128 Keysight B2980B User’s Guide, Edition 1
How to Perform Measurement
Measurement Considerations
External Noise
Power line noise is one of the major sources that can negatively affect low current
measurements. Usually, noise current comes from capacitor. Even if it has low
capacitance, it causes large noise. So, it is desirable to eradicate the capacitive
coupling. Shielding can be a countermeasure for the external noise.
Dielectric Absorption
Change of electric field applied to an insulation material causes the leakage
current which needs long convergence time. This is the phenomenon called as the
dielectric absorption. The level of current and the length of convergence time
depend on the type of insulation material and the amount of electric field change.
This undesirable phenomenon can be alleviated by selecting the insulation
material of low dielectric absorption and by using the guard technique effective for
reducing the electric field change. Current compensation is difficult because the
current level changes along with the passage of time. So it is important to wait
enough time until the current converges.
Ammeter
Voltage
source
Insulation
material
Noise current caused by
dielectric absorption
Time
Time
Voltage Current
A
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