer groove and the second wafer groove respectively.

[0018] The differential pressure flowmeter described above, a first sealing ring is arranged between the second high-pressure pressure guiding hole and the first high-pressure pressure guiding hole, and a second sealing ring is arranged between the second low-pressure pressure guiding hole and the first low-pressure pressure guiding hole.

[0019] The present invention will be further described in detail below with reference to the drawings and specific embodiments. Description of the Drawings

[0020] Figure 1Structural schematic diagram of the differential pressure flowmeter according to Embodiment 1 of the present invention;

[0021] Figure 2 is Figure 1 exploded view of the differential pressure flowmeter shown;

[0022] Figure 3 is Figure 1 cross-sectional view of a partial structure of the differential pressure flowmeter shown;

[0023] Figure 4 is Figure 1 structural schematic diagram of the first housing in the differential pressure flowmeter shown;

[0024] Figure 5 is Figure 1 structural schematic diagram of the second housing in the differential pressure flowmeter shown;

[0025] Figure 6 is Figure 1 structural schematic diagram of the base cover in the differential pressure flowmeter shown;

[0026] Figure 7 Structural schematic diagram of the differential pressure flowmeter according to Embodiment 2 of the present invention;

[0027] Figure 8 is Figure 7 exploded view of the differential pressure flowmeter shown;

[0028] Figure 9 is Figure 7 structural schematic diagram of the isolation component in the differential pressure flowmeter shown;

[0029] Figure 10 is Figure 9 cross-sectional view of the isolation component shown;

[0030] Figure 11 is Figure 7 structural schematic diagram of the base cover in the differential pressure flowmeter shown;

[0031] Figure 12 Structural schematic diagram of an existing oil-filled pressure sensor described in Embodiment 2 of the present invention;

[0032] Figure 13 is Figure 12 cross-sectional view of the oil-filled pressure sensor shown in

[0033] Figure 14 is Figure 7 high-pressure pressure guiding path diagram of the differential pressure flowmeter shown;

[0034] Figure 15 is Figure 7Schematic diagram of the low-pressure pressure guiding path and the absolute pressure guiding path of the differential pressure flowmeter shown;

[0035] Figure 16 is Figure 7 Partial cross-sectional view of the differential pressure flowmeter shown when placed upright;

[0036] Figure 17 is Figure 7 Partial cross-sectional view of the differential pressure flowmeter shown when placed sideways.

[0037] Explanation of the reference numerals in the attached drawings:

[0038] 100 Base assembly, 110 Base, 111 First fluid passage, 112 Second fluid passage, 113 First mounting groove, 1131 Flow-through groove, 120 Throttle element, 121 First communication hole, 122 Second communication hole, 130 Base cover, 131 First high-pressure pressure guiding hole, 132 First low-pressure pressure guiding hole, 133 Fourth mounting groove, 134 High-pressure end oil pressure compensation groove, 135 Low-pressure end oil pressure compensation groove;

[0039] 200 Measuring assembly, 210 Metal housing, 211 First housing, 2111 Accommodating groove, 2112 Second high-pressure pressure guiding hole, 2113 Second low-pressure pressure guiding hole, 2114 Pressure guiding groove, 212 Second housing, 2121 First wafer groove, 2122 Second wafer groove, 2123 Baffle, 2124 High-pressure oil filling hole, 2125 Low-pressure oil filling hole, 220 First sensor wafer, 230 Second sensor wafer, 240 Sensor circuit board, 250 Flowmeter circuit board, 260 First sealing ring, 270 Second sealing ring;

[0040] 300 Isolation assembly, 310 Isolation plate, 311 Second mounting groove, 312 Third mounting groove, 313 Third communication hole, 314 Fourth communication hole, 320 First pressure diaphragm, 330 Second pressure diaphragm, 340 First compression ring, 350 Second compression ring;

[0041] 400 Oil-filled pressure sensor, 410 Low-pressure diaphragm, 420 High-pressure diaphragm, 430 Pressure sensor diaphragm. Detailed implementation manners

[0042] The embodiments of the present invention will be described in detail below:

[0043] Embodiment 1

[0044] Refer to Figures 1 to 6, an embodiment of the present invention provides a differential pressure flowmeter, which includes a base assembly 100 and a measurement assembly 200. The base assembly 100 includes a base 110, a throttling element 120, and a base cover 130. The base 110 has a first fluid passage 111 and a second fluid passage 112, and the flow directions of the first fluid passage 111 and the second fluid passage 112 are the same. A temperature sensor is provided inside the base 110 for measuring the temperature of the fluid. Both the throttling element 120 and the base cover 130 are connected to the base 110. The base cover 130 is provided with a first high-pressure pressure tapping hole 131 and a first low-pressure pressure tapping hole 132. The axial directions of the first high-pressure pressure tapping hole 131 and the first low-pressure pressure tapping hole 132 are parallel to each other and perpendicular to the flow directions of the first fluid passage 111 and the second fluid passage 112. When the fluid flows through the throttling element 120, due to the viscosity of the fluid, there will be a pressure difference before and after the fluid flows through the throttling element 120.

