Metrohm viva 1.0 (process analysis) - Manual (Page 607)

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5 Method
viva 1.0 (for Process analysis)
￭￭￭￭￭￭￭￭ 595
Nonlinear
regression y =
k(0)
+
k(1)
⋅ x +
k(4)
⋅ x 4
≥3
Linear interpola-
tion y =
k(0)
+
k(1)
⋅ x
≥2
At least three points are required for being able to generate a non-linear
or quadratic calibration. A suitable curve fit (quadratic or non-linear) must
be placed on the points so that the calibration curve is available in the
curve display and/or so that the calibration curve can be calculated. Fig. 1
shows the first three points of the calibration, which lie upon a line. This
curve can not be evaluated with a non-linear or quadratic curve type. For
the purposes of evaluation, the calibration curve must intersect the line
with the evaluation ratio and may not lie parallel to it.
Figure 1 Fig.: 1
An additional, fourth point is required for the calibration so that the non-
linear or quadratic function is laid on the points and so that extrapolation
can be carried out to the intersection point with the evaluation ratio (see
Figure 2, page 596).