Micro-pressure sensor calibration device and method

Abstract

The invention discloses a micro-pressure sensor calibration device and method, and belongs to the technical field of micro-differential pressure sensor calibration, and the device comprises an integrated box body, a precise micro-volume adjusting mechanism, a return-to-zero sealing assembly and a connection interface unit. The interior of the box body is divided into a standard chamber and an adjusting chamber with constant volumes through a partition plate; the precise micro-volume adjusting mechanism is integrated on one side of the adjusting cavity, and a spiral micrometer head is used for driving a precise piston rod to change the volume of the cavity. And the zeroing sealing assembly adopts a precise stop valve to control the connection and disconnection between the cavity and the atmosphere. According to the invention, the Boyle's law is utilized, the theoretical differential pressure is accurately calculated by reading the mechanical displacement of the spiral micrometer head, and high-precision calibration can be realized without depending on a power supply and a standard differential pressure gauge; meanwhile, a standard meter interface is reserved, and a laboratory verification mode is compatible. The device has the advantages of being compact in structure, passive, portable, intuitive in operation, high in precision and the like, and solves the problem that the micro differential pressure sensor cannot be accurately calibrated on site in a field power-free environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro pressure difference sensor calibration, in particular to a micro pressure sensor calibration device and method. BACKGROUND

[0002] Micro pressure difference sensors are widely used in aerospace, meteorological monitoring, industrial process control, and heating, ventilation and air conditioning fields. Due to their extremely small measurement range (usually a few pascals to a few thousand pascals), they are easily affected by environmental temperature, atmospheric pressure fluctuations, and installation location, so they need to be calibrated regularly for zero point and sensitivity.

[0003] Existing micro pressure difference calibration devices are mainly divided into two categories:

[0004] The first type is a comparison device based on a high-precision standard pressure difference meter. For example, Chinese patent CN102778332B discloses a "micro pressure difference generation and calibration device", which uses two independent cylindrical main cylinders as the pressure difference source, adjusts the volume of the cylinder to generate pressure difference through a precision lead screw, and uses the measurement value of the standard pressure difference meter as the reference for calibration. Although this device isolates environmental interference and has high precision, it uses a separate double-cylinder structure, which is large in size and not portable; and it must rely on a high-precision standard pressure difference meter and a computer system for synchronous acquisition, making it difficult to meet the needs of field work in a power-free environment.

[0005] The second type is a pressure generation device based on a complex electronic control system. For example, Chinese patent CN111693211A discloses a "micro pressure difference calibrator", which uses an electromagnet to drive a moving part sealed by a magnetic liquid to generate a micro pressure difference, and cooperates with an upper computer for automatic control. Although this device achieves automation, it has a complex structure and relies heavily on power supply and upper computer control, and the maintenance cost of consumables such as magnetic liquid is high, so it is also not suitable for portable field applications.

[0006] In addition, in some simple field calibrations, a medical syringe is often used to push gas to generate pressure. However, manual operation of the syringe cannot accurately control the volume change, and the heat from the operator's hand is directly transferred to the gas, causing adiabatic compression temperature rise, which seriously affects the measurement accuracy of the pascal (Pa) level micro pressure difference.

[0007] Therefore, there is an urgent need for a portable micro pressure difference sensor calibration device that is compact in structure, does not require power, does not rely completely on a standard meter, and can overcome thermal interference and achieve high-precision volume adjustment. SUMMARY

[0008] The technical scheme of the present application provides a solution significantly different from the prior art, mainly a micro-pressure sensor calibration device and method, to overcome the shortcomings of the prior art, such as large size, dependence on power supply and standard table, and low precision of simple devices.

