APPLICATIONS
5.4 CALIBRATING OTHER PICOAMMETERW
ELECTROMETERS
In general, calibrating other instruments with the Model
263 is a simple matter of sourcing the appropriate para-
meter to the meter and performing the calibration adjust-
ment. However, a technique to reduce AMPS offset on
the 200pA, 20pA, and 2pA ranges should be routinely
used when optimum source accuracy is required. The off-
set generated by these ranges are listed with the accuracy
specifications of the Model 263.
With the Model 263 connected to an electrometer or
picoammeter, perform the following steps to reduce
Model 263 offset on the 200pA, ZOpA, and 2pA AMPS
ranges:
1. While in standby, program the Model 263 for the de-
sired output.
2. Place the meter in zero check and select the optimum
range for the programmed output. If the meter has a
zero correct feature, use it to zero the display.
3. Set the Model 263 for zero by pressing ZERO, and
source zero to the meter by pressing OPERATE.
4. Release zero check on the meter. The displayed reading
on the meter is offset.
5. Using the appropriate control (ZERO, SUPPRESS, etc.),
zero the display of the meter to cancel the source offset.
6. The programmed output level of the Model 263 can now
be sourced to the meter by again pressing ZERO.
The above procedure only needs to be performed if the
Referring to the calibration procedure found in the Model
specified
offset of the Model 263 is high enough to ad-
619 Instruction Manual, use the Model 263 as follows:
versely affect the specified accuracy of the meter reading.
The following paragraphs summarize how the Model 263
can be used to calibrate the Keithley Models 480,619,614,
642, 61OC, 602, and 616.
5.4.1 Model 480 Picoammeter Calibration
The Model 263 simplifies the Model 480 calibration pro-
cedure by eliminating the need for precision resistors and
a DCV calibrator to form a current source. Referring to
the calibration procedure found in the Model 480 Instruc-
tion Manual, use the Model 263 as follows:
1. Gain Adjustement (step e)--In this step a precision
resistor and a DC calibrator are used to source current.
Instead, simply use the Model 263 as a current source
(19O.OOOj4A and 19.0000+4) to the lOOpA and 10~A
ranges of the Model 480.
2. 1OnA Range Adjustment (step f)-Again, in this step
a precision resisitor and a DC calibrator are used to
source current. Instead, use the Model 263 to source
19.00001~4 to the 1OnA range of the Model 480.
To connect the Model 263 to the Model 480, refer to Figure
5-7.
5.4.2 Model 819 Electrometer Calibration
MODEL 480
TRIAXTO BNC ADAPTER
MODEL 263
(KEITHLEY MODEL4804)
-!
Figure 5-7. Model 480 Calibration
5-14
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