Portable quasi-static pressure calibration device

Abstract

The invention relates to a portable quasi-static pressure calibration device. Comprising a quick-opening valve mechanism, a standard pressure transmitter and a gas storage bottle, the quick-opening valve mechanism comprises a mounting block, a high-pressure cavity is formed in the mounting block, a standard pressure monitoring hole is formed in the side wall of the high-pressure cavity, the high-pressure cavity is connected with a gas storage bottle, a stepped hole used for being detachably connected with a calibrated sensor mounting structure is formed in one side of the mounting block, and a low-pressure cavity is formed in the end, away from the side edge, of the stepped hole. An exhaust hole parallel to the axis of the stepped hole is formed in the upper part of the stepped hole in the mounting block; a connecting cavity communicated with the high-pressure cavity and the low-pressure cavity is further formed in the mounting block and comprises a high-pressure cavity communicating hole parallel to the axis of the exhaust hole and a communicating locking mechanism mounting hole perpendicular to the axis of the exhaust hole; a pressing rod spring type communication locking mechanism is arranged in the communication locking mechanism mounting hole, and communication between the high-pressure cavity and the low-pressure cavity is achieved by pressing a pressing rod. The device is clear in principle and easy to operate, and the defects that a traditional drop / pendulum bob calibration system is complex in installation and tedious in maintenance are overcome.

Description

Technical Field

[0001] The invention belongs to the field of sensor measurement and calibration, and in particular relates to a portable quasi-static pressure calibration device. Background Art

[0002] At present, the mainstream quasi-static pressure calibration method is the drop / pendulum calibration device, which acts on the piston assembly at the top of the pressure-generating cylinder through a freely falling hammer head. The piston squeezes the pressure-transmitting medium in the cylinder to form a semi-sine pressure signal, thereby performing a quasi-static calibration of the sensor. Although the drop / pendulum calibration device has been widely used, this type of device has the following problems: 1) The drop / pendulum calibration device is usually large and difficult to move; 2) In order to ensure the stability of the calibration excitation source, the drop / pendulum calibration device needs to clean the cylinder before each test, resulting in a long test cycle. The above problems make the drop / pendulum calibration device unable to be used in field working environments where sensors need to be calibrated frequently. Summary of the invention

[0003] The object of the present invention is to provide a portable quasi-static pressure calibration device.

[0004] The technical solution for achieving the purpose of the present invention is: a portable quasi-static pressure calibration device, including a quick-opening valve mechanism, a standard pressure transmitter and a gas storage bottle;

[0005] The quick-opening valve mechanism includes a mounting block, a high-pressure chamber is arranged in the mounting block, a standard pressure monitoring hole is arranged on the side wall of the high-pressure chamber, the high-pressure chamber is connected to the gas cylinder through the gas cylinder connecting hole on the mounting block, a stepped hole is opened on one side of the mounting block, the stepped hole is used for detachably connecting the calibrated sensor mounting structure, the end of the stepped hole away from the side is a low-pressure chamber, the calibrated sensor mounted on the calibrated sensor mounting structure is located in the low-pressure chamber, and an exhaust hole parallel to the axis of the stepped hole is arranged on the upper part of the mounting block at the step hole; a connecting chamber connecting the high-pressure chamber and the low-pressure chamber is also provided on the mounting block, the connecting chamber includes a high-pressure chamber connecting hole parallel to the axis of the exhaust hole and a connecting locking mechanism mounting hole perpendicular to the axis of the exhaust hole; a pressure rod spring-type connecting locking mechanism is arranged in the connecting locking mechanism mounting hole, and the pressure rod is pressed to realize the connection between the high-pressure chamber and the low-pressure chamber, thereby realizing measurement, and the pressure rod is released to realize the sealing of the high-pressure chamber connecting hole, and the gas in the low-pressure chamber is discharged through the exhaust hole, thereby realizing the recovery of the calibration device.