[0009] The technical scheme adopted by the present application to solve the above technical problems is:

[0010] A micro-pressure sensor calibration device comprises:

[0011] The box body is integrally designed, and the inside of the box body is provided with a standard chamber and an adjusting chamber which are isolated from each other;

[0012] The precise micro-volume adjusting mechanism is connected to one side of the integrally designed box body and located on the side of the adjusting chamber, and is used for adjusting the air pressure of the adjusting chamber; the precise micro-volume adjusting mechanism comprises an adjusting cylinder in communication with the adjusting chamber and a screw micrometer head used for driving the adjusting cylinder, the adjusting cylinder is provided with a precise piston rod, and the screw micrometer head is used for pushing and pulling the precise piston rod to move;

[0013] The zero-return sealing assembly comprises precise stop valves in communication with the standard chamber and the adjusting chamber respectively, and is used for controlling the communication and isolation between the chambers in the box body and the outside atmosphere;

[0014] The connecting interface unit comprises sensor connecting ports in communication with the standard chamber and the adjusting chamber respectively, and is used for connecting the micro-pressure difference sensor to be measured through a pipeline.

[0015] Further, the box body is provided with a partition plate, which divides the inside of the box body into the standard chamber and the adjusting chamber.

[0016] Further, the outer wall surface of the box body is wrapped with a layer of heat insulation material, which is used for isolating the influence of the outside temperature;

[0017] And / or, the knob of the screw micrometer head is provided with a heat insulation sleeve, which is used for blocking the conduction of the heat of the hands of the operator to the adjusting mechanism and the inside of the chamber.

[0018] Further, the position of the box body through which the adjusting cylinder passes is provided with a dynamic sealing ring.

[0019] Further, the fixed sleeve of the screw micrometer head is fixedly connected with the adjusting cylinder or the box body, and the movable shaft of the screw micrometer head is abutted or fixedly connected with the end portion of the precise piston rod.

[0020] Further, the screw micrometer head is provided with a mechanical scale, and the resolution of the mechanical scale is higher than or equal to 0.01 mm.

[0021] Further, the connecting interface unit further comprises a standard table interface respectively communicating with the standard chamber and the adjusting chamber, and the standard table interface is provided with a sealing plug; when the sealing plug is removed and a standard differential pressure gauge is connected, the device enters a standard calibration mode.

[0022] Further, the connecting interface unit adopts a quick plug, and the connected pipeline adopts a hard capillary tube with a low expansion coefficient to minimize the volume error caused by pipeline deformation.

[0023] Further, the adjusting cylinder is embeddedly inserted into the adjusting chamber, and in the initial state, the piston at the end of the precision piston rod is flush with the inner wall of the box.

[0024] The application also provides a micro-pressure sensor calibration method, which adopts the micro-pressure sensor calibration device to calibrate, and comprises the following steps:

[0025] S1. Connecting step: connecting two pressure tapping openings of a micro-pressure difference sensor to be measured to the standard chamber and the adjusting chamber of the device through pipelines respectively;

[0026] S2. Zeroing step: opening two precision shut-off valves to make the interiors of the two chambers communicate with the atmosphere, and after the pressure inside and outside the system is balanced, closing the precision shut-off valves, at this time, the system is in an initial closed state;

[0027] S3. Pressure building step: rotating the knob of the screw micrometer head to drive the precision piston rod to advance by a specific distance L to change the air pressure of the adjusting chamber;

[0028] S4. Thermal equilibrium step: stopping operation and keeping still for a preset time (for example, 30-60 seconds), waiting for the heat generated due to gas compression to dissipate until the temperature in the chamber returns to the ambient temperature;

[0029] S5. Calculation and calibration step: reading the displacement reading of the screw micrometer head, calculating the theoretical absolute pressure in the adjusting chamber by using the Boyle's law and the pressure difference relative to the standard chamber , and comparing with the reading of the sensor to be measured; wherein, in the calculation process, a dead volume correction formula is adopted:

[0030]

[0031]

[0032] In the formula, P0 is the initial atmospheric pressure;

[0033] is the volume of the piston,

[0034] is the volume of the piston, , A is the piston cross-sectional area;

[0035] V is the total initial volume of the system, defined as: ;

[0036] V is the fixed volume of the body of the adjustment chamber;

[0037] V is the volume of the connecting pipeline;

[0038] V is the volume of the internal air chamber of the sensor to be measured.

