9762 papers found
The paper deals with a method of THD factor measurement with using watch filtration of the fundamental frequency. The proposed application enables to identify main frequency changes of evaluated signal what improves the effectiveness of filtration. Results of the simulation studies and laboratory experiments proved usefulness of suggested solutions for measurement of THD factor. It let design a prototype of measuring device based on the proposed method.
The high precision comparison of DC currents in electrically insulated circuits using magnetic modulators was not yet realized in practice; the nature of arising errors and their values were not described in literature. The physical model is proposed, which explains the error as a result of non-homogeneous magnetic fields influence, produced by comparison and output windings along the ring core of magnetic modulator. The expression for comparison error calculation in such devices is deduced, experimentally verified and methods of its reducing are proposed. The comparison error about 10 -7 is...
Modulation quality in most of digitally encoded cellular systems is examined by measuring the phase error and the frequency error of the transmitted signal. Phase error is an indication of how accurately the individual bits modulate the radio-frequency carrier; frequency error is the difference between the specified carrier frequency and the actual carrier frequency. The paper proposes a new technique for phase and frequency error measurement. The technique is based on a suitable digital signal-processing algorithm, capable also of gaining burst synchronisation on TDMA signals;...
The IEC 1000-4-7 standard is currently mandated to fix both procedures and instruments for evaluating the level of harmonics and inter-harmonics in electromagnetic interference measurements for power supply systems and connected equipment. Prescriptions and recommendations related to inter-harmonics seem to be not well detailed; this is particularly true for those showing a nonstationary behaviour. As a matter of fact, only a digital signal-processing approach, based on the Discrete Fourier Transform, is strongly recommended; little or nothing is said both about the sampling rate to be...
The result of a measurement has uncertain value-band depending on dynamic behaviour of the measured object and measurement instrumentation. Numerical value is attained with successive approximation of the difference between the reference and measured quantity. Estimation of the difference between two levels is possible with at least two sampling pulses. The dynamic error is proportional to that difference with addition of some constant. For effectiveness of differential tracking, the non-uniform quantization must fulfill three conditions: partitions into halves, increasing quantization...
The water analytic methods, based on the conductivity measurements are in the field of the physico-chemistry, called conductometrie. Its main task is the defining the material quality, but also quantity via soluble materials. One important element in this hardware is the conductivity measuring device and especially the conductivity cell.
This paper describes the measurement services, the instrumentation and procedures available for force metrology at the National Institute of Standards and Technology, USA. The uncertainty in the forces realized over a range of 44 N to 53 MN is reviewed. The maintenance and the uncertainty of the voltage ratio indicating system for strain gage load cells are discussed.
In order to improve the reliability of weight calibration, a fully-automatic mass comparator has been installed in an airtight chamber. In the chamber, the density of the inner air is kept constant, and mass comparison can be done with the fixed environmental conditions. Consequently, a decrease of the uncertainty of the air buoyancy correction and the standard deviation of the mass comparison will be expected. An airtight chamber was made of stainless steel, divided into upper and lower cases, and has a cylindrical shape with an inner diameter of about 700 mm and height of about 740 mm. A...
The NRLM has therefore developed a force standard machine employing an electromagnetic force compensation sensor to extend the established 10 N to 20 MN force standards to forces of mN order. We are currently conducting research on achieving force standard measurement precision in this range of ± 0.02 % or less. In order to make comparative verification of force standard values established by deadweight-type force standard machines, the rated capacity of the electromagnetic force compensation sensor incorporated in this machine is 50 N at 0.1 mN resolution. However, by reducing the capacity...
Direct extrusion shaping creates friction on the tool surfaces due to relative motion of the tool materials. Friction increases the necessary extrusion force and causes extrusion faults by changing the material flow mechanism. A number of parameters affect the magnitude of extrusion force. Being one of these parameters, the lubrication effects the friction and therefore defines the extrusion force in friction. In this study, the effect of lubrication on the extrusion force is theoretically and experimentally studied. In the experiments done, the parameters such as extrusion ratio, die angle...