[0006] Further, the pressure rod spring type communication locking mechanism includes a pressure rod, a pressure rod spring, a sealing ring, a sealing ball, a sealing block and a sealing spring;

[0007] The pressure rod comprises a pressure rod head and a pressure rod body, and an inclined step for limiting the sealing ball and an annular protrusion for limiting the pressure rod spring and the pressure rod body are arranged in the mounting hole of the connecting locking mechanism; the diameter of the pressure rod head is larger than the diameter of the pressure rod body, a pressure rod spring is arranged between the pressure rod head and the annular protrusion, and the pressure rod spring is sleeved outside the upper half of the pressure rod body; two sealing ring annular protrusions are arranged in the middle of the pressure rod body, and an annular groove for installing the sealing ring is formed between the two sealing ring annular protrusions, and the sealing ring realizes the sealing between the pressure rod body and the inner wall of the mounting hole of the connecting locking mechanism; a sealing spring is arranged at the bottom of the mounting hole of the connecting locking mechanism, and the sealing block comprises a cylindrical end and a groove section connected to the sealing ball and having a diameter larger than the cylindrical section, and the sealing spring is sleeved outside the cylindrical section. When the pressure rod head is loosened, under the action of the sealing spring, the sealing block and the sealing ball move upward, and the sealing ball is stuck at the inclined step to realize the sealing of the high-pressure chamber.

[0008] Furthermore, the sealing ball is made of elastic material.

[0009] Furthermore, the sealing ball is made of rubber, polytetrafluoroethylene or polyethylene.

[0010] Furthermore, it also includes a PID adjustment module. A high-pressure chamber air inlet is also provided on the mounting block. The high-pressure chamber air inlet is connected to an external high-pressure gas source through a proportional valve and a switch valve. The proportional valve is connected to the PID adjustment module. The switch valve is used to disconnect the air-tightening of the quick-opening valve mechanism behind the proportional valve. The standard pressure transmitter obtains the pressure change in the high-pressure chamber in real time, and converts it into a voltage value and transmits it to the PID adjustment module. The PID adjustment module performs PID control on the inflation and pressurization process of the proportional valve according to the output voltage value of the standard pressure transmitter.

[0011] Furthermore, the sum of the volumes V1 of the high-pressure chamber and the gas storage bottle and the volume V2 of the low-pressure chamber satisfy that the pressure source change ΔP≤0.1% after i tests.

[0012] Furthermore, the section with the largest diameter of the mounting structure of the calibrated sensor is threadedly connected to the corresponding section of the stepped hole.

[0013] Furthermore, the calibrated sensor installation structure is provided with various specifications, and different calibrated sensor installation structures are selected according to different types of calibrated sensors.

[0014] Compared with the prior art, the present invention has the following significant advantages:

[0015] 1) The device has good portability. Compared with quasi-static calibration systems such as drop / pendulum, this device is small in size and easy to carry to the field environment. After a single external gas source is inflated, only the quick-opening valve mechanism, gas storage cylinder, standard pressure transmitter and calibration pressure sensor core module are retained, and multiple rounds of quasi-static calibration tests can still be carried out independently;

[0016] 2) The device has good repeatability. After a single external gas source inflation, the device can independently conduct 4 to 5 rounds of quasi-static calibration tests (with a 2L gas cylinder), while ensuring that the pressure change of the calibration source is less than 0.1%; and by matching standard gas cylinders of different specifications, the number of quasi-static tests that the device can conduct independently can be effectively increased;

[0017] 3) Through the pressure control module (standard pressure sensor, PID adjustment module, proportional valve), the pressure of the excitation source in the quick-opening valve mechanism can be accurately controlled to meet the calibration requirements of pressure sensors of various ranges.

[0018] 4) The equipment has clear principles and is easy to operate, improving the shortcomings of traditional drop / pendulum calibration systems, which are complex to install and maintain. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the calibration device of the present invention.

[0020] Figure 2 The invention relates to a quick-opening valve mechanism.

