Environmental Conditions; Front Panel Calibration - Keithley 263 Instruction Manual

APPLICATIONS
NOTE: The following additional items will be neccesary
if calibration is to be performed over the IEEE-488 bus.
4. Keithley Model 4853 IEEE-488 Interface installed in the
Model 485.
5. HP 85 Computer equipped with HP 82937 Gl'IEi Inter-
face and I/O ROM.
6. Keithley Model 7008 IEEE cable.
5.2.3 Environmental Conditions
Calibration should be performed under laboratory condi-
tions having an ambient temperature of 23 * 1°C and a
relative humidity of less than 70%. With both the Model
485 and 263 on, allow them to warm up for one hour. If
either instrument has been subjected to extreme temper-
ature or humidity, allow at least one additional hour for
the instrument to stabilize before beginning the calibra-
tion procedure.
NOTE
Calibration can be stopped at any time and only
those ranges out of specification need be cali-
brated.
5.2.4 Front Panel Calibration
Perform the following steps to calibrate the Model 485
from the front panel:
1. On the Model 485, depress ZERO CHECK and select
the 21~4 range.
2. With an open input, adjust the ZERO pot for .OOOO * 1
count on the display.
NOTE
If Q104, U105, R113, R114 or R115 have been re-
placed, the picoammeter may not zero. See para-
graph 5.7 in the Model 485 Instruction Manual for
the procedure to balance the input amplifier.
3. Connect the output of the Model 263 Calibrator/Source
to the input of the Model 485 as shown in Figure 5-1.
Make sure the calibrator is in standby,
4. On the Model 485, press the REL and LOG push-
buttons simultaneously and hold in until the message
"CAL" is displayed. Release the buttons. The unit is
now in the calibration mode as indicated by the
"CAL" annunciator.
5. Release ZERO CHECK on the Model 485.
6. Program the Model 263 to output .OOOOO nA. Use the
AMPS (active) current source.
7. The Model 485 may be displaying a small offset (= 1
count). To cancel this offset, press REL on the Model
485 to zero the display.
8. Program the Model 263 to output 1.90000 nA.
9. Adjust the display of the Model 485 to read 1.9OOOnA
using the STOiCLR and RCL buttons. The STOiCLR
button increments the displayed reading and the RCL
button decrements the displayed reading.
10. Using Table 5-1 as a guide, repeat the basic procedure
outlined in steps 5 through 9 to calibrate the rest of
the current ranges of the Model 485.
11. To store calibration constants and exit the calibration
mode, simultaneously press the REL and LOG buttons
until the message "Star" is displayed. If instead the
message "out" is displayed, then calibration storage
was not enabled as explained in paragraph 5.2.1 and
calibration constants will only be valid until the Model
485 is turned off.
Table 5-l. Model 485 Range Calibration
485 Range
263 Output
current 485 Reading
2:?+
1.90000 IL4
1.9ooonA
19.0000 nA
19.000 IIA
200 IIA
190.000 I-LA 190.00 nA
2
PA 1.90000 fiA
1.9000 pA
20 PA 19.0000 PA
19.000 PA
200 PA
190.000 &A 190.00 PA
2mA 1.9000 InA
1.9ooomA
5-2