6482-901-01 Rev. A / August 2012
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3-3
Model 6482 Dual-Channel Picoammeter / Voltage Source Reference Manual
Section 3: Basic Operation
Basic circuit configuration
The fundamental circuit configuration for the Model 6482 is shown in
. Note that the
instrument has two separate channels (one channel shown), each of which includes a feedback
ammeter and a 0 ±10 V or 0 ±30 V voltage bias source.
also shows the output enable
circuit, which is shown enabled (see
), and the ground connect relay (see
). Note that the device under test (DUT) is connected between the triaxial INPUT
jack and the SOURCE OUTPUT terminal.
Figure 3-1
Basic circuit configuration
Operation considerations
The following paragraphs discuss warm-up period, autozero, and source delay.
Warm-up
The Model 6482 must be turned on and allowed to warm up for at least one hour to achieve rated
accuracies. For the latest specifications, visit the Keithley Instruments website
(http://www.keithley.com).
Autozero
Every analog-to-digital conversion (current reading) is calculated from a series of zero, reference,
and signal measurements. With autozero enabled, all three of these measurements are performed
for each reading to achieve rated accuracy. With autozero disabled, zero and reference are not
measured. Disabling autozero increases measurement speed, but zero drift will eventually
degrade accuracy. With autozero disabled, periodically change measurement speed.
Temperature changes across components within the instrument can cause the reference and zero
values for the analog-to-digital converter to drift due to thermo-electric effects. Autozero acts to
negate the effects of drift in order to maintain measurement accuracy over time. Without autozero
enabled, current measurements can drift and become erroneous.
NOTE
Autozero control affects both channels simultaneously.
-
+
HI
LO
Output
on
R
F
To analog-to-digital
converter
Floating channel 1
or channel 2
common
Feedback
ammeter
Bias source
0 to ±10 V or
0 to ±30 V
20 mA (maximum)
VOLTAGE
SOURCE
OUT
Note: One channel shown.
Other channel is identical.
Chassis
ground
Ground
connect
disabled
DUT
Chassis
ground
Triaxial
INPUT
20 mA
(maximum)
Current flow (I)
Summary of Contents for 6482
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