Model 6220/6221 Reference Manual
Output Connections
2-13
Return to
Cable Guard (which has less noise than banana jack Guard) can also be used to
measure voltage as previously described. For best accuracy, it is recommended
that banana jack Guard be used.
Figure 2-9
Using banana jack Guard to measure voltage
Floating the current source
Using an external source in the test system may require that the Model 622x
current source float off Earth Ground. An example of such a test system is shown
in
, which includes an external voltage source. Notice that Output Low
of the voltage source is connected to earth ground.
NOTE
For the Keithley Model 2182/2182A Nanovoltmeter, the
input impedance for the 100V range is 10M
Ω
. Therefore,
for higher impedance DUT, voltage should be measured
at banana jack Guard or Cable Guard.
10M
W
DUT
10µA
I-source
High
Low
622x
10M
W
R
IN
V
5µA
5µA
Low-Impedance Voltmeter
+50V
x1
10M
W
DUT
10µA
I-source
High
Low
622x
10M
W
Rin
V
10µA
Low-Impedance Voltmeter
+100V ±1mV
Banana
Jack Guard
A) 50% measure error due to voltmeter loading
B) Using banana jack Guard to measure voltage
V
DUT
= I x R
= 5µA x 10M
W
= 50V
V
DUT
= I x R
= 10µA x 10M
W
= 100V
V
GUARD
= V
DUT
±1mV
= 100V ±1mV
V
GUARD
Loading Error =
V
R
IN
= I x R
= 5µA x 10M
W
= 50V
V
R
IN
V
R
IN
+ V
DUT
= 50%
= 50V / 100V
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Summary of Contents for 6220
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