[0021] Figure 3 The flow state of high-pressure gas in the quick-opening valve mechanism when the pressure rod is pressed down and popped up; (a) is when the pressure rod is pressed down, and (b) is when the pressure rod is popped up.

[0022] Figure 4 This is the measured pressure curve of the calibrated piezoelectric sensor of the present invention.

[0023] Description of reference numerals:

[0024] 1-air inlet hole, 2-standard pressure monitoring hole, 3-gas cylinder connection hole, 4-high pressure chamber, 5-pressure rod, 6-sealing ring, 7-exhaust hole, 8-low pressure chamber, 9-sealing ball, 10-sealing spring, 11-calibrated sensor mounting structure. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0026] like Figure 1 As shown, a portable quasi-static pressure calibration device includes a proportional valve, a quick-opening valve mechanism, a standard pressure transmitter, a PID adjustment module, a gas storage cylinder, and a calibrated pressure sensor.

[0027] The front end of the proportional valve is connected to an external high-pressure gas source, and the rear end is connected to the quick-opening valve mechanism through a switch valve. The proportional valve can adjust the air flow rate through the proportional valve in real time according to the control signal sent by the PID adjustment module, thereby realizing the internal pressure control function of the quick-opening valve mechanism.

[0028] The standard pressure transmitter is installed in conjunction with the quick-opening valve mechanism through threads; the standard pressure transmitter can obtain the pressure changes in the high-pressure chamber of the quick-opening valve mechanism in real time, and convert it into a voltage value and transmit it to the PID control module through a low-noise cable.

[0029] The PID adjustment module performs PID control on the proportional valve inflation pressure according to the output voltage value of the standard pressure transmitter. The control process has the characteristics of fast response, small overlimit, and high stable state accuracy. It has obvious control effect, especially for large pure lag objects that are difficult to control with conventional PID.

[0030] like Figure 2 As shown, the quick-opening valve mechanism mainly consists of an air inlet 1, a standard pressure monitoring hole 2, a gas cylinder connecting hole 3, a high-pressure chamber 4, a pressure rod 5, a sealing ring 6, an exhaust hole 7, a low-pressure chamber 8, a sealing ball 9, a sealing spring 10, and a calibrated sensor mounting structure 11. The air inlet, the standard pressure monitoring hole, and the gas cylinder connecting hole are all provided with mounting threads, wherein the air inlet is connected to the proportional valve, the standard pressure monitoring hole is connected to the standard pressure transmitter, and the gas cylinder connecting hole is connected to the gas cylinder;

[0031] The quick-opening valve mechanism, during the inflation process of the device, the pressure rod 5 is in an upward pop-up state (such as Figure 3 b), at this time, the sealing ball 9 is lifted by the spring mechanism 10, so that the high-pressure chamber 4 is isolated from the low-pressure chamber 8, and the low-pressure chamber 8 is connected to the exhaust hole 7;

[0032] Quick-opening valve mechanism, when conducting a calibration test, the experimenter presses the pressure rod 5 down to a predetermined position (such as Figure 3 a), at this time, the sealing ring 6 blocks the exhaust hole 7, so that the low-pressure chamber 8 is isolated from the external atmospheric environment; the sealing ball 9 no longer isolates the high-pressure chamber 4 from the low-pressure chamber 8, and the gas in the high-pressure chamber 4 quickly flows into the low-pressure chamber 8, causing the air pressure in the low-pressure chamber 8 to rise rapidly and act on the surface of the sensitive element of the sensor to be calibrated, thereby realizing the quasi-static calibration of the sensor.

