Abstract
The viscosity standard in Japan has been established and maintained with capillary master viscometers which are calibrated by the stepping-up method based on the kinematic viscosity of distilled water at 20°C and at atmospheric pressure. In order to improve the accuracy of kinematic viscosity measurements and to extend the temperature ranges of the viscosity standard, new capillary master viscometers with an automatic flow time detection system have been designed and constructed. Then, NRLM (National Research Laboratory of Metrology) has participated in the international comparison of ASTM (American Society for Testing and Materials) standard viscosity liquids organized by ASTM Committee D-02. 07 A since 1984 to confirm the international consistency of the kinematic viscosities determined in the temperature range -40 to 100°C by using new capillary master viscometers.From the results of the comparison, the differences between kinematic viscosities obtained by NRLM and CIC (Cannon Instrument Company, U.S.A.) are -0.28 to 0.20%. The accuracy of kinematic viscosities of the ASTM standard viscosity liquids determined by capillary master viscometers is estimated to be within ±0.05% in two standard deviations.
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