计量科学与技术

2023, 67(1): 1-2.

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Design of Precision Adjustable DC Standard Source Based on PWM

GUO Junyan, YANG Chunling, YANG Xuqiang, QI Chao

2023, 67(1): 3-9. doi: 10.12338/j.issn.2096-9015.2022.0045

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In the field of high-precision DC output calibration of testing instruments and the development of precision measurement and measuring systems, it is essential to investigate strategies for improving the accuracy and resolution of DC standard sources and achieving the localization of precision adjustable DC standard sources. This paper presents the development of a precision adjustable DC standard source that uses a dual Pulse Width Modulation (PWM) synthesis voltage division regulation mode to achieve a resolution of 0.1 µV for the output DC voltage. By utilizing temperature compensation, precise phase inversion, drift-free filtering, and current compensation technology, the standard source was able to achieve an output uncertainty index of 4 ppm. Furthermore, a compensation correction algorithm was developed to improve the output accuracy. Experimental results confirm that the developed DC standard source operates reliably and stably over extended periods, making it suitable for high-performance DC reference requirements.

Remote Reproduction of Standard Time Based on Variable Speed Integral PID Control

CHEN Dehao, YANG Zhiqiang, WANG Yuzhuo

2023, 67(1): 10-15. doi: 10.12338/j.issn.2096-9015.2022.0112

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With the wide-ranging and deepening application of high-precision time and frequency in various fields, there is a growing demand for remote time traceability. In order to achieve high precision and high stability in long-range time traceability, this paper proposes using optical fiber time-frequency links to realize remote reproduction of high-precision time references. Furthermore, the atomic clock taming method is optimized using a variable speed integral PID control strategy. The time reference recurrence scheme is verified for the link between the National Institute of Metrology Hepingli campus and the Changping campus, spanning 54 km. The experimental results demonstrate that the absolute value of more than 85% of the remote reproduction time deviation is better than 0.3 ns, and the remote reproduction time stability is better than 6 ps/d. The stability of remote reproduction frequency is better than 5×10⁻¹⁶/d.

Development and Determination of Reference Material for Glycerol Trioleate/Glycerol Tristearate Solid Fat Content

PU Cheng, CHENG Fang, WANG Miaomiao, REN Lingling

2023, 67(1): 16-22. doi: 10.12338/j.issn.2096-9015.2021.0605

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Solid fat content (SFC) is an important quality indicator for describing fats and oils, such as cocoa butter and margarine. Low-field nuclear magnetic resonance (NMR) has become the mainstream method for measuring SFC due to its simplicity, speed, and lack of chemical reagents. The low-field NMR direct method is a relative measurement method that requires calibration and traceability of the instrument using a mixture of glycerol trioleate and glycerol tristearate. This paper introduces the principles of low-field NMR and SFC measurement, studies the traceability path of SFC for the glycerol trioleate/glycerol tristearate mixture, investigates its stability at different temperatures, analyzes the reasons for inaccurate measurement of mixed oil tubes at different temperature conditions, and finally determines the calibration method and temperature of the reference materials.

Correction and Calibration of R Value Curve for Blood Oxygen Saturation Measurement Model Based on Lambert-Beer Law

MA Jun, LIU Gang, LI Chao, WEN Qianyu

2023, 67(1): 23-28. doi: 10.12338/j.issn.2096-9015.2022.0252

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The measurement of oxygen saturation in peripheral tissues is an important indicator of the oxygen supply to cells and tissues. However, with the emergence of a variety of new oximeters, the existing R value curve of oximetry simulation can no longer meet the current demand for metrological testing. To address this issue, a modified method of oxygen saturation measurement based on the Lambert-Beer law was proposed. This method involves the addition of an optical filter medium to the existing verification device to correct the R value curve and achieve a correction value added to the original measurement model. The experimental results demonstrate that by adding filter media to modify the R value curve, the oximeter can measure values that are close to the standard value under different R value curves. The indication repeatability is also small, meeting the requirements of national metrological verification regulation. The proposed method effectively solves the incompatibility problem between the simulator and the oximeter. The tests with the device also indicate that the correction factor could be quantitative for different kinds of pulse oximeters, if the calibration parameters can be achieved. The proposed correction method is simple to operate and suitable for the correction of different R value curves. It can provide certain technical support for the measurement verification of the blood oxygen module of the monitor of small brands. However, it should be noted that the attachment position, material, and thickness of the filter media will affect the correction effect. In conclusion, the proposed method of using an optical filter medium to modify the R value curve is a feasible correction method for the calibration of pulse oximeters. It has the potential to be applied to different kinds of pulse oximeters and could be of great value in the field of medical measurement.

