Operation
3-24
Figure 3-11
Eliminating ground loops
Experiment
(source)
E
S
R
E
IN
HI
Preamplifier
LO
Z
CM
I
Single
System
Ground
Ground bus
V
G
Input voltage to the preamplifier is:
E
IN
= E
S
+ I R
Resistance of input LO connection
(typically around 100m
Ω
)
Current passing through Z
CM
(M
Ω
or
G
Ω
) due to V
G
and currents in the
source (magnitude is typically
hundreds of nA’s).
Source voltage (desired signal)
E
IN
≈
E
S
, since I R is now insignificant compared to E
S
.