Home > Knowledge > Content

Categories

How to deal with the data deviation when the user tests the sample in the rotary viscometer?

- May 25, 2018 -

The rotational viscometer is a new type of instrument for measuring the viscosity of liquids. Widely used to determine the viscosity of various fluids such as oils, paints, plastics, foods, drugs, adhesives, etc. The performance of our rotational viscometer is better than that of national metrological verification procedures. In particular, there are many problems in the use of SMEs' testers. Users have large deviations when testing samples.

The

First, the rotational viscometer to cycle test, if necessary (the instrument is used frequently or in a qualified critical state) to conduct an intermediate self-check to determine the measurement performance of qualified, coefficient error within the allowable range, otherwise can not obtain accurate data.

The

Second, pay special attention to the measured liquid temperature. Many users neglect this point and think that the temperature difference does not matter. Our experiments have proved that when the temperature deviation is 0.5°C, the viscosity of some liquids deviates by more than 5%. The temperature deviation has a great influence on the viscosity, and the temperature increases and the viscosity decreases. Therefore, special attention should be paid to keeping the temperature of the measured liquid constant near the specified temperature point, and it is better not to exceed 0.1°C for accurate measurement.

The

Third, the choice of measuring container (outer tube). For the rotational viscometer, read the instrument manual carefully. Different rotors (inner cylinders) are matched with the corresponding external cylinders, otherwise the measurement results will be greatly biased. For a single cylinder rotary viscometer, the radius of the outer cylinder is in principle required to be infinitely large. The actual measurement requires that the inner diameter of the outer cylinder, that is, the measurement container, be not less than a certain size. Experiments have shown that especially when the No. 1 rotor is used, a large measurement error is caused if the inner diameter of the container is too small.

The

Fourth, the correct choice of rotor or adjust the speed, so that the value between 20 to 90 grid.

The

Rotary viscometer uses dial and pointer readings, its stability and reading deviation together have 0.5 grids, if the reading is too small as near 5 grid, the relative error caused by more than 10%, if you choose the right rotor or speed With a reading of 50 cells, the relative error can be reduced to 1%. If the value is more than 90, the torque generated by the hairspring is too large, creep easily occurs, and the hairspring is damaged, so it is necessary to correctly select the rotor and the rotation speed.

The

Fifth, frequency correction. For domestic instruments, the nominal frequency is 50Hz, and our current power supply frequency is also 50Hz. We use the frequency meter to test the variability less than 0.5%, so the general measurement does not require frequency correction. The correction formula is:

The

Actual viscosity = indicated viscosity × nominal frequency ÷ actual frequency

The

Sixth, the depth of the rotor immersed in the liquid and the effect of air bubbles.

The

The rotational viscometer has strict requirements on the depth of the rotor immersed in the liquid and must be operated in accordance with the instructions (some binocular instruments have strict requirements on the amount of liquid to be tested and must be taken from the cylinder). When the rotor is immersed in the liquid, bubbles are often present. Most of the float will disappear after the rotor rotates. 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. Slowly immersing the rotor is an effective way.

The

Seventh, rotor cleaning. The measuring rotor (including the outer cylinder) is to be clean and free from dirt. It is usually cleaned after the measurement, especially after the paint and adhesive are measured. Pay attention to the cleaning method, soaking with a suitable organic solvent, do not use a metal knife and other hard scraping, because the rotor surface has serious scratches will bring about the deviation of the measurement results.


Related Industry Knowledge

Related Products

  • Handheld Brix Meter Refractometer for Fruit and Honey and Sugar Test
  • Pen Digital EC Meter
  • Viscosity Measurement Instruments
  • Benchtop Multimeter Analyzer Auto LCD Display with USB for Water Quality Testing
  • Bench Top PH Meter Auto  and High Precision Used for Testing the PH and MV Value
  • LAB Weighing Scale Balance Digital Electronic Large Scales Weighing Platform with High Precision