An automatic weighing system and its sampling method

Abstract

The purpose of this invention is to provide a system and method for achieving high-precision automatic sampling without cross-contamination of samples. This invention discloses an automatic weighing system, including a sampling module, a weighing module, and a cleaning module. The sampling module includes a sampling rod and a driving device. The driving device controls the rotation and movement of the sampling rod. A detachable sampling head is provided at the bottom of the sampling rod, and the sampling head has a groove for sampling. The weighing module is used to weigh the mass of the sample taken by the sampling rod. The cleaning module is used to clean the sampling rod. This invention further discloses the sampling method of the above-mentioned automatic weighing system. The advantages of this invention are: It constructs a piecewise fitting function for samples of different densities to better control the error between the predicted and actual measured values ​​of the sampling quantity, thereby ensuring sampling accuracy; it accurately controls the sampling centrifugation speed and time, solving the problem that existing automated operations require changing different sampling rods when the sample density is different.

Description

Technical Field

[0001] This invention relates to an automatic sampling and weighing device for powder samples. Background Technology

[0002] Currently, in wet chemical analysis, the first step in analyzing powder samples is to take samples, then weigh the samples to ensure an accurate sample volume, followed by acid digestion, and finally analysis of the solution samples.

[0003] In the above process, the conventional procedure involves manually inserting a sample spoon into the sample vial for micro-sampling. The sample volume is typically between 0.1g and 0.5g, with a control precision of 0.00001g. For samples with higher density, the volume is relatively small, and the sample tube used to hold the powder has a small diameter. Therefore, this operation is currently performed manually for precise sampling control. After sampling, before taking the next sample, the sample spoon needs to be wiped clean with an alcohol swab or similar device to prevent any residual sample from contaminating the next sample. The alcohol swab becomes a contaminant after wiping and needs to be disposed of.

[0004] If the number of samples is large but the number of samples taken for analysis is small, the operation requires high skill and intensity from personnel, resulting in low control accuracy and impacting the accuracy of sample analysis. Currently, there is no automated system for high-precision sampling and weighing of powder samples in analytical operations. With the increasing demand for automation in laboratory chemical analysis, a high-precision automated weighing system for micro-powder samples is a key breakthrough.

[0005] Traditional automated operation designs simply use robotic arms to control sample spoons, simulating manual sampling to achieve automation. However, this approach suffers from low sampling accuracy, requiring the use of different sized sample spoons for samples of varying densities, making the operation complex and difficult to clean. Some manufacturers also use robotic arms to simulate human hand shaking and weigh samples by tilting them, but this method has poor control accuracy and results in a large sample scattering area, making it impossible to place the samples into sample tubes used in conventional chemical analysis. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned difficulties and provide a system and sampling method that can achieve high-precision automatic sampling and prevent cross-contamination of samples.

[0007] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: an automatic weighing system, comprising a sampling module, a weighing module, and a cleaning module. The sampling module includes a sampling rod and a driving device. The driving device is used to control the rotation and movement of the sampling rod. The bottom of the sampling rod is provided with a detachable sampling head, and the sampling head is provided with a groove for sampling. The weighing module is used to weigh the mass of the sample taken by the sampling rod. The cleaning module is used to clean the sampling rod. The sampling head includes a connecting part, a sampling part, and a guiding part. One end of the connecting part is connected to the sampling rod by a thread or a snap fastener, and the other end is provided with a sampling area. The sampling area has the groove, and the outer edge of the groove is provided with a slope. The lower end of the sampling area is provided with a conical guiding part. The functional relationship between the maximum sampling amount g1 of the sampling part and the sampling area is:

[0008]

[0009] h is the depth of the groove, α is the angle between the slope and the center line of the sampling rod, β is the natural angle of packing of the powder sample to be tested, D is the outer diameter of the sampling area, and n1 is the density of the powder sample to be tested.

[0010] Preferably, the driving device includes a robotic arm, a connecting plate, and a motor. The robotic arm is used to control the up, down, left, and right movement of the connecting plate. The connecting plate is equipped with a motor, and a bearing mounting seat is fixed to the motor via a coupling. The bearing mounting seat is equipped with a bearing for connecting a sampling rod.

[0011] Preferably, both the weighing module and the cleaning module are mounted on a table. The weighing module includes a balance with a weighing tube for collecting powder samples from the sampling rod. The cleaning module is equipped with a high-pressure purging device or a water cleaning device for cleaning the sampling rod.

[0012] The sampling method of the above-mentioned automatic weighing system:

[0013] (A1) The sampling rod is rotated and inserted into the sample bottle containing the powder sample by the driving device. The powder sample submerges the sampling head on the sampling rod, so that the groove on the sampling head is filled with the sample.

