ASTM D2162 Test Method for Basic Calibration of Master Viscometers and Viscosity Oil Standards
4. Summary of Test Method
4.1 Two or more master viscometers, having calibration constants in the 0.001 to 0.003-mm2/s2 (cSt/s) range, are calibrated with water at 20°C. The kinematic viscosities of two or more oil standards are measured at 40°C in these two master viscometers. Corrections are made for buoyancy and, where necessary, for temperature and surface tension.
4.2 A third master viscometer, with a calibration constant of 0.003 to 0.009 mm2/s2 (cSt/s), is then calibrated at 40°C with the two standard oils and its calibration factor calculated at standard conditions for water at 20°C. In like manner additional viscosity oil standards and additional master viscometers are calibrated at 40°C using the average results from at least two master viscometers or two oil standards. Steps between successive calibration constants or viscosities increase by a factor of three or less until the desired viscosity range is covered.
4.3 Oils are calibrated at other temperatures using the average result from at least two master viscometers.
5. Significance and Use
5.1 Because there are surface tension or kinematic viscosity differences, or both, between the primary standard (7.4) and kinematic viscosity standards (7.5), special procedures using master viscometers are required to "step-up" from the kinematic viscosity of the primary standard to the kinematic viscosities of oil standards.
5.2 Using master viscometers calibrated according to this test method, an operator can calibrate kinematic viscometers in accordance with Specifications D446.
5.3 Using viscosity oil standards established in this test method, an operator can calibrate kinematic viscometers in accordance with Specifications D446.
