Primary traceability system of piston type micro flow measurement standard device

Abstract

The utility model relates to a primary traceability system of a piston type micro flow measurement standard device. Two incompatible fluid media are arranged in a second container in the system, wherein the upper-layer fluid medium is used for avoiding volatilization of the lower-layer fluid medium; and the output end of the piston type micro flow measurement standard device is connected into the second container through a pipeline and is immersed into the lower-layer fluid medium. According to the piston type micro flow measurement standard device, liquid discharged according to the specified flow flows into a second container arranged in an electronic balance, the liquid is contained in the lower layer of the second container, and liquid paraffin is contained in the upper layer of the second container and is kept in an overflow state; the liquid paraffin overflowing from the second container flows into the external first container, the mass of the liquid discharged by the piston type micro-flow measurement standard device is weighed through the electronic balance, and the original-level traceability of the volume of the piston type micro-flow measurement standard device is achieved through buoyancy correction and mass-density-volume conversion. According to the utility model, high accuracy, high repeatability and reproducibility of the piston type micro flow measurement standard device in long-time and low-mass weighing traceability can be realized.

Description

Technical Field

[0001] The utility model relates to a flow standard device traceability system, in particular to a primary traceability system of a piston type micro-flow measurement standard device. Background Art

[0002] In recent years, the application of micro-flow measurement and control in the fields of semiconductor manufacturing, medical chemical industry, food hygiene, bioengineering, high-tech, etc. has become more and more common. The calibration of micro-flow related instruments has become one of the important branches in the current flow measurement field. The piston flow measurement standard device has developed rapidly in recent years because its value accuracy comes from the dimensional accuracy of the plunger or piston cylinder, and it is easy to achieve the output of micro-standard flow with the help of driving components such as motors.

[0003] At present, the traceability methods of piston flow measurement standard devices include the traceability of time and volume. The traceability of time is mainly completed by a timer with high accuracy. Therefore, the traceability accuracy of this type of standard device depends on the traceability result of the volume. At present, there are two main volume traceability methods for piston flow measurement standard devices: dimension method and weighing method. The dimension method mainly measures the dimension accuracy of the plunger or piston cylinder and the longitudinal displacement accuracy driven by the motor and other driving components. The volume traceability result of the standard device is obtained by tracing the cross-sectional area and the movement distance respectively. This traceability method is applicable to the situation where the plunger or piston traceability has been completed before the installation of the standard device. Since the motor and other driving components always vibrate, the repeatability of the traceability result of the movement distance is also poor for standard devices with short movement distances or no suitable location to place the distance measurement target. The weighing method generally fills the piston flow measurement standard device with liquid (generally pure water), weighs the mass of the liquid discharged by the set standard device volume, and calculates the standard volume of the standard device, and obtains the traceability result of the standard device volume at one time. This method is more applicable to standard devices with larger weighing mass. For standard devices for measuring small flow rates, due to the small weighing mass and long time, the volatilization amount of the liquid cannot be ignored. The traceability repeatability under different temperatures, humidity and airflows is poor, and the pipe outlet should have tension hanging on it with an indefinite amount of liquid, which will produce a large deviation for the traceability results at the ml level. Utility Model Content

[0004] In order to solve the problems existing in the background technology, the utility model provides a primary traceability system for a piston-type micro-flow measurement standard device, which can avoid the liquid volatilization caused by long-term tracing and the influence of unequal mass of liquid hanging on the wall at the pipeline outlet before and after tracing, and realize the piston-type micro-flow measurement standard device under different temperatures, humidity and airflows. High-accuracy, high repeatability and reproducible traceability.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0006] The utility model provides a primary traceability system of a piston-type micro-flow measurement standard device, comprising an electronic balance, a first container located on the electronic balance, and a second container located in the first container;

[0007] The second container is provided with two incompatible fluid media, wherein the upper fluid medium is used to prevent the volatilization of the lower fluid medium;

[0008] The output end of the piston-type micro-flow metering standard device is connected to the second container through a pipeline and immersed in the lower fluid medium.

[0009] Furthermore, the upper fluid medium in the second container is the same as the output fluid medium of the piston-type micro-flow measurement standard device.

[0010] Furthermore, the upper fluid medium is liquid paraffin and the lower fluid medium is pure water.

[0011] Furthermore, the upper level of the liquid paraffin is flush with the opening of the second container.

[0012] Furthermore, the pipe located above the second container has a gooseneck.

[0013] Furthermore, the output flow rate of the piston-type micro-flow measurement standard device is 5 to 1000 ml / h.

[0014] The utility model has the following beneficial effects:

[0015] 1. In the process of tracing, the liquid paraffin of the utility model always covers the liquid surface of the built-in beaker and the external beaker, thus avoiding the volatilization of the liquid in the lower layer. At the same time, since the liquid paraffin does not contain volatile elements such as sulfur, nitrogen and oxygen, it is inherently non-volatile, thus eliminating the adverse effects of long-term and low-quality weighing method traceability results caused by the volatilization of the traceability liquid under different temperatures, humidity and airflows during the entire traceability process.

[0016] 2. During the traceability process, the utility model has a gooseneck above the outlet pipe of the standard device, and it is always immersed in the liquid, avoiding the influence of unequal mass of liquid hanging on the wall at the outlet of the pipe before and after tracing. At the same time, the liquid level of the built-in beaker is always kept consistent, and the pressure at the outlet of the standard device remains basically unchanged, thereby improving the consistency of the state of the standard device before and after tracing.

[0017] Based on this, the utility model can realize high accuracy, high repeatability and reproducibility of the piston-type micro-flow measurement standard device in long-term, low-mass weighing traceability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1It is a structural schematic diagram of the utility model system.

