Combined Standard Uncertainty (Uc(Y - Agilent Technologies E4416A Service Manual

C Measurement Uncertainty Analysis - Power Reference Level Test

Combined Standard Uncertainty (uc(y))

Table C-2 Combined Standard Uncertainty
Symbol Source of Uncertainty
U(V ) Two Voltage measurements
0
on a
3458A DMM
U(V ) Two Voltage measurements
1
on a
3458A DMM
U(V ) Voltage measurement on
comp
3458A DMM
U(R) 4 wire Resistance
measurement on
3458A DMM
U(CF) Calibration factor for
Thermistor
U(M ) Mismatch between the
s
DUT and the Thermistor
U(Drift) Drift of 8478B Thermistor
U(Rep) Repeatability of the
complete measurement
U(c) Combined Uncertainty
*
U Expanded Uncertainty
* Using Agilent's standard 95.5% confidence the coverage factor is k = 2.00
Expanded Uncertainty
The expanded uncertainty is: U= 3.030 mW, as a percent of 1.000 mW: U =
0.303%
C-148
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Value Probability Divisor
Distribution
69.65 μW
Normal 2
69.45 μW
Normal 2
49.25 μW
Normal 2
0.0046 Ω
Normal 2
0.002 Normal 2
0.0012 U shaped
0.0006 Normal 2
0.057 μW
Normal 1
Normal
k = 2 Normal
E4416A/E4417A Power Meters Service Guide
Ci Ui/μW
-04
2.129x10 V/Ω 0.007
-02
1.224x10 V/Ω 0.426
-02
− 1.245x10
V/Ω 0.307
-06
− 4.727x10
V/Ω 0.012
-04
− 9.696x10
V/Ω 1.070
-04
− 9.454x10
2
V/Ω 0.885
-03
1.00x10 V/Ω 0.6
1 0.057
1.515
3.030