[0014] (A2) The sampling rod is rotated by the driving device and centrifugally rotated at a certain speed. After rotating for a period of time, part of the sample on the surface of the sampling tank is centrifuged and removed from the sampling tank. The mass of the remaining sample in the sampling tank is the sampled sample.

[0015] (A3) The sampling rod is lifted by the drive device and moved to the weighing module. Then the driving device is controlled to drive the sampling rod to rotate at high speed so that the sample in the sampling head groove is fully thrown out and the sampling rod stops.

[0016] (A4) The sampling rod is moved to the cleaning module in the cleaning area by the driving device, and then removed after cleaning for the next use;

[0017] (A5) The weighing module calculates the weight of the sample.

[0018] Preferably, based on the high-precision sampling requirements, fitting functions for each segment of samples with different densities are constructed within multiple sampling ranges. The smaller the range of the segment, the higher the sampling accuracy. When the sampling accuracy is within the range of 0.1g, the prediction error between the fitting function corresponding to each segment and the actual sample mass obtained is within the range of 0.001% of the absolute value.

[0019] The sampling range for density n2 is [g 20 g 21 Let it be divided into N segments, with each segment having a sampling size g. 22 for:

[0020] Where 0≤g 21 -g 20 ≤0.1g.

[0021] Preferably, based on the sampling amount g2 in steps A1 and A2 and the sample density n2, the function whose segmentation interval is set to [g2-m1, g2+m2] is: g2=f2(s,t), where N is the number of segmented intervals, where the function g2 = f2(s, t) is fitted using the following polynomial:

[0022] g2=a1+a2s+a3t+a4s 2 +a5st+a6t 2 +a7s 3 +a8s 2 t+a9st 2 +

[0023] a 10 t 3 +a 11 s 4 +a 12 s 3 t+a 13 s 2 t 2 +a 14 st 3 +a 15 t 4 +a 16 s 5 +

[0024] a 17 s 4 t 1+a 18 s 3 t 2 +a 19 s 2 t 3 +a 20 s 1 t 4 +a 21 t 5 a1, a2, a3, a4, a5, a6, a7, a8, a9, a 10 ,a 11 ,a 12 ,a 13 ,a 14 ,a 15 ,a 16 ,a 17 ,a 18 ,a 19 ,a 20 ,a 21 is an undetermined coefficient, where s is the centrifugal rotation speed in step A2 and t is the centrifugal rotation time in step A2.

[0025] Preferably, the fitting process needs to control its accuracy, and the relative error δ is used to determine the accuracy: Among them, g i It is the actual weighing value of the i-th sample, g j It is the fitted approximation of the i-th sample. Using polynomial fitting, the relative error can be controlled within 0.001%.

[0026] Preferably, based on the piecewise fitting function of samples with different densities and the corresponding sample mass, the segment interval to which it belongs is determined, the corresponding sampling head is selected, the corresponding sampling centrifugation speed and centrifugation time are obtained, and the corresponding sampling control parameters are set.

[0027] Compared with the prior art, the advantages of the present invention are:

[0028] 1. Accurately control the sampling and centrifugation speed and time, solving the problem that existing automated operations require changing different sampling rods when the sample density is different;

[0029] 2. Based on samples of different densities, construct piecewise fitting functions to better control the error between the predicted and actual measured values ​​of the sampling amount, thereby ensuring sampling accuracy;

[0030] 3. The cleaning module can automatically clean the sampling rod, which is more convenient and easier to automate than the traditional sample spoon sampling method that requires wiping and cleaning. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the present invention;

[0032] Figure 2 This is a schematic diagram of the sampling head at the bottom of the sampling rod of the present invention. Detailed Implementation

[0033] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0034] An automatic weighing system includes a sampling module, a weighing module, and a cleaning module. The sampling module includes a sampling rod 7 and a driving device. The driving device includes a robotic arm 1, a connecting plate 2, and a motor 3. The robotic arm controls the up, down, left, and right movement of the connecting plate. The motor is fixed to the connecting plate, and a bearing mounting seat 5 is fixed to the motor via a coupling 4. The bearing mounting seat has a bearing for connecting the sampling rod. The driving device controls the rotation and movement of the sampling rod through a program.

[0035] The bottom of the sampling rod is provided with a detachable sampling head, which includes a connecting part 71, a sampling part 72, and a guiding part 73. One end of the connecting part is connected to the sampling rod by a thread or a snap fastener, and the other end is provided with a sampling area. The sampling area has a groove 721, and the outer edge of the groove is provided with a slope 722. The lower end of the sampling area is provided with a tapered guiding part. The maximum sampling amount g1 of the sampling part and the functional relationship between the sampling area are as follows:

[0036]

[0037] h is the depth of the groove, α is the angle between the slope and the centerline of the sampling rod, β is the angle of natural packing of the powder sample, D is the outer diameter of the sampling area, and n1 is the density of the powder sample. Assuming the density n is known... 11 The maximum sample size in the segmented interval is g 12 The volume V2 of the sampling groove of the sampling rod can be calculated. Then, by setting the outer diameter of the sampling area to D1 and the depth of the sampling groove to α1, the height h1 of the sampling groove can be calculated, and finally the size parameters of the sampling rod can be determined.

