Buchi DuMaster D-480, Руководство по эксплуатации

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Operating instructions DuMaster D-480 ©BÜCHI Labortechnik AG
4 - Understanding the instrument and planning its use 51
Background knowledge required for calibration
Important calibration principles
Perfect calibration of the instrument is a key condition for achieving correct analysis results. The
calibration has to be carried out over the whole measuring range.
For successful calibration the user must be familiar with the analyzer and the operating instructions.
The personnel performing calibration must therefore be authorized and must have undergone
appropriate training.
Purpose of instrument calibration
The analyzer does not measure the absolute content of an element in the sample but rather only
changes of the element portion in the combustion gases. These changes cause an electrical signal in
the detector that is recorded and integrated by the software depedent on time.
In order to create a correlation between the integrated detector signal and the absolute element
content of the analysis samples, a series of calibration samples with known element content and
different sample weights are measured. The software computes the calibration factors on the basis of
the known element contents and the sample weights of the calibration samples.
Conditions for perfect calibration
In order to be able to calibrate the instrument perfectly, the following conditions must be met:

The instrument must have passed the leak test.

The instrument blank values must be low and roughly constant.

Only use suitable substances of at least p.a. quality or certified standards as calibration samples.

The concentration values of the calibration samples must cover the whole measuring range.
When to calibrate the instrument
It is always necessary to calibrate the instrument when one of the following is true:

You have removed components that influence analysis results, e.g. the detector.

The daily factor for a measuring component is clearly outside of the range of 0.9 to 1.1. Also, it
displays fast changes in time from day to day.
Calibration formulae
The formulae used for calibration can be found in
Calibration formulae
(on page 54).
Calibration curve calculation method
For details on the various calibration curve calculation methods and when to use them, see
Calibration curve computation method criteria
(on page 52).
Notes on performing calibration
For details on practical implementation of calibration, refer to

the section Performing calibration.

the calibration tables.