The Guide to the Expression of Uncertainty in Measurement (GUM) describes the standard approach for assessing uncertainty. By considering the law of uncertainty propagation, it tells us how to compute variance of functions of several random variables. Although the method is straightforward, it can become rather involved depending on the complexity of the model. In this work we develop a package for Mathematica software system which aims to render the procedure of calculation uncertainty simple and transparent for the end user.
The paper deals with the new technique for calibration of the household gas meters according to the working conditions in order to reduce the error caused by non-conversion of gas volume to base conditions. To apply this technique the studies of gas pressure and temperature variations in household gas meters during a year were carried out, the ratio of gas volumes consumed by household consumers during the cold and warm seasons of the year is defined. Based on the studies the average annual gas temperature and pressure weighed by the consumed gas volumes are defined. Based on the weighed...
Inter-laboratory comparisons between NIMJ and four JCSS accredited laboratories in Japan for water flow are carried out for wide flowrate range from 0.005 m 3 /h to 5000 m 3 /h using five type transfer flowmeters. The deviations of test results between NMIJ and the accredited labs are within approximately 0.1% and the averages of these deviations for each accredited labs are within 0.025%. These result indicate a high capability of the calibration facilities in the accredited labs. To investgate the reason of the deviations in the comparisons, influences of temperature, density and...
A new oil flow standard device is built with dual-standard by National Institute of Metrology(NIM). The two types of standards are installed in the device, namely, new-type auto-load electronic scale and standard volumetric tube. Working medium: transformer oil, with a kinematic viscosity of 21 mm 2 /s; flow range: (1.2 ~ 120) m 3 /h; the extended uncertainty of the oil flow meter with double standards: U rel ≤ 0.05% ( k = 2); the extended uncertainty for mass method: U rel = 0.04%; the extended uncertainty for volumetric tube U rel = 0.03%. The repeatability is less than 0.02%. The...
Pitot -tube is widely used to measure the air velocity. The coefficient must be calibrated to correct the measurement result. LDA (laser Doppler anemometer) can be applied to calibrate Pitot-tube to acquire this coefficient. During the process, the calibration result is influenced by the flow round the probe of Pitot-tube and air velocity distribution deviation in long axis. The experiments are conducted to evaluate or correct this influence. The results show (1) the calibration results will be different due to the interference of probe mounted in flow field. So, the proper measurement...
This paper deals with the dynamic temperature effects in a high-speed, clearance-sealed realization of a piston prover. A dynamic mathematical model was built to study the temperature variations and to estimate their influence on the flow measurements. The mathematical model is formulated on the basis of lumped-element models of the piston and the gas cavity. The energy balance for the gas cavity includes the convective heat exchange with the surroundings. One of the potential effects results from the temperature differences betwen the inlet gas flow and the cylinder wall. In addition, the...
An experimental investigation was carried out on the performance of an ultrasonic heat meter with interference of non-uniformity from the upstream installation of a ball valve, which it is partly opened. It was found that the existence of the ball valve may under-report the flow, especially when the flow rate is low. From the measured PIV results, it can be found that the velocity distribution is obviously non-uniform inside the meter, and the change is remarkable when the inlet is added with a ball valve. The time resolved PIV results also demonstrate that the flow field becomes unsteady...
The present work presents an evaluation of a flow measuring method known as the volumetric method. The method consists in running a turbine at a constant load during an extended period of time which depends upon the reservoir geometry. The flow rate through the turbine is determined from the volume change in the reservoir(s) by measuring the water level change. Through a pilot study in a full scale machine it is shown that the method reproduces reasonable results. The measured flow rate deviates by less than 3% from the value reported in the hydropower plant. The accuracy of the reported...
This paper introduces a new approach for the parameter measurement of fluid conductivity in an electromagentic flow-meter. Based on dual excitiation method, one magnetic excitation is used for flow rate measurement, and the other electric excitation is for fluid conductivity measurement. Dual-frequency electric excitation is employed to get fluid conductivity in a wide range with high precision. A calculation model for fluid conductivity is proposed.
In this study a theoretical investigation of performance of multipath ultrasonic flow meters under distorted flow profiles is proposed. The velocity distribution depends on the pipe configuration, which will produce an asymmetric flow profile and as a result will affect the accuracy of measurement. So, we discover how to minimize the effect of distorted flows on measuring process of ultrasonic flow meters due to number of chords and their arrangement. In order to evaluate the performance of the multipath ultrasonic flow meters the measurement error is determined for various asymmetric flow...