Model 6485 Picoammeter Instruction Manual Applications Guide I-11
As shown in Figure I-8, this will cause a current (i) to flow through the low to ground
capacitance of the picoammeter (A). Picoammeter HI is connected to the highest resis-
tance side of the circuit being measured, the “R” side of this current source. This circuit is
connected properly, so this current does not flow through the picoammeter and, therefore,
does not cause any measurement errors.
Figure I-8
Proper connection
However, when the HI of the picoammeter is connected to the low impedance power sup-
ply, this AC current (i) flows through the picoammeter (A) as illustrated in Figure I-9. This
current may affect the measurement accuracy, especially at low signal levels.
Current Source
6485
Picoammeter
+
-
i
HI
LO
R
A
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