Considering Noise Reduction - Keysight B2980B Series User Manual

Function Details
Setup Integrity Checker

Considering Noise Reduction

The noise checking in a better measurement environment results in a smaller
Variance Ratio value. To make the Variance Ratio smaller, improve your
measurement environment or change the measurement condition. For example,
changing the measurement cable, suppressing the external noise, considering the
surrounding environment such as vibration, changing the aperture time and filter.
The effect by the countermeasure can be evaluated by the change of noise level or
variance ratio.
If the measurement cable (Triaxial Cable) has the problem in the example of Figure
5-16, a large noise or variance ratio should be measured when connecting only
the measurement cable. In that case, changing the measurement cable,
confirming the connectors, preventing the vibration on the measurement cable, or
suppressing the external noise may solve the problem.
Or, you can confirm the shielding effect of the test fixture by measuring the noise
level with connecting the test fixture. If the noise level or variance ratio does not
reduce, the measurement cable or the shielding itself has the problem.
It is recommended to prepare several kinds and lengths of stable and shielded
measurement cables that have been measured beforehand. The previously
measured data is helpful to evaluate the measurement results of noise checking.
Keysight B2980B User's Guide, Edition 1 251