6 Stirring operation
50108226_02.2007
21
Thermo Scientific
The magnetic stirrer has a soft start feature that first centers the magnetic stirring bars
within the vessels and then slowly accelerates them to the desired speed. As long as
the asterisk symbol is still shown in the display (10), the selected speed has not been
reached yet.
6.3.4 Power adaptation
Cf. Table 4, Power menu.
Select
Higher power for larger quantities, higher speeds, viscous media, and
connection with several stirring drives via the bench-top terminal block
(see also Table 1).
Lower power for smaller quantities, lower speeds, media of watery
consistency, or if heating the area where the stirrer is placed or heat
emanation (e.g. in incubators) are undesirable.
Select the required stirring power in the Power menu.
While doing so, observe the stirring movement: The power setting is correct when the
stirring bar turns evenly and without jerking.
6.3.5 Mixing vertically (Shake)
CAUTION
If you selected the shake mode (vertical mixing):
Select the minimum speed setting and then increase it slowly.
Depending on the magnetic stirring bar used, you may be able to
perform vertical stirring only at lower speeds.
Cf. Table 4, Shake menu.
To avoid vigorous stirring movements, change the stirring mode to Shake. This will keep
the magnetic stirring bar from spinning, rocking it gently back and forth only. This helps
avoid excessive shear forces.
Select vertical mixing on the Shake menu.
Select the minimum speed setting and then increase it only slowly.
6.3.6 Interval operation
Cf. Table 4, Interval menu.
Even during continuous operation (e.g. overnight) it may be a good idea to interrupt the
stirring at regular intervals. After each pause, the stirring bars are being recentered.
This ensures that no stirring point is rendered inoperative for a longer period of time if a
stirring bar migrates away from the turning center.
Select the Interval submenu
Select Interval ON.
Select the desired stirring time (e.g. 30 s).
Select the desired pause time (e.g. 10 s).
The rotation speed is reduced at the end of every stirring period, and the stirring is
stopped. After every pause the stirrer is restarted. The direction of rotation is reversed,
the magnetic stirring bars are recentered and the rotation speed is slowly increased
again.
