IMEKO Event Proceedings

Page 781 of 855 Results 7801 - 7810 of 8545

Chiu-Hsien Chen, Sheau-shi Pan
THE UNCERTAINTY OF PITCH AND YAW RE-EVALUATED FOR PRIMARY ROCKWELL HARDNESS STANDARD SYSTEM IN CMS

The Primary Rockwell Hardness Standard System was set up in the Center for Measurement Standards since July 1996 till June 1997. During the time, a laser interferometer, HP10737R 3-axis compact interferometer system was used to measure the effect of pitch and yaw of the Rockwell Hardness machine.
As the laser interferometer was performed the measurement of the pitch and yaw of the indenter when the hardness was measured; then we evaluated the uncertainty caused from the Abbe's error through pitch and yaw measurements. In this paper, we will compare the results to the results of 2003 and to evaluate the aging effect of the indenter axis during seven years' used.

Boris Stogny, Evgeny Tankevich, Inna Iakovlieva, Gregory Varsky
THE UNIVERSAL MODEL OF ERROR OF ACTIVE POWER MEASURING CHANNEL

The types of the structures of active electric power measuring channel and features of functions of measuring transformers in their configurations are considered. The universal mathematical model of measuring channel error, which takes into account influence of channel’s configuration, individual metrological performances of separate measuring devices, measuring operating conditions and the controlled electric network mode on its value, is developed. The example of application of the offered model is made.

T. Chinarak, K. Leetang, T. Changpan
THE UPGRADED CONTROL SYSTEM OF PRIMARY LIQUID FLOW MEASUREMENT STANDARD AT NIMT

The liquid piston provers have been widely used as the primary standard for liquid flow measurement. There are many flowmeters which can be used with the prover such as turbine flowmeters, variable area flowmeters, electromagnetic flowmeters, etc. The flowrates from the prover are measured by volumetric method. Thus, the displaced volume of water and the moving distance of the piston during measurement are the key factors. In order to receive the accurate volume, the efficient system for gaining pulses from the linear encoder is needed. Also, temperature and pressure of liquid inside the piston cylinder and the environmental conditions are involved with the measurement. Recently, the piston prover at NIMT had been upgraded by replacing the out-of-date control system and modifying the key equipments; linear encoder, PT-100 and digital manometer. Moreover, the well-known method called ‘water draw’ has been brought to verify the new system and provides the piston prover constant value. The uncertainty of the system is evaluated and reported as 0.07% (k = 2).

Lifen Wan, Chunhui Li, Yan Li, Lishui Cui
THE UPSTREAM INSTALLATION EFFECT ON THE CBPR OF SONIC NOZZLE

The test for the critical back pressure ratio (CBPR) of a sonic nozzle by using an orifice plate is established, and six types of upstream conditions are set up. Preliminary experimental results show that the upstream conditions have almost no effect on the CBPR at throat Reynolds number larger than 1.1 × 105, but better upstream conditions or the longer lengths of upstream straight pipe can improve flow stability; when throat Reynolds number smaller than 1.1 × 105, the upstream installation condition would have a significant impact on the CBPR, because of the occurrence of the premature unchoking phenomenon. Therefore, it is necessary to measure the CBPR in use for small throat diameter nozzle.

Przemyslaw Otomanski
THE USAGE OF THE APPROXIMATE METHODS TO DETERMINE THE UNCERTAINTY OF RELATIVE HUMIDITY MEASUREMENT USED TO INTEGRATED HUMIDITY SENSORS

Results of experiments concerning humidity measurements have been presented in the paper. Integrated humidity sensors were used for the experiments, which transformed the value measured into a corresponding capacity. The structure of a measuring system was described, and the requirements concerning particular elements of the measuring track were defined. Using the regression method, an analytical equation was modeled, combining the output capacity value of the sensor with the examined humidity changes. With the use of experimental results as well as the least square method, the values for the above equation’s parameters were determined. The knowledge of coverage factor characteristics for the convolution of four selected probability distributions was used for the research.

Ferdinando De Tomasi, Maria Rita Perrone
THE USE OF A MULTIWAVELENGTH LIDAR TO DETECT AEROSOL LAYERS IN THE ATMOSPHERE

The peculiarity of lidar systems is to provide vertical profiles of aerosol extinction and backscattering coefficients, which allow getting information on aerosol optical properties and their dependence on altitude. We analyze in this paper a case study in which lidar signals have allowed detecting different atmospheric aerosol layers from the boundary layer up to the stratosphere. Results on the dependence of aerosol optical properties on altitude will also be presented.

O Kruger, L Mostert
THE USE OF A µCMM IN THE CALIBRATION OF HARDNESS INDENTERS

In order to perform traceable hardness measurements using Rockwell Hardness Indenters, the indenter must conform to the requirement of ISO 6508-3 standard. The standard defines specifications for the geometric parameters for this type of indenter. Conformance to this standard is of particular importance to all calibration laboratories which operate in accordance with ISO/IEC 17025. At present there is no facility in South Africa with the capability of calibrating indenters for conformance to ISO 6508-3. This situation is being addressed through a series of studies currently being conducted at the National Metrology Institute of South Africa. The following parameters are calibrated using the µCMM. ISO 6508-3 specifies a radius of 200 µm with an uncertainty of ± 5 µm for Rockwell Hardness Indenter tips. Also specified in the ISO standard is the cone perpendicularity between the axis of the diamond cone to the axis of the indenter holder, with a specification of ± 0,03°. The last part of the ISO standard which was investigated states: “The surface of the cone and the spherical tip shall blend in a truly tangential manner.” All these parameters were measured and associated uncertainties calculated to prove conformance with ISO 6508-3 for the calibration of hardness indenters.

G. L. Tiago Fº, G. T. Caetano
THE USE OF ADCP IN SMALL AND MEDIUM RIVERS

The introduction and operation of a hydrological data net depends on the installation of flow stations net that can generate reliable data obtained from a stage discharge curve, that is produced through a series of flow measurements made in the cross section. Usually, for measurement of those flows, it is used the conventional current meters and other methods. They are well-known and applied plenty methods, however, in the execution they demand time, knowledge and technical abilities, without which can be generated data that are not real.
A way to accelerate the process is the use of methods and automated devices, as it is the case of Acoustic Doppler Current Profiler - ADCP, that measures the flow automatically through Doppler effect. However, its use is restricted to the great rivers.
The present paper makes a review and has the objective of comparing different methods of flow measurement. In this case, the comparison is made between the conventional methods and the acoustic automated method of ADCP. With this study, it intends to verify the reliability of the instrument for flow measurement in small and medium rivers and, according to the case, to develop a methodology for the imposed conditions.

J.M. Lee, K.B. Lee, S.H. Lee, T.S. Park
THE USE OF CALIBRATED IONIZATION CHAMBER FOR THE CERTIFICATION OF 226Ra RADIOACTIVITY

The efficiency of a 226Ra aqueous solution source in the radium-radon secular equilibrium against the gamma reference ionization chamber in KRISS has been obtained both by calculating from the photon energy-dependent efficiency curve of the ionization chamber and by measuring with an 226Ra standard source. The two results of calculation and measurement have showed such a good agreement that the gamma reference ionization chamber may be used to certificate the radioactivity of 226Ra aqueous solutions in the secular equilibrium and its traceability could be linked to the multi-radionuclide calibration of the ionization chamber.

Page 781 of 855 Results 7801 - 7810 of 8545