Calibration system and calibration method of mass flow controller

Abstract

The present invention provides a calibration method for a mass flow controller, comprising: controlling the fluid pressure upstream of the mass flow controller to reach multiple detection points in sequence, and obtaining the upstream fluid pressure value of the mass flow controller and the corresponding pressure detection value of the pressure sensor when the fluid pressure upstream of the mass flow controller reaches each detection point; obtaining a calculation formula for the corresponding relationship between the upstream theoretical fluid pressure value and the pressure detection value corresponding to each detection point interval based on the two upstream fluid pressure values ​​and two pressure detection values ​​corresponding to each adjacent detection point; and writing the calculation formula corresponding to each detection point interval into the mass flow controller. The calibration method provided by the present invention can automatically determine the calculation formula between the pressure detection value of the pressure sensor and the upstream theoretical fluid pressure value of the mass flow controller, complete the calibration of the pressure sensor, and improve the consistency and reliability of the sensor calibration results. The present invention also provides a calibration system for a mass flow controller.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor process equipment, and in particular to a calibration method for a mass flow controller and a calibration system for a mass flow controller. Background Art

[0002] A mass flow controller (MFC) is a fluid flow control device that monitors flow in real time and precisely measures and controls gas mass flow. It is widely used in industries such as semiconductors, fuel cells, solar energy, vacuum coating, and analytical instruments. The accuracy and reliability of mass flow controllers have become key factors affecting process accuracy and stability in these fields.

[0003] A pressure-type mass flow controller (pressure-type MFC) operates by exploiting the fact that, under certain conditions, the velocity of gas passing through a restricting orifice (throat) reaches the speed of sound. Specifically, a first pressure sensor and a second pressure sensor are located upstream and downstream of the orifice. When the pressure at the inlet and outlet of the pressure-type mass flow controller meets certain conditions, the velocity of gas passing through the orifice reaches the speed of sound and does not increase any further. This flow state is also known as blocked flow. At this point, the first and second pressure sensors detect the inlet fluid pressure P1 and outlet fluid pressure P2 of the flow channel at the front end of the throat, respectively, to determine the fluid flow rate in the restricting orifice (throat).

[0004] Due to the unique characteristics of pressure-type mass flow controllers, flow detection requires a comprehensive assessment based on the relationship between the pressure values ​​obtained by the two pressure sensors. When the ratio of the first pressure sensor's measured value, P1, to the second pressure sensor's measured value, P2, is greater than or equal to 2, the MFC flow rate and the first pressure sensor's measured value, P1, have a linear relationship. When the ratio is less than 2, the MFC flow rate and P1 have a functional relationship. Therefore, during the calibration process of a mass flow controller, pressure calibration must be performed on both pressure sensors separately to ensure their performance.

[0005] However, existing mass flow controller calibration methods primarily rely on manual operator calibration of pressure sensors, which is unreliable and time-consuming. Furthermore, the calibration process relies on manual recording of data at a specific moment, which is subject to randomness and inaccuracy. This makes it impossible to guarantee that every calibrated sensor is qualified, which can easily impact subsequent mass flow controller production processes. Furthermore, the mass flow controller production process is complex and time-consuming, and sensor problems can significantly reduce the profitability of subsequent processes, impacting production efficiency and product yield. Summary of the Invention

[0006] The present invention aims to provide a calibration method and calibration system for a mass flow controller, which can automatically calibrate the pressure sensor in the mass flow controller, reduce the manpower input in the sensor calibration process, and improve the consistency and reliability of the sensor calibration results.

[0007] To achieve the above object, as one aspect of the present invention, a method for calibrating a mass flow controller is provided, wherein at least one pressure sensor is provided on a fluid passage of the mass flow controller, the method comprising:

[0008] controlling the fluid pressure upstream of the mass flow controller to reach a plurality of detection points in sequence, and obtaining the upstream fluid pressure value of the mass flow controller and the corresponding pressure detection value of the pressure sensor when the fluid pressure upstream of the mass flow controller reaches each of the detection points;

[0009] According to the two upstream fluid pressure values ​​and the two pressure detection values ​​corresponding to each two adjacent detection points, a calculation formula for the corresponding relationship between the upstream theoretical fluid pressure value and the pressure detection value corresponding to each detection point interval is obtained;

[0010] The calculation formula corresponding to each detection point interval is written into the mass flow controller.

