BrandTech Scientific seripettor - Manual (Page 39)

English
Checking the Volume (Calibration)
Depending on use, we recommend that gravimetric testing of the instrument be carried out every
3-12 months. This time frame should be adjusted to correspond with individual requirements.
Gravimetric volume testing according to DIN EN ISO 8655-6 (for measurement conditions,
see 'Error Limits', page 38) is performed as follows:
39
* Calculation of accuracy (A %) and coefficient of variation (CV %):
A % and CV % are calculated according to the formulas for statistical control.
x
i
= results of weighings
n = number of weighings
Z = correction factor
(e.g., 1.0029 µl/mg at 20 °C, 1013 hPa)
V
0
= nominal volume
Mean volume
V – V
0
V
0
A% = · 100
Σ (x
i
– x) 2
n – 1
s = Z ·
Mean value x =
Σ x
i
n
Mean volume V = x · Z
Accuracy* Standard deviation Coefficient of variation*
100 s
V
CV% =
1.
Preparation of the instrument
Clean the instrument (Cleaning, page 40), fill it
with distilled H
2
O and then prime it carefully.
2.
Check the volume
a) 10 dispensing operations with distilled H
2
O in
3 volume ranges (100 %, 50 %, 10 %) are
recommended.
b) For discharge depress piston slowly and
steadily without force until the lower stop.
c) Wipe off the tip of discharge tube.
d) Weigh the dispensed quantity on an analytical
balance. (Please follow the operating manual
of the balance manufacturer.)
e) Calculate the dispensed volume. The Z factor
takes account of the temperature and air
buoyancy.
3.
Calculations