52
Release:
09/2008
CyBi
®
-Well
Manual
Operation
7.5
Specific Pipettor Features
Liquid
volumes
are
aspirated
and
discharged
by
piston
motion.
The
piston
suspension
point
has
a
mechanical
freeplay
(slackness).
This
means:
after
each
reversal
in
piston
motion
direction,
the
piston
drive
will
cover
a
certain
motion
length
without
actually
moving
the
piston
and
aspirating
or
discharging
a
volume
of
liquid.
This
motion
length
corresponds
to
the
freeplay.
In
order
to
prevent
dosing
errors,
a
volume
cycle
is
organized
in
such
a
way
that
the
pis-
ton
reversal
point
lies
outside
of
the
actual
pipetting
range
(motion
into
zero-position,
aspiration
with
additional
stroke)
or
is
corrected
by
suitable
compensator
motion
(dis-
pense
with
additional
stroke).
Aspirate with additional stroke
Fig. 11:
Aspirate with additional stroke
This
is
the
recommended
standard
procedure
for
precise
pipetting.
Piston
motion
starts
in
zero-position
(1)
and
continues
beyond
the
position
that
corre-
sponds
to
nominal
pipetting
volume.
The
pistons
are
then
lowered
back
into
this
posi-
tion
(2).
The
amount
of
freeplay
(3)
is
excluded
by
this
procedure.
During
direction
1
Zero-position
2
Aspirate
volume
with
additional
stroke
and
piston
reversal
3
Upper
freeplay
4
Dispense
exact
volume
(single
volume
or
subvolume)
5
Residual
dispensing
6
Move
to
zero-position
A1
=
D2:
nominal
pipetting
volume
A2:
additional
aspiration
volume
D1:
additional
volume
dispensed
<
A2
(additional
stroke)
D2:
nominal
pipetting
volume
D3:
residual
volume
(proportional
to
freeplay)
D4:
air
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