[0011] Optionally, controlling the fluid pressure upstream of the mass flow controller to reach a plurality of detection points in sequence comprises:

[0012] According to the set number of cycles, the same detection point is detected a corresponding number of times, wherein a single cycle is to control the fluid pressure upstream of the mass flow controller to increase from the detection point with the minimum pressure value to the detection point with the maximum pressure value, and then control the fluid pressure to decrease from the detection point with the maximum pressure value to the detection point with the minimum pressure value;

[0013] The pressure detection value is an average value of a detection value of a corresponding detection point of a corresponding pressure sensor during an increasing change in the fluid pressure upstream of the mass flow controller and a detection value of a corresponding detection point during a decreasing change in the fluid pressure.

[0014] Optionally, the calibration method further includes:

[0015] According to the target pressure range, a plurality of detection points and the number of cycles corresponding to the target pressure range are obtained from a database.

[0016] Optionally, the calibration method further includes:

[0017] When the difference between the detection value of the pressure sensor at the corresponding detection point during the increasing change of the fluid pressure and the detection value of the corresponding detection point during the decreasing change of the fluid pressure is greater than a first preset difference threshold, the calibration is stopped and the mass flow controller is determined to be unqualified.

[0018] Optionally, the first preset difference threshold is between 0.4 kPa and 0.6 kPa.

[0019] Optionally, controlling the fluid pressure upstream of the mass flow controller to reach a plurality of detection points in sequence includes:

[0020] The fluid pressure upstream of the mass flow controller is controlled so that the difference between the upstream fluid pressure value and each detection point in sequence is not greater than a second preset difference threshold.

[0021] Optionally, the second preset difference threshold is less than 0.02 kPa.

[0022] Optionally, the calibration method further includes:

[0023] Controlling the fluid pressure upstream of the mass flow controller to reach a test pressure, and obtaining the upstream fluid pressure value of the mass flow controller and the pressure detection value of the pressure sensor;

[0024] Calculating the upstream theoretical fluid pressure value based on the pressure detection value of the pressure sensor according to the obtained calculation formula;

[0025] The upstream theoretical fluid pressure value is compared with the upstream fluid pressure value. When the difference between the upstream theoretical fluid pressure value and the upstream fluid pressure value is greater than a third preset difference threshold, the mass flow controller is determined to be unqualified.

[0026] Optionally, the calculation formula is Y=a(X+b), wherein Y is the theoretical fluid pressure value upstream of the mass flow controller, X is the flow detection value of the pressure sensor, and a and b are constants.

[0027] As a second aspect of the present invention, a calibration system for a mass flow controller is provided, the calibration system comprising a host computer, a calibration fluid path and a pressure controller, the calibration fluid path having a calibration position for connecting to the mass flow controller to be measured, the host computer being able to control the pressure controller to change the fluid pressure upstream of the calibration position, and the host computer being able to implement the calibration method for the mass flow controller described above.

[0028] The calibration method and calibration system of the mass flow controller provided by the present invention can automatically determine the calculation formula between the pressure detection value of the pressure sensor and the theoretical fluid pressure value upstream of the mass flow controller, and write the obtained calculation formula into the mass flow controller to complete the calibration of the pressure sensor in the mass flow controller, thereby reducing the manpower input in the pressure sensor calibration process and the product failure rate caused by inevitable mistakes or errors in manual operation. While saving a large amount of human resources, the consistency and reliability of the sensor calibration results are guaranteed, thereby ensuring the product quality of the mass flow controller and improving the work efficiency of the production workshop. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 1 is a schematic structural diagram of a calibration system for a mass flow controller provided in an embodiment of the present invention;

