Summary of ASTM D 445 method
The time is measured for a fixed volume of liquid to flow under gravity through the capillary of a calibrated viscometer under a reproducible driving head and at a closely controlled and known temperature. The kinematic viscosity is the product of the measured flow time and the calibration constant of the Glass Capillary Viscometers. Use only calibratedGlass Capillary Viscometers, ASTM thermometers and Certified Viscosity Reference Standards. If the determined kinematic viscosity does not agree within +/-0.035% of the certified value, recheck each step in the procedure, including thermometer and viscometer calibration, to locate the source of error. The most common sources of error are caused by particles of dust lodged in the capillary bore and temperature measurement errors. The calibration constant, C, is dependent upon the gravitational acceleration at the place of calibration and this must, therefore, be supplied by the standardization laboratory together with the instrument constant.Calculate the kinematic viscosity, n, from the measured flow time, t, and the viscometer constant, C, by means of the following equation: v = C·t
where:
v =kinematic viscosity, mm2/s,
C =calibration constant of the viscometer, (mm2/s)/s, and
t =mean flow time, s.
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