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L. Cordova, I. Marfenko, A. Pfau, L. Shen
Considering Covariance in Reference Flowmeter-based Calibration Facilities

Given their simplicity, flow calibration facilities using flowmeters as reference standards are very common. The present paper introduces a method to estimate calibration facility uncertainty considering empirically determined correlation effects under working conditions. This improvement strongly increases the confidence in flowmeter-based calibration facilities of the particular type used, making third-party recognition of calibration services more reliable and transparent. A special type of calibration facility having multiple reference flowmeters installed both in-series and in-parallel, and fully automated scale calibration systems using weights was used. No human intervention is required for the calibration of the gravimetric system. When no covariance is considered, the expanded uncertainty of the facility can be expressed by the single flowmeter uncertainty reduced by the factor 1/m², m being the number of flowmeters used in parallel or in series; for two devices in n lines, by the factor 1/(2n)². This approach has its limitations and does not address possible unknown systematic effects during the calibration of each reference flowmeter. A more conservative approach assumes full correlation between the flowmeters used. The tested facility was designed to make covariance between two simultaneously calibrated reference devices measurable. By knowing the covariance, better understanding is given to the real performance of the reference flowmeters under working conditions and no full correlation needs to be assumed. In this paper we present firstly theoretical considerations and discuss the assumptions for modelling this particular type of facility. Secondly historical data is presented and analyzed, and finally, the facility performance of 0.03 % up to 100 kg/s is validated through flow comparisons using a highly accurate reference flowmeter.

Tao Meng, Lei Wang, Zhou Chang, Chao Xing,Huichao Shi
Method for direction diagnosis of multiple fluctuation sources on the flow standard facility

Extra uncertainty is introduced to the result of flowmeter calibration by flow fluctuations in the flow standard facility. Identifying sources of fluctuations is important for the location and elimination of the fluctuation sources in the flow standard facility, however it is difficult to diagnose the direction of fluctuation source when multiple sources exist. A correlation analysis method based on Empirical Mode Decomposition (EMD) utilizing the signals of pressure sensor and flowmeter is proposed to diagnose the directions of different fluctuation sources. The proposed method could separate the superposition signal of multiple fluctuation sources and effectively diagnose the directions of multiple fluctuation sources at one time and provide accurate information for the location and elimination of the fluctuation sources. Experiment platform was built based on a water flow standard facility and the direction diagnosis experiment of double fluctuation sources was conducted to verify the effectiveness of the proposed method. The experiment results shows that the directions of multiple fluctuation sources could be accurately diagnosed by the proposed method.

Chaojian Tao, Jiaodan Chen, Liqiong Huang, Shuqiang Chen, Shuxi Lin, Qiang Lin, Zeng Hong
Research on Temperature Control Technology of high- Pressure Loop Gas Flow Standard Facility

The high-pressure loop gas flow standard facility (hereinafter referred to as the facility) is a working measurement standard [1] for gas flowmeters to perform measurement performance tests under different pressures. It can study and improve the measurement performance of flowmeters under different pressures and different gas media, which is of great significance to the research of flow measurement technology. This paper studies the temperature control technology of the facility, the purpose is to make the temperature meet the working requirements of the facility and as close as possible to the existing international advanced level. Through theoretical analysis and experimental methods, combined with the author's company and the experience of external construction facilities, this paper designs an intelligent control system including its various subsystems, and realizes the design requirement that the temperature change of the facility's working gas is not greater than ± 0.1 °C/min. This paper shares the construction experience, and proposes a technical route for further improvement by using advanced control methods such as fuzzy control and neural network control to reach the existing international excellent level of ± 0.05 °C/min.

Wanli Yang, Xingen Wang, Yujie Chen, Yuming Shen
Research on Mathematical Model and Optimal Flow Characteristics of Steering Diverter

The function expression of the flow characteristics of rotary flow diverters was deduced. It can be seen from the expression that when the splitter plate of the diverter moves at a constant speed through the nozzle slot,the optimal flow characteristic curve with an approximately linear relationship is obtained. A flaw of the “Biryukov curves” was pointed out. It is also proposed that the essence of the flow diverter timing error Δt isthe error caused by the installation asymmetry and the flow characteristic asymmetry, not the travel difference. The tow computational equations of timing error were deduced, the equation in JJG 164-2000 (flowmeter method) and the one in ISO 4185 standard (static weighing method). A stepper motor drive system was designed, and experiments on the installation asymmetry of the diverter were carried out. The experimentalresults show that when the diverter splitter plate is triggered in advance, the timing error produces a negative deviation while lag trigger produces a positive deviation; and the greater the distance from the center point, the greater the absolute value of the timing error.

Liu Wei, Li Li, Chen Wei, Zhan Jiao, Liu Yahui
The flow performance testing device of the ambient air sampler

In this paper, the flow measurement performance of the ambient air sampler is studied, which is widely used in environmental monitoring, health care and mining enterprises. The paper develops the flow rate performance test device of ambient air sampler, which consists of the high-low temperature test device, the load performance test device, the flow standard device and the pressure measurement device. For various types of ambient air samplers and its calibrators, the device can carry out flow performance tests with the flow range of 10 mL/min ~ 265 L/min, with flow indication error no more than ±2%, the high-low temperature tests with the range of (-20 ~ 40)℃, and the load performance tests in the range (-50 ~ 0)kPa. The uneven capability of temperature adaption of different types of samplers or from various manufacture is found through experiments research, but the flow metering performance of samplers is significantly improved compensated by temperature in this paper. In the load test, the sampler load condition of different ranges or manufacturers are different, which meets the requirement of more than 50 % the air extraction capacity.

