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Model 2790 SourceMeter
Shielding
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Proper shielding of all signal paths and sources being measured is important to minimize
noise pickup in virtually any low-level measurement situation. Otherwise, interference
from such noise sources as line frequency and RF fields can seriously corrupt measure-
ments, rendering experimental data virtually useless.
In order to minimize noise, a closed metal shield surrounding the source may be necessary
(Figure
noise performance may result with the shield connected to chassis ground in some situa-
tions.
Figure D-4
Shielding example
2790
WARNING
®
Switch System Reference Manual
Do not float input LO more than 30V rms, 42.4V peak above earth
ground with an exposed shield connected to input LO. To avoid a pos-
sible shock hazard, surround the LO shield with a second safety shield
that is insulated from the inner shield. Connect this safety shield to
safety earth ground using #18 AWG minimum wire before use.
D-4). This shield should be connected to input LO in most cases, although better
A
HI
LO
Connect noise
shield to LO.
Safety shield required when
floating noise shield >30V rms
above chassis ground.
Noise
Shield
DUT
Safety
Shield
Connect safety shield to a
known safety earth ground using
#18 AWG wire or larger.
D-9
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