Discussion on calibration methods for Hershey's instrument medical centrifuges

Medical centrifuges are specialized equipment for the rapid separation, concentration and purification of mixed substances of different precipitation coefficients by centrifugal forces generated by high-speed rotation, and are widely used in medical and health, blood banks, pharmaceutical plants, biomedical engineering, animal and plant research and other fields
.

However, so far there is no suitable technical means and calibration methods in the direction of measurement and detection, so this paper proposes the study of medical centrifuge calibration methods, which will play a huge role
in promoting the development of medical centrifuge technology in the field of metrology.

1.
Overview Medical centrifuge is a device that generates constant acceleration, an instrument widely used in the fields of medicine, biology and pharmacology, for separating particles suspended in solution and separating two liquids
of different densities that are not mutually soluble.

It is usually composed
of a table, a control system, a test parameter measurement and display system and its auxiliary equipment.

According to the table structure, it can be divided into two types: rotary disc type and rotary arm type
.

2.
Measurement characteristics (1) speed indication error: the relative error of the speed of the high-speed centrifuge does not exceed ±1%, and the relative error of the speed of the low-speed centrifuge does not exceed ±2.
5%.


(2) Speed stability: not more than ±1%.


(3) The noise of the whole machine: (A weight) should not be greater than 90dB
.

(4) Relative deviation of timing: The relative deviation of the digital timing device should not be greater than ±1%; The relative deviation of the mechanical timer should not be greater than ±5%.


(5) Lifting and deceleration time: the centrifuge acceleration time should be ≤ 10s, and the deceleration time should be ≤10s
.

3.
Calibration conditions 3.
1 Environmental conditions (1) Temperature: (10~40)°C; (2) Relative humidity: (30~85)%; (3) Voltage change range: 10% of the rated voltage; (4) There should be no corrosive gas and liquid around the centrifuge environment; No strong electromagnetic interference; No vibration interference
.

3.
2 Calibration standards and other equipment Serial number Equipment name Measurement range and technical requirements 1 Digital tachometer Measuring range: (0~99999)rpm; 0.
1 class 2 electronic stopwatch measurement range: (0~3600)s; Resolution value 0.
01s 3 Sound level meter measurement range :(40~100)dB(A); Type II (A weighting) Technical requirements for calibration equipment and other equipment Table 4, calibration items and calibration methods 4.
1 Appearance (1) The centrifuge should have a nameplate indicating the model, specifications, manufacturing plant, manufacturing instrument license mark and number, factory number and date, etc
.

(2) The centrifuge control and measurement reality parts should be complete, and the inserts should be connected reliably; Each switch, knob, button should function normally, operate flexibly and reliably, and should have obvious text or symbol description; In the display part, the characters should be clear and complete 4.
2 speed indication error centrifuge is not loaded, 3 speed setting values are uniformly selected within the maximum speed range of the centrifuge, each 3 measurements are made, the centrifuge speed indication value and the calibration speed meter indication value, the speed indication error is calculated according to the formula, and should comply with the provisions of
4.
1.

4.
3 speed stability centrifuge is unloaded, the centrifuge is adjusted to the maximum speed, and the speed is measured every 2min with the 0.
1 stage tachometer after the speed is stable, and the total measurement is 5 times
.

Calculate the average, and then use the formula to calculate the speed stability, take its maximum or minimum value, should comply with the provisions of
4.
2.

4.
4 The whole machine noise (1) The centrifuge is unloaded, the centrifuge speed is adjusted to the maximum to make it work normally, and 5 measurements
are made with the sound level gauge A level weight network at a distance of 1m in front of the center machine.

The result shall be as follows in Article
4.
3.

(2) Stop the centrifuge work and measure the background noise
at the same position.

When the background noise is more than 10dB lower than the noise value (A weight) of the centrifuge being measured, the measured value is not corrected
.

In the case of 4dB to 10dB, it shall be amended according to the provisions of the following table; When below 4dB, its measurements are invalid
.

Difference between noise value and background noise 4 5 6 7 8 9 10 Correction value K 2.
2 1.
7 1.
3 1.
0 0.
8 0.
6 0.
4 Background noise correction value table Note 1: K indicates the value
that should be subtracted from this measurement.

Note 2 to entry: In quality arbitration, background noise correction is required
.

4.
5 The timed relative deviation with the electronic stopwatch has a setting value of 5min and 10min, and the relative deviation between the measured time measurement value and the setting value shall comply with the provisions of
4.
4.

4.
6 Lifting and lowering speed time (1) Adjust the centrifuge to the maximum speed, and prepare the chronograph
with an electronic stopwatch.

(2) Start the centrifuge and measure the time required for the rotor to rise from 0 to the maximum speed, that is, the speed increase time
.

When the rotor of the centrifuge is at the highest speed and keeps the speed stable, press the stop button to measure the time it takes for the rotor to drop from the maximum speed to 0, that is, the speed reduction time
.

The calibration results should comply with the provisions of
4.
5.

Hunan Hexi Hunan Hexi Instrument and Equipment Co.
, Ltd.
has been registered and established in Xiangjiang New Area since 2007, after more than ten years of development, it has now become a professional high-tech company integrating R&D, production and sales of laboratory instruments and equipment with independent intellectual property rights, independent brands and independent innovation capabilities, and the drafting
of national standards for centrifuges.

The company mainly produces high-speed refrigerated centrifuges, ultra-large capacity refrigerated centrifuges, low-speed refrigerated centrifuges, ambient centrifuges, crude oil moisture determination centrifuges, vacuum centrifuge concentrators, 3H series intelligent centrifuges and latex moisture rapid testers, and in the same industry first passed ISO13485 medical device quality management system certification, ISO9001: 2008 quality management system certification and CE certification
.

The company's products are widely used in military industry, scientific research institutes, colleges and universities, central blood banks, hospitals, biological products, pharmaceuticals, biochemical testing, agricultural science, environmental protection and petrochemical, food and other production and scientific research fields
.

Hexi Instrument has set up direct offices and after-sales service centers
in Beijing, Guangzhou, Nanjing, Shenyang, Harbin, Xi'an, Chongqing, Jinan, Kunming, Wuhan, Nanchang, Lanzhou, Changsha and other places.