Pressure precision calibration method applied to multi-coil spring tube pressure gauge

Abstract

The application provides a pressure precision calibration method applied to a multi-coil spring tube pressure gauge, S1, before pressurization, an outer contour line of an outer coil tube body of the multi-coil spring tube is outlined by using a visual system, and a tube end position of the outer contour line is obtained; S2, a center of the outer contour line is determined, the tube end is taken as a 0-degree scale point, the outer contour line is divided and defined by 1-degree intervals to obtain N-degree scale points, wherein N is an integer value from 0 to 360, the arc length of each adjacent two scale points is calculated, and the arc lengths of all the arcs are added to obtain the total arc length from the 0-degree scale point to the 360-degree scale point; S3, the deflection angle values of each scale point under other pressure points are measured; S4, corresponding scale points matched with the deflection angle of the nominal pressure indicated by a dial plate are screened out, and a pointer is installed at the scale point position. The application avoids misjudgment of manual identification, and greatly improves production efficiency and product quality.

Description

Technical Field

[0001] This invention belongs to the field of accuracy calibration technology for fluid pressure measuring elements, and in particular relates to a method for calibrating the pressure accuracy of multi-turn Bourdon tubes. Background Technology

[0002] Multi-turn Bourdon tube pressure gauges are simple in structure and easy to install, and are often used to monitor the internal pressure of fire extinguishing containers. However, due to limitations in the materials, structure, and manufacturing process of their pressure sensing element, the multi-turn Bourdon tube, their pressure accuracy is difficult to calibrate using the same methods as traditional Bourdon tube pressure gauges, and they cannot be applied to high-precision pressure measurements. Currently, the calibration method commonly used by domestic pressure gauge manufacturers is as follows: after pressurization, observe the change in pressure at a certain position of the pre-installed pointer on the multi-turn Bourdon tube, and then select an appropriate dial based on the change. If no suitable dial is available, observe the angle at the next position, and so on. Because the range of positions is large and the available dial styles are limited, this method cannot cover all possibilities, requires complete manual identification, has a high workload and a high error rate, and cannot guarantee detection accuracy. Summary of the Invention

[0003] In view of this, the present invention proposes a pressure accuracy calibration method for multi-turn Bourdon tube pressure gauges, thereby solving the problems of needing to select multiple dials, complex manual operation, serious misjudgment, and poor calibration accuracy in the current pressure accuracy calibration process.

[0004] Pressure accuracy calibration method applied to multi-turn Bourdon tube pressure gauges:

[0005] S1. Before pressurization, use a vision system to outline the outer contour of the outer coil of the multi-turn spring tube and determine the position of the tube end of the outer contour.

[0006] S2. Determine the center of the outer contour line. With the pipe end as the 0° scale point, divide the outer contour line into N° scale points at 1° intervals, where N is an integer value from 0 to 360. Calculate the arc length between each two adjacent scale points and add up the arc lengths of all arcs to obtain the total arc length from the 0° scale point to the 360° scale point.

[0007] S3. Measure the deflection angle values ​​of each scale point under other pressure points;

[0008] S4. Select the corresponding scale point whose deflection angle value matches the deflection angle of the nominal pressure indicated by the dial, and install the pointer at the scale point.

[0009] Furthermore, in S1, the visual system distinguishes the grayscale difference between the outermost spring tube body of the multi-turn spring tube and the bottom background, and outlines the outer contour line along the edge of the grayscale difference.

[0010] Furthermore, the pipe end position of the outer contour line in S1 is obtained by the following method:

[0011] The outer contour line is divided into multiple pixels, and the coordinate values ​​of each pixel in the image are obtained. Then, the horizontal axis is used as the sequence of the number of pixels, and the vertical axis is the X or Y coordinate of the pixel. Two smooth curves formed by each pixel of the outer contour line in this coordinate system are obtained. The jump point on the two smooth curves, i.e. the pipe end position, is calculated by calculating the slope of the curves.

[0012] Furthermore, in S2, the outer contour line is fitted with a circle that approximates it, thereby determining the position of its center.

[0013] Furthermore, in S2, the pipe end is taken as the 0° scale point, and the line connecting this point and the center of the circle is defined as the 0° reference line; with the 0° reference line as the reference, rays are radiated outward from the center of the circle in 1° intervals, and the intersection with the circle fitted by the contour line is used to obtain each scale point.

[0014] The arc length between two adjacent scale points is obtained by using the two-point distance formula, which is the arc length of each segment. Then, the total arc length of the outer contour line is obtained by summing the arc lengths of each segment.

[0015] Furthermore, in S3, a specified pressure is applied to the multi-turn spring tube, and the outer contour line of the outer coil of the multi-turn spring tube is drawn using a vision system under the pressure value, and the tube end position of the outer contour line under the pressure value is obtained.

[0016] Based on the arc length between each two adjacent scale points calculated before pressurization, starting from the pipe end position of the outer contour line under this pressure value, the current position of each scale point on the outer contour line under this pressure value is calculated.

