Metrohm 840 PC Control 5.0 / Touch Control - Manual (Page 283)

4 Parameters
PC Control / Touch Control
271
• Function : Selects the possible working steps.
With Dosing the given volume is added. Automatic filling takes
place neither before nor after the command.
Fill
the cylinder can take place from a freely selectable port. The
valve disk then remains at the selected port.
With Aspirate liquid is aspirated via the given port. As with Dosing,
the cylinder is not automatically filled either before or after the
command. It should be possible for the aspirated volume to be re-
moved with a single piston stroke.
With the Eject function the whole cylinder content is ejected via the
given port. In contrast to the function "End volume" the piston is
pressed down to the stop, i.e. past the maximum volume mark. This
command should only be used for preparing the dosing unit before
the pipetting sequence.
With the command Exchange position the cylinder is filled via the
given port. This means that, for example, air can be aspirated via
Port 4. The valve disk is then rotated to Port 2 and the dosing drive
can be removed from the dosing unit.
With Change port the valve disk is only moved to the given port; no
piston movement takes place.
As the dosing units are exchangeable, the coupling of the Dosino
piston rod (spindle) has a slight mechanical tolerance that can be
noticed when the piston changes its direction of movement. This
tolerance can be compensated with the command Compensate. A
short piston movement is first made in the same direction as the
previous movement; this is followed by a piston movement in the
reverse direction.
The whole cylinder content is ejected via the selected port with End
volume . The piston is lowered to the maximum volume mark i.e. un-
til 10'000 pulses have been dosed. This command should be used
for pipetting functions to empty the cylinder.
• In-/Outlet: Selects the port, with which the liquid handling com-
mand should be carried out.
• Volume: Here you enter the volume to be processed.
• Rate: Rate at which the commands Dosing, Fill, Aspirate, Eject,
Exchange position and End volume are carried out. Aspirating
and ejecting the sample should be done with a rate < 10 mL/min.
The item Control device is mentioned in Section 4.10.1, the parame-
ters for the Dosing device are described in Section 4.1.5.
A schematic command sequence is explained in Section 6.5.3.