Current Issue

2022, Volume 66,  Issue 7

Display Method:
Abstract:
Evaporation loss is an important indicator to characterize oil quality. The Noack B method for non-wood alloy in The current industry standard NB/SH/T0059-2010 "Standard test method for evaporation loss of lubricating oils by the Noack method" has the advantages of being non-toxic, able to simulate the actual working conditions of engines and accurate test results, and is widely used in the industry. This paper studied the influence of different factors including sample addition amount, heating temperature, heating time, and pressure difference of vacuum pump on the experimental results and the uncertainties introduced in the process of Noack B method measurement. The research results show that when the sample amount is changed at (65±0.1) g, the test result change is ±0.019%. The fluctuation of the heating temperature at 245.2℃±0.5℃ may cause the test result change not more than ±0.27%. The variation of heating time per 5 s may cause less than 0.02% of the test results. The variation of measurement results caused by the pressure fluctuation of vacuum pump pressure at (20 ± 0.2) mmH2O is ±0.04%. The uncertainties introduced by the sample addition amount, heating temperature, heating time, and vacuum pump pressure difference are 0.011%, 0.16%, 0.01%, and 0.02%, respectively, and the expanded uncertainty introduced by each influencing factor is 0.32% (k=2).
Abstract:
In this paper, Microchip´s PIC24FJ128GC006 is used as the central processing unit, and LabVIEW is used as the host computer software development platform to develop a DHT8X digital temperature and humidity sensor data acquisition system. The multi-channel digital signal is collected by the single-chip microcomputer, and the collected data is transmitted to the upper computer through RS232. The data acquisition system designed by LabVIEW performs data display, processing, storage, and generates data records. It has been verified that the device is easy to operate, accurate in data reading and has good running performance.
Abstract:
Monitoring, analyzing, and measuring the real-time change of radio frequency (RF) signal plays a key role in optimizing signal spectrum efficiency. Real-time spectrum analyzers use digital fluorescence analysis technology to observe, measure and analyze time-varying signals, which have become an important means to monitor transient signals. In this paper, the key technical principle of the real-time spectrum analyzer is introduced, and the calibration methods for real-time bandwidth analysis and full-capture minimum pulse width-amplitude ratio are studied and proposed. According to the main functional characteristics of the real-time spectrum analyzer, the calibration methods of real-time bandwidth analysis and full-capture minimum pulse width-amplitude ratio are experimentally verified, and the uncertainty analysis and evaluation are carried out.
Abstract:
Purity measurement of the peptide is the key to building metrological traceability for the measurement value of peptides in clinical chemistry, pharmaceutical chemistry, food chemistry, and other fields. In addition to the mass balance method, nuclear magnetic resonance method, and hydrolysis method, organic elemental analysis is a new technique for measuring the purity of peptides in chemical metrology. However, a detailed introduction to this technique is yet to be reported. In this paper, a technique for peptide purity measurement based on the analysis of nitrogen, sulfur, and other elements has been established. Using oxytocin as a typical sample, the nitrogen and sulfur elements in the sample were analyzed, the content of nitrogen and sulfur elements in the main component was obtained by deducting the content of nitrogen and sulfur elements in the relevant structural impurities, and the purity results of the peptide were obtained by calculation using the information of the number of atoms and molecular weight of nitrogen and sulfur elements in the molecule of the peptide. The relative standard deviation was less than 1% compared with the measurement results of the authoritative mass balance method. The results of the impurity-corrected organic elemental analysis technique established in this paper are accurate and reliable and can be used for peptide purity standard substance determination.
Abstract:
As endocrine-disrupting compounds, 4-octylphenol, 4-nonylphenol, ethinylestradiol, hexestrol, and dienestrol have been detected in water, soil and food, and their certified reference materials are in wide market demand. In this paper, the purity of the five organic compounds was analyzed by differential scanning calorimetry (DSC), and joint research was carried out by high-performance liquid chromatography (HPLC) and thermal gravimetric analysis (TGA). The results showed that the purity of 4-octylphenol, 4-nonylphenol, ethinylestradiol, and hexestrol could be determined by DSC, and the results were in good agreement with those of the HPLC method. Since there was no obvious endothermic curve of dienestrol observed by DSC combined with TGA which revealed the decomposition of dienestrol during melting. It is concluded that the DSC method is not applicable for the purity analysis of dienestrol.
Abstract:
Aiming at the excessive temperature interval between the zinc fixed point (419.53℃) and the aluminum fixed point (660.32℃) in the International Temperature Scale of 1990 (ITS-90), an Al-Cu fixed point (Cu 33wt%, 548.16℃) was developed as an auxiliary fixed point. Self-developed radiation thermometer RT9032 was used to test the melting and solidification temperature values of Al-Cu fixed points. For the determination of the Al-Cu fixed point temperature value, the average value of the melting plateau, the point of inflection (POI), and the upper limit (UL) temperature point were adopted. The research results showed that different determination methods do not produce significant differences for the melting temperature, with a maximum difference of 34 mK, and the repeatability of the Al-Cu fixed point is within 18 mK. Therefore, the Al-Cu fixed point (melting point) can be used as an auxiliary fixed point in addition to the ITS-90 fixed point.