[0033] Quick-opening valve mechanism. After a round of experimental results, the experimenter no longer constrains the position of the pressure rod 5, and the pressure rod 5 rebounds. At this time, the sealing ball 9 is lifted up by the spring mechanism 10 again, so that the high-pressure chamber 4 is isolated from the low-pressure chamber 8; at the same time, the low-pressure chamber 8 is connected to the exhaust hole 7, and the high-pressure gas in the low-pressure chamber 8 is discharged to restore the atmospheric pressure;

[0034] The high-pressure chamber and the low-pressure chamber are designed to be cylindrical in overall structure to improve the pressure resistance and facilitate machining;

[0035] The sealing ball 9 is made of elastic material to ensure the sealing effect. The material can be rubber, polytetrafluoroethylene or polyethylene;

[0036] The gas storage bottle is connected to the high-pressure chamber of the quick-opening valve mechanism through a thread, and the gas storage bottle is used to increase the volume of the high-pressure chamber in the quick-opening valve mechanism, so as to improve the stability of the calibration source in the high-pressure chamber of the calibration device after multiple rounds of tests;

[0037] The pressure stability indicators in the high-pressure chamber during the device calibration test were analyzed, and the dimensional requirements for the quick-opening valve mechanism and gas storage cylinder were proposed. For static calibration, GB / T 5478-2015 "Pressure Sensor Performance Test Method" stipulates that the error of the standard pressure source of the calibration system should not exceed 1 / 2 or 1 / 3 of the allowable error of the tested sensor; for dynamic calibration, JJG 624-2005 "Dynamic Pressure Sensor" stipulates that the step amplitude uncertainty of the dynamic pressure source of the quick-opening valve should be <1% (K=2); At present, for quasi-static calibration, there is no national or industry standard that proposes relevant indicators for the stability of the pressure source. According to the requirements for pressure sources in GB / T 5478-2015, JJG 624-2005, and JJG 152-2018 standards, combined with the actual functions of the single inflation and multiple rounds of tests of this device, the following indicators are proposed for the pressure stability of the high-pressure chamber of the device: After the external gas source inflates the high-pressure chamber of the quick-opening valve mechanism and the gas storage bottle to the predetermined pressure, the device can carry out 4 to 5 rounds of calibration experiments on the premise of disconnecting the external high-pressure gas source, and ensure that the loading pressure value changes no more than 0.1%;

[0038] In order to achieve the target of loading pressure value variation not exceeding 0.1% in 4 to 5 rounds of experiments, it is necessary to analyze and calculate the volume of the low-pressure chamber 8, high-pressure chamber 4 structure and gas storage bottle in the quick-opening valve mechanism; assuming that the high-pressure chamber of the quick-opening valve mechanism and the gas storage bottle meet the ideal gas equation after pressurization, then after the external gas source inflates the high-pressure chamber of the quick-opening valve mechanism and the gas storage bottle, each physical parameter complies with Formula 1:

[0039] P0=n0RT / V1 (1)

[0040] Where: P0 is the initial pressure of the high-pressure chamber (MPa), n0 is the amount of initial gas substance (mol), R is the molar gas constant (J / mol·K), T is the temperature (K), and V1 is the volume of the high-pressure chamber and the gas cylinder. The first round of calibration test was carried out. After the pressure rod was pressed, the high-pressure chamber was connected to the low-pressure chamber. At this time, Formula 1 changed to Formula 2:

[0041] P1=n0RT / (V1+V2) (2)

[0042] Where: V2 is the volume of the low-pressure chamber; the pressure rod rebounds, and the high-pressure and low-pressure chambers are isolated from each other again. The high-pressure gas in the low-pressure chamber is discharged from the exhaust hole 7, and the pressure of the high-pressure chamber remains unchanged at P1. Then the ideal gas equation in the high-pressure chamber and the gas storage bottle becomes:

[0043] P1=n1RT / V1 (3)

[0044] Where: n1 is the amount of gas in the high-pressure chamber and the gas cylinder after the first experiment. Assuming that the temperature remains unchanged during the experiment, this value can be calculated using the known parameters in equations 1 and 2.

