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What matters should be paid attention to when using a rotational viscometer? According to the response of the after-sales department, some customers are using the rotational viscometer. Improper operation makes the data inaccurate, so that the instrument often fails and the service life is shortened. Based on this problem and the measurement principle, Xiamen Haida must pay attention to the following points in order to obtain accurate and reliable measurement data:

1. The performance indicators of the instrument must meet the requirements of the national metrological verification regulations:

1. The instruments in use should be checked periodically.

2. When necessary (the instrument is frequently used or in a critical state of being qualified), the viscometer should conduct an intermediate self-examination to determine that its measurement performance is qualified.

3. The coefficient error is within the allowable range, otherwise accurate data cannot be obtained.

2. Selection of measuring container (outer cylinder):

1. For the double-cylinder rotational viscometer, read the instrument manual carefully, and different rotors (inner cylinders) match the corresponding outer cylinders, otherwise the measurement results will deviate greatly.

2. For a single-cylinder rotational viscometer, in principle, the radius of the outer cylinder is required to be infinite. In actual measurement, the inner diameter of the outer cylinder, that is, the measuring container, is required to be no less than a certain size.

3. For example, the ndj-1 rotational viscometer produced by Shanghai Yutong Instrument Factory requires that the diameter of the beaker or straight cylindrical container used for measurement is not less than 70mm.

4. 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.

3. Pay special attention to the temperature of the liquid to be measured:

1. Many users ignore this and think that the temperature difference does not matter,

2. Our experiments have shown that when the temperature deviation is 0.5°C, the viscosity value of some liquids has a deviation of more than 5%, and the temperature deviation has a great influence on the viscometer. The temperature increases and the viscosity decreases.

3. Therefore, special attention should be paid to keep the temperature of the liquid to be measured constant around the specified temperature point, and it is best not to exceed 0.1°C for accurate measurement.

4. Select the rotor correctly or adjust the speed so that the displayed value is between 20 and 90 grids:

1. This type of instrument adopts the dial and pointer method to read,

2. Its stability and reading deviation are combined with 0.5 grids. If the reading is too small, such as around 5 grids, the relative error caused is more than 10%.

3. If the appropriate rotor or speed is selected so that the reading is within 50 divisions, the relative error can be reduced to 1%.

4. If the value of the rotational viscometer is above 90 bars, the torque generated by the hairspring will be too large, which will easily cause creep and damage the hairspring. Therefore, the rotor and speed must be selected correctly.

5. Cleaning of the rotor:

1. The rotor (including the outer cylinder) for measurement should be clean and free of dirt

2. Generally, the viscometer should be cleaned in time after measurement, especially after measuring paint and adhesives.

3. Pay attention to the cleaning method. It can be soaked in a suitable organic solvent. Never use a metal knife to scrape hard, because serious scratches on the surface of the rotor will cause deviations in the measurement results.

6. The depth of the rotor immersed in the liquid and the influence of air bubbles:

1. The rotational viscometer has strict requirements on the depth of the rotor immersed in the liquid, and must be made in accordance with the requirements of the instructions (some dual-cylinder instruments have strict requirements on the amount of liquid tested, and must be measured with a graduated cylinder).

2. In the process of immersing the rotor in the liquid, there are often bubbles, and most of them will float and disappear after the rotor rotates for a period of time. Sometimes the bubbles attached to the lower part of the rotor cannot be eliminated. So tilting and slowly immersing the rotor is an effective method.

7. Frequency correction:

1. For domestic instruments whose nominal frequency is 50 Hz, and the current power supply frequency in my country is also 50 Hz, we use a frequency meter to test the variability of less than 0.5%, so the general measurement does not require frequency correction.

2. But for some instruments in Japan, Europe and America, the nominal frequency is 60hz, and frequency correction must be performed, otherwise a 20% error will occur. The correction formula is: Actual viscosity = indicated viscosity × nominal frequency ÷ actual frequency

Eight, viscometer Other issues that need attention:

1. Most instruments need to be leveled. After replacing the rotor and adjusting the height of the rotor, pay attention to the leveling problem at any time during the measurement process, otherwise the reading will be deviated or even impossible to read.

2. Some instruments need to be equipped with a protective frame. Read the instructions carefully and install them according to the regulations, otherwise the reading will be deviated.

3. Determine whether it is an approximate Newtonian fluid. For non-Newtonian fluids, the rotor, rotation speed and rotation time should be specified after selection, so as to avoid misunderstanding that the instrument is inaccurate.