2-15
2.9
IEEE-488 bus calibration
2.9.1 Calibration commands
Refer to Section 3 or Appendix C for a complete listing of
calibration commands. Section 3 also provides a detailed
discussion of each command.
2.9.2 IEEE-488 bus comprehensive calibration
procedure
Follow the procedure outlined below to perform comprehen-
sive calibration over the IEEE-488 bus. The bus commands
and appropriate parameters are separately summarized for
each step.
Procedure
Step 1: Prepare the Model 6517A for Calibration
1. Connect the Model 6517A to the IEEE-488 bus of the
computer using a shielded IEEE-488 cable such as the
Keithley Model 7007.
2. Connect the calibration standard to the Model 6517A
DIGITAL I/O jack (see Figure 2-1).
NOTE
The calibration standard must be con-
nected to the DIGITAL I/O port in order to
operate properly. Do not connect any
equipment except the Model 5156 Elec-
trometer Calibration Standard to the
Model 6517A DIGITAL I/O port during
calibration. Digital signals present during
calibration may affect other equipment.
3. Turn on the power, and allow the Model 6517A to warm
up for at least one hour before performing calibration.
4. Unlock calibration by briefly pressing in on the recessed
front panel CAL switch, and verify that the following
message is displayed:
CALIBRATION UNLOCKED
Comprehensive cal can now be run
NOTE
You can query the instrument for the state
of the comprehensive CAL switch by
using the following query:
:CAL:PROT:SWIT?
A returned value of 1 indicates that cali-
bration is locked, while a returned value of
0 shows that calibration is unlocked.
5. Make sure the primary address of the Model 6517A is
the same as the address specified in the program you
will be using to send commands. (Use the MENU key
and the COMMUNICATION menu to access the
IEEE-488 address.)
Step 2: Offset Calibration
Perform the steps below to perform the various offset cali-
bration steps. Table 2-9 summarizes these steps.
1. Connect the shorted triax cable (connect red and black
clips) to the instrument INPUT jack.
2. Send the following command over the bus:
:CAL:UNPR:VOFF
Wait until the instrument completes this step before con-
tinuing. (See paragraph 3.9.)
3. Disconnect the triax shorting cap from the INPUT jack,
and connect the triax shielding (non-shorting) cap to the
INPUT jack in its place.
4. Send the following command to the instrument:
:CAL:UNPR:IOFF
Wait until the instrument completes this step before
continuing.
Step 3: Initiate Calibration
Send the following command over the bus to initiate
calibration:
:CAL:PROT:INIT
Table 2-9
Offset calibration steps
Step
Bus command
Connections*
Offset voltage
Bias current
:CAL:UNPR:VOFF
:CAL:UNPR:IOFF
Triax shorting cable
Triax shielding cap
* Connect indicated triax cap or cable to INPUT jack.