[0045] The measurement assembly 200 includes a metal housing 210, a first sensor wafer 220, a second sensor wafer 230, a sensor circuit board 240, and a flowmeter circuit board 250. The metal housing 210 is connected to the base cover 130. Both the first sensor wafer 220 and the second sensor wafer 230 are connected to the sensor circuit board 240, and the first sensor wafer 220, the second sensor wafer 230, and the sensor circuit board 240 are all arranged inside the metal housing 210. The flowmeter circuit board 250 is fixed to the outside of the metal housing 210 by screws. The sensor circuit board 240 is electrically connected to the flowmeter circuit board 250, and the signal ground of the flowmeter circuit board 250 is connected to the metal housing 210. The first sensor wafer 220 is a differential pressure sensor wafer, and the second sensor wafer 230 is an absolute pressure sensor wafer or a gauge pressure sensor wafer.

[0046] The first sensor wafer 220 is used to measure the pressure difference before and after the fluid flows through the throttling element 120, and the second sensor wafer 230 is used to measure the absolute pressure of the fluid. It should be noted that the absolute pressure of the fluid mentioned here can be directly measured by an absolute pressure sensor, or can be obtained by measuring the gauge pressure Pg of the fluid with a gauge pressure sensor and then adding the current atmospheric pressure Pa (P = Pg + Pa). That is, when the second sensor wafer 230 is an absolute pressure sensor wafer, the pressure measured by the second sensor wafer 230 is the true absolute pressure of the fluid. When the second sensor wafer 230 is a gauge pressure sensor wafer, the pressure measured by the second sensor wafer 230 is the gauge pressure of the fluid, and the true absolute pressure of the fluid can be obtained by adding the current atmospheric pressure value to the gauge pressure of the fluid.

[0047] During measurement, the fluid to be measured can flow through the first fluid passage 111, the throttling element 120, and the second fluid passage 112 in sequence. The first high-pressure pressure tapping hole 131 can introduce the absolute pressure of the fluid to the first sensor wafer 220 and introduce the high pressure of the throttling element 120 to the second sensor wafer 230. The first low-pressure pressure tapping hole 132 can introduce the absolute pressure of the fluid to the second sensor wafer 230 and introduce the low pressure of the throttling element 120 to the second sensor wafer 230. It should be noted that in the above description, both the first high-pressure pressure tapping hole 131 and the first low-pressure pressure tapping hole 132 can introduce the absolute pressure of the fluid to the second sensor wafer 230. Specifically, the second sensor wafer 230 can choose to be installed at any one of the first high-pressure pressure tapping hole 131 or the first low-pressure pressure tapping hole 132, and the first sensor wafer 220 is installed at the other of these two hole positions.

[0048] For example, when the second sensor wafer 230 chooses to be installed at the first high-pressure pressure tapping hole 131, then during measurement, the high pressure of the fluid is introduced to the first sensor wafer 220 by the first high-pressure pressure tapping hole 131, the low pressure of the fluid is introduced to the first sensor wafer 220 by the first low-pressure pressure tapping hole 132, and the absolute pressure of the fluid is introduced to the second sensor wafer 230 by the first high-pressure pressure tapping hole 131. According to the measured absolute pressure and differential pressure, the flow rate of the fluid can be calculated. Another example is when the second sensor wafer 230 chooses to be installed at the first low-pressure pressure tapping hole 132. Then during measurement, the high pressure of the fluid is introduced to the first sensor wafer 220 by the first high-pressure pressure tapping hole 131, the low pressure of the fluid is introduced to the first sensor wafer 220 by the first low-pressure pressure tapping hole 132, and the absolute pressure of the fluid is introduced to the second sensor wafer 230 by the first low-pressure pressure tapping hole 132. According to the measured absolute pressure and differential pressure, the flow rate of the fluid can be calculated.

