1.1 Test samples can exhibit different behavior at low temperature in the CCS, thereby requiring procedural variations. Some highly viscoelastic samples will spiral toward the rotor shaft when the rotor drive is started. If the sample climbs from the shear zone, the rotor speed will increase noticeably. The use of the rubber stopper in the fill tube (see 11.2) normally will ensure that the procedure in Section 11 will be satisfactory; however, very highly viscoelastic test samples can require this special procedure. The procedure in A1.2-A1.7 is used for both viscoelastic and non-viscoelastic samples. There are more manipulations in shorter time periods required in A1.5 than in 11.2. Calibration oils must be run by the same procedure as the test samples since the calibration curves can differ slightly.
1.2 Insert test sample from a dropping pipet into the filling tube filling the gap between the rotor and stator, with a slight excess to cover the rotor with about 1 mm of liquid. Turn the rotor by hand to ensure complete wetting of the surfaces of the stator and rotor while the last portion of this sample is flowing up past the rotor sides.
1.3 Turn the temperature control and coolant flow on, and allow the stator to cool. Control temperature should be reached within 30 to 60 s for test temperatures down to -20°C and within 60 to 90 s for test temperatures down to -30°C. To ensure optimum control of temperature, the valve settings on the coolant circulator are set for control of coolant with a low-viscosity test sample in the viscometric cell and the simulator motor turned on; the temperature of the coolant to the viscometric cell is approximately 10°C below the test temperature. There must be good thermal contact with the temperature sensor in the thermal well in the stator. This thermal well should be cleaned periodically (see 6.6.1).
1.4 The null meter reset knob should be set slightly lower than the test temperature, such that when the rotor drive is turned on the test temperature will be established without further temperature adjustment.
1.5 Start a timer when test temperature is reached (as indicated by the temperature indicator meter and the cyclic controlling of coolant flow). At 10 more or less 2 s after starting the timer, add additional sample directly into the cup, thus filling the cup completely.
1.6 Turn on rotor drive at 30 more or less 2 s after start of timer.
1.7 Record speed indicator meter reading at 10 more or less 2 s from rotor startup, estimating the meter reading to the nearest 0.001 unit. Turn off rotor drive and coolant flow.
1.8 Clean the CCS by the procedure in 11.3-11.3.3.
1.9 The precision of the measurement of the apparentviscosity of highly viscoelastic engine oils has not been determined and can be expected to be somewhat poorer from that determined in 14.1-14.3.
