Glossary
89
MMS
®
Inspection DPM High
value). The measuring result is true if the difference of x - nominal value is close
to zero.
A significant difference can be caused by a poor calibration (nominal value in-
correctly entered, calibration foil incorrectly labeled, probe incorrectly posi-
tioned on the surface). Such systematic deviations cause different users, e.g.
supplier and customer, to obtain different results from the same test piece.
Please note that we consider trueness to be a property of the measured read-
ings. However, many people believe that trueness is a property of the gage! In
laymen's terms, this becomes a question of the "accuracy of the gage". True-
ness, though, is largely dependent on the setting (e.g. the calibration) and mon-
itoring of the gage. And these rely in turn on the skill and reliability of the user.
Because this is the case, the manufacturer of a gage cannot guarantee the true-
ness of the values measured by this gage or even affix a label stating the true-
ness of the measured readings on the gage. Every measuring result, then, is as
true or false as the user allows it to be. Therefore, trueness cannot be a crite-
rion for the quality of a gage. At most, it indicates its stability (trueness during
prolonged operation of the gage without the necessary corrective actions being
taken in that time).
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