[0045] According to the derivation of equations 1 to 3, the calibration pressure P5 of the low-pressure chamber during the fifth test can be recursively calculated in sequence, as shown in equation 4:

[0046] P5=n4RT / (V1+V2) (4)

[0047] The overall structure of the low-pressure chamber of the quick-opening valve mechanism is cylindrical, with a radius of 6mm and a length of 1.5mm. The basic volume of the low-pressure chamber is 301.584mm 3 ; Low pressure chamber connection hole, radius 3mm, length 1.5mm, connection hole volume 42.412mm 3 Considering the volume of the sensor installation and the pressure transmission path of the low-pressure chamber, the low-pressure chamber V2 is 400mm 3 Assuming that the preload gauge pressure in the high-pressure chamber and the gas cylinder is 1MPa before the test, in order to ensure that the loading pressure value of the device does not change by more than 0.1% after 5 rounds of tests, it can be calculated according to formula 1-4 that the volume of the high-pressure chamber and the gas cylinder should be greater than 2080cm 3 Considering the portability of the device, the high-pressure chamber is designed as a cylinder with a radius of 22mm and a height of 53mm, and the gas cylinder adopts a 2L standard steel cylinder; According to the above structural dimension parameters, it can be calculated that in the fifth round of tests, the transposed loading pressure value is 0.99904MPa, and the pressure source change ΔP is:

[0048] ΔP=P0-P5=1-0.99904=0.096% (5)

[0049] That is, after 5 rounds of tests, the pressure source changes ≤ 0.1%, which meets the design indicators of the device. According to the calculation results, it can be proved that the device still has excellent stability after 4 to 5 rounds of calibration tests without the external gas source.

[0050] According to the calculation results, under the premise of ensuring the stability of the gas source (the change does not exceed 0.1%), the number of calibrations after a single inflation can be increased by replacing the volume of the gas cylinder. Table 1 shows the maximum theoretical test times of the device after pressurization to 1MPa when it is equipped with standard gas cylinders of different specifications.

[0051] Table 1 Maximum theoretical test times of different specifications of gas cylinders after pressurization to 1MPa

[0052] Gas cylinder capacity (L) Maximum number of theoretical experiments Changes in stress sources (%) 2 5 0.096％ 3 7 0.091％ 4 10 0.098％ 5 12 0.094％

[0053] The calibration workflow of a portable quasi-static pressure calibration device is as follows:

[0054] 1) Connect the proportional valve, quick-opening valve mechanism, gas storage cylinder, standard pressure transmitter, PID adjustment module in sequence, and install the calibrated pressure sensor;

[0055] 2) According to the calibration requirements, set the PID adjustment module parameters through the host computer;

[0056] 3) Open the switch valve between the quick-opening valve mechanism and the proportional valve, and inflate the quick-opening valve mechanism and the gas cylinder through an external gas source until the preset pressure is reached;

[0057] 4) Disconnect the external gas source. According to actual needs, the proportional valve, PID adjustment module and related connecting cables and gas lines can be disassembled under the premise of closing the switch valve, and only the quick-opening valve mechanism, gas storage bottle, standard pressure transmitter and calibration pressure sensor are retained to improve the portability of the equipment;

[0058] 6) The experimenter operates the quick-opening valve mechanism and conducts multiple rounds of quasi-static calibration experiments;

[0059] 7) After the test is completed, determine whether to connect an external gas source based on the experimental results and conduct the next round of experiments.