[0049] This flowmeter can integrate the first sensor wafer 220 and the second sensor wafer 230 together within the metal housing 210. It can not only reduce the volume of the flowmeter, making the structure of the flowmeter compact, but also the metal housing 210 can form an electromagnetic shielding cover to reduce the electromagnetic interference received by the first sensor wafer 220 and the second sensor wafer 230, thereby improving the measurement accuracy. At the same time, the first sensor wafer 220 and the second sensor wafer 230 of this flowmeter are connected to the sensor circuit board 240 and integrated within the metal housing 210 together with the sensor circuit board 240. The sensor circuit board 240 is electrically connected to the flowmeter circuit board 250, eliminating the need for additional long wires to be connected. Therefore, the electromagnetic interference introduced by the long wires can be avoided, further improving the measurement accuracy. In addition, the first sensor wafer 220 and the second sensor wafer 230 can be encapsulated within the flowmeter during assembly, improving the assembly efficiency of the flowmeter. The flowmeter circuit board 250 is fixed to the outside of the metal housing 210 by screws, enabling the signal ground of the flowmeter circuit board 250 to be connected to the metal housing 210, eliminating the signal interference generated when a person touches the metal housing 210.

[0050] Specifically, referring to Figure 2 and Figure 3 Base 110 is provided with a first installation groove 113. The throttling element 120 is disposed within the first installation groove 113 and is lower than the first installation groove 113. Specifically, the thickness of the throttling element 120 is less than the depth of the first installation groove 113, and the bottom surface of the throttling element 120 is connected to the bottom wall of the first installation groove 113. The thickness of the throttling element 120 refers to the distance between the top surface and the bottom surface of the throttling element 120. There is a flow-through groove 1131 between the top surface of the throttling element 120 and the bottom surface of the base cover 130. Specifically, the flow-through groove 1131 is a part of the first installation groove 113. The throttling element 120 is further provided with a first communication hole 121 and a second communication hole 122. The first fluid passage 111, the first communication hole 121, the flow-through groove 1131, the second communication hole 122, and the second fluid passage 112 are sequentially communicated. During measurement, the fluid enters from within the first fluid passage 111, passes through the first communication hole 121 into the flow-through groove 1131, then enters the second fluid passage 112 via the second communication hole 122, and finally flows out of the flowmeter. When the fluid flows from the first communication hole 121 through the second communication hole 122, that is, when the fluid flows through the throttling element 120, based on the pressure difference of the fluid before and after flowing through the throttling element 120 and the measured absolute pressure of the fluid, the flow rate of the fluid can be calculated. Specifically, the throttling element 120 can be a laminar flow element, a sonic nozzle, an orifice plate, a baffle 2123, or other detection elements designed according to the principle of the throttling device.

[0051] Specifically, referring to Figure 4 and Figure 5, the metal housing 210 includes a first housing 211 and a second housing 212 that are connected to each other. Both the first housing 211 and the second housing 212 are made of metal materials. The first housing 211 is connected to the base 110. An accommodation groove 2111 is provided on the inner bottom wall of the first housing 211, and the sensor circuit board 240 is connected in the accommodation groove 2111. The second housing 212 is provided with a first wafer groove 2121 and a second wafer groove 2122. In the normal use state of the flowmeter, the first housing 211 and the second housing 212 are covered and connected to each other. At this time, the accommodation groove 2111, the first wafer groove 2121, and the second wafer groove 2122 are not connected to the external environment. At this time, it can be ensured that both the first sensor wafer 220 and the second sensor wafer 230 are located in an electromagnetic shielding environment, and the interference of external electromagnetic signals can be avoided. A baffle 2123 is provided between the first wafer groove 2121 and the second wafer groove 2122. The first sensor wafer 220 and the second sensor wafer 230 are respectively located in the first wafer groove 2121 and the second wafer groove 2122, or the first sensor wafer 220 and the second sensor wafer 230 are respectively located in the second wafer groove 2122 and the first wafer groove 2121. The first sensor wafer 220 and the second sensor wafer 230 can be glued to the sensor circuit board 240.