[0031] Figure 2 1 is a flow chart of a calibration method for a mass flow controller provided by an embodiment of the present invention;

[0032] Figure 3 is a flow chart of a calibration method for a mass flow controller provided by another embodiment of the present invention;

[0033] Figure 4 It is a flow chart of a calibration method for a mass flow controller provided by another embodiment of the present invention. DETAILED DESCRIPTION

[0034] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0035] In order to solve the above technical problems, as one aspect of the present invention, a calibration method of a mass flow controller is provided, wherein at least one pressure sensor is provided on the fluid path of the mass flow controller, such as Figure 2 As shown, the calibration method includes:

[0036] Step S1, controlling the fluid pressure upstream of the mass flow controller to reach multiple detection points in sequence, and obtaining the upstream fluid pressure value of the mass flow controller and the corresponding pressure detection value of the pressure sensor when the fluid pressure upstream of the mass flow controller reaches each detection point;

[0037] Step S2: Based on the two upstream fluid pressure values ​​and the two pressure detection values ​​corresponding to each two adjacent detection points, a calculation formula for the corresponding relationship between the upstream theoretical fluid pressure value Y and the pressure detection value corresponding to each detection point interval (i.e., the pressure interval with the two adjacent detection points as endpoints) is obtained (multiple calculation formulas corresponding to multiple detection point intervals can be used together to calculate the value of the upstream theoretical fluid pressure Y based on the pressure detection values);

[0038] Step S3: Write the calculation formula corresponding to each detection point interval into the mass flow controller.

[0039] As an optional embodiment of the present invention, Figure 1 As shown, the mass flow controller to be calibrated is a pressure-type mass flow controller, that is, the fluid path includes a throat section, and on the fluid path, a first pressure sensor and a second pressure sensor are respectively provided upstream and downstream of the throat section. The mass flow controller is used to control the flow rate of the fluid (such as gas) by controlling the flow rate of the fluid through the throat section, and determines the fluid flow rate through the pressure detection values ​​(inlet pressure P1, outlet pressure P2) of the first pressure sensor and the second pressure sensor and the calculation formula determined by the calibration method provided by the embodiment of the present invention.

[0040] Optionally, the calculation formula can be a linear equation, for example, it can be expressed as Y=a(X+b), where Y is the upstream theoretical fluid pressure value, X is the flow detection value of the pressure sensor (first pressure sensor, second pressure sensor), and a and b are constants (where a is the slope and b is the intercept).

[0041] For example, taking the pressure detection value (inlet pressure P1) of the first pressure sensor as an example, when the fluid pressure upstream of the mass flow controller reaches two adjacent detection points, the upstream fluid pressure values ​​of the mass flow controller are Y1 and Y2 respectively, and the corresponding pressure detection values ​​of the first pressure sensor are X1 and X2 respectively. Then, the calculation formula Y=a1(X+b1) for the corresponding relationship between the upstream theoretical fluid pressure value Y and the pressure detection value X corresponding to the detection point interval can be determined based on the points (X1, Y1) and (X2, Y2); similarly, based on the upstream fluid pressure values ​​Y2 and Y3 corresponding to the next group of adjacent two detection points and the pressure detection values ​​X2 and X3 of the first pressure sensor, the calculation formula Y=a2(X+b2) corresponding to the detection point interval is determined. Similarly, the values ​​of constants a and b in the calculation formula corresponding to each two adjacent detection points (each detection point interval) are calculated respectively until all the calculation formulas are obtained and stored in the mass flow controller (the same algorithm is performed on the second pressure sensor and will not be repeated here).

[0042] The mass flow controller calibration method provided by the present invention can automatically determine a calculation formula between a pressure detection value X of a pressure sensor and a theoretical fluid pressure value Y upstream of the mass flow controller, and write the obtained calculation formula into the mass flow controller to complete the calibration of the pressure sensors (first pressure sensor, second pressure sensor) in the mass flow controller, thereby reducing the manpower input in the pressure sensor calibration process and the product failure rate caused by inevitable mistakes or errors in manual operation. While saving a large amount of human resources, it ensures the consistency and reliability of the sensor calibration results, thereby ensuring the product quality of the mass flow controller and improving the work efficiency of the production workshop.

