Use Of Viscometer

2021/04/16

Use Of Viscometer

A viscometer is a physical property analysis instrument for measuring fluid viscosity. Viscosity is a physical property of a fluid substance, and an important physical parameter to measure the resistance of a liquid to flow. It reflects the internal friction between molecules when the fluid is subjected to an external force. The viscosity of a substance is closely related to its chemical composition. Viscosity measurement is closely related to petroleum, chemical, electric power, metallurgy, national defense and other fields. It is an important means for industrial process control, product quality improvement, energy conservation and development. In scientific fields such as physical chemistry and fluid mechanics, viscosity measurement plays an important role in understanding fluid properties and studying flow conditions.

Correct use of digital rotational viscometer, pay attention to the following points.

The blacksmith needs his own hardware! The performance index of the instrument must first meet the requirements of the metrological verification regulations or meet the calibration standards of the Brookfield manufacturer. The instrument in use should be checked regularly. If necessary (the instrument is frequently used or in a critical confirmation state), an intermediate self-check should be carried out to determine its measurement performance. The coefficient error is within the allowable range, otherwise accurate data cannot be obtained. Special attention must be paid to the temperature of the sample being tested. Many users tend to ignore this point and think that the temperature difference is irrelevant. The actual experiment proves that when the temperature deviation is 0.5 ℃, the deviation of the viscosity value of some liquids exceeds 5%. Temperature deviation has a greater impact on viscosity, and viscosity decreases when temperature rises. Therefore, special attention should be paid to keeping the temperature of the measured liquid constant near the specified temperature point. For accurate measurement, it is best not to exceed 0.1°C. Selection of measuring container (sample cup). For the dual-cylinder measuring system, please read the instructions carefully. Different rotors (inner cylinders) need to be matched with corresponding outer cylinders (sample cups), otherwise the measurement results will have great deviations. For a single-cylinder rotational viscometer, in principle, the radius of the outer cylinder is infinite. In actual measurement, the inner diameter of the outer cylinder, that is, the measuring container, is not less than a certain size. For example, the laboratory standard rotational viscometer produced by Brookfield in the United States requires a 600mL beaker for measurement.

Choice of rotor and speed. Correctly select the rotor or adjust the speed so that the torque percentage of the reading is between 10% and 100%. If the torque percentage is too low, the measurement reading is invalid; if it is too high, the measurement is over-range and there is no reading. The depth of the rotor immersed in the liquid and the influence of air bubbles. Rotational viscometers have strict requirements on the depth of the rotor immersed in the liquid, and must be operated in accordance with the instructions (some double-tube instruments have strict requirements on the amount of liquid to be measured, and must be measured with a measuring cylinder). The rotor is often immersed in liquid with bubbles, and most of the bubbles will rise and disappear after the rotor has rotated for a period of time. Air bubbles attached to the lower part of the rotor sometimes cannot be eliminated.

Clean the rotor in time. The measuring rotor (including the sample cup) should be clean and free of dirt. Generally, it should be cleaned in time after the measurement, especially after the paint and adhesive are measured. Once the sample is measured with a dirty rotor, it will usually have an unpredictable effect on the measurement result.