[0052] Further, with continued reference to Figure 4, a second high-pressure pressure tapping hole 2112 and a second low-pressure pressure tapping hole 2113 are opened on the bottom wall of the accommodation groove 2111. The position of the second high-pressure pressure tapping hole 2112 corresponds to and communicates with that of the first high-pressure pressure tapping hole 131, and the second high-pressure pressure tapping hole 2112 communicates with the first wafer groove 2121. The position of the second low-pressure pressure tapping hole 2113 corresponds to and communicates with that of the first low-pressure pressure tapping hole 132, and the second low-pressure pressure tapping hole 2113 communicates with the second wafer groove 2122. When the fluid flows through the throttling element 120, the first high-pressure pressure tapping hole 131 and the second high-pressure pressure tapping hole 2112 together introduce the high pressure of the throttling element 120 to the first sensor wafer 220, and the first low-pressure pressure tapping hole 132 and the second low-pressure pressure tapping hole 2113 together introduce the low pressure of the throttling element 120 to the second sensor wafer 230, and introduce the absolute pressure of the fluid to the second sensor wafer 230. Specifically, a pressure tapping groove 2114 is opened on the bottom wall of the accommodation groove 2111. The pressure tapping groove 2114 communicates with the second high-pressure pressure tapping hole 2112 and the second low-pressure pressure tapping hole 2113, and the pressure tapping groove 2114 can introduce the fluid pressure to the first sensor wafer 220 or the second sensor wafer 230. The pore walls of the first high-pressure pressure tapping hole 131, the second high-pressure pressure tapping hole 2112, the first low-pressure pressure tapping hole 132 and the second low-pressure pressure tapping hole 2113 are all sealed. Specifically, a first sealing ring 260 can be arranged between the second high-pressure pressure tapping hole 2112 and the first high-pressure pressure tapping hole 131, and a second sealing ring 270 can be arranged between the second low-pressure pressure tapping hole 2113 and the first low-pressure pressure tapping hole 132. Both the first sealing ring 260 and the second sealing ring 270 can be sealing parts such as O-ring washers. Specifically, two circular grooves can be opened on the bottom wall of the first installation groove 113, and the first high-pressure pressure tapping hole 131 and the first low-pressure pressure tapping hole 132 are respectively opened on the bottom walls of these two circular grooves. After the side walls of the circular grooves are sealed, the first sealing ring 260 and the second sealing ring 270 are installed.

[0053] Specifically, pads are provided on both the flowmeter circuit board 250 and the sensor circuit board 240. After the first housing 211 and the sensor circuit board 240 are installed, the flowmeter circuit board 250 is installed on the outside of the first housing 211. At the same time, the pads between the flowmeter circuit board 250 and the sensor circuit board 240 are connected by tin wire. The distance between the flowmeter circuit board 250 and the sensor circuit board 240 is very close, so no additional wires are needed, which can play a role in anti-electromagnetic interference. Then, the flowmeter circuit board 250 and the metal housing 210 are locked and connected by screws. The screws can not only lock the flowmeter circuit board 250, but also connect the signal ground on the flowmeter circuit board 250 to the metal housing 210, which can eliminate the signal interference generated when the human body touches the metal housing 210.

[0054] Embodiment 2

[0055] Refer toFigure 7 and Figure 8 For Embodiment 2 of the present invention, another differential pressure flowmeter is provided. The difference between this differential pressure flowmeter and the differential pressure flowmeter in Embodiment 1 is that the differential pressure flowmeter in this Embodiment 2 further includes an isolation assembly 300. The isolation assembly 300 includes an isolation plate 310, a first pressure diaphragm 320, and a second pressure diaphragm 330. The isolation plate 310 is connected between the base 110 and the base cover 130. The first pressure diaphragm 320 and the second pressure diaphragm 330 are connected inside the isolation plate 310. The first pressure diaphragm 320 isolates the flow channel 1131 and the first high-pressure pressure tapping hole 131, and the second pressure diaphragm 330 isolates the flow channel 1131 and the first low-pressure pressure tapping hole 132. Liquid oil is filled in the space from the top surface of the first pressure diaphragm 320 to the first wafer groove 2121, and liquid oil is filled in the space from the top surface of the second pressure diaphragm 330 to the second wafer groove 2122.

[0056] In the differential pressure flowmeter of Embodiment 1, when measuring the fluid flow rate, the fluid is in direct contact with the bottom wall of the sensor circuit board 240. Therefore, this kind of differential pressure flowmeter is usually used to measure non-corrosive fluids. For corrosive fluids, it is necessary to isolate the fluid from the sensor. Therefore, Embodiment 2 of the present invention provides a differential pressure flowmeter that can be used to measure corrosive fluids. In this Embodiment 2, the flowmeter uses the first pressure diaphragm 320 to isolate the flow channel 1131 and the first high-pressure pressure tapping hole 131, and uses the second pressure diaphragm 330 to isolate the flow channel 1131 and the first low-pressure pressure tapping hole 132. When the fluid flows through the throttling element 120, the first pressure diaphragm 320 and the second pressure diaphragm 330 sense the pressure of the fluid and transmit the pressure to the first sensor wafer 220 and the second sensor wafer 230 through the liquid oil, so as to measure the pressure change of the fluid. The first pressure diaphragm 320 and the second pressure diaphragm 330 can prevent the fluid from directly contacting the flowmeter circuit board 240. Specifically, the isolation plate 310, the first pressure diaphragm 320, and the second pressure diaphragm 330 are all made of 316L stainless steel material, and the obtained isolation plate 310, the first pressure diaphragm 320, and the second pressure diaphragm 330 have strong corrosion resistance.

