Test Considerations - Agilent Technologies U1251A User Manual

7 Performance Tests and Calibration

Test Considerations

128
Long test leads can also act as antennas which may pick up
AC signals.
For optimum performance, all procedures should comply
with the following recommendations:
• Ensure that the calibration ambient temperature is stable
and is between 18 °C and 28 °C. Ideally the calibration
should be performed at 23 °C ± 1 °C.
• Ensure that the ambient relative humidity is less than
80%.
• Allow a warm- up period of five minutes 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 of 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, ensure that the calibrator's "0"
output is correct. You will need to set the offset for each
range of the measuring function being verified.
Agilent U1251A/U1252A User's and Service Guide