Keithley 6220, Reference Manual

Page: 68 / 454

2-14 Output Connections Model 6220/6221 Reference Manual
Return to Section 2 topics
For the test circuit shown in Figure 2-10 , the Model 622x current source must be
configured to float off Earth Ground. As shown, Output Low of the Model 622x is
fl10V above Earth Ground. If Output Low of the Model 622x was instead
connected to Earth Ground, the voltage source would be shorted through Earth
Ground.
In order to float the current source, Output Low must be disconnected from Earth
Ground. The floating configurations are shown in
Figure 2-4 B and Figure 2-5 B.
See “Triax output low,” on page 2-7 for details on selecting the floating
configuration.
WARNING When floating the Model 622x, an electric shock hazard may
exist between Output Low of the Model 622x and Chassis:
• The chassis of the Model 622x must be connected to Earth
Ground. Use the chassis ground screw on the rear panel for
connection to a known safety Earth Ground.
• The test circuit must be surrounded by a safety shield that is
connected to a safety Earth Ground (see “Safety shield con-
nections,” on page 2-16 ).
Figure 2-10
Floating the Model 622x current source
1mA
I-source
High
Low
622x
10V
Source
+10V
Earth Ground
Chassis
NOTE Earth Ground and Chassis are essentially at the same
ground potential. The difference between these two
ground points is shown in Figure 2-1.
Low
Output Low connected
to Earth Ground
Output Low
NOT connected
to Earth Ground
(floating)
High
+
Chassis
Chassis
622x chassis screw
connected to safety
Earth Ground
V-source chassis connected to Earth
Ground through the power cord
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