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How to Use Viscometer Correctly?

Date:2020-06-09

Viscosity meter is widely used to measure the dynamic viscosity of various fluids such as resins, inks, paints, paints, foods, medicines, adhesives and so on. Because of its simple structure, moderate price, convenience and practicality, it is very popular. In the long-term verification process, we found that many users, especially the testers of small and medium-sized enterprises, have some problems in the process of using the viscometer, and the performance of the tested instruments is often better than the requirements of the national metrological verification regulations. Or it has already reached Brookfield's calibration standards, but the user's data is very different when actually testing the sample.

Digital Rotational Viscometer

Digital Rotational Viscometer

How can we obtain accurate and reliable measurement results?

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

NO 1

Blacksmith need its own hardware! The performance index of the instrument must first meet the requirements of metrological verification regulations or meet the calibration standards of Brookfield manufacturers. The instrument in use should be subject to periodic verification. If necessary (the instrument is used frequently or in a critical state of qualification), an intermediate self-examination should be conducted to determine its measurement performance. The coefficient error is within the allowable range, otherwise accurate data cannot be obtained.

NO 2

Special attention must be paid to the temperature of the tested sample. Many users often ignore this point and think that the temperature difference does not matter. The actual experiment proves that: when the temperature deviation is 0.5 ℃, some liquid viscosity values deviation exceeds 5%. The temperature deviation has a great influence on the viscosity, and 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, it is better not to exceed 0.1 ℃ for accurate measurement.

NO 3

Selection of measuring container (sample cup). For the double-cylinder measurement system, please read the instructions carefully. Different rotors (inner cylinders) need to match the corresponding outer cylinders (sample cups), otherwise the measurement results will deviate greatly. For a single-cylinder rotary viscometer, in principle, the radius of the outer cylinder is infinitely large. 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 rotary viscometer produced by Brookfield in the United States requires a 600mL beaker for measurement. Experiments show that especially when using the No. 1 rotor, if the inner diameter of the container is too small, it will cause a large measurement error.

NO 4

Rotor and speed selection. 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 measured reading is invalid; if it is too high, the overrange is measured and there is no reading.

NO 5

The depth of the rotor immersed in the liquid and the influence of bubbles. The rotational viscometer has strict requirements on the depth of the rotor immersed in the liquid, and must be operated according to the instructions (some double-barrel instruments have strict requirements on the amount of liquid tested, which must be measured with a measuring cylinder). The rotor is often immersed in liquid with bubbles, and most of them will rise and disappear after a period of rotation of the rotor. The bubbles attached to the lower part of the rotor sometimes cannot be eliminated. The presence of bubbles will cause a large deviation in the measurement data, so 45 The slow tilt of the ° angle is an effective way to immerse the rotor.

NO 6

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 measuring the paint and adhesive. Once the sample is measured with an unclean rotor, it often introduces unpredictable effects on the measurement results.

Conclusion

Only when the viscometer is used correctly can accurate and reliable measurement data be obtained. Before measuring samples, you should first understand more about the correct operation method and precautions of the viscometer. Only in this way can the desired accurate measurement results be obtained.