Keithley 2750, Service Manual

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2-2 Calibration Model 2750 Multimeter/Switch System Service Manual
Introduction
Use the procedures in this section to calibrate the Model 2750. Calibration procedures
include:
• Comprehensive calibration: Usually the only calibration required in the field.
• Manufacturing calibration: Usually only performed at the factory (unless the unit
has been repaired).
• Model 7700 calibration: Covers calibration procedures specific to Model 7700
cards.
WARNING The information in this section is intended only for qualified service per-
sonnel. Do not attempt these procedures unless you are qualified to do so.
All the procedures require accurate calibration equipment to supply precise DC and AC
voltages, DC and AC currents, and resistance values. Comprehensive calibration can be
performed any time by an operator either from the front panel, or by using the SCPI com-
mands sent either over the IEEE-488 bus or the RS-232 port. DC-only and AC-only cali-
bration may be performed individually, if desired.
Environmental conditions
Conduct the calibration procedures in a location that has:
• An ambient temperature of 18° to 28°C (65° to 82°F).
• A relative humidity of less than 80% unless otherwise noted.
Warmup period
Allow the Model 2750 Multimeter/Switch System to warm up for at least two hours
before performing calibration.
If the instrument has been subjected to temperature extremes (those outside the ranges
stated above) allow extra time for the instrument’s internal temperature to stabilize. Typi-
cally, allow one extra hour to stabilize a unit that is 10°C (18°F) outside the specified tem-
perature range.
Allow the test equipment to warm up for the minimum time specified by the manufacturer.
Line power
The Model 2750 requires a line voltage of 100V/120V/220V/240V, ±10% and a line fre-
quency of 45Hz to 66Hz or 360Hz to 440Hz. Note that the line frequency is automatically
sensed at power-up, but the line voltage must be manually set to either 100V/120V or
220V/240V as described in
Section 3 .