[0057] Specifically, referring to Figure 9 and Figure 10, the partition plate 310 is provided with a second installation groove 311 and a third installation groove 312. The first pressure diaphragm 320 and the second pressure diaphragm 330 are respectively installed in the second installation groove 311 and the third installation groove 312. The bottom walls of the second installation groove 311 and the third installation groove 312 are respectively provided with a third communication hole 313 and a fourth communication hole 314. During measurement, the fluid to be measured can act on the first pressure diaphragm 320 and the second pressure diaphragm 330 through the third communication hole 313 and the fourth communication hole 314 respectively. A gap is reserved between the bottom surface of the first pressure diaphragm 320 and the bottom wall of the second installation groove 311, and a gap is reserved between the bottom surface of the second pressure diaphragm 330 and the bottom wall of the third installation groove 312. During measurement, the fluid to be measured is filled between the bottom surface of the first pressure diaphragm 320 and the bottom wall of the second installation groove 311, and the fluid to be measured is filled between the bottom surface of the second pressure diaphragm 330 and the bottom wall of the third installation groove 312.

[0058] Specifically, two groups of first pressing rings 340 are provided in the second installation groove 311, and the first pressure diaphragm 320 is welded between the two groups of first pressing rings 340. Two groups of second pressing rings 350 are provided in the third installation groove 312, and the second pressure diaphragm 330 is welded between the two groups of second pressing rings 350. Specifically, the outer peripheral side wall of the first pressing ring 340 is welded to the inner peripheral side wall of the second installation groove 311, and the outer peripheral side wall of the second pressing ring 350 is welded to the inner peripheral side wall of the third installation groove 312. After welding, it can be ensured that a gap is reserved between the bottom surface of the first pressure diaphragm 320 and the bottom wall of the second installation groove 311. At the same time, it can also be ensured that a gap is reserved between the bottom surface of the second pressure diaphragm 330 and the bottom wall of the third installation groove 312. The outer peripheral side wall of the first pressing ring 340 is closely attached to the inner peripheral side wall of the second installation groove 311, and the outer peripheral side wall of the second pressing ring 350 is closely attached to the inner peripheral side wall of the third installation groove 312 to achieve sealing. Of course, sealing treatment can also be carried out on the inner peripheral side walls of the second installation groove 311 and the third installation groove 312 in advance.

[0059] Specifically, referring to Figure 8 , the second housing 212 is provided with a high-pressure oil filling hole 2124 and a low-pressure oil filling hole 2125. The high-pressure oil filling hole 2124 and the low-pressure oil filling hole 2125 are respectively communicated with the first wafer groove 2121 and the second wafer groove 2122. After the flowmeter is assembled, liquid oil is filled through the high-pressure oil filling hole 2124 and the low-pressure oil filling hole 2125, and finally the high-pressure oil filling hole 2124 and the low-pressure oil filling hole 2125 are closed with pins to complete the encapsulation of the flowmeter. In the embodiment of the present invention, in order to facilitate seeing the structures of various components, connecting parts such as pins in the figure have been hidden. Further, referring to Figure 11, the base cover 130 is provided with a fourth installation groove 133. The bottom surface of the first housing 211 is connected to the bottom wall of the fourth installation groove 133. The bottom wall of the fourth installation groove 133 is provided with a high-pressure end oil pressure compensation groove 134 and a low-pressure end oil pressure compensation groove 135. The high-pressure end oil pressure compensation groove 134 communicates with the first high-pressure pressure tapping hole 131 and the second high-pressure pressure tapping hole 2112. The low-pressure end oil pressure compensation groove 135 communicates with the first low-pressure pressure tapping hole 132 and the second low-pressure pressure tapping hole 2113. And the first high-pressure pressure tapping hole 131 and the first low-pressure pressure tapping hole 132 can communicate with each other through the fourth installation groove 133.