[0039] Compared with the prior art, the beneficial effects of the present application are:

[0040] (1) High-precision passive calibration: the present application uses a screw micrometer head with mechanical scale as the driving mechanism, replacing the traditional manual or electric motor. By using the high resolution (0.01mm level) of the screw micrometer mechanism, precise volume control at microliter level can be achieved without power supply, and high-precision passive calibration is realized by combining with the Boyle's law calculation method.

[0041] (2) Excellent thermal stability: in view of the problem that micro-pressure difference measurement is sensitive to temperature, the present application sets a layer of thermal insulation material on the outer wall of the box, and sets a thermal insulation sleeve at the operating knob, effectively blocking the heat conduction of the environment and the body temperature of the operator; at the same time, the "thermal equilibrium" step is introduced in the calibration method, which eliminates the adiabatic temperature rise error caused by gas compression, and significantly improves the measurement accuracy.

[0042] (3) Compact and portable structure: compared with the separated double-cylinder structure in the prior art, the present application adopts an integrated double-chamber design, which is more compact and solid, and is easy to carry to the field for use.

[0043] (4) Dual-mode compatible design: the present application can work independently without standard table through "calculation method", and also reserves standard table interface, which can be connected in parallel with high-precision standard pressure difference meter for "standard method" verification, taking into account the flexibility of field operation and the rigor of laboratory value traceability.

[0044] (5) System error correction: the present application introduces correction of the "dead volume" of the connecting pipeline and the internal cavity of the sensor in the calculation method, further eliminating the inherent error of the system and ensuring the accuracy of value transmission.

[0045] The present application will be explained in detail in combination with the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a structural schematic diagram of an embodiment of the present application;

[0047] Figure 2 for Figure 1 Enlarged structural diagram of region A in the middle;

[0048] Figure 3 This is a schematic diagram of another embodiment of the present invention.

[0049] 1. Housing; 11. Standard chamber; 12. Adjustment chamber; 2. Partition; 3. Insulation material layer; 4. Micrometer screw head; 41. Movable shaft; 42. Insulation sleeve; 5. Adjustment cylinder; 51. Dynamic sealing ring; 52. Precision piston rod; 6. Precision shut-off valve; 61. Standard chamber shut-off valve; 62. Adjustment chamber shut-off valve; 7. Sensor connection port; 8. Standard meter interface. Detailed Implementation

[0050] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below with reference to the accompanying drawings, which illustrate several embodiments of the present invention. However, the present invention can be implemented in different forms and is not limited to the embodiments described in the text. Rather, these embodiments are provided to make the disclosure of the present invention more thorough and complete.

[0051] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly associated with those skilled in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0053] Example: Please refer to the appendix for details. Figure 1 - Appendix Figure 2 This embodiment provides a micro-pressure sensor calibration device, which mainly consists of an integrated housing 1, a precision micro-volume adjustment mechanism, a zeroing sealing component, and a connection interface unit.

[0054] 1. Integrated cabinet

[0055] The preferred material is stainless steel or hard aluminum alloy with a low coefficient of thermal expansion to ensure volume stability under pressure changes. Inside the enclosure, a precision-machined partition 2 strictly divides the internal space into two independent chambers: a standard chamber 11 on the left and an adjustment chamber 12 on the right.

[0056] In the preferred design, through precision machining control, the initial body volume of the standard chamber 11 and the regulating chamber 12 are equal.

[0057] To eliminate the influence of ambient temperature fluctuations and operator body temperature on measurement accuracy, the outer surface of the enclosure 1 is entirely covered with a layer of insulating material 3, such as aerogel felt or polyurethane foam.

[0058] 2. Precision micro-volume adjustment mechanism

[0059] It is installed on one side of the housing 1 and communicates with the adjustment chamber 12. The mechanism includes a micrometer screw head 4 and an adjustment cylinder 5.

