Model 2651A High Power System SourceMeter® Instrument Reference Manual
Section 4: Theory of operation
2651A-901-01 Rev. A / March 2011
4-19
Figure 81: Comparison of unguarded and guarded measurements
Insulator
I
D
DUT
Metal Mounting Plate
I
L
R
L1
R
L2
Insulator
I
M
= I
D
+ I
L
I
M
= Measured current
I
D
= DUT current
I
L
= Leakage current
IN/OUT
HI
IN/OUT
LO
A: Unguarded
I
D
DUT
Metal Mounting Plate
R
L1
Insulator
I
M
= I
D
IN/OUT
HI
IN/OUT
LO
x1
GUARD
0V
SourceMeter
SourceMeter
B: Guarded
Connect to earth safety ground
using #18 AWG wire or larger.
Cable Shield
Safety Shield
I-meter
A
I-meter
A
V-source
+
-
V-source
+
-