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Range Channel Volume Inaccuracy Imprecision
5-50 µl
50-300 µl
5-50 µl
50-300 µl
ADJUSTMENT (Fig. 7)
Adjustment is done with the service tool.
1. Place the service tool into the openings of the
calibration nut at the top of the handle.
2. Turn the service tool clockwise to increase, or
counterclockwise to decrease the volume.
3. After adjustment check the calibration according to the
instructions above.
FORMULAS FOR CALCULATING RESULTS
Conversion of mass to volume
V = (w + e) x Z
Evaporation loss can be significant with low volumes. To
determine mass loss, dispense water to the weighing
vessel, note the reading and start a stopwatch. See how
much the reading decreases during 30 seconds (e.g. 6 mg
= 0.2 mg/s).
Compare this to the pipetting time from taring to reading.
Typically pipetting time might be 10 seconds and the mass
loss is 2 mg (10 s x 0.2 mg/s) in this example. If an
evaporation trap or lid on the vessel is used the correction
of evaporation is usually unnecessary.
The factor Z is for converting the weight of the water to
volume at test temperature and pressure. A typical value
is 1.0032 µl/mg at 22°C and 95 kPa. See the conversion
table on page 18.
Inaccuracy (systematic error)
Inaccuracy is the difference between the dispensed
volume and the selected volume of a pipette.
A = V - V
0
Inaccuracy can be expressed as a relative value:
A% = 100% x A / V
Imprecision (random error)
Imprecision refers to the repeatability of the pipettings. It is
expressed as standard deviation (s) or coefficient of
variation (cv)
n
S
(
V
S
=
i=1
n
Standard deviation can be expressed as a relative value (CV)
CV = 100% x S / V
µl
8
50
5
8
300
50
12
50
5
12
300
50
V = volume (µl)
w = weight (mg)
e = evaporation loss (mg)
Z = conversion factor for mg/µl conversion
A
= inaccuracy
V
= mean volume
V
= nominal volume
0
0
V
)
-
2
i
1
-
µl
±0.75
±0.25
±3.0
±2.3
±0.75
±0.25
±3.0
±2.3
s
=
standards deviation
v
=
mean volume
n
=
number of measurements
7
ENGLISH
%
s.d. µl cv%
±1.5
0.35 0.7
±5.0
0.10 2.0
±1.0
0.9
±4.6
0.8
±1.5
0.35 0.7
±5.0
0.10 2.0
±1.0
0.9
±4.6
0.8
0.3
1.5
0.3
1.5
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