[0060] It should be noted that there are also some oil-filled pressure sensors 400 on the market at present, which can avoid the fluid directly contacting and corroding the sensor. However, this kind of oil-filled pressure sensor 400 is affected by the weight of the oil and will generate a large zero-point error. In addition, this kind of oil-filled pressure sensor 400 can only be used to measure the pressure difference. In the existing flowmeter, an additional sensor for measuring the absolute pressure of the fluid needs to be purchased, which is not conducive to the packaging of the flowmeter and the miniaturization of the flowmeter. As Figure 12 shown, this is one of the oil-filled pressure sensors 400 on the market. Its two ends are respectively provided with a low-pressure diaphragm 410 and a high-pressure diaphragm 420, and a pressure sensor diaphragm 430 is arranged inside. In the figure, h1 is the oil filling height at the high-pressure end, and h2 is the oil filling height at the low-pressure end. When the oil-filled pressure sensor 400 is placed upright, the pressure P of the oil-filled pressure sensor 400 = SGρgh1. As Figure 13 shown, when the oil-filled pressure sensor 400 is placed upside down, the pressure P of the oil-filled pressure sensor 400 = -SGρgh2. SG is the specific gravity of the oil, ρ is the density of water, and g is the acceleration of gravity. SG, ρ, and g are fixed values, while h1 and h2 are different. Therefore, when the placement direction of the oil-filled pressure sensor 400 is different, the measured zero-point pressure P is different. Especially in the case of a micro pressure difference within 10 kPa, the zero-point error generated by the self-weight of the oil will occupy a relatively large proportion of the range. For example, generally, Δh = h2 = 20 mm, SG is 1.065, then ΔP = 1.065 * 1000 * 9.8 * 0.02 = 208.74 pa. If the range of the oil-filled pressure sensor 400 is 10 kPa, then the zero-point error generated when placed upside down accounts for 208.74 / 10000 = 2% of the full range. The relatively large zero-point error affects the measurement accuracy.

[0061] Referring to Figures 14 to 17 , the flowmeter in the second embodiment of the present invention can make the structure of the flowmeter compact while well reducing the zero-point error generated due to different placement directions caused by the weight of the oil.

[0062] The following will explain why the zero error caused by the oil weight can be reduced after the first sensor wafer 220 and the second sensor wafer 230 are encapsulated in this flowmeter:

[0063] It should be noted that in the second embodiment, the first sensor wafer 220 is installed at the hole position of the first high-pressure pressure tapping hole 131, and the second sensor wafer 230 is installed at the hole position of the first low-pressure pressure tapping hole 132. As Figure 14 shown, the high pressure induced by the liquid oil can be transmitted to the first sensor wafer 220 through the first high-pressure pressure tapping hole 131. As Figure 15 shown, the low pressure induced by the liquid oil can be transmitted to the first sensor wafer 220 via the first low-pressure pressure tapping hole 132 and the pressure tapping groove 2114. The liquid oil can also transmit the absolute pressure of the fluid to the second sensor wafer 230 through the first low-pressure pressure tapping hole 132.

[0064] As Figure 16 shown, this figure is a partial cross-sectional view of the flowmeter in the upright position in the second embodiment. The generated pressure difference ΔP = SGρgh1–SGρgh2 = (h1 - h2)*SGρg, where Δh = h1 - h2 is the diaphragm thickness of the first sensor wafer 220. In the second embodiment, Δh < 0.1mm. When Δh = 0.1mm, calculating Δp = 1.065 * 1000 * 9.8 * 0.0001 = 1.043pa. Therefore, it can be considered that when it is upright, ΔP < 1.043pa, which is much smaller than 208.74pa in the prior art. Similarly, when the flowmeter is placed upside down, Δh is also the diaphragm thickness of the first sensor wafer 220. Therefore, ΔP < 1.043pa, which is much smaller than 208.74pa in the prior art.

[0065] As Figure 17 shown, this figure is a partial cross-sectional view of the flowmeter in the side position in the second embodiment. Under the action of the oil pressure compensation groove 134 at the high-pressure end, Δh is the distance from the highest level of the oil to the highest point of the oil pressure compensation groove 134 at the high-pressure end. In the second embodiment, at this time, Δh = 3mm, that is, when the flowmeter is placed in the side position, the distance from the highest level of the oil to the highest point of the oil pressure compensation groove 134 at the high-pressure end is 3mm. The zero-point pressure difference ΔP = SGρgΔh = 1.065 * 1000 * 9.8 * 0.003 = 31.3pa, which is much smaller than 208.74pa in the prior art. Similarly, when the flowmeter is placed in the side position towards the other side, Δh is also 3mm, and the zero-point pressure difference ΔP = SGρgΔh = 1.065 * 1000 * 9.8 * 0.003 = 31.3pa. As can be seen from the above, the zero error of this flowmeter caused by the self-weight of the oil is very small, and the first sensor wafer 220 and the second sensor wafer 230 can be encapsulated together, making the structure of the flowmeter compact and facilitating assembly.