[0060] Adjusting cylinder 5: Its port is connected to the adjusting chamber 12, and a dynamic sealing ring 51 (such as a fluororubber O-ring) is provided at the position on the housing 1 through which the adjusting cylinder 5 passes; the adjusting cylinder 5 is provided with a precision piston rod 52, and the piston at the end of the precision piston rod 52 is designed with high airtightness between it and the inner wall of the adjusting cylinder 5 to ensure that there is no gas leakage when the piston moves.

[0061] In some embodiments, the adjusting cylinder 5 may be a syringe (needle).

[0062] The micrometer screw head 4 employs a high-precision micrometer head structure. Its fixed sleeve is installed at the end of the adjusting cylinder 5 furthest from its own port. The movable shaft 41 of the micrometer screw head 4 abuts against or is fixedly connected to the end of the precision piston rod 52, and the movable shaft 41 and the precision piston rod 52 are coaxially arranged. The micrometer screw head 4 is equipped with a mechanical scale, with a preferred resolution of 0.01 mm or higher. When the knob of the micrometer screw head 4 is rotated, the movable shaft 41 of the micrometer screw head 4 pushes and pulls the precision piston rod 52 in a linear motion within the adjusting cylinder 5 to achieve pressure adjustment.

[0063] To prevent heat from the hand from being transferred to the device through the knob, the knob of the micrometer head 4 is specially covered with an insulating sleeve 42, such as made of bakelite or engineering plastic.

[0064] 3. Zeroing sealing assembly

[0065] Precision shut-off valves 6, namely standard chamber shut-off valve 61 and regulating chamber shut-off valve 62, are respectively installed at the top of the standard chamber 11 and the regulating chamber 12. The shut-off valves preferably adopt a needle valve structure to achieve smooth opening and closing of the air circuit and avoid pressure shock caused by the instantaneous opening and closing of the ball valve.

[0066] 4. Connection Interface Unit

[0067] The side of the standard chamber 11 and the adjusting chamber 12 is respectively provided with a sensor connection port 7 for connecting the micro pressure difference sensor to be tested. In order to reduce the "dead volume" error introduced by the connecting pipeline, the connection port adopts a quick plug joint, and a hard capillary tube with a low expansion coefficient (such as a PU tube or a stainless steel tube with an inner diameter of φ2mm) is used as a connecting gas path.

[0068] In some optimized designs, in order to be compatible with the laboratory high-precision calibration requirements, the side of the standard chamber 11 and the adjusting chamber 12 is also reserved with a standard table interface 8, which is usually sealed by a sealing plug.

[0069] The calibration method based on the above-mentioned micro pressure sensor calibration device comprises the following steps:

[0070] Step 1: System connection and parameter confirmation

[0071] The high pressure end and the low pressure end of the micro pressure difference sensor to be tested are respectively connected to the sensor connection ports 7 of the adjusting chamber 12 and the standard chamber 11 through the connecting pipelines.

[0072] Before measurement, the total initial volume parameter of the system is confirmed. For the adjusting chamber 12 side, the total initial volume is defined as:

[0073]

[0074] Wherein:

[0075] V0: The fixed volume of the adjusting chamber 12 (determined by the machining size, which is a known constant); At the same time, the effective volume of the adjusting cylinder 5 connected to the adjusting chamber 12 is considered (determined according to the scale value corresponding to the initial position of the piston in the adjusting cylinder 5, which is a known constant).

[0076] Vp: The volume of the connecting pipeline (calculated according to the length and inner diameter of the pipeline, which is a known constant);

[0077] Vs: The volume of the internal gas chamber of the sensor to be tested (usually provided by the sensor manufacturer, for a micro pressure difference sensor, the value is usually small, but it cannot be ignored in high-precision calculation).

[0078] Step 2: System zeroing

[0079] The two precision stop valves 6 are opened counterclockwise, so that the standard chamber 11 and the adjusting chamber 12 are simultaneously connected with the outside atmosphere. After standing for a few seconds, when the internal gas pressure of the system and the ambient atmospheric pressure are completely balanced, the two precision stop valves 6 are closed clockwise. At this time, the system is in a closed state, and the initial pressure of the two chambers is , the pressure difference is zero.

