Page 224
Operator‘s Manual FERITSCOPE
®
FMP30
Glossary
Check function from the measurement readings of the control mea-
surement and the characteristics of the standard on which the control
measurement was carried out. The test value is the result of the ratio
of
difference
to
uncertainty (k=2)
.
E
1
: The measurement accuracy for the opened application file is
ok for this standard and cannot be further improved by this standard.
The difference between the mean value from the control measure-
ment and the nominal value (= reference value) of the standard used
for measurement cannot be distinguished from the measurement un-
certainty of the calibration
(measurement uncertainty (k=2)
).
E > 1
: The mean value of the control measurement has an excessive
deviation to the nominal value of the standard used for measure-
ment. Perform a corrective calibration to improve the measurement
accuracy for the opened application file.
x
m
:
Arithmetic mean value for the control measurement
x
r
:
Nominal value of the standard for which the control measurement was performed
U
m
:
Measurement uncertainty (k=2) of the control measurement based on stochastic errors
t:
Student factor (can be found in commonly available reference books e.g. "Formeln und
Tabellen der angewandten mathematischen Statistik" by Graf, Henning, Stange and Wil-
rich). For example, at a 68.27 % confidence level (k=1) and n = 10, the Student factor
is t
68.27; 9
= 1.07.
s:
Standard deviation of the mean value x
m
from the control measurement
n:
Number of control measurements on the standard
U
r
:
Specified measurement uncertainty (k=2) of the standard, direct entry value or, with spec-
ified tolerance level, the calculation takes place according to the formula Gl. 1
T:
Amount of the specified tolerance data of the standard
1.653: Factor for the confidence level of 95.45 % (k=2), resulting from the variance of the rec-
tangular distribution. For the confidence level of 68.27 % (k=1), the factor is 1.
Three-point calibration
Corrective calibration (one-point or two-point
True value
Trueness (Accuracy of the mean)
Trueness (Accuracy of the mean)
Agreement between the true value and the mean value of a measure-
Test value E
x
m
x
r
–
U
m
k=2
2
U
r
k=2
2
+
----------------------------------------------------------------------
=
U
m
k=2
2 t 68.27 %, n - 1
s x
m
n
-------------
=
U
r
k=2
1.653 T
3
-------
=
(Gl. 1) or entry value for U(k=2)
