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21 Heating (only on centrifuges with heating/cooling option)
During operation of the centrifuge the centrifuge chamber can be heated as required to the preselected temperature.
The heating is switched off when the rotor is stationary.
Risk of burning! The surface temperature of the heating element in the centrifugal chamber of the centrifuge
can reach 500°C / 932°F. Do not touch the heating element.
The plastic buckets, order no. 5091, may only be used for temperatures up to a maximum of 40°C.
22 Relative centrifugal force (RCF)
The relative centrifugal force (RCF) is given as a multiple of the acceleration of gravity (g). It is a unit-free value and
serves to compare the separation and sedimentation performance.
These values are calculated using the formula below:
1,118
r
2
1000
RPM
RCF
u
u
¸
¹
·
¨
©
§
1000
1,118
r
RCF
RPM
u
u
RCF = relative centrifugal force
RPM = rotational speed (revolutions per minute)
r = centrifugal radius in mm = distance from the centre of the turning axis to the bottom of the centrifuge.
For more on the centrifugal radius see the chapter ” Anhang/Appendix,
Rotoren und Zubehör/Rotors and accessories”.
The relative centrifugal force (RCF) stands in relation to the revolutions per minute and the centrifugal
radius.
23 Centrifugation of materials with higher density
The rotors are designed to centrifuge substances up to a maximum mean homogenous density of 1.2 kg/dm
3
when
rotating at the stated speed.
Denser substances must be centrifuged at lower speed.
The permissible speed can be calculated using the following formula:
speed
Rated
x
density
Greater
1.2
=
)
(n
speed
Reduced
red
e.g.: RPM 4000, density 1.6 kg/dm
3
RPM
3464
=
4000
x
1.6
1.2
=
n
red
If in doubt you should obtain clarification from the manufacturer.
24 Rotor Identification
After every start of a centrifugation run the rotor utilised is identified.
After a change of rotor the drive switches off and the rotor code (R xx) as well as the maximum rotational speed
(n-max=xxxxx) of the rotor are displayed.
A further operation of the centrifuge is only possible after a single opening of the lid.
If, following a rotor change, the maximum speed of the rotor is less than the set speed, the speed is limited to
the maximum speed of the rotor.
