Mismatch - Agilent Technologies E4418B Service Manual

A normal distribution is assumed, as the 3458A Manual has not specified the type of
distribution used on the measurement.
Both V
the output of the 432A using a 3458A DMM. The approximate values of V
V
scale.
For the 3458A DMM, the specified accuracy for the 10 volt scale is:
8ppm of Reading + 0.5ppm of Range
with;
0.15ppm of Reading + 0.01ppm of Range per °C (temp coefficient Tcal ±5 °C)
± 8.75 ppm of Reading + 0.55ppm of Range
Therefore,
(
U V
comp
For V0 and V1, two measurements are taken, so the uncertainty is equated to the RSS
of using two DMMs;

Mismatch

The Mismatch uncertainty was previously determined as being:
Note
Agilent E4416A/E4417A Service Guide
Measurement Uncertainty Analysis – Power Reference Level Test
and V values are calculated by subtracting V
0 1
for no power (V ) and for 1mW power (V
ref 0
) ( ) ±
U V
= =
ref
Voltage measurement
U(Vcomp)
U(V )
0
U(V )
1
MsUncertainty magnitude
This is the worst-case uncertainty for mismatch and occurs when the
incident and reflected waves are 180 degrees out of phase.
) are 5V with the DMM on the 10V
1
× ×
8.75 5 0.55 10
---------------------- - + ----------------------- -
1000000 1000000
49.25 µV
69.65 µV
69.65 µV
( )
2P s P d
=
Measurement Introduction
from V as measured at
ref comp
comp
±
49.25uV
=
Uncertainty
and
B-5