Metrohm 893 Professional Biodiesel Rancimat - Manual (Page 32)

4.2 Calibration functions
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893 Professional Biodiesel Rancimat
Figure 14 Measuring arrangement (schematic representation)
1 Reaction vessel 2 Sample
3 Heating block 4 Measuring vessel
5 Conductivity measuring cell 6 Measuring solution
4.2 Calibration functions
4.2.1 Determining the cell constant
The cell constant of the conductivity sensor (6.0913.130) is normally at
1.1 ± 0.1 cm-1. This accuracy is sufficient for an induction time determi-
nation since only the shape of the curve is evaluated. For the determina-
tion of the stability time, however, the conductivity change is measured
in absolute terms. As a rule, the time until an increase in conductivity of
50 µS/cm is determined. The cell constant for the conductivity electrode
being used has to be calibrated in order to be able to measure the con-
ductivity correctly.