Research Progress in Quantitative Analysis of Soft Samples Based on LA-ICP-MS

GAO Tianheng, REN Tongxiang, WANG Song

2023, 67(1): 29-38, 67. doi: 10.12338/j.issn.2096-9015.2022.0269

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Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has gained significant attention in recent years due to its capability to directly analyze solid samples under quasi-nondestructive conditions, and to provide in-situ elemental concentration information with a certain spatial resolution. However, quantitative analysis of soft samples by LA-ICP-MS remains a challenge due to elemental fractionation and complex matrix effects. To obtain reliable and comparable results, the corresponding measurement protocol not only requires the use of verified methods, but also the establishment of correct calibration methods based on standards, thus enabling the traceability of measurement results. This paper reviews relevant literature published by domestic and foreign research teams since 2000, and introduces the common measurement strategies of LA-ICP-MS for three different types of soft samples. By summarizing the verification parameters of the five methods, the current situation of quantitative methods is analyzed from three aspects: method precision, accuracy, and representativeness. The paper also highlights the problem of method traceability. The results show that the quantification strategy that matches the matrix and is synchronized with the measurement is more advantageous. However, the lack of a fully matrix-matched certified reference material (CRM) limits the research on sampling representativeness and traceability of measurement results. Therefore, these two aspects will be the key problems to be addressed in the future when using LA-ICP-MS to carry out quantitative analysis methods of soft samples. Although some researchers have conducted studies on the synthesis method of soft standard and the traceability of measurement results by isotope dilution method, there are still several issues that need to be resolved.

Study on Flue Gas Flow Measurement Method Based on S-Type Pitot Tube

XU Ruixiang, ZHAI Hengtao, WANG Xu, XIAO Yuanhuan, ZHANG Tianliang, PENG Liang, XUE Lei

2023, 67(1): 39-44. doi: 10.12338/j.issn.2096-9015.2022.0262

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To investigate the measurement method of flue gas flow, the advantages and disadvantages of current main carbon verification methods are analyzed. The background and significance of carbon emission research, as well as the progress of related research at home and abroad, are described. A method for measuring flue gas flow using an S-type pitot tube is proposed based on the measurement principle of flue gas flow. Two integration methods of equal area and equal distance are proposed based on the study of pitot tube velocity measurement principle and the flow measurement method of velocity area method. The installation position of the pitot tube, the measurement points of the flue section, and their distribution in the two integration methods are compared. The rationality and advantages of the two integration methods of equal area and equal distance are analyzed and compared theoretically. To verify the rationality of the two integration methods, the results measured by the two integration methods are analyzed and compared based on the laboratory wind tunnel device. It is concluded that the deviation of the two methods is large at low flow rate, and the deviation of the two integration methods is about 0.5% at high flow rate, which provides technical support for the accurate measurement of measured smoke and air flow. The study suggests that the proposed measurement method using S-type pitot tube is a reliable and effective way for measuring flue gas flow.

Study on Energy Measurement Pricing Units and Reference Values of Natural Gas in China

JIA Lingling, WU Yunyi

2023, 67(1): 45-49. doi: 10.12338/j.issn.2096-9015.2022.0097

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In order to conduct localized research on the conversion of natural gas pricing methods, this study investigated energy measurement units in the literature based on the natural gas energy pricing model. Reference values were calculated for different methods, and the feasibility of dynamic adjustment of the reference values was explored. The study proposes natural gas energy measurement units and reference calorific values suitable for China. The results showed that using the reference calorific value as the unit of measurement and pricing for natural gas energy can better reflect the characteristics and value of natural gas itself. The reference calorific value can be assigned a fixed value or an adjusted value, and the amount of adjustment should be determined dynamically based on the stability of the natural gas periodic calorific value and its price. Using Qingfeng station and Nangang station of Ethylene branch pipeline as the gas source and downstream users as the object, pricing conversion results were calculated using 36.0 MJ/m³ as the fixed reference calorific value and average high calorific value as the adjusted reference calorific value. The research indicated that the selected reference calorific value and assignment method could support the pricing method conversion, and natural gas of different sources and qualities could be compared with each other. The flexibility of using the adjusted assignment for reference calorific values was more substantial than the fixed method.

