34410A/11A/L4411A Service Guide 63
Calibration Procedures 3
Test Considerations
Errors may be induced by ac signals present on the input leads during a
self–test. 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 (T
cal
) is stable and
between 18 °C and 28 °C. Ideally the calibration should be performed
at 23 °C ±2 °C.
• Assure ambient relative humidity is less than 80%.
• Allow a 90 minute warm–up period with a copper short connected.
• Use shielded twisted pair PTFE–
insulated cables to reduce settling and
no
ise 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 highly 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 take care to ensure the calibrator’s “0” output
is correct. You will need to set the offset for each range of the measuring
function being verified.
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