[0017] By calculating the position of each scale point on the outer contour line before pressurization and the deflection angle of its position on the outer contour line after pressurization relative to the center of the circle, the deflection angle value of each scale point under this pressure value can be obtained.

[0018] This invention avoids misjudgments caused by manual identification, greatly improving production efficiency and product quality. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram illustrating the principle of the present invention;

[0021] Figure 2 A schematic diagram illustrating the use of a vision system to outline the outer contour of a multi-turn Bourdon tube;

[0022] Figure 3 This is a schematic diagram of two smooth curves formed by each pixel of the outer contour line.

[0023] Figure 4 A schematic diagram for determining the jump point, i.e., the position of the pipe end;

[0024] Figure 5 This is a comparative diagram showing how the arcs between adjacent scale points approximate the lines connecting them. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0026] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0027] First, we need to clarify two key premises:

[0028] First premise: During a stable and linear pressure change process, the changes in adjacent positions on the outer coil of the multi-turn Bourdon tube are not abrupt but continuous.

[0029] The second premise is that, throughout the entire pressurization process, although the outer coil of the multi-turn Bourdon tube rotates, the relative tube lengths between these positions remain constant. That is, regardless of how the Bourdon tube deforms, the arc length between adjacent points will not change.

[0030] like Figure 1 As shown: Assuming AB are two adjacent points on the Bourdon tube, then:

[0031] ∠AOC-∠BOC≈∠A'OC-∠B'OC;

[0032] Arc length AB = Arc length A'B'.

[0033] Under the above two premises, with the aid of visual monitoring system and calculation software, we can measure the rotation angle at various positions on the outer coil of the multi-turn Bourdon tube, and then select the appropriate pointer installation position based on the detected rotation angle value.

[0034] The specific content of the method of the present invention is as follows:

[0035] Before pressurization, i.e., under standard atmospheric pressure.

[0036] S1. Use a vision system to outline the outer contour of the outer coil of the multi-turn spring tube, hereinafter referred to as the outer contour, and determine the tube end position of the outer contour under this pressure state.

[0037] Specifically,

[0038] S101, such as Figure 1 As shown, the visual system distinguishes the grayscale difference between the outermost spring tube body (i.e., the outer coil body) and the bottom background of the multi-turn spring tube, and the outer contour line is drawn along the edge of the grayscale difference.

[0039] S102. Divide the outer contour line into multiple pixel points, obtain the coordinate values ​​of each pixel point in the image, and then use the horizontal axis as the sequence of pixel points and the vertical axis as the X or Y coordinate of the pixel point to obtain two smooth curves formed by each pixel point of the outer contour line in this coordinate system (e.g., ...). Figure 2 As shown in the figure, it is easy to see that there is a clear jump point in the two smooth curves. This jump point is the position of the tube end of the outer coil of the multi-turn spring tube.

[0040] S103. The jump point, i.e., the pipe end position, is calculated:

[0041] The jump point can be calculated by calculating the slope of the curve, as follows:

[0042] The slope of each point can be calculated using its own coordinates and the coordinates of its adjacent points:

[0043] K1 = (Y2 - Y1) / (X2 - X1)

[0044] K2 = (Y3 - Y2) / (X3 - X2)

[0045] K3 = (Y4 - Y3) / (X4 - X3).

[0046] Let the jump position be K. n We can derive abs(K) n )<abs(K n+1 And abs(K) n )<abs(K n-1 );

[0047] Based on the judgment result, the following can be obtained: Figure 4 The green marker at the end point indicates the pipe end, thus revealing the pipe end location.

[0048] S2. Determine the center of the outer contour line in S1. Using the pipe end as the 0° scale point, divide the outer contour line into N° scale points at 1° intervals, where N is an integer value from 0 to 360. Calculate the arc length between each pair of adjacent scale points, and add up the arc lengths of all arcs to obtain the total arc length L from the 0° scale point to the 360° scale point. 0N .

[0049] Specifically,

[0050] S201. Fit an approximate circle to the outer contour line and determine the position of its center.

[0051] S202. Taking the pipe end as the 0° scale point, the line connecting this point and the center of the circle is defined as the 0° reference line. Using the 0° reference line as a reference, radiate rays outward from the center of the circle clockwise at 1° intervals, intersecting the circle fitted by the contour line to obtain various scale points, namely the 1° scale point, the 2° scale point, ..., the N° scale point, where the maximum value of N is 360.

[0052] S203. Calculate the total arc length: (e.g.) Figure 5 As shown, since the scale points are closely spaced, it can be assumed that the arc length between any two adjacent scale points is approximately a straight line. Knowing the coordinates of each scale point, the arc length (L) of each segment can be determined using the distance formula between two points. 01 L 12 L 23 L 34 L 45 ...), and then summing up the arc lengths of each segment gives the total arc length L of the outer contour line. 0N .

[0053] S3. Measure the deflection angle values ​​at each scale point (position) under other pressure points:

[0054] S301. Apply a specified pressure to the multi-turn Bourdon tube, and use the method in S1 to use a vision system to outline the outer contour of the outer coil of the multi-turn Bourdon tube under the pressure value, and obtain the tube end position of the outer contour under the pressure value.