Research on High Stability Fiber Bragg Grating Wavelength Standard

FAN Qiming, XU Ning, WU Tingyan, LIU Zhiwei, ZHANG Zhixin

2023, 67(1): 50-54. doi: 10.12338/j.issn.2096-9015.2022.0218

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Fiber Bragg grating (FBG) demodulators are widely used in various fields, including civil engineering, aviation, healthcare, and national defense. To comply with the Calibration Specification for Optical Fiber Bragg Grating Sensor Network Analyzers (JJF 1804-2020), it is crucial to calibrate the wavelength demodulation values of the FBG demodulator using a stable reference standard FBG. In this study, we developed a set of high stability FBG wavelength reference standards by utilizing a specially designed stress relief structure, intelligent control algorithm, and semiconductor refrigeration technology to achieve high precision temperature control. Through repeatability testing and comparison to commercial FBG measurements, we demonstrate that the performance of our developed FBG wavelength standards far exceeds the requirements of the calibration specification. Our results show that our FBG demodulator calibration procedure significantly improves the calibration uncertainty of the instrument.

Research on Verification Device for Air Permeability Standard Used in Tobacco Industry

ZOU Yi, YU Li, LI Chengzhi

2023, 67(1): 55-59, 54. doi: 10.12338/j.issn.2096-9015.2022.0106

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The air permeability standard for tobacco is the main instrument used in measuring paper air permeability. The accuracy of its measurements is critical for determining the transmittance of harmful gases in flue gas, which in turn has significant implications for human health. This paper explores and investigates a verification device for the air permeability standard in accordance with current National Standards. We designed a specialized fixture and constructed a complete apparatus that meets the necessary requirements. With this device, air permeability standards can be effectively traced and measurements in the region can be made accurately and reliably. By reducing the amount of tar and other harmful substances in cigarettes, this research contributes to the protection of human life and health.

Study on the Measurement Uncertainty of Temperature Itinerant Detecting Instruments Based on ISO GUM Method

YIN Yue, LIANG Xingzhong, CHEN Jie, MA Yan, ZHANG Hu, ZHANG Jiong, KONG Fei

2023, 67(1): 60-67. doi: 10.12338/j.issn.2096-9015.2022.0229

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In order to address the issue of measurement accuracy in the calibration of temperature itinerant detecting instruments, a new mathematical model has been established for measuring the low-temperature Pt100 sensors and high-temperature thermocouple sensors based on existing technical specifications. The GUM method has been employed to assess the measurement uncertainty of the temperature itinerant detecting instruments, which provides technical support for improving the traceability and transfer system of these instruments and revising the calibration specification. The results show that the GUM method identifies the primary sources of uncertainty as the temperature itinerant detecting instruments' indications and the performance of the constant temperature sources. The uncertainty of the low-temperature Pt100 sensors is 0.03℃ to 0.07℃ (k=2) in the range of -80℃ to 600℃, while the uncertainty of the high-temperature thermocouple sensors is 0.8℃ (k=2) in the range of 600℃ to 1000℃. Furthermore, the use of a salt bath tank can significantly improve the calibration accuracy of temperature sensors in the temperature range of 300℃ to 600℃.

Research on Intermediate Check Method for Gas Flow Standard Devices Using Critical Flow Venturi Nozzles

WANG Xueli, ZHAO Zuoguang, XU Yandong, XU Zhao

2023, 67(1): 68-72. doi: 10.12338/j.issn.2096-9015.2022.0062

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Intermediate check plays a critical role in the value traceability system of a measuring laboratory. The Judgement Method of E_n value is a common method used for intermediate checks of gas flow standard devices. However, this method heavily relies on the long-term stability of the check standard, which can lead to erroneous judgments. To address this issue, we designed a new method that combines two comparative tests. The first test compares the critical flow venturi nozzles within the device, and the second test compares several devices within the laboratory based on the same measurement principle. This article provides a description of the procedures involved in the intermediate check method, and we analyze the test data using an example. Our method can fully monitor the reliability of the device's main standards, as well as check the reliability of several intralaboratory devices at any time. Furthermore, our approach reduces the measurement error caused by changes in installation and operating environments. In summary, this intermediate check method is more convenient and efficient, making the verification process for critical flow venturi nozzles in gas flow standard devices more reliable.

2023 Vol. 67, No. 1

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