Agilent Technologies U1251A, Руководство пользователя и сервисное руководство

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128 Agilent U1251A/U1252A User’s and Service Guide
7 Performance Tests and Calibration
Test Considerations
Long test leads can also act as an antenna causing pick- up
of AC signals.
For optimum performance, all procedures should comply
with the following recommendations:
• Assure that the calibration ambient temperature is stable
and between 18 °C and 28 °C. Ideally the calibration
should be performed at 23 °C ± 1 °C.
• Assure ambient relative humidity is less than 80%.
• Allow a 5 minutes warm- up period with a Shorting Plug
connected to the V and COM input terminals.
• Use shielded twisted pair Teflon- insulated cables to
reduce settling and noise errors. Keep the input cables as
short as possible.
• Connect the input cable shields to earth ground. Except
where noted in the procedures, connect the calibrator LO
source to earth ground at the calibrator. It is important
that the LO to earth ground connection be made at only
one place in the circuit to avoid ground loops.
Because the instrument is capable of making very accurate
measurements, you must take special care to ensure that the
calibration standards and test procedures used do not
introduce additional errors. Ideally, the standards used to
verify and adjust the instrument should be an order of
magnitude more accurate than each instrument range
full- scale error specification.
For the DC voltage, DC current, and resistance gain
verification measurements, you should ensure the calibrator's
"0" output is correct. You will need to set the offset for each
range of the measuring function being verified.