[0055] S302. As mentioned in the second premise above, the arc length between two adjacent scale points (i.e. two adjacent positions) will not change after pressurization. Therefore, based on the arc length value between each two adjacent scale points calculated before pressurization, starting from the pipe end position of the outer contour line under the pressure value, the current position of each scale point on the outer contour line under the pressure value is calculated.

[0056] S303. Calculate the position of each scale point on the outer contour line before pressurization and the deflection angle of the position on the outer contour line after pressurization relative to the center of the circle. This will give you the deflection angle value of each scale point under the pressure value.

[0057] S4. Select the corresponding scale point whose deflection angle value matches the deflection angle of the nominal pressure indicated on the dial, and install the pointer at that scale point.

[0058] For example:

[0059] Example 1: Using the above method, pressure was applied to the No. 1 multi-turn Bourdon tube at 3.6MPa, 4.2MPa, and 5.3MPa respectively. Finally, it was found that at the 115° mark on its outer ring, the deflection angles at 3.6, 4.2, and 5.3MPa were 75°, 85°, and 135° respectively, which are consistent with the corresponding deflection angles of 3.6, 4.2, and 5.3 on the dial. Therefore, it can be determined that installing the pointer at the 115° mark on the outer contour line of the No. 1 tube before pressure is applied can match the dial used.

[0060] Example 2: Using the above method, pressure was applied to the No. 2 multi-turn Bourdon tube at 3.6MPa, 4.2MPa, and 5.3MPa respectively. Finally, it was found that at the 227° mark on its outer ring, the deflection angles at 3.6, 4.2, and 5.3MPa were 75°, 85°, and 135° respectively, which are consistent with the corresponding deflection angles of 3.6, 4.2, and 5.3 on the dial. Therefore, it can be determined that the pointer installed at the 227° mark on the outer contour line of the No. 1 tube before pressure is applied can match the dial used.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calibrating the pressure accuracy of a multi-turn Bourdon tube pressure gauge, characterized in that, S1. Before pressurization, use a vision system to outline the outer contour of the outer coil of the multi-turn spring tube and determine the position of the tube end of the outer contour. S2. Determine the center of the outer contour line. With the pipe end as the 0° scale point, divide the outer contour line into N° scale points at 1° intervals, where N is an integer value from 0 to 360. Calculate the arc length between each two adjacent scale points and add up the arc lengths of all arcs to obtain the total arc length from the 0° scale point to the 360° scale point. S3. Measure the deflection angle values ​​of each scale point under other pressure points; S4. Select the corresponding scale point whose deflection angle value matches the deflection angle of the nominal pressure indicated by the dial, and install the pointer at the scale point.

2. The pressure accuracy calibration method for multi-turn Bourdon tube pressure gauges according to claim 1, characterized in that, In S1, the visual system distinguishes the grayscale difference between the outermost spring tube body of the multi-turn spring tube and the bottom background, and outlines the outer contour line along the edge of the grayscale difference.

3. The pressure accuracy calibration method for multi-turn Bourdon tube pressure gauges according to claim 1, characterized in that, The pipe end position of the outer contour line in S1 is obtained by the following method: The outer contour line is divided into multiple pixels, and the coordinate values ​​of each pixel in the image are obtained. Then, the horizontal axis is used as the sequence of the number of pixels, and the vertical axis is the X or Y coordinate of the pixel. Two smooth curves formed by each pixel of the outer contour line in this coordinate system are obtained. The jump point on the two smooth curves, i.e. the pipe end position, is calculated by calculating the slope of the curves.

4. The pressure accuracy calibration method for multi-turn Bourdon tube pressure gauges according to claim 1, characterized in that, In S2, the outer contour line is fitted with a circle that approximates it, thereby determining the position of its center.

5. The pressure accuracy calibration method for multi-turn Bourdon tube pressure gauges according to claim 1, characterized in that, In S2, the pipe end is taken as the 0° scale point. The line connecting this point and the center of the circle is defined as the 0° reference line. Based on the 0° reference line, the radiating rays are rotated outward from the center of the circle clockwise at intervals of 1°. The intersection with the circle fitted by the contour line is used to obtain each scale point. The arc length between two adjacent scale points is obtained by using the two-point distance formula, which is the arc length of each segment. Then, the total arc length of the outer contour line is obtained by summing the arc lengths of each segment.

6. The pressure accuracy calibration method for multi-turn Bourdon tube pressure gauges according to claim 1, characterized in that, In S3, a specified pressure is applied to the multi-turn spring tube, and the outer contour line of the outer coil of the multi-turn spring tube is drawn using a vision system under the pressure value, and the tube end position of the outer contour line under the pressure value is obtained. Based on the arc length between each two adjacent scale points calculated before pressurization, starting from the pipe end position of the outer contour line under this pressure value, the current position of each scale point on the outer contour line under this pressure value is calculated. By calculating the position of each scale point on the outer contour line before pressurization and the deflection angle of its position on the outer contour line after pressurization relative to the center of the circle, the deflection angle value of each scale point under this pressure value can be obtained.

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