Acoustic Signal; Recall Hours Of Operation; Relative Centrifugal Force (Rcf); Centrifugation Of Materials With Higher Density - Hettich EBA 21 Mode D'emploi

16

Acoustic Signal

The acoustic signal sounds:
•
Upon the appearance of a disturbance in 2 second intervals.
•
After completion of a centrifugation run and rotor standstill in 30 second intervals.
The acoustic signal is stopped by opening the lid or pressing any key.
The signal after completion of the centrifugation run can be activated or deactivated in the following manner, if the
rotor is at standstill:
•
Hold down the key for 8 seconds.
After 8 seconds, SOUND / BELL appears in the display.
•
Set OFF or ON with the key
•
Press the key in order to store the setting.
START
As confirmation, ∗∗∗ ok ∗∗∗ will be displayed for a short period.
17

Recall hours of operation

Recall hours of operation is only possible during rotor standstill.
•
Hold down the key for 8 seconds.
After 8 seconds, SOUND / BELL appears in the display.
•
Press the key once again.
The centrifuge's hours of operation (CONTROL: ) are displayed.
•
Press the key or to exit the hours of operation recall.
18

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:
RCF
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.
The relative centrifugal force (RCF) stands in relation to the revolutions per minute and the centrifugal
radius.
19

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
rotating at the stated speed.
Denser substances must be centrifuged at lower speed.
The permissible speed can be calculated using the following formula:
Reduced speed (n )
red
e.g.: RPM 4000, density 1.6 kg/dm
1.2
n = x 4000 = 3464
red
1.6
If in doubt you should obtain clarification from the manufacturer.
or .
2
 
RPM
 
= × ×
r 1,118
 
1000
For more on the centrifugal radius see the chapter " Anhang/Appendix,
Rotoren und Zubehör/Rotors and accessories".
1.2
= x Rated speed
Greater density
3
RPM
RCF
⇒ =
RPM
×
r 1,118
EN
×
1000
3
when
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