Performance Verification; Verification Test Requirements - Keithley 7708 User Manual

Performance verification
The performance of the Model 7708 card is tested by verifying measurement accuracy through the card. If verification limits
are met through the front panel terminals of the Model 27xx, they should also be met through the card.
WARNING The information in this section is intended only for qualified service personnel. Do not
attempt these procedures unless you are qualified to do so.
NOTES Measurement accuracy through the Model 7708 card should only be verified after instrument
accuracy has already been verified through the front panel terminals of the Model 27xx. The
procedures to verify accuracy from the front panel inputs are provided in the Model 2700 Service
Manual.
If the Model 7708 card is still under warranty and is the cause of measurement inaccuracy, contact
your Keithley representative or the factory to determine the correct course of action.
Model 7708 verification test procedures include:
• DC volts
• AC volts
• Resistance
• Temperature
• Frequency
• Ratio and average
Verification test requirements
Be sure that you perform the verification tests:
• Under the proper environmental conditions.
• After the specified warm-up period.
• Using the correct line voltage.
• After restoring factory defaults.
• With the INPUTS switch in the REAR (in) position.
Also, make sure to use the proper calibration equipment
procedures.
Environmental conditions
Conduct your performance verification procedures in a test environment that has:
• An ambient temperature of 18° to 28°C (65° to 82°F).
• A relative humidity of less than 80% unless otherwise noted.
Warm-up period
Allow the Model 27xx to warm up for at least two hours before conducting the verification procedures.
If the instrument has been subjected to temperature extremes (those outside the ranges stated above), allow additional time for
the instrument's internal temperature to stabilize. Typically, allow one extra hour to stabilize a unit that is 10°C (18°F) outside
the specified temperature range.
Also, allow the test equipment to warm up for the minimum time specified by the manufacturer.
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(Table 2) and the reading limits provided with the verification