Mengna Li, Bodo Mickan, Chunhui Li, Jia Ren, Yan Wu, Ming Xu
The comparison of the gas flow secondary standard facilities at high pressure

The first formal comparison was organized in China for the purpose of determination of the degree of equivalence of the gas flow secondary standard facilities during 2016 ~ 2020. There were 4 participants from China, and PTB was invited as the link lab to connect this comparison with the serial key comparisons of CCM.FF.K5. Based on the flow range of the existing secondary standard facilities of participating laboratories, 3 turbine flow meters were used as transfer standards. Totally 298 sets of measured data were obtained with Reynolds number range of (6.3 × 10^4 ~ 1.4 × 10^7). Results of all participants were considered for the determination of the reference value and the uncertainty of the reference value. The operation conditions were represented by the Reynold number, while the measured value was represented by the relative error of the meter e in (%). The fitted curve based on the relationship between e and the Reynolds number for each single meter was obtained. The degree of equivalence of En was finally evaluated. Among all 298 sets of measured results, there were 282 sets of results with En ≤ 1, while there were 9 sets of results with 1 < En ≤ 1.2.

A. W. Boudaoud, J. D. McGraw, T. Lopez-Leon, F. Ogheard
Traceability of the Primary Nano-flow Measurement System: Measuring the Local Inner Diameter of a Glass Capillary

As part of the Metrology for Drug Delivery ("MeDD II") European joint research project, a primary method for the measurement of liquid flow rates at the nanolitre per minute scale has been developed. This primary standard allows the calibration of flow meters and flow generators such as infusion pumps, pressure controllers and syringe pumps, for flow rates ranging from 10 nL/min to 1500 nL/min with relative expanded uncertainties (k = 2 ) of 12 % and 0.15 %, respectively. The system is based on the measurement of the displacements over time of a liquid/air interface moving inside a cylindrical glass capillary tube. The flow rate is obtained by multiplying the resulting flow velocity by the cross-sectional area of the tube which depends on the square of the capillary’s inner radius. In order to ensure the traceability of flow rate measurements to International System of Units, camera and frame rate calibration procedures have been established. However, the measured flow rates depend on the local value of the inner diameter which must also be traceable. In this paper, we present a method to measure the inner diameter of cylindrical thin-walled capillaries by confocal microscopy. The method allows visualizing the inside of a tube by filling it with a fluorescent solution and acquiring -stacked images along its full height. The mean inner diameter is deduced from the widths of the fluorescent signal in the obtained images which are measured by image processing. The method was applied on capillaries with different inner diameters and the results were compared with the values given by manufacturers. The relative expanded uncertainties (k = 2 ) were estimated to a maximum of 4 %, which is two times lower than the one provided by manufacturers.

P. Žibret, G. Bobovnik, J. Kutin
Implementation of the dynamic flying start-stop method in the pVTt gas flow standard

The gas flow standards using the volumetric method with a constant volume (pVTt) determine the flow rate based on the rate of mass change determined by measuring the density of the gas inside a constant volume. These standards normally use the static method of mass determination and rarely the dynamic one, due to dynamic changes of the gas temperature during mass collection. We have developed the analytical model that predicts the change of temperature in the pVTt system for gas flow rates up to 12 mg/min. Both measurement methods, the static and the dynamic, were implemented in the measuring system, with the dynamic method being corrected using the analytical model. The analytical correction model was validated by a comparison between the flow-rate measurements using the static and the dynamic methods. Based on successful validation of the analytical model we believe the corrected dynamic method is a viable alternative to the static one for the considered flow range.

Jun Ma, Yejun Chen
Influence of Verification Volume and Flow rate on Verification Facility for Water Meters of Piston

According to the JJG 1113-2015 “Verification Facility for Water Meters” calibration regulations, when testing the verification facility for water meters of Piston, the indication error and repeatability of the main standard implement are determined by two parameters, namely the verification volume and flow rate. Experiments show that the setting of two parameters affects the verification results, when the flow rate is set to 25 L/h and the verification volume is 2 L, the indication error and repeatability of the main standard implement meet the requirements of the verification regulation; while when the flow rate increases to 50 L/h, or even larger, the test results do not meet the requirements, i.e. the test results produce a misjudgment of the piston cylinder's metering performance. The main purpose of this paper is to verify the influence of the verification volume and flow rate settings on the piston cylinder's indication error and repeatability through testing.

M. A. de Huu, M. Tschannen, Hugo Bissig
Extending the functionality of the METAS primary standard in gas flow

METAS is the Swiss national metrology institute. Its laboratory for flow operates several primary standards for liquid and gas flow, among which two piston provers with BIPM-registered CMC entries in the range (0.1 to 300) L/min. To extend their functionality, additional working modes have been implemented in the data-acquisition software that allow almost endless measurement possibilities over the flow range (0.002 to 300) L/min. With the current extension of functionalities, all types of flow meters, from critical nozzles to laminar flow elements can now be calibrated under various configurations.In this paper, we will present the changes that have been made to the design, as well as commissioning and validation results with various types of flow meters. The increase in flow rate range towards very low values brings pressure and temperature stability consideration into account that are being treated and presented here. Finally, results from a METAS internal bilateral comparison are presented and show an excellent agreement between two primary standards.

Page 9 of 907 Results 81 - 90 of 9067