How does a blood centrifuge calculate the centrifugal force and the rotational speed?

How to calculate centrifugal force and rotation speed on a blood centrifuge

The centrifugal force applied to the specimen in the centrifuge depends on the rotational speed of rotation (RPM) and the radius of rotation. If you know the rotational speed of the centrifuge (RPM), you can calculate the centrifugal force using the following formula:

Relative centrifugal force (G-force) = 0.00001118 * radius of rotation * (RPM) ²

The radius of rotation mentioned in the above formula is that the centrifuge is equipped with a test tube for rotation to produce a circumference, and the radius of the circumference is the radius of rotation in centimeters (cm). For the following figure, the rotor has a radius of rotation of 12.7 cm.

Different people have different definitions of the radius of rotation. As shown in the figure below, some people consider the distance from the top of the test tube clamp to the center of the rotor as the radius of rotation. We mark it as R-min. Some people define the distance from the middle of the tube clamp to the center of the rotor as the radius of rotation. We mark it as R-avg. Some people use the distance from the bottom of the test tube clamp to the center of the horizontal rotor as the radius of rotation. We mark it as R-max. Through our research on the relevant standards of the industry, we recommend using the R-max maximum radius of rotation to calculate the corresponding centrifugal force (g -force).

RPM represents the speed of rotation per minute. This parameter is the speed at which the manufacturer tells the user that the machine is rotating during the centrifugation process based on the central axis of the rotor. However, even if the rotational speed (RPM) is the same, the centrifugal force (g-force) applied to the sample is different due to the difference in the radius of rotation. According to the formula listed we can see. The rotation speed (RPM) is the same, and the larger the radius of rotation (R-max), the larger the centrifugal force (g-force) we get. For example, we spin centrifugation at 3500RPM. The 15cm radius of rotation (R-max) can generate a centrifugal force (g-force) of about 2058xg. The 5cm radius of rotation (R-max) can produce a maximum centrifugal force of 686xg. -force).

Some users prefer to calculate the rotational speed (RPM) and centrifugal force (g-force) using a nomogram. We provide the following map. Once the user knows the centrifugal force (g-force) to be applied to the specimen, the user can measure the radius of rotation (R-max) of the rotor with the adapter and calculate the required rotation using the formula mentioned above or the nomogram below. Radius (RPM).

In summary, the user should always set the centrifugal force on the centrifuge to the correct value, rather than a rough rotation speed. Most clinical tube manufacturers will provide a description to inform the user of the recommended centrifugal force for the tube.

Some centrifugal machines have digital display devices that display and change the current rotational speed (RPM) and centrifugal force (g-force). In this case, the user can easily set the required centrifugal force directly on the centrifuge (g- Force), instead of converting the centrifugal force (g-force) into rotational speed (RPM) for setting. If the centrifuge used by the user does not display and set the centrifugal force (g-force), then the user needs to convert the centrifugal force (g-force) into the rotational speed (RPM) according to the above chart or formula, so as to set the corresponding setting on the centrifuge. Rotation speed (RPM).

For more information, please click on the Blood Centrifuge Selection Guide.