Measurement Uncertainty - Keysight N5221A Service Manual

PNA Series Microwave Network Analyzers Tests and Adjustments
N5221A/22A System Verification

Measurement Uncertainty

Measurement uncertainty is defined as the sum of:
• the residual systematic (repeatable) errors, and
• the random (non-repeatable) errors
in the measurement system after calibration.
The systematic errors are:
• directivity,
• source match,
• load match,
• reflection and transmission frequency tracking, and
• isolation (crosstalk).
The random errors include:
• noise,
• drift,
• connector repeatability, and
• test cable stability.
A complete description of system errors and how they affect measurements is provided in the analyzer's
on-line embedded help.
Any measurement result is the vector sum of the actual test device response plus all error terms. The
precise effect of each error term depends on its magnitude and phase relationship to the actual test device
response. When the phase of an error response is not known, phase is assumed to be worst-case (180 to
+180). Random errors such as noise and connector repeatability are generally combined in a
root-sum-of-the-squares (RSS) manner.
Service Guide N5222-90001 3-21