[0066] It should be noted that in the description of the present invention, when it comes to the description of directions, such as the directions or positional relationships indicated by up, down, front, back, left, right, etc., they are all based on the directions or positional relationships shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed or operated in a specific direction, and should not be construed as a limitation to the present invention.

[0067] In the description of the present invention, the meaning of "several" is one or more, the meaning of "multiple" is two or more, "greater than", "less than", "exceeding", etc. are understood as not including the number itself, and "above", "below", "within", etc. are understood as including the number itself. If there is a description of "first" or "second", etc., it is only for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0068] In the description of the present invention, unless otherwise clearly defined, words such as "set", "installed", "connected", etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0069] The above embodiments are only the preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention belong to the scope of protection required by the present invention.

Claims

1. A differential pressure flowmeter, characterized in that, Comprising: A base assembly (100), including a base (110), a throttling element (120) and a base cover (130). The base (110) has a first fluid passage (111) and a second fluid passage (112). Both the throttling element (120) and the base cover (130) are connected to the base (110). The base cover (130) is provided with a first high-pressure pressure tapping hole (131) and a first low-pressure pressure tapping hole (132), and A measurement assembly (200), including a metal housing (210), a first sensor wafer (220), a second sensor wafer (230), a sensor circuit board (240) and a flowmeter circuit board (250). The metal housing (210) is connected to the base cover (130). Both the first sensor wafer (220) and the second sensor wafer (230) are connected to the sensor circuit board (240), and the first sensor wafer (220), the second sensor wafer (230) and the sensor circuit board (240) are all arranged inside the metal housing (210). The sensor circuit board (240) is electrically connected to the flowmeter circuit board (250), and the signal ground of the flowmeter circuit board (250) is connected to the metal housing (210). The first sensor wafer (220) is a differential pressure sensor wafer, and the second sensor wafer (230) is an absolute pressure sensor wafer or a gauge pressure sensor wafer; During measurement, the fluid to be measured can flow through the first fluid passage (111), the throttling element (120) and the second fluid passage (112) in sequence. The first high-pressure pressure tapping hole (131) can introduce the absolute pressure of the fluid to the first sensor wafer (220), and introduce the high pressure of the throttling element (120) to the second sensor wafer (230). The first low-pressure pressure tapping hole (132) can introduce the absolute pressure of the fluid to the second sensor wafer (230), and introduce the low pressure of the throttling element (120) to the second sensor wafer (230); Wherein, the metal housing (210) includes a first housing (211) and a second housing (212) connected to each other. The first housing (211) is connected to the base (110). The first housing (211) is provided with a receiving groove (2111). The bottom wall of the receiving groove (2111) is provided with a second high-pressure pressure tapping hole (2112) and a second low-pressure pressure tapping hole (2113). The second high-pressure pressure tapping hole (2112) corresponds to the position of the first high-pressure pressure tapping hole (131) and is communicated with each other. The second low-pressure pressure tapping hole (2113) corresponds to the position of the first low-pressure pressure tapping hole (132) and is communicated with each other; The base cover (130) is provided with a fourth installation groove (133). The bottom surface of the first housing (211) is connected to the bottom wall of the fourth installation groove (133). The bottom wall of the fourth installation groove (133) is provided with a high-pressure end oil pressure compensation groove (134) and a low-pressure end oil pressure compensation groove (135). The high-pressure end oil pressure compensation groove (134) communicates with the first high-pressure pressure guiding hole (131) and the second high-pressure pressure guiding hole (2112). The low-pressure end oil pressure compensation groove (135) communicates with the first low-pressure pressure guiding hole (132) and the second low-pressure pressure guiding hole (2113). And the first high-pressure pressure guiding hole (131) and the first low-pressure pressure guiding hole (132) can communicate with each other through the fourth installation groove (133).

2. The differential pressure flowmeter according to claim 1, wherein The base (110) is provided with a first installation groove (113). The throttling element (120) is arranged in the first installation groove (113) and is lower than the first installation groove (113). There is a flow-through groove (1131) between the top surface of the throttling element (120) and the bottom surface of the base cover (130). The throttling element (120) is also provided with a first communication hole (121) and a second communication hole (122). The first fluid passage (111), the first communication hole (121), the flow-through groove (1131), the second communication hole (122), and the second fluid passage (112) are communicated in sequence.

