Current Issue

2024, Volume 68,  Issue 4

Measurement Methods and Techniques
Abstract:
Accurate acquisition of the physical quantities to be measured is a prerequisite for achieving precise measurements. Currently, high-precision and expensive CNC gear measuring instruments are widely used. However, for micro gears with a modulus less than 0.1 mm and a diameter less than 1 mm, traditional contact measurement methods cannot measure the complete tooth profile due to the narrow tooth groove width. Optical measurement methods also face the problem of not being able to obtain tooth root data due to tooth occlusion and tooth surface inclination limitations. In response to this situation, a high-precision measurement method for micro gears based on white light interferometry is proposed. Real-time monitoring of the micro gear end face tilt is achieved based on the appearance order of interference patterns, ensuring the extraction accuracy of the gear profile. The gear center is determined based on the three-dimensional point cloud data of the end face, effectively improving the gear centering accuracy. The white light interferometry measurement principle for micro gears, the end face leveling model, and the gear error calculation method are introduced in detail. Experimental results show that this method can achieve high-precision measurement of micro gears, providing an effective means to solve the precision measurement problem of micro gears.
Abstract:
As one of the key components of heavy-duty electric locomotives, the bogie is closely related to the operational and safety performance of these locomotives. In the design and manufacturing process of bogies, there are problems such as ineffective traceability and insufficient detection methods in large-scale specialized testing devices, including bogie rolling vibration test benches. Moreover, during the testing process, the measurement results are inevitably affected by factors such as load effects, mechanical wave interference, locomotive vibration, and wheel hub distortion. The existing traceability methods for bogie values adopt offline calibration, ignoring the influence of factors such as actual installation position, electromagnetic interference, and environmental disturbance, making calibration data difficult to apply. This study analyzes the basic structure and working principle of the rolling vibration test bench for heavy-duty electric locomotive bogies and summarizes a series of technical indicators that can comprehensively and objectively reflect the measurement characteristics of the test bench. The calibration items and specific testing methods of the test bench are clarified, and the most critical performance indicator, torque, is selected for measurement uncertainty analysis. Finally, three test benches developed by CRRC Zhuzhou Machinery Co., Ltd. are selected for experimental verification, proving that the proposed calibration method for the test benches is scientific and reasonable.
Abstract:
To better control large field of view active optical telescopes, this paper explains the basic principles of detecting and calibrating the adjustment components in telescopes based on internal and external measurement systems. Error analysis is performed on the calibration process of large field of view active optical telescopes, and the principle of the detection method for motion components of large field of view active optical telescopes is demonstrated through desktop experiments. Non-diffractive uniform beam splitting is achieved, overcoming the disadvantages of diffractive beam splitting, such as multiple stray fringes and small splitting angles. The dispersion angle is higher than 100°, with an accuracy better than 15 µm and an angular accuracy better than 3″. The calibration accuracy based on wavefront sensing is better than 10 µm, which can effectively improve the calibration accuracy of the adjustment elements of large-aperture, large field of view telescopes and ultimately enhance the imaging quality of the telescopes.
Abstract:
Resistance strain sensors have a wide range of types and applications and are commonly used in industries such as bridge and tunnel construction, building, aerospace, etc., to monitor the structural health of various systems. Therefore, it is essential to reasonably evaluate the dynamic characteristics of resistance strain sensors. This article discusses and analyzes the characteristics of resistance strain sensors and the description of metrological characteristics in relevant domestic and international standards and specifications. Considering the current status of metrological calibration of resistance strain sensors, this paper proposes a method for calibrating the dynamic characteristics of resistance strain sensors using existing vibration measuring devices. This method is based on an existing vibration standard device, where a dynamic signal analyzer collects vibration table signals and strain sensor signals, and analyzes the measurement signals to obtain dynamic sensitivity, thus completing the calibration of the sensor's dynamic characteristics. Experiments have verified the feasibility and good repeatability of this method. Finally, the data processing process is explained, and the uncertainty of the sensor's dynamic sensitivity is evaluated.
Abstract:
During the production and transportation of Gas-Insulated Transmission Lines (GIL), internal defects may occur, leading to localized partial discharge faults during operation, accompanied by abnormal vibration and sound signals. When GIL malfunctions, it not only causes serious damage to the equipment itself but also poses a threat to the stable operation of the power system. This paper studies a method for detecting partial discharge faults in GIL based on vibration signals, which can accurately identify specific units and locations of the faults. The characteristics of vibration signals in GIL localized partial discharge fault states are analyzed. By processing and identifying signals collected from simulated experiments and on-site tests, the identification method has been optimized, enabling accurate and effective determination of whether GIL has experienced localized partial discharge faults.
Abstract:
To precisely measure the beam non-parallelism error of photoelectric autocollimators, a method based on a pentaprism has been proposed in this paper. By using a pentaprism, the measurement optical path can be optimized, thereby reducing the influence of surface shape irregularities of the mirror required in the detection process. The error of the non-parallel beam of the photoelectric autocollimator has been quantitatively analyzed, and different methods of beam parallelism measurement are compared experimentally. The results show that the difference between the pentaprism method and using a mirror with a curvature of less than 5×10−5 m−1 is less than 0.1″, which is far superior to the traditional measurement method using a mirror with average flatness. Moreover, the repeatability of the pentaprism method can reach 0.1″. The pentaprism method reduces the system error and improves the measurement accuracy of the beam parallelism of the photoelectric autocollimator.
