User`s guide

Measurement Tutorial 3
U2741A User’s Guide 51
Figure 3-2 Ground loop induced error
The best way to eliminate ground loops is to isolate the
digital multimeter from earth by not grounding the input
terminals. If the digital multimeter must be earth- referenced,
connect it and the device under test to the same common
ground point. Also connect the digital multimeter and device
under test to the same electrical outlet whenever possible.
R
L
= Lead Resistance
R
i
= digital multimeter Isolation
V
ground
= Voltage Drop or Ground Bus
R
L
R
i
> 10GΩ
V
ground
R
L
V
test
LO
HI
Meter
Ideal
Resistance
User's Guide.book Page 51 Friday, August 8, 2008 9:11 AM