Fluke Digital Multimeter - Page 32

©Fluke Calibration 2011 Basics Of Measurement Uncertainty for DMM Calibration 32
Measurement
Value
Deviation from
Average
x
1
10.07
+0.03
x
2
10.02
-0.02
x
3
10.01
-0.03
x
4
10.06
+0.02
x
5
10.04
0.00
Calculating the uncertainty due
to measurement repeatability
• The uncertainty is statistically
analyzed from the measurement
data series
u
1
– for a normally distributed
population, the best estimate of
uncertainty is the experimental
standard deviation of the mean
NOTE: In the unusual case where
1. the calibrating standard is extremely accurate &
stable, and
2. the repeated test measurement values are
unchanged (or even with only a ± one digit
change)
Then this uncertainty can be considered as non
significant
• One measurement value would be sufficient
• The type B resolution uncertainty is adequate
Experimental
Standard
Deviation
Experimental
Standard Deviation
of the Mean











1
)(
1
2
n
xx
n
i
i
s
n
s
u 1