When GROUND MODE is set to ON, the GPT-
10000 grounds the return terminal to the 
ground. This mode is best for DUTs that are 
grounded to an earth ground by their chassis, 
fixtures or operation environment. This mode 
measures the potential of the HIGH VOLTAGE 
terminal with respect to earth ground. This 
means that additional noise which leaks to 
earth ground will also be measured. This is the 
safest testing mode, though potentially not as 
accurate. 
When GROUND MODE is set to OFF, the 
return terminal is floating with respect to the 
earth ground. This mode is for DUTs that are 
floating and not directly connected to an earth 
ground. This is more accurate than when 
GROUND MODE is set to ON as less noise will 
be measured. For this reason, this testing mode 
is able to measure with better stability.