Operation Manual

11
6. Withdraw the pipette vertically and touch
the tip against the inside wall of the test
water container.
7. Pipette the water into the weighing vessel,
touching the tip against the inside wall of
the vessel just above the liquid surface at an
angle of 30° to 45°. Withdraw the pipette by
drawing the tip 8-10 mm along the inner wall
of the weighing vessel.
8. Read the weight in mgs (m
i
).
9. Repeat the test cycle until 10 measurements
have been recorded.
10. Convert the recorded masses (m
i
) to volumes (V
i
)
V
i
= m
i
Z Z = correction factor (Table 1)
11. Calculate the mean volume (⊽) delivered:
⊽ = (∑V
i
)/10
12. For conformity evaluation calculate the
systematic error e
s
of the measurement:
in µl: e
s
= ⊽ - V
s
V
s
= selected test volume
or in %: e
s
= 100 (⊽ - V
s
)/V
s
13. For conformity evaluation calculate the
random error of the measurement:
as standard deviation s = ∑(V
i
- ⊽)
2
n - 1
n = number of measurement (10)
or as coefficient of variation CV = 100s/⊽
14. Compare the systematic error (inaccuracy)
and random error (imprecision) with the
values in the performance specifications
- (p. 97) or the specifications of your own
laboratory. If the results fall within the
specifications, the pipette is ready for
use. Otherwise check both systematic and
random errors and, when necessary, proceed
to the recalibration procedure (Chapter 11.2).
NOTE: Systemic error (inaccuracy) is the
difference between the dispensed volume and the
selected test volume. Random error (imprecision)
is the scatter of the dispensed volumes around
the mean of the dispensed volume. (ISO 8655-1.)
NOTE: Sartorius specifications are achieved in
strictly controlled conditions (ISO 8655-6). The
user should establish own specifications based on
the field of use and the accuracy requirements
placed on the pipette (ISO8655-1).