ASTM D6821 Standard Test Method for Low Temperature Viscosity of Drive Line Lubricants in a Constant Shear Stress Viscometer
12. Report
12.1 Report the final test temperature, apparent viscosity, and yield stress, if measured.
13. Precision and Bias
13.1 Precision:
13.1.1 Yield Stress - A determination of precision for the measurement of yield stress has not been made at this time.
13.1.2 Apparent Viscosity:
13.1.2.1 Repeatability - The difference between successive results obtained by the same operator with the same apparatus under constant operating conditions on identical material would in the long run, in the normal and correct operation of the test method exceed 10.3 % of the mean only in one case in twenty.
13.1.2.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test materials would, in the long run, exceed 17.2 % of the mean only in one case in twenty.
13.2 The interlaboratory program included nine test oils at the -26 °C test temperature and nine oils at the -40 °C test temperature. The slate of oils contained commercial gear oils, hydraulic oils, automatic transmission fluids, and nominally Newtonian viscosity reference oils. The oils were tested in six laboratories at -26 °C and five laboratories at -40 °C. The separate analysis of each temperature yielded essentially the same precision as the combined analysis.
13.3 Bias - There is no accepted reference material suitable for determining the bias of this test method; no statement on bias is being made.
14. Keywords
14.1 apparent viscosity; low-temperature flow properties; low-temperature viscosity; mini-rotary viscometer; viscosity; yield stress
