9
Enter value into test record.
►
7. Place weighing vessel on the balance and record weighing value.
8. Tare balance again.
9. Repeat steps 5 - 8 ten times (for multichannel pipettes ten times per channel).
Enter weighing values into test record.This results in a minimum of 24 (8-channel) resp.
►
36 (12-channel) weighing values.
10. Afterwards, repeat the same procedure for 50% and 100% of the nominal volume. Always start
with step 4.
Enter the weighing values into the test record. This results in 30 values for the singlechannel
pipette, in 72 values for the 8-channel pipette and 108 values for the 12-channel pipette.
►
6. Evaluation
The obtained weighing values from the gravimetric test are only the mass values of the pipetted
volume without the correction of the air buoyancy. To obtain the actual volume, a correction calc-
ulation taking into account the water density and the air buoyancy has to be carried out.
For multichannel pipettes, the following calculations have to be carried out for each channel seperately.
Mean weighing value (of one channel for multichannel pipettes)
x =
x + x + x ... + x
1
10
Example for 10 weighing values:
2
10
3
Mean volume (of one channel)
V = x · Z
Factor Z; see table
Enter value into the test record
►
►
Standard deviation volume (of one channel)
Factor Z; see table
Enter value into the test record
►
►
(x
1
– x)
2
9
s = Z ·
+ (x
2
– x)
2
+ (x
3
– x)
2
+ ... (x
10
– x)
2
+
