Performance Tests 2
Keysight E4416A/E4417A Power Meters Service Guide 47
Power Reference Level Test
Description
This test verifies the power level accuracy of the internal 50 MHz oscillator-also
called the power reference oscillator. The power reference oscillator output is
factory adjusted to 1 mW ±0.4%. This accuracy includes a performance limit of
0.1% and a system measurement uncertainty figure of 0.3% (traceable to the
National Physical Laboratory (NPL), UK). Refer to Appendix C for the
measurement uncertainty of the system.
If an equivalent measurement system is employed for post-factory test (with
ambient temperature of 23 ±3 °C), the power reference oscillator output can again
be set to 1 mW ±0.4%. This setting is sufficient to ensure that the power reference
oscillator meets the accuracy specification of ±0.5% after 2 years. This
specification includes the ±0.4% setting and also takes into account other factors
that will contribute to determining the accuracy after 2 years. The complete
breakdown of the ±0.5% specification is as follows:
Electrical Characteristics Performance Limits (maximum) Conditions
Power reference 1 mW Internal 50 MHz oscillator factory set to
±0.4% traceable to National Physical
Laboratory (NPL), UK.
Power reference accuracy setting ±0.1% Guardbanded Test Line Limits.
Power reference accuracy after
2 years
±0.9% (0 to 55 ºC) Worst case power meter accuracy, taking
into account the possibility of oscillator
drift and operation at 55 º.
The setting of the oscillator output accuracy is determined from the system
measurement uncertainty plus any chosen test line limit.
For example, if a test line limit of 1 mW ±0.2% was chosen while maintaining a
system measurement uncertainty of ±0.3%, the overall accuracy of the test
setup for the 1 mW power output becomes 0.3% + 0.2%, giving a setting
accuracy of 0.5%.
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