For medical centrifuges, choose the right one—not necessarily the most expensive.

　　 Medical centrifuge It’s a machine that generates centrifugal force, which depends on the rotor radius, rotational speed, and sample mass—specifically, F = Rmω² (where F is the centrifugal force, R is the radius, m is the sample mass, and ω is the rotational speed). Centrifugal force is one of the most important parameters for evaluating a centrifuge, and it also serves as a key criterion for distinguishing between different levels of centrifuge performance. When medical centrifuges leave the factory, they typically specify both their maximum rotational speed and the corresponding maximum centrifugal force. As we all know, the rotor radius and sample mass remain constant during operation; only the rotational speed can be adjusted through control. Therefore, we often use rotational speed as the standard way to describe a centrifuge—for example, “high-speed centrifuge” or “ultra-high-speed centrifuge.”
　　When a medical centrifuge’s rotor spins at high speed, air friction generates heat, causing the rotor’s temperature to rise and, consequently, the temperature of the sample in the tubes to increase as well. Since biological samples are sensitive to temperature, centrifugation experiments generally require that the temperature be maintained at 4°C. Without intelligent technology controlled by a computer, it would be impossible to achieve an accuracy of ±1°C. Therefore, refrigeration units are used to cool the centrifuge chamber, thereby cooling both the rotor and the sample. However, measuring the actual temperature of a rotating rotor is extremely challenging. Both domestically and internationally, temperature sensors are typically placed near the rotor at the bottom of the centrifuge chamber to indirectly measure the rotor’s temperature. In this case, the sample temperature Tsample equals the chamber temperature Tchamber plus a compensation term Tcompensation. The compensation term Tcompensation, in turn, depends on the rotor’s type, its rotational speed, and the duration of operation.
　　A medical centrifuge operates by using a motor to spin the rotor at high speed. In the past, these motors were DC motors equipped with carbon brushes. During operation, the carbon brushes wore down, producing sparks, noise, and even vibrations. Moreover, carbon brushes had a limited lifespan, requiring replacement before the motor could resume functioning. Even more serious was the pollution caused by the wear of carbon brushes, which generated carbon dust. This contamination not only affected the centrifuge itself but also spread to the surrounding environment—a type of pollution that is entirely unsuitable for the healthcare industry.
　　A typical manifestation of analog technology is adjusting operation parameters—such as rotational speed, temperature, and time—by turning knobs, with the data displayed by pointers on a dial. Its drawbacks include: the selection of parameters and the reading of data are heavily influenced by human factors, such as operator and reader variability, leading to poor control accuracy. Moreover, this process must be repeated every time, resulting in poor repeatability. Some... Medical centrifuge Although digital displays (such as those that show values selected by a knob) represent an improvement in readability, the underlying principle of value acquisition remains analog technology. A typical digital display features a user-friendly interface, keyboard operation, digital readout, and fully computer-controlled programmable functions. At its core lies intelligent control, which is realized by a computer. All parameters required for operating a medical centrifuge—such as rotational speed, temperature, duration, acceleration/deceleration rates, and others—are entered via keyboard input and displayed digitally. As a result, the error in selecting and reading operational parameters is extremely minimal. Moreover, since the system is programmable, a set of operational parameters can be assigned a specific code number for easy storage and retrieval.
　　This is because the motors used in medical centrifuges are typically series-wound motors. Such a motor consists of two main parts: the stator and the rotor. The stator comprises a centralized, fixed magnetic pole made up of an iron core and magnetic field coils. The rotor, on the other hand, consists of an iron core, rotor coils, and a commutator. The brushes play a crucial role in connecting the stator coils to the rotor coils via the commutator. The operating principle of the series-wound motor's circuit is as follows: current flows from the power source through the stator’s magnetic field coils, then through the brushes, across the commutator, into the rotor coils, and finally returns to the power source via the brushes and the stator’s magnetic field coils, thus completing the circuit. The magnetic field coils and rotor coils are connected in series through the commutator and brushes. Since the current remains constant throughout the circuit, the motor can only operate normally at the desired speed if the series circuit remains unobstructed and free of any breaks. Therefore, it is evident that the operational condition of the brushes directly affects the smooth running of the motor. However, due to factors such as wear, consumption, or spring failure during the brushes’ contact with the commutator, the brushes can easily become open-circuited or lose contact with the commutator—this being the primary cause of centrifuge shutdowns or reduced rotational speeds.
　　Medical centrifuges are commonly used in hospital laboratories to centrifuge blood, separating the serum and blood cells into distinct layers after centrifugation. The serum obtained through this process is then used for various biochemical tests. Therefore, medical centrifuges are essential equipment in laboratory departments. There are many different types of centrifuges available. Medical centrifuge Typically, these are low-speed centrifuges with a rotation speed of around 4,000 rpm; centrifuging for 5 to 10 minutes is usually sufficient. If the rotation speed is too low or too high, the centrifugation effect will not be optimal.