[0038] If a sample with density n2 needs to take g2, select its segmented interval [g2-m1, g2+m2], where Select the corresponding sampling rod and sampling slot. The experimental data should consist of at least 21 sets. To ensure consistency, each set of identical experimental data should be tested three times using the same test parameters.

[0039] The weighing module is used to weigh the mass of the sample taken by the sampling rod, and the cleaning module 11 is used to clean the sampling rod. Both the weighing module and the cleaning module are located on the system platform 10. The weighing module includes a balance 9 with a weighing tube 8 on it. The weighing tube is used to collect the powder sample on the sampling rod. The cleaning module is equipped with a high-pressure purging device or a water cleaning device for cleaning the sampling rod.

[0040] Sampling method of automatic weighing system:

[0041] (A1) The sampling rod is rotated and inserted into the sample bottle containing the powder sample by the driving device. The powder sample submerges the sampling head on the sampling rod, so that the groove on the sampling head is filled with the sample.

[0042] (A2) The sampling rod is rotated by the driving device and centrifugally rotated at a certain speed. After rotating for a period of time, part of the sample on the surface of the sampling tank is centrifuged and removed from the sampling tank. The mass of the remaining sample in the sampling tank is the sampled sample.

[0043] (A3) The sampling rod is lifted by the drive device and moved to the weighing module. Then the driving device is controlled to drive the sampling rod to rotate at high speed so that the sample in the sampling head groove is fully thrown out and the sampling rod stops.

[0044] (A4) The sampling rod is moved to the cleaning module in the cleaning area by the driving device, and then removed after cleaning for the next use;

[0045] (A5) The weighing module calculates the weight of the sample.

[0046] Repeat step A1 to fit each segment within multiple sampling ranges based on samples of different densities. The smaller the segment range, the higher the sampling accuracy. When the sampling accuracy is within 0.1g, the absolute value of the prediction error of the fitting function corresponding to each segment based on the actual sample amount is within 1%.

[0047] Furthermore, based on the maximum sampling quantity g1 of the sampling section and the functional relationship of the sampling area, a fitting method is used to fit the test data and methods described in the above steps to a corresponding function g = f(s, t). The function g = f(s, t) is fitted using the following polynomial:

[0048] g = a1 + a2s + a3t + a4s 2 +a5st+a6t 2 +a7s 3 +a8s 2 t+a9st 2 +

[0049] a 10 t 3 +a 11s 4 +a 12 s 3 t+a 13 s 2 t 2 +a 14 st 3 +a 15 t 4 +a 16 s 5 +

[0050] a 17 s 4 t 1 +a 18 s 3 t 2 +a 19 s 2 t 3 +a 20 s 1 t 4 +a 21 t 5

[0051] in,

[0052] a1, a2, a3, a4, a5, a6, a7, a8, a9, a 10 ,a 11 ,a 12 ,a 13 ,a 14 ,a 15 ,a 16 ,a 17 ,a 18 ,a 19 ,a 20 ,a 21 The coefficients are undetermined for the polynomial, and some coefficients may be zero.

[0053] If the sample size is g2 and the sample density is n2, the fitting function with a segmented interval of [g2-m1, g2+m2] is defined as follows:

[0054] g2 = f2(s, t)

[0055] Fitting requires controlling its accuracy; the relative error δ is used to determine the accuracy:

[0056]

[0057] Among them, g i It is the actual weighing value of the i-th sample, g j It is the fitted approximation of the i-th sample. Using a 5th-order polynomial fitting, the relative error can be controlled within 0.001%.

[0058] If the sample size is g2 and the sample density is n2, and the segmentation interval is set to [g2-m1, g2+m2], the sampling accuracy can be determined as follows:

[0059]

[0060] Among them, g i2 The actual weighing value of the i-th sample in the segmented interval [g2-m1, g2+m2] is g. j2 It is the approximate value of the i-th sample in the segmented interval [g2-m1, g2+m2]. By using polynomial fitting, the relative error can be controlled within 0.001%.

