Medical centrifuge is a specialized equipment for rapid separation, concentration and purification of different sedimentation coefficient mixtures by centrifugal force generated by high-speed rotation. It is widely used in medical and health, blood stations, pharmaceutical plants, biomedical engineering, animal and plant research and other fields. However, there is no suitable technical means and calibration method in the direction of metrology and detection. Therefore, laboratory instrument--Hunan Gilson proposed the research of calibration method of medical centrifuge, which will greatly develop the development of medical centrifuge technology in the field of metrology. The driving force.
1 Overview
A medical centrifuge is a device that produces constant acceleration. An instrument widely used in medicine, biology, and pharmacology to separate particles suspended in a solution and to separate two different densities of different densities. liquid. It usually consists of a platform, a control system, a test parameter measurement display system and its ancillary equipment. According to the structure of the platform, it can be divided into two types: rotary type and rotary arm type.
2 Measurement characteristics
(1) Speed ​​indication error: The relative error of the high speed centrifuge speed does not exceed ±1%, and the relative error of the low speed centrifuge speed does not exceed ±2.5%.
(2) Speed ​​stability: no more than ±1%.
(3) Machine noise: (A weighting) should be no more than 90dB.
(4) Timing relative deviation: The relative deviation of the digital timing device should be no more than ±1%; the relative deviation of the mechanical timer should be no more than ±5%.
(5) Lifting speed time: The speed up time of the centrifuge should be ≤10s, and the speed reduction time should be ≤10s.
3 Calibration conditions
3.1 Environmental conditions
(1) Temperature: (10 ~ 40) ° C;
(2) Relative humidity: (30 ~ 85)%;
(3) Voltage variation range: 10% of rated voltage;
(4) There should be no corrosive gas or liquid around the centrifuge environment; no strong electromagnetic interference; no vibration interference.
4 Calibration method
4.1 Appearance
(1) The centrifuge shall have a nameplate indicating the model, specification, manufacturer, manufacturing measuring instrument license mark and number, factory number and date.
(2) Centrifuge control and measurement should be fully equipped, and each connector should be connected reliably; each switch, knob and button should function normally, operate flexibly and reliably, and should have obvious text or symbol description; display part, character It should be clear and complete.
4.2 Speed ​​indication error
The centrifuge is unloaded, and three speed setting values ​​are uniformly selected within the maximum speed range of the centrifuge, and each measurement is performed three times. The indication value of the centrifuge speed and the indication value of the calibration tachometer are recorded, and the rotational speed indication error is according to the formula (1) The calculation shall comply with the provisions of 4.1.
[δ=n-nini×100%] (1)
Where: [δ] - speed indication error;
[n] - average of 3 measurements;
[ni] - Display value of the centrifuge at the i-th speed point.
4.3 Speed ​​stability
The centrifuge is idling, and the centrifuge is adjusted to the maximum speed. After the speed is stable, the speed is measured every 2 minutes with a 0.1-speed tachometer, and the total speed is measured 5 times. Calculate the average value, and then calculate the rotational speed stability by using equation (2). Take the maximum or minimum value, which should meet the requirements of 4.2.
[Sn=nmax(nmin)-nn×100%] (2)
Where: [Sn] - speed stability;
[nmax] - the actual maximum speed;
[nmin] - the actual minimum speed;
[n] - the average of 5 measurements.
4.4 Machine noise
(1) The centrifuge is unloaded, and the centrifuge speed is adjusted to the maximum to make it work normally. The sound level meter A-level weighting network is used for 5 measurements at a distance of 1 m from the front of the machine. The results should meet the requirements of Article 4.3.
(2) Stop the centrifuge and measure the background noise at the same position. When the background noise is more than 10 dB lower than the measured centrifuge noise value (A weighting), the measured value is not corrected. When 4dB~10dB, it is corrected according to the provisions of Table 3. When it is 4dB or less, the measured value is invalid.
[x=xin] (3)
Where: [x] - arithmetic mean of noise, dB(A);
[xi]——The noise value of the number of measurements is i, dB(A);
[n] - number of measurements.
Table 3 Background noise correction value is in decibels
Note 1: K indicates the value to be subtracted from this measured value.
Note 2: The background noise needs to be corrected during quality arbitration.
4.5 Timing relative deviation
With the electronic stopwatch at the set value of 5min and 10min, the relative deviation between the measured time measured value and the set value shall comply with the provisions of 4.4.
Timing relative deviation = [t-ΔtΔt × 100%]
Where: [t] - actual measurement time;
[Δt] - set value.
4.6 Lifting speed time
(1) Adjust the centrifuge to the maximum speed and prepare the timing with an electronic stopwatch.
(2) Start the centrifuge and measure the time required for the rotor to rise from 0 to the maximum speed, which is the speed up time. When the rotor of the centrifuge is at the highest speed and the speed is stable, press the stop button to measure the time required for the rotor to drop from the maximum speed to 0, which is the speed reduction time. The calibration results should be in accordance with 4.5.
This article was edited by the laboratory instrument - Hunan Gilson Technology Development Co., Ltd.
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