[0043] It should be noted that the pressure sensors (the first and second pressure sensors) directly detect fluid pressure and generate analog signals, which must be converted to digital signals by an AD conversion module (not shown) before they can be used for comparison and calculation. The calibration method for a mass flow controller provided in an embodiment of the present invention can be automatically implemented by a calibration system and is particularly suitable for calibrating pressure sensors within a small pressure range (fluid pressure below 20 kPa). For example, when the user selects a target pressure range of 5-15 kPa, the database can be queried to obtain pre-stored commonly used detection point values: 5 kPa, 7 kPa, 8 kPa, 9 kPa, 10 kPa, 11 kPa, 12 kPa, 13 kPa, 14 kPa, and 15 kPa.

[0044] Existing manual calibration methods for mass flow controller pressure sensors typically limit accuracy to a pressure range of 20 kPa to 200 kPa at the detection point, making it difficult to accurately calibrate within a small pressure range below 20 kPa. However, the calibration method for mass flow controllers provided by the present invention can be automatically implemented by a calibration system, improving the applicability and accuracy of pressure sensors within a small pressure range.

[0045] In order to improve the accuracy of the pressure detection value, as a preferred embodiment of the present invention, the step of controlling the fluid pressure upstream of the mass flow controller to reach multiple detection points in sequence includes:

[0046] According to the set number of cycles, the same detection point is tested a corresponding number of times, wherein a single cycle is to control the fluid pressure upstream of the mass flow controller to increase from the detection point with the minimum pressure value to the detection point with the maximum pressure value, and then control the fluid pressure to decrease from the detection point with the maximum pressure value to the detection point with the minimum pressure value;

[0047] The pressure detection value is the average value of the detection value of the corresponding detection point of the corresponding pressure sensor during the process of increasing fluid pressure upstream of the mass flow controller and the detection value of the corresponding detection point during the process of decreasing upstream fluid pressure.

[0048] Still taking the case where the target pressure range is 5-15kPa as an example, after completing the detection of the 5kPa pressure, the fluid pressure upstream of the mass flow controller is adjusted from 5kPa to 7kPa, 8kPa, 9kPa, 10kPa, 11kPa, 12kPa, 13kPa, 14kPa, and 15kPa in sequence and the detection values ​​of the corresponding pressure sensors are obtained. Then, the fluid pressure upstream of the mass flow controller is adjusted from 15kPa to 14kPa, 13kPa, 12kPa, 11kPa, 10kPa, 9kPa, 8kPa, 7kPa, and 5kPa in reverse and the detection values ​​of the corresponding pressure sensors are obtained. Finally, the detection values ​​of the pressure sensors (first pressure sensor or second pressure sensor) corresponding to the same detection point are averaged to obtain the pressure detection values ​​of the pressure sensor corresponding to each detection point.

[0049] Alternatively, in other embodiments of the present invention, the calculation formula for each cycle can be obtained based on the detection values ​​of the pressure sensor corresponding to two adjacent detection points in each cycle, and then the average value of the calculation formulas corresponding to multiple cycles can be calculated to obtain the final calculation formula.

[0050] Specifically, when the calculation formula is a linear equation Y=a(X+b), the slope a and intercept b in the calculation formula Y=a(X+b) between the upstream theoretical fluid pressure value Y and the pressure detection value X corresponding to each cycle can be first calculated, and then the average values ​​of the slopes a and intercepts b corresponding to multiple cycles can be calculated respectively to obtain the average slope and average intercept, and then the final calculation formula can be obtained.

