Cone-plate viscometer requirements in use
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The main feature of the cone-plate viscometer is that the dosage is small, only about 1ml; low viscosity can be measured, the viscosity of water can be measured; programmable automatic detection, and printout; the instrument can be connected to a computer, through the hemorheological workstation software Platform operation, complete a series of hemorheology indicators, such as: apparent viscosity of whole blood, shear stress, shear rate, Casson curve, etc.
Cone-plate viscometer mainly includes a flat plate and a replaceable cone rotor. The motor drives the conical rotor to rotate at a constant speed through a variable speed gear, and an appropriate amount of sample is kept on the flat plate and the fingertips of the rotor, and the friction between the sample molecules drives the cone and plate to rotate. Under the action of the torsion spring in the torque detector, the torsion spring no longer deforms after the rotor rotates by a certain angle. At this time, the torsion torque applied by the torsion spring is related to the molecular internal friction (ie viscosity) of the sample being tested: the greater the sample viscosity, the greater the torsion torque. A variable capacitor is installed in the torque detector, and its moving piece rotates with the cone plate, thereby changing its own capacitance value. The torque of the torsion spring reflected by this capacitance change is the viscosity of the measured sample, which is displayed by the meter, and the displayed data is the viscosity value of the sample.
Cone-plate viscometer has become a standard instrument for rheological tests of non-Newtonian materials such as paints, inks, varnishes, resins, dispersants, ink cosmetics and pharmaceuticals. The viscosities of these materials all depend on the shear rate. The high-precision wear-resistant cone head of the cone-plate viscometer rotates at a controlled temperature at high speed to simulate the real shear force. The bottom plate of the viscometer is equipped with temperature control, which can measure the temperature characteristics of the viscosity of the paint.
Cone-plate viscometer requirements in use:
1. Its performance index must meet the requirements of national metrological verification regulations. The viscometer in use is subject to periodic verification. If necessary (the instrument is used frequently or in a critical state of qualification), an intermediate self-check is required to determine its measurement performance. The coefficient error is within the allowable range, otherwise accurate data cannot be obtained.
Second, pay special attention to the temperature of the measured liquid. Many users ignore this point and think that the temperature difference does not matter. Our experiments prove that when the temperature deviation is 0.5 ° C, some liquids have a viscosity value deviation of more than 5%. The temperature deviation has a great influence on the viscosity. The temperature increases and the viscosity decreases. So pay special attention to keep the temperature of the measured liquid constant near the specified temperature point, and do not exceed 0.1 ° C for the measurement.
Third, the choice of measuring container (outer cylinder). For the viscometer, carefully read the instrument manual. Different rotors (inner cylinders) match the corresponding outer cylinders, otherwise the measurement results of the cone-plate viscometer will deviate greatly.