3. The differential pressure flowmeter according to claim 2, wherein The sensor circuit board (240) is connected in the receiving groove (2111). The second housing (212) is provided with a first wafer groove (2121) and a second wafer groove (2122). A baffle (2123) is provided between the first wafer groove (2121) and the second wafer groove (2122). The first sensor wafer (220) and the second sensor wafer (230) are respectively located in the first wafer groove (2121) and the second wafer groove (2122), or the first sensor wafer (220) and the second sensor wafer (230) are respectively located in the second wafer groove (2122) and the first wafer groove (2121).

4. The differential pressure flowmeter according to claim 3, wherein The second high-pressure pressure guiding hole (2112) communicates with the first wafer groove (2121). The second low-pressure pressure guiding hole (2113) communicates with the second wafer groove (2122).

5. The differential pressure flowmeter according to claim 4, wherein, The bottom wall of the receiving groove (2111) is provided with a pressure guiding groove (2114). The pressure guiding groove (2114) communicates with the second high-pressure pressure guiding hole (2112) and the second low-pressure pressure guiding hole (2113). The pressure guiding groove (2114) can introduce fluid pressure into the first sensor wafer (220) or the second sensor wafer (230).

6. The differential pressure flowmeter according to claim 4, characterized in that It further includes an isolation component (300), and the isolation component (300) includes an isolation plate (310), a first pressure diaphragm (320) and a second pressure diaphragm (330). The isolation plate (310) is connected between the base (110) and the base cover (130). The first pressure diaphragm (320) and the second pressure diaphragm (330) are connected inside the isolation plate (310). The first pressure diaphragm (320) isolates the flow channel (1131) and the first high-pressure pressure-introducing hole (131), and the second pressure diaphragm (330) isolates the flow channel (1131) and the first low-pressure pressure-introducing hole (132). Liquid oil is filled from the top surface of the first pressure diaphragm (320) to the first wafer groove (2121), and liquid oil is filled from the top surface of the second pressure diaphragm (330) to the second wafer groove (2122).

7. The differential pressure flowmeter according to claim 6, wherein The isolation plate (310) is provided with a second installation groove (311) and a third installation groove (312). The first pressure diaphragm (320) and the second pressure diaphragm (330) are respectively installed in the second installation groove (311) and the third installation groove (312). A third communication hole (313) and a fourth communication hole (314) are respectively provided on the bottom walls of the second installation groove (311) and the third installation groove (312). During measurement, the fluid to be measured can act on the first pressure diaphragm (320) and the second pressure diaphragm (330) through the third communication hole (313) and the fourth communication hole (314) respectively.

8. The differential pressure flowmeter according to claim 7, wherein, A gap is reserved between the bottom surface of the first pressure diaphragm (320) and the bottom wall of the second installation groove (311), and a gap is reserved between the bottom surface of the second pressure diaphragm (330) and the bottom wall of the third installation groove (312). During measurement, the fluid to be measured is filled between the bottom surface of the first pressure diaphragm (320) and the bottom wall of the second installation groove (311), and the fluid to be measured is filled between the bottom surface of the second pressure diaphragm (330) and the bottom wall of the third installation groove (312).

9. The differential pressure flowmeter according to claim 8, wherein, Two groups of first pressure rings (340) are provided in the second installation groove (311), and the first pressure diaphragm (320) is welded between the two groups of first pressure rings (340). Two groups of second pressure rings (350) are provided in the third installation groove (312), and the second pressure diaphragm (330) is welded between the two groups of second pressure rings (350).

10. The differential pressure flowmeter according to claim 9, characterized in that, The outer peripheral side wall of the first pressure ring (340) is welded to the inner peripheral side wall of the second installation groove (311), and the outer peripheral side wall of the second pressure ring (350) is welded to the inner peripheral side wall of the third installation groove (312).

11. The differential pressure flowmeter according to claim 6, characterized in that, The second housing (212) is provided with a high-pressure oil filling hole (2124) and a low-pressure oil filling hole (2125), and the high-pressure oil filling hole (2124) and the low-pressure oil filling hole (2125) are respectively communicated with the first wafer groove (2121) and the second wafer groove (2122).

12. The differential pressure flowmeter according to claim 4, characterized in that, A first sealing ring (260) is provided between the second high-pressure pressure tapping hole (2112) and the first high-pressure pressure tapping hole (131), and a second sealing ring (270) is provided between the second low-pressure pressure tapping hole (2113) and the first low-pressure pressure tapping hole (132).

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