D
Measurement Uncertainty Analysis - Instrument Accuracy Test
D-152
E4416A/E4417A Power Meters Service Guide
Hence: Measurement Accuracy = f(MV , TSE)
The Measurement Uncertainty is not calculated from different sensor and
power meter combinations, rather it is taken care of in the Customer Limit
specification setting. Hence using the same power meter and making
measurements a number of times will give us the uncertainty of the test
station, without the uncertainty associated with the meter itself. By taking n
samples of the same meter/DUT in effect we are averaging out the error
associated with the DUT's measurement capability leaving us with a raw test
station uncertainty which is made up from TSE and the DMM error, for
example, the Measured Voltage (MV).
The method that is used to calculate the Measurement Uncertainty of our test
station is a combination of Type A and Type B analysis in line with the ISO
Expression of Measurement Uncertainty Guide.
Uncertainty Equation
TSE
The Measurement Uncertainty of the Measurement Accuracy is calculated
from testing the same DUT at 5dB step power level from
−
25 dBm to +20 dBm.
N O T E
Test Station Error (TSE) is the error contribution of the cables, connectors, noise, and
so forth, that cannot be measured independently.
N O T E
The measurement uncertainty only relates to the test station, in this case, a power
meter is the most accurate method of measuring power. Hence the reason the DUT
Measure component can be ignored in the measurement equation. However, taking a
number of measurements of the test system with the same power meter, averages out
the error resolution or minimize it to the extent where the magnitude error is many
times smaller than the station error.
u
2
MA
(
)
C
TSE
u TSE
(
)
⋅
[
]
2
C
MV
u MV
(
)
⋅
[
]
2
+
=
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