Laboratory centrifuges are used in a wide range of fields, generally used in various laboratories such as hospital laboratories , scientific research institutions laboratories, food and drug inspection laboratories, food hygiene laboratories, etc., and the speed is not greater than 30000r/min. The speed of the laboratory centrifuge is a very important technical parameter. The magnitude of the centrifugal force is proportional to the speed of the laboratory centrifuge. If the speed does not meet the specified requirements, the suspension or emulsion cannot be effectively separated. During the testing process, different laboratory centrifuges may be used to separate the same substance, resulting in different conclusions, which will seriously affect the test results.
Since there are no laboratory centrifuge speed verification regulations and calibration specifications , the verification/calibration of centrifuges cannot be carried out. Therefore, it is necessary to discuss the calibration method of laboratory centrifuge speed.
The following is the description and uncertainty analysis and evaluation of the laboratory centrifuge speed calibration method .
1. Measurement performance of laboratory centrifuge (see Table 1)
2. Environmental conditions
Ambient temperature: (20±5)°C; relative humidity: ≤80%; no direct sunlight or direct radiation from other heat sources; no strong vibration and airflow around; pollution level 2, no conductive dust, explosive gas, high concentration around Dust or corrosive substances are present.
3. Measurement standard
According to the measurement performance of the laboratory centrifuge, the rotational speed measuring instrument requires the use of a rotational speed measuring instrument with an accuracy of more than 0.2%, and its expanded uncertainty U (k=2) should meet the calibration of the technical indicators of the tested laboratory centrifuge Requirements (that is, the value of the expanded uncertainty is not greater than 1/3 of the absolute value of the error).
4. Calibration items
Speed error, speed stability.
5. Calibration method
1. Calibration of speed error
Before calibration, the measuring equipment shall be sufficiently stabilized under the specified conditions.
Adjust the laboratory centrifuge loaded with a fully loaded rotor to the highest rated speed, stabilize it for 5 minutes, measure the speed of the centrifuge with a speed measuring instrument, measure once every 1 minute, measure 10 times in total, and calculate each time according to formula (1) The rotational speed error, take the maximum value.
