Anritsu S251B - Manual (Page 13)

Calibration
The Site Master is a field portable unit operating in the rigors of the test environment. An
Open-Short-Load (OSL) or Open-Short-Load-Through (OSLT) calibration should be per-
formed prior to making a measurement in the field. A built-in temperature sensor in the Site
Master advises the user, via an icon located on the right side of the LCD screen, that the in-
ternal temperature has exceeded a safety window, and the user is advised to perform an-
other OSL or OSLT calibration in order to maintain the integrity of the measurement.
NOTES:
For best calibration results—compensation for all measurement uncertain-
ties—ensure that the Open/ Short/Load is at the end of the test port or optional
extension cable; that is, at the same point that you will connect the antenna or
device to be tested.
For best results, use a phase stable Test Port Extension Cable (see Optional
Accessories). If you use a typical laboratory cable to extend the Site Master test
port to the device under test, cable bending subsequent to the OSL or OSLT
calibration will cause uncompensated phase reflections inside the cable. Thus,
cables which are NOT phase stable may cause measurement errors that are
more pronounced as the test frequency increases.
For optimum calibration, Anritsu recommends using precision calibration components.
Annual Verification
Anritsu recommends an annual calibration and performance verification of the Site Master
and the OSL calibration components by local Anritsu service centers. Anritsu service cen-
ters are listed in Table 1-2 on the following page.
The Site Master itself is self-calibrating, meaning that there are no field-adjustable compo-
nents. However, the OSL calibration components are crucial to the integrity of the calibra-
tion and therefore, must be verified periodically to ensure performance conformity. This is
especially important is the OSL calibration components have been accidentally dropped or
over-torqued.
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Chapter 1 General Information