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How to Convert RPM to Gs on a Beckman

A centrifuge works by making a hard metal part called a rotor revolve at a user-desired speed. Rotors have cavities into which test tubes can be inserted, and the contents of these tubes will have an acceleration (RCF, relative to the Earth's gravity g) that will be proportional to both the speed of rotation (measured in revolutions per minute, or RPMs) and the radius of rotation of the rotor (measured in millimeters). Because different rotors spinning at the same RPMs will result in different accelerations, it is useful to be able to convert RPM to RCF.

Things You'll Need

Rotor manual
Calculator

Instructions

- 1
  Look up the rotational radius in the rotor manual.
- 2
  Select the desired speed in RPM.
- 3
  Calculate RCF using the following formula:
  
  RCF = r w ^ 2 / g, where:
  
  RCF = Relative centrifugal field, or the ratio of the centrifugal acceleration caused by spinning to the Earth's gravitational acceleration
  
  r = The rotational radius of the rotor
  
  w = The angular velocity in radians per second
  
  g = The Earth's gravity (9807 mm/s^2)
- 4
  If the rotational radius is in millimeters and the angular velocity is in RPM, then you can use the following formula:
  
  RCF = 1.12 r ('/1000) ^2
- 5
  For example, a rotor with a rotational radius of 20 mm that spins at 50,000 RPM generates an acceleration of about 56,000 g, or 56,000 times the Earth's gravity.

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