Measurement Uncertainty Analysis - Power Reference Level Test C
E4416A/E4417A Power Meters Service Guide C-139
Uncertainty Equation
General form of uncertainty equation is:
Hence,
Assuming that there is no correlation exists between the 8 input variables.
Voltage Measurements Uncertainty
Since the manufacturer's data is used to determine the standard uncertainty,
the analysis used is the Type A method.
The 3458A DMM Uncertainty is calculated with reference to the Appendix A
of the 3458A Operating Manual.
A normal distribution is assumed, as the 3458A Manual has not specified the
type of distribution used on the measurement.
Both V
0
and V
1
values are calculated by subtracting V
ref
from V
comp
as
measured at the output of the 432A using a 3458A DMM. The approximate
values of V
comp
and V
ref
for no power (V
0
) and for 1 mW power (V
1
) are 5 V
with the DMM on the 10 V scale.
For the 3458A DMM, the specified accuracy for the 10 volt scale is:
8ppm of Reading + 0.5 ppm of Range
u
2
y() c
2
iu
2
x
i
() 2 c
i
c
j
ux
i
x
j
,()
ji1+=
N
∑
i 1=
N
∑
⎝⎠
⎜⎟
⎜⎟
⎛⎞
+
i 1=
N
∑
=
u
2
1mW()CV
0
uV
0
()⋅
2
– CV
0
uV
0
()⋅
2
CV
comp
uV
com p
()⋅
2
CR u R()⋅
2
…++ ++
CCF u CF()⋅
2
CM
s
uM
s
()⋅
2
C
Rep
uRep()⋅
2
C
Drift
uDrift()⋅
2
++ +
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