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Construction of constant-pressure gas flowmeters utilizing directly driven bellows and diaphragm bellows as volume displacers were described in recent decades. They have important advantages: accuracy, reliability, easy operation and maintenance.Difficult is to scale sufficiently accurately the changes in volume at compression, to evaluate the uncertainty of this measurement, and to include all the...
The main obstacle in the construction of primary vacuum standards for very low pressures – ultra-high vacuum (UHV) – is outgassing from the walls of the apparatus. Thus, principles utilising a higher pumping rate in the calibration chamber, e.g., the pressure ratio technique, seem to be more useful for this range. However, a serious problem is inherent in this method, namely, that the gas in the calibration...
Accurate calibrations of gauges to ever lower pressures (higher vacuum) are increasingly becoming necessary. The calibrations over the entire ultra high vacuum (UHV) range i.e. up to 10−10 Pa are already sometimes demanded by the users of vacuum measuring devices. Standards covering part of this range are available in some national metrological laboratories while primary standards covering the entire...
Continuous oscillations of the pressure of hydrogen and some other gases were observed in an ultra high vacuum (UHV) apparatus. The oscillations arose progressively during experiments with hydrogen permeation through stainless-steel ion-implanted samples, later they occurred in the apparatus without any sample as well. They were observed for a long time, detected with an ionisation gauge and a mass...
A simple cryogenic system for testing of the superconducting power transformer was constructed. Thermal shielding is provided by additional liquid nitrogen bath instead of super-insulation. The system, together with use of a precise nitrogen liquid level meter, permitted calorimetric measurements of losses of the 8kVA HTS transformer with a resolution of the order of 0.1W.
The Becker friction vacuum gauge is based on the measurement of the damping of mechanical vibrations ofa metal ribbon caused by the surrounding gas. The lower limit of the pressure measurement range dependsmainly on the internal damping in the material of the vibrating element. This damping is influenced by thechoice of a suitable material of the ribbon but it also rises with increasing tension in...
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