FISCHER FISCHERSCOPE X-RAY XDLM 231, Operator'S Manual

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Measurement device monitoring for the Fischerscope X-RAY Calibration of X-ray fluorescence measuring instruments
108 FISCHERSCOPE
®
X-RAY
coating thickness and to a limited degree in the composition of the
coatings and of the substrate material. The calibration standards
must exhibit known coating thicknesses, and for the analysis,
known compositions
(nominal values) .
To this end, the supplier of the calibration standards measures
them against
higher-value master standards with secured nominal
values.
A certificate confirms the
traceability , describes the method how the
nominal values have been determined and may also indicate the
test conditions, the nominal values and their measurement
uncertainties.
Through the calibration, the nominal values of the standards are
transferred to the measurement application. Thereafter, the
measured coating thicknesses and concentrations are
correct , as
long as the calibration standards are labeled correctly. After each
calibration, the calibration is checked by
re-measuring the
standards to ensure that all entries have been correct and that the
calibration indeed leads to correct results. These check
measurements should be documented in the same manner as all
other test measurements.
Trueness
The instrument will then measure the coating thicknesses of other
specimens that correspond in coating structure and substrate
material to the measurement application
correctly as well. The
trueness of measurements is a quality that is particularly important
because supply contracts for coated products often require the
observance of specification limits. Wrong or incorrect
measurements can then lead to unwarranted acceptance or
rejection. The trueness aids in avoiding non-conforming
measurement results both within the production and between
supplier and customer. A measurement must be based on
calibration standards and be traceable. Only then is it correct. If
calibration standards do not exist or are not available for certain
measurement applications, then reference samples that have been
measured using a calibrated measurement application or have
been measured standard-free shall assume their roll
(documentation is required; see Fischer Application Report
vr 9812).
Strictly speaking, a ”correct” measurement is secure only for such
samples that correspond to the calibration standards in their
coating structure and composition. WinFTM allows for certain
differences between the structure of the sample and that of the
standard, e.g., differences in the substrate material. Although these
differences are physically taken into account correctly, for formal
reasons they require documentation.