Abstract:
The accuracy of portable uric acid analyzers directly affects the daily monitoring of uric acid in patients with gout and hyperuricemia. Due to the lack of calibration standards for these analyzers, it is necessary to establish a calibration protocol. Based on the developed calibration device for portable uric acid analyzers, a calibration method is proposed, and technical indicators are determined. The method is verified through calibration cases, and relevant influencing factors are analyzed. According to the calibration method, the verification results of the indication error and repeatability of the portable uric acid analyzer meet the technical requirements. The successfully established calibration method for portable uric acid analyzers can provide a useful reference for the development of the "Calibration Specification for Portable Uric Acid Analyzers" and promote the traceability and standardization of portable uric acid analyzers.
Research Progress
Abstract:
Ultrasonic flow meters demonstrate high precision and instantaneous measurement capabilities in flow measurement, showing significant application potential. They are of great importance for safe oil and gas storage, low-loss transportation, and fair settlement. This paper analyzes the working mechanism of high-precision ultrasonic flow meters based on four flow calculation principles: time difference method, frequency method, cross-correlation method, and Doppler method. The influence of flow velocity and temperature on flow measurement accuracy is revealed from three perspectives: turbulence characteristics, instrument structure, and environmental factors. The interference of meter geometry changes on the flow velocity field is also discussed. This paper summarizes the error factors of ultrasonic flow meters and the technical methods to reduce errors, providing ideas and guidance for the innovation of high-precision flow meter technology through research and prospect.
Impact Studies in Metrology
Abstract:
When conducting drug experiments on cells cultured in vitro, drug treatment can cause cell death, and different methods for detecting cell survival rates can impact the experimental results. This study uses HeLa cells as the experimental object and treats the cells with different concentrations of cisplatin. The cell survival rates detected with or without floating cells in the old culture medium are compared. The experimental results indicate that when using the CCK-8 method to detect the cell survival rates in 96-well and 24-well plates, the cell survival rates of the experimental group without removing the old culture medium are higher than those of the experimental group with the old culture medium removed. At a cisplatin concentration of 0.625 μM, there is a significant difference in cell survival rates between the experimental groups with and without the removal of the old medium. In 6-well plates and 100 mm dishes, a cell counter is used to detect the floating cells in the cell culture medium after drug application, and the presence of viable cells among the floating cells in the medium is found. The results suggest that the floating viable cells in the culture medium after drug treatment can affect the accuracy of the cell drug experiment results, and removing the old culture medium will remove these viable cells.
Abstract:
The mass of the special small weights used in liquid-medium piston gauges is calculated with reference to the effective area of the zero-pressure piston, while the mass of the large weights only considers the deformation of the piston system caused by loading the large weights. As a result, the actual pressure measured by the piston gauge loaded with nominal pressure weights is less than the nominal pressure. Based on the basic principles of piston pressure gauges, a measurement value correction model for liquid-medium piston gauges with a measurement upper limit of 25 MPa and above is derived. The results of the relative pressure correction values for piston gauges with upper measurement limits of 60 MPa and 250 MPa show that the absolute value of the relative pressure correction value increases nearly linearly with the number of small weights loaded but exhibits a nonlinear increase with a gradually weakening trend as the number of large weights loaded increases. The limit value of the relative pressure correction value is proportional to the pressure deformation coefficient and the upper measurement limit of the piston gauge. Overall, the influence of small weights on the relative pressure correction value is greater than that of large weights, and the relative pressure correction value reaches an extreme value at the pressure measurement point with the largest number of small weights loaded near the upper limit of the piston measurement. The relative pressure correction limit of the 250 MPa piston is −5.17×10−5, exceeding the maximum allowable error of the 0.005-level piston gauge. Based on the limitation of the maximum tolerance of the special weight mass, the output measurement values of 25 MPa piston gauges of grade 0.01 and above and 250 MPa piston gauges of grade 0.02 and above must be corrected to ensure the accuracy of their pressure value transmission.
Abstract:
The automatic verification assembly lines for electric energy measuring instruments can experience performance degradation or even malfunctions during long-term online high-load operation, leading to deviations in the test results of electric energy measurement errors. In order to accurately grasp the fluctuation patterns of the automatic verification assembly line measurement system for electric energy measuring instruments, determine the total variation from the measurement system and the differences in each variable, and improve the accuracy and reliability of the measurement system, an analysis plan for the assembly line measurement system was designed. Based on the analysis of the structural characteristics and working principles of the assembly line, a new experimental scheme is proposed, and a measurement system analysis plan is formulated. Taking the automated calibration assembly line of low-voltage current transformers as an example, the repeatability and reproducibility, bias and linearity, and stability of the measurement system were analyzed. The analysis results show that the variation of the measurement system accounts for 1.67% of the total variation, the variation index GR&R is 18.21%, the bias ratio is 5.4%, the linearity ratio is 8.7%, and there are 7 distinguishable categories. The measurement system has the required measurement ability and is in a conditionally acceptable state. Further analysis of the sources of variation reveals that reproducibility is the main factor of variation, and there are significant differences in the consistency of measurement systems at different workstations. Finally, based on the analysis results of the measurement system, production site management, and operation and maintenance experience, suggestions for improving the measurement system are proposed.