10-3
Determining System Measurement Uncertainties
Sources of Measurement Errors
Sources of Measurement Errors
Measurement errors are made up of systematic errors, random errors, and drift errors.
Each of these measurement error types is discussed in this section.
Sources of Systematic Errors
The residual (after measurement calibration) systematic errors result from imperfections
in the calibration standards. All measurements are affected by dynamic accuracy. For
reflection measurements, the associated residual errors are residual directivity, residual
source match, residual load match, and residual reflection tracking. For transmission
measurements, the additional residual errors are residual crosstalk, residual source
match, residual load match, and residual transmission tracking.
The listing below shows the abbreviations used for residual systematic errors that are in
the uncertainty equations.
• E
DF
= forward residual directivity
• E
SF
= forward residual source match
• E
RF
= forward residual reflection tracking
• E
XF
= forward crosstalk
• E
LF
= forward load match
• E
TF
= forward transmission tracking
• E
DR
= reverse residual directivity
• E
SR
= reverse residual source match
• E
RR
= reverse residual reflection tracking
• E
XR
= reverse crosstalk
• E
LR
= reverse load match
• E
TR
= reverse transmission tracking
• A
M
= magnitude dynamic accuracy
• A
P
= phase dynamic accuracy
Dynamic accuracy includes errors during internal self-calibration routines, gain
compression in the microwave frequency converter (sampler) at high signal levels, errors
generated in the synchronous detectors, localized non-linearities in the IF filter system,
and from LO leakage into the IF signal paths.
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