Claims

1. A portable quasi-static pressure calibration device, characterized in that: Includes quick-opening valve mechanism, standard pressure transmitter and gas storage bottle; The quick-opening valve mechanism comprises a mounting block, a high-pressure chamber (4) is arranged in the mounting block, a side wall of the high-pressure chamber (4) is provided with a standard pressure monitoring hole (2), the high-pressure chamber (4) is connected to the gas cylinder through a gas cylinder connecting hole (3) on the mounting block, a stepped hole is opened on one side of the mounting block, the stepped hole is used for detachably connecting a calibrated sensor mounting structure (11), the end of the stepped hole away from the side is a low-pressure chamber (8), the calibrated sensor mounted on the calibrated sensor mounting structure (11) is located in the low-pressure chamber (8), and a pressure monitoring hole (2) is provided on the mounting block at the upper part of the stepped hole. An exhaust hole (7) parallel to the axis of the stepped hole; a connecting cavity connecting the high-pressure cavity (4) and the low-pressure cavity (8) is also provided on the mounting block, and the connecting cavity includes a high-pressure cavity connecting hole parallel to the axis of the exhaust hole and a connecting locking mechanism mounting hole perpendicular to the axis of the exhaust hole; a pressure rod spring-type connecting locking mechanism is provided in the connecting locking mechanism mounting hole, and the high-pressure cavity and the low-pressure cavity are connected by pressing the pressure rod, thereby achieving measurement; the pressure rod is released, the high-pressure cavity connecting hole is sealed, and the gas in the low-pressure cavity is discharged through the exhaust hole, thereby achieving the recovery of the calibration device.

2. The portable quasi-static pressure calibration device according to claim 1, characterized in that: The pressure rod spring type connecting locking mechanism comprises a pressure rod (5), a pressure rod spring, a sealing ring (6), a sealing ball (9), a sealing block and a sealing spring (10); The pressure rod comprises a pressure rod head and a pressure rod body, and an inclined step for limiting the sealing ball and an annular protrusion for limiting the pressure rod spring and the pressure rod body are arranged in the connecting locking mechanism installation hole; the diameter of the pressure rod head is larger than the diameter of the pressure rod body, a pressure rod spring is arranged between the pressure rod head and the annular protrusion, and the pressure rod spring is sleeved outside the upper half of the pressure rod body; two sealing ring annular protrusions are arranged in the middle of the pressure rod body, and an annular groove for installing a sealing ring (6) is formed between the two sealing ring annular protrusions, and the sealing ring (6) realizes the sealing between the pressure rod body and the inner wall of the connecting locking mechanism installation hole; a sealing spring (10) is arranged at the bottom of the connecting locking mechanism installation hole, and the sealing block comprises a columnar end and a groove section connected to the sealing ball and having a diameter larger than the columnar section, and the sealing spring (10) is sleeved outside the columnar section. When the pressure rod head is loosened, under the action of the sealing spring, the sealing block and the sealing ball move upward, and the sealing ball (10) is clamped at the inclined step to realize the sealing of the high-pressure chamber.

3. The portable quasi-static pressure calibration device according to claim 2, characterized in that: The sealing ball (9) is made of elastic material.

4. The portable quasi-static pressure calibration device according to claim 3, characterized in that: The material of the sealing ball (9) is rubber, polytetrafluoroethylene or polyethylene.

5. The portable quasi-static pressure calibration device according to claim 4, characterized in that: It also includes a PID adjustment module. The mounting block is also provided with a high-pressure chamber air inlet (1). The high-pressure chamber air inlet is connected to an external high-pressure gas source via a proportional valve and a switch valve. The proportional valve is connected to the PID adjustment module. The switch valve is used to disconnect the air-tightening of the quick-opening valve mechanism behind the proportional valve. The standard pressure transmitter obtains the pressure change in the high-pressure chamber in real time, converts it into a voltage value and transmits it to the PID adjustment module. The PID adjustment module performs PID control on the inflation and pressurization process of the proportional valve according to the output voltage value of the standard pressure transmitter.

6. The portable quasi-static pressure calibration device according to claim 5, characterized in that: The sum of the volumes of the high-pressure chamber and the gas cylinder V1 and the volume of the low-pressure chamber V2 satisfy that the pressure source change ΔP≤0.1% after i tests.

7. The portable quasi-static pressure calibration device according to claim 1, characterized in that: The section with the largest diameter of the calibrated sensor mounting structure (11) and the corresponding section of the stepped hole are threadedly connected.

8. The portable quasi-static pressure calibration device according to claim 7, characterized in that: The calibrated sensor installation structure (11) is provided with a plurality of specifications, and a different calibrated sensor installation structure (11) is selected according to different types of the calibrated sensors.

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