Metrohm 746 VA Trace Analyzer User Manual

Page 481

6 Data processing and evaluation

746 VA Trace Analyzer / 747 VA Stand

6-18

6.7.5

Baselines for PSA curves

With curves recorded with the measurement mode

PSAMODE

, there is no possibility

to select a method to calculate the baseline, the corresponding baseline parame-

ters are missing on the dialog page "SUBSTANCES".
The baseline is calculated automatically with the predetermined parameters

Type

linear

and

Scope

whole

. The baseline is determined by the tangent method

where, starting from the automatically determined peak base points

dU.front

and

dU.rear

, an iterative search is made within a fixed range for identical slopes. The

range of the tangent search is ca. 20 mV outward and inward up to 1 point before

the peak maximum.
If two points with identical slopes are found, the two points of tangency are con-

nected with each other to give the linear baseline. If no common slope is found, the

linear baseline is drawn directly between the two base points.

The two base points

dU.front

and

dU.rear

are only displayed

and can not be changed. On the

other hand, it is possible to dis-

play the subtracted curve

subtracted

to check the

evaluation (see section 6.7.4).

PSA

dU.front dU.rear

Point of tangency

(rear)

Subtracted

curve

Base point

(front)

Range for

tangent search