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Compare this to the pipetting time from tareing to reading. Typically pipetting time might
be 10 seconds and the mass loss is 2 mg (10s x 0.2mg/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 1.0032µl/mg at 22°C and 95 kPa. See the conversion
table on page 47.
Accuracy (systematic error)
Accuracy is the difference between the dispensed volume and the selected volume of a pipette.
A = V -V
0
Accuracy can be expressed as a relative value: A% = 100% x A / V
Precision (random error)
Precision refers to the repeatability of the pipettings. It is expressed as standard
deviation (s) or coefficient of variation (cv)
n
S
(
V
S
=
i
i=1
n
-
When the Finnpipette Digital is not in use, make sure it is stored in an upright position.
We recommend a Finnpipette stand for this purpose.
SHORT-TERM CHECKING
The pipette should be checked at the beginning of each day for dust and dirt on the
outside surfaces of the pipette.
Particular attention should be paid to the tip cone. No other solvents except 70 %
ethanol should be used to clean the pipette.
LONG-TERM
MAINTENANCE
If the pipette is used daily it should be checked every three months. The servicing
procedure starts with the disassembly of the pipette.
DISASSEMBLING 0.2-50 µl PIPETTES
1. Press the tip ejector.
9
2. Insert the maintenance pliers under the ejector bar to release the tip ejector.
3. Remove the tip cone by pressing with maintenance pliers.
10
4. Pull out the piston and the spring.
5. Keep the tip cone vertically and push out with piston the rest of the piston assembly.
Then keep the tip cone upside down and tap all parts from tip cone.
Remember keep all parts in order on table for reassembly.
6. Clean the piston, the piston spring and the O-rings with a dry napless cloth.
A = accuracy
V = mean volume
V
= nominal volume
0
s = standards deviation
v = mean volume
V
)
-
2
n = number of measurements
cv is the relative value of standard deviation.
1
cv = 100% x s / v
MAINTENANCE
8
0
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