1-5
1.8
Offset voltage and bias current
calibration
Before performing meter verification procedures (checking
accuracy of the volts, amps, coulombs, and ohms measure-
ment functions), the offset voltage and bias current calibra-
tion procedure should be performed, as described in the
following paragraphs.
1.8.1 Front panel offset calibration
To calibrate voltage offset and input bias current from the
front panel, proceed as follows:
1. Turn on the Model 6517A, and allow a one-hour warm-
up period before calibrating offsets.
2. From normal display, press the MENU key.
3. Select CAL, then press ENTER.
4. Choose OFFSET-ADJ, then press ENTER. The instru-
ment will prompt you as follows:
CONNECT TRIAX SHORT
Press ENTER to continue.
5. Connect the shorted triax cable (short red and black
clips) to the rear panel INPUT connector, then press
ENTER. The instrument will then perform voltage off-
set calibration, during which it will display the follow-
ing message:
Performing V offset calibration
6. The Model 6517A will then prompt you as follows:
CONNECT TRIAX CAP
Press ENTER to continue
7. Removing the triax short, and connect the triax shield-
ing (non-shorting) cap in its place.
8. Press ENTER. The Model 6517A will perform offset
current verification, during which it will display the fol-
lowing message:
Performing I offset calibration
9. Press EXIT as necessary to return to normal display
once both offset calibration procedures are completed.
1.8.2 IEEE-488 bus offset calibration
To calibrate voltage offset and input bias current using IEEE-
488 bus commands, proceed as follows:
1. Turn on the Model 6517A, and allow a one-hour warm-
up period before calibrating voltage and current offsets.
2. Connect the triax shorting cable to the rear panel INPUT
connector, then send the following command over the
IEEE-488 bus:
:CAL:UNPR:VOFF
Wait until the instrument completes this step before con-
tinuing.
3. Removing the triax shorting cable, and connect the triax
shielding (non-shorting) cap in its place.
4. Send the following command to the instrument over the
IEEE-488 bus:
:CAL:UNPR:IOFF
5. Wait until the instrument completes bias current calibra-
tion, then remove the cap from the rear panel INPUT
connector.
1.9
Meter verification procedures
The following paragraphs contain procedures for verifying
instrument one-year accuracy specifications for the follow-
ing functions:
• DC volts
• DC amps
• Coulombs
• Ohms
NOTE
Ohms accuracy specifications are derived
from both amps and voltage source speci-
fications. Thus, it is not necessary to sepa-
rately verify the accuracy of the ohms
function. As long as the amps function and
voltage source meet their respective accu-
racy specifications, ohms function accu-
racy is assured.
If the Model 6517A meter functions are out of specifications
and not under warranty, refer to the calibration procedures in
Section 2.
WARNING
The maximum INPUT level (HI to LO)
is 250V peak. The maximum common-
mode voltage is 500V peak.
Exceeding these values may cause dam-
age to the unit.
Some of the procedures in this section
may expose you to hazardous voltages.
Use standard safety precautions when
such hazardous voltages are encoun-
tered to avoid personal injury caused by
electric shock.