A. Borchling, C. Kroner
Overview of differences between electronic and mechanical domestic cold water meter

During the last years the share of electronic water meters based on ultrasonic or magnetic-inductive measuring principles installed in households has increased steadily. The question arises to what extent their measuring performance differs from that of classic mechanical water meters. Due to the static measuring principles without moving mechanical components, it is to be expected that electronic water meters are less susceptible to water properties. To gain insights in this regard experiments were conducted with different water qualities (pH, total hardness, particles). In addition, the measurement performance at constant and variable flow rates was evaluated and compared with that of mechanical water meters. The fact that electronic water meters, in contrast to mechanical meters, measure discretely and not continuously was also addressed in the investigations. In particular, it was studied how the sampling interval affects the accuracy with which the total volume is recorded, depending on the time of sampling and the length of the observation period.

Liu Yajie, Tian Peng, Liu Yizai, Zhang Yuanming
Research on Measurement Performance Change of Water Meter in Use Based on Multi-stage Sampling Inspection

Water meter measurement data is the basis for users to pay water bills, sewage charges and some enterprises to pay water collection fees, the national administrative departments of measurement of water meters to implement the cycle of calibration, the use of the deadline, the expiration of the rotation of management. Because of the high cost of replacing a large number of water meters, and disassembly will affect the normal production and life of water, so there are still a large number of water meters have exceeded the rotation cycle but still in use. The lack of measurement and testing data for water meters in long-term use in the industry is likely to cause cost disputes between users and water companies, and is not conducive to the water authorities' accurate measurement of the quotas for water users in their jurisdictions, or to the enterprises' accurate accounting of water costs and revenues. At present, most of the domestic residential water meters in use are rotary-wing water meters and screw-wing water meters, and through sorting out the two types of water meters in use in a city, researching the sampling plan, implementing multi-stage sampling and testing, and obtaining statistics on the metering performance of 1920 water meters of various years of use, various specifications and various frequencies of use with a sample capacity of 1920 units. The positive offset and negative offset ratio were compared horizontally. Combined with the characteristics of water meter structure, working principle and error generation mechanism, the analysis was carried out to determine the specific stage of the life cycle of each type of water meter. Water companies, water end-users, and water extraction enterprises can grasp the qualification rate and indicated value error of their water meters based on the research results, which can facilitate the development of disassembly and calibration or rotation plans. The administrative department in charge of metering can refer to the research results and revise the cycle inspection or rotation time in the relevant metering technical regulations with the current economic development. Therefore, the research results have high application value.

P. G. Spazzini, G. La Piana, A. Piccato, V. Delnegro, M. Viola
FLOW LEAKS RENORMALIZATION

Flow leaks are small devices that generate a well-determined flow when subject to a pressure differential (feed pressure). Such devices are widely used in the industry for the easy generation of flows, which can be used for several applications. In order to be correctly included in a Quality Management System (QMS), they need to be calibrated against a reference flow. Such calibration depends on the feed pressure and on the fluid density through a complex relation which can be derived from the modified Darcy law, therefore results of a calibration performed in a given condition are not necessarily valid when the leak is used in different conditions (e.g. different atmospheric pressure, ambient temperature). In the present paper we will show how to obtain a correct renormalization of the calibration results, which, if applied in use, allows to compute precisely the actual flow rate generated by the leak. The renormalization is based on the modified Darcy law, and therefore requires the determination of the leak permeability. A mathematical description of the renormalization will be presented. Additionally, a method for the experimental determination of the permeability will be discussed. The effect of the renormalization on the output of the leak will be demonstrated through a set of example cases, obtained in various environmental conditions within our laboratory. It will be shown that, first the calibration uncertainty can be reduced dramatically by applying the correct normalization, and second that the in-use uncertainty can be brought to be of the same order of magnitude as the calibration uncertainty

Y. W. Zhang, L. S. Cui, D. L. Xie, H. Zhang
Study on the Uncertainty of the Doppler Frequency for the Calibration of LDV within the Speed of (0.1~340) m/s

Laser Doppler Velocimetry (LDV) is a single-point velocity measurement instrument. LDV can be precisely calibrated by the adjustable speed spinning-dics facility from NIM at speeds generally less than 40 m/s. However, due to its unique limitations, it is hard to calibrate LDV at a higher speed. To solve the problem of traceability of LDV high-speed measurement results and of the applicability of LDV low-speed calibration results under high-speed conditions, it is analyzed that the uncertainty of velocity depends on both interference fringe spacing and Doppler frequency. As fringe spacing is independent of velocity, the possible difference of uncertainty in between the high and low velocity may be only related to the uncertainty of Doppler frequency at different velocities. Doppler frequency is a result of Doppler frequency algorithm, which includes mixed-radix FFT (Fast Fourier Transform) and the phase difference correction method in this paper. Because of the nonlinearity and complexity of the algorithm, the uncertainty of Doppler frequency is suitable for being evaluated by Monte Carlo Method (MCM) propagating probability distribution. The evaluation result shows that the relative uncertainty of Doppler frequency caused by the algorithm is less than 0.05 % within the range of (0.1 ~ 340) m/s. The obvious difference of uncertainty has not been found in different velocities investigated. The budget resulting from Doppler frequency uncertainty change on the velocity result is less than 0.00075 %. It is concluded that the calibration result at low velocity is also reasonable to be used in the case at the high velocity measurement within the speed of (0.1 ~ 340) m/s.

Zhang Ying, Yang Fan,Wan Lifen, Xiong Qian, Chen Ling
Systematic study on the reappearance of the horizontal position of Standard Metal Gauge and related problems

Standard metal gauge, especially the first class metal gauge, it is mainly responsible for the second class, third class standard metal gauge value transfer function; In the actual verification work of standard metal gauge, if the level deviates from the source position or is not adjusted for human reasons, the accuracy of the measurement results will be directly affected, resulting in the deviation of the measurement value transmission. By studying the influence of the level deviation from the tracing position of the leveler on the level, the deviation function of the measuring neck and the level tube is obtained. In addition, based on the analysis of common metal level compensation gauges, the formulas for calculating the level compensation of various kinds of compensation gauges are obtained. Based on this, some suggestions are put forward for the compensation gauge with the level tube arranged vertically. By analyzing the incline between measuring neck, liquid level pipe, scale and main part produced in the production process, it is concluded that the installation incline has no influence on the measurement results.