Hach-Lange TENSETTE plus User Manual - Handbuch (Seite 29)

Calibration
29
5.4.2 One point calibration
The one point calibration can be used if a single specific volume must
be calibrated. The calibration volume can be selected from the entire
volume range. Note that the inaccuracy of other volumes changes
also and the performance for other volumes cannot be assured.
1. Do the pipetting series with the calibration volume.
2. Calculate the results.
3. Select MENU and select OPTIONS with the scroll key and
accept with OK.
4. Select CALIBRATE and accept with OK.
5. Select ONE POINT and confirm with OK. The calibration volume
is shown on the display.
6. Select EDIT and change the calibration volume with the scroll
key and accept with OK.
7. Change the actual volume with the scroll key and accept with
OK.
8. A text SAVE? is displayed.
9. Accept with YES.
10. The adjustment has been changed.
5.5 Formulas for calculating results
5.5.1 Conversion of mass to volume
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 tareing 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
(71.5 °F) and 95 kPa ( Appendix Conversion table on page 77 ).
V = (w + e) x Z V = volume (µL)
w = weight (mg)
e = evaporation loss (mg)
Z = conversion factor for mg/µl conversion