Recall Hours Of Operation; Cooling (Only In Centrifuges With Cooling); Standby-Cooling; Pre-Cooling The Rotor - Hettich UNIVERSAL 32 Bedienungsanleitung

EN
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

Cooling (only in centrifuges with cooling)

The temperature set-point can be adjusted from -20°C to +40°C. The lowest obtainable temperature is dependent on
the rotor (see Chapter "Anhang/Appendix, Rotoren und Zubehör/Rotors and accessories").
18.1

Standby-cooling

With rotor standstill and closed lid the centrifugal chamber is cooled to the pre-selected temperature. The
temperature set-point is shown in the display.
18.2

Pre-cooling the rotor

For rapid pre-cooling of the unloaded rotor and the accessories, it is recommended that the centrifuge is run with the
continuous running settings and a speed of ca. 20% of the maximum rotor speed.
19

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.
20

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.
21

Rotor Identification

After every start of a centrifugation run the rotor utilised is identified.
After the rotor has been changed, the drive switches off and the maximum speed and the rotor code are displayed
briefly.
Afterwards, OPEN OEFFNEN is displayed and further operation of the centrifuge is only possible after opening
the lid once.
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.
20/56
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
×
1000
3
when