Keithley SourceMeter 3A 2420, Service Manual

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Calibration 2-3
Calibration considerations
When performing the calibration procedures:
• Make sure that the test equipment is properly warmed up and connected to the Model
2420 front panel INPUT/OUTPUT jacks. Also be certain that the front panel jacks are
selected with the TERMINALS switch.
• Always allow the source signal to settle before calibrating each point.
• Do not connect test equipment to the Model 2420 through a scanner or other switching
equipment.
• If an error occurs during calibration, the Model 2420 will generate an appropriate error
message. See Appendix B for more information.
WARNING The maximum common-mode voltage (voltage between LO and chassis
ground) is 250V peak. Exceeding this value may cause a breakdown in in-
sulation, creating a shock hazard.
CAUTION The maximum voltage between INPUT/OUTPUT HI and LO or 4-WIRE
SENSE HI and LO is 75V peak. The maximum voltage between INPUT/
OUTPUT HI and 4-WIRE SENSE HI or between INPUT/OUTPUT LO
and 4-WIRE SENSE LO is 5V. Exceeding these voltage values may result
in instrument damage.
Calibration cycle
Perform calibration at least once a year to ensure the unit meets or exceeds its specifications.
Recommended calibration equipment
Table 2-1 lists the recommended equipment for the calibration procedures. You can use al-
ternate equipment as long that equipment has specifications at least as good as those listed in the
table. For optimum calibration accuracy, test equipment specifications should be at least four
times better than corresponding Model 2420 specifications.