Error Terms Can Also Serve A Diagnostic Purpose - Agilent Technologies 8719ET Service Manual

8719ET/20ET/22ET
8719ES/20ES/22ES
RF Network Analyzers

Error Terms Can Also Serve a Diagnostic Purpose

Specific parts of the analyzer and its accessories directly contribute to the magnitude and
shape of the error terms. Since we know this correlation and we know what typical error
terms look like, we can examine error terms to monitor system performance (preventive
maintenance) or to identify faulty components in the system (troubleshooting).
• Preventive Maintenance: A stable, repeatable system should generate repeatable
error terms over long time intervals, for example, six months. If you print or plot the
error terms, you can periodically compare current error terms with the record. A sudden
shift in error terms reflects a sudden shift in systematic errors, and may indicate the
need for troubleshooting. A long-term trend often reflects drift, connector and cable
wear, or gradual degradation, indicating the need for further investigation and
preventive maintenance. Yet, the system may still conform to specifications. The cure is
often as simple as cleaning and gaging connectors or inspecting cables.
• Troubleshooting: If a subtle failure or mild performance problem is suspected, the
magnitude of the error terms should be compared against values generated previously
with the same instrument and calibration kit. This comparison will produce the most
precise view of the problem.
However, if previously generated values are not available, compare the current values
to the typical values listed in
plots in "Error Term Descriptions" on page
inspect the corresponding system component. If the condition causes system verification
to fail, replace the component.
Consider the following while troubleshooting:
All parts of the system, including cables and calibration devices, can contribute to
systematic errors and impact the error terms.
Connectors must be clean, gaged, and within specification for error term analysis to
be meaningful.
Avoid unnecessary bending and flexing of the cables following measurement
calibration, minimizing cable instability errors.
Use good connection technique during measurement and calibration. The connector
interface must be repeatable. For information on connection technique and on
cleaning and gauging connectors, refer to
on page 1-6.
Use error term analysis to troubleshoot minor, subtle performance problems. Refer to
Chapter 4 , "Start Troubleshooting Here,"
error is evident.
It is often worthwhile to perform the procedure twice (using two distinct
measurement calibrations) to establish the degree of repeatability. If the results do
not seem repeatable, check all connectors and cables.
Service Guide
Error Terms Can Also Serve a Diagnostic Purpose
Table 11-3 and Table
11-10. If the magnitude exceeds its limit,
"Principles of Microwave Connector Care"
if a blatant failure or gross measurement
11-4, and shown graphically on the
Error Terms
11- 3