Agilent Technologies N4413A, User Manual

Page: 50 / 234

Using the Multiport Test System
How to Calibrate
Chapter 3 40
How to Calibrate
Calibration is required for accurate measurements. Even though calibration does take a few
minutes to complete, it saves time and money compared to costs associated with erroneous
measurement data. Even mechanical (non-electronic) calibration is reasonably quick once you
become familiar with the process.
TIP Understanding How Changes Affect Measurements
No two measurements and environmental conditions are exactly the same. The
best way to understand your conditions is to experiment and see how your test
equipment behaves over a period of time. A good way of doing this is to measure
the same device (i.e., a known standard) hourly throughout the day. Save or
print the measurement results of each measurement. Compare these results to
gain an understanding of how the ambient environment and drift affect the
measurements. Watch for trends with regard to the device meeting
specifications or measuring within guard band limits.
Triggers to Calibrate
We recommend that you perform a calibration on your multiport test system when the
following conditions occur:
• When connectors are cleaned, repaired, or replaced.
• If test cables have any changes, such as:
— When a test cable is replaced.
— When any connection is changed except the connections to the DUT.
— When test cables are flexed excessively (kinked or unkinked).
• If the frequency range is changed beyond the limits of the previous calibration.
• If the number of measurement points is increased to more than the number of points of the
previous calibration.
• When ambient temperature changes more than ±3 °C.
• Any other ambient environmental changes of significance.
• Regularly by time because of drift, if none of the previous conditions apply.
— Check the calibration at least daily (twice daily is recommended). Refer to “A Method of
Checking Calibration” on page 41 .
— Recalibrate weekly.