Fisher FERITSCOPE FMP30 - Page 231

Page 226 Operator‘s Manual FERITSCOPE
®
FMP30
Glossary
certainty takes the measurement uncertainty (U
m
) of the control measurement
and the specified measurement uncertainty (U
r
) of the standard (= reference
part) into account for a confidence level of 95.45 %, corresponding to the
extension factor k=2. The calculations are made according to ISO/IEC
Guide 98-3.
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.
Unit of measurement
Unit for displaying measurement data. In -ferrite content measurement,
the common units of measurement are ferrite numbers (FN) or ferrite per-
cent (Fe%).
USL
Upper specification limit. Specification limits (LSL and USL)
Variable features Features
Variance
Mean squared deviation. The square root of the variance is called stan-
dard deviation.
X
Countrate Countrate
X
Base
Zero point of the calibration curve. Countrate obtained when measure-
ments are taken on the Base of the calibration standard set.
Uncertainty (k=2) = (U
m
(k=2))² + (U
r
(k=2))²
U
m
k=22 t 68.27 %, n - 1
sx
m

n
-------------=
U
r
k=21.653
T
3
-------=
(Gl. 1) or entry value for U(k=2)