Metrohm 743 Rancimat - Manual (Page 74)

4.5 Methods ￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
66 ￭￭￭￭￭￭￭￭ 743 Rancimat
Range 0 ... 100 h
Evaluation suppression
Start
Time from the start of the determination to the start of the evaluation
suppression.
Range 0 ... 100 h
End
Time from the start of the determination to the end of the evaluation sup-
pression.
Range 0 ... 100 h
Evaluation sensitivity
This value defines the minimum value which the maximum of the curve of
the second derivative has to reach in order to be accepted as a result. The
result, i.e. the induction time, is the time until the first accepted maxi-
mum.
The default value "1" will lead to the correct result for most applications.
Smaller values will cause the acceptance of smaller maximums of the sec-
ond derivative. Higher values require a higher maximum.
Range 0.1 ... 9999
Induction time
The induction time is the time to the break point of the curve conduc-
tivity vs. time recorded with the Rancimat. The induction time is a parame-
ter for the oxidation stability of the sample examined and corresponds to
a large extent to the results from the complex AOM method.
For automatic determination of the induction time, the second derivative
of the measured curve is used, which exhibits a maximum at the break
point and which can be displayed in the window Live graph. To enable
detection of a break point, certain criteria must be fulfilled with regard to
the height and width of the peak in the second derivative. The break point
can also be determined manually as the intersection point of the two tan-
gents at the extended straight branches of the curve (see "Setting tan-
gents manually", page 116).