[0061] The above description is only a specific embodiment of the present invention, but the technical features of the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. An automatic weighing system, comprising a sampling module, a weighing module, and a cleaning module, characterized in that, The sampling module includes a sampling rod and a driving device. The driving device controls the rotation and movement of the sampling rod. A detachable sampling head is located at the bottom of the sampling rod, and the sampling head has a groove for sampling. The weighing module weighs the mass of the sample taken by the sampling rod. The cleaning module cleans the sampling rod. The sampling head includes a connecting part, a sampling part, and a guiding part. One end of the connecting part is connected to the sampling rod via a thread or snap-fit, and the other end has a sampling area. The sampling area has the groove, and the outer edge of the groove has a slope. A tapered guiding part is located at the lower end of the sampling area. The maximum sampling amount g1 of the sampling part and the functional relationship between the sampling area and the sampling volume g1 are as follows: h is the depth of the groove, α is the angle between the slope and the center line of the sampling rod, β is the natural angle of packing of the powder sample to be tested, D is the outer diameter of the sampling area, and n1 is the density of the powder sample to be tested.

2. The automatic weighing system according to claim 1, characterized in that, The driving device includes a robotic arm, a connecting plate, and a motor. The robotic arm is used to control the up, down, left, and right movement of the connecting plate. The connecting plate is equipped with a motor, and a bearing mounting seat is fixed to the motor via a coupling. The bearing mounting seat is equipped with a bearing for connecting a sampling rod.

3. The automatic weighing system according to claim 1, characterized in that, Both the weighing module and the cleaning module are mounted on a table. The weighing module includes a balance with a weighing tube for collecting powder samples from the sampling rod. The cleaning module is equipped with a high-pressure purging device or a water cleaning device for cleaning the sampling rod.

4. A sampling method for an automatic weighing system according to any one of claims 1-3, characterized in that, (A1) The sampling rod is rotated and inserted into the sample bottle containing the powder sample by the driving device. The powder sample submerges the sampling head on the sampling rod, so that the groove on the sampling head is filled with the sample. (A2) The sampling rod is rotated by the driving device and centrifugally rotated at a certain speed. After rotating for a period of time, part of the sample on the surface of the sampling tank is centrifuged and removed from the sampling tank. The mass of the remaining sample in the sampling tank is the sampled sample. (A3) The sampling rod is lifted by the drive device and moved to the weighing module. Then the driving device is controlled to drive the sampling rod to rotate at high speed so that the sample in the sampling head groove is fully thrown out and the sampling rod stops. (A4) The sampling rod is moved to the cleaning module in the cleaning area by the driving device, and then removed after cleaning for the next use; (A5) The weighing module calculates the weight of the sample.

5. The sampling method of an automatic weighing system according to claim 4, characterized in that, Based on the requirements for high-precision sampling, fitting functions for each segment were constructed for samples of different densities across multiple sampling ranges. The smaller the segment range, the higher the sampling accuracy. When the sampling accuracy is within 0.1g, the absolute value of the prediction error between the fitting function corresponding to each segment and the actual sample mass is within 0.001%. The sampling range for density n2 is [g 20 g 21 Let it be divided into N segments, with each segment having a sampling size g. 22 for: Where 0≤g 21 -g 20 ≤0.1g.

6. The sampling method of an automatic weighing system according to claim 5, characterized in that, Based on the sample size of g2 in steps A1 and A2, and the sample density n2, Let the function whose segmented interval is [g2-m1, g2+m2] be: g2=f2(s,t), where N is the number of segmented intervals. Its function g2 = f2(s, t) is fitted using the following polynomial: g2a1+a2s+a3t+a4s 2 +a5st+a6t 2 +a7s 3 +a8s 2 t+a9st 2 + a 10 t 3 +a 11 s 4 +a 12 s 3 t+a 13 s 2 t 2 +a 14 st 3 +a 15 t 4 +a 16 s 5 + a 17 s 4 t 1 +a 18 s 3 t 2 +a 19 s 2 t 3 +a 20 s 1 t 4 +a 21 t 5 a1, a2, a3, a4, a5, a6, a7, a8, a9, a 10 ,a 11 ,a 12 ,a 13 ,a 14 ,a 15 ,a 16 ,a 17 ,a 18 ,a 19 ,a 20 ,a 21 is an undetermined coefficient, where s is the centrifugal rotation speed in step A2 and t is the centrifugal rotation time in step A2.

7. The sampling method of an automatic weighing system according to claim 6, characterized in that, Fitting requires controlling its accuracy; here, the relative error δ is used to determine the accuracy: Among them, g i It is the actual weighing value of the i-th sample, g j It is the fitted approximation of the i-th sample. Using polynomial fitting, the relative error can be controlled within 0.001%.

8. The sampling method of an automatic weighing system according to claim 6, characterized in that, Based on the piecewise fitting function of samples with different densities and the corresponding sample mass, determine the segment interval to which it belongs, select the corresponding sampling head, obtain the corresponding sampling centrifugation speed and centrifugation time, and set the corresponding sampling control parameters.

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