Keithley 2651A Reference Manual page 76

Section 2: General operation
Noise shield
A noise shield (see following figure) is used to prevent unwanted signals from being induced into the
test circuit. Low-level signals may benefit from effective shielding. The metal noise shield surrounds
the test circuit and should be connected to SMU LO as shown.
Safety shield
A safety shield must be used whenever hazardous voltages (>30 V RMS, 42 V peak) will be
present in the test circuit. To prevent electrical shock that could cause injury or death, NEVER
use the Model 2651A in a test circuit that may contain hazardous voltages without a properly
installed and configured safety shield.
2-54
Model 2651A High Power System SourceMeter® Instrument Reference Manual
Figure 19: High-impedance guarding
SENSE/GUARD
S S
LO G G G G HI
LO
LO
>
Figure 20: Noise shield
SENSE/GUARD
S S
LO G G G G HI
Noise shield
connected to
In/Out LO
OUTPUT
LO HI
40V, 50A MAX.
HI
G
Guard shield
The guard shield can be the shield of
a coaxial cable, or it can be an insulated
foil that surrounds the conductor.
DUT
HI
1 GΩ
Metal guard shield
OUTPUT
LO HI
40V, 50A MAX.
LO HI
DUT
LO HI
>1 GΩ
WARNING
Noise Shield
2651A-901-01 Rev. A / March 2011