[0051] For example, if the calculation formulas obtained after multiple cycles at two adjacent test points are Y = 3.4(X + 2), Y = 3.35(X + 2.1), Y = 3.4(X + 1.9), and Y = 3.4(X + 2.1), and the slope a and intercept b are averaged, the average slope is 3.39 and the average intercept is 2.25, then the calculation formula for the pressure sensor corresponding to this pair of test points is determined to be Y = 3.39(X + 2.25).

[0052] In order to improve the calibration efficiency, as a preferred embodiment of the present invention, the values ​​of each detection point under each commonly used fluid pressure range can be pre-stored in the database of the calibration system, such as Figure 3 As shown, the calibration method also includes:

[0053] Step S0: acquiring a plurality of detection points and cycle times corresponding to the target pressure range from a database according to the target pressure range.

[0054] In order to improve the product yield of the mass flow controller, as a preferred embodiment of the present invention, the calibration method further includes:

[0055] After controlling the fluid pressure upstream of the mass flow controller to undergo at least one cycle of increasing and decreasing changes, when the difference between the detection value of the corresponding detection point of the pressure sensor during the increasing change of the fluid pressure and the detection value of the corresponding detection point during the decreasing change of the fluid pressure is greater than a first preset difference threshold, the calibration is stopped and the mass flow controller is determined to be unqualified.

[0056] In an embodiment of the present invention, two detection values ​​successively detected by the same pressure sensor when the fluid pressure passes through the same detection point twice during an increasing change and a decreasing change of the fluid pressure are compared. When the difference between the two detection results is too large (greater than a first preset difference threshold), it indicates that the pressure controller has poor stability, and the mass flow controller is directly judged as unqualified, thereby improving the product yield of the mass flow controller.

[0057] As an optional embodiment of the present invention, the first preset difference threshold is 0.5kPa (0.5 kiloPascal, i.e. 500Pa (Pascal)), that is, when the difference between the two detection values ​​obtained by the pressure sensor during two detections during an increasing change in fluid pressure and a decreasing change in fluid pressure is greater than 0.5kPa, it is considered that the pressure sensor has poor stability and is difficult to meet the use requirements of the mass flow controller.

[0058] The embodiment of the present invention does not specifically limit the criteria for determining whether the fluid pressure upstream of the mass flow controller reaches the detection point. For example, in order to shorten the adjustment time of adjusting the upstream fluid pressure and improve the calibration efficiency of the mass flow controller, as a preferred embodiment of the present invention, a difference range can be given in advance. When the difference between the upstream fluid pressure and the detection point is small, it is considered that the upstream fluid pressure has reached the detection point, avoiding repeated overly precise adjustment of the upstream fluid pressure, which affects the calibration efficiency. The steps of controlling the fluid pressure upstream of the mass flow controller to reach multiple detection points in sequence may specifically include:

[0059] The fluid pressure upstream of the mass flow controller is controlled so that the difference between the upstream fluid pressure value and each detection point in sequence is not greater than a second preset difference threshold.

[0060] As an optional embodiment of the present invention, the second preset difference threshold is less than 0.02 kPa. For example, in some embodiments of the present invention, the second preset difference threshold may be 0.01 kPa. That is, when the difference between the upstream fluid pressure value and the current detection point is no greater than 0.01 kPa, the fluid pressure is deemed to have reached the detection point, and the detection results of the two pressure sensors can be read. For example, when calibrating the detection point to 5 kPa, the fluid pressure upstream of the mass flow controller is adjusted so that the fluid pressure is within the range of 5 ± 0.01 kPa. The detection results of the two pressure sensors and the upstream fluid pressure value can then be read.

[0061] As a preferred embodiment of the present invention, the calibration method may further include the step of testing the calibrated mass flow controller, that is, controlling the fluid pressure upstream of the mass flow controller to a pressure value different from the test point, and comparing the upstream theoretical fluid pressure value obtained by the calibrated mass flow controller with the upstream fluid pressure value to see whether it is consistent. Specifically, Figure 4 As shown, the calibration method also includes:

[0062] Step S4, controlling the fluid pressure upstream of the mass flow controller to reach a test pressure, and obtaining the upstream fluid pressure value of the mass flow controller and the pressure detection value of the pressure sensor;

[0063] Step S5: Calculate the upstream theoretical fluid pressure value based on the pressure detection value of the pressure sensor according to the obtained calculation formula;

[0064] Step S6: Compare the upstream theoretical fluid pressure value with the upstream fluid pressure value. When the difference between the upstream theoretical fluid pressure value and the upstream fluid pressure value is greater than a third preset difference threshold, determine that the mass flow controller is unqualified.

