Keysight Technologies 85058B, User'S And Service Manual

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85058B/E 1-21
General Information
When to Calibrate
When to Calibrate
A network analyzer calibration remains valid as long as the changes in the systematic error are
insignificant. This means that changes to the uncorrected leakages (directivity and isolation),
mismatches (source match and load match), and frequency response of the system are small
(<10%) relative to accuracy specifications.
Change in the environment (especially temperature) between calibration and measurement is
the major cause in calibration accuracy degradation. The major effect is a change in the
physical length of external and internal cables. Other important causes are dirty and damaged
test port connectors and calibration standards. If the connectors become dirty or damaged,
measurement repeatability and accuracy is affected. Fortunately, it is relatively easy to
evaluate the general validity of the calibration. To test repeatability, remeasure one of the
calibration standards. If you can not obtain repeatable measurements from your calibration
standards, maintenance needs to be performed on the test port connectors, cables and
calibration standards. Also, maintain at least one sample of the device under test or some
known device as your reference device. A verification kit may be used for this purpose. After
calibration, measure the reference device and note its responses. Periodically remeasure the
device and note any changes in its corrected response which can be attributed to the test
system. With experience you will be able to see changes in the reference responses that
indicate a need to perform the measurement calibration again.