Two terms that centrifuge operators encounter are Revolutions per Minute and Relative Centrifugal Force. Revolutions per Minute, or RPM, is the measurement of how fast the rotor assembly of the centrifuge makes a full rotation in one minute. In other words, the RPM is how fast the centrifuge rotor assembly is spinning. The Relative Centrifugal Force also referred to as “g-force,” is a measurement of the gravitational force to which the sample is subjected. This force is generated from the spinning of the rotor assembly, which drives this force toward the centrifuge tubes.
Proper laboratory procedures in which centrifugation is an element will use RCF rather than RPM. This is because different centrifuges can run at the same RPM but have different RCFs. This is because the radius of their rotor assemblies differs. For example, you might have two centrifuges, both running at an RPM of 3,000, but their RCF differs because one centrifuge has a rotor assembly radius of 100 mm while the other centrifuge has a rotor assembly radius of 75 mm. With a slight adjustment of the RPM from 3,500 to 4,000, a centrifuge with a radius of 75 mm will result in having about the same RCF as the centrifuge with a radius of 100 mm.