[0065] In an embodiment of the present invention, the size of the third preset difference threshold can be determined based on the normal error size of the mass flow controller. For example, when the error of the mass flow controller is 0.01 kPa, the third preset difference threshold can be 0.01 kPa. That is, when the difference between all upstream theoretical fluid pressure values ​​and upstream fluid pressure values ​​is less than or equal to 0.01 kPa, the difference is considered to be a normal error, and the calibrated mass flow controller can accurately detect the upstream fluid pressure and thus accurately detect the flow rate; when the difference between the upstream theoretical fluid pressure value and the upstream fluid pressure value is greater than 0.01 kPa, it is considered that the pressure value detected by the calibrated mass flow controller deviates too much from the actual upstream pressure value, and the mass flow controller is unqualified.

[0066] As a second aspect of the present invention, a calibration system for a mass flow controller is provided, such as Figure 1As shown, the calibration system includes a host computer (computer), a calibration fluid path and a pressure controller (the pressure controller has a control accuracy of ±0.001kPa on the fluid pressure). The calibration fluid path has a calibration position for connecting to the mass flow controller to be measured. The host computer can control the pressure controller to change the fluid pressure upstream of the calibration position (so that the fluid pressure reaches each detection point and detects the upstream fluid pressure value), and can implement the calibration method provided in the embodiment of the present invention.

[0067] The mass flow controller calibration system provided by the present invention can automatically determine a calculation formula between a pressure detection value X of a pressure sensor and a theoretical fluid pressure value Y upstream of the mass flow controller, and write the obtained calculation formula into the mass flow controller to complete the calibration of the pressure sensors (first pressure sensor, second pressure sensor) in the mass flow controller, thereby reducing the manpower input in the pressure sensor calibration process and the product failure rate caused by inevitable mistakes or errors in manual operation. While saving a large amount of human resources, it ensures the consistency and reliability of the sensor calibration results, thereby ensuring the product quality of the mass flow controller and improving the work efficiency of the production workshop.

[0068] As a preferred embodiment of the present invention, Figure 1 As shown, the calibration system also includes a system control module and a database. The upper computer controls the opening and closing of the stop valve and controls the pressure controller to change the fluid pressure upstream of the calibration position through the system control module. The upper computer can communicate with the database through the system control module and obtain information such as common detection points corresponding to each target pressure range from the database.

[0069] As an optional embodiment of the present invention, the host computer can be a computer, which has software for automatically calibrating sensors stored therein, and can implement the calibration method of the mass flow controller provided by the embodiment of the present invention by running the software. In order to facilitate the user to control the calibration process in real time, as a preferred embodiment of the present invention, the host computer software also includes a related program for displaying a human-computer interaction interface to the user. The user can interact with the calibration system through the host computer and select it in the database according to the name of the data file. For example, 5-15kPa can be searched according to the target pressure range to see if there is a pressure range that meets one's needs, and the user can select it in the interface of the host computer software, and import the corresponding data file in the database into the host computer software. At the same time, the user can also select the number of cycles of step S1 in the host computer software, and the duration of collecting the pressure detection value of the pressure sensor when the upstream fluid pressure is stable at each detection point, etc.

[0070] As an optional embodiment of the present invention, Figure 1As shown, the calibration system also includes a stop valve, which is connected between the air source and the pressure controller to control the on / off of the calibration fluid path. The host computer is also used to control the stop valve to open before the calibration process begins to make the calibration fluid path conductive; and, after the calibration is completed, control the stop valve to close to disconnect the calibration fluid path.

