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Why Calibration Is
Essential
When to Repeat the
Calibration
Checking the
Calibration
Operation
Measurement Calibration
Measurement Calibration
During measurement calibration, a standard device with known
characteristics is measured, and the results of the measurement are used to
create a set of error coefficients. During subsequent measurements, the
network analyzer uses the error coefficients to correct for its own
measurement errors.
The accuracy of the network analyzer is very much dependent on this
error-correction technique; therefore, the analyzer must be calibrated before
it is used to make measurements.
The 8510XF is designed for exceptional stability; after it has been
calibrated, the specified measurement accuracy of the system is guaranteed,
provided that the conditions of measurement remain the same. However,
certain changes to the measurement conditions may invalidate the
calibration, as described below.
•
A calibration is only valid for the frequency range over which it was
performed; if the frequency range has changed, the calibration must be
repeated.
•
A calibration is only valid for the number of points over which it was
performed; if the number of points has been increased, the calibration
must be repeated.
•
If test port cables have been kinked, replaced, or disconnected and
reconnected, the calibration may be invalid, and should be checked.
•
If connectors have been degraded by wear, the calibration may be
invalid, and should be checked.
•
If the ambient temperature changes by ±1 °C or more, the calibration
may be invalid, and should be checked.
A common practice for making a rough check of a calibration is to
remeasure one of the devices used in the calibration procedure (or
verification procedure). For example, if you reconnect a short that was used
during calibration, it should appear as a near-perfect short, across the
frequency range of calibration.
3-6 8510XF Network Analyzer Systems
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