Abstract:
As one of the important performance parameters of the signal source, it is of great significance to measure the signal source voltage standing wave ratio(VSWR)accurately. Based on studying the structure of the signal source and the two working mechanisms of “RF OFF”, the influence of "RF ON" and "RF OFF" on the measurement results of VSWR for the signal source was analyzed. With a vector network analyzer as the measurement equipment, this paper studies the measurement methods of VSWR for signal sources in different modes. The experimental results showed that the passive device measurement method under the condition of “RF OFF” can be used for the signal source with fast closing mode, while the frequency offset measurement method under the condition of “RF ON” can be used for the complete shutdown mode.
Abstract:
With the large-scale application of precision thermometers with a temperature measurement accuracy of up to 1 mK or even 0.1 mK in experimental equipment and aerospace equipment, higher requirements are placed on the temperature control accuracy of the thermostatic bath used in the traceability of precision temperature measurement values. A thermostatic bath with a temperature control accuracy of less than 1/10,000 to meet the traceability requirements of its value. In this paper, the model of the thermostatic bath for testing precision thermometers is built by using the thermostatic calorimeter temperature control mode, and through theoretical analysis and experimental verification, the thermostatic bath model can meet the calibration requirements of precision thermometers with a temperature measurement accuracy of 1 mK or even 0.1 mK.
Abstract:
Linear calibration curve is widely used in the field of chemical measurement, but its applicability conditions and uncertainty calculation method need to be further strengthened, and it is unreasonable to rashly use the ordinary least square method when the applicable premise is not met. Based on practical data examples, this paper compares the difference between the ordinary least square method and the weighted least square method. Applying the uncertainty propagation law, the uncertainty calculation formula of the linear calibration curve is derived in detail and compared with the widely used calculation method at present. It is suggested that when determining the calibration curve, whether the uncertainty of the measurement results meets the homogeneity of variance should first be considered, and if it does not, the weighted least square method should be used. When calculating the uncertainty introduced by the calibration curve, the uncertainty of the actual measurement results should be used instead of substituting the residual of the measurement results of the calibration solution.
Abstract:
Off-site law enforcement comes is an important means for investigations into unlawful acts of motor vehicles. The metrological performance of monitoring devices, however, directly affects the accuracy and impartiality of law enforcement. By collating the monitoring equipment used by traffic police, environmental protection, and traffic competent authorities for off-site enforcement of motor vehicles and their metrological specifications, the characteristics of the monitoring equipment for off-site enforcement of motor vehicles and the existing verification and calibration methods are sorted out and analyzed, and the monitoring system for motor vehicle honking is used as an example to make recommendations on the verification and calibration methods for monitoring equipment.
Abstract:
Anechoic chamber and hemi-anechoic chamber provide the necessary acoustic environment for various acoustic tests, mainly including frequency range, spatial range, and background noise of the free sound field. The anechoic chamber and hemi-anechoic chamber absorb the sound wave incident on the wall and reduce the reflected sound by laying sound-absorbing materials in the chamber, thereby generating a free sound field environment. This paper introduces the principle and method of calibrating the free sound field of anechoic chamber and hemi-anechoic chamber by inverse square law and the data processing of the free sound field of the anechoic chamber to provide experience reference for improving the measurement accuracy of the free sound field of anechoic chamber.
Abstract:
Vibration frequency is an important parameter in the particle impact noise detection (PIND) test. Based on the MATLAB fitting tool and logarithmic transformation, the “package height vibration frequency” relationship graph is analyzed, and a quantifiable mathematical function model is developed to improve the accuracy of the vibration frequency setting. Aiming at the inconsistency of PIND test standards, the standard adoption priority is clarified through the comprehensive comparison method, and the use of impact pulse duration parameters is optimized. Intermediate check of the PIND test equipment based on the mean and range control chart method was carried out to ensure the validity and reliability of the calibration state of the key parameters of the PIND test equipment.
Abstract:
In this paper, the coaxiality error of dual-spindle boring and milling machine measured by laser calibrator is studied, and the error factors affecting the measurement results are analyzed. According to the structure characteristics of dual-spindle boring and milling machine, the influences on the coaxiality error are analyzed from three main aspects: column straightness, verticality, and positioning accuracy. Based on the analysis of coaxiality measurement results, it is determined that the direction of deviation of the positioning accuracy of the column and the direction of deviation of the verticality of the column to the table are the main influencing factors. Based on the analysis results, the assembly process of dual-spindle boring and milling machine can be optimized in a targeted manner to reduce the coaxiality error.
Abstract:
According to the measurement method in Appendix A of JJF 1815-2020 " Calibration Specification for Class Ⅱ Biosafety Cabinets ", the source of uncertainty components of each standard was analyzed, and the measurement uncertainty evaluation method for biosafety cabinet personnel, product, and cross-contamination protection (potassium iodide method) has been successfully established, and the uncertainty of the measurement results was evaluated. The extended uncertainties of personnel protection, product protection, and cross-contamination protection of biosafety cabinets were 34%, 33%, and 32%, respectively, with the inclusion factor k all being 2, which suggests that they can be used for the standardization of methods for traceability and measurement uncertainty assessment of related parameters.