[0071] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for calibrating a mass flow controller, wherein at least one pressure sensor is provided on a fluid passage of the mass flow controller, characterized in that: The method comprises: controlling the fluid pressure upstream of the mass flow controller to reach a plurality of detection points in sequence, and obtaining the upstream fluid pressure value of the mass flow controller and the corresponding pressure detection value of the pressure sensor when the fluid pressure upstream of the mass flow controller reaches each of the detection points; According to the two upstream fluid pressure values ​​and the two pressure detection values ​​corresponding to each two adjacent detection points, a calculation formula for the corresponding relationship between the upstream theoretical fluid pressure value and the pressure detection value corresponding to each detection point interval is obtained; Writing the calculation formula corresponding to each detection point interval into the mass flow controller; The controlling the fluid pressure upstream of the mass flow controller to reach a plurality of detection points in sequence comprises: According to the set number of cycles, the same detection point is detected a corresponding number of times, wherein a single cycle is to control the fluid pressure upstream of the mass flow controller to increase from the detection point with the minimum pressure value to the detection point with the maximum pressure value, and then control the fluid pressure to decrease from the detection point with the maximum pressure value to the detection point with the minimum pressure value; The pressure detection value is an average of a detection value of a corresponding detection point of a corresponding pressure sensor during an increasing change in the fluid pressure upstream of the mass flow controller and a detection value of a corresponding detection point during a decreasing change in the fluid pressure; Alternatively, the calculation formula for each cycle is first obtained based on the detection values ​​of the pressure sensor corresponding to two adjacent detection points in each cycle, and then the calculation formulas corresponding to multiple cycles are averaged to obtain the final calculation formula.

2. The calibration method according to claim 1, characterized in that: The calibration method further includes: According to the target pressure range, a plurality of detection points and the number of cycles corresponding to the target pressure range are obtained from a database.

3. The calibration method according to claim 1, characterized in that: The calibration method further includes: When the difference between the detection value of the pressure sensor at the corresponding detection point during the increasing change of the fluid pressure and the detection value of the corresponding detection point during the decreasing change of the fluid pressure is greater than a first preset difference threshold, the calibration is stopped and the mass flow controller is determined to be unqualified.

4. The calibration method according to claim 3, characterized in that: The first preset difference threshold is between 0.4 kPa and 0.6 kPa.

5. The calibration method according to claim 1, characterized in that: The controlling the fluid pressure upstream of the mass flow controller to reach a plurality of detection points in sequence includes: The fluid pressure upstream of the mass flow controller is controlled so that the difference between the upstream fluid pressure value and each detection point in sequence is not greater than a second preset difference threshold.

6. The calibration method according to claim 5, characterized in that: The second preset difference threshold is less than 0.02 kPa.

7. The calibration method according to any one of claims 1 to 6, characterized in that: The calibration method further includes: Controlling the fluid pressure upstream of the mass flow controller to reach a test pressure, and obtaining the upstream fluid pressure value of the mass flow controller and the pressure detection value of the pressure sensor; Calculating the upstream theoretical fluid pressure value based on the pressure detection value of the pressure sensor according to the obtained calculation formula; The upstream theoretical fluid pressure value is compared with the upstream fluid pressure value. When the difference between the upstream theoretical fluid pressure value and the upstream fluid pressure value is greater than a third preset difference threshold, the mass flow controller is determined to be unqualified.

8. The calibration method according to any one of claims 1 to 6, characterized in that: The calculation formula is Y=a(X+b), where Y is the theoretical fluid pressure value upstream of the mass flow controller, X is the flow detection value of the pressure sensor, and a and b are constants.

9. A mass flow controller calibration system, characterized in that: The calibration system includes a host computer, a calibration fluid path and a pressure controller. The calibration fluid path has a calibration position for connecting to the mass flow controller to be measured. The host computer can control the pressure controller to change the fluid pressure upstream of the calibration position, and the host computer can implement the calibration method of the mass flow controller described in any one of claims 1 to 8.

Images