[0080] Step 3: Precise pressure building

[0081] Hold the hand-held heat shield 43 and slowly rotate the knob of the screw micrometer head 4, so that the movable shaft 41 moves slowly, pushing the precise piston rod 52 to advance to the port of the adjusting cylinder 5. Observe the mechanical scale of the screw micrometer head 4 to make the precise piston rod 52 advance a certain distance , for example, 5.00 mm.

[0082] At this time, since the adjusting cylinder 5 is in communication with the adjusting chamber 12, the volume of the gas in the adjusting chamber 12 is compressed, and the change is :

[0083]

[0084] wherein, is the cross-sectional area of the inner wall of the adjusting cylinder 5, which is a known constant.

[0085] Step 4: Thermal equilibrium waiting

[0086] Stop operating and keep the device stationary for 30-60 seconds.

[0087] Principle explanation: The gas will be adiabatically heated at the moment of compression, causing the pressure reading to be temporarily high. The waiting is to allow the gas in the chamber to exchange heat through the metal box wall, so that the gas temperature returns to the ambient temperature , ensuring that the subsequent calculation meets the "isothermal" premise of the Boyle's law.

[0088] Step 5: Pressure difference calculation and calibration

[0089] After the sensor reading is stable, according to the Boyle's law , the theoretical absolute pressure in the adjusting chamber 12 is calculated :

[0090]

[0091] Then the theoretical pressure difference value of the adjusting chamber 12 relative to the standard chamber 11 (which remains unchanged) is :

[0092]

[0093] The operator records the display value of the sensor to be tested at this time, and compares it with the theoretical pressure difference value calculated above. If there is a deviation, the sensor needs to be calibrated.

[0094] By changing the advancing distance of the piston rod (For example, by advancing 1mm, 2mm, 3mm... in sequence), a series of standard differential pressure values ​​can be obtained, thereby completing the linearity calibration of the sensor across its entire range.

[0095] The above method can be applied in field environments without power supply, calibrating micro-differential pressure sensors through a "computational method." This process specifically introduces a "thermal equilibrium" step and a "dead volume correction" algorithm to address the insufficient accuracy of traditional simple devices.

[0096] In another embodiment, such as Figure 3 As shown, the adjusting cylinder 5 is embedded in the adjusting chamber 12, and a dynamic sealing ring 51 (such as a fluororubber O-ring) is provided on the housing 1 at the position through which the adjusting cylinder 5 passes. In the initial state, the piston at the end of the precision piston rod 52 is flush with the inner wall of the housing 1. With this setting, the effective volume of the adjusting cylinder 5 communicating with the adjusting chamber 12 is directly located within the adjusting chamber 12, eliminating the need to separately calculate the effective volume of the adjusting cylinder 5, making calculation more convenient.

[0097] In another embodiment, the device also features a "laboratory standard mode": when used in a laboratory setting, the sealing plug on the standard gauge interface 8 can be removed, and a high-precision digital standard differential pressure gauge can be connected in parallel. In this mode, the micrometer head 4 functions solely as a high-precision "pressure generator," and the operator does not need to perform the aforementioned formula calculations but directly reads the value from the standard differential pressure gauge as the true value to calibrate the sensor under test. This mode combines the advantages of the device's precise pressure generation with the direct traceability of the standard gauge.

[0098] The present invention has been described by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvement made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, shall be within the protection scope of the present invention.

