Vitlab 1608002, Operating Manual, Page: 29 / 124

29
Mean value
x =
Σ
x
i
n
Mean volume
Accuracy*
Coefficient of Variation*
Standard Deviation
V = x · Z
100 s
V
CV% =
Σ
(x
i
– x)
2
n – 1
s = Z ·
V – V
0
V
0
A% = · 100
8. Checking the Volume
Depending on use, we recommend inspection of the instrument every 3 to 12 months. The cycle
can, however, be adjusted to individual requirements.
The gravimetric testing of the pipette volume is performed according to the following steps and is in
accordance with DIN EN ISO 8655, Part 6.
1. Set nominal volume
Set volume to the maximum volume indi-
cated on the instrument (see page 27 for
procedure).
2. Condition the pipette
Condition the pipette before testing by using
a pipette tips to aspirate and discharge the
test liquid (distilled H
2
O) five times. After
this, discard the pipette tips.
3. Carry out the test
a) Attach new pipette tips and prerinse one
time with test liquid.
b) Aspirate liquid and pipette it into the weigh-
ing vessel.
c) Weigh the pipetted quantity with an analyti-
cal balance. (Please follow the operating
manual instructions from the balance manu-
facturer.)
d) Calculate the volume, taking the tempera-
ture into account.
e) At least 10 pipettings and weighings in three
volume ranges (100%, 50%, 10% of nomi-
nal volume) are recommended for statistical
analysis.
Calculation for nominal volume V
0
x
i
= Weighing results
n = Number of weighings
Z = Correction factor (e.g. 1,0029 μl/mg at 20 °C, 1013 hPa)
Note:
Each individual channel must be tested
seperately.
*) = Calculation of accuracy (A%) and variation
coefficient (CV%): A% and CV% are calculated
according to the formulas for statistical control.
Note:
Testing instructions (SOPs) are available for
download at www.vitlab.de.