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Calibration FERITSCOPE® DMP30
9 Calibration
The term "calibration" is used in this Operator's Manual as a general term for deter-
mining the deviation from a reference value, adjustment and correction: calibration
of the gauge using calibration standards to adapt the measuring system (gauge and
probe) to the measuring application at hand.
The calibration sets the difference between nominal and actual value to zero.
To obtain comparable measurement results, the instruments must be adjusted or
calibrated using standards that can be traced to internationally recognized second-
ary standards.
A calibration is a reference measurement during which the measured values and de-
termined correction factors of the specimen are recorded and stored in a calibration
file in the connected probe, separate from the batch. The calibration standards used
at Fischer are traceable to internationally recognized secondary standards of the
National Institute of Standards and Technology (NIST) for ferrite number (FN).
In order to measure, it is absolutely essential that a calibration suitable for the mea-
suring application has been assigned to the batch.
The determination of the ferrite content is influenced by the following variables:
Geometry of the specimen (size of the reference area, curvature, distance of the
measurement location from the edge of the specimen, sheet thickness, clad-
ding thickness)
The correction of these influencing quantities should be carried out based on
the correction factors listed beginning on page 44.
Creating user-specific calibration standards to determine, for example the
influence of the curvature or thickness of the specimen is not recom-
mended because the -ferrite content of the starting material can be al-
tered even with most careful mechanical processing, especially in the
surface area that is registered by the probe.
Probe tip wear
To a certain degree, probe tip wear can be corrected through a calibration (be-
ginning on page 55). Too much probe tip wear, which becomes noticeable
through an increased scatter of the readings on a specimen with a homoge-
neous -ferrite content distribution (e.g., a calibration standard), cannot be cor-
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