OHAUS Guardian 2000 Manuel D'instructions page 12

EN-10
2 To turn on the stirrer, rotate the knob clockwise from the OFF position. The
illuminates to indicate that the stirrer is on.
3 To turn off the stirrer, rotate the knob counterclockwise and return to the OFF
position. The
STIRRING OPERATING TIPS
The stirrer increases speed at a steady rate until the setpoint is reached. If the
stirrer is not reaching its setpoint: 1) the stir bar may be too large, 2) the liquid may
be too viscous, 3) the setpoint speed may need to be reduced. Additionally, the
magnetic strength of stir bars reduce over time and may need to be replaced. Apart
from that, the bottom surface of the vessel can affect the stirring performance of the
magnetic stir bar. Adjust the vessel being used or change the stir bar to optimize
mixing in the sample.
When heating and stirring a reaction vessel within an oil bath or similar set-up, the
stirring function will stir up to approximately one inch (2.5 cm) from the top plate.
The stirring speed will vary according to liquid viscosity, spin bar length, and
distance from top plate. Adjust one or all of these to achieve the desired stirring
speed. For example: the closer the reaction vessel is to the top plate, the strong the
magnetic connection between the unit and the stir bar.
3.4. Controlling the Top Plate Heater
1 Rotate the left knob to control the heat setting.
a) Clockwise rotation will increase the heat setting.
b) Counterclockwise rotation will decrease the heat setting.
2 To turn on the heater, rotate the knob clockwise from the OFF position. The
illuminates to indicate that the heater is running.
3 To turn off the heater, rotate the knob counterclockwise and return to the OFF
position. The
light turns off to indicate that the stirrer is off.
light turns off to indicate that the heater is off.
Guardian TM Hotplate-Stirrers