[0019] In the figure: 1. Piston-type micro-flow measurement standard device; 2. Stainless steel pipe; 3. Gooseneck; 4. Built-in beaker; 5. External beaker; 6. Electronic balance; 7. Liquid paraffin; 8. Liquid. DETAILED DESCRIPTION

[0020] The present application is further described below in conjunction with the accompanying drawings and embodiments.

[0021] like Figure 1 As shown, an embodiment of the present application provides a primary traceability system for a piston-type micro-flow measurement standard device, including an electronic balance 6, an external beaker 5 (i.e., a first container) located on the electronic balance, and an internal beaker 4 (i.e., a second container) located in the external beaker 5.

[0022] The built-in beaker 4 is provided with two incompatible fluid media, wherein the upper fluid medium is used to prevent the volatilization of the lower fluid medium. In this example, the upper fluid medium is liquid paraffin 7, and the lower fluid medium is pure water 8, and the liquid paraffin 7 is overflowing.

[0023] One end of the output end of the piston-type micro-flow measurement standard device 1 is connected to one end of a stainless steel tube 2, and the other end of the stainless steel tube 2 is vertically inserted into the built-in beaker 4 and immersed in pure water 8 to prevent the liquid from adhering to the wall. The front section of the stainless steel tube 2 vertically inserted into the built-in beaker 4 is provided with a gooseneck head 3, which is used to ensure that the incoming flow of the piston-type micro-flow measurement standard device passes through the highest point, so that when the standard device stops, no self-flow is generated.

[0024] The traceability process of the embodiment of this application:

[0025] The piston-type micro-flow metering standard device can be traced in N sections starting from the starting point of the movement. Before a single traceability, the outlet of the piston-type micro-flow metering standard device is connected to a stainless steel pipe, which is placed in the built-in beaker (i.e., the second container) in the electronic balance after passing through the gooseneck. The lower layer of the built-in beaker is filled with the same liquid as the standard device, taking pure water as an example. The upper layer is filled with liquid paraffin and the built-in beaker is kept overflowing, that is, the upper horizontal surface of the liquid paraffin is flush with the opening of the built-in beaker. The built-in beaker is placed in an external beaker (the first container), and the liquid paraffin overflowing from the built-in beaker will flow into the external beaker.

[0026] Before tracing back, the outlet of the standard device should be immersed in the pure water in the built-in beaker, and the initial reading Q0 of the electronic balance should be read. Set the nominal volume V of the standard device for this traceability output, start the standard device, and output pure water at the set flow rate F. As the liquid in the standard device is discharged into the built-in beaker, the lower layer of pure water in the cup will gradually increase, and the upper layer of liquid paraffin in the built-in beaker will overflow into the external beaker. When the standard device has completed the output according to the set nominal value of pure water volume, read the end reading Q1 of the electronic balance.

[0027] The pure water density r at the current temperature is obtained by looking up the pure water density table or measuring with a density meter. When the elastic modulus of the standard device material and the system expansion are not considered, the error d of the nominal volume V of the standard device is calculated as follows:

[0028]

[0029] Where c is the air buoyancy correction coefficient, which is taken as 1.0011.

[0030] Furthermore, when the liquid paraffin in the built-in beaker cannot completely cover the pure water, the tracing should be stopped immediately, the pure water should be drawn out of the built-in beaker, and liquid paraffin should be added until the built-in beaker overflows. After the state stabilizes, the next tracing should be carried out according to a certain section of the above process, and the traceability results should be repetitively calculated.

[0031] Taking a piston flow metering standard of (5-1000) ml / h as an example, the total volume is 60 ml, and the traceability is carried out in 3 sections. At a flow rate of 100 ml / h, each section is traced 3 times, and each traceability takes about 10 minutes. The traceability results are shown in Table 1. The results show that this embodiment eliminates the influence of liquid volatilization and unequal mass of liquid hanging on the wall at the pipeline outlet before and after tracing, and ensures that the pressure before and after tracing remains basically unchanged, which can achieve high accuracy, high repeatability and reproducibility of the piston-type micro-flow metering standard device in long-term, low-mass weighing traceability.

[0032] Table 1

[0033]

[0034] The above specific implementation modes are used to explain the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A primary traceability system for a piston-type micro-flow measurement standard device, characterized in that: The invention comprises an electronic balance, a first container located on the electronic balance, and a second container located in the first container; The second container is provided with two incompatible fluid media, wherein the upper fluid medium is used to prevent the volatilization of the lower fluid medium; The output end of the piston-type micro-flow metering standard device is connected to the second container through a pipeline and immersed in the lower fluid medium.

2. The primary traceability system of a piston-type micro-flow measurement standard device according to claim 1 is characterized in that: The upper fluid medium in the second container is the same as the output fluid medium of the piston-type micro-flow measurement standard device.

3. The primary traceability system of a piston-type micro-flow measurement standard device according to claim 1 is characterized in that: The upper fluid medium is liquid paraffin, and the lower fluid medium is pure water.

4. The primary traceability system of a piston-type micro-flow measurement standard device according to claim 3 is characterized in that: The upper level of the liquid paraffin is flush with the opening of the second container.

5. A primary traceability system for a piston-type micro-flow measurement standard device according to any one of claims 1 to 4, characterized in that: The pipe located above the second container has a gooseneck.

6. The primary traceability system of a piston-type micro-flow measurement standard device according to claim 5 is characterized in that: Features: The output flow rate of the piston-type micro-flow measurement standard device is 5-1000 ml / h.

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