Claims

1. A micro-pressure sensor calibration apparatus, characterized by: The application relates to a micro-pressure differential sensor calibration device. The device comprises: a box (1) with an integrated design, which is internally provided with a standard chamber (11) and an adjusting chamber (12) which are isolated from each other; a precise micro-volume adjusting mechanism which is connected to one side of the integrated box (1) and is located at the side of the adjusting chamber (12) and is used for adjusting the air pressure of the adjusting chamber (12); the precise micro-volume adjusting mechanism comprises an adjusting cylinder (5) which is communicated with the adjusting chamber (12) and a screw micrometer head (4) which is used for driving the adjusting cylinder (5), the adjusting cylinder (5) is internally provided with a precise piston rod (52), and the screw micrometer head (4) is used for pushing and pulling the precise piston rod (52) to move; a zero-return sealing assembly which comprises precise stop valves (6) which are respectively communicated with the standard chamber (11) and the adjusting chamber (12) and is used for controlling the communication and isolation between the chambers in the box (1) and the atmosphere; 2. The micro-pressure sensor calibration device of claim 1, wherein: a connecting interface unit which comprises sensor connecting ports (7) which are respectively communicated with the standard chamber (11) and the adjusting chamber (12) and is used for connecting the micro-pressure differential sensor to be detected through pipelines.

3. The micro-pressure sensor calibration device of claim 1, wherein: The box (1) is internally provided with a partition plate (2) which divides the chamber in the box (1) into the standard chamber (11) and the adjusting chamber (12). The outer wall surface of the box (1) is wrapped with a heat insulation material layer (3).

4. The micro-pressure sensor calibration device of claim 1, wherein: And / or, an insulating sleeve (43) is arranged at the knob of the screw micrometer head (4).

5. The micro-pressure sensor calibration device of claim 1, wherein: The box (1) is provided with a dynamic sealing ring (51) at the position through which the adjusting cylinder (5) passes.

6. The micro-pressure sensor calibration device of claim 1, wherein: The fixed sleeve of the screw micrometer head (4) is fixedly connected with the adjusting cylinder (5) or the box (1), and the movable shaft (41) of the screw micrometer head (4) is abutted or fixedly connected with the end of the precise piston rod (52).

7. The micro-pressure sensor calibration device of claim 1, wherein: The screw micrometer head (4) is provided with a mechanical scale, the resolution of which is higher than or equal to 0.01 mm.

8. The micro-pressure sensor calibration device of claim 7, wherein: The connecting interface unit further comprises standard meter interfaces (8) which are respectively communicated with the standard chamber (11) and the adjusting chamber (12), and the standard meter interfaces (8) are provided with sealing plugs.

9. The micro-pressure sensor calibration device of claim 1, wherein: The connecting interface unit adopts quick plug-in connectors, and the pipelines connected are made of hard capillary tubes with low expansion coefficients.

10. A method for calibrating a micro-pressure sensor using the micro-pressure sensor calibration device according to any one of claims 1-9, characterized in that: The adjusting cylinder (5) is embeddedly inserted into the adjusting chamber (12), and in the initial state, the piston at the end of the precise piston rod (52) is flush with the inner wall of the box (1). The device comprises the following steps: S1. a connecting step: two pressure taking openings of the micro-pressure differential sensor to be detected are connected to the standard chamber (11) and the adjusting chamber (12) of the device through pipelines respectively; S2. a zero-return step: two precise stop valves (6) are opened, so that the interiors of the two chambers are communicated with the atmosphere, after the pressure balance between the system and the atmosphere, the precise stop valves (6) are closed, and at this moment, the system is in the initial state of being closed; S3. a pressure building step: the knob of the screw micrometer head (4) is rotated, the precise piston rod (52) is driven to advance a specific distance L, and the air pressure of the adjusting chamber (12) is changed; S5. Calculation and calibration step: reading the displacement reading of the screw micrometer head (4), calculating the theoretical absolute pressure in the conditioning chamber (12) using Boyle's law and the differential pressure with respect to the standard chamber (11) and comparing it with the reading of the sensor to be tested; where, in the calculation, a dead volume correction formula is used: ； ； S4. a heat balance step: the operation is stopped and the system is kept still for a preset time, heat generated due to air compression is dissipated, and the temperature in the chamber is recovered to the ambient temperature; in the formula: initial atmospheric pressure; to push the volume, , A is the piston cross-sectional area; Total initial volume of the system, defined as: ; to regulate the fixed volume of the body of the chamber (12); to connect the volume of the